[ { "id": "authors:04266-ee780", "collection": "authors", "collection_id": "04266-ee780", "cite_using_url": "https://authors.library.caltech.edu/records/04266-ee780", "type": "article", "title": "In-situ visualization of a growing brittle crack in aluminum oxynitride using synchrotron X-rays and the double-cleavage drilled compression geometry", "author": [ { "family_name": "Gorske", "given_name": "Sara F.", "orcid": "0000-0002-1329-9625", "clpid": "Gorske-Sara-F" }, { "family_name": "Park", "given_name": "Jun-Sang", "orcid": "0000-0002-3416-8130" }, { "family_name": "Kenesei", "given_name": "Peter" }, { "family_name": "Sharma", "given_name": "Hemant", "orcid": "0000-0002-0800-9275" }, { "family_name": "Almer", "given_name": "Jonathan", "orcid": "0000-0002-1900-2271" }, { "family_name": "Voorhees", "given_name": "Peter", "orcid": "0000-0003-2769-392X", "clpid": "Voorhees-Peter" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "

Brittle fracture is difficult to study in situ due to the speed of a growing crack and the often-catastrophic nature of failure in brittle materials. As a result, the influence of microstructural considerations, such as orientation, grain boundary locations, and strain field, on the crack path remains poorly understood. Presented in this study is a method addressing this knowledge gap, which utilizes the double-cleavage drilled compression geometry to achieve quasi-stable fracture in aluminum oxynitride (AlON). Synchrotron X-ray micro-computed tomography is used to characterize the crack shape and length, while high-energy diffraction microscopy provides information on the strains, orientations, and shapes of grains in the microstructure surrounding the crack tip. During testing, the crack grew in discrete and irregular jumps while the fracture toughness falls within reported ranges. The crack in AlON is found to have no greater tendency to crack intergranularly as compared to transgranularly, and grains which are cracked transgranularly do not display a trend in orientation or stress when compared to those around which the crack followed a grain boundary. The high resolution of the crack path and microstructural data provides a path forward for modeling and understanding 3D brittle fracture.

", "doi": "10.1016/j.actamat.2026.122213", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2026-06-15", "volume": "312", "pages": "122213" }, { "id": "authors:bv7tq-3cg22", "collection": "authors", "collection_id": "bv7tq-3cg22", "cite_using_url": "https://authors.library.caltech.edu/records/bv7tq-3cg22", "type": "article", "title": "Discovery and characterization of a silicon aluminum scandate (SAS) material", "author": [ { "family_name": "Yu", "given_name": "Kevin", "orcid": "0000-0003-3130-4309", "clpid": "Yu-Kevin" }, { "family_name": "Stokes", "given_name": "Jamesa", "orcid": "0000-0002-0675-9988", "clpid": "Stokes-Jamesa" }, { "family_name": "Jha", "given_name": "Kunal K.", "orcid": "0000-0001-9551-8256", "clpid": "Jha-Kunal-K" }, { "family_name": "Harder", "given_name": "Bryan", "orcid": "0000-0002-5304-5267", "clpid": "Harder-Bryan" }, { "family_name": "Nelson", "given_name": "Hosea M.", "orcid": "0000-0002-4666-2793", "clpid": "Nelson-H-M" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "

A newly discovered doped silicon aluminum scandate (SAS) phase was successfully isolated and synthesized. Microcrystal electron diffraction was employed to determine the doped SAS crystal structure, revealing a triclinic (P 1 ¯ ) unit cell with the nominal formula Si\u2082Al\u2082Sc\u2081\u2084O\u2082\u2088 with minority dopants of CaO, MgO, Fe\u2082O\u2083, and TiO\u2082. Powder X-ray diffraction and Rietveld refinement confirmed the structure of the doped SAS material. Electron-probe microanalysis and solid-state nuclear magnetic resonance were used to better understand the composition and local structure of the doped SAS phase. The results indicated that there are extensive cation substitutions within the doped SAS material. Differential thermal analysis on doped SAS demonstrated that the material is thermally stable up to 2150°C, suggesting potential for refractory applications. Additional characterization, enabled by the solved structure of doped SAS, focused on relevant properties for refractory materials. The thermal expansion behavior of the doped SAS material was evaluated using high-temperature, in situ X-ray diffraction, while the reaction pathway for SAS formation was determined using a combination of high-temperature X-ray diffraction and annealing experiments. Ultimately, this study defines the structure, composition, and thermal behavior of the doped SAS material, while also highlighting the utility of microcrystal electron diffraction for structure determination of complex oxide phases.

", "doi": "10.1016/j.actamat.2026.121949", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2026-04-01", "volume": "307", "pages": "121949" }, { "id": "authors:n61bx-tbb53", "collection": "authors", "collection_id": "n61bx-tbb53", "cite_using_url": "https://authors.library.caltech.edu/records/n61bx-tbb53", "type": "article", "title": "Improving molten regolith electrolysis with zirconia-based hollow anode technology", "author": [ { "family_name": "Yu", "given_name": "Kevin", "orcid": "0000-0003-3130-4309", "clpid": "Yu-Kevin" }, { "family_name": "West", "given_name": "William", "clpid": "West-William" }, { "family_name": "Stokes", "given_name": "Jamesa", "orcid": "0000-0002-0675-9988" }, { "family_name": "Harder", "given_name": "Bryan", "orcid": "0000-0002-5304-5267" }, { "family_name": "Reidy", "given_name": "Lorlyn" }, { "family_name": "Dominguez", "given_name": "Jesus" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "

Molten regolith electrolysis is a promising in-situ resource utilization technology that targets O2 and metals production through the direct electrolysis of molten lunar regolith. However, there are still challenges associated with molten regolith electrolysis, such as bubble detachment and O2 separation and collection at the anode. A hollow anode, comprised of an oxygen-conducting yttria-stabilized zirconia shell and a platinum current collector, is designed here to address these challenges. Experimental results from an inverted hollow anode reactor successfully demonstrate that molten regolith electrolysis can be performed through a solid electrolyte. The elemental composition of both the cathodic products (primarily Fe and Si) and solidified lunar regolith simulant are reported as a function of electrolysis duration. These observations are supported by a thermochemical model built using FactSage to provide compositions of the cathodic products and solidified regolith simulant with increasing O2 removal. Finally, the behavior of yttria-stabilized zirconia in the hollow anode application is characterized, and provides guidance for the design and operation of a yttria-stabilized zirconia hollow anode to enable integration into a full-scale molten regolith electrolysis reactor.

", "doi": "10.1016/j.actaastro.2025.06.028", "issn": "0094-5765", "publisher": "Elsevier", "publication": "Acta Astronautica", "publication_date": "2025-10", "volume": "235", "pages": "723-735" }, { "id": "authors:0pyc2-zsz80", "collection": "authors", "collection_id": "0pyc2-zsz80", "cite_using_url": "https://authors.library.caltech.edu/records/0pyc2-zsz80", "type": "article", "title": "Clear as mud redefined: Tunable transparent mineral scaffolds for visualizing microbial processes below ground", "author": [ { "family_name": "Quinn", "given_name": "Laura", "orcid": "0000-0002-6112-028X", "clpid": "Quinn-Laura" }, { "family_name": "Sharma", "given_name": "Kriti", "clpid": "Sharma-Kriti" }, { "family_name": "Faber", "given_name": "Katherine T", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Orphan", "given_name": "Victoria J", "orcid": "0000-0002-5374-6178", "clpid": "Orphan-V-J" } ], "abstract": "

Microbes inhabiting complex porous microenvironments in sediments and aquifers catalyze reactions that are critical to global biogeochemical cycles and ecosystem health. However, the opacity and complexity of porous sediment and rock matrices have considerably hindered the study of microbial processes occurring within these habitats. Here we generated microbially-compatible, optically transparent mineral scaffolds to visualize and investigate microbial colonization and activities occurring in these environments, in laboratory settings and in situ. Using inexpensive synthetic cryolite mineral, we produced optically transparent scaffolds mimicking the complex three-dimensional structure of sediments and rocks, by adapting a suspension-based freeze-casting technique commonly used in materials science. Fine-tuning of parameters such as freezing rate and choice of solvent provided full control of pore size and architecture. The combined effects of scaffold porosity and structure on the movement of microbe-sized particles, tested using velocity-tracking of fluorescent beads, showed diverse yet reproducible behaviors. The scaffolds we produced are compatible with epifluorescence microscopy, allowing the fluorescence-based identification of colonizing microbes by DNA-based staining and fluorescence in situ hybridization to depths of 100 µm. Additionally, Raman spectroscopy analysis indicates minimal background signal in regions used for measuring deuterium and ¹³C enrichment in microorganisms, highlighting the potential to directly couple D\u2082O or ¹³C stable isotope probing and Raman-FISH for quantifying microbial activity at the single-cell level. To demonstrate the relevance of cryolite scaffolds for environmental field studies, we visualized their colonization by diverse microorganisms within rhizosphere sediments of a coastal seagrass plant, using epifluorescence microscopy. The new tool presented here enables highly resolved, spatially explicit, and multi-modal investigations into the distribution, activities, and interactions of underground microbes typically obscured within opaque geological materials until now.

", "doi": "10.1093/pnasnexus/pgaf118", "issn": "2752-6542", "publisher": "National Academy of Sciences", "publication": "PNAS Nexus", "publication_date": "2025-04-16", "series_number": "5", "volume": "4", "issue": "5", "pages": "pgaf118" }, { "id": "authors:q2fv3-sen12", "collection": "authors", "collection_id": "q2fv3-sen12", "cite_using_url": "https://authors.library.caltech.edu/records/q2fv3-sen12", "type": "article", "title": "Shape memory and superelasticity in polycrystalline ceria-stabilized zirconia honeycombs", "author": [ { "family_name": "Quinn", "given_name": "Laura K.", "orcid": "0000-0002-6112-028X", "clpid": "Quinn-Laura-K" }, { "family_name": "Esteves", "given_name": "Remelisa", "orcid": "0000-0001-7941-6356", "clpid": "Esteves-Remelisa" }, { "family_name": "Latorre-Su\u00e1rez", "given_name": "Perla", "orcid": "0000-0003-0259-2604", "clpid": "Latorre-Su\u00e1rez-Perla" }, { "family_name": "Rossman", "given_name": "George R.", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "Raghavan", "given_name": "Seetha", "orcid": "0000-0001-5389-9417", "clpid": "Raghavan-Seetha" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "
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Shape-memory and superelastic materials undergo a reversible martensitic transformation that allows them to return to their original state after deformation, either on the application of heat or the removal of stress. While zirconia-based ceramics can undergo this martensitic transformation, the volume expansion that accompanies the transformation can cause mismatched stresses at grain boundaries in polycrystalline systems, leading to cracking and premature failure. To increase the surface area to volume ratio, and thus circumvent this premature failure, this work uses directional freeze casting to incorporate columnar pores into ceria-stabilized zirconia ceramics, thereby producing honeycomb-like structures. These ceramics can be subjected to stresses up to 45 MPa and, depending on the ceria content, exhibit either shape-memory or superelastic behavior under uniaxial compression. The studies highlight the use of X-ray diffraction and Raman spectroscopy to track the extent of the martensitic transformations over different collection volumes and explore that behavior over multiple cycles. Furthermore, in-situ Raman spectroscopy coupled with conventional uniaxial compression and diamond anvil cell loading confirm, for the first time, superelastic behavior in bulk-scale, polycrystalline, porous zirconia ceramics.

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", "doi": "10.1016/j.actamat.2024.120340", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2024-12-01", "volume": "281", "pages": "120340" }, { "id": "authors:7xxbg-fbw63", "collection": "authors", "collection_id": "7xxbg-fbw63", "cite_using_url": "https://authors.library.caltech.edu/records/7xxbg-fbw63", "type": "article", "title": "Thermochemical interactions between yttria\u2010stabilized zirconia and molten lunar regolith simulants", "author": [ { "family_name": "Yu", "given_name": "Kevin", "orcid": "0000-0003-3130-4309" }, { "family_name": "Stokes", "given_name": "Jamesa", "orcid": "0000-0002-0675-9988" }, { "family_name": "Harder", "given_name": "Bryan", "orcid": "0000-0002-5304-5267" }, { "family_name": "Reidy", "given_name": "Lorlyn" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "
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Oxygen produced through in-situ resource utilization (ISRU) is critical to maintaining a permanent human presence on the lunar surface. Molten regolith electrolysis and carbothermal reduction are two promising ISRU techniques for generating oxygen directly from lunar regolith, which is primarily a mixture of oxide minerals; however, both processes require operating temperatures of 1600°C to melt lunar regolith and dissociate the molten oxides. These conditions limit the use of many oxide refractory materials, such as Al2O3 and MgO, due to rapid degradation resulting from reactions between the refractory materials and molten lunar regolith. Yttria-stabilized zirconia (YSZ) is shown here to be a promising refractory oxide to provide containment of molten regolith while demonstrating limited reactivity. This work focuses on corrosion studies of YSZ powders and dense YSZ crucibles in contact with molten lunar maria and highlands regolith simulants at 1600°C. The interactions between YSZ and molten regolith were characterized using scanning electron microscopy/energy dispersive spectroscopy, X-ray diffraction, and electron backscatter diffraction. A FactSage thermochemical model was created for comparison with the experimental results. These combined analyses suggest that lunar maria regolith will degrade the YSZ faster than the lunar highlands regolith due to the lower viscosity of the maria regolith. The feasibility of long-term molten regolith containment with YSZ is discussed based on the YSZ powder and crucible results.

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", "doi": "10.1111/jace.19821", "issn": "0002-7820", "publisher": "American Ceramic Society", "publication": "Journal of the American Ceramic Society", "publication_date": "2024-04-13" }, { "id": "authors:ym7kj-vsj33", "collection": "authors", "collection_id": "ym7kj-vsj33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230705-530447400.1", "type": "article", "title": "Chemical Transformations of 2D Kaolinic Clay Mineral Surfaces from Sulfuric Acid Exposure", "author": [ { "family_name": "Chari", "given_name": "C. S.", "orcid": "0000-0001-6404-4203", "clpid": "Chari-Celia-S" }, { "family_name": "Heimann", "given_name": "J. E.", "orcid": "0000-0002-1050-4582", "clpid": "Heimann-Jessica-E" }, { "family_name": "Rosenzweig", "given_name": "Z.", "orcid": "0000-0001-6098-3932", "clpid": "Rosenzweig-Zeev" }, { "family_name": "Bennett", "given_name": "J. W.", "orcid": "0000-0002-7971-4772", "clpid": "Bennett-Joseph" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A combined experimental and computational approach is used to investigate the chemical transformations of kaolinite and metakaolin surfaces when exposed to sulfuric acid. These clay minerals are hydrated ternary metal oxides and are shown to be susceptible to degradation by loss of Al as the water-soluble salt Al\u2082(SO\u2084)\u2083, due to interactions between H\u2082SO\u2084 and aluminum cations. This degradation process results in a silica-rich interfacial layer on the surfaces of the aluminosilicates, most prominently observed in metakaolin exposed to pH environments of less than 4. Our observations are supported by XPS, ATR-FTIR, and XRD experiments. Concurrently, DFT methodologies are used to probe the interactions between the clay mineral surfaces and H\u2082SO\u2084 as well as other sulfur-containing adsorbates. An analysis performed using a DFT + thermodynamics model shows that the surface transformation processes that lead to the loss of Al and SO\u2084 from metakaolin are favorable at pH below 4; however, such transformations are not favorable for kaolinite, a result that agrees with our experimental efforts. The data obtained from both experimental techniques and computational studies support that the dehydrated surface of metakaolin interacts more strongly with sulfuric acid and provide atomistic insight into the acid-induced transformations of these mineral surfaces.", "doi": "10.1021/acs.langmuir.3c00113", "issn": "0743-7463", "publisher": "American Chemical Society", "publication": "Langmuir", "publication_date": "2023-05-23", "series_number": "20", "volume": "39", "issue": "20", "pages": "6964-6974" }, { "id": "authors:5567n-k5940", "collection": "authors", "collection_id": "5567n-k5940", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20230725-500424000.4", "type": "article", "title": "Gradient-controlled freeze casting of preceramic polymers", "author": [ { "family_name": "Arai", "given_name": "Noriaki", "orcid": "0000-0002-3040-2997", "clpid": "Arai-Noriaki" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Solidification is the foundation upon which freeze casting is built, and this work seeks to understand the solidification process in freeze casting, especially with respect to the growth of dendrites. To this end, two solidification parameters, freezing front velocity and temperature gradient, were independently controlled using a gradient-controlled freeze casting setup to investigate the effects of each parameter. Changes in dendritic pore size and morphology with solidification parameters were investigated by scanning electron microscopy and mercury intrusion porosimetry. The results agree with dendrite growth theory. The theory of constitutional supercooling is used to describe the morphological changes of dendritic pores to cellular pores by the control of freezing front velocity, temperature gradient, and preceramic polymer concentrations.", "doi": "10.1016/j.jeurceramsoc.2022.12.016", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2023-05", "series_number": "5", "volume": "43", "issue": "5", "pages": "1904-1911" }, { "id": "authors:b179s-ckg07", "collection": "authors", "collection_id": "b179s-ckg07", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220222-706520000", "type": "article", "title": "Oxidation resistance of AlN/BN via mullite-type Al\u2081\u2088B\u2084O\u2083\u2083", "author": [ { "family_name": "Chari", "given_name": "C. S.", "orcid": "0000-0001-6404-4203", "clpid": "Chari-Celia-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "AlN/BN ceramic composites are materials of interest for high-temperature applications because of their low elastic modulus and high thermal shock resistance. Concerns of side products that could form, due to the oxidation of BN into reactive B\u2082O\u2083, motivate the study of the influence of B\u2082O\u2083 on the oxidation of AlN and AlN/BN. This investigation explores such an effect by comparing the oxidation kinetics of AlN with that of B\u2082O\u2083-coated AlN, offering insight into how liquid B\u2082O\u2083 films provide AlN with improved protection against oxidation at temperatures from 1200 to 1300 \u00b0C. These concepts are extended to AlN/BN in oxidative environments. We discuss the formation of Al\u2081\u2088B\u2081\u2088O\u2083\u2083 whiskers from B\u2082O\u2083 and Al\u2082O\u2083 and analyze how the microstructure evolves into hollow crystals with prolonged exposure to high-temperatures. Ultimately, this study provides a novel perspective on the oxidation of AlN/BN and serves as a guide to understanding the morphological evolution of Al\u2081\u2088B\u2081\u2088O\u2083\u2083.", "doi": "10.1016/j.jeurceramsoc.2022.02.037", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2022-07", "series_number": "8", "volume": "42", "issue": "8", "pages": "3437-3445" }, { "id": "authors:p2vnr-qna08", "collection": "authors", "collection_id": "p2vnr-qna08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220121-733841000", "type": "article", "title": "Deposition of electrically conductive zirconium monoxide via plasma spray-physical vapor deposition", "author": [ { "family_name": "Harder", "given_name": "Bryan J.", "orcid": "0000-0002-5304-5267", "clpid": "Harder-Bryan-J" }, { "family_name": "Good", "given_name": "Brian", "clpid": "Good-Brian" }, { "family_name": "Schmitt", "given_name": "Michael", "orcid": "0000-0003-0922-3975", "clpid": "Schmitt-Michael" }, { "family_name": "Kowalski", "given_name": "Ben", "orcid": "0000-0001-9324-1628", "clpid": "Kowalski-Benjamin" }, { "family_name": "Koszegi", "given_name": "Giacomo", "clpid": "Koszegi-Giacomo" }, { "family_name": "Johnson", "given_name": "Matthew T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-Matthew-T" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A condensed phase of zirconium monoxide (ZrO) was detected in YSZ (Zr_(0.92)Y_(0.08)O_(2-\u03b4)) coatings deposited using plasma spray-physical vapor deposition. The rapid cooling rate of this process can result in the condensation of nonequilibrium states that can be kinetically trapped in the coatings. The columnar microstructure contained a mixture of YSZ, ZrO2, and ZrO phases. The ZrO phase was expected to be conductive based on density functional theory calculations, and preliminary impedance measurements were performed that supported this prediction. When heated in an oxygen-containing environment, the ZrO phase remains in the coating until \u223c450 K, at which point it disappears quickly, as confirmed by X-ray diffraction and thermogravimetric methods. The loss of ZrO in the coating was also linked to a loss in electrical conductivity. However, it was shown that this phase can persist at elevated temperatures of \u223c1000 K in vacuum or inert environments for at least 100 h.", "doi": "10.1111/jace.18309", "issn": "0002-7820", "publisher": "Wiley", "publication": "Journal of the American Ceramic Society", "publication_date": "2022-05", "series_number": "5", "volume": "105", "issue": "5", "pages": "3568-3580" }, { "id": "authors:vbaz4-t4a36", "collection": "authors", "collection_id": "vbaz4-t4a36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20220425-535273500", "type": "article", "title": "Nanoscale engineering of gold particles in 18th century B\u00f6ttger lusters and glazes", "author": [ { "family_name": "Chari", "given_name": "Celia S.", "orcid": "0000-0001-6404-4203", "clpid": "Chari-Celia-S" }, { "family_name": "Taylor", "given_name": "Zane W.", "orcid": "0000-0002-9326-6873", "clpid": "Taylor-Zane-W" }, { "family_name": "Bezur", "given_name": "Anik\u00f3", "orcid": "0000-0001-6628-7049", "clpid": "Bezur-Anik\u00f3" }, { "family_name": "Xie", "given_name": "Sujing", "clpid": "Xie-Sujing" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "By exploring the manufacturing methods of historic objects, cultural heritage studies can yield new insights into the history of technology. The required tunability of processing steps, however, is often unknown and the underlying physics and chemistry that provide insight into the object's properties may also be lacking. A case in point is B\u00f6ttger luster, a purple overglaze decoration famous for its distinctive iridescence, produced in the Meissen Manufactory from its earliest B\u00f6ttger period (1710\u20131719) to around 1735. The iridescence of B\u00f6ttger luster distinguishes it from contemporaneous purple glazes, motivating the exploration of what compositional and structural features give rise to this optical phenomenon. In this study, historic samples of B\u00f6ttger luster and Purple of Cassius from Meissen are characterized and compared microscopically. The composition of both overglaze enamels is presented, including results from scanning transmission electron microscopy (STEM)-energy-dispersive X-ray spectroscopy (EDX) analyses. It was found that the iridescence and purple color of B\u00f6ttger luster is due to the presence of gold nanoparticles in the glaze of the porcelain. Of specific interest is how the underlying physics of scattering and interference of the nanoparticle array is responsible for the iridescence that distinguishes B\u00f6ttger luster from other gold-based purple colorants, including Purple of Cassius. Coupling these results with prior findings of Meissen porcelains, the glazes were recreated and characterized using scanning electron microscopy (SEM)-EDX, X-ray diffraction (XRD), and ultraviolet-visible spectroscopy (UV-Vis), offering insights into compositional requirements to produce purple luster.", "doi": "10.1073/pnas.2120753119", "pmcid": "PMC9170166", "issn": "0027-8424", "publisher": "National Academy of Sciences", "publication": "Proceedings of the National Academy of Sciences of the United States of America", "publication_date": "2022-04-21", "series_number": "18", "volume": "119", "issue": "18", "pages": "e2120753119" }, { "id": "authors:dtanz-r1078", "collection": "authors", "collection_id": "dtanz-r1078", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210504-120148263", "type": "article", "title": "Freeze-cast honeycomb structures via gravity-enhanced convection", "author": [ { "family_name": "Arai", "given_name": "Noriaki", "orcid": "0000-0002-3040-2997", "clpid": "Arai-Noriaki" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The effect of gravity on directional solidification was investigated in solution-based freeze casting. A preceramic siloxane-based polymer was freeze-cast with a cyclohexene solvent from two different directions: that against the direction of the gravitational force and that in concert with the gravitational force. Because the density of preceramic polymer is higher than the solvent, the segregated polymer creates a denser solution ahead of the freezing front than the underlying solution when the freezing direction is the same as the gravity direction. This results in convective flow in the liquid phase. This convective flow influences constitutional supercooling, which changes not only the pore size of freeze-cast structure but also the pore morphology from dendritic to cellular pores.", "doi": "10.1111/jace.17871", "issn": "0002-7820", "publisher": "Wiley", "publication": "Journal of the American Ceramic Society", "publication_date": "2021-09", "series_number": "9", "volume": "104", "issue": "9", "pages": "4309-4315" }, { "id": "authors:nz65p-gqy77", "collection": "authors", "collection_id": "nz65p-gqy77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210604-111533773", "type": "article", "title": "Coarsening of dendrites in solution-based freeze-cast ceramic systems", "author": [ { "family_name": "Arai", "given_name": "Noriaki", "orcid": "0000-0002-3040-2997", "clpid": "Arai-Noriaki" }, { "family_name": "Stan", "given_name": "Tiberiu", "clpid": "Stan-Tiberiu" }, { "family_name": "Macfarland", "given_name": "Sophie", "orcid": "0000-0001-8488-7363", "clpid": "Macfarland-Sophie" }, { "family_name": "Voorhees", "given_name": "Peter W.", "orcid": "0000-0003-2769-392X", "clpid": "Voorhees-Peter-W" }, { "family_name": "Muyanja", "given_name": "Nancy S.", "orcid": "0000-0002-3394-5452", "clpid": "Muyanja-Nancy-S" }, { "family_name": "Shahani", "given_name": "Ashwin J.", "orcid": "0000-0002-6157-840X", "clpid": "Shahani-Ashwin-J" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The morphologies of freeze-cast materials are typically controlled and tuned by adjusting the freezing front velocity and temperature gradient. Recently it has been demonstrated that coarsening, similar to that commonly practiced in alloy systems, is also effective for morphological control in freeze-cast materials. However, the underlying coarsening mechanisms and their effect on microstructure evolution are largely unknown. In this study, frozen preceramic polymer/cyclohexane solutions were coarsened at 2 \u00b0C and 4 \u00b0C for up to 5 h, and the resulting morphologies were characterized using scanning electron microscopy, mercury intrusion porosimetry, and X-ray computed tomography. During coarsening the microstructure evolved from dendritic (primary and secondary pores) to honeycomb-like (large open channels with flat walls). The size of both primary and secondary pores increased linearly with the cube root of coarsening time, consistent with dendritic coarsening in alloy systems. Other important metrics such as primary dendrite spacing, dendrite growth directionality, and the effect of coarsening on the pore-ceramic interface area are reported. These findings provide novel insights into coarsening of freeze-cast systems and can lead to new avenues for microstructure tailorability.", "doi": "10.1016/j.actamat.2021.117039", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2021-08-15", "volume": "215", "pages": "Art. No. 117039" }, { "id": "authors:g7br0-2cd89", "collection": "authors", "collection_id": "g7br0-2cd89", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210511-122025958", "type": "article", "title": "Looking Back, Looking Forward: Materials Science in Art, Archaeology, and Art Conservation", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Casadio", "given_name": "Francesca", "orcid": "0000-0003-4043-9010", "clpid": "Casadio-Francesca" }, { "family_name": "Masic", "given_name": "Admir", "clpid": "Masic-Admir" }, { "family_name": "Robbiola", "given_name": "Luc", "orcid": "0000-0002-1614-9921", "clpid": "Robbiola-Luc" }, { "family_name": "Walton", "given_name": "Marc", "orcid": "0000-0002-4436-3546", "clpid": "Walton-Marc" } ], "abstract": "Cultural heritage materials, ranging from archaeological objects and sites to fine arts collections, are often characterized through their life cycle. In this review, the fundamentals and tools of materials science are used to explore such life cycles\u2014first, via the origins of the materials and methods used to produce objects of function and artistry, and in some cases, examples of exceptional durability. The findings provide a window on our cultural heritage. Further, they inspire the design of sustainable materials for future generations. Also explored in this review are alteration phenomena over intervals as long as millennia or as brief as decades. Understanding the chemical processes that give rise to corrosion, passivation, or other degradation in chemical and physical properties can provide the foundation for conservation treatments. Finally, examples of characterization techniques that have been invented or enhanced to afford studies of cultural heritage materials, often nondestructively, are highlighted.", "doi": "10.1146/annurev-matsci-080819-013103", "issn": "1531-7331", "publisher": "Annual Reviews", "publication": "Annual Review of Materials Research", "publication_date": "2021-07", "volume": "51", "pages": "435-460" }, { "id": "authors:jvzm3-47c46", "collection": "authors", "collection_id": "jvzm3-47c46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210114-143037831", "type": "article", "title": "Fracture Diodes: Directional Asymmetry of Fracture Toughness", "author": [ { "family_name": "Brodnik", "given_name": "N. R.", "clpid": "Brodnik-Neal-R" }, { "family_name": "Brach", "given_name": "S.", "orcid": "0000-0003-4766-8131", "clpid": "Brach-Stella" }, { "family_name": "Long", "given_name": "C.\u2009M.", "clpid": "Long-C-M" }, { "family_name": "Ravichandran", "given_name": "G.", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Bourdin", "given_name": "B.", "orcid": "0000-0002-1312-9175", "clpid": "Bourdin-Blaise" }, { "family_name": "Faber", "given_name": "K.\u2009T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Bhattacharya", "given_name": "K.", "orcid": "0000-0003-2908-5469", "clpid": "Bhattacharya-K" } ], "abstract": "Toughness describes the ability of a material to resist fracture or crack propagation. It is demonstrated here that fracture toughness of a material can be asymmetric, i.e., the resistance of a medium to a crack propagating from right to left can be significantly different from that to a crack propagating from left to right. Such asymmetry is unknown in natural materials, but we show that it can be built into artificial materials through the proper control of microstructure. This paves the way for control of crack paths and direction, where fracture\u2014when unavoidable\u2014can be guided through predesigned paths to minimize loss of critical components.", "doi": "10.1103/physrevlett.126.025503", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "2021-01-15", "series_number": "2", "volume": "126", "issue": "2", "pages": "Art. No. 025503" }, { "id": "authors:k15jc-vab75", "collection": "authors", "collection_id": "k15jc-vab75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20201019-100031049", "type": "article", "title": "Hierarchical porous SiOC via freeze casting and self-assembly of block copolymers", "author": [ { "family_name": "Kuo", "given_name": "Taijung", "orcid": "0000-0002-3720-968X", "clpid": "Kuo-Taijung" }, { "family_name": "Rueschhoff", "given_name": "Lisa M.", "orcid": "0000-0001-6503-5704", "clpid": "Rueschhoff-L-M" }, { "family_name": "Dickerson", "given_name": "Matthew B.", "clpid": "Dickerson-M-B" }, { "family_name": "Patel", "given_name": "Tulsi A.", "orcid": "0000-0002-6156-2248", "clpid": "Patel-T-A" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Surface area, permeability, and mechanical robustness are particularly crucial for porous ceramics utilized in filter and catalyst support applications. Unfortunately, these desirable properties are often inversely related to one another via porosity and pore size, creating a serious challenge in the optimization of these materials. To address this challenge, we propose a hierarchical porous composite, fabricated by freeze casting preceramic polymers and re-infiltrating with a self-assembling preceramic polymer/block copolymer blend. The resulting pyrolyzed SiOC hierarchical solid displayed a bimodal pore size distribution with macropores from the freeze-cast structure and mesopores in the self-assembled coating. Neither permeability, compressive strength, nor Young's modulus of the porous composite were compromised with the mesoporous conformal coatings. With the presented hierarchical structure, a better filtration material is expected with higher throughput and reaction rates. Furthermore, by adopting a two-step process, macropores and mesopores can be individually tuned to optimize structures for desired applications.", "doi": "10.1016/j.scriptamat.2020.09.042", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2021-01-15", "volume": "191", "pages": "204-209" }, { "id": "authors:9v86c-rs752", "collection": "authors", "collection_id": "9v86c-rs752", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200122-074829153", "type": "article", "title": "Permeable carbon nanotube-reinforced silicon oxycarbide via freeze casting with enhanced mechanical stability", "author": [ { "family_name": "Kuo", "given_name": "C. T.", "orcid": "0000-0002-3720-968X", "clpid": "Kuo-Claire-Tai-Jung" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Reinforcement strategies were applied to solution-based freeze-casting systems to form porous ceramic composites. Multi-walled carbon nanotubes (MWCNT) were used as the reinforcing fillers in a polysiloxane preceramic polymer freeze cast with dimethyl carbonate to produce silicon oxycarbide-based lamellar pore structures. Using a carefully designed dispersion procedure, CNT agglomerates were reduced both in suspension and in pore walls. Electrical conductivity increased by ten orders of magnitude over pure silicon oxycarbide, indicating the preservation of CNTs after pyrolysis. Permeability, compression, and diametral compression (Brazilian disk) tests were performed to demonstrate the reinforcing effect of CNTs without sacrificing the permeability of the final porous structures.", "doi": "10.1016/j.jeurceramsoc.2019.12.059", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2020-06", "series_number": "6", "volume": "40", "issue": "6", "pages": "2470-2479" }, { "id": "authors:6zsvy-3g175", "collection": "authors", "collection_id": "6zsvy-3g175", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210201-150525983", "type": "patent", "title": "Freeze-cast ceramic membrane for size based filtration", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Kornfield", "given_name": "Julia A.", "orcid": "0000-0001-6746-8634", "clpid": "Kornfield-J-A" }, { "family_name": "Arai", "given_name": "Noriaki", "orcid": "0000-0002-3040-2997", "clpid": "Arai-Noriaki" }, { "family_name": "Bateman", "given_name": "Orland", "clpid": "Bateman-Orland" }, { "family_name": "Ismagilov", "given_name": "Rustem F.", "orcid": "0000-0002-3680-4399", "clpid": "Ismagilov-R-F" } ], "abstract": "Provided herein are methods for making a freeze-cast material having a internal structure, the methods comprising steps of: determining the internal structure of the material, the internal structure having a plurality of pores, wherein: each of the plurality of pores has directionality; and the step of determining comprises: selecting a temperature gradient and a freezing front velocity to obtain the determined internal structure based on the selected temperature gradient and the selected freezing front velocity; directionally freezing a liquid formulation to form a frozen solid, the step of directionally freezing comprising: controlling the temperature gradient and the freezing front velocity to match the selected temperature gradient and the selected freezing front velocity during directionally freezing; wherein the liquid formulation comprises at least one solvent and at least one dispersed species; and subliming the at least one solvent out of the frozen solid to form the material.", "publisher": "U.S. Patent Office", "publication_date": "2020-04-16" }, { "id": "authors:tgzn4-6ba54", "collection": "authors", "collection_id": "tgzn4-6ba54", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200207-102105047", "type": "article", "title": "Effects of zinc oxide filler on the curing and mechanical response of alkyd coatings", "author": [ { "family_name": "Sturdy", "given_name": "Lauren F.", "clpid": "Sturdy-L-F" }, { "family_name": "Wright", "given_name": "Madeleine S.", "clpid": "Wright-M-S" }, { "family_name": "Yee", "given_name": "Alexander", "clpid": "Yee-Alexander" }, { "family_name": "Casadio", "given_name": "Francesca", "clpid": "Casadio-F" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Shull", "given_name": "Kenneth R.", "clpid": "Shull-K-R" } ], "abstract": "The mechanical properties of an alkyd resin filled with zinc oxide pigment were studied at different concentrations over a wide range of time scales using dynamic mechanical analysis, quartz crystal rheometry and nanoindentation. The motivation for this work stems from the interest in accessing the long-term properties of paint coatings by studying the mechanical properties of historic paints. In this foundational work, we compare three different modalities of mechanical measurements and systematically determine the effect of pigment filler loading on the measured properties. Quantitative agreement between the methods is obtained when the characteristic time scales of each of the methods is taken into account. While nanoindentation is the technique most readily applied to historic paint samples, the rheometric quartz crystal microbalance (rheo-QCM) is the best suited for obtaining mechanistic information from measurements of paint properties over time, provided that appropriate thin-film samples can be produced. In these studies we find that ZnO increases the rate of oxidation of the alkyd during the initial stages of cure by an amount that depends on the ZnO content.", "doi": "10.1016/j.polymer.2020.122222", "issn": "0032-3861", "publisher": "Elsevier", "publication": "Polymer", "publication_date": "2020-03-16", "volume": "191", "pages": "Art. No. 122222" }, { "id": "authors:efmzk-d2m21", "collection": "authors", "collection_id": "efmzk-d2m21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20200430-104816477", "type": "article", "title": "Guiding and Trapping Cracks With Compliant Inclusions for Enhancing Toughness of Brittle Composite Materials", "author": [ { "family_name": "Brodnik", "given_name": "Neal R.", "clpid": "Brodnik-N-R" }, { "family_name": "Hsueh", "given_name": "Chun-Jen", "clpid": "Hsueh-Chun-Jen" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Bourdin", "given_name": "Blaise", "clpid": "Bourdin-B" }, { "family_name": "Ravichandran", "given_name": "Guruswami", "orcid": "0000-0002-2912-0001", "clpid": "Ravichandran-G" }, { "family_name": "Bhattacharya", "given_name": "Kaushik", "orcid": "0000-0003-2908-5469", "clpid": "Bhattacharya-K" } ], "abstract": "The problem of toughening heterogeneous materials with a stiff matrix and compliant inclusions is investigated through numerical simulations and experiments. Specifically, the problem of optimizing a combination of effective toughness and effective elastic modulus in the context of a square array of compliant inclusions in a stiff matrix is explored. Crack propagation in the heterogeneous material is simulated using a variational phase-field approach. It is found that the crack can meander between or get attracted to and trapped in the inclusions. Composite specimens with a stiff matrix and compliant circular inclusions were 3D printed, and their fracture toughness was measured using a specially designed loading fixture. The experimental results show agreement with the numerical predictions by demonstrating the attraction and trapping of cracks in the inclusions. This study demonstrates the potential for significant enhancement of toughness through elastic compliance contrast between the matrix and the inclusion without notably compromising the effective elastic modulus of the composite material.", "doi": "10.1115/1.4045682", "issn": "0021-8936", "publisher": "American Society of Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "2020-03", "series_number": "3", "volume": "87", "issue": "3", "pages": "Art. No. 031018" }, { "id": "authors:dxgks-zp162", "collection": "authors", "collection_id": "dxgks-zp162", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191224-093208324", "type": "article", "title": "Dense garnet-type electrolyte with coarse grains for improved air stability and ionic conductivity", "author": [ { "family_name": "Zeng", "given_name": "Xiaomei", "clpid": "Zeng-Xiaomei" }, { "family_name": "Martinolich", "given_name": "Andrew J.", "orcid": "0000-0002-7866-9594", "clpid": "Martinolich-A-J" }, { "family_name": "See", "given_name": "Kimberly A.", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly-A" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Garnet-type electrolytes with high ionic conductivity and chemical stability against lithium metal show promise as solid-state electrolytes for lithium-ion batteries. However, a high concentration of pores and grain boundaries in air-processed polycrystalline electrolytes makes them prone to dendrite formation and reaction with atmospheric moisture, leading to electrochemical and mechanical instability. In this work, we illustrate that abnormal grain growth, an often-avoided phenomenon in conventional ceramic processing, can be employed as a unique approach to obtain extraordinarily large oligo crystals for minimal grain boundaries. Here we report a straightforward approach to develop a robust Ga-doped garnet, Li_(6.25)Ga_(0.25)La_3Zr_2O_(12) (LGLZO) electrolyte with conventional solid-state sintering in air. By preparing nanopowders without agglomeration through ball milling and freeze drying, we can control the microstructure of air-sintered electrolytes for desirable properties of a high density (98% of theoretical density) and an average grain size of 460 \u00b5m. The robust air-processed LGLZO electrolytes demonstrate high ionic conductivity, stability in air, and mechanical robustness relative to other garnet electrolytes offering promise as cost- and performance-competitive solid-state electrolytes for safe lithium-ion batteries.", "doi": "10.1016/j.est.2019.101128", "issn": "2352-152X", "publisher": "Elsevier BV", "publication": "Journal of Energy Storage", "publication_date": "2020-02", "volume": "27", "pages": "Art. No. 101128" }, { "id": "authors:958he-ptr86", "collection": "authors", "collection_id": "958he-ptr86", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20191120-091827034", "type": "article", "title": "Analysis of Multi-scale Mechanical Properties of Ceramic Trusses Prepared from Preceramic Polymers", "author": [ { "family_name": "Brodnik", "given_name": "N. R.", "clpid": "Brodnik-Neal-R" }, { "family_name": "Schmidt", "given_name": "J.", "clpid": "Schmidt-J" }, { "family_name": "Colombo", "given_name": "P.", "clpid": "Colombo-P" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "To better understand the impact of complex structure on mechanical properties in additively manufactured ceramics, truss structures were 3D printed in preceramic polymer and mechanically evaluated in the pyrolyzed SiOC state. Specimens were printed using digital light processing with a siloxane polymer resin blend. Four different designs were printed: two bending-dominant Kelvin cell structures, a stretching-dominant octet structure, and a mixture of the two with geometries chosen for equivalent stiffness. Mechanical characterization was done at multiple length scales: uniaxial compression to evaluate the entire truss structure, and three-point flexure to assess individual beam elements. After pyrolysis, it was found that truss designs exhibited different shrinkages at the beam element scale despite being composed of the same preceramic polymer and exhibiting isotropic shrinkage at the macro-truss scale. This manner of nonuniform shrinkage has rarely, if ever been reported, as it is standard practice in additive manufacturing to report only bulk linear shrinkage. In uniaxial compression, Kelvin structures with thicker beams exhibited the highest strength of 10 MPa, and octet structures exhibited the lowest strength of 3.8 MPa. In beam element flexure however, the octet beams had the highest strength, 1.9 GPa, four times stronger than the Kelvin beam elements and 500 times stronger than the octet bulk structure. Lastly, the implications for interchangeable truss structures are discussed.", "doi": "10.1016/j.addma.2019.100957", "issn": "2214-8604", "publisher": "Elsevier", "publication": "Additive Manufacturing", "publication_date": "2020-01", "volume": "31", "pages": "Art. No. 100957" }, { "id": "authors:5rrhw-jse87", "collection": "authors", "collection_id": "5rrhw-jse87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190904-112355921", "type": "article", "title": "Robust Cellular Shape-Memory Ceramics via Gradient\u2010Controlled Freeze Casting", "author": [ { "family_name": "Zeng", "given_name": "Xiaomei", "clpid": "Zeng-Xiaomei" }, { "family_name": "Arai", "given_name": "Noriaki", "orcid": "0000-0002-3040-2997", "clpid": "Arai-Noriaki" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Shape\u2010memory ceramics offer promise for applications like actuation and energy damping, due to their unique properties of high specific strength, high ductility, light weight and inertness in harsh environments. To date, shape\u2010memory behavior in ceramics is limited to micro/submicro\u2010scale pillars and particles to circumvent the longstanding problem of transformation\u2010induced fracture which occurs readily in bulk polycrystalline specimens. The challenge, therefore, lies in the realization of shape\u2010memory properties in bulk ceramics, which requires careful design of three\u2010dimensional structures that locally mimic pillar structures. In this work, it is demonstrated that with a gradient\u2010controlled freeze\u2010casting approach, honeycomb\u2010like cellular structures can be fabricated with thin and directionally aligned walls to facilitate martensitic transformation under compression without fracture. With this approach, robust bulk shape\u2010memory ceramics have been demonstrated in a highly porous structure with strengths under compressive stresses of 25 MPa and strains up to 7.5%.", "doi": "10.1002/adem.201900398", "issn": "1438-1656", "publisher": "Wiley", "publication": "Advanced Engineering Materials", "publication_date": "2019-12", "series_number": "12", "volume": "21", "issue": "12", "pages": "Art. No. 1900398" }, { "id": "authors:4mq2s-4ek78", "collection": "authors", "collection_id": "4mq2s-4ek78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190614-153313032", "type": "article", "title": "Obreimoff revisited: controlled heterogeneous fracture through the splitting of mica", "author": [ { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Brodnik", "given_name": "N. R.", "clpid": "Brodnik-N-R" }, { "family_name": "Ekeh", "given_name": "T.", "clpid": "Ekeh-T" }, { "family_name": "Bhattacharya", "given_name": "K.", "orcid": "0000-0003-2908-5469", "clpid": "Bhattacharya-K" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Obreimoff reported his first instrumented measurements of the cleavage of muscovite mica in 1930 and that work helped to propel a greater understanding of fracture. This study builds upon that effort by investigating the role of compliance heterogeneities in brittle materials through mica splitting in a manner similar to Obreimoff. The natural layered structure of mica makes it ideal as a model system for studying fracture as crack propagation can be constrained along a single controlled cleavage plane. Cleavage through the insertion of a rounded wedge provides a straightforward mechanical setup that produces stable crack propagation, so long as the effects of friction and wedge geometry are properly considered. First, homogeneous mica sheets of uniform thickness are cleaved in ambient atmosphere to establish a baseline splitting force and critical strain energy release rate, similar Obreimoff's original work. After establishing this baseline, mica sheets with prescribed thickness heterogeneities are investigated. It is found that the splitting force required to propagate a crack along a specimen with a sharp increase in layer thickness is significantly larger than the analogous homogeneous splitting forces, even though the crack is not deflected. This indicates that a sharp increase in stiffness can produce an increase in toughness in layered structures without the need for any actual toughness contrast between constituent components or any crack deflection. This toughening effect produced by compliance contrast may have implications in the context of layered ceramic composite design, where systems are often composed of a stiff outer shell and a more compliant and damage-tolerant functional layer.", "doi": "10.1016/j.mechmat.2019.103088", "issn": "0167-6636", "publisher": "Elsevier", "publication": "Mechanics of Materials", "publication_date": "2019-09", "volume": "136", "pages": "Art. No. 103088" }, { "id": "authors:kfa6q-y3427", "collection": "authors", "collection_id": "kfa6q-y3427", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20190107-100348482", "type": "article", "title": "Out-of-plane mechanical characterization of acicular mullite and aluminum titanate diesel particulate filters", "author": [ { "family_name": "Brodnik", "given_name": "Neal R.", "clpid": "Brodnik-N-R" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "This study characterizes the flexural and compressive behavior of two porous ceramic honeycombs commonly used in diesel particulate filtration, acicular mullite and aluminum titanate. Compression along the axis normal to the honeycomb cross\u2010section, referred to as out\u2010of\u2010plane compression, is compared to in\u2010plane flexure. The relationship between these loading modes is assessed using the failure strength and elastic modulus of the honeycomb structure and the constituent wall material. Weibull analyzes showed that flexure and out\u2010of\u2010plane compression exhibit similar behavior in cases where failure is governed by a single flaw, such as in acicular mullite. However, in heavily microcracked systems like aluminum titanate, compressive failure occurs by damage accumulation rather than growth of a single flaw, so compressive failure strengths are higher than flexural ones. Buckling was also shown to occur in both systems, but the geometries required are unlikely to be encountered in practical application. In the context of filter life assessment, failure in flexure occurs at much lower stresses for systems that rely on microcracking to accommodate thermal strains, so flexure is better suited as an estimate of filter strength.", "doi": "10.1111/ijac.13161", "issn": "1546-542X", "publisher": "Wiley", "publication": "International Journal of Applied Ceramic Technology", "publication_date": "2019-05", "series_number": "3", "volume": "16", "issue": "3", "pages": "1173-1183" }, { "id": "authors:s9kcg-8rv23", "collection": "authors", "collection_id": "s9kcg-8rv23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181107-085123398", "type": "article", "title": "Hierarchical porous ceramics via two-stage freeze casting of preceramic polymers", "author": [ { "family_name": "Arai", "given_name": "Noriaki", "orcid": "0000-0002-3040-2997", "clpid": "Arai-Noriaki" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Freeze-cast porous ceramics are of interest due to a broad range of applications such as filters, bioscaffolds, and catalyst supports. However, achieving the desired mechanical strength while retaining sufficient functionality, such as permeability, has been challenging. In this work, hierarchical structures of bridged lamellar pores were created via two-stage freeze casting of a preceramic polymer to enhance compressive strength of the resulting SiOC. It has been shown that the bridge density can be controlled by changing the concentration of preceramic polymer in solution and compressive strength increased approximately threefold while permeability constants ranged from 9.63\u202f\u00d7\u202f10^(\u221213) to 3.96\u202f\u00d7\u202f10^(\u221212)\u202fm^2.", "doi": "10.1016/j.scriptamat.2018.10.037", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2019-03-15", "volume": "162", "pages": "72-76" }, { "id": "authors:6yfh5-qmj22", "collection": "authors", "collection_id": "6yfh5-qmj22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180713-090924787", "type": "article", "title": "Dense Freeze\u2010cast Li_7La_3Zr_2O_(12) Solid Electrolytes with Oriented Open Porosity and Contiguous Ceramic Scaffold", "author": [ { "family_name": "Buannic", "given_name": "Lucienne", "orcid": "0000-0003-3055-4058", "clpid": "Buannic-L" }, { "family_name": "Naviroj", "given_name": "Maninpat", "clpid": "Naviroj-M" }, { "family_name": "Miller", "given_name": "Sarah M.", "orcid": "0000-0001-8462-1063", "clpid": "Miller-S-M" }, { "family_name": "Zagorski", "given_name": "Jakub", "clpid": "Zagorski-J" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Llord\u00e9s", "given_name": "Anna", "clpid": "Llord\u00e9s-A" } ], "abstract": "Freeze casting is used for the first time to prepare solid electrolyte scaffolds with oriented porosity and dense ceramic walls made of Li_7La_3Zr_2O_(12) (LLZO), one of the most promising candidates for solid state battery electrolytes. Processing parameters \u2010 such as solvent solidification rate, solvent type, and ceramic particle size \u2010 are investigated, focusing on their influence on porosity and ceramic wall density. Dendrite\u2010like porosity is obtained when using cyclohexane and dioxane as solvents. Lamellar porosity is observed in aqueous slurries resulting in a structure with the highest apparent porosity and densest ceramic scaffold but weakest mechanical properties due to the lack of interlamellar support. The use of smaller LLZO particle size in the slurries resulted in lower porosity and denser ceramic walls. The intrinsic ionic conductivity of the oriented LLZ ceramic scaffold is unaffected by the freeze casting technique, providing a promising ceramic scaffold for polymer infill in view of designing new types of ceramic\u2010polymer composites.", "doi": "10.1111/jace.15938", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2019-03", "series_number": "3", "volume": "102", "issue": "3", "pages": "1021-1029" }, { "id": "authors:p0bt6-4t124", "collection": "authors", "collection_id": "p0bt6-4t124", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181107-112508653", "type": "article", "title": "In-situ observation of evolving microstructural damage and associated effective electro-mechanical properties of PZT during bipolar electrical fatigue", "author": [ { "family_name": "Tan", "given_name": "Wei Lin", "clpid": "Tan-Wei-Lin" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Kochmann", "given_name": "Dennis M.", "orcid": "0000-0002-9112-6615", "clpid": "Kochmann-D-M" } ], "abstract": "We investigate the fatigue behavior of bulk polycrystalline lead zirconate titanate (PZT) during bipolar electric field cycling. We characterize the frequency- and cycle-dependent degradation in both the effective electro-mechanical properties (specifically, the electrical hysteresis and the macroscopic viscoelastic stiffness and damping measured by Broadband Electromechanical Spectroscopy, BES) and the microstructural damage evolution (quantified via scanning electron microscopy). The BES setup enables the mechanical characterization while performing electrical cycling so as to measure the evolving viscoelasticity without remounting the sample; particularly measuring the viscoelastic damping allows us to gain insight into the ferroelectric domain wall activity across the full electric hysteresis and over the full range of cycles. A clear dependence on the electric cycling frequency is observed in the rates of degradation of all measured properties including an up to 10% increase in dynamic compliance and a 70% decrease in electric displacement magnitude. We quantify the evolving micro-crack density across wide ranges of numbers of cycles and compare with changes in the effective compliance. Interestingly, the observed strong degradation in the ferroelectric hysteresis is contrasted by relatively mild changes in the effective viscoelastic moduli, while samples clearly indicate increasing levels of micro-damage.", "doi": "10.1016/j.actamat.2018.10.065", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2019-02-01", "volume": "164", "pages": "704-713" }, { "id": "authors:4ggyk-ve688", "collection": "authors", "collection_id": "4ggyk-ve688", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20180713-131315182", "type": "article", "title": "Freeze-Cast Alumina Pore Networks: Effects of Processing Parameters in Steady-State Solidification Regimes of Aqueous Slurries", "author": [ { "family_name": "Miller", "given_name": "S. M.", "orcid": "0000-0001-8462-1063", "clpid": "Miller-S-M" }, { "family_name": "Xiao", "given_name": "X.", "clpid": "Xiao-Xiaolin" }, { "family_name": "Setlock", "given_name": "J. A.", "clpid": "Setlock-J-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Aqueous alumina slurries with varying solids loading and particle size were freeze-cast under seven freezing conditions to investigate the influence of these on pore network characteristics including pore size and geometric specific surface area. Slurry temperatures were recorded in situ to determine freezing front position and velocity during solidification, which were then analyzed via regression and modeled using solidification theory. Classic mathematical models for the time dependence of freezing front position and velocity were found to hold for freeze-cast slurries. Building on these, a one-phase Stefan problem was used to describe freezing kinetics. Models for freezing front velocity were combined with solidification theory to obtain predictions of microstructural feature size from freezing kinetics. Results showed that, while there may be a dependence on solids loading, the combination of mathematical modeling of solidification and classic solidification theory is applicable to freeze-cast ceramics and accurately describes pore network characteristics from processing parameters.", "doi": "10.1016/j.jeurceramsoc.2018.07.009", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2018-12", "series_number": "15", "volume": "38", "issue": "15", "pages": "5134-5143" }, { "id": "authors:02cnd-acb13", "collection": "authors", "collection_id": "02cnd-acb13", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181001-131357242", "type": "article", "title": "Julia Randall Weertman (1926\u20132018)", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Julia Randall Weertman, on receiving the Materials Research Society's highest honour, the Von Hippel Award, in 2003, gave a lecture entitled 'The Pursuit of the Small', referring to her groundbreaking work on grain boundary cavities and nanocrystalline metals. How satisfying that this pioneering materials scientist, in pursuit of the small, had such a larger-than-life career. Weertman passed away on 31 July 2018 in Evanston, Illinois.", "doi": "10.1038/s41563-018-0195-1", "issn": "1476-1122", "publisher": "Nature Publishing Group", "publication": "Nature Materials", "publication_date": "2018-11", "series_number": "11", "volume": "17", "issue": "11", "pages": "949" }, { "id": "authors:bmhz7-4qf61", "collection": "authors", "collection_id": "bmhz7-4qf61", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20181105-080720122", "type": "conference_item", "title": "Freeze casting of porous zirconia through sol-gel", "author": [ { "family_name": "Garcia Ponte", "given_name": "Elizabeth", "clpid": "Garcia-Ponte-E" }, { "family_name": "Zeng", "given_name": "Xiaomei", "clpid": "Zeng-Xiaomei" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Shape memory materials experience diffusionless phase transitions through martensitic transformations where the material returns to its original phase after heat is applied (shape memory), or where it returns on its own (superelasticity). In ceramics, this transformation is optimized at high surface area-to-vol. ratios, where cracking due to the transitions is reduced. Freeze casting is a technique used to make porous materials which have high surface area and low d. Sol-gel processing allows for good control over the fabrication of ceramic powders, and consequently, the microstructure. We propose that by combining sol-gel and directional freeze casting, a homogeneous and directional zirconia porous structure can be achieved. By controlling the chem. compns. of acetylacetone and water (Zr/AcAc/H_2O 1/0.1/7.5 molar ratio), and thus, balancing the processes of hydrolysis and polycondensation, a suspension was produced which was made into a porous foam by freeze casting. Freezing conditions at -30\u00b0C yielded ceramic foams with minimal cracking, micropores, and 1-2 \uf06dm wall thickness. Ceramics sintered at 1500\u00b0C were found to have a higher grain d. and larger grain sizes than those sintered at 1200\u00b0C and 1400\u00b0C. The mech. properties were studied by compressing the sintered ceramics, and their correlation with the microstructure were explored.", "publisher": "Caltech Library", "publication_date": "2018-11" }, { "id": "authors:vnpna-wvf82", "collection": "authors", "collection_id": "vnpna-wvf82", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170825-143142523", "type": "article", "title": "Freeze-cast yttria-stabilized zirconia pore networks: Effects of alcohol additives", "author": [ { "family_name": "Miller", "given_name": "Sarah", "orcid": "0000-0001-8462-1063", "clpid": "Miller-S-M" }, { "family_name": "Xiao", "given_name": "Xianghui", "orcid": "0000-0002-7142-3452", "clpid": "Xiao-Xianghui" }, { "family_name": "Setlock", "given_name": "John", "clpid": "Setlock-J-A" }, { "family_name": "Farmer", "given_name": "Serene", "clpid": "Farmer-S-C" }, { "family_name": "Faber", "given_name": "Katherine", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Freeze casting yttria-stabilized zirconia (YSZ) can be useful in making electrodes for solid oxide fuel cells (SOFCs) by introducing hierarchical porosity to increase triple-phase boundary (TPB) area while maintaining adequate fuel flow. In this study the influence of alcohol additives on pore structure of aqueous YSZ freeze-cast samples was investigated. Slurries with ethanol, iso-propyl alcohol, or methanol as additives were compared to a control sample. Pore characteristics along sample lengths were measured using X-ray computed tomography reconstructions. The control sample showed significant changes in pore size along sample length, whereas pore size of the alcohol additive samples remained similar, indicating that freezing rates of the additive samples remained constant during solidification. Ice lens formation and interactions between alcohols and slurry functional additives (dispersant, surfactant, and binder) resulted in complex pore structures which show promise in increasing SOFC TPB area.", "doi": "10.1111/ijac.12794", "issn": "1546-542X", "publisher": "Wiley", "publication": "International Journal of Applied Ceramic Technology", "publication_date": "2018-03", "series_number": "2", "volume": "15", "issue": "2", "pages": "296-306" }, { "id": "authors:bb3rk-r2c39", "collection": "authors", "collection_id": "bb3rk-r2c39", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20171026-133814643", "type": "article", "title": "Suspension- and solution-based freeze casting for porous ceramics", "author": [ { "family_name": "Naviroj", "given_name": "Maninpat", "orcid": "0000-0001-9426-6990", "clpid": "Naviroj-Maninpat" }, { "family_name": "Voorhees", "given_name": "Peter W.", "orcid": "0000-0003-2769-392X", "clpid": "Voorhees-Peter-W" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Freeze casting of traditional ceramic suspensions and freeze casting of preceramic polymer solutions were directly compared as methods for processing porous ceramics. Alumina and polymethylsiloxane were freeze cast with four different organic solvents (cyclooctane, cyclohexane, dioxane, and dimethyl carbonate) to obtain ceramics with \u223c70% porosity. Median pore sizes were smaller for solution freeze casting than for suspension freeze casting under identical processing conditions. The pore structures, which range from foam-like to lamellar, were correlated to the Jackson \u03b1-factor of the solvent; solvents with low \u03b1-factors yielded nonfaceted pore structures, while high \u03b1-factors produced more faceted structures. Intermediate \u03b1-factors resulted in dendritic pore structures and were most sensitive to the processing method. Small suspended particles ahead of a solid\u2013liquid interface are hypothesized to destabilize the dendrite tip in suspension freeze casting resulting in more foam-like structures. Differences in processing details were highlighted, particularly regarding the improved freezing front observation possible with solution-based freeze casting.", "doi": "10.1557/jmr.2017.133", "issn": "0884-2914", "publisher": "Cambridge University Press", "publication": "Journal of Materials Research", "publication_date": "2017-09-14", "series_number": "17", "volume": "32", "issue": "17", "pages": "3372-3382" }, { "id": "authors:g72pd-8f037", "collection": "authors", "collection_id": "g72pd-8f037", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170825-084546752", "type": "article", "title": "X-ray nanotomography analysis of the microstructural evolution of LiMn_2 O_4 electrodes", "author": [ { "family_name": "Liu", "given_name": "Zhao", "orcid": "0000-0003-0370-2406", "clpid": "Liu-Zhao" }, { "family_name": "Han", "given_name": "Kai", "clpid": "Han-Kai" }, { "family_name": "Chen-Wiegart", "given_name": "Yu-chen Karen", "clpid": "Chen-Wiegart-Y-K" }, { "family_name": "Wang", "given_name": "Jiajun", "clpid": "Wang-Jiajun" }, { "family_name": "Kung", "given_name": "Harold H.", "clpid": "Kung-Harold-H" }, { "family_name": "Wang", "given_name": "Jun", "clpid": "Wang-Jun" }, { "family_name": "Barnett", "given_name": "Scott A.", "clpid": "Barnett-S-A" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "One of the greatest challenges for advancing lithium-ion battery (LIB) technology is to minimize cell degradation during operation for long-term stability. To this end, it is important to understand how cell performance during operation relates to complex LIB microstructures. In this report, transmission X-ray microscopy (TXM) nanotomography is used to gain quantitative three-dimensional (3D) microstructure-performance correlations of LIB cathodes during cycling. The 3D microstructures of LiMn_2O_4 (LMO) electrodes, cycled under different conditions, including cycle number, operating voltage, and temperature, are characterized via TXM and statistically analyzed to investigate the impact of cycling conditions on the electrode microstructural evolution and cell performance. It is found that the number of cracks formed within LMO particles correlated with capacity fade. For the cell cycled at elevated temperatures, which exhibits the most severe capacity fade among all cells tested, mechanical cracking observed in TXM is not the only dominant contributor to the observed degradation. Mn^(2+) dissolution, as verified by detection of Mn on the counter electrode by energy dispersive spectrometry, also contributed. The current work demonstrate 3D TXM nanotomography as a powerful tool to help probe in-depth understanding of battery failure mechanisms, which could be applicable to electrode structure optimization for advancing LIB development.", "doi": "10.1016/j.jpowsour.2017.06.027", "issn": "0378-7753", "publisher": "Elsevier", "publication": "Journal of Power Sources", "publication_date": "2017-08-31", "volume": "360", "pages": "460-469" }, { "id": "authors:9vnwf-ejv91", "collection": "authors", "collection_id": "9vnwf-ejv91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170424-093007210", "type": "article", "title": "The role of ceramic and glass science research in meeting societal challenges: Report from an NSF-sponsored workshop", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Under the sponsorship of the U.S. National Science Foundation, a workshop on emerging research opportunities in ceramic and glass science was held in September 2016. Reported here are proceedings of the workshop. The report details eight challenges identified through workshop discussions: Ceramic processing: Programmable design and assembly; The defect genome: Understanding, characterizing, and predicting defects across time and length scales; Functionalizing defects for unprecedented properties; Ceramic flatlands: Defining structure-property relations in free-standing, supported, and confined two-dimensional ceramics; Ceramics in the extreme: Discovery and design strategies; Ceramics in the extreme: Behavior of multimaterial systems; Understanding and exploiting glasses and melts under extreme conditions; and Rational design of functional glasses guided by predictive modeling. It is anticipated that these challenges, once met, will promote basic understanding and ultimately enable advancements within multiple sectors, including energy, environment, manufacturing, security, and health care.", "doi": "10.1111/jace.14881", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2017-05", "series_number": "5", "volume": "100", "issue": "5", "pages": "1777-1803" }, { "id": "authors:j9fwh-8mz03", "collection": "authors", "collection_id": "j9fwh-8mz03", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170407-083807485", "type": "article", "title": "Nucleation-controlled freeze casting of preceramic polymers for uniaxial pores in Si-based ceramics", "author": [ { "family_name": "Naviroj", "given_name": "Maninpat", "clpid": "Naviroj-M" }, { "family_name": "Wang", "given_name": "Melody M.", "clpid": "Wang-M-M" }, { "family_name": "Johnson", "given_name": "Matthew T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A grain-selection template was applied to freeze casting to control nucleation of pore-forming crystals and achieve ceramics with highly aligned pore structures. A polymethylsiloxane preceramic polymer was freeze cast with cyclohexane as a solvent to produce dendritic pores in SiOC. Image analysis and permeability measurements were performed to quantify the influence of various templates on sample properties. Results show that the percentage of porosity aligned along the freezing axis increased from 13.9% without a template to 92.6% with an optimal template. The Darcian permeability constant increased by more than 6-fold, from 3.4 \u00d7 10^(\u221212) to 2.1 \u00d7 10^(\u221211) m^2.", "doi": "10.1016/j.scriptamat.2016.10.038", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2017-03-15", "volume": "130", "pages": "32-36" }, { "id": "authors:w5d6q-gdj76", "collection": "authors", "collection_id": "w5d6q-gdj76", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20170227-085745824", "type": "article", "title": "Experimental Model Validation of High Aspect Ratio Through-Hole Filling by Additive-Assisted Copper Electrodeposition", "author": [ { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Keck", "given_name": "C. H. C.", "clpid": "Keck-C-H-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A multi-element, time-dependent model developed by Childers et al. [A.S. Childers, M.T. Johnson, J. Ram\u00edrez-Rico, and K.T. Faber, J. Electrochem. Soc., 160:3093-3102, 2013] for copper infiltration of large (\u223c50\u2013200 \u00b5m diameter), high aspect ratio (\u223c60) through-hole channels was experimentally tested for validity. The model built on the work of Akolkar and Landau [R. Akolkar and U. Landau, J. Electrochem. Soc., 151:702-711, 2004] for copper deposition in micro-scale integrated circuitry. Childers' model broadens the original by including the transport and adsorption of all electrolyte species - inhibitors, accelerators, and copper ions. The resulting model is tested experimentally with wood-derived biomorphic carbon materials. Results indicate that model predictions of premature pore choke off are in agreement with quantitative observations of copper infiltration and qualitative imaging of plated pore profiles. Low accelerator concentrations (0.002 ppm) yielded the highest quantity of copper infiltration without premature closure.", "doi": "10.1149/2.0391702jes", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "2017-01", "series_number": "2", "volume": "164", "issue": "2", "pages": "D48-D52" }, { "id": "authors:br5nw-43k02", "collection": "authors", "collection_id": "br5nw-43k02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160602-160330647", "type": "article", "title": "Interfacial frictional stresses and fracture toughness of biomorphic graphite/copper interfaces", "author": [ { "family_name": "Childers", "given_name": "A. S.", "clpid": "Childers-A-S" }, { "family_name": "Brodnik", "given_name": "N. R.", "clpid": "Brodnik-N-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A fiber push-in test was adapted to measure the interfacial frictional stresses present in wood-derived biomorphic graphite/copper interpenetrating phase composites. Additionally, a sandwich composite was used to measure the interfacial fracture toughness of the copper/graphite system. Results indicate that due to poor wetting of copper on graphite, the surface roughness and extent of mechanical interlocking between the two phases determine the mechanical characteristics of the interface, and that the values are comparable to other metal-ceramic composite systems with limited bonding. A characterization of the mechanically bonded interfaces is vital to understanding load transfer, thermal cycling effects, contact resistance, and thermal conductivity.", "doi": "10.1016/j.matlet.2016.03.065", "issn": "0167-577X", "publisher": "Elsevier", "publication": "Materials Letters", "publication_date": "2016-07-01", "volume": "174", "pages": "106-109" }, { "id": "authors:f1t0n-46e33", "collection": "authors", "collection_id": "f1t0n-46e33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160401-105848310", "type": "conference_item", "title": "Watching paint dry: Assessing the curing and aging of modern oil-based paints", "author": [ { "family_name": "Faber", "given_name": "Katherine", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Sturdy", "given_name": "Lauren", "clpid": "Sturdy-L" }, { "family_name": "Wright", "given_name": "Madeleine", "clpid": "Wright-M" }, { "family_name": "Shull", "given_name": "Kenneth", "clpid": "Shull-K-R" }, { "family_name": "Casadio", "given_name": "Francesca", "clpid": "Casadio-F" }, { "family_name": "Muir", "given_name": "Kimberley", "clpid": "Muir-K" } ], "abstract": "The mech. properties of artists' paint films have been the subject of few investigations. Their study is\nnevertheless important because of its implications for the deterioration, handling, storage, and treatment of\npaintings. Tensile strength measurements provide insight into the mech. properties of paint strips, but the\nsample sizes required for these tests limit their applicability to actual artworks. In this partnership between the\nArt Institute of Chicago and Northwestern University, we explore the use of two techniques for studying the\nmech. behavior of artists' paints as well as model systems of pigment-filled and unfilled alkyd resins. Firstly,\nwe use a quartz crystal microbalance (QCM) to measure the phys. properties of the model systems during\ncuring in real time. The technique is sensitive to both mass changes and the dynamic shear modulus, in\nambient conditions as well as at elevated temps. Secondly, nanoindentation is employed to investigate the\nproperties of the same paint films as a function of curing time, providing both hardness and elastic modulus\nfrom small vols.; artists' paints are similarly examd. Finally the two techniques are compared as\ncomplementary methods for establishing the dynamic behavior of paint films.", "publisher": "Caltech Library", "publication_date": "2016-03" }, { "id": "authors:e8e9y-1pg55", "collection": "authors", "collection_id": "e8e9y-1pg55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160303-131553645", "type": "article", "title": "The influence of calcium\u2013magnesium\u2013aluminosilicate deposits on internal stresses in Yb_2Si_2O_7 multilayer environmental barrier coatings", "author": [ { "family_name": "Stolzenburg", "given_name": "F.", "clpid": "Stolzenburg-F" }, { "family_name": "Kenesei", "given_name": "P.", "clpid": "Kenesei-P" }, { "family_name": "Almer", "given_name": "J.", "clpid": "Almer-J-D" }, { "family_name": "Lee", "given_name": "K. N.", "clpid": "Lee-K-N" }, { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The interaction of calcium-magnesium-aluminosilicates (CMAS) with Yb_2Si_2O_7-based multilayer environmental barrier coatings was studied using a combination of high-energy synchrotron X-ray techniques. Changes in the phase-specific stresses and lattice spacings as a function of temperature were investigated with wide-angle X-ray scattering. Small-angle X-ray scattering was used to study the interaction of CMAS with nanoporosity, while X-ray computed tomography was used to study the formation of cracks in the coating. It was found that CMAS interacts strongly with the Yb_2Si_2O_7 topcoat, leading to changes in lattice spacing, alterations of the ambient temperature stresses, and large cracks in the CMAS that extend through the topcoat.", "doi": "10.1016/j.actamat.2015.12.016", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2016-02-15", "volume": "105", "pages": "189-198" }, { "id": "authors:r1dcb-9ae48", "collection": "authors", "collection_id": "r1dcb-9ae48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160701-072111054", "type": "article", "title": "Three-Phase 3D Reconstruction of a LiCoO_2 Cathode via FIB-SEM Tomography", "author": [ { "family_name": "Liu", "given_name": "Zhao", "orcid": "0000-0003-0370-2406", "clpid": "Liu-Zhao" }, { "family_name": "Chen-Wiegart", "given_name": "Yu-chen K.", "clpid": "Chen-Wiegart-Y-K" }, { "family_name": "Wang", "given_name": "Jun", "clpid": "Wang-Jun" }, { "family_name": "Barnett", "given_name": "Scott A.", "clpid": "Barnett-S-A" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Three-phase three-dimensional (3D) microstructural reconstructions of lithium-ion battery electrodes are critical input for 3D simulations of electrode lithiation/delithiation, which provide a detailed understanding of battery operation. In this report, 3D images of a LiCoO_2 electrode are achieved using focused ion beam-scanning electron microscopy (FIB-SEM), with clear contrast among the three phases: LiCoO_2 particles, carbonaceous phases (carbon and binder) and the electrolyte space. The good contrast was achieved by utilizing an improved FIB-SEM sample preparation method that combined infiltration of the electrolyte space with a low-viscosity silicone resin and triple ion-beam polishing. Morphological parameters quantified include phase volume fraction, surface area, feature size distribution, connectivity, and tortuosity. Electrolyte tortuosity was determined using two different geometric calculations that were in good agreement. The electrolyte tortuosity distribution versus position within the electrode was found to be highly inhomogeneous; this will lead to inhomogeneous electrode lithiation/delithiation at high C-rates that could potentially cause battery degradation.", "doi": "10.1017/S1431927615015640", "issn": "1431-9276", "publisher": "Cambridge University Press", "publication": "Microscopy and Microanalysis", "publication_date": "2016-02", "series_number": "01", "volume": "22", "issue": "01", "pages": "140-148" }, { "id": "authors:eed8y-3jw79", "collection": "authors", "collection_id": "eed8y-3jw79", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20160204-125158377", "type": "article", "title": "The interaction of calcium\u2013magnesium\u2013aluminosilicate with ytterbium silicate environmental barrier materials", "author": [ { "family_name": "Stolzenburg", "given_name": "F.", "clpid": "Stolzenburg-F" }, { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Lee", "given_name": "K. N.", "clpid": "Lee-K-N" }, { "family_name": "Jacobson", "given_name": "N. S.", "clpid": "Jacobson-N-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The interactions of two potential topcoat materials for environmental barrier coatings, Yb_2SiO_5 and Yb_2Si_2O_7, with calcium-magnesium-aluminosilicate (CMAS) engine deposits were studied. X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron diffraction were used to investigate the phase transformation associated with the exposure of Yb_2SiO_5 and Yb_2Si_2O_7 to CMAS at 1300 \u00b0C. It was found that Yb_2SiO_5 strongly reacts with CMAS to completely dissolve the Yb_2SiO_5 and form hexagonal Ca_2Yb_8(SiO_4)_6O_2 deposits. In contrast, no discernable reaction between CMAS and Yb_2Si_2O_7, was observed over the 96-h exposure.", "doi": "10.1016/j.surfcoat.2015.08.069", "issn": "0257-8972", "publisher": "Elsevier", "publication": "Surface and Coatings Technology", "publication_date": "2015-12-25", "volume": "284", "pages": "44-50" }, { "id": "authors:pfzev-1a773", "collection": "authors", "collection_id": "pfzev-1a773", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150826-112119743", "type": "article", "title": "Freeze-cast alumina pore networks: Effects of freezing conditions and dispersion medium", "author": [ { "family_name": "Miller", "given_name": "S. M.", "orcid": "0000-0001-8462-1063", "clpid": "Miller-S-M" }, { "family_name": "Xiao", "given_name": "X.", "clpid": "Xiao-X" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Alumina ceramics were freeze-cast from water- and camphene-based slurries under varying freezing conditions and examined using X-ray computed tomography (XCT). Pore network characteristics, i.e., porosity, pore size, geometric surface area, and tortuosity, were measured from XCT reconstructions and the data were used to develop a model to predict feature size from processing conditions. Classical solidification theory was used to examine relationships between pore size, temperature gradients, and freezing front velocity. Freezing front velocity was subsequently predicted from casting conditions via the two-phase Stefan problem. Resulting models for water-based samples agreed with solidification-based theories predicting lamellar spacing of binary eutectic alloys, and models for camphene-based samples concurred with those for dendritic growth. Relationships between freezing conditions and geometric surface area were also modeled by considering the inverse relationship between pore size and surface area. Tortuosity was determined to be dependent primarily on the type of dispersion medium.", "doi": "10.1016/j.jeurceramsoc.2015.05.012", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2015-11", "series_number": "13", "volume": "35", "issue": "13", "pages": "3595-3605" }, { "id": "authors:wx0xa-1d542", "collection": "authors", "collection_id": "wx0xa-1d542", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210114-140128973", "type": "article", "title": "On-Site Identification of Early B\u00f6ttger Red Stoneware Using Portable XRF/Raman Instruments: 2, Glaze & Gilding Analysis", "author": [ { "family_name": "Simsek", "given_name": "Gulsu", "clpid": "Simsek-Gulsu" }, { "family_name": "Colomban", "given_name": "Philippe", "clpid": "Colomban-Philippe" }, { "family_name": "Casadio", "given_name": "Francesca", "clpid": "Casadio-Francesca" }, { "family_name": "Bellot-Gurlet", "given_name": "Ludovic", "clpid": "Bellot-Gurlet-Ludovic" }, { "family_name": "Zelleke", "given_name": "Ghenete", "clpid": "Zelleke-Ghenete" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Milande", "given_name": "V\u00e9ronique", "clpid": "Milande-V\u00e9ronique" }, { "family_name": "Tilliard", "given_name": "Laurence", "clpid": "Tilliard-Laurence" } ], "abstract": "Twenty\u2010one glazed red stoneware objects, with gilded or gold\u2010painted decor from different collections (Cit\u00e9 de la C\u00e9ramique, S\u00e8vres, France; Art Institute of Chicago, USA; a private collection) attributed to 18th century B\u00f6ttger, Meissen (Saxony) have been analyzed with a portable X\u2010ray fluorescence spectrometer (XRF) and portable or fixed Raman micro\u2010spectrometer in laboratory/museum/collector rooms. Analysis was aimed at gaining a deeper understanding of the technology of production of the gilding and black glaze, to augment what is known from the limited literature. Three different techniques to obtain a golden d\u00e9cor emerged as a result of this study: (i) a true gilding with gold, (ii) gold with mercury, and (iii) an alloy of copper and zinc.", "doi": "10.1111/jace.13720", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2015-10", "series_number": "10", "volume": "98", "issue": "10", "pages": "3006-3013" }, { "id": "authors:1t2sv-zb259", "collection": "authors", "collection_id": "1t2sv-zb259", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20150518-140317330", "type": "article", "title": "Directionally aligned macroporous SiOC via freeze casting of preceramic polymers", "author": [ { "family_name": "Naviroj", "given_name": "M.", "clpid": "Naviroj-M" }, { "family_name": "Miller", "given_name": "S. M.", "orcid": "0000-0001-8462-1063", "clpid": "Miller-S-M" }, { "family_name": "Colombo", "given_name": "P.", "clpid": "Colombo-P" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A commercially available polysiloxane was used as a preceramic polymer for solution freeze casting to obtain directionally aligned porous silicon oxycarbide. We show how choice of solvent, polymer concentration, and freezing rate can affect the final pore network of the freeze-cast ceramic. Solvents of cyclohexane and camphene resulted in dendritic pores, while tert-butyl alcohol (TBA) produced intersecting cellular pores in the freeze-cast ceramic. Characterization of pore size distribution by mercury intrusion porosimetry of ceramics produced from cyclohexane\u2013polysiloxane solutions with varying polymer concentrations and freezing rates demonstrated trends consistent with solidification theory. Fourier transform infrared spectroscopy and X-ray diffraction were employed to confirm that the freeze-casting process resulted in silicon oxycarbide of comparable chemistry and crystallinity to that produced via traditional preceramic polymer processing techniques.", "doi": "10.1016/j.jeurceramsoc.2015.02.013", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2015-08", "series_number": "8", "volume": "35", "issue": "8", "pages": "2225-2232" }, { "id": "authors:9kdte-v6y48", "collection": "authors", "collection_id": "9kdte-v6y48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140910-213824542", "type": "article", "title": "On-Site Identification of Early B\u00d6TTGER Red Stoneware Made at Meissen Using Portable XRF: 1, Body Analysis", "author": [ { "family_name": "Simsek", "given_name": "Gulsu", "clpid": "Simsek-G" }, { "family_name": "Casadio", "given_name": "Francesca", "clpid": "Casadio-F" }, { "family_name": "Colomban", "given_name": "Philippe", "clpid": "Colomban-P" }, { "family_name": "Bellot-Gurlet", "given_name": "Ludovic", "clpid": "Bellot-Gurlet-L" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Zelleke", "given_name": "Ghenete", "clpid": "Zelleke-G" }, { "family_name": "Milande", "given_name": "V.", "clpid": "Milande-V" }, { "family_name": "Moinet", "given_name": "Eric", "clpid": "Moinet-E" } ], "abstract": "A selection of 50 red stoneware objects, polished, unpolished, partially polished or glazed, from different collections (D\u00e9partement du Patrimoine et des Collections de la Cit\u00e9 de la C\u00e9ramique, S\u00e8vres, France; Art Institute of Chicago; a private collection), attributed to 18th century B\u00f6ttger, 20th century Meissen (Saxony) and Chinese productions have been analyzed with a portable X-ray fluorescence spectrometer in museum/collector rooms. The comparison of major (Si, Al), minor (K,Ca,Fe), and trace (Ti, Mn, Zr, Rb, Sr) element ratios was made to assist with the classification of the different artifacts as a function of their production technology and raw materials. The results are discussed in light of historical reports on the characteristics of B\u00f6ttger production and criteria of identification are proposed to distinguish between \"classical\" B\u00f6ttger (early 18th century) and other productions.", "doi": "10.1111/jace.13032", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2014-09", "series_number": "9", "volume": "97", "issue": "9", "pages": "2745-2754" }, { "id": "authors:j3342-2gf96", "collection": "authors", "collection_id": "j3342-2gf96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181318690", "type": "article", "title": "X-ray micro-computed tomography and tortuosity calculations of percolating pore networks", "author": [ { "family_name": "Shanti", "given_name": "Noah O.", "clpid": "Shanti-N-O" }, { "family_name": "Chan", "given_name": "Victor W. L.", "clpid": "Chan-V-W-L" }, { "family_name": "Stock", "given_name": "Stuart R.", "clpid": "Stock-S-R" }, { "family_name": "De Carlo", "given_name": "Francesco", "clpid": "De-Carlo-F" }, { "family_name": "Thornton", "given_name": "Katsuyo", "clpid": "Thornton-K" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Synchrotron source X-ray micro-computed tomography was used for non-destructive three-dimensional (3-D) imaging of porous alumina structures, in which the porosity was induced by a granular porogen, added in amounts of 10\u201360 vol.%. Microstructural characteristics related to transport properties, including connectivity and tortuosity, were measured from the resulting 3-D data sets. Connectivity of 94.5\u201399.6% was measured for samples produced with 35\u201360% porogen (30.8\u201349.6% porosity). Two methods of calculating tortuosity, path length ratio and gas phase flux were compared, and the effect of sample volume on calculated tortuosity value and computational time was examined. Average sample tortuosity calculated using the two methods generally agreed, although significant directional anisotropy was detected in some cases for the gas phase flux calculation method. Tortuosity values as low as 1.5 were measured for alumina components with 49.6% porosity.", "doi": "10.1016/j.actamat.2014.03.003", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2014-06", "volume": "71", "pages": "126-135" }, { "id": "authors:2gp4z-qhn34", "collection": "authors", "collection_id": "2gp4z-qhn34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-132757238", "type": "article", "title": "Wood-derived copper\u2013graphite composites produced via additive-assisted electrodeposition", "author": [ { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Childers", "given_name": "A. S.", "clpid": "Childers-A-S" }, { "family_name": "De Carlo", "given_name": "F.", "clpid": "De Carlo-F" }, { "family_name": "Xiao", "given_name": "X.", "clpid": "Xiao-X" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "An additive-assisted copper electroplating technique designed for infiltrating high-aspect-ratio pores was adapted to work with three-dimensional wood-derived graphitic scaffolds with aspect ratios ranging from 15 to 300. The poor wettability of the carbon/copper system necessitates the development of alternative infiltration techniques to produce composite structures from highly porous precursors such as wood-derived graphite. By incorporating electrolyte additives, copper infiltration was demonstrated into red oak-derived graphite scaffolds, producing a composite with a biologically-derived microstructure. Copper infiltration was studied as a function of electrolyte chemistry and deposition time in two dimensions using electron microscopy techniques and in three dimensions using X-ray computed tomography.", "doi": "10.1016/j.compscitech.2013.09.010", "issn": "0266-3538", "publisher": "Elsevier", "publication": "Composites Science and Technology", "publication_date": "2013-12-13", "volume": "89", "pages": "61-68" }, { "id": "authors:kqtwp-j5a33", "collection": "authors", "collection_id": "kqtwp-j5a33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-143238554", "type": "article", "title": "In situ imaging and strain determination during fracture in a SiC/SiC ceramic matrix composite", "author": [ { "family_name": "Ram\u00edrez-Rico", "given_name": "J.", "clpid": "Ram\u00edrez-Rico-J" }, { "family_name": "Stolzenburg", "given_name": "F.", "clpid": "Stolzenburg-F" }, { "family_name": "Almer", "given_name": "J. D.", "clpid": "Almer-J-D" }, { "family_name": "Routbort", "given_name": "J. L.", "clpid": "Routbort-J-L" }, { "family_name": "Singh", "given_name": "D.", "clpid": "Singh-D" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A combined imaging and microdiffraction technique using high-energy synchrotron X-rays is described and used to reveal microstructure, damage and strain evolution around notches in SiC/SiC composites. This technique allows for monitoring the material for cracks while loading and mapping the strain distribution in fibers and matrix with a resolution of tens of microns. We show that at current resolutions this technique is capable of measuring the strain distribution near crack tips in ceramic matrix composites and observe load transfer effects.", "doi": "10.1016/j.scriptamat.2013.05.032", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2013-10", "series_number": "7", "volume": "69", "issue": "7", "pages": "497-500" }, { "id": "authors:n26yr-nme95", "collection": "authors", "collection_id": "n26yr-nme95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-124426828", "type": "article", "title": "Thermal conductivity of wood-derived graphite and copper\u2013graphite composites produced via electrodeposition", "author": [ { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Childers", "given_name": "A. S.", "clpid": "Childers-A-S" }, { "family_name": "Ram\u00edrez-Rico", "given_name": "J.", "clpid": "Ram\u00edrez-Rico-J" }, { "family_name": "Wang", "given_name": "H.", "clpid": "Wang-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The thermal conductivity of wood-derived graphite and graphite/copper composites was studied both experimentally and using finite element analysis. The unique, naturally-derived, anisotropic porosity inherent to wood-derived carbon makes standard porosity-based approximations for thermal conductivity poor estimators. For this reason, a finite element technique which uses sample microstructure as model input was utilized to determine the conductivity of the carbon phase independent of porosity. Similar modeling techniques were also applied to carbon/copper composite microstructures and predicted conductivities compared well to those determined via experiment.", "doi": "10.1016/j.compositesa.2013.06.009", "issn": "1359-835X", "publisher": "Elsevier", "publication": "Composites Part A: Applied Science and Manufacturing", "publication_date": "2013-10", "volume": "53", "pages": "182-189" }, { "id": "authors:v4p33-v6636", "collection": "authors", "collection_id": "v4p33-v6636", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181319155", "type": "article", "title": "Small Volumes Create Super(elastic) Effects", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Anyone who has ever broken a favorite coffee cup knows that ceramic materials do not accommodate strain well. Ceramic materials typically fail at strains (extensions) of less than 0.1%. On page 1505 of this issue, Lai et al. (1) demonstrate a class of ceramics that can deform reversibly by more than 7%, rendering these solids \"superelastic.\" To put this in context, at 7% strain, an aluminum can would crumple with no hope of recovery. When Lai et al. made small chemical changes to their ceramics, they found a memory effect, whereby the solid can be permanently deformed, but upon heating reverts back to its original size and shape.", "doi": "10.1126/science.1245097", "issn": "0036-8075", "publisher": "American Association for the Advancement of Science", "publication": "Science", "publication_date": "2013-09-27", "series_number": "6153", "volume": "341", "issue": "6153", "pages": "1464-1465" }, { "id": "authors:j7yvd-qhx91", "collection": "authors", "collection_id": "j7yvd-qhx91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140709-123339432", "type": "article", "title": "Impact of doping on the mechanical properties of acicular mullite", "author": [ { "family_name": "Hsiung", "given_name": "C.-H. H.", "clpid": "Hsiung-C-H-H" }, { "family_name": "Pyzik", "given_name": "A. J.", "clpid": "Pyzik-A-J" }, { "family_name": "Gulsoy", "given_name": "E. B.", "clpid": "Gulsoy-E-B" }, { "family_name": "De Carlo", "given_name": "F.", "clpid": "De Carlo-F" }, { "family_name": "Xiao", "given_name": "X.", "clpid": "Xiao-X" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Acicular mullite (ACM) is a highly porous ceramic with a needlelike microstructure. Next-generation ACM-based diesel particulate filters will require porosities >60%, making optimizing ACM's mechanical properties a key area of interest. A prior study determined that, for the range of microstructures evaluated, the elastic modulus, strength, and fracture toughness were largely functions of total porosity and not needle or pore size, consistent with the Gibson\u2013Ashby foam model. Therefore, alternate strengthening and toughening methods were sought. Doping the ACM precursor with either MgO or Nd_2O_3 produced ACM microstructures that appeared similar but had differing bulk mechanical properties. The mechanical properties of the mullite needles, the intergranular glassy phase, and the mullite\u2013glass interface of the ACMs were investigated, but no major differences were found. Using X-ray computed tomography, a 3D imaging technique, it was found that MgO-doping of the ACM created a less uniform, and thus weaker, microstructure than Nd_2O_3-doping.", "doi": "10.1016/j.jeurceramsoc.2013.02.006", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2013-09", "series_number": "10", "volume": "33", "issue": "10", "pages": "1955-1965" }, { "id": "authors:rgxf3-ncm93", "collection": "authors", "collection_id": "rgxf3-ncm93", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-095221316", "type": "article", "title": "Modeling Macro-Sized, High Aspect Ratio Through-Hole Filling by Multi-Component Additive-Assisted Copper Electrodeposition", "author": [ { "family_name": "Childers", "given_name": "A. S.", "clpid": "Childers-A-S" }, { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Ram\u00edrez-Rico", "given_name": "J.", "clpid": "Ram\u00edrez-Rico-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A multi-element, time-dependent model is used to examine additive-assisted copper electroplating in macro-channels. This model is an adaptation of the work of Akolkar and Landau [J. Electrochem. Soc., 156, D351 (2009)], used to describe plating in micro-vias for integrated circuits. Using their method for describing species movement in the channel, the model has been expanded to include transport and adsorption limitations of the inhibitor and accelerator, as well as the copper ions in solution. The model is used to investigate copper plating as an infiltration method across many size scales and aspect ratios. Biomorphic graphite scaffolds produced from wood are used as a representative system and the results of a two-additive bath are used to characterize the behavior of the additives and determine the effectiveness of the plating. The results indicate that at macro-scales, channel dimensions play an increasingly important role in dictating the behavior of additive-assisted plating. Because additive systems are designed to establish differential surface coverage within the channel, the success of which is determined by the additive's rates of diffusion and adsorption, certain size scale/aspect ratio combinations preclude such coverage. A guide for sample geometries that may be successfully infiltrated with a two-additive bath is provided.", "doi": "10.1149/2.018312jes", "issn": "0013-4651", "publisher": "Electrochemical Society", "publication": "Journal of the Electrochemical Society", "publication_date": "2013-08-29", "series_number": "12", "volume": "160", "issue": "12", "pages": "D3093-D3102" }, { "id": "authors:4ak02-t3685", "collection": "authors", "collection_id": "4ak02-t3685", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181319264", "type": "article", "title": "Emerging Opportunities in Ceramics: Reports from the 4th International Congress on Ceramics", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Lara-Curzio", "given_name": "Edgar", "clpid": "Lara-Curzio-E" } ], "abstract": "The American Ceramic Society, in collaboration\nwith the Ceramic Society of Japan and the European\nCeramic Society, and under the leadership of the International\nCeramic Federation, initiated a series of international\nbiennial Congresses on Ceramics and Glass in\n2006. The first Congress, held in Toronto, Canada, was\na global event designed to facilitate discussion and planning\nconcerning major issues that face the ceramic and\nglass industries, culminating in the development of a historic\ntechnology roadmap for ceramics, published by\nWiley. Building on the success of the first meeting, two\nsubsequent Congresses were organized in Verona in\n2008 and Osaka in 2010, each with roadmap activities\nand proceedings. The 4th International Congress on\nCeramics (ICC4), held in Chicago, Illinois from July 15\nto 19, 2012, followed in the same vein. ICC4 was organized\nto address emerging opportunities in ceramics and\nglass disciplines in themes that included aerospace; biology\nand medicine; environment, energy, and transportation;\nelectronic, optical, and magnetic ceramics and their\ndevices; nanostructured ceramics; security and strategic\nmaterials; technology entrepreneurship; and workforce\ndevelopment. Ceramics and glass are key to enabling\ntechnology in all the aforementioned areas and offer the\npossibility of achieving greater efficiency, durability, and\nin many cases properties and functionality that cannot\nbe attained with any other class of materials.", "doi": "10.1111/ijac.12089", "issn": "1744-7402", "publisher": "Wiley", "publication": "International Journal of Applied Ceramic Technology", "publication_date": "2013-05", "series_number": "3", "volume": "10", "issue": "3", "pages": "377-378" }, { "id": "authors:0h1z4-t0f30", "collection": "authors", "collection_id": "0h1z4-t0f30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181319398", "type": "article", "title": "Three-dimensional morphological measurements of LiCoO_2 and LiCoO_2/Li (Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 lithium-ion battery cathodes", "author": [ { "family_name": "Liu", "given_name": "Zhao", "orcid": "0000-0003-0370-2406", "clpid": "Liu-Zhao" }, { "family_name": "Cronin", "given_name": "J. Scott", "clpid": "Cronin-J-S" }, { "family_name": "Chen-Wiegart", "given_name": "Yu-chen K.", "clpid": "Chen-Wiegart-Y-K" }, { "family_name": "Wilson", "given_name": "James R.", "clpid": "Wilson-J-R" }, { "family_name": "Yakal-Kremski", "given_name": "Kyle J.", "clpid": "Yakal-Kremski-K-J" }, { "family_name": "Wang", "given_name": "Jun", "clpid": "Wang-Jun" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Barnett", "given_name": "Scott A.", "clpid": "Barnett-S-A" } ], "abstract": "The three-dimensional (3D) morphologies of two types of lithium-ion battery cathodes, LiCoO_2 (LCO) and LiCoO_2/Li (Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 (LCO/NMC) composites, have been measured using focused ion beam scanning electron microscopy (FIB-SEM) and transmission X-ray microscopy (TXM). TXM measurements were taken at X-ray energies that can provide clear contrast between LCO and NMC particles in the composite cathodes. Multiple three-dimensional image volumes were collected and statistical analyses were done to assess the accuracy and spatial variation of structural parameters including oxide volume fractions, surface areas, and particle size distributions. Comparisons of un-cycled and cycled batteries showed small changes in structure, but spatial and cell-to-cell microstructural variations, found especially in the LCO/NMC cathodes, were large enough to limit the ability to distinguish actual cycling-induced structure changes. The observation of cathode metal cations on the battery anode after cycling may explain, at least in part, the observed 30% capacity loss.", "doi": "10.1016/j.jpowsour.2012.11.043", "issn": "0378-7753", "publisher": "Elsevier", "publication": "Journal of Power Sources", "publication_date": "2013-04-01", "volume": "227", "pages": "267-274" }, { "id": "authors:v9tz9-3c678", "collection": "authors", "collection_id": "v9tz9-3c678", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140709-144848100", "type": "article", "title": "Microstructure and mechanical properties of acicular mullite", "author": [ { "family_name": "Hsiung", "given_name": "C.-H. H.", "clpid": "Hsiung-C-H-H" }, { "family_name": "Pyzik", "given_name": "A. J.", "clpid": "Pyzik-A-J" }, { "family_name": "De Carlo", "given_name": "F.", "clpid": "De-Carlo-F" }, { "family_name": "Xiao", "given_name": "X.", "clpid": "Xiao-X" }, { "family_name": "Stock", "given_name": "S. R.", "clpid": "Stock-S-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Porous acicular mullite (ACM) ceramics are known to be mechanically robust even at high porosities. This study was undertaken to better understand what aspects of acicular mullite's needle-like microstructure affect the overall mechanical properties and how the microstructure might be modified to improve mechanical performance. ACMs with a variety of porosities, pore sizes, and needle diameters were produced, and their elastic moduli, flexure strengths, and fracture toughnesses were measured. Three-dimensional image analysis was an invaluable tool in determining the needle diameters of these complex 3D network structures. It was found that porosity was the most dominant factor in determining the mechanical properties of ACM and that its behavior could be described using the Gibson\u2013Ashby foam model.", "doi": "10.1016/j.jeurceramsoc.2012.09.017", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2013-03", "series_number": "3", "volume": "33", "issue": "3", "pages": "503-513" }, { "id": "authors:hka4e-ce696", "collection": "authors", "collection_id": "hka4e-ce696", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181319557", "type": "article", "title": "3D analysis of a LiCoO_2-Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 Li-ion battery positive electrode using x-ray nano-tomography", "author": [ { "family_name": "Chen-Wiegart", "given_name": "Yu-chen Karen", "clpid": "Chen-Wiegart-Y-K" }, { "family_name": "Liu", "given_name": "Zhao", "orcid": "0000-0003-0370-2406", "clpid": "Liu-Zhao" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Barnett", "given_name": "Scott A.", "clpid": "Barnett-S-A" }, { "family_name": "Wang", "given_name": "Jun", "clpid": "Wang-Jun" } ], "abstract": "A full-field high-resolution x-ray nano-tomography technique, transmission x-ray microscopy (TXM), was used to reveal the 3D morphology of the lithium ion battery composite positive electrode: LiCoO_2 (LCO)-Li(Ni_(1/3)Mn_(1/3)Co_(1/3))O_2 (NMC). The TXM method allowed the unambiguous chemical identification of oxide particles by tuning the x-ray energy relative to the transition-metal absorption edges. The NMC particles have a much rougher surface compared to the LCO particles. Cracks due to processing exist in both LCO and NMC particles but the NMC particles exhibit more severe cracking and also tend to have internal pores in addition to radial cracks. Further, the carbon-based phases including the binder and the conductive carbon were identified using Zernike phase contrast imaging.", "doi": "10.1016/j.elecom.2012.12.021", "issn": "1388-2481", "publisher": "Elsevier", "publication": "Electrochemistry Communications", "publication_date": "2013-03", "volume": "28", "pages": "127-130" }, { "id": "authors:er82k-31192", "collection": "authors", "collection_id": "er82k-31192", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181319796", "type": "article", "title": "Challenges in Ceramic Science: A Report from the Workshop on Emerging Research Areas in Ceramic Science", "author": [ { "family_name": "Rohrer", "given_name": "Gregory S.", "clpid": "Rohrer-G-S" }, { "family_name": "Affatigato", "given_name": "Mario", "clpid": "Affatigato-M" }, { "family_name": "Backhaus", "given_name": "Monika", "clpid": "Backhaus-M" }, { "family_name": "Bordia", "given_name": "Rajendra K.", "clpid": "Bordia-R-K" }, { "family_name": "Chan", "given_name": "Helen M.", "clpid": "Chan-H-M" }, { "family_name": "Curtarolo", "given_name": "Stefano", "clpid": "Curtarolo-S" }, { "family_name": "Demkov", "given_name": "Alex", "clpid": "Demkov-A" }, { "family_name": "Eckstein", "given_name": "James N.", "clpid": "Eckstein-J-N" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Garay", "given_name": "Javier E.", "clpid": "Garay-J-E" }, { "family_name": "Gogotsi", "given_name": "Yury", "clpid": "Gogtsi-Y" }, { "family_name": "Huang", "given_name": "Liping", "clpid": "Huang-Liping" }, { "family_name": "Jones", "given_name": "Linda E.", "clpid": "Jones-L-E" }, { "family_name": "Kalinin", "given_name": "Sergei V.", "clpid": "Kalinin-S-V" }, { "family_name": "Lad", "given_name": "Robert J.", "clpid": "Lad-R-J" }, { "family_name": "Levi", "given_name": "Carlos G.", "clpid": "Levi-C-G" }, { "family_name": "Levy", "given_name": "Jeremy", "clpid": "Levy-J" }, { "family_name": "Maria", "given_name": "Jon-Paul", "clpid": "Maria-J-P" }, { "family_name": "Mattos", "given_name": "Louis, Jr.", "clpid": "Mattos-L-Jr" }, { "family_name": "Navrotsky", "given_name": "Alexandra", "orcid": "0000-0002-3260-0364", "clpid": "Navrotsky-A" }, { "family_name": "Orlovskaya", "given_name": "Nina", "clpid": "Orlovskaya-N" }, { "family_name": "Pantano", "given_name": "Carlo", "clpid": "Pantano-C" }, { "family_name": "Stebbins", "given_name": "Jonathan F.", "clpid": "Stebbins-J-F" }, { "family_name": "Sudarshan", "given_name": "T. S.", "clpid": "Sudarshan-T-S" }, { "family_name": "Tani", "given_name": "Toshihiko", "clpid": "Tani-T" }, { "family_name": "Weil", "given_name": "K. Scott", "clpid": "Weil-K-S" } ], "abstract": "In March 2012, a group of researchers met to discuss emerging topics in ceramic science and to identify grand challenges in the field. By the end of the workshop, the group reached a consensus on eight challenges for the future:\u2014understanding rare events in ceramic microstructures, understanding the phase-like behavior of interfaces, predicting and controlling heterogeneous microstructures with unprecedented functionalities, controlling the properties of oxide electronics, understanding defects in the vicinity of interfaces, controlling ceramics far from equilibrium, accelerating the development of new ceramic materials, and harnessing order within disorder in glasses. This paper reports the outcomes of the workshop and provides descriptions of these challenges.", "doi": "10.1111/jace.12033", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2012-12", "series_number": "12", "volume": "95", "issue": "12", "pages": "3699-3712" }, { "id": "authors:vbjmk-7hw55", "collection": "authors", "collection_id": "vbjmk-7hw55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140710-115952819", "type": "article", "title": "Direct lamination of solid oxide fuel cell anode support, anode, and electrolyte by sequential tape casting of thermoreversible gel slips", "author": [ { "family_name": "Shanti", "given_name": "N. O.", "clpid": "Shanti-N-O" }, { "family_name": "Bierschenk", "given_name": "D. M.", "clpid": "Bierschenk-D-M" }, { "family_name": "Barnett", "given_name": "S. A.", "clpid": "Barnett-S-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A novel direct lamination technique by tape casting thermoreversible gel-based slips is introduced for the production of solid oxide fuel cell anode support, anode, and electrolyte layers. Production of cells with controlled layer thicknesses of \u223c10\u2013500 \u03bcm and having well formed and relatively high toughness interfaces is demonstrated. Cells with maximum current density of 1.76 A\u2022cm^(\u22122) and maximum power density 425 mW cm^(\u22122) were achieved using 97% H_2/3% H_2O fuel at 800 \u00b0C. Specific opportunities for further optimization of processing to improve electrochemical performance are highlighted.", "doi": "10.1016/j.jpowsour.2012.03.073", "issn": "0378-7753", "publisher": "Elsevier", "publication": "Journal of Power Sources", "publication_date": "2012-08-15", "volume": "212", "pages": "43-46" }, { "id": "authors:gwv0k-ana32", "collection": "authors", "collection_id": "gwv0k-ana32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-095356082", "type": "article", "title": "Liquid Desiccant Solvent Extraction of Alumina-Filled Thermoreversible Gels", "author": [ { "family_name": "Shanti", "given_name": "N. O.", "clpid": "Shanti-N-O" }, { "family_name": "DeNolf", "given_name": "G. C.", "clpid": "DeNolf-G-C" }, { "family_name": "Shull", "given_name": "K. R.", "clpid": "Shull-K-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A liquid desiccant solvent extraction technique is introduced to significantly reduce the amount of warping during drying in thermoreversibly gelcast alumina samples by eliminating capillary stresses during the initial solvent removal stage. This process is combined with a secondary drying step in a vacuum oven with an in-line solvent trap, allowing for the complete recovery of the alcohol solvent used in producing gels. Optimal concentrations and immersion times for poly(tert-butyl acrylate)-based and water-based liquid desiccants are determined, along with the osmotic stresses and equilibrium solvent concentrations of gels immersed in these desiccants. Solvent loss during the liquid desiccant solvent extraction step, volumetric shrinkage during drying and sintering, and sintered porosity are measured. It is determined that a ~10 wt% poly(tert-butyl acrylate)/90 wt% isopropyl alcohol liquid desiccant is optimal.", "doi": "10.1111/j.1551-2916.2011.04884.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2012-02", "series_number": "2", "volume": "95", "issue": "2", "pages": "509-514" }, { "id": "authors:51s5s-4tt98", "collection": "authors", "collection_id": "51s5s-4tt98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-140715363", "type": "book_section", "title": "Gelcasting of Ceramic Bodies", "book_title": "Ceramics and Composites Processing Methods", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Shanti", "given_name": "Noah O.", "clpid": "Shanti-N-O" } ], "contributor": [ { "family_name": "Bansal", "given_name": "Narottam P.", "clpid": "Bansal-N-P" }, { "family_name": "Boccaccini", "given_name": "Aldo R.", "clpid": "Boccaccini-A-R" } ], "abstract": "Net-shape and near-net-shape forming techniques have long been appealing in the\nproduction of ceramic materials. The high hardness and low toughness of ceramics\nmake post-densification machining both costly and time-consuming, providing strong\nincentive for the development and optimization of net-shape techniques. The oldest of\nthese forming techniques is slip casting. However, extrusion of cylindrical shapes, tape\ncasting of laminates, and gelcasting, freeze casting, and injection molding of complex\nshapes have received considerable attention. Selective laser sintering, where shapes are\ndetermined via a computer-controlled localized heating profile, and robocasting, where\nmaterial from a syringe or fine extruder is deposited in robotically controlled patterns,\nhave garnered more recent interest. Each of these techniques relies on the suspension\nof a ceramic powder in a liquid vehicle or binder system for the forming stage of the\noperation. The shaped component is solidified through drying, cooling, or gelling. Once\nresidual liquid is evaporated and binders are burned out, traditional densification\nmethods, such as sintering, are employed. \n\nTreated here is gelcasting, one of the more promising forming methods for complex-shaped\nceramic and powdered metal components. This method was patented by Janney and Omatete in the early 1990s and was explored in detail by them and their\ncoworkers at Oak Ridge National Laboratory. In their originally conceived\nmethod, a low-viscosity slurry is produced by mixing a ceramic powder into an aqueous-based\nmonomer solution, while Venkataswamy et al. used monomers that required\norganic solvents. The slurries have characteristically high solids loadings, often\ngreater than 50 vol %, but have sufficiently low viscosity to flow easily. Through the\naddition of a chemical initiator and, in some cases, a catalyst, polymerization commences,\nat which point the slurry should be cast. The chemically cross-linked network\nthat is formed through polymerization renders the ceramic powder particles immobile.\nThe filled gel conforming to the shape of the mold is rigid enough to be removed for\nfurther processing. The high water content makes a controlled drying process critical\nto prevent warping and cracking. Low binder concentrations (generally <5 wt %) can\nbe removed quickly and the body sintered. Sintering to full density is promoted by the\nhigh solids loading that can be achieved in gel-casting slurries. \n\nGelcasting should not be confused with sol-gel processing. In gelcasting, ceramic\n(or precursor) powders are suspended in a monomer or polymer solution to form slurries\nfor casting. The monomer/polymer solution gels without reacting with the suspended\npowder, in essence locking the particles in place; the same gel would form in\nthe absence of any ceramic. In sol-gel processing, ceramic precursors are integral to\nthe gel formation process (through hydrolysis, polycondensation, etc.) Metal alkoxides,\nhydroxides, and the like form the backbone of the gel network and are converted to\nceramic in later processing steps. \n\nIn this chapter, we first describe the categories of gel-casting systems and the\nchemistry of gelation in each type. Following this is a description of the processing\nsteps from gel preparation to densification. An account of the variety of structural\nclasses that are afforded by gelcasting is then presented. In addition to the processing\nof conventional bulk ceramics, gelcasting of textured ceramics, porous bodies,\nand laminates is described. Finally, gel-casting challenges and opportunities are\nhighlighted.", "doi": "10.1002/9781118176665.ch6", "isbn": "9780470553442", "publisher": "Wiley", "place_of_publication": "Hoboken, NJ", "publication_date": "2012", "pages": "199-234" }, { "id": "authors:k1ydp-1e933", "collection": "authors", "collection_id": "k1ydp-1e933", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181320055", "type": "article", "title": "Chemical and Mechanical Consequences of Environmental Barrier Coating Exposure to Calcium-Magnesium-Aluminosilicate", "author": [ { "family_name": "Harder", "given_name": "Bryan J.", "clpid": "Harder-B-J" }, { "family_name": "Ram\u00edrez-Rico", "given_name": "Joaquin", "clpid": "Ram\u00edrez-Rico-J" }, { "family_name": "Almer", "given_name": "Jonathan D.", "clpid": "Almer-J-D" }, { "family_name": "Lee", "given_name": "Kang N.", "clpid": "Lee-K-N" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The success of Si-based ceramics as high-temperature structural materials for gas turbine applications relies on the use of environmental barrier coatings (EBCs) with low silica activity, such as Ba_(1\u2212x)Sr_xAl_2Si_2O_8 (BSAS), which protect the underlying components from oxidation and corrosion in combustion environments containing water vapor. One of the current challenges concerning EBC lifetime is the effect of sandy deposits of calcium\u2013magnesium\u2013aluminosilicate (CMAS) glass that melt during engine operation and react with the EBC, changing both its composition and stress state. In this work, we study the effect of CMAS exposure at 1300\u00b0C on the residual stress state and composition in BSAS\u2013mullite\u2013Si\u2013SiC multilayers. Residual stresses were measured in BSAS multilayers exposed to CMAS for different times using high-energy X-ray diffraction. Their microstructure was studied using a combination of scanning electron microscopy and transmission electron microscopy techniques. Our results show that CMAS dissolves the BSAS topcoat preferentially through the grain boundaries, dislodging the grains and changing the residual stress state in the topcoat to a nonuniform and increasingly compressive stress state with increasing exposure time. The presence of CMAS accelerates the hexacelsian-to-celsian phase transformation kinetics in BSAS, which reacts with the glass by a solution\u2013reprecipitation mechanism. Precipitates have crystallographic structures consistent with Ca-doped celsian and Ba-doped anorthite.", "doi": "10.1111/j.1551-2916.2011.04448.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2011-06", "series_number": "S1", "volume": "94", "issue": "S1", "pages": "S178-S185" }, { "id": "authors:3b764-tyk63", "collection": "authors", "collection_id": "3b764-tyk63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-101550186", "type": "article", "title": "Catalytic graphitization of three-dimensional wood-derived porous scaffolds", "author": [ { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A catalytic technique to enhance graphite formation in nongraphitizing carbons was adapted to work with three-dimensional wood-derived scaffolds. Unlike many synthetic graphite precursors, wood and other cellulosic carbons remain largely disordered after high temperature pyrolysis. Using a nickel nitrate liquid catalyst and controlled pyrolysis conditions, wood-derived scaffolds were produced showing similar graphitic content to traditional pitch-based graphite while retaining the high-aspect ratio pores of the precursor wood microstructure. Graphite formation was studied as a function of processing time and pyrolysis temperature, and the resulting carbons were analyzed using x-ray diffraction, Raman spectroscopy, x-ray photoelectron spectroscopy, and electron microscopy techniques.", "doi": "10.1557/jmr.2010.88", "issn": "0884-2914", "publisher": "Cambridge University Press", "publication": "Journal of Materials Research", "publication_date": "2011-01", "series_number": "1", "volume": "26", "issue": "1", "pages": "18-25" }, { "id": "authors:r3ayz-wnp19", "collection": "authors", "collection_id": "r3ayz-wnp19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140912-093131896", "type": "conference_item", "title": "Stresses in Ytterbium Silicate Multilayer Environmental Barrier Coatings", "author": [ { "family_name": "Stolzenburg", "given_name": "F.", "clpid": "Stolzenburg-F" }, { "family_name": "Almer", "given_name": "J.", "clpid": "Almer-J-D" }, { "family_name": "Lee", "given_name": "K. N.", "clpid": "Lee-K-N" }, { "family_name": "Harder", "given_name": "B. J.", "clpid": "Harder-B-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The internal stresses of plasma-sprayed multilayer ytterbium disilicate environmental barrier\ncoatings were measured using microfocused high-energy X-rays in a transmission geometry.\nStresses were measured for as-sprayed and ex-situ heat-treated ytterbium disilicate topcoats at\nroom temperature and during in-situ heating and cooling experiments. In-situ loading\nexperiments were also performed on the topcoat in order to establish its elastic constants. The\nytterbium disilicate was found to have a relatively low coefficient of thermal expansion resulting\nin compressive stresses of approximately 100 MPa throughout the topcoat. In-situ heating\nexperiments revealed a statistically significant stress relaxation in the ytterbium disilicate topcoat\nupon thermal cycling to temperatures above 1300\u00b0C, indicating the onset of stress relaxation but\nno cracks were observed in SEM micrographs. The stress states were also modeled using a\nnumerical solution; measured stresses were found to be very close to the predicted stresses in\nytterbium dilisicate topcoats, while the experimentally determined stresses in the intermediate\nlayers were of much smaller magnitude than the calculated stresses.", "publisher": "Caltech Library", "publication_date": "2011" }, { "id": "authors:64khm-b3r04", "collection": "authors", "collection_id": "64khm-b3r04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140711-155202875", "type": "article", "title": "A hierarchical study of the mechanical properties of gypsum", "author": [ { "family_name": "Chen", "given_name": "Z.", "clpid": "Chen-Z" }, { "family_name": "Sucech", "given_name": "S.", "clpid": "Sucech-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The flexural strength of gypsum is reported for freestanding single crystals in three-point bending carried with a nanoindenter. The elastic modulus, splitting tensile strength, and fracture toughness of monolithic gypsum consisting of interlocking needle-like microcrystals are also reported as functions of porosity and accelerator addition. This study shows that geometric configurations, in addition to porosity, affect the mechanical properties of gypsum. The properties are improved by 50\u2013100% when the crystal network changes from needle aggregates to one made up of homogeneous randomly oriented single crystals. An Ashby geometric model for open-cell foams is adopted to link the properties of the individual crystals and the bulk properties. The lower and upper bounds of the measured elastic modulus are in accordance with bending-dominated behavior and stretch-dominated behavior predicted by the model, respectively. However, the strength of gypsum is much lower than values predicted by the model, which is based failure on fracture of individual crystals, suggesting that the strength of monolithic gypsum may be instead controlled by the failure of weak intercrystalline contacts.", "doi": "10.1007/s10853-010-4527-z", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "2010-08", "series_number": "16", "volume": "45", "issue": "16", "pages": "4444-4453" }, { "id": "authors:z0cpm-c9g88", "collection": "authors", "collection_id": "z0cpm-c9g88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-080530348", "type": "article", "title": "Thermal conductivity of the pine-biocarbon-preform/copper composite", "author": [ { "family_name": "Parfen'eva", "given_name": "L. S.", "clpid": "Parfen'eva-L-S" }, { "family_name": "Orlova", "given_name": "T. S.", "clpid": "Orlova-T-S" }, { "family_name": "Smirnov", "given_name": "B. I.", "clpid": "Smirnov-B-I" }, { "family_name": "Smirnov", "given_name": "I. A.", "clpid": "Smirnov-I-A" }, { "family_name": "Misiorek", "given_name": "H.", "clpid": "Misiorek-H" }, { "family_name": "Jezowski", "given_name": "A.", "clpid": "Jezowski-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The thermal conductivity of composites of a new type prepared by infiltration under vacuum of melted copper into empty sap channels (aligned with the sample length) of high-porosity biocarbon preforms of white pine tree wood has been studied in the temperature range 5\u2013300 K. The biocarbon preforms have been prepared by pyrolysis of tree wood in an argon flow at two carbonization temperatures of 1000 and 2400\u00b0C. From the experimental values of the composite thermal conductivities, the fraction due to the thermal conductivity of the embedded copper is isolated and found to be substantially lower than that of the original copper used in preparation of the composites. The decrease in the thermal conductivity of copper in the composite is assigned to defects in its structure, namely, breaks in the copper filling the sap channels, as well as the radial ones, also filled by copper. A possibility of decreasing the thermal conductivity of copper in a composite due to its doping by the impurities present in the carbon preform is discussed.", "doi": "10.1134/S1063783410070048", "issn": "1063-7834", "publisher": "Springer", "publication": "Physics of the Solid State", "publication_date": "2010-07", "series_number": "7", "volume": "52", "issue": "7", "pages": "1348-1355" }, { "id": "authors:w7jbg-jb526", "collection": "authors", "collection_id": "w7jbg-jb526", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140716-074513492", "type": "article", "title": "Thermal conductivity of high-porosity biocarbon preforms of beech wood", "author": [ { "family_name": "Parfen'eva", "given_name": "L. S.", "clpid": "Parfen'eva-L-S" }, { "family_name": "Orlova", "given_name": "T. S.", "clpid": "Orlova-T-S" }, { "family_name": "Kartenko", "given_name": "N. F.", "clpid": "Kartenko-N-F" }, { "family_name": "Sharenkova", "given_name": "N. V.", "clpid": "Sharenkova-N-V" }, { "family_name": "Smirnov", "given_name": "B. I.", "clpid": "Smirnov-B-I" }, { "family_name": "Smirnov", "given_name": "I. A.", "clpid": "Smirnov-I-A" }, { "family_name": "Misiorek", "given_name": "H.", "clpid": "Misiorek-H" }, { "family_name": "Jezowski", "given_name": "A.", "clpid": "Jezowski-A" }, { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "This paper reports on measurements performed in the temperature range 5\u2013300 K for the thermal\nconductivity \u03ba and electrical resistivity \u03c1 of high-porosity (cellular pores) biocarbon preforms prepared by\npyrolysis (carbonization) of beech wood in an argon flow at carbonization temperatures of 1000 and 2400\u00b0C.\nX-ray structure analysis of the samples has been performed at 300 K. The samples have revealed the presence\nof nanocrystallites making up the carbon matrices of these biocarbon preforms. Their size has been determined. For samples prepared at T_(carb) = 1000 and 2400\u00b0C, the nanocrystallite sizes are found to be in the\nranges 12\u201325 and 28\u201360 \u00c5, respectively. The dependences \u03ba(T) are determined for the samples cut along and\nacross the tree growth direction. The thermal conductivity \u03ba increases with increasing carbonization temperature and nanocrystallite size in the carbon matrix of the sample. Thermal conductivity measurements conducted on samples of both types have revealed an unusual temperature dependence of the phonon thermal\nconductivity for amorphous materials. As the temperature increases from 5 to 300 K, it first increases in proportion to T, to transfer subsequently to ~T^(1.5) scaling. The results obtained are analyzed.", "doi": "10.1134/S1063783410060028", "issn": "1063-7834", "publisher": "Springer", "publication": "Physics of the Solid State", "publication_date": "2010-06", "series_number": "6", "volume": "52", "issue": "6", "pages": "1115-1122" }, { "id": "authors:mgwf5-aqa43", "collection": "authors", "collection_id": "mgwf5-aqa43", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-090151860", "type": "article", "title": "Thermal properties of wood-derived copper\u2013silicon carbide composites fabricated via electrodeposition", "author": [ { "family_name": "Pappacena", "given_name": "K. E.", "clpid": "Pappacena-K-E" }, { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Wang", "given_name": "H.", "clpid": "Wang-H" }, { "family_name": "Porter", "given_name": "W. D.", "clpid": "Porter-W-D" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Copper\u2013silicon carbide composites were fabricated by electrodeposition of copper into pores of wood-derived silicon carbide, a ceramic with a microstructure that can be tailored via the use of different wood precursors. Thermal conductivity values were determined using flash diffusivity at temperatures from 0 to 900 \u00b0C. Thermal conductivities of up to 202 W/mK at 0 \u00b0C and 148W/mK at 900 \u00b0C were achieved. Object-oriented finite-element analysis (OOF) modeling was used to understand the heat flux distributions throughout the microstructures. OOF was also used to calculate the effective thermal conductivity, which correlated well with experimentally-determined values for axially-oriented composites. In addition, OOF was used to predict effective conductivity values and heat flux distributions for transversely-oriented composites.", "doi": "10.1016/j.compscitech.2009.11.011", "issn": "0266-3538", "publisher": "Elsevier", "publication": "Composites Science and Technology", "publication_date": "2010-03", "series_number": "3", "volume": "70", "issue": "3", "pages": "478-484" }, { "id": "authors:15esq-2xf75", "collection": "authors", "collection_id": "15esq-2xf75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-091939378", "type": "article", "title": "Transformation kinetics in plasma-sprayed barium- and strontium-doped aluminosilicate (BSAS)", "author": [ { "family_name": "Harder", "given_name": "B. J.", "clpid": "Harder-B-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The hexacelsian-to-celsian phase transformation in Ba_(1\u2013x)Sr_xAl_2Si_2O_8 is of interest for environmental barrier coating applications. Plasma-sprayed microstructures were heat treated above 1100 \u00b0C and the kinetics of the hexacelsian-to-celsian transformation were quantified. Activation energies for bulk and crushed materials were determined to be \u223c340 and \u223c500 kJ mol^(\u22121), respectively. X-ray diffraction and electron backscattered diffraction were used to establish how plasma spraying barium- and strontium-doped aluminosilicate effectively reduces the energy required for its transformation.", "doi": "10.1016/j.scriptamat.2009.11.019", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2010-03", "series_number": "5", "volume": "62", "issue": "5", "pages": "282-285" }, { "id": "authors:19b9q-a5032", "collection": "authors", "collection_id": "19b9q-a5032", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-133958799", "type": "article", "title": "Processing of wood-derived copper\u2013silicon carbide composites via electrodeposition", "author": [ { "family_name": "Pappacena", "given_name": "K. E.", "clpid": "Pappacena-K-E" }, { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Xie", "given_name": "S.", "clpid": "Xie-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "An electrodeposition technique has been adapted to produce copper\u2013silicon carbide composites with honeycomb-like microstructures. The detrimental Cu\u2013SiC reaction was avoided by using this room temperature processing technique. The wood-derived silicon carbide phase allows for tailorable microstructures due to the variety of available wood precursors. Plating efficiency for each wood type was determined using image analysis. This processing method results in the successful filling of pores with aspect ratios of up to 100.", "doi": "10.1016/j.compscitech.2009.12.019", "issn": "0266-3538", "publisher": "Elsevier", "publication": "Composites Science and Technology", "publication_date": "2010-03", "series_number": "3", "volume": "70", "issue": "3", "pages": "485-491" }, { "id": "authors:zxe4r-1t974", "collection": "authors", "collection_id": "zxe4r-1t974", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-090311535", "type": "article", "title": "Through-thickness determination of phase composition and residual stresses in thermal barrier coatings using high-energy X-rays", "author": [ { "family_name": "Weyant", "given_name": "C. M.", "clpid": "Weyant-C-M" }, { "family_name": "Almer", "given_name": "J.", "clpid": "Almer-J-D" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "High-energy X-rays were used to determine the local phase composition and residual stresses through the thickness of as-sprayed and heat-treated plasma-sprayed thermal barrier coatings consisting of a NiCoCrAlY bond coat and an yttria-stabilized zirconia (YSZ) topcoat produced with through-thickness segmentation cracks. The as-sprayed residual stresses reflected the combined influence of quenching stresses from the plasma spray process, thermal expansion mismatch between the topcoat, bond coat and substrate, and stress relief from the segmentation cracks. Heat treatments led to the formation of a thermally grown oxide (TGO) which was in compression in the plane, as well as relief of quenching stresses and development of a stress gradient in the YSZ topcoat. The high-energy X-ray technique used in this study revealed the effects that TGO and segmentation cracks have on the in-plane stress state of the entire coating.", "doi": "10.1016/j.actamat.2009.10.010", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2010-02", "series_number": "3", "volume": "58", "issue": "3", "pages": "943-951" }, { "id": "authors:czq33-qdz73", "collection": "authors", "collection_id": "czq33-qdz73", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140709-153150670", "type": "article", "title": "Load partitioning in honeycomb-like silicon carbide aluminum alloy composites", "author": [ { "family_name": "Wilkes", "given_name": "T.E.", "clpid": "Wilkes-T-E" }, { "family_name": "Harder", "given_name": "B.J.", "clpid": "Harder-B-J" }, { "family_name": "Almer", "given_name": "J.D.", "clpid": "Almer-J-D" }, { "family_name": "Faber", "given_name": "K.T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A 50/50 vol.% Al/SiC composite was made via melt infiltration of an aluminum alloy into a porous beech wood-derived SiC preform. The honeycomb-like composite microstructure consisted of an interconnected SiC phase surrounding discrete Al \"fibers\" aligned in the growth direction of the beech wood. High energy synchrotron X-ray diffraction was used to measure the volume averaged lattice strains in both the SiC and Al phases during in situ compressive loading up to an applied stress of \u2212530 MPa. Load transfer from the Al to the SiC was observed, and the Al yielded at an applied stress of above \u2212213 MPa. The elastic behavior of the composite was modeled with both an isostrain rule of mixtures calculation and variational bounds for the effective elastic modulus. Furthermore, calculations of the von Mises effective stress of the SiC and Al phases showed that the wood-derived SiC was a more effective reinforcement than either SiC particle- or whisker-reinforced composites.", "doi": "10.1016/j.actamat.2009.08.050", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2009-12", "series_number": "20", "volume": "57", "issue": "20", "pages": "6234-6242" }, { "id": "authors:xfmps-9gn12", "collection": "authors", "collection_id": "xfmps-9gn12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140716-082758115", "type": "article", "title": "Young's modulus and internal friction in porous biocarbon white pine wood precursors", "author": [ { "family_name": "Kardashev", "given_name": "B. K.", "clpid": "Kardashev-B-K" }, { "family_name": "Orlova", "given_name": "T. S.", "clpid": "Orlova-T-S" }, { "family_name": "Smirnov", "given_name": "B. I.", "clpid": "Smirnov-B-I" }, { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "This paper reports on a study performed in the temperature range 100\u2013293 K, in air and in vacuum, for the amplitude and time dependences of the Young's modulus and the internal friction (ultrasound damping) of biocarbon precursors prepared from white pine wood at two pyrolysis (carbonization) temperatures of 1000 and 2400\u00b0C. The measurements have been conducted by the resonance technique with a composite vibrator on samples cut along and across the tree growth direction. The desorption of molecules of the external medium at low amplitudes of ultrasonic vibrations has been found to produce the pronounced influence on the effective elastic modulus and elastic vibration decrement. The data obtained from acoustic measurements of the amplitude dependences of the elastic modulus have been used to estimate the microplastic properties of the samples. It has been shown that increasing the carbonization temperature gives rise to noticeable changes in the Young's modulus and internal friction, as well as to reduction of the microplastic stress \u03c3 y of the biomaterial studied. The stress \u03c3_y of the samples cut across the growth direction has been found to be substantially smaller than that of the \"longitudinal\" samples. The elastic and microplastic properties of precursors prepared from white pine wood have been compared with those of the white eucalyptus wood.", "doi": "10.1134/S1063783409120063", "issn": "1063-7834", "publisher": "Springer", "publication": "Physics of the Solid State", "publication_date": "2009-12", "series_number": "12", "volume": "51", "issue": "12", "pages": "2463-2468" }, { "id": "authors:f2zym-q9f75", "collection": "authors", "collection_id": "f2zym-q9f75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140710-091155715", "type": "article", "title": "Effect of pyrolyzation temperature on wood-derived carbon and silicon carbide", "author": [ { "family_name": "Pappacena", "given_name": "K. E.", "clpid": "Pappacena-K-E" }, { "family_name": "Gentry", "given_name": "S. P.", "clpid": "Gentry-S-P" }, { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Johnson", "given_name": "M. T.", "orcid": "0000-0002-3710-1070", "clpid": "Johnson-M-T" }, { "family_name": "Xie", "given_name": "S.", "clpid": "Xie-S" }, { "family_name": "Davis", "given_name": "A.", "clpid": "Davis-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The structure of carbon and silicon carbide produced through the pyrolyzation of wood and the subsequent melt-infiltration with silicon was studied as a function of initial carbon pyrolyzation temperature. Scanning electron microscopy, transmission electron microscopy, mercury intrusion porosimetry, X-ray diffraction and Raman spectroscopy were used to characterize material derived from initial carbon pyrolyzation temperatures in the range of 300\u20132400 \u00b0C. It was determined that, although structural differences abound in carbon pyrolyzed at different temperatures, the resulting silicon carbide is independent of the initial temperature of carbon pyrolyzation.", "doi": "10.1016/j.jeurceramsoc.2009.04.040", "issn": "0955-2219", "publisher": "Elsevier", "publication": "Journal of the European Ceramic Society", "publication_date": "2009-11", "series_number": "14", "volume": "29", "issue": "14", "pages": "3069-3077" }, { "id": "authors:sdm56-4pe98", "collection": "authors", "collection_id": "sdm56-4pe98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-160552994", "type": "article", "title": "Heat Capacity of the White Pine Biocarbon Preform and the Related Biocarbon/Copper Composite", "author": [ { "family_name": "Smirnov", "given_name": "I. A.", "clpid": "Smirnov-I-A" }, { "family_name": "Orlova", "given_name": "T. S.", "clpid": "Orlova-T-S" }, { "family_name": "Smirnov", "given_name": "B. I.", "clpid": "Smirnov-B-I" }, { "family_name": "Wlosewicz", "given_name": "D. W.", "clpid": "Wlosewicz-D-W" }, { "family_name": "Misiorek", "given_name": "H.", "clpid": "Misiorek-H" }, { "family_name": "Jezowski", "given_name": "A.", "clpid": "Jezowski-A" }, { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "This paper reports on measurements in the 80\u2013300-K temperature interval of the heat capacity at constant pressure C_(p)(T) of high-porosity amorphous white pine carbon preforms (biocarbon) prepared by pyrolysis (carbonization) at T_(carb) = 1000 and 2400\u00b0C in an argon flow. The dependences C_(p)(T) for biocarbon/copper composites based on the carbon preforms obtained have also been determined. It is shown that the mixture rule holds for the composites, i.e., that C_(p)(T) of the composite is a sum of the heat capacities of the constituent materials taken in the corresponding ratios. Phonon mean free paths for the white pine carbon preforms prepared at T_(carb) = 1000 and 2400\u00b0C have been calculated and used to estimate the size of the nanocrystallites contributing to formation of the carbon frameworks of these preforms.", "doi": "10.1134/S1063783409110110", "issn": "1063-7834", "publisher": "Springer", "publication": "Physics of the Solid State", "publication_date": "2009-11", "series_number": "11", "volume": "51", "issue": "11", "pages": "2264-2268" }, { "id": "authors:krs1c-9mn53", "collection": "authors", "collection_id": "krs1c-9mn53", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181320153", "type": "article", "title": "Ceramic Laminates by Gelcasting", "author": [ { "family_name": "Shanti", "given_name": "Noah O.", "clpid": "Shanti-N-O" }, { "family_name": "Hovis", "given_name": "David B.", "clpid": "Hovis-D-B" }, { "family_name": "Seitz", "given_name": "Michelle E.", "clpid": "Seitz-M-E" }, { "family_name": "Montgomery", "given_name": "John K.", "clpid": "Montgomery-J-K" }, { "family_name": "Baskin", "given_name": "Donald M.", "clpid": "Baskin-D-M" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Laminated ceramic composites are appealing for many applications due to their unique and customizable thermal and mechanical properties. Gelcasting is a relatively new, yet commercially proven, near-net-shape processing technique suitable for laminate production. A review of gelcasting techniques and a discussion of their application to laminate processing are provided, along with an overview of laminate design and processing concerns. Specific examples of single-phase laminates produced via gelcasting are provided, including porous/dense alumina and magnetically aligned iron titanate and barium hexaferrite structures.", "doi": "10.1111/j.1744-7402.2008.02312.x", "issn": "1744-7402", "publisher": "Wiley", "publication": "International Journal of Applied Ceramic Technology", "publication_date": "2009-09", "series_number": "5", "volume": "6", "issue": "5", "pages": "593-606" }, { "id": "authors:s59w4-wh816", "collection": "authors", "collection_id": "s59w4-wh816", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-095003520", "type": "article", "title": "Acrylic Triblock Copolymer Design for Thermoreversible Gelcasting of Ceramics: Rheological and Green Body Properties", "author": [ { "family_name": "Seitz", "given_name": "M. E.", "clpid": "Seitz-M-E" }, { "family_name": "Shull", "given_name": "K. R.", "clpid": "Shull-K-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Thermoreversible gelcasting (TRG) is an attractive net-shape powder-based processing technique which relies on the temperature-driven gelation of a polymer solution. This study uses the TRG of alumina to investigate the implications of triblock copolymer design (block length, endblock fraction, and midblock chemistry) on rheological and green body properties. The liquid-to-solid transition and relaxation time in the gel state are controlled by the polymer's endblock length while the total polymer length controls the viscosity at high temperature. Although triblock design and concentration do not affect the green body porosity or sintered density, they do have significant effects on green body behavior. Triblocks with a high fraction of rubbery midblock behave as elastomers and confer significant toughness to the green bodies. In contrast, those with glassy midblocks increase the strength of the body but also behave in a brittle manner. Green body strength increases with increasing triblock concentration and is well described by a model for the strength of ceramic bodies with the binder localized at the particle necks.", "doi": "10.1111/j.1551-2916.2009.03059.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2009-07", "series_number": "7", "volume": "92", "issue": "7", "pages": "1519-1525" }, { "id": "authors:e4eqs-ny431", "collection": "authors", "collection_id": "e4eqs-ny431", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-133753969", "type": "article", "title": "X-ray micro-computed tomography of beech wood and biomorphic C, SiC and Al/SiC composites", "author": [ { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Stock", "given_name": "S. R.", "clpid": "Stock-S-R" }, { "family_name": "De Carlo", "given_name": "F.", "clpid": "De-Carlo-F" }, { "family_name": "Xiao", "given_name": "X.", "clpid": "Xiao-X" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The microstructures of beech wood and of beech wood-derived carbon, silicon carbide (SiC), and an aluminum/SiC composite were studied using both scanning electron microscopy (SEM) and synchrotron X-ray micro-computed tomography (\u00b5CT). As opposed to traditional two-dimensional imaging techniques, the \u00b5CT data allowed nondestructive evaluation of relatively large sample volumes. Nondestructive three-dimensional data analysis led to the observation of microstructural features, such as varying pore-wall topographies not previously seen in SEM, calculations of the volume fraction of porosity and characterization of the interconnectivity of porosity in the SiC material.", "doi": "10.1080/14786430902956457", "issn": "1478-6435", "publisher": "Taylor & Francis", "publication": "Philosophical Magazine", "publication_date": "2009-06-11", "series_number": "17", "volume": "89", "issue": "17", "pages": "1373-1389" }, { "id": "authors:gnmrk-fyg14", "collection": "authors", "collection_id": "gnmrk-fyg14", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-161429351", "type": "article", "title": "In situ stress analysis of multilayer environmental barrier coatings", "author": [ { "family_name": "Harder", "given_name": "B. J.", "clpid": "Harder-B-J" }, { "family_name": "Almer", "given_name": "J. D.", "clpid": "Almer-J-D" }, { "family_name": "Lee", "given_name": "K. N.", "clpid": "Lee-K-N" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The biaxial stress and thermal expansion of multilayer doped-aluminosilicate environmental barrier coatings were measured in situ during cooling using microfocused high-energy X-rays in transmission. Coating stresses during cooling from 1000 \u00b0C were measured for as-sprayed and thermally cycled samples. In the as-sprayed state, tensile stresses as high as 75 MPa were measured in the doped-aluminosilicate topcoat at 375 \u00b0C, after which a drop in the stress occurred accompanied by through-thickness cracking of the two outermost layers. After thermally cycling the samples, the stress in the topcoat was reduced to approximately 50 MPa, and there was no drop in stress upon cooling. This stress reduction was attributed to a crystallographic phase transformation of the topcoat and the accompanying change in thermal expansion coefficient. The addition of a doped aluminosilicate to the mullite layer did not lower the stress in the topcoat, but may offer increased durability due to an increased compressive stress.", "doi": "10.1154/1.3120602", "issn": "0885-7156", "publisher": "Cambridge University Press", "publication": "Powder Diffraction", "publication_date": "2009-06", "series_number": "2", "volume": "24", "issue": "2", "pages": "94-98" }, { "id": "authors:sfd64-8t876", "collection": "authors", "collection_id": "sfd64-8t876", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-110117925", "type": "article", "title": "Residual Stress Analysis of Multilayer Environmental Barrier Coatings", "author": [ { "family_name": "Harder", "given_name": "B. J.", "clpid": "Harder-B-J" }, { "family_name": "Almer", "given_name": "J. D.", "clpid": "Almer-J-D" }, { "family_name": "Weyant", "given_name": "C. M.", "clpid": "Weyant-C-M" }, { "family_name": "Lee", "given_name": "K. N.", "clpid": "Lee-K-N" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Silicon-based ceramics (SiC, Si_3N_4) are promising materials systems for high-temperature structural applications in gas turbine engines. However, the silica layer that forms on these materials is susceptible to attack from water vapor present in combustion environments. To protect against this degradation, environmental barrier coatings (EBCs) have been developed to shield the underlying substrate and prevent degradation. Here we report on elastic and thermal properties, as well as internal stresses of candidate multilayer coatings, as measured in situ using microfocused high-energy X-rays in a transmission diffraction geometry. Doped aluminosilicate coatings were investigated for their stability on a SiC/SiC melt-infiltrated substrate. The coatings consisted of a Ba_(1\u2212x)Sr_xAl_2Si_2O_8 topcoat with a mullite or mullite+SrAl_2Si_2O_8 interlayer, and a silicon bond coat. A numerical model was used to compare the stress results with an ideal coating system. Experiments were carried out on as-sprayed and heat-treated samples in order to analyze the strain and phase evolution as a function of multilayer depth and temperature. The phase transformation of the topcoat promoted healing of cracks in the EBC and reduced stresses in the underlying layers and the addition of SAS to the interlayer reduced stresses in thermally cycled coatings, but did not stop cracks from forming.", "doi": "10.1111/j.1551-2916.2008.02888.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2009-02", "series_number": "2", "volume": "92", "issue": "2", "pages": "452-459" }, { "id": "authors:m3apz-3ek09", "collection": "authors", "collection_id": "m3apz-3ek09", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140716-083406553", "type": "article", "title": "Thermal conductivity of high-porosity biocarbon precursors of white pine wood", "author": [ { "family_name": "Parfen'eva", "given_name": "L. S.", "clpid": "Parfen'eva-L-S" }, { "family_name": "Orlova", "given_name": "T. S.", "clpid": "Orlova-T-S" }, { "family_name": "Kartenko", "given_name": "N. F.", "clpid": "Kartenko-N-F" }, { "family_name": "Sharenkova", "given_name": "N. V.", "clpid": "Sharenkova-N-V" }, { "family_name": "Smirnov", "given_name": "B. I.", "clpid": "Smirnov-B-I" }, { "family_name": "Smirnov", "given_name": "I. A.", "clpid": "Smirnov-I-A" }, { "family_name": "Misiorek", "given_name": "H.", "clpid": "Misiorek-H" }, { "family_name": "Jezowski", "given_name": "A.", "clpid": "Jezowski-A" }, { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "This paper reports on measurements of the thermal conductivity \u03ba and the electrical conductivity \u03c3 of high-porosity (cellular pores) biocarbon precursors of white pine tree wood in the temperature range 5\u2013300 K, which were prepared by pyrolysis of the wood at carbonization temperatures (T_(carb)) of 1000 and 2400\u00b0C. The x-ray structural analysis has permitted the determination of the sizes of the nanocrystallites contained in the carbon framework of the biocarbon precursors. The sizes of the nanocrystallites revealed in the samples prepared at T_(carb) = 1000 and 2400\u00b0C are within the ranges 12\u201335 and 25\u201370 \u00c5, respectively. The dependences \u03ba(T) and \u03c3(T) are obtained for samples cut along the tree growth direction. As follows from \u03c3(T) measurements, the biocarbon precursors studied are semiconducting. The values of \u03ba and \u03c3 increase with increasing carbonization temperature of the samples. Thermal conductivity measurements have revealed that samples of both types exhibit a temperature dependence of the phonon thermal conductivity \u03ba_(ph), which is not typical of amorphous (and amorphous to x-rays) materials. As the temperature increases, \u03ba_(ph) first varies proportional to T, to scale subsequently as \u223cT ^(1.7). The results obtained are analyzed.", "doi": "10.1134/S1063783408120032", "issn": "1063-7834", "publisher": "Springer", "publication": "Physics of the Solid State", "publication_date": "2008-12", "series_number": "12", "volume": "50", "issue": "12", "pages": "2245-2255" }, { "id": "authors:cjzr7-g0w48", "collection": "authors", "collection_id": "cjzr7-g0w48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-125752610", "type": "article", "title": "Elasticity and inelasticity of the SiC/Al-13Si-9Mg biomorphic metal ceramics", "author": [ { "family_name": "Kardashev", "given_name": "B. K.", "clpid": "Kardashev-B-K" }, { "family_name": "Orlova", "given_name": "T. S.", "clpid": "Orlova-T-S" }, { "family_name": "Smirnov", "given_name": "B. I.", "clpid": "Smirnov-B-I" }, { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The acoustic investigations of the elastic (Young's modulus) and microplastic properties of a composite material, the SiC/Al-13Si-9Mg biomorphic metal ceramic, were performed. The ceramic was prepared by infiltration of the Al-13Si-9Mg melt into porous silicon carbide derived from wood of two species of trees, beech and sapele. The measurements were performed with a composite piezoelectric vibrator under resonance conditions, with rod-shaped samples vibrated longitudinally at about 100 kHz over a wide range of vibrational strain amplitudes, which included both the linear (amplitude-independent) and nonlinear (microplastic) regions. It was shown that the Young's modulus and the microplastic properties of the composite are anisotropic and depend substantially on the tree species, particularly when longitudinal vibrations are excited in samples cut along the tree fibers.", "doi": "10.1134/S1063783408100168", "issn": "1063-7834", "publisher": "Springer", "publication": "Physics of the Solid State", "publication_date": "2008-10", "series_number": "10", "volume": "50", "issue": "10", "pages": "1882-1887" }, { "id": "authors:gegdq-ypp96", "collection": "authors", "collection_id": "gegdq-ypp96", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-103529474", "type": "article", "title": "Processing\u2013microstructure relationships for plasma-sprayed yttrium aluminum garnet", "author": [ { "family_name": "Weyant", "given_name": "C. M.", "clpid": "Weyant-C-M" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Plasma-sprayed yttrium aluminum garnet (YAG) has been considered as a component in a thermal barrier coating system to reduce oxidation of the bond coat by impeding oxygen diffusion through the coating. For this application, a fully crystalline, dense YAG coating would be advantageous to maximize lifetime and minimize oxygen diffusion. The effects of nine processing variables on the porosity and percent crystallinity in plasma-sprayed YAG were determined. Two powder types were investigated to compare a commercial, off-the-shelf, fused-and-crushed powder to a specially-processed, spherical plasma-spray powder. The resultant models suggest that plasma torch power and spray distance had the largest effect on the responses. It was determined that the processing parameters that lead to a coating with low porosity produce a coating with low crystallinity and vice versa. A possible route to producing a dense, crystalline coating was explored where a dense, amorphous coating was subsequently heat treated to produce crystalline material that retained the microstructure of the as-sprayed YAG in the bulk of the coating. However, macrocracking in the system due to thermal mismatch and crystallization stresses would need to be addressed for a viable multilayer TBC.", "doi": "10.1016/j.surfcoat.2008.07.008", "issn": "0257-8972", "publisher": "Elsevier", "publication": "Surface and Coatings Technology", "publication_date": "2008-08-15", "series_number": "24", "volume": "202", "issue": "24", "pages": "6081-6089" }, { "id": "authors:j2s5v-0cn21", "collection": "authors", "collection_id": "j2s5v-0cn21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-095121590", "type": "article", "title": "Mechanical properties of wood-derived silicon carbide aluminum-alloy composites as a function of temperature", "author": [ { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Pastor", "given_name": "J. Y.", "clpid": "Pastor-J-Y" }, { "family_name": "Llorca", "given_name": "J.", "clpid": "Llorca-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The mechanical behavior [i.e., stiffness, strength, and toughness (K_(IC))] of SiC Al\u2013Si\u2013Mg metal\u2013ceramic composites (50:50 by volume) was studied at temperatures ranging from 25 to 500 \u00b0C. The SiC phase was derived from wood precursors, which resulted in an interconnected anisotropic ceramic that constrained the pressure melt-infiltrated aluminum alloy. The composites were made using SiC derived from two woods (sapele and beech) and were studied in three orthogonal orientations. The mechanical properties and corresponding deformation micromechanisms were different in the longitudinal (LO) and transverse directions, but the influence of the precursor wood was small. The LO behavior was controlled by the rigid SiC preform and the load transfer from the metal to the ceramic. Moduli in this orientation were lower than the Halpin\u2013Tsai predictions due to the nonlinear and nonparallel nature of the Al-filled pores. The LO K_(IC) agreed with the Ashby model for the K_(IC) contribution of ductile inclusions in a brittle ceramic.", "doi": "10.1557/JMR.2008.0197", "issn": "0884-2914", "publisher": "Cambridge University Press", "publication": "Journal of Materials Research", "publication_date": "2008-06", "series_number": "6", "volume": "23", "issue": "6", "pages": "1732-1743" }, { "id": "authors:mg6qy-h2r17", "collection": "authors", "collection_id": "mg6qy-h2r17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-093532513", "type": "article", "title": "Nanoindentation analysis of the elastic properties of porous SiC derived from wood", "author": [ { "family_name": "Kaul", "given_name": "V. S.", "clpid": "Kaul-V-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Nanoindentation was used to measure the solid phase elastic modulus and hardness of porous silicon carbide derived from wood precursors. The results indicate that the solid phase of this material is composed of both SiC and unreacted carbon, and the elastic moduli and hardness of the two constituents differ by an order of magnitude. Modulus models for porous and composite materials correlate better with experimental observations when porosity is uniformly distributed.", "doi": "10.1016/j.scriptamat.2008.01.018", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2008-05", "series_number": "10", "volume": "58", "issue": "10", "pages": "886-889" }, { "id": "authors:55195-d3w23", "collection": "authors", "collection_id": "55195-d3w23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-105748685", "type": "article", "title": "Texture and microstructural development in gelcast barium hexaferrite", "author": [ { "family_name": "Hovis", "given_name": "D. B.", "clpid": "Hovis-D-B" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Kenik", "given_name": "E. A.", "clpid": "Kenik-E-A" } ], "abstract": "The development of texture in barium hexaferrite by templated grain growth was studied as a function of the Fe_2O_3/BaCO_3 ratio, B_2O_3 additions in the starting materials, and sintering temperature. A magnetic field was used to orient the template particles during the gelcasting process. Excess BaCO_3 resulted in abnormal grain growth and maximized texture, while B_2O_3 additions promoted coarsening, but no abnormal grain growth.", "doi": "10.1007/s10853-007-2375-2", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "2008-03", "series_number": "6", "volume": "43", "issue": "6", "pages": "1836-1843" }, { "id": "authors:w2de4-tkv84", "collection": "authors", "collection_id": "w2de4-tkv84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140714-103602932", "type": "article", "title": "Internal stresses and phase stability in multiphase environmental barrier coatings", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Weyant", "given_name": "C. M.", "clpid": "Weyant-C-M" }, { "family_name": "Harder", "given_name": "Bryan", "clpid": "Harder-B" }, { "family_name": "Almer", "given_name": "Jonathan", "clpid": "Almer-J" }, { "family_name": "Lee", "given_name": "Kang", "clpid": "Lee-K" } ], "abstract": "The use of silicon-based ceramics in power generation applications is limited by recession of the passivating SiO2 when it reacts with water-vapor to form a volatile hydroxide. Environmental barrier coatings are used to prevent diffusion of reactive species to the structural ceramic substrate. Often these barriers are multilayered and/or multiphase to provide optimal thermal expansion match, microstructural stability, as well as low diffusivities. High energy X-rays are used to assess internal stress as well as phase content and stability in two coating systems: alloyed Ta_2O_5 for Si_3N_4 and strontium-aluminosilicates for SiC/SiC. In particular, the role of phase transitions and precipitation on the coating internal stresses is evaluated along with their ramifications for coating lifetime.", "doi": "10.3139/146.101590", "issn": "1862-5282", "publisher": "Carl Hanser Verlag", "publication": "International Journal of Materials Research", "publication_date": "2007-12", "series_number": "12", "volume": "98", "issue": "12", "pages": "1188-1195" }, { "id": "authors:pbbxb-fh855", "collection": "authors", "collection_id": "pbbxb-fh855", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-130040547", "type": "article", "title": "Thermal Conductivity of Porous Silicon Carbide Derived from Wood Precursors", "author": [ { "family_name": "Pappacena", "given_name": "K. E.", "clpid": "Pappacena-K-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Wang", "given_name": "H.", "clpid": "Wang-H" }, { "family_name": "Porter", "given_name": "W. D.", "clpid": "Porter-W-D" } ], "abstract": "Biomorphic silicon carbide (bioSiC), a novel porous ceramic derived from natural wood precursors, has potential applicability at high temperatures, particularly when rapid temperature changes occur. The thermal conductivity of bioSiC from five different precursors was experimentally determined using flash diffusivity and specific heat measurements at temperatures ranging from room temperature to 1100\u00b0C. The results were compared with values obtained from object-oriented finite-element analysis (OOF). OOF was also used to model and understand the heat-flow paths through the complex bioSiC microstructures.", "doi": "10.1111/j.1551-2916.2007.01777.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2007-09", "series_number": "9", "volume": "90", "issue": "9", "pages": "2855-2862" }, { "id": "authors:7kg9r-0w676", "collection": "authors", "collection_id": "7kg9r-0w676", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-155230023", "type": "article", "title": "Self-Assembly and Stress Relaxation in Acrylic Triblock Copolymer Gels", "author": [ { "family_name": "Seitz", "given_name": "Michelle E.", "clpid": "Seitz-M-E" }, { "family_name": "Burghardt", "given_name": "Wesley R.", "clpid": "Burghardt-W-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Shull", "given_name": "Kenneth R.", "clpid": "Shull-K-R" } ], "abstract": "The structure and relaxation behavior of thermoreversible gels made with poly(methyl methacrylate)\u2212poly(n-butyl acrylate)\u2212poly(methyl methacrylate) [PMMA\u2212PnBA\u2212PMMA] triblock copolymers in 2-ethylhexanol, a midblock selective solvent, were studied by small-angle X-ray scattering (SAXS) and rheology. Effects of endblock length, endblock fraction, and gel concentration on the gel properties were investigated. A dramatic decrease in SAXS intensity was observed over a 20 \u00b0C interval where the gel transitions smoothly from elastic to viscous behavior. SAXS patterns were fit with a Percus\u2212Yevick disordered hard-sphere model from which aggregation number and average domain spacing were calculated. Aggregation number increases with increasing gel concentration and endblock length. Increasing the endblock length from 9K to 25K increases the relaxation time of a gel with a polymer volume fraction of 0.15 by a factor of 10^6. For a given triblock endblock fraction and molecular weight, the micelle aggregation number is strongly correlated to the gel relaxation time. Arrhenius behavior with an effective activation energy of ~550 kJ/mol was observed for all triblocks and concentrations. This very high effective energy barrier describes gels relaxation behavior over a 40 \u00b0C temperature range, where the relaxation times vary by a factor of 10^(10).", "doi": "10.1021/ma061993+", "issn": "0024-9297", "publisher": "American Chemical Society", "publication": "Macromolecules", "publication_date": "2007-02-20", "series_number": "4", "volume": "40", "issue": "4", "pages": "1218-1226" }, { "id": "authors:acsmd-tx108", "collection": "authors", "collection_id": "acsmd-tx108", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181320601", "type": "article", "title": "Noninvasive methods for the investigation of ancient Chinese jades: an integrated analytical approach", "author": [ { "family_name": "Casadio", "given_name": "Francesca", "clpid": "Casadio-F" }, { "family_name": "Douglas", "given_name": "Janet G.", "clpid": "Douglas-J-G" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "This paper reports on an integrated analytical approach for the noninvasive characterization of Chinese nephrite samples, encompassing both geological reference specimens and museum objects. Natural variations induced by cationic substitutions, as well as human-induced alterations such as heating, which both affect color, are the focus of this contribution. Totally noninvasive methods of analysis were used, including X-ray fluorescence spectroscopy, Raman microspectroscopy, visible reflectance spectroscopy and X-ray diffraction; moreover, the feasibility of using a portable Raman spectrometer for the in-field identification of jades has been demonstrated. Fe/Fe+Mg (% p.f.u.) ratios of the jades have been calculated based on hydroxyl stretching Raman bands, which will provide an important addition to similar data that are being collected at major museums in the Western and Eastern hemispheres.", "doi": "10.1007/s00216-006-0684-y", "issn": "1618-2642", "publisher": "Springer", "publication": "Analytical and Bioanalytical Chemistry", "publication_date": "2007-02", "series_number": "3", "volume": "387", "issue": "3", "pages": "791-801" }, { "id": "authors:m2k5n-pvy31", "collection": "authors", "collection_id": "m2k5n-pvy31", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140915-104116116", "type": "book_section", "title": "A stone kneeling figure in the Art Institute of Chicago: new evidence from scientific investigations and archaeological finds in China", "book_title": "Scientific Research on the Sculptural Arts of Asia", "author": [ { "family_name": "Casadio", "given_name": "Francesca", "clpid": "Casadio-F" }, { "family_name": "Xu", "given_name": "Jay", "clpid": "Xu-J" }, { "family_name": "Pearlstein", "given_name": "Elinor", "clpid": "Pearlstein-E" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Knowles", "given_name": "Ariel", "clpid": "Knowles-A" }, { "family_name": "Zhichun", "given_name": "Jing", "clpid": "Zhichun-J" } ], "contributor": [ { "family_name": "Douglas", "given_name": "J.", "clpid": "Douglas-J" } ], "abstract": "An ancient stone sculpture of a figure kneeling with hands bound behind him was bequeathed to the Art\nInstitute of Chicago in 1950 and for many years had no known counterpart. Comparable finds are now confirmed\nby a group of similar figures discovered since 1984 at several archaeological sites in the Chengdu plain of China's\nsouthwestern Sichuan province, which are datable to the late second millennium B.C. E. Unlike those recently unearthed\nfigures, carved of more roughly textured, yellowish gray or dark green stones, some of which preserve traces of\npigment that partially highlight their facial features, the Art lnstitute's example bears a smooth and shiny blackish\ngreen surface. Questions about the nature of this surface--whether coated with a paintlike film and/or darkened by\nheating- prompted a thorough investigation of the figure. Nondestructive techniques such as in situ Raman microscopy,\nx-ray diffraction, environmental scanning electron microscopy, and near infrared reflectance spectroscopy\nwere used to fully characterize the sculpture. Fourier transform infrared spectroscopy was employed to shed light\non the nature of applied materials such as fills, surface accretions, and possible coatings. Results of these extensive\nscientific examinations, evaluated together with experimental tests of heating and polishing as well as with relevant\narchaeological evidence recently brought to light, have enhanced our understanding of the surface treatment of this\nfascinating and hitherto enigmatic sculpture.", "isbn": "1904982204", "publisher": "Archetype Press", "place_of_publication": "London", "publication_date": "2007", "pages": "3-11" }, { "id": "authors:pmcjb-88e87", "collection": "authors", "collection_id": "pmcjb-88e87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-162004301", "type": "book_section", "title": "Processing, microstructure and mechanical behavior of SiC-based ceramics via naturally derived scaffolds", "book_title": "Mechanical Properties and Performance Engineering Ceramics II: Engineering and Science Proceedings", "author": [ { "family_name": "de Arellano L\u00f3pez", "given_name": "A. R.", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Mart\u00ednez-Fern\u00e1ndez", "given_name": "J.", "clpid": "Mart\u00ednez-Fern\u00e1ndez-J" }, { "family_name": "Varela-Feria", "given_name": "F. M.", "clpid": "Varela-Feria-F-M" }, { "family_name": "Sep\u00falveda", "given_name": "R.", "clpid": "Sep\u00falveda-R" }, { "family_name": "L\u00f3pez Robledo", "given_name": "M. J.", "clpid": "L\u00f3pez Robledo-M-J" }, { "family_name": "Llorca", "given_name": "J.", "clpid": "Llorca-J" }, { "family_name": "Pastor", "given_name": "J. Y.", "clpid": "Pastor-J-Y" }, { "family_name": "Presas", "given_name": "M.", "clpid": "Presas-M" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Kaul", "given_name": "V. S.", "clpid": "Kaul-V-S" }, { "family_name": "Pappacena", "given_name": "K. E.", "clpid": "Pappacena-K-E" }, { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" } ], "contributor": [ { "family_name": "Tandon", "given_name": "Rajan", "clpid": "Tandon-R" }, { "family_name": "Wereszczak", "given_name": "Andrew", "clpid": "Wereszczak-A" }, { "family_name": "Lara-Curzio", "given_name": "Edgar", "clpid": "Lara-Curzio-E" } ], "abstract": "Biomorphic silicon carbide ceramics are a new class of materials fabricated by reactive infiltration of molten silicon with carbonaceus preforms obtained from wood pyrolysis. The resulting material is a Si/SiC composite, in which the SiC forms a skeleton that replicates the wood microstructure with unreacted Si filling the pores. The silicon can be removed from the composite creating a highly porous SiC material that can be refilled with other products, like metal alloys, to create ceramic/metal composites.", "doi": "10.1002/9780470291313.ch60", "isbn": "978-0-470-08052-8", "publisher": "American Ceramics Society", "place_of_publication": "Westerville, Ohio", "publication_date": "2007", "pages": "635-650" }, { "id": "authors:kxznp-3k808", "collection": "authors", "collection_id": "kxznp-3k808", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140715-140006126", "type": "article", "title": "Composites by aluminum infiltration of porous silicon carbide derived from wood precursors", "author": [ { "family_name": "Wilkes", "given_name": "T. E.", "clpid": "Wilkes-T-E" }, { "family_name": "Young", "given_name": "M. L.", "clpid": "Young-M-L" }, { "family_name": "Sepulveda", "given_name": "R. E.", "clpid": "Sepulveda-R-E" }, { "family_name": "Dunand", "given_name": "D. C.", "clpid": "Dunand-D-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Composites were fabricated by infiltration of molten Al\u201313Si\u20139Mg into porous SiC derived from wood. The composite microstructure retains the heterogeneous orthorhombic symmetry of the initial wood material. As compared to the uninfiltrated SiC preform, the composite shows much improved transverse compressive strength and stiffness, resulting in reduced anisotropy.", "doi": "10.1016/j.scriptamat.2006.08.040", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2006-12", "series_number": "12", "volume": "55", "issue": "12", "pages": "1083-1086" }, { "id": "authors:p7mf4-k8j80", "collection": "authors", "collection_id": "p7mf4-k8j80", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140710-105757237", "type": "article", "title": "Precursor selection and its role in the mechanical properties of porous SiC derived from wood", "author": [ { "family_name": "Kaul", "given_name": "V. S.", "clpid": "Kaul-V-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Sep\u00falveda", "given_name": "R.", "clpid": "Sep\u00falveda-R" }, { "family_name": "de Arellano L\u00f3pez", "given_name": "A. R.", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Mart\u00ednez-Fern\u00e1ndez", "given_name": "J.", "clpid": "Mart\u00ednez-Fern\u00e1ndez-J" } ], "abstract": "The compressive strength, elastic modulus, and fracture toughness of porous SiC derived from wood precursors were measured. These mechanical properties and the amount of unreacted carbon were found to be a function of porosity and pore size distribution, which are dependent on the precursor wood. The presence of residual carbon was found to have a deleterious effect on compressive strength and elastic modulus. The amount of residual carbon was quantified and found to be higher in materials derived from precursors where the pores are non-uniformly distributed and areas with a higher concentration of small pores. The pore anisotropy and density gradients in wood led to a preferred crack path along growth rings in directions parallel to the wood growth direction. These findings can be used to select the proper precursor wood to obtain the desired properties in the final porous SiC.", "doi": "10.1016/j.msea.2006.05.033", "issn": "0921-5093", "publisher": "Elsevier", "publication": "Materials Science and Engineering A", "publication_date": "2006-07-25", "series_number": "1-2", "volume": "428", "issue": "1-2", "pages": "225-232" }, { "id": "authors:cye4j-bgm77", "collection": "authors", "collection_id": "cye4j-bgm77", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181320718", "type": "article", "title": "Residual stress and microstructural evolution in environmental barrier coatings of tantalum oxide alloyed with aluminum oxide and lanthanum oxide", "author": [ { "family_name": "Weyant", "given_name": "C. M.", "clpid": "Weyant-C-M" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Almer", "given_name": "J. D.", "clpid": "Almer-J-D" }, { "family_name": "Guiheen", "given_name": "J. V.", "clpid": "Guiheen-J-V" } ], "abstract": "Pure Ta_2O_5 has been investigated as a possible environmental barrier coating (EBC) material for silicon nitride-based ceramics, but was found to be inadequate because of localized buckling and the formation of microcracks. To address these issues, alloying additions were explored to improve some of the properties of Ta_2O_5 for this application. Aluminum oxide (Al_2O_3) was investigated to stabilize the low-temperature \u03b2-Ta_2O_5 phase and reduce grain growth in the coating through the formation of a solid solution. Lanthanum oxide (La_2O_3) was investigated as a second phase former designed to pin grain-boundaries and reduce grain growth. High-brilliance X-rays at the Advanced Photon Source at Argonne National Laboratory were used to evaluate residual stress and phase evolution in the alloyed coatings. Scanning electron microscopy was used to study microstructural changes and grain growth. Al_2O_3 was successful at stabilizing \u03b2-Ta_2O_5 and the Al_2O_3 and La_2O_3 significantly reduced grain growth in the coatings. Significant microcracking was observed in the coatings alloyed with Al_2O_3 after thermal cycling in air. Coatings alloyed with Al_2O_3 and La_2O_3 showed no evidence of microcracking. However, some of the alloyed coatings which were first thermally cycled in air and subsequently exposed to high-temperature steam completely delaminated from the AS800 silicon nitride substrates, a highly undesirable result for an EBC.", "doi": "10.1111/j.1551-2916.2005.00830.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2006-03", "series_number": "3", "volume": "89", "issue": "3", "pages": "971-978" }, { "id": "authors:6nm45-25g11", "collection": "authors", "collection_id": "6nm45-25g11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181320843", "type": "article", "title": "Residual stress and microstructural evolution in tantalum oxide coatings on silicon nitride", "author": [ { "family_name": "Weyant", "given_name": "C. M.", "clpid": "Weyant-C-M" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Almer", "given_name": "J. D.", "clpid": "Almer-J-D" }, { "family_name": "Guiheen", "given_name": "J. V.", "clpid": "Guiheen-J-V" } ], "abstract": "Due to its coefficient of thermal expansion (CTE) and phase stability up to 1360\u00b0C, tantalum oxide (Ta_2O_5) was identified and investigated as a candidate environmental barrier coating for silicon nitride-based ceramics. Ta_2O_5 coatings were plasma sprayed onto AS800, a silicon nitride ceramic from Honeywell International, and subjected to static and cyclic heat treatments up to 1200\u00b0C in air. Cross-sections from coated and uncoated substrates were polished and etched to reveal the effect of heat treatments on microstructure and grain size. As-sprayed coatings contained vertical cracks that healed after thermal exposure. Significant grain growth that was observed in the coatings led to microcracking due to the anisotropic CTE of Ta_2O_5. High-energy X-ray diffraction was used to determine the effect of heat treatment on residual stress and phases. The uncoated substrates were found to have a surface compressive layer before and after thermal cycling. Coating stresses in the as-sprayed state were found to be tensile, but became compressive after heat treatment. The microcracking and buckling that occurred in the heat-treated coatings led to stress relaxation after long heat treatments, but ultimately would be detrimental to the function of the coating as an environmental barrier by affording open pathways for volatile species to reach the underlying ceramic.", "doi": "10.1111/j.1551-2916.2005.00396.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2005-08", "series_number": "8", "volume": "88", "issue": "8", "pages": "2169-2176" }, { "id": "authors:jsk16-62189", "collection": "authors", "collection_id": "jsk16-62189", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181320949", "type": "article", "title": "Processing and surface flaw tolerance of alumina bilayers", "author": [ { "family_name": "Montgomery", "given_name": "John K.", "clpid": "Montgomery-J-K" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Alumina bilayers of different relative thicknesses and densities were produced with a strong interface using a modified gel-casting technique. Tolerance to surface damage is examined using biaxial flexure of disks damaged with a single Vickers indentation at various loads. The greatest surface flaw tolerance is seen in bilayers consisting of a thin porous layer on the tensile surface coupled to a thick dense layer. Here, the modulus mismatch causes redistribution of the applied stress, and fracture initiates at the internal porous-dense interface rather than at the surface from the introduced indentation flaw.", "doi": "10.1111/j.1551-2916.2005.00073.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2005-02", "series_number": "2", "volume": "88", "issue": "2", "pages": "287-292" }, { "id": "authors:5rspm-ap130", "collection": "authors", "collection_id": "5rspm-ap130", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321046", "type": "article", "title": "Synthetic crossed-lamellar microstructures in oxide ceramics", "author": [ { "family_name": "Kaul", "given_name": "Vikram S.", "clpid": "Kaul-V-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A process has been developed to produce a crossed-lamellar-type microstructure in mullite combining tape casting, oriented lamination, and templated grain growth. Ceramic laminates were produced with aligned rod-like grains with the alignment direction varying from layer-to-layer with abrupt interfaces between layers. Other designed microstructures are also possible using this process.", "issn": "1229-9162", "publisher": "Hanyang University", "publication": "Journal of Ceramic Processing Research", "publication_date": "2005", "series_number": "3", "volume": "6", "issue": "3", "pages": "218-222" }, { "id": "authors:ys99h-rbt27", "collection": "authors", "collection_id": "ys99h-rbt27", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321138", "type": "article", "title": "Thermal conductivity, phase stability, and oxidation resistance of Y_3Al_5O_(12) (YAG)/Y_2O_3-ZrO_2 (YSZ) thermal-barrier coatings", "author": [ { "family_name": "Su", "given_name": "Y. J.", "clpid": "Su-Y-Jennifer" }, { "family_name": "Trice", "given_name": "R. W.", "clpid": "Trice-R-W" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Wang", "given_name": "H.", "clpid": "Wang-Hsin" }, { "family_name": "Porter", "given_name": "W. D.", "clpid": "Porter-W-D" } ], "abstract": "This paper describes a new multilayer TBC that incorporates a 10 \u03bcm-thick oxygen barrier layer of yttrium\u2013aluminum garnet (YAG) into a typical YSZ TBC system. The thermal conductivity of as-sprayed YAG/YSZ coatings was reduced due to excessive porosity and amorphous areas in the YAG layer. After long-term heat treatments, the conductivity of the multilayer was unaffected by the presence of YAG. Sintering and recrystallization of the amorphous YAG regions occurred during high-temperature heat treatments. While YAG itself possesses excellent phase stability, its presence also improved the phase stability of zirconia near the YAG/YSZ interface, inhibiting the outward diffusion of yttrium from high-yttria t-ZrO_2 The YAG layer reduced the NiCoCrAlY bond-coat oxidation rate by a factor of three during isothermalfurnace tests conducted at 1200\u00b0 C.", "doi": "10.1023/B:OXID.0000025334.02788.d3", "issn": "0030-770X", "publisher": "Springer", "publication": "Oxidation of Metals", "publication_date": "2004-04", "series_number": "3-4", "volume": "61", "issue": "3-4", "pages": "253-271" }, { "id": "authors:zdgw0-aek91", "collection": "authors", "collection_id": "zdgw0-aek91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321368", "type": "article", "title": "Tantalum oxide coatings as candidate environmental barriers", "author": [ { "family_name": "Moldovan", "given_name": "Monica", "clpid": "Moldovan-M" }, { "family_name": "Weyant", "given_name": "C. M.", "clpid": "Weyant-C-M" }, { "family_name": "Johnson", "given_name": "D. Lynn", "clpid": "Johnson-D-L" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Tantalum (Ta) oxide, due to its high-temperature capabilities and thermal expansion coefficient similar to silicon nitride, is a promising candidate for environmental barriers for silicon (Si) nitride-based ceramics. This paper focuses on the development of plasma-sprayed Ta oxide as an environmental barrier coating for silicon nitride. Using a D-optimal design of experiments, plasma-spray processing variables were optimized to maximize coating density. The effect of processing variables on coating thickness was also determined. X-ray diffraction (XRD) was use to ascertain that the as-sprayed coatings were comprised of \u03b1- and \u03b2-Ta2O5, but were fully converted to \u03b2-Ta_2O_5 after a 1200 \u00b0C heat treatment. Grain growth of the Ta_2O_5 followed a time dependence of t^(0.2) at 1200 \u00b0C.", "doi": "10.1007/s11666-004-0049-z", "issn": "1059-9630", "publisher": "ASM International", "publication": "Journal of Thermal Spray Technology", "publication_date": "2004-03", "series_number": "1", "volume": "13", "issue": "1", "pages": "51-56" }, { "id": "authors:tqfhj-5sw21", "collection": "authors", "collection_id": "tqfhj-5sw21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321255", "type": "article", "title": "Editorial", "author": [ { "family_name": "Zhu", "given_name": "Dongming", "clpid": "Zhu-D" }, { "family_name": "Va\u00dfen", "given_name": "Robert", "clpid": "Va\u00dfen-R" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Ceramic thermal and environmental barrier coatings are used in gas turbine engines to protect engine hot-section components in harsh\ncombustion environments, and extend component lifetimes. For future high performance engines, the development of advanced thermal\nand environmental barrier coating systems will allow these coatings to be more aggressively used to simultaneously increase engine\noperating temperature and reduce cooling requirements, thereby leading to significant improvements in engine power density and\nefficiency. Advanced ceramic coatings for high efficiency and low emission engine applications have demonstrated improved temperature\nreduction and environmental protection benefits in engine combustion and thermal cyclic environments for metallic and\nceramic components.", "doi": "10.1007/s11666-004-0039-1", "issn": "1059-9630", "publisher": "ASM International", "publication": "Journal of Thermal Spray Technology", "publication_date": "2004-03", "series_number": "1", "volume": "13", "issue": "1", "pages": "3" }, { "id": "authors:8r4x4-yyv68", "collection": "authors", "collection_id": "8r4x4-yyv68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321491", "type": "article", "title": "A thermoreversible gelcasting technique for ceramic laminates", "author": [ { "family_name": "Montgomery", "given_name": "John K.", "clpid": "Montgomery-J-K" }, { "family_name": "Botha", "given_name": "Adele S.", "clpid": "Botha-A-S" }, { "family_name": "Drzal", "given_name": "Peter L.", "clpid": "Drzal-P-L" }, { "family_name": "Shull", "given_name": "Kenneth R.", "clpid": "Shull-K-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "An improved thermoreversible gelcasting technique has been developed which affords the direct casting of laminates. A higher boiling point solvent, pentanol, in conjunction with a better dispersant permitted higher solids loading and optimized processing time for the gel. The technique has been demonstrated for Al_2O_3 bilayers of two densities.", "doi": "10.1016/S1359-6462(02)00517-1", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2003-03-17", "series_number": "6", "volume": "48", "issue": "6", "pages": "785-789" }, { "id": "authors:vrgbr-8bn11", "collection": "authors", "collection_id": "vrgbr-8bn11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210114-135221913", "type": "book_section", "title": "TMS Annual Meeting: Preface", "book_title": "Electron Microscopy, its Role in Materials Science: the Mike Meshii Symposium", "author": [ { "family_name": "Faber", "given_name": "K.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fine", "given_name": "M.", "clpid": "Fine-M" }, { "family_name": "King", "given_name": "W.", "clpid": "King-W" }, { "family_name": "Liaw", "given_name": "P.", "clpid": "Liaw-Peter-K" }, { "family_name": "Mori", "given_name": "B.", "clpid": "Mori-B" }, { "family_name": "Weertman", "given_name": "J.", "clpid": "Weertman-Julia-R" } ], "contributor": [ { "family_name": "Weertman", "given_name": "Julia R.", "clpid": "Weertman-Julia-R" }, { "family_name": "Meshii", "given_name": "Mike", "clpid": "Meshii-Mike" } ], "abstract": "[no abstract]", "isbn": "9780873395359", "publisher": "Minerals, Metals and Materials Society", "place_of_publication": "Warrendale, PA", "publication_date": "2003-03", "pages": "ix-x" }, { "id": "authors:qzbp0-r8562", "collection": "authors", "collection_id": "qzbp0-r8562", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321645", "type": "article", "title": "Effect of heat treatment on phase stability, microstructure, and thermal conductivity of plasma-sprayed YSZ", "author": [ { "family_name": "Trice", "given_name": "R. W.", "clpid": "Trice-R-W" }, { "family_name": "Su", "given_name": "Y. Jennifer", "clpid": "Su-Y-Jennifer" }, { "family_name": "Mawdsley", "given_name": "J. R.", "clpid": "Mawdsley-J-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "de Arellano-L\u00f3pez", "given_name": "A. R.", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Wang", "given_name": "Hsin", "clpid": "Wang-Hsin" }, { "family_name": "Porter", "given_name": "W. D.", "clpid": "Porter-W-D" } ], "abstract": "The effects of 50-hour heat treatments at 1000\u00b0C, 1200\u00b0C, and 1400\u00b0C on air plasma-sprayed coatings of 7 wt% Y_2O_3-ZrO_2 (YSZ) have been investigated. Changes in the phase stability and microstructure were investigated using x-ray diffraction and transmission electron microscopy, respectively. Changes in the thermal conductivity of the coating that occurred during heat treatment were interpreted with respect to microstructural evolution. A metastable tetragonal zirconia phase, with a non-equilibrium amount of Y_2O_3 stabilizer, was the predominant phase in the as-sprayed coating. Upon heating to 1000\u00b0C for 50 hours, the concentration of the Y_2O_3 in the t-zirconia began to decrease as predicted by the Y_2O_3-ZrO_2 phase diagram. The c-ZrO_2 phase was first observed after the 50-hour heat treatment at 1200\u00b0C; monoclinic zirconia was observed after the 50-hour heat treatment at 1400\u00b0C. TEM analysis revealed closure of intralamellar microcracks after the 50-hour/1000\u00b0C heat treatment; however, the lamellar morphology was retained. After the 50-hour/1200\u00b0C heat treatment, a distinct change was observed in the interlamellar pores; equiaxed grains replaced the long, columnar grains, with some remnant lamellae still observed. No lamellae were observed after the 50-hour/1400\u00b0C heat treatment. Rather, the microstructure was equivalent when viewed in either plan view or cross-section, revealing large grains with regions of monoclinic zirconia. Thermal conductivity increased after every heat treatment. It is believed that changes in the intralamellar microcracks and/or interlamellar pores are responsible for the increase in thermal conductivity after the 1000\u00b0C and 1200\u00b0C heat treatments. The increase in thermal conductivity that occurs after the 50-hour/1400\u00b0C heat treatment is proposed to be due to the formation of m-ZrO_2, which has a higher thermal conductivity than tetragonal or cubic zirconia.", "doi": "10.1023/A:1015310509520", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "2002-06", "series_number": "11", "volume": "37", "issue": "11", "pages": "2359-2365" }, { "id": "authors:q27pj-y8b78", "collection": "authors", "collection_id": "q27pj-y8b78", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181322108", "type": "article", "title": "Thermal properties of pitch-derived graphite foam", "author": [ { "family_name": "Gaies", "given_name": "D.", "clpid": "Gaies-D" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Graphite foams make potentially desirable engineering materials because of their high thermal conductivity coupled with their low density. Compared to conventional thermal management materials, such as copper and aluminum, graphite foams have specific thermal conductivity values up to five times higher. A high specific thermal conductivity combined with relatively high specific strength make graphite foam an attractive material for use in thermal management applications. Other properties of graphite foam, such as a relatively low coefficient of thermal expansion (CTE), make the material dimensionally stable, and thus, well suited to thermal applications.", "doi": "10.1016/S0008-6223(02)00099-4", "issn": "0008-6223", "publisher": "Elsevier", "publication": "Carbon", "publication_date": "2002-06", "series_number": "7", "volume": "40", "issue": "7", "pages": "1137-1140" }, { "id": "authors:dm690-6gd45", "collection": "authors", "collection_id": "dm690-6gd45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321764", "type": "article", "title": "Thermoreversible gelcasting: A novel ceramic processing technique", "author": [ { "family_name": "Montgomery", "given_name": "John K.", "clpid": "Montgomery-J-K" }, { "family_name": "Drzal", "given_name": "Peter L.", "clpid": "Drzal-P-L" }, { "family_name": "Shull", "given_name": "Kenneth R.", "clpid": "Shull-K-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A new ceramic processing method, thermoreversible gelcasting\n(TRG), has been developed. The method uses a gelation\nprocess that can be reversed multiple times. Two Al_2O_3\nsystems have been explored with the use of a specific triblock\ncopolymer to form a binding gel network. The mixture becomes\na free-flowing liquid on heating above 60\u00b0C. However,\non cooling below 60\u00b0C, the slurry instantaneously transforms\nto a physical gel. This process can be reversed easily (essentially\nwith an infinite processing time window) while the\nsolvent is present in the system, which is advantageous when\ntrying to produce high-quality dense pieces if initial casting\nirregularities occur. Near-theoretically dense specimens have\nbeen produced with properties consistent with reported values\nof high-density Al_2O_3.", "doi": "10.1111/j.1151-2916.2002.tb00239.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2002-05", "series_number": "5", "volume": "85", "issue": "5", "pages": "1164-1168" }, { "id": "authors:xksqr-cf411", "collection": "authors", "collection_id": "xksqr-cf411", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181321890", "type": "article", "title": "In situ characterization of small-particle plasma sprayed powders", "author": [ { "family_name": "Su", "given_name": "Y. J.", "clpid": "Su-Y-J" }, { "family_name": "Bernecki", "given_name": "T. F.", "clpid": "Bernecki-T-F" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The effect of various small-particle plasma spray powder injection parameters on the in situ particle position, velocity, and temperature is measured for yttria-stabilized zirconia and yttrium-aluminum-garnet powder. Using full-factorial experiments and multiple regression analysis, carrier gas flow, injector angle, and powder feeder disc speed were found to significantly affect the particle properties. Temperature and velocity were inversely related; on average, the cooler particles traveled faster. These properties also correlated to the particle position in the flame, where particles above the centerline of the flame traveled faster. The trends are discussed on the basis of residence time in the flame, as well as in terms of particle size segregation effects. Coating density and splat geometry reflect the temperature and velocity differences between the runs. Slower, hotter particles possessed more intrasplat and intersplat porosity and less splat-substrate contact area, leading to lower overall coating density.", "doi": "10.1361/105996302770348970", "issn": "1059-9630", "publisher": "ASM International", "publication": "Journal of Thermal Spray Technology", "publication_date": "2002-03", "series_number": "1", "volume": "11", "issue": "1", "pages": "52-61" }, { "id": "authors:8rrpa-x7w95", "collection": "authors", "collection_id": "8rrpa-x7w95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181322006", "type": "article", "title": "The role of starting powder size on the compressive response of stand-alone plasma-sprayed alumina coatings", "author": [ { "family_name": "Trice", "given_name": "R. W.", "clpid": "Trice-R-W" }, { "family_name": "Batson", "given_name": "C.", "clpid": "Batson-C" }, { "family_name": "Scharff", "given_name": "C.", "clpid": "Scharff-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Cylindrical stand-alone tubes of plasma-sprayed alumina were tested in uniaxial compression at room temperature, using strain gages to monitor axial strains. The effect of lamella size on the mechanical response was investigated by employing different starting powders to fabricate samples. The average powder sizes investigated included 9 \u03bcm, 19 \u03bcm and 32 \u03bcm alumina; the resulting effective lamella diameters were 10 \u03bcm, 28 \u03bcm, and 55 \u03bcm, respectively. Similar stress-strain hysteresis was observed on unloading in all tubes, independent of lamella size. A strong correlation between the failure stress and the cumulative strain at failure was also observed for tubes fabricated from the three powders. For samples with approximately constant densities, tubes plasma sprayed with the 9 \u03bcm powder exhibited greater moduli than tubes sprayed from either 19 or 32 \u03bcm powders. This difference was attributed to the greater percentage of unmelted \u03b1-Al_2O_3 in the coating.", "doi": "10.1023/A:1013738112206", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "2002-02", "series_number": "3", "volume": "37", "issue": "3", "pages": "629-636" }, { "id": "authors:fcq5s-xhc63", "collection": "authors", "collection_id": "fcq5s-xhc63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140912-172317679", "type": "article", "title": "Materials education: opportunities over a lifetime. A report on the 17th Biannual Conference of National Materials Policy, College Park, Maryland, USA, May 20-21, 2002", "author": [ { "family_name": "Anderson", "given_name": "Iver E.", "clpid": "Anderson-I-E" }, { "family_name": "Schwartz", "given_name": "Lyle H.", "clpid": "Schwartz-L-H" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Cargill", "given_name": "G. Slade, III", "clpid": "Cargill-G-S-III" }, { "family_name": "Houston", "given_name": "Betsy", "clpid": "Houston-B" } ], "abstract": "This article presents a report, in the form of highly abbreviated notes, of the 17th Biennial\nConference on National Materials Policy, held May 20-21, 2002, in College Park, Maryland, under\nthe sponsorship of the Federation of Materials Societies (FMS) and the University Materials Council.\nMore detailed information may be obtained by contacting FMS at betsyhou@ix.netcom.com, or\nconsulting the FMS web site http://www.materialsocieties.org.", "issn": "0738-7989", "publisher": "International Council on Materials Education", "publication": "Journal of Materials Education", "publication_date": "2002", "series_number": "4-6", "volume": "24", "issue": "4-6", "pages": "185-202" }, { "id": "authors:1yw0q-r8g75", "collection": "authors", "collection_id": "1yw0q-r8g75", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181322226", "type": "article", "title": "Fracture of a textured anisotropic ceramic", "author": [ { "family_name": "Zimmerman", "given_name": "M. H.", "clpid": "Zimmerman-M-H" }, { "family_name": "Baskin", "given_name": "D. M.", "clpid": "Baskin-D-M" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fuller", "given_name": "E. R., Jr.", "clpid": "Fuller-E-R-Jr" }, { "family_name": "Allen", "given_name": "A. J.", "clpid": "Allen-A-J" }, { "family_name": "Keane", "given_name": "D. T.", "clpid": "Keane-D-T" } ], "abstract": "The role of crystallographic texture in determining the fracture behavior of a highly anisotropic ceramic, iron titanate, has been examined. By exploiting the anisotropy in its single crystal magnetic susceptibility, crystallographically textured and untextured iron titanate microstructures were formed by gelcasting in the presence and absence of a strong magnetic field, respectively. The magnetic field-assisted processing imparted a fiber-like texture to the processed ceramic material in which the crystallographic b-axes of the grains aligned parallel to the applied field. Triaxial residual stress and lattice parameter measurements showed that both the untextured and textured materials had undergone significant stress\u2013relaxation, presumably due to spontaneous microcracking. Further, 'aggregates' of non-textured material were discovered within textured material that led to a population of meso-scale cracks (meso-cracks) in the microstructure oriented normal to the direction of alignment. Both crack populations were examined using a finite element simulation and confirmed by small angle neutron scattering measurements, and for meso-cracks, by X-ray tomography. Bend strength and R-curve behavior were evaluated as a function of texture and orientation in the magnetically processed materials. Strengths remained within 20% of that of the control material, except for one orientation, for which the strength decreased with increasing degree of texture due to favorably oriented meso-cracks. The R-curve behavior was highly anisotropic, with the peak fracture toughness of the magnetically processed material ranging from approximately equal to 2.5 times that of the control material. Additionally, the peak fracture toughness of each orientation increased with the degree of texture. Anisotropic fracture properties were related to interactions between the test crack and the population of meso-cracks.", "doi": "10.1016/S1359-6454(01)00224-5", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "2001-09-20", "series_number": "16", "volume": "49", "issue": "16", "pages": "3231-3242" }, { "id": "authors:m3zfj-kg906", "collection": "authors", "collection_id": "m3zfj-kg906", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181322406", "type": "article", "title": "Thermal conductivity and phase evolution of plasma-sprayed multilayer coatings", "author": [ { "family_name": "Su", "given_name": "Y. Jennifer", "clpid": "Su-Y-Jennifer" }, { "family_name": "Wang", "given_name": "Hsin", "clpid": "Wang-Hsin" }, { "family_name": "Porter", "given_name": "Wally D.", "clpid": "Porter-W-D" }, { "family_name": "de Arellano Lopez", "given_name": "A. R.", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Multilayer coatings were prepared using small-particle plasma spray to investigate the effect of interfaces on thermal conductivity and phase stability. Monolithic and multilayer alumina and yttria partially-stabilized zirconia coatings, with 0, 3, 20, and 40 interfaces in 200\u2013380 \u03bcm thick coatings were studied. Thermal conductivity was determined for the temperature range 25 \u00b0C to 1200 \u00b0C using the laser flash method and differential scanning calorimetry. Thermal conductivity of the multilayer coatings was accurately modeled by a series heat transfer equation, indicating that interfacial resistance plays a negligible role in heat transfer in the direction perpendicular to the coating plane. Powder X-ray diffraction results indicate that identical phase transitions occur in all the coatings. Independent of coating microstructure (i.e. layer thickness), as-sprayed \u03b3-Al_2O_3 transforms to \u03b1-Al_2O_3 after 100 hours at 1200\u00b0C; as-sprayed metastable t\u2032\u2013ZrO_2 converts to a mixture of t\u2013ZrO_2 and c\u2013ZrO_2 after 100 hours at 1300 \u00b0C. Thus, the results indicate that the interfaces do not aid in stabilizing the as-sprayed phases after prolonged severe heat treatments.", "doi": "10.1023/A:1017932617123", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "2001-07-15", "series_number": "14", "volume": "36", "issue": "14", "pages": "3511-3518" }, { "id": "authors:nc786-qv976", "collection": "authors", "collection_id": "nc786-qv976", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323080", "type": "article", "title": "Optimization of small-particle plasma-sprayed alumina coatings using designed experiments", "author": [ { "family_name": "Mawdsley", "given_name": "Jennifer R.", "clpid": "Mawdsley-J-R" }, { "family_name": "Su", "given_name": "Y. Jennifer", "clpid": "Su-Y-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Bernecki", "given_name": "Thomas F.", "clpid": "Bernecki-T-F" } ], "abstract": "Statistically designed experiments and multiple regression analysis have been used to determine the effects of processing parameters on three properties of small particle plasma sprayed alumina coatings \u2013 permeability, hardness, and thickness. First, an initial screening study was conducted with six variables at two levels each. Based on the results from this preliminary set, a second set of experiments was then conducted to probe the effects of four variables at three levels each. Multiple regression analysis was used to create models describing the effects of the variables on the three coating properties. The models were then used to identify the optimum conditions for producing coatings with the desired properties. It was found that the optimum conditions for low permeability did not correlate with those for high hardness due to defect structures that formed in the hardest coatings. The morphology of the defect structures was such that they did not affect indentation measurements, but did affect permeability. These defect structures formed as a result of copious splashing during splat formation and correlated to coatings that had high surface roughness.", "doi": "10.1016/S0921-5093(00)01992-4", "issn": "0921-5093", "publisher": "Elsevier", "publication": "Materials Science and Engineering A", "publication_date": "2001-06-30", "series_number": "1-2", "volume": "308", "issue": "1-2", "pages": "189-199" }, { "id": "authors:0gemh-xyr42", "collection": "authors", "collection_id": "0gemh-xyr42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323309", "type": "article", "title": "Textured microstructures in barium hexaferrite by magnetic field assisted gelcasting and templated grain growth", "author": [ { "family_name": "Hovis", "given_name": "David B.", "clpid": "Hovis-D-B" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The objective of this paper is to describe a method of producing textured barium hexaferrite by magnetic field assisted gelcasting while avoiding the limited solids loading caused by stacking of barium hexaferrite plates. We illustrate here a method of gelcasting a matrix of non-magnetic iron (III) oxide and barium carbonate in the presence of barium ferrite seeds for templated grain growth. At high temperatures, the iron oxide and barium carbonate react to form a fine-grained barium ferrite matrix surrounding the previously aligned barium ferrite seeds.", "doi": "10.1016/S1359-6462(01)00957-5", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2001-06-01", "series_number": "11", "volume": "44", "issue": "11", "pages": "2525-2529" }, { "id": "authors:pxcgq-6wh21", "collection": "authors", "collection_id": "pxcgq-6wh21", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323191", "type": "article", "title": "Moir\u00e9 interferometry analysis of fiber debonding", "author": [ { "family_name": "Easley", "given_name": "Thomas C.", "clpid": "Easley-T-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Shah", "given_name": "Surendra P.", "orcid": "0000-0002-3367-2394", "clpid": "Shah-S-P" } ], "abstract": "Progressive fiber debonding in steel fiber/cementitious matrix composites has been studied using a single fiber pullout test that permits simultaneous measurements of the load versus crack opening displacement relationship and Moir\u00e9 interferometry fringe patterns. Analysis of Moir\u00e9 interferometry patterns allows the fiber axial and interfacial shear stresses to be calculated along the entire fiber length. The interfacial shear stress distribution along the debonded length of the fiber indicates a steep decrease in shear stress with interfacial slip, from 6 to 1 MPa for 7 \u03bcm of fiber slip and a crack opening displacement of 22 \u03bcm. These results suggest that improvements in the toughness of cement-based composites could be achieved by developing materials in which the decrease in shear stress is less severe.", "doi": "10.1061/(ASCE)0733-9399(2001)127:6(625)", "issn": "0733-9399", "publisher": "American Society of Civil Engineers", "publication": "Journal of Engineering Mechanics", "publication_date": "2001-06", "series_number": "6", "volume": "127", "issue": "6", "pages": "625-629" }, { "id": "authors:5sav6-zah92", "collection": "authors", "collection_id": "5sav6-zah92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323409", "type": "article", "title": "Evolution of impedance spectra during debonding and pullout of single steel fibers from cement", "author": [ { "family_name": "Torrents", "given_name": "Josep M.", "clpid": "Torrents-J-M" }, { "family_name": "Easley", "given_name": "Thomas C.", "clpid": "Easley-T-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Mason", "given_name": "Thomas O.", "clpid": "Mason-T-O" }, { "family_name": "Shah", "given_name": "Surendra P.", "orcid": "0000-0002-3367-2394", "clpid": "Shah-S-P" } ], "abstract": "Impedance measurements were made during the debonding\nand pullout of a fully embedded, crack-bridging single steel\nfiber from a cement matrix. Nyquist plots gave evidence of two\nbulk arcs, and the \"cusp\" between them proved to be sensitive\nto both debonding and pullout of the embedded fiber. Physical\nsimulations that used a steel wire in tap water were applied to\ninterpret the debonding and pull-out results. The cusp resistance\nfrom impedance spectroscopy provided quantitative\ninformation about the extent of pullout and, at least qualitatively,\ncorrelated with the debond length before pullout. Impedance\nmeasurements on both sides of the matrix crack\nshowed that crack deflection and debonding occurred on both\nsides symmetrically.", "doi": "10.1111/j.1151-2916.2001.tb00735.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2001-04", "series_number": "4", "volume": "84", "issue": "4", "pages": "740-746" }, { "id": "authors:ynf77-85b64", "collection": "authors", "collection_id": "ynf77-85b64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140912-170049690", "type": "book_section", "title": "Ceramics: Microstructural Toughening (Excluding Transformation Toughening, Whisker Toughening, and Continuous Fiber Toughening)", "book_title": "Encyclopedia of Materials: Science and Technology", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Buschow", "given_name": "K. H. J\u00fcrgen", "clpid": "Buschow-K-H-J" }, { "family_name": "Cahn", "given_name": "Robert W.", "clpid": "Cahn-R-W" }, { "family_name": "Flemings", "given_name": "Merton C.", "clpid": "Flemings-M-C" }, { "family_name": "Ilschner", "given_name": "Bernhard", "clpid": "Ilschner-B" }, { "family_name": "Kramer", "given_name": "Edward J.", "clpid": "Kramer-E-J" }, { "family_name": "Mahajan", "given_name": "Subash", "clpid": "Mahajan-S" } ], "abstract": "The enhancement of fracture toughness in ceramic materials can occur over a broad range of length scales. The length scale that has received the greatest attention in structural ceramic materials is the microstructural scale, that of the grain dimensions that normally vary from 1 \u00b5m to 20 \u00b5m. In single-phase materials, weak grain boundaries or residual stresses resulting from thermal expansion anisotropy perturb the propagation of a crack. The same is true for grain boundary phases or particulate reinforcements in multiphase materials.", "doi": "10.1016/B0-08-043152-6/00206-0", "isbn": "0-08-043152-6", "publisher": "Elsevier", "place_of_publication": "Oxford", "publication_date": "2001", "pages": "1108-1113" }, { "id": "authors:33820-4ve25", "collection": "authors", "collection_id": "33820-4ve25", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323692", "type": "article", "title": "Effect of microstructure on high-temperature compressive creep of self-reinforced hot-pressed silicon nitride", "author": [ { "family_name": "Boling-Risser", "given_name": "Martha A.", "clpid": "Boling-Risser-Martha-A" }, { "family_name": "Goretta", "given_name": "K. C.", "clpid": "Goretta-K-C" }, { "family_name": "Routbort", "given_name": "J. L.", "clpid": "Routbort-J-L" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "An experimental self-reinforced hot-pressed silicon nitride was\nused to examine the effects of microstructure on high-temperature\ndeformation mechanisms during compression\ntesting. At 1575\u20131625\u00b0C, the as-received material exhibited a\nstress exponent of 1 and appeared to deform by steady-state\ngrain-boundary sliding accommodated by solution-reprecipitation\nof silicon nitride through the grain-boundary\nphase. The activation energy was 610 6 110 kJ/mol. At\n1450\u20131525\u00b0C for the as-received material, and at 1525\u20131600\u00b0C\nfor the larger-grained heat-treated samples, the stress exponent\nwas >1. Damage, primarily in the form of pockets of\nintergranular material at two-grain junctions, was observed in\nthese samples.", "doi": "10.1111/j.1151-2916.2000.tb01683.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2000-12", "series_number": "12", "volume": "83", "issue": "12", "pages": "3065-3069" }, { "id": "authors:rcvma-and55", "collection": "authors", "collection_id": "rcvma-and55", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323547", "type": "article", "title": "Deformation mechanisms in compression-loaded, stand-alone plasma-sprayed alumina coatings", "author": [ { "family_name": "Trice", "given_name": "Rodney W.", "clpid": "Trice-R-W" }, { "family_name": "Prine", "given_name": "David W.", "clpid": "Prine-D-W" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Cylindrical, stand-alone tubes of plasma-sprayed alumina were tested in compression in the axial direction at room temperature, using strain gauges to monitor axial and circumferential strains. The primary compression-loading profile used was cyclic loading, with monotonically increased peak stresses. Hysteresis was observed in the stress-strain response on unloading, beginning at a peak stress of 50 MPa. The modulus decreased as the maximum applied stress increased. The stress-strain response was only linear at low stresses; the degree of nonlinearity at high stresses scaled with the stress applied. One-hour dwells at constant stress at room temperature revealed a time-dependent strain response. Using transmission electron microscopy and acoustic emission to investigate deformation mechanisms, the stress-strain response was correlated with crack pop in, growth, and arrest. It is proposed that the numerous defects in plasma-sprayed coatings, including porosity and microcracks, serve as sites for crack nucleation and/or propagation. As these small, nucleated cracks extend under the applied stress, they propagate nearly parallel to the loading direction along interlamellae boundaries. With increasing stress, these cracks ultimately link, resulting in catastrophic failure.", "doi": "10.1111/j.1151-2916.2000.tb01682.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2000-12", "series_number": "12", "volume": "83", "issue": "12", "pages": "3057-3064" }, { "id": "authors:djjyr-bb554", "collection": "authors", "collection_id": "djjyr-bb554", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323856", "type": "article", "title": "Estudio comparativo de t\u00e9cnicas de preparaci\u00f3n de muestraspara microscop\u00eda electr\u00f3nica de transmisi\u00f3n de recubrimientos cer\u00e1micos proyectados por plasma", "author": [ { "family_name": "de Arellano L\u00f3pez", "given_name": "A. Ram\u00edrez", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Chiou", "given_name": "W. A.", "clpid": "Chiou-W-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The development of advanced materials, with complex microstructures, is a permanent challenge to the development and application of new efficient techniques for microstructural characterization. In ceramic coatings on metals, there exist a differential ion-milling ratio between both components, limiting in principle the use of conventional techniques. In this work, we report on a comparative study of TEM sample preparation techniques for plasma-sprayed ceramic coatings. Firstly, we have used a procedure derived from the conventional one (polishing, dimpling, ion milling), and alternatively a new technique using focused ion-beam milling. The material selected for this study is fine-grained alumina that was plasma-sprayed on a steel substrate. The efficiency of both techniques is discussed along with the most significant microstructural features of the material subject of study.", "issn": "0366-3175", "publisher": "Spanish Society of Ceramics and Glass and the Spanish National Research Council CSIC", "publication": "Bolet\u00edn de la Sociedad Espa\u00f1ola de Cer\u00e1mica y Vidrio", "publication_date": "2000-11", "series_number": "6", "volume": "39", "issue": "6", "pages": "735-740" }, { "id": "authors:1gagk-f4x33", "collection": "authors", "collection_id": "1gagk-f4x33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181323960", "type": "article", "title": "The dissociation of NZP (Ca_(0.5)Sr_(0.5)Zr_4P_6O_(24)) during plasma spraying during plasma spraying", "author": [ { "family_name": "Trice", "given_name": "Rodney W.", "clpid": "Trice-R-W" }, { "family_name": "Brewer", "given_name": "Luke N.", "clpid": "Brewer-L-N" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Sodium zirconium phosphate (NaZr_2P_3O_(12) or NZP) was first systematically evaluated in the early 1980s by Roy and co\u2013workers, who demonstrated its extremely low coefficient of thermal expansion (CTE). It was later shown that other group IA and IIA atoms can be ionically substituted into the NZP crystal structure to adjust the CTE. As a result of their low and tailorable CTEs, NZP's have potential use as a protective coating for silicon\u2013based ceramics and carbon\u2013carbon composites.\n\nOne technique for the application of ceramic coatings employs plasma\u2013spraying. In this process, powders are injected into a plasma flame, melted, and propelled onto a substrate. The resulting coating microstructure is typically composed of thin lamellae (from each melted particle) stacked on top of one another during each pass of the torch. In the current research, NZP has been plasma\u2013sprayed using the recently patented small particle plasma\u2013spray process. The microstructure was then analyzed using transmission electron microscopy and x\u2013ray diffraction to identify the phases in the complex coating that resulted.", "doi": "10.1016/S1359-6462(00)00303-1", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2000-04-14", "series_number": "9", "volume": "42", "issue": "9", "pages": "855-860" }, { "id": "authors:rynkv-f1v47", "collection": "authors", "collection_id": "rynkv-f1v47", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181324112", "type": "article", "title": "Role of lamellae morphology on the microstructural development and mechanical properties of small-particle plasma-sprayed alumina", "author": [ { "family_name": "Trice", "given_name": "Rodney W.", "clpid": "Trice-R-W" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The influence of spray parameters on the microstructure and\nflexural strength of plasma-sprayed alumina was investigated.\nCoatings were applied using a small-particle plasma spray\n(SPPS) method, which is a recently patented process that\nallows submicrometer-sized powders to be sprayed. Using\nidentical starting powders, coatings that were produced using\ntwo distinctly different spray conditions exhibited significant\ndifferences in both microstructure and strength. Scanning\nelectron microscopy investigations of single lamellae (or splats)\nrevealed that, for one spray condition, melted alumina particles\nwill splash when they contact the substrate. The morphology\nof the splats that comprised the subsequent layers of the\ncoating also were highly fragmented and thinner than lamellae\nformed under \"nonsplashing\" spray conditions. The surface\nroughness was strongly dependent on the morphology of the\nlamellae; increased roughness was noted for fragmented\nsplats. Thick coatings that were comprised of splashed splats\ndeveloped a unique microstructural feature that was responsible\nfor the observed increase in roughness. These microstructural\ndifferences greatly influenced the flexure strength, which\nvaried from 75 \u00b1 21 MPa for the nonsplashing spray condition\nto 17 \u00b1 2.4 MPa for the \"splashing\" condition.", "doi": "10.1111/j.1151-2916.2000.tb01290.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "2000-04", "series_number": "4", "volume": "83", "issue": "4", "pages": "889-896" }, { "id": "authors:cy81w-zkp11", "collection": "authors", "collection_id": "cy81w-zkp11", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181324208", "type": "article", "title": "Processing of stepped-density alumina via gelcasting and reaction bonding techniques", "author": [ { "family_name": "Montgomery", "given_name": "J. K.", "clpid": "Montgomery-J-K" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Ceramics that combine property gradients or steps in monolithic bodies are increasingly being sought as alternatives to ceramic composites made of multiple dissimilar materials. Furthermore, more sophisticated applications specify single components to serve many functions that often require disparate properties. For example, oxygen impermeability and high compliance may need to be coupled with low thermal conductivity in thermal barrier coatings or a thin, oxygen permeable membrane may need to be coupled to a rigid porous support for electrochemical gas extraction. Density graded materials are also of interest for structural applications, as one may couple a thin, dense wear resistant layer with a lightweight support structure or a porous, flaw tolerant surface with a dense, stiff support structure.\n\nHowever, graded density ceramics are difficult to process due to the need to accommodate differential volume changes upon firing. For example, a green body containing a particle size gradient would result in graded density due to higher densification of the small particle portion upon firing. However, due to the non-uniform volume changes throughout the specimen, sintering stresses occur which cause macroscopic cracking. This paper presents a novel method to produce stepped-density alumina bodies which maintain mechanical integrity by eliminating non-uniform volume changes. The processing instead relies on a reaction bonding technique.", "doi": "10.1016/S1359-6462(99)00342-5", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "2000-01-17", "series_number": "3", "volume": "42", "issue": "3", "pages": "283-287" }, { "id": "authors:s0wnq-vm123", "collection": "authors", "collection_id": "s0wnq-vm123", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181324485", "type": "article", "title": "Use of a crack-bridging single-fiber pullout test to study steel fiber/cementitious matrix composites", "author": [ { "family_name": "Easley", "given_name": "Thomas C.", "clpid": "Easley-T-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Shah", "given_name": "Surendra P.", "orcid": "0000-0002-3367-2394", "clpid": "Shah-S-P" } ], "abstract": "The fracture process of steel fiber/cementitious matrix composites has been studied using a single-fiber pullout test that permits detailed measurements of the load-crack opening displacement relationship during fiber debonding and unloading. Using a suitable analytical model, the interfacial fracture energy and interfacial sliding friction have been calculated for composites incorporating steel fibers with cement paste or mortar matrices. Comparison of theoretical debonding curves with the experimental data show that the model accurately represents the fiber debonding process, except for a decrease in interfacial sliding friction due to wear of matrix asperities at the interface. Differences between the calculated interfacial properties of several specimens are associated with changes in the interfacial microstructure.", "doi": "10.1111/j.1151-2916.1999.tb02274.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1999-12", "series_number": "12", "volume": "82", "issue": "12", "pages": "3513-3520" }, { "id": "authors:15dbb-75g97", "collection": "authors", "collection_id": "15dbb-75g97", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181324609", "type": "article", "title": "The role of NZP additions in plasma-sprayed YSZ: microstructure, thermal conductivity and phase stability effects", "author": [ { "family_name": "Trice", "given_name": "Rodney W.", "clpid": "Trice-R-W" }, { "family_name": "Su", "given_name": "Y. Jennifer", "clpid": "Su-Y-Jennifer" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Wang", "given_name": "Hsin", "clpid": "Wang-Hsin" }, { "family_name": "Porter", "given_name": "Wally", "clpid": "Porter-W-D" } ], "abstract": "A concept for lowering the thermal conductivity of plasma-sprayed yttria-stabilized zirconia (YSZ) was evaluated by adding a low thermal conductivity secondary phase. Ca_(0.5)Sr_(0.5)Zr_4P_6O_(24), a member of the zirconium phosphate or NZP family, was co-sprayed with YSZ using the recently patented small-particle plasma-spray process. The amount of NZP phase in the YSZ varied from 4 to 18 vol.%. Transmission electron microscopy revealed that the plasma-sprayed NZP existed as 30-50 nm size grains when sprayed with YSZ. Between 100 and 1200 degrees C, reductions in the thermal conductivity of NZP/VSZ composite coatings compared to YSZ-only coatings were traced to porosity effects. The NZP phase destabilized the t'-ZrO_2 phase of the YSZ, favoring the formation of t-ZrO_2, then m-ZrO_2, a phase with a high-thermal conductivity. Due to this phase change, a large hysteresis was observed in thermal conductivity during the initial heat-up and cool down cycles of the NZP containing samples.", "doi": "10.1016/S0921-5093(99)00468-2", "issn": "0921-5093", "publisher": "Elsevier", "publication": "Materials Science and Engineering A", "publication_date": "1999-11-30", "series_number": "2", "volume": "272", "issue": "2", "pages": "284-291" }, { "id": "authors:pt2pr-qnv32", "collection": "authors", "collection_id": "pt2pr-qnv32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181324717", "type": "article", "title": "Microstructural characterization of small-particle plasma spray coatings", "author": [ { "family_name": "de Arellano-L\u00f3pez", "given_name": "Antonio R.", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The microstructure of a small-particle plasma spray\n(SPPS) aluminum oxide coating sprayed onto a prepared\nmild steel substrate has been characterized using a variety\nof microscopic techniques as part of a process optimization\nstudy. The coating was highly conforming to the substrate\nas evidenced in high-resolution transmission electron microscopy,\nalthough some voids were present at the interface.\nThe layered splat microstructure, characteristic of\nconventional plasma-sprayed coatings but smaller in size,\nwas discerned in partially thinned samples in a focused-ion-\nbeam scanning electron microscope (FIB-SEM). Microcracks\nand microporosity, generally less than 0.5 \u03bcm in\nsize, was also seen between splats using transmission electron\nmicroscopy. Cubic alumina of the crystallographic\nform \u03b3-Al_2O_3 was identified by electron diffraction.", "doi": "10.1111/j.1151-2916.1999.tb02063.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1999-08", "series_number": "8", "volume": "82", "issue": "8", "pages": "2204-2208" }, { "id": "authors:1ewep-tb886", "collection": "authors", "collection_id": "1ewep-tb886", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181324822", "type": "article", "title": "Effects of loading rate on the fracture of cementitious materials", "author": [ { "family_name": "Tandon", "given_name": "S.", "clpid": "Tandon-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Cement paste, mortar, and concrete were studied to examine the influence of loading rate on operative toughening mechanisms. The fracture toughness of cement paste was found to be independent of crack length, while mortar and concrete exhibited strongly rising resistance curves. In the case of cement paste and mortar, the peak fracture toughness was found to be independent of the loading rate. Ln concrete, the peak toughness was found to decrease with increasing loading rate. Surface roughness measurements were performed to understand the effect of loading rate on the fracture mechanisms. The roughness analysis coupled with fractography were found to correlate with the toughness measurements.", "doi": "10.1016/S0008-8846(98)00223-3", "issn": "0008-8846", "publisher": "Elsevier", "publication": "Cement and Concrete Research", "publication_date": "1999-03", "series_number": "3", "volume": "29", "issue": "3", "pages": "397-406" }, { "id": "authors:6hs2z-vj604", "collection": "authors", "collection_id": "6hs2z-vj604", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181324926", "type": "book_section", "title": "Anisotropic small-angle neutron scattering studies of ceramics", "book_title": "Advanced materials for the 21st century : the 1999 Julia R. Weertman symposium", "author": [ { "family_name": "Allen", "given_name": "A. J.", "clpid": "Allen-A-J" }, { "family_name": "Fuller", "given_name": "E. R., Jr.", "clpid": "Fuller-E-R-Jr" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Zimmerman", "given_name": "M. H.", "clpid": "Zimmerman-M-H" }, { "family_name": "Wallace", "given_name": "J. S.", "clpid": "Wallace-J-S" } ], "contributor": [ { "family_name": "Chung", "given_name": "Yip-wah", "clpid": "Chung-Y-W" } ], "abstract": "This paper discusses how small-angle neutron scattering studies can be applied in two variations to obtain a representative characterization of the large, densely-populated, and anisotropic features that occur in the microstructures of various materials. The use of Pored scattering to amplify the anisotropies that are present, permitting different microstructural components to be identified, is discussed. Measurement of the anisotropic beam-broadening due to multiple small-angle neutron scattering is also described, as is its use to extract mean sizes and volume-fractions for the component microstructures. The work is illustrated by a small-angle scattering study of microcracking in a strongly textured anisotropic ceramic.", "isbn": "0873394550", "publisher": "TMS", "place_of_publication": "Warrendale, PA", "publication_date": "1999", "pages": "15-25" }, { "id": "authors:9z1ee-4ay18", "collection": "authors", "collection_id": "9z1ee-4ay18", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325031", "type": "book_section", "title": "Ceraset (TM) and Blackglas (TM) mini-tow composites with carbon-coated Nicalon (TM) tows", "book_title": "Advances in ceramic-matrix composites IV", "author": [ { "family_name": "Gonczy", "given_name": "S. T.", "clpid": "Gonczy-S-T" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Two commercially available preceramic polymers are the polyureasilazane Ceraset(TM) resin from DuPont Lanxide Composites and the polysiloxane Blackglas(TM) resin from AlliedSignal Inc. The Ceraset(TM) polymer pyrolyzes to a silicon carbonitride under nitrogen and a silicon carbide under argon. The Blackglas(TM) polymer produces a silicon oxycarbide under nitrogen or argon pyrolysis. Two groups of ceramic composites were made with the two preceramic polymer systems and single rows of carbon-coated ceramic grade Nicalon(TM) fiber, using 6 infiltration seeps and 1000\u00b0C argon pyrolysis. The mean tensile break loads for the two composite sets were equivalent -75 Newtons with coefficients of variation of 10-20% and obvious fiber pull-out. The break loads were independent of the matrix weight fraction, showing that the fibers are the dominant source of strength. There was no apparent difference in short term oxidation protection between the two types of matrix compositions, given the rapid oxidation of the pyrolytic carbon on the Nicalon(TM) fibers. Oxidation at 1000\u00b0C in air for one hour embrittled both sets of ceramic composites, reducing the mean break loads to 27 Newtons.", "isbn": "1574980599", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1999", "pages": "149-160" }, { "id": "authors:dafc1-bt037", "collection": "authors", "collection_id": "dafc1-bt037", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325151", "type": "article", "title": "The influence of loading rate on crack bridging processes in Al_2O_3", "author": [ { "family_name": "Tandon", "given_name": "S.", "clpid": "Tandon-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Commercially available alumina of 94% nominal purity was used to examine the influence of loading rate on toughening mechanisms. For fine-grained alumina, the crack resistance, K_R, was found to be independent of crack length and loading rate. Coarse-grained alumina exhibited strongly rising R-curves where the initial fracture toughness, K_0, was found to be independent of the loading rate. The net toughening, \u0394K_(SS), in coarse-grained alumina was found to decrease with increasing loading rate. Loading rate effects were independent of testing environment. A rate dependent coefficient of friction was incorporated into a crack bridging model to describe the effect of loading rate on toughness in this system. Predictions based on the bridging models, using the measured coefficients of friction for this material system, are in good agreement with the observed phenomenon.", "doi": "10.1016/S1359-6454(98)00023-8", "issn": "1359-6454", "publisher": "Elsevier", "publication": "Acta Materialia", "publication_date": "1998-06-12", "series_number": "10", "volume": "46", "issue": "10", "pages": "3547-3555" }, { "id": "authors:1mp8a-4tr22", "collection": "authors", "collection_id": "1mp8a-4tr22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325288", "type": "article", "title": "Effect of interface properties on microcracking of iron titanate", "author": [ { "family_name": "Saigal", "given_name": "Anil", "clpid": "Saigal-A" }, { "family_name": "Fuller", "given_name": "Edwin R., Jr.", "clpid": "Fuller-E-R-Jr" }, { "family_name": "Langer", "given_name": "Stephen A.", "clpid": "Lager-S-A" }, { "family_name": "Carter", "given_name": "W. Craig", "clpid": "Carter-W-C" }, { "family_name": "Zimmerman", "given_name": "Michael H.", "clpid": "Zimmerman-M-H" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The orthorhombic pseudobrookites have served as model material systems for investigating the role of thermal expansion anisotropy on the microcracking behavior in single phase ceramics. Among those typically studied are MgTi_2O_5, Fe_2TiO_5 and Al_2TiO_5. Fe_2TiO_5 is anisotropic in both thermal expansion and paramagnetic susceptibility. Fe_2TiO_5 has an orthorhombic crystal structure and belongs to the Bbmm space group. It belongs to the class of titanates under investigation as second-phase toughness enhancers and as coatings for engine manifolds. The coefficient of thermal expansion of Fe_2TiO_5 is 10.1 \u00d7 10^(\u22126) K^(\u22121), 16.3 \u00d7 10^(\u22126) K^(\u22121) and 0.6 \u00d7 10^(\u22126) K^(\u22121) in the a, b and c directions, respectively. The goal of the present work is to examine residual stresses and study the effect of interface properties on fracture and propensity toward microcracking of Fe_2TiO_5 using finite element analysis.", "doi": "10.1016/S1359-6462(98)00040-2", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "1998-04-03", "series_number": "9", "volume": "38", "issue": "9", "pages": "1449-1453" }, { "id": "authors:b2nkr-b7t72", "collection": "authors", "collection_id": "b2nkr-b7t72", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140919-144228367", "type": "book_section", "title": "Comparison of Focused Ion Beam and Conventional Techniques on TEM Specimen Preparation of Metal-Ceramic Interfaces", "author": [ { "family_name": "de Arellano L\u00f3pez", "given_name": "A. Ramirez", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Chiou", "given_name": "W.-A.", "clpid": "Chiou-W-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The results of TEM analyses of materials are critically dependent on the quality of the sample\nprepared. Although numerous techniques have been developed in the last two decades, differential\nthinning of inhomogeneous materials remains a serious problem. Recently, focused ion beam (FIB)\ntechnique has been introduced for cross-sectional sample preparation for TEM and SEM. \nA novel system for depositing a fine-grain (~200 nm) ceramic coating on a metal surface via\na patent pending Small-Particle Plasma Spray (SPPS) technique has been developed at the Basic\nIndustry Research Laboratory of Northwestern University. To understand the properties of the\ncoated surface, the ceramic/metal interface and the microstructure of the ceramic coating must be\ninvestigated. This paper presents a comparison of the microstructure of an Al_2O_3 coating on a mild\nsteel substrate prepared using conventional and FIB techniques.", "publisher": "San Francisco Press", "publication_date": "1998" }, { "id": "authors:hsth4-2cm12", "collection": "authors", "collection_id": "hsth4-2cm12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140923-163358533", "type": "book_section", "title": "Morfolog\u00eda Granular y Microestructura de Recubrimientos Cer\u00e1micos de Grano Fino Proyectados Por Plasma (Spps)", "book_title": "VI Congreso Nacional Propiedades Mec\u00e1nicas de S\u00f3lidos", "author": [ { "family_name": "de Arellano L\u00f3pez", "given_name": "A. R.", "clpid": "de-Arellano-L\u00f3pez-A-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Pajares Vicente", "given_name": "Anonia", "clpid": "Pajares-Vicente-A" }, { "family_name": "Cumbrera Hern\u00e1ndez", "given_name": "Francisco Luis", "clpid": "Cumbrera-Hern\u00e1ndez-F-L" }, { "family_name": "GuibertauCabanillas", "given_name": "Fernando", "clpid": "GuibertauCabanillas-F" } ], "isbn": "8484977447", "publisher": "Universidad de Extramadura", "place_of_publication": "Badajaoz, Spain", "publication_date": "1998", "pages": "234-240" }, { "id": "authors:h7xy0-9db62", "collection": "authors", "collection_id": "h7xy0-9db62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325422", "type": "book_section", "title": "Strength and stability studies on mini-tow ceramic composites made with nitrided Nextel (TM) 312 fibers and silicon oxycarbide", "book_title": "22nd Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A", "author": [ { "family_name": "Gonczy", "given_name": "S. T.", "clpid": "Gonczy-S-T" }, { "family_name": "Oba", "given_name": "K.", "clpid": "Oba-K" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Bray", "given_name": "Don", "clpid": "Bray-D" } ], "abstract": "Nitridation of Nextel(TM) 312 alumino-borosilicate fibers produces a boron-nitride-rich surface layer which acts as a debond layer in ceramic composites. This interface-fiber system offers a low cost alternative to CVD deposition of coatings on alumina and silicon carbide fibers. Ceramic fiber composites were made with 6 infiltration/pyrolysis cycles of a nitrided multifilament Nextel(TM) 312 mini-tow, using Blackglas(TM) resin to produce a silicon oxycarbide matrix. In the as-prepared condition the Nextel-Blackglas(TM) mini-tow composites had a mean tensile breaking load of 53 Newtons, a coefficient of variation of 26%, and limited fiber pull-out. The Nextel(TM) composites were then heat-treated in air at 600\u00b0, 800\u00b0, and 1000\u00b0C to determine oxidation stability. After 600\u00b0C oxidation for 200 hours, the Blackglas(TM) Nextel(TM) composites retained 75% of the as-prepared tensile break load with a fibrous fracture surface. Oxidation for 24 hours at 1000\u00b0C and for 100 hours at 800\u00b0C reduced the retained tensile breaking load by 47% and 66% respectively, showing reduced strain-to-failure and distinct embrittlement of the composite.", "doi": "10.1002/9780470294482.ch17", "isbn": "9780470375587", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1998", "pages": "147-154" }, { "id": "authors:ynh8q-36r45", "collection": "authors", "collection_id": "ynh8q-36r45", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325539", "type": "article", "title": "Forming tough, single phase laminates of Fe_2TiO_5 via magnetic-assisted gelcasting", "author": [ { "family_name": "Baskin", "given_name": "Donald M.", "clpid": "Baskin-D-M" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Ohtsuka", "given_name": "Hideyuki", "clpid": "Ohtsuka-H" } ], "abstract": "Single phase laminates of iron titanate were formed by gelcasting both in the presence and absence of a magnetic field to produce alternating layers of textured and non-textured microstructure, respectively. X-ray analysis was performed on each lamina verifying that alignment was maintained throughout processing. Toughness of trilayer laminates (non-textured/textured/non-textured) were measured using a modified version of the short double cantilever beam geometry. Toughness experiments resulted in large scale crack deflection of several hundred microns. Peak toughnesses were measured to be well over 8 MPa\u2022m^(1/2) which is a substantial improvement over monolithic iron titanate.", "issn": "0021-4876", "publisher": "Japan Institute of Metals", "publication": "Journal of the Japan Institute of Metals", "publication_date": "1997-12", "series_number": "12", "volume": "61", "issue": "12", "pages": "1306-1310" }, { "id": "authors:w57k0-2x320", "collection": "authors", "collection_id": "w57k0-2x320", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325647", "type": "article", "title": "Forming single-phase laminates via the gelcasting technique", "author": [ { "family_name": "Baskin", "given_name": "Donald M.", "clpid": "Baskin-D-M" }, { "family_name": "Zimmerman", "given_name": "Michael H.", "clpid": "Zimmerman-M-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fuller", "given_name": "Edwin R., Jr.", "clpid": "Fuller-E-R-Jr" } ], "abstract": "Single-phase laminates of iron titanate were formed by gel-casting in both the presence and absence of a magnetic field to produce alternating layers of textured and nontextured microstructure, respectively. X-ray analysis was performed on each lamina verifying that alignment was maintained throughout processing. Tunnel cracks were found in trilayer laminates (nontextured/textured/nontextured) when the alignment direction was parallel to the interface between layers. The cracks are consistent with a stress profile of residual tension parallel to the interface in the textured layer.", "doi": "10.1111/j.1151-2916.1997.tb03213.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1997-11", "series_number": "11", "volume": "80", "issue": "11", "pages": "2929-2932" }, { "id": "authors:ey572-1hj22", "collection": "authors", "collection_id": "ey572-1hj22", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325775", "type": "article", "title": "Forming textured microstructures via the gelcasting technique", "author": [ { "family_name": "Zimmerman", "given_name": "Michael H.", "clpid": "Zimmerman-M-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fuller", "given_name": "Edwin R., Jr.", "clpid": "Fuller-E-R-Jr" } ], "abstract": "Crystallographically textured samples of iron titanate were produced by gelcasting in the presence of a strong magnetic field. Texture was assessed by measuring X-ray pole figures on samples that were cast in different orientations relative to the applied field. Specimens in this study exhibit fiber-type texture, with the b-axes aligned parallel to the applied field. Peak texture strengths were on the order of 3 and 48 multiples of a random distribution (MRD) when processed in a 3.2 and 8.4 T magnetic field, respectively. This study shows that a combination of gelcasting with magnetic-field-assisted processing provides a convenient method for fabricating samples which can be used to study the role of crystallographic texture on the physical properties of polycrystalline ceramics, e.g., their elastic or fracture behavior.", "doi": "10.1111/j.1151-2916.1997.tb03184.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1997-10", "series_number": "10", "volume": "80", "issue": "10", "pages": "2725-2729" }, { "id": "authors:q14my-1wc29", "collection": "authors", "collection_id": "q14my-1wc29", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326168", "type": "article", "title": "Ceramic composite interfaces: Properties and design", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Optimal design of the fiber-matrix interface in ceramic-matrix composites is the key to achieving desired composite performance. In this paper the interface-controlling parameters are described. Techniques for measuring interfacial properties are reported. Examples of interface design of both oxide and non-oxide types are illustrated.", "doi": "10.1146/annurev.matsci.27.1.499", "issn": "0084-6600", "publisher": "Annual Reviews", "publication": "Annual Review of Materials Science", "publication_date": "1997-08", "volume": "27", "pages": "499-524" }, { "id": "authors:7p4hm-ky557", "collection": "authors", "collection_id": "7p4hm-ky557", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140707-163033253", "type": "article", "title": "Controlled symmetry breaking in superconducting UPt_3", "author": [ { "family_name": "Jin", "given_name": "D. S.", "clpid": "Jin-D-S" }, { "family_name": "Husmann", "given_name": "A.", "clpid": "Husmann-A" }, { "family_name": "Rosenbaum", "given_name": "T. F.", "orcid": "0009-0008-6152-666X", "clpid": "Rosenbaum-T-F" }, { "family_name": "Steyer", "given_name": "T. E.", "clpid": "Steyer-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "We have developed a biaxial-stress calorimeter for use at milli-Kelvin temperatures to study the nature of the double superconducting transition in single crystal UPt_3. We suppress the basal-plane antiferromagnetism and merge the two transitions through c-axis stress, and then break the hexagonal symmetry of the basal plane in a regulated manner through stress along \u00e2. We recover a double superconducting transition, but with a shift in the relative sizes of the specific heat jumps for the upper and lower transitions, as well as a different measure of the strength of the symmetry-breaking field.", "doi": "10.1103/PhysRevLett.78.1775", "issn": "0031-9007", "publisher": "American Physical Society", "publication": "Physical Review Letters", "publication_date": "1997-03-03", "series_number": "9", "volume": "78", "issue": "9", "pages": "1775-1778" }, { "id": "authors:gdpnr-shq70", "collection": "authors", "collection_id": "gdpnr-shq70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181325896", "type": "article", "title": "High temperature stability and thermal expansion behavior of molybdenum-chromium M_2C carbides", "author": [ { "family_name": "Knepfler", "given_name": "C. A.", "clpid": "Knepfler-C-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Weertman", "given_name": "J.", "clpid": "Weertman-J" }, { "family_name": "Olson", "given_name": "G. B.", "clpid": "Olson-G-B" }, { "family_name": "Hubbard", "given_name": "C. R.", "clpid": "Hubbard-C-R" }, { "family_name": "Cavin", "given_name": "O. B.", "clpid": "Cavin-O-B" }, { "family_name": "Packen", "given_name": "N.", "clpid": "Packen-N" } ], "abstract": "The thermal expansion of molybdenum-chromium M_2C carbides has been studied over the temperature range from room temperature to 900\u00b0C using high-temperature X-ray diffraction. Hyperstoichiometric carbides demonstrated hysteretic thermal expansion/contraction as excess carbon was lost upon heating above 750\u00b0C in an inert environment. Coefficients of thermal expansion of both the a and c axes increase linearly with chromium content.", "doi": "10.1016/S0925-8388(96)02442-5", "issn": "0925-8388", "publisher": "Elsevier", "publication": "Journal of Alloys and Compounds", "publication_date": "1997-02-15", "series_number": "1-2", "volume": "248", "issue": "1-2", "pages": "139-142" }, { "id": "authors:5mb9v-awh39", "collection": "authors", "collection_id": "5mb9v-awh39", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326057", "type": "article", "title": "Cyclic fatigue of reaction-bonded silicon nitride at elevated temperatures", "author": [ { "family_name": "Christensen", "given_name": "R. J.", "clpid": "Christensen-R-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Cyclic and static loading tests were performed on reaction-bonded silicon nitride from 1000\u20131400 \u00b0C in air. This porous, fine-grained material contained no glassy grain-boundary phase and exhibited no slow crack growth at room temperature. Under cyclic loading, the crack-growth behaviour at 1000 \u00b0C was similar to room-temperature results; however, at 1200 and 1400 \u00b0C crack-growth rates increased significantly. Under static loading, significant crack growth was detected at 1000 \u00b0C and increased with temperature. Most of the crack growth under cyclic loading was attributed to slow crack-growth mechanisms, but evidence of cyclic crack-growth mechanisms were also observed. Oxidation played a major role in crack-growth velocity at high temperature.", "doi": "10.1023/A:1018509902025", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "1997-02", "series_number": "4", "volume": "32", "issue": "4", "pages": "949-955" }, { "id": "authors:r420s-hb568", "collection": "authors", "collection_id": "r420s-hb568", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326284", "type": "article", "title": "Fracture energy of glass-alumina interfaces via the bimaterial bend test", "author": [ { "family_name": "Cazzato", "given_name": "Anthony", "clpid": "Cazzato-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The fracture energies of glass-alumina interfaces mere measured using the bimaterial bend test. These experiments comprise one of the few studies in which the bimaterial bend test has been applied to an all-ceramic materials system. The experiment was used to evaluate the effect of materials purity, processing and environmental conditions on the interface toughness, Changes in interface fracture energy were measured as a function of glass content, interface roughness, phase angle, and testing atmosphere. Alumina glass content and testing atmosphere had the greatest effect on the interface toughness and the overall mechanical behavior of the composite, The effect of phase angle of loading on the interface fracture energy was assessed over several degrees by varying the relative heights of the two layers. The results from these interface fracture experiments offer insight into the fracture behavior of multiphase and composite ceramics where deflection of cracks at bimaterial interfaces is an important concern.", "doi": "10.1111/j.1151-2916.1997.tb02808.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1997-01", "series_number": "1", "volume": "80", "issue": "1", "pages": "181-188" }, { "id": "authors:9rezm-9vm44", "collection": "authors", "collection_id": "9rezm-9vm44", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140912-114830027", "type": "book_section", "title": "Tensile Tests of Miniature Fiber Reinforced Ceramic Composites for Screening Process-Property Relations", "book_title": "Proceedings of the 21st Annual Conference on Composites, Advanced Ceramics, Materials, and Structures: A", "author": [ { "family_name": "Gonczy", "given_name": "S. T.", "clpid": "Gonczy-S-T" }, { "family_name": "Sprandel", "given_name": "R. C.", "clpid": "Sprandel-R-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Singh", "given_name": "J. P.", "clpid": "Singh-J-P" } ], "abstract": "Mechanical testing of 2-D and 3-D composites in bar geometries is material, time, and cost intensive. As an alternative low-cost, rapid-fabrication geometry, multifilament Nicalon\u2122 (with pyrolytic carbon-coating) tows were densified with the preceramic polymer (Blackglas\u2122) technology to form single tow ceramic \"mini-composites\". Using modified ASTM tow testing methods, the Blackglas-Nicalon(C) mini-composites were tested in tension at ambient temperatures. The ceramic mini-composites had fibrous failure with linear load-deflection curves and mean breaking loads of 70 N. Gage length (1, 2.5 & 5 cm) effects on breaking loads were minimal. The coefficient of variation (CoV) for the ceramic mini-composites was 19% as compared to a 10% CoV for earlier tensile tests on Blackglas-Nicalon 2-D fabric composite bars. Results were compared to tensile tests of epoxy-Nicalon tows. Breaking strengths of the ceramic mini-composites were roughly 30% of the breaking strengths of the epoxy-Nicalon composites. Oxidation at 600\u00b0 and 1000\u00b0C for 1 hour embrittled the Blackglas-Nicalon (C) composites and reduced the breaking load to values of 42 N and 17 N, respectively.", "doi": "10.1002/9780470294437.ch79", "isbn": "9780470375495", "publisher": "Wiley", "place_of_publication": "Hoboken, NJ", "publication_date": "1997", "pages": "729-736" }, { "id": "authors:jzqcg-6pj24", "collection": "authors", "collection_id": "jzqcg-6pj24", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326397", "type": "article", "title": "Residual stress in ceramics with large thermal expansion anisotropy", "author": [ { "family_name": "Paulik", "given_name": "S. W.", "clpid": "Paulik-S-W" }, { "family_name": "Zimmerman", "given_name": "M. H.", "clpid": "Zimmerman-M-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fuller", "given_name": "E. R., Jr.", "clpid": "Fuller-E-R-Jr" } ], "abstract": "Residual stress was measured in sintered and heat-treated Fe_2TiO_5 samples with various grain sizes. The influence of texturing was assessed by comparing the residual stress states of samples having randomly oriented grains and highly oriented grains produced through magnetically assisted processing. The residual stress was measured with x-ray diffraction using Cr K_\u03b1 radiation. Due to the significant texture and the consequential oscillations in the d_(\u03c6\u03c8) vs sin^2 \u03c8 data, the residual stress was calculated using the Marion-Cohen method. Textured samples showed significantly lower residual stresses except when spontaneous microcracking accompanied grain growth in the randomly oriented systems. Elastic modulus measurements showed a direct correlation between the decrease in residual stress and the microcrack density.", "doi": "10.1557/JMR.1996.0354", "issn": "0884-2914", "publisher": "Materials Research Society", "publication": "Journal of Materials Research", "publication_date": "1996-11", "series_number": "11", "volume": "11", "issue": "11", "pages": "2795-2803" }, { "id": "authors:zr8ke-7aa90", "collection": "authors", "collection_id": "zr8ke-7aa90", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326507", "type": "article", "title": "Texture assessment of magnetically processed iron titanate", "author": [ { "family_name": "Zimmerman", "given_name": "Michael H.", "clpid": "Zimmerman-M-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fuller", "given_name": "Edwin R., Jr.", "clpid": "Fuller-E-R-Jr" }, { "family_name": "Kruger", "given_name": "Keith L.", "clpid": "Kruger-K-L" }, { "family_name": "Bowman", "given_name": "Keith J.", "clpid": "Bowman-K-J" } ], "abstract": "Untextured and highly textured iron titanate specimens were produced by vacuum filtering iron titanate-ethanol suspensions in the absence and presence of a strong magnetic field, respectively, Crystallographic texture was assessed by measuring X-ray pole figures on surfaces parallel and perpendicular to the field direction for several peaks in each system, Morphological texture was assessed by measuring grain size as a function of angle to a reference direction, Results indicate that magnetic field processing imposes a strong, fiber-type texture on the order of 30 times random, with the b-axis parallel to the applied field, Additionally, morphological texturing is absent for the grain sizes studied in this work.", "doi": "10.1111/j.1151-2916.1996.tb08600.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1996-05", "series_number": "5", "volume": "79", "issue": "5", "pages": "1389-1393" }, { "id": "authors:mwdnj-eh093", "collection": "authors", "collection_id": "mwdnj-eh093", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326649", "type": "article", "title": "Damage tolerance of silicon carbide- and alumina-matrix surface composites", "author": [ { "family_name": "Day", "given_name": "P. S.", "clpid": "Day-P-S" }, { "family_name": "Skamser", "given_name": "D. J.", "clpid": "Skamser-D-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Jennings", "given_name": "H. M.", "clpid": "Jennings-H-M" }, { "family_name": "Johnson", "given_name": "D. Lynn", "clpid": "Johnson-D-L" } ], "abstract": "A method for the fabrication of a ceramic-matrix composite (CMC) layer on the surface of a monolithic substrate via chemical vapor infiltration (CVI) is described. Preforms consisted of tows of fibers wound onto the surface of monolithic cylindrical tubes. Nicalon fibers were wound onto mullite substrates and infiltrated with \u03b2-SiC from CH_3SiCl_3/H_2 gas mixtures in a cylindrical cold-wall reactor. Similarly, Nextel fibers were wound onto A1_2O_3 substrates and infiltrated with \u03b1-Al_2O_3 from AlCl_3/H_2/CO_2/N_2 gas mixtures. Composites with densities as high as 88% of the theoretical value were fabricated in 8 h. The effective fracture strength of the SiC- and Al_2O_3-matrix surface composites, as determined from diametral compression tests of C-ring specimens, was found to be insensitive to damage caused to the outer diameter by a Vickers indentation. The tolerance of the SiC-matrix surface composites to surface damage was retained in specimens subjected to oxidation at 1000\u00b0C for 6 h.", "doi": "10.1111/j.1151-2916.1996.tb08558.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1996-04", "series_number": "4", "volume": "79", "issue": "4", "pages": "1117-1120" }, { "id": "authors:nzz08-q0g95", "collection": "authors", "collection_id": "nzz08-q0g95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326751", "type": "article", "title": "On loading rate effects in toughening processes", "author": [ { "family_name": "Tandon", "given_name": "S.", "clpid": "Tandon-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Environmental crack tip reactions are a known source of premature fracture in oxides. These rate-dependent\nphenomena commonly are studied in strength tests where loading rate serves as the major\nexperimental variable. A material susceptible to environmentally-assisted crack growth is stronger at fast\ntesting rates. A topic which has received far less attention is the influence of stressing rate or loading rate\non the shielding processes which occur at some distance from the crack tip, although the inverse has been\nstudied by Deuerler et al. In their work, the crack velocity-stress intensity, v-K, curve was measured\nas a function of crack length in alumina. The v-K curve shifted to higher stress intensities for longer\ncracks, indicative of greater shielding as the crack grew progressively up the K_R (resistance) curve. In this\npaper, we explore the influence of loading rate on the fracture toughness of two aluminum oxides, one\nwhich fails in a brittle fashion (i.e., where toughness is independent of crack length), and a second which\ndemonstrates significant resistance curve behavior due to grain bridging behind the crack tip. We present\nhere the first known documentation of a loading rate effect on shielding phenomena in ceramic materials.", "doi": "10.1016/1359-6462(95)00586-2", "issn": "1359-6462", "publisher": "Elsevier", "publication": "Scripta Materialia", "publication_date": "1996-03-01", "series_number": "5", "volume": "34", "issue": "5", "pages": "757-762" }, { "id": "authors:0vw0n-dj616", "collection": "authors", "collection_id": "0vw0n-dj616", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326842", "type": "article", "title": "Room-Temperature Cyclic Fatigue of Reaction-Bonded Silicon Nitride Using the Double Cleavage Drilled Compression Specimen", "author": [ { "family_name": "Christensen", "given_name": "Renee J.", "clpid": "Christensen-R-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The double cleavage drilled compression specimen was used to study the room-temperature cyclic fatigue behavior of reaction-bonded silicon nitride (RBSN). Fatigue results were compared with slow crack growth under static loading. The fatigue exponent for RBSN was found to be 40, although no slow crack growth occurred under static loading. The fatigue threshold for RBSN was as low as 0.5/K_(lc) and dependent upon loading conditions. Crack growth behavior and electron microscopy provided evidence that the fatigue mechanism was due to asperity and debris wedging at the crack face.", "doi": "10.1111/j.1151-2916.1996.tb08139.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1996-02", "series_number": "2", "volume": "79", "issue": "2", "pages": "425-429" }, { "id": "authors:6byar-9aa92", "collection": "authors", "collection_id": "6byar-9aa92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181326961", "type": "article", "title": "Cohesive crack modeling of influence of sudden changes in loading rate on concrete fracture", "author": [ { "family_name": "Tandon", "given_name": "S.", "clpid": "Tandon-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Ba\u017eant", "given_name": "Zden\u011bk P.", "clpid": "Ba\u017eant-Z-P" }, { "family_name": "Li", "given_name": "Yuan N.", "clpid": "Li-Y-N" } ], "abstract": "The results of an experimental study of a sudden change in loading rate on the fracture behavior of normal- and high-strength concrete specimens of three different sizes are reported. Geometrically similar three-point bend specimens were subjected to either a sudden 1000-fold increase or a 10-fold decrease of the loading rate. It was observed that for a large increase of the loading rate, the post-peak softening can be reversed to hardening followed by a second peak of the stress-strain diagram. A sudden decrease of the loading rate initially causes, a steeper softening slope of this diagram. The results are similar for normal and high strength concrete specimens. The viscoelastic cohesive crack model with the rate-dependent softening law is used to model the experimental results.", "doi": "10.1016/0013-7944(95)00080-F", "issn": "0013-7944", "publisher": "Elsevier", "publication": "Engineering Fracture Mechanics", "publication_date": "1995-12", "series_number": "6", "volume": "52", "issue": "6", "pages": "987-997" }, { "id": "authors:6ptw9-r6x10", "collection": "authors", "collection_id": "6ptw9-r6x10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181327118", "type": "article", "title": "Mechanical Behavior of Alumina Reinforced with Carbon-Coated Silicon Carbide Whiskers", "author": [ { "family_name": "Steyer", "given_name": "Todd E.", "clpid": "Steyer-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "SiC whiskers with 0, 20, and 50 \u00c5 carbon coatings were incorporated into an alumina matrix to modify residual thermal stress and interfacial bonding. Composites were characterized using triaxial X-ray diffraction for residual stress determination and electron microscopy to explore interfacial chemistry. Fracture toughness and R-curve behavior were examined for short and long crack lengths. Uncoated SiC whiskers optimized strength, fracture toughness, and R-curve behavior of these composites. A graphite interphase at the whisker/matrix interface decreased contributions to crack bridging without promoting additional toughening by whisker pullout.", "doi": "10.1111/j.1151-2916.1995.tb08039.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1995-10", "series_number": "10", "volume": "78", "issue": "10", "pages": "2673-2679" }, { "id": "authors:m1rgq-zdf98", "collection": "authors", "collection_id": "m1rgq-zdf98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181327215", "type": "article", "title": "Fracture strength of free\u2010standing chemically vapor\u2010deposited diamond films", "author": [ { "family_name": "Steyer", "given_name": "Todd E.", "clpid": "Steyer-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Drory", "given_name": "Michael D.", "clpid": "Drory-M-D" } ], "abstract": "The fracture strength of free\u2010standing chemically vapor\u2010deposited diamond films was assessed by four\u2010point bending. A two\u2010parameter Weibull analysis was performed on 130 \u03bcm thick films resulting in a Weibull modulus of 4.3 and a statistical scaling stress of 626 MPa. The residual stress in films was measured from the free\u2010standing film curvature to be 384\u00b110 MPa. The fracture surface chemistry was examined using scanning Auger spectroscopy. The fracture did not occur preferentially along grain boundaries.", "doi": "10.1063/1.113617", "issn": "0003-6951", "publisher": "American Institute of Physics", "publication": "Applied Physics Letters", "publication_date": "1995-06-05", "series_number": "23", "volume": "66", "issue": "23", "pages": "3105-3107" }, { "id": "authors:ey7e1-wcy95", "collection": "authors", "collection_id": "ey7e1-wcy95", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181327414", "type": "article", "title": "Tensile Behavior of Microcracking SiC-TiB_2 Composites", "author": [ { "family_name": "Gu", "given_name": "W.-H.", "clpid": "Gu-W-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The stress-strain behavior of microcracking SIC-TIB_2 composites was studied using uniaxial tensile tests. The nonlinear stress-strain behavior provided the critical stresses for microcracking (defined as the proportional limit) and the magnitude of residual strain release as a consequence of stress-induced microcracking. The release of residual strain was confirmed using the loading-unloading process. Both the critical stress for the nonlinear stress-strain curve and the release of residual strain mere used to establish the maximum principal stress as the stress criterion for microcracking.", "doi": "10.1111/j.1151-2916.1995.tb08845.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1995-06", "series_number": "6", "volume": "78", "issue": "6", "pages": "1507-1512" }, { "id": "authors:1k2qf-72921", "collection": "authors", "collection_id": "1k2qf-72921", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181327859", "type": "article", "title": "Interfacial debonding and sliding in brittle-matrix composites measured using an improved fiber pullout technique", "author": [ { "family_name": "Mumm", "given_name": "D. R.", "clpid": "Mumm-D-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A modified fiber pullout technique has been developed which allows direct experimental evaluation of the force-displacement relation for a crack-bridging fiber. The technique allows a continuous, accurate measurement of stable, progressive interfacial debonding and frictional sliding. Coupled with an appropriate analysis, the test provides a quantitative determination of interfacial properties relevant to the toughening of brittle materials through fiber-reinforcement. The technique has been used to measure interfacial debonding and sliding in three SiC fiber/glass composite systems. The fibers differ primarily in diameter and surface roughness characteristics allowing a unique evaluation of the effects of these parameters. The results indicate that fiber surface roughness plays a significant role in the interfacial debonding and sliding behavior. Load fluctuations observed during both monotonic and cyclic loading are explained by invoking the concept of asperity-asperity interaction during sliding at a rough interface.", "doi": "10.1016/0956-7151(94)00294-R", "issn": "0956-7151", "publisher": "Elsevier", "publication": "Acta Metallurgica et Materialia", "publication_date": "1995-03", "series_number": "3", "volume": "43", "issue": "3", "pages": "1259-1270" }, { "id": "authors:hsgzg-dkw04", "collection": "authors", "collection_id": "hsgzg-dkw04", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181327973", "type": "article", "title": "Softening Reversal and Other Effects of a Change in Loading Rate on Fracture of Concrete", "author": [ { "family_name": "Ba\u017eant", "given_name": "Zden\u011bk P.", "clpid": "Ba\u017eant-Z-P" }, { "family_name": "Gu", "given_name": "Wei-Hwa", "clpid": "Gu-W-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The time dependence of concrete fracture, and particularly the effect of loading rate, has so far been studied mainly in the dynamic range. The present study extends a preceding investigation of the rate effect in the static range that covered times to peak from 1 to 300,000 sec. Geometrically similar three-point-bend specimens of three different sizes are subjected to either a sudden 1000-fold increase of the loading rate or a 10-fold sudden decrease of the loading rate. It is found that the post-peak softening can be reversed to hardening, followed by a second load peak that can be either higher or lower than the previous load peak. The rise to the second peak depends on the previous post-peak load drop from the first peak load. A sudden decrease in the loading rate causes initially a steeper softening slope. The source of these time-dependent effects appears to be not only the thermally activated nature of the process of bond ruptures in the fracture process zone but also the effect of creep, both a nonlinear creep in the fracture process zone and a linear creep in the bulk of the specimen. The results of this study and a previous study suggest that there is a significant difference in fracture behavior for short-time and long-time loads. The phenomena observed are of interest, for example, for the analysis of concrete dams with cracks that evolve over many years. Mathematical modeling of the present test results is left for a subsequent study.", "doi": "10.14359/1171", "issn": "0889-325X", "publisher": "American Concrete Institute", "publication": "ACI Materials Journal", "publication_date": "1995-01", "series_number": "1", "volume": "92", "issue": "1", "pages": "3-9" }, { "id": "authors:0jyg3-xqt19", "collection": "authors", "collection_id": "0jyg3-xqt19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328107", "type": "book_section", "title": "Crack stability in the fracture of cementitious materials", "book_title": "Microstructure of Cement-Based Systems/Bonding and Interfaces in Cementitious Materials", "author": [ { "family_name": "Tandon", "given_name": "S.", "clpid": "Tandon-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Bazant", "given_name": "Z. P.", "clpid": "Ba\u017eant-Z-P" } ], "contributor": [ { "family_name": "Diamond", "given_name": "S.", "clpid": "Diamond-S" }, { "family_name": "Glasser", "given_name": "F. P.", "clpid": "Glasser-F-P" }, { "family_name": "Mindess", "given_name": "S.", "clpid": "Mindess-S" }, { "family_name": "Roberts", "given_name": "L. R.", "clpid": "Roberts-L-R" }, { "family_name": "Skalny", "given_name": "J. P.", "clpid": "Skalny-J-P" } ], "abstract": "The aim of the present study is to investigate the stability of crack propagation in cementitious materials. Tests were conducted on bend specimens in three-point and four-point loading conditions. Three-point bend specimens showed stable crack growth for mortar, normal strength and high strength concrete specimens. Alternatively, four-point bend specimens showed catastrophic failure for mortar and quasi-catastrophic failure for normal strength and high strength concrete specimens. Results will be discussed in relation to brittleness number model and specific microstructural features including the interfacial transition zone between the cement paste and the aggregate and the attendant toughening mechanisms.", "doi": "10.1557/PROC-370-387", "isbn": "1558992723", "publisher": "Materials Research Society", "place_of_publication": "Pittsburgh, PA", "publication_date": "1995", "pages": "387-396" }, { "id": "authors:6cxbk-rqh74", "collection": "authors", "collection_id": "6cxbk-rqh74", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328349", "type": "book_section", "title": "Interface Design in Brittle-Brittle Systems", "book_title": "High Performance Composites: Commonalty of Phenomena", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Mumm", "given_name": "Daniel R.", "clpid": "Mumm-D-R" } ], "contributor": [ { "family_name": "Chawla", "given_name": "K. K.", "clpid": "Chawla-K-K" }, { "family_name": "Liaw", "given_name": "P. K.", "clpid": "Liaw-P-K" }, { "family_name": "Fishman", "given_name": "Steven G.", "clpid": "Fishman-S-G" } ], "abstract": "In brittle matrix composites both ceramic, intermetallic, and cement-based, design of the fiber-matrix\ninterface is key to achieving high composite toughness. In this paper we explore first, a\nmethod for accurately determining interfacial properties and second, the influence of physical\nand chemical aspects of the fiber-matrix interface which influence fracture toughness of the\ncomposite. \n\nA modified fiber pullout technique has been developed which allows direct experimental\nevaluation of the force-displacement relation for a crack bridging fiber. The technique allows\ncontinuous, accurate measurement of stable, progressive debonding and frictional sliding. \n\nCoupled with an appropriate analysis, the test provides a quantitative determination of\ninterfacial properties relevant to the toughening of brittle materials.\nAmong the parameters of influence in determining interfacial properties, and consequently,\ncomposite toughness, are interface toughness, surface roughness, residual stress state, and\ncoefficient of friction. Each of these can be altered by use of coatings or surface modifications.\nExamples of each will be reviewed in a variety of brittle systems.", "isbn": "0873392477", "publisher": "Minerals, Metals & Materials Society", "place_of_publication": "Warrendale, PA", "publication_date": "1994-10", "pages": "131-142" }, { "id": "authors:1fmz7-x1097", "collection": "authors", "collection_id": "1fmz7-x1097", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328464", "type": "book_section", "title": "Effects of Reinforcement Surface Morphology on Toughening of Brittle-Matrix Composites", "book_title": "High Performance Composites: Commonalty of Phenomena", "author": [ { "family_name": "Mumm", "given_name": "Daniel R.", "clpid": "Mumm-D-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Chawla", "given_name": "K. K.", "clpid": "Chawla-K-K" }, { "family_name": "Liaw", "given_name": "P. K.", "clpid": "Liaw-P-K" }, { "family_name": "Fishman", "given_name": "Steven G.", "clpid": "Fishman-S-G" } ], "abstract": "The mechanical properties of brittle-matrix composites critically depend upon the nature of the\nreinforcement/matrix interface. Recent theoretical and experimental work has shown that the\nmorphology of the reinforcement surface can play a dominant role in determining the toughening\nbehavior in these materials. In this work, the role of reinforcement surface roughness is\nexamined both analytically and experimentally. Measurements of the debonding and frictional\nsliding of rough fibers in glass matrices, obtained using a modified fiber pullout technique, show\na significant dependence on fiber surface roughness. The effects of surface roughness are\nexplored further by measuring systematic changes in the fiber sliding behavior with controlled\nfiber coatings. The available analytical models of rough fiber sliding are examined to interpret\nthe experimental results.", "isbn": "0873392477", "publisher": "Minerals, Metals & Materials Society", "place_of_publication": "Warrendale, PA", "publication_date": "1994-10", "pages": "181-192" }, { "id": "authors:yvfaz-kk141", "collection": "authors", "collection_id": "yvfaz-kk141", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328225", "type": "article", "title": "Development of Textured Microstructures in Ceramics with Large Thermal Expansion Anisotropy", "author": [ { "family_name": "Paulik", "given_name": "Steven W.", "clpid": "Paulik-S-W" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fuller", "given_name": "Edwin R., Jr.", "clpid": "Fuller-E-R-Jr" } ], "abstract": "Fe_2TiO_5 exhibits a high degree of anisotropy in both thermal expansion and paramagnetic susceptibility. Anisotropy in paramagnetic susceptibility allows textured microstructures to be produced using magnetically-assisted grain alignment during sample fabrication. The resulting solid-state sintered aligned samples had a b-axis orientation coefficient of 3.33 (vs 6.60 for an aligned powder\u2013epoxy suspension) where an orientation coefficient of 1 represents a randomly-oriented sample. This texturing reduced the residual stresses generated from the large thermal expansion anisotropy of the control samples, as evidenced by reduced microcracking and morphological texturing of the aligned microstructure.", "doi": "10.1111/j.1151-2916.1994.tb07014.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1994-02", "series_number": "2", "volume": "77", "issue": "2", "pages": "454-458" }, { "id": "authors:82f2t-hym02", "collection": "authors", "collection_id": "82f2t-hym02", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328570", "type": "article", "title": "X-ray residual stress analysis of a ceramic thermal barrier coating undergoing thermal cycling", "author": [ { "family_name": "Jordan", "given_name": "D. W.", "clpid": "Jordan-D-W" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The residual stress of a ZrO_2-8%Y_2O_3 thermal barrier coating was determined as a function of thermal cycling. Samples were thermally cycled from 400\u00b0C to 1000\u00b0C in air. After a few cycles the samples exhibited a value of compressive residual stress consistent with that determined by considering the thermal expansion coefficients of the coating and substrate. Stress relief occurs in the ZrO_2-Y_2O_3 coating, increasing in both frequency and magnitude with increasing number of thermal cycles. This behavior is explained in terms of a model of failure of coatings in compression.", "doi": "10.1016/0040-6090(93)90256-O", "issn": "0040-6090", "publisher": "Elsevier", "publication": "Thin Solid Films", "publication_date": "1993-11-25", "series_number": "1-2", "volume": "235", "issue": "1-2", "pages": "137-141" }, { "id": "authors:840d3-hjb35", "collection": "authors", "collection_id": "840d3-hjb35", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328689", "type": "article", "title": "Effective dilatational transformation toughening in brittle materials", "author": [ { "family_name": "Cai", "given_name": "Hongda", "clpid": "Cai-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The toughness of brittle materials can be increased significantly by martensitic phase transformation in which the\ntransformable particles near the crack tip region undergo a stress-indueed transformation with a positive volume change. The mechanics of transformation toughening has been the subject of numerous studies. Earliest models of\ntransformation toughening were based upon energy changes associated with transforation. McMeeking and Evans\npointed out that there were difficulties with these earlier models when compared with experimental results and in some\ncases the models provided conflicting predictions of the role of microstructure, temperature, etc. on the toughness. An\nalternative approach, based upon the reduction in the crack-tip stress intensity factor, was first devised with the objective to\nprovide an unequivocal basis for comparison with experimental results. The steady state dilatational transformation\ntoughening is given in terms of the reduction in the mode I crack tip stress intensity factor:\n\n\u0394 K = - 0.66 \u03a9 V_p \u221ah (E/[2(1-\u03bd^2)] (1)\n\nwhere \u03a9 is the plane strain transformation area dilatation, V_p is the volume fraction of the transformed particles in the\ntransformation zone, h is the transformation zone height, E and \u03bd are the Young's modulus and Poisson's ratio. This result\nwas derived assuming a zone shape of a hydrostatic contour. \n\nThe effective transformation toughening also depends the relative elastic moduli of the transforming particle and nontransforming\nmatrix phases. For a matrix phase of a given elastic modulus, rigid transforming particles are more effective\nin toughening than compliant panicles. The effect of elastic mismatch may not be important in pure zirconia ceramics\ncontaining precipitates of tetragonal ZrO_2 where the mismatch is low. However, the effect can be substantial in\nZrO_2-containing composites. Therefore, the intent of the present work is to extend McMeeking and Evans' model for\ntransformation toughening to include the effect of elastic mismatch between the particle and matrix phases. \n\nElastic mismatch can also affect the stress intensity due to the elastic interaction between near tip stress field and the\nparticles, but this component will not be considered here. Instead, we shall concentrate on the effect which results from the\ndependence of effective transformation strain on elastic mismatch.", "doi": "10.1016/0956-716X(93)90027-P", "issn": "0956-716X", "publisher": "Elsevier", "publication": "Scripta Metallurgica et Materialia", "publication_date": "1993-05-01", "series_number": "9", "volume": "28", "issue": "9", "pages": "1161-1166" }, { "id": "authors:b0p4z-b3w41", "collection": "authors", "collection_id": "b0p4z-b3w41", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328787", "type": "article", "title": "High-Temperature Hardness of Chemically Vapor-Deposited Diamond", "author": [ { "family_name": "Mumm", "given_name": "Daniel R.", "clpid": "Mumm-D-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Drory", "given_name": "Michael D.", "clpid": "Drory-M-D" }, { "family_name": "Gardinier", "given_name": "Clayton F.", "clpid": "Gardinier-C-F" } ], "abstract": "The hardness of chemically vapor-deposited diamond is examined at elevated temperatures. Diamond films of 400-\u03bcm thickness are grown on silicon substrates by plasma-enhanced chemical vapor deposition with subsequent removal of the substrate by chemical etching. Vickers hardness measurements were performed in the temperature range of 500\u00b0\u2013950\u00b0C in an inert gas environment and under 7-N load. A 30% reduction in hardness from the room-temperature value is observed above 800\u00b0C.", "doi": "10.1111/j.1151-2916.1993.tb03716.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1993-01", "series_number": "1", "volume": "76", "issue": "1", "pages": "238-240" }, { "id": "authors:1qjkd-x1b91", "collection": "authors", "collection_id": "1qjkd-x1b91", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140919-144538556", "type": "book_section", "title": "Fracture of Brittle and Quasi-Brittle Engineering Materials", "author": [ { "family_name": "Tandon", "given_name": "S.", "clpid": "Tandon-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The study of fracture of engineering materials involves a number of science and engineering\ndisciplines. Continuum fracture mechanics is deeply rooted in the problem of fracture\nbecause it treats the relationship between a crack or inhomogeneity and the stress\nstate in a material. Physics and chemistry are important because they help to explain the\nreactions between the environment and the crack tip. Finally, materials science is essential\nin understanding the relations among bond rupture, structure, processing and performance\nof a material.\nFracture of materials can be divided into two broad categories - ductile and brittle\nfracture. Ductile fracture is associated with appreciable plastic deformation. \"Cup and\ncone\" fracture demonstrated in metals due to tensile overload is a classic example of ductile\nfracture. The different stages of such fracture are shown in Figure l.l(a). At the maximum\nload, plastic deformation is concentrated in a small gage length of the specimen and\nnecking begins. Once this necked region has formed, fracture begins at the center of the\nspecimen and extends along the dashed lines, finally producing the familiar cup and cone\nfracture. In fcc metals, plastic deformation continues on the conjugate slip planes until the\nspecimen has necked down to a sharp point. Polycrystalline metals with second phase particles\nfail due to initiation, growth and coalescence of micro-voids formed in the necked region. Similarly, semicrystalline polymers exhibit necking which leads to localized\nstrengthening of the specimen. Then the specimen elongates due to the propagation of this\nneck along the gage length. This ductile fracture in polymers is different from that in metals,\nin which all subsequent deformation is confined to the neck region.\nAlternatively, brittle fracture is associated with little or no deformation. A brittle material\nbehaves elastically up to the maximum load at which catastrophic failure occurs (Fig.\n1.1(b )). Silicate glasses are the most common example of such fracture. Brittle fracture\nis controlled by microscopic inclusions, surface and interior flaws and defects and pores\npresent in the material. An intermediate category of fracture, known as quasi-brittle\nfracture, has recently been defined. A quasi-brittle material, a title which encompasses\nmany polycrystalline ceramics and cementitious materials, shows measurable deformation\nprior to failure. The deformation, however, is not associated with dislocation motion. At\nthe onset of nonlinearity in the load-displacement relationship existing flaws in the material\nstart growing and new flaws form (Fig. 1.1(c)). Such materials are characterized by a\nsoftening curve after the peak load. This softening branch of the load-displacement relationship\nis associated with stable crack growth in the material before the final fracture. The\nfailed specimen, however, need not look any different from a classically-brittle failed specimen. \n\nIn a review article such as this, it is useful to first build the necessary background, and\nvarious aspects of fracture mechanics are reviewed in the next section. This review is followed\nby discussions of the microstructural aspects of toughening mechanisms, short crack\nfracture in comparison to long crack fracture, the statistical nature of fracture and its implications\nfor quasi-brittle materials, and slow crack growth and other environmental effects\non various fracture processes are presented. The implications to cementitious materials\nare discussed throughout.", "publisher": "American Ceramic Society", "publication_date": "1993" }, { "id": "authors:an0g1-nj648", "collection": "authors", "collection_id": "an0g1-nj648", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140915-112949042", "type": "book_section", "title": "Multiple Cracking and Interface Debonding in a Brittle Film on a Ductile Rod", "book_title": "Advances in Ceramic-Matrix Composites", "author": [ { "family_name": "Cazzato", "given_name": "A.", "clpid": "Cazzato-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Bansal", "given_name": "N. P." } ], "abstract": "A test technique was developed to measure interfacial shear strength through\nobservation of crack densities in bimaterial concentric cylinders. Multiple cracking\nand debonding were observed in a model ductile-brittle pair of aluminum rods\nwith soda-silicate cement coatings and the results compared to a system where the\ninterface was modified by a polymeric interphase layer. A shear lag analysis was\nused to relate the observed crack densities to the interfacial shear strength. Four\npoint bend tests were performed on monolithic soda-silicate cement specimens to\ndetermine the statistical variation in strength of the coating material. A multiple\ncracking computer simulation was developed to include the statistical nature of the\ncoating strength. The crack density, bend testing and simulation results were integrated\nto calculate interfacial shear strength in the Al-cement system.", "isbn": "0944904696", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1993", "pages": "329-338" }, { "id": "authors:jtfxv-g4v64", "collection": "authors", "collection_id": "jtfxv-g4v64", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140915-113613432", "type": "book_section", "title": "DCB Methods for Examining Toughening in Alumina Reinforced with Carbon Coated SiC Whiskers", "book_title": "Advances in Ceramic-Matrix Composites", "author": [ { "family_name": "Steyer", "given_name": "T. E.", "clpid": "Steyer-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Bansal", "given_name": "N. P." } ], "abstract": "The mechanical properties of Al_2O_3 have been substantially improved by the addition\nof SiC whiskers. Room temperature strength and fracture toughness have\nbeen reported for a variety of whisker sources and whisker fractions. The composite\nmicrostructure and the properties of the whisker/matrix interface allow various\ntoughening mechanisms to be active in the SiC/Al_2O_3 system including crack\nbranching and deflection, whisker and grain bridging, and whisker debonding and\npullout.\n\nModifications of the whisker/matrix interface are one way of tailoring the composite\nmicrostructure. Tiegs et al. have made composites from heat-treated and acid-leached\nwhiskers to modify the whisker surface chemistry and the whisker/matrix\ninterfacial chemistry. \n\nA second means of modifying the whisker/matrix interface has been suggested by\nHsueh et al. in which a low modulus film is used to modify the residual stress.\nUsing this theory, a 50 \u00c5 carbon film on a 0.7 \u03bcm diameter whisker would result in\na nearly ten percent reduction of residual stress at the whisker/matrix interface in\nSiC whisker-reinforced alumina. \n\nSiC whiskers coated with carbon are used in this study as a way of modifying the\nchemical and mechanical bonding at the whisker/matrix interface by directly\nchanging the interfacial chemistry and by modifying the residual thermal stresses found in these materials due to the thermal expansion mismatch of the composite\nconstituents. In this study, two DCB methods of analysis are used to examine the\neffects of modified interfaces on fracture toughness in these materials.", "isbn": "0944904696", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1993", "pages": "617-630" }, { "id": "authors:5gpmg-q8r84", "collection": "authors", "collection_id": "5gpmg-q8r84", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140915-111614317", "type": "book_section", "title": "Micro-Mechanical Aspects of Fiber Debonding and Frictional Sliding in Brittle Matrix Composites", "book_title": "Advances in Ceramic-Matrix Composites", "author": [ { "family_name": "Mumm", "given_name": "Daniel R.", "clpid": "Mumm-D-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Bansal", "given_name": "N. P.", "clpid": "Bansal-N-P" } ], "abstract": "It is now well established that the mechanical behavior of a fiber-reinforced brittle-matrix material largely depends on the properties of the fiber-matrix interface. In\nparticular, to obtain enhanced toughness through fiber reinforcement, the interface\nmust exhibit a relatively low fracture energy such that fiber debonding and crack\nbridging occur during matrix crack propagation. With further matrix crack extension,\ndebond propagation and frictional fiber sliding occur, providing energy dissipation\nfor enhanced toughness. Interfacial properties of importance include the\nfracture energy, frictional sliding characteristics and residual stress state. In addition,\nthe morphology of the sliding interface has recently emerged as an important\ninterfacial parameter which can greatly influence fiber debonding and sliding\nbehavior. Experimental evidence of the role of fiber surface morphology during\nfiber sliding was first reported by Jero and Kerans. \n\nRecognition of the importance of the interfacial properties has prompted the development\nof a number of techniques to evaluate these parameters, including the single-fiber pull-out and push-down tests. These techniques are designed to directly\ndetermine composite interfacial properties, and therefore, assess the mechanical\nperformance of fiber-reinforced brittle-matrix materials. Numerous fiber debonding\nand sliding experiments have been done using these two techniques. However,\na number of factors make it difficult to determine fundamental interfacial\nproperties from such tests. For instance, with the push-down technique, the sample\ngeometry results in prominent end effects. In addition, the preparation of pushdown\nspecimens may allow relief of residual stresses which are now known to play an important role in determining fiber debonding and sliding behavior. Furthermore,\nsince the applied loads are compressive, the push-down technique does\nnot properly evaluate the effects of locally sliding fiber strength, i.e. fiber fracture\naway from the matrix crack plane and the frictional pull-out of the fractured fibers. \n\nThere are equivalent concerns with the standard single-fiber pull-out technique.\nThe free length of fiber protruding from the edge of the specimen leads to low system\nstiffness, and accurate fiber displacement measurements are difficult to obtain.\nIn this work, an improved single-fiber pull-out technique .has been developed and\nused to observe stable, progressive fiber debonding and sliding in two model composite\nsystems. Fiber surface roughness is shown. to have a pronounced effect on\nthe interfacial frictional sliding in these composite systems. Roughness-induced\nload fluctuations are observer during progressive debonding, with the fluctuation\namplitude increasing with frictional sliding zone length.", "isbn": "0944904696", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1993", "pages": "163-172" }, { "id": "authors:8pq0z-rw598", "collection": "authors", "collection_id": "8pq0z-rw598", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329039", "type": "article", "title": "Crack Bridging by Inclined Fibers/Whiskers in Ceramic Composites", "author": [ { "family_name": "Cai", "given_name": "Hongda", "clpid": "Cai-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Fuller", "given_name": "Edwin R., Jr.", "clpid": "Fuller-E-R-Jr" } ], "abstract": "Crack bridging by inclined fibers has been studied in a brittle fiber-brittle matrix model ceramic composite. Results of the fiber bridging force vs the crack opening displacement have been obtained for different fiber inclination angles using a fracture mechanics approach. Localized matrix cracking has been observed for inclined fibers and related to fiber inclination angle. The experimental results showing the influence of fiber inclination angle are discussed and compared with theoretical analyses to provide insight into crack bridging by inclined fibers/whiskers. Implications for toughening by whisker bridging are also discussed.", "doi": "10.1111/j.1151-2916.1992.tb04395.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1992-11", "series_number": "11", "volume": "75", "issue": "11", "pages": "3111-3117" }, { "id": "authors:5tmay-p8446", "collection": "authors", "collection_id": "5tmay-p8446", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181328925", "type": "article", "title": "Microcracking and R-curve behavior in SiC-TiB_2 composites", "author": [ { "family_name": "Gu", "given_name": "W.-H.", "clpid": "Gu-W-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Steinbrech", "given_name": "R. W.", "clpid": "Steinbrech-R-W" } ], "abstract": "The fracture toughness of SiC-TiB_2 composites is studied as a function of TiB_2 size and fraction with emphasis on the effect of stress-induced microcracking. R-curve behavior in these materials is observed from double cantilever beam tests and is found to be a major strength-controlling factor. The microcrack process zones are confirmed by both small angle X-ray scattering and transmission electron microscopy. The process zone size scales with the fraction of TiB_2 present. For composites containing fine TiB_2 particles, quasi-catastrophic crack growth and arrest are observed during R-curve measurements. The various contributions to the R-curve are discussed.", "doi": "10.1016/0956-7151(92)90475-T", "issn": "0956-7151", "publisher": "Elsevier", "publication": "Acta Metallurgica et Materialia", "publication_date": "1992-11", "series_number": "11", "volume": "40", "issue": "11", "pages": "3121-3128" }, { "id": "authors:tw07n-xwj94", "collection": "authors", "collection_id": "tw07n-xwj94", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329276", "type": "article", "title": "Process zone formation in cement-aggregate composites", "author": [ { "family_name": "Kilius", "given_name": "D. E.", "clpid": "Kilius-D-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Many non-metallic structural materials, such as\nPortland cement concrete, are limited in their utility\nb} their low tensile strength and fracture toughness.\nToughening agents lend these materials greater flaw\ntolerance and the ability to sustain greater loads.\nThe operative toughening mechanisms are not\nunderstood well in cement-based composites, but\nare believed to arise from fracture process zones\nahead of the crack tip and in the wake of the crack,\nand act to reduce the stress intensity or shield the\ncrack from the applied loading.", "doi": "10.1007/BF00730273", "issn": "0261-8028", "publisher": "Springer", "publication": "Journal of Materials Science Letters", "publication_date": "1992-09-01", "series_number": "17", "volume": "11", "issue": "17", "pages": "1167-1169" }, { "id": "authors:rfmwm-5eb48", "collection": "authors", "collection_id": "rfmwm-5eb48", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329163", "type": "article", "title": "On the Use of Approximation Methods for Microcrack Shielding Problems", "author": [ { "family_name": "Cai", "given_name": "H.", "clpid": "Cai-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "There is experimental evidence that stress-induced microcracking near a macrocrack tip enhances the fracture toughness of brittle materials. In considering the interaction of the macrocrack with multiple microcracks using a discrete model, it is essential to use approximation methods in order to keep the amount of the computation to a tractable level. However, when crack distances are small, the results of the approximation methods can be significantly different from the numerical solution based upon the exact formulation. The results obtained by these approximation methods will be compared with the numerical solution to show the applicability ranges in which the errors are acceptably small. The use of results obtained by the approximation methods outside applicability ranges in literature is shown to lead to incorrect conclusions concerning microcrack shielding.", "doi": "10.1115/1.2893751", "issn": "0021-8936", "publisher": "American Society Mechanical Engineers", "publication": "Journal of Applied Mechanics", "publication_date": "1992-09", "series_number": "3", "volume": "59", "issue": "3", "pages": "497-501" }, { "id": "authors:rf8j9-0bv30", "collection": "authors", "collection_id": "rf8j9-0bv30", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-205922710", "type": "book_section", "title": "Fiber Debonding and Pullout Processes in Ceramic Composites", "book_title": "Proceedings of the 16th Annual Conference on Composites and Advanced Ceramic Materials", "author": [ { "family_name": "Mumm", "given_name": "D. R.", "clpid": "Mumm-D-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Wachtman", "given_name": "John B., Jr.", "clpid": "Wachtman-J-B-Jr" } ], "abstract": "The fiber debonding and pullout behavior in a model ceramic composite system has been investigated using a novel single-fiber pullout technique. Stable, progressive debonding was observed prior to fiber fracture and frictional fiber pullout. Interfacial parameters were calculated from single load-displacement curves using a recent analysis of the fiber debonding and pullout process. The interfacial parameters extracted from these experiments are consistent with independent measurements reported in the literature. The morphology of the fiber surface appears to play a significant role in determining the fiber debonding and sliding behavior.", "doi": "10.1002/9780470313954.ch8", "isbn": "9780470375174", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1992", "pages": "70-77" }, { "id": "authors:3v5nb-avf12", "collection": "authors", "collection_id": "3v5nb-avf12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210114-140129140", "type": "book_section", "title": "Preface", "book_title": "Semiconductors and Semimetals", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Malloy", "given_name": "Kevin J.", "clpid": "Malloy-Kevin-J" } ], "contributor": [ { "family_name": "Faber", "given_name": "Katherine T.", "clpid": "Faber-K-T" }, { "family_name": "Malloy", "given_name": "Kevin J.", "clpid": "Malloy-Kevin-J" } ], "abstract": "[no abstract]", "doi": "10.1016/s0080-8784(08)62511-9", "isbn": "9780127521374", "publisher": "Academic Press", "place_of_publication": "San Diego, CA", "publication_date": "1992", "pages": "ix-x" }, { "id": "authors:bj5te-2ff98", "collection": "authors", "collection_id": "bj5te-2ff98", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329407", "type": "book_section", "title": "Mechanical Behavior of Compound Semiconductors", "book_title": "Mechanical Properties of Semiconductors", "author": [ { "family_name": "Guruswamy", "given_name": "Sivaraman", "clpid": "Guruswamy-S" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hirth", "given_name": "John P.", "clpid": "Hirth-J-P" } ], "contributor": [ { "family_name": "Faber", "given_name": "Katherine T.", "clpid": "Faber-K-T" }, { "family_name": "Malloy", "given_name": "Kevin J.", "clpid": "Malloy-K-J" } ], "abstract": "The semiconductor industry has long been aware of the need to avoid\ndeformation during bulk single-crystal semiconductor growth or during\nsubsequent device processing. The generation of dislocations during liquid-encapsulated\nCzochralski (LEC) growth of Si, Ge, GaAs, and other III-V\ncompounds is believed to occur when the thermal stress imposed on the\ncrystal during growth exceeds the critical resolved shear stress (CRSS) and\nthe crystal is deformed (Mil'vidskii and Bochkavev, 1978; Jordan et al., 1980,\n1984, and 1986). The dislocation density increase that results from deformation\nhas a deleterious effect on the device yield, performance and reliability\n(Nanishi et al., 1982; Petroff and Hartman, 1973; Miyazawa and Hyuga,\n1986). The reduction of thermal stresses during crystal growth and enhancement\nof crystal strength by doping, such as with In and Si in GaAs (Jordan\nand Parsey, 1986, 1988; McGuigan et al., 1986) makes possible growth of\nlarge single crystals with reduced defects. The deformation behavior of Si and\nGe has been a subject of much research for the past three decades while\nlimited studies have been performed on III-V and II-VI compound semiconductors\nsuch as GaAs, InP, and CdTe. The mechanical response of these\ncrystals depends on the crystal structure, nature of atomic bonding, concentration\nof dopants, temperature, and strain or loading rate. In this paper we\nreview the current understanding of the deformation behavior in these\nmaterials. Their expected behavior at low, intermediate, and high temperatures,\npredicted from the current understanding of dislocation motion in\nsolids, is presented along with compressive, tensile, and hardness data on\nGaAs, InP, CdTe, and Si. The effects of ternary dopants on the mechanical\nbehavior of these materials are analyzed using ideas of solid solution\nstrengthening and defect chemistry. Finally, implications for defect-free\ncrystal growth and device fabrication are examined.", "doi": "10.1016/S0080-8784(08)62516-8", "isbn": "0-12-752137-2", "publisher": "Academic Press", "place_of_publication": "Boston, MA", "publication_date": "1992", "pages": "189-230" }, { "id": "authors:4c78e-xx556", "collection": "authors", "collection_id": "4c78e-xx556", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-204747280", "type": "book_section", "title": "Fracture Behavior of SiC Whisker-Reinforced Al_2O_3 with Modified Interfaces", "book_title": "Proceedings of the 16th Annual Conference on Composites and Advanced Ceramic Materials", "author": [ { "family_name": "Steyer", "given_name": "T. E.", "clpid": "Steyer-T-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Wachtman", "given_name": "John B., Jr.", "clpid": "Wachtman-J-B-Jr" } ], "abstract": "Carbon-coated SiC whiskers have been examined as a function of coating thickness for reinforcement in Al_2O_3. A compliant carbon layer at the whisker/ matrix interface modifies the residual stress due to thermal expansion mismatch and changes the interfacial chemistry. The fracture behavior of this material has been observed using 4-point bending for strength and the double cantilever beam technique for fracture toughness and R-curve behavior. The strength and R-curve behavior of composites with and without whisker coatings of carbon are presented to evaluate the effect of modified interfaces on the mechanical performance of whisker composites.", "doi": "10.1002/9780470313978.ch11", "isbn": "9780470375198", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1992", "pages": "669-677" }, { "id": "authors:88gv1-net36", "collection": "authors", "collection_id": "88gv1-net36", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329539", "type": "article", "title": "Ferroelastic Toughening in Bismuth Vanadate", "author": [ { "family_name": "Baker", "given_name": "Theresa L.", "clpid": "Baker-T-L" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Readey", "given_name": "D. W.", "clpid": "Readey-D-W" } ], "abstract": "Bismuth vanadate has been used as a model system to examine toughening by stress-induced domain motion in a ferroelastic material. Fracture toughnesses in the ferroelastic and paraelastic states have been compared. Toughening and R-curve behavior have been observed in the ferroelastic state. Single crystals of BiVO_4 show domain nucleation and propagation under compressive loading and domain generation during fracture. The increase in toughening in the ferroelastic state can be explained by a combination of crack deflection and domain wall motion, the latter contributing to R-curve behavior.", "doi": "10.1111/j.1151-2916.1991.tb07148.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1991-07", "series_number": "7", "volume": "74", "issue": "7", "pages": "1619-1623" }, { "id": "authors:cm4ex-4af42", "collection": "authors", "collection_id": "cm4ex-4af42", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329661", "type": "article", "title": "Analysis of a Microcrack Prototype and Its Implications for Microcrack Toughening", "author": [ { "family_name": "Cai", "given_name": "Hongda", "clpid": "Cai-H" }, { "family_name": "Moran", "given_name": "B.", "clpid": "Moran-B" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The stress intensity factor, the volume, and the macroscopic dilatational strain associated with microcracking for various crack lengths and elastic mismatches are examined for a microcrack prototype, which consists of a penny-shaped crack in the center of spherical particle under residual hydrostatic tension. The results of these quantities and the implications for microcrack toughening are presented. The effects of elastic mismatch between the particle and matrix phases are emphasized.", "doi": "10.1111/j.1151-2916.1991.tb07164.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1991-07", "series_number": "7", "volume": "74", "issue": "7", "pages": "1695-1698" }, { "id": "authors:z3wxb-jcy10", "collection": "authors", "collection_id": "z3wxb-jcy10", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329775", "type": "book_section", "title": "Fracture Properties on SiC Based Particulate Composites", "book_title": "Toughening Mechanisms in Quasi-Brittle Materials", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Gu", "given_name": "W.-H.", "clpid": "Gu-W-H" }, { "family_name": "Cai", "given_name": "H.", "clpid": "Cai-H" }, { "family_name": "Winholtz", "given_name": "R. A.", "clpid": "Winholtz-R-A" }, { "family_name": "Magley", "given_name": "D. J.", "clpid": "Magley-D-J" } ], "contributor": [ { "family_name": "Shah", "given_name": "S. P.", "clpid": "Shah-S-P" } ], "abstract": "In order to evaluate the role of residual stresses in\nfracture toughening, a SiC-based particulate composite has been studied\nunder uniform stressing conditions and in the near tip stress field of a\npre-cracked specimen. First, residual stresses in a SiC-TiB_2 composite\nbefore and after stressing have been measured using x-ray diffraction.\nTensile residual stresses in the TiB_2 drop by 50% after bending stresses\nof 250 MPa were applied. Likewise, the compressive residual stresses in\nthe SiC phase decrease accordingly. Second, in the near tip stress\nfield, a process zone of microcracks has been measured using\ntransmission electron microscopy of thin foils taken from various\nlocations from a fracture surface of a fracture mechanics specimen.\nMicrocrack zones greater than 150 \u03bcm in height have been measured.\nCrack bridging sites of TiB_2 particles operate more than a few\nmillimeters behind a propagating crack. Hence, the toughening in this\nsystem is comprised of both stress-induced microcracking and crack\nbridging. The various contributions to the toughening are discussed.", "doi": "10.1007/978-94-011-3388-3_1", "isbn": "0792311981", "publisher": "Kluwer Academic Publishers", "place_of_publication": "Boston, MA", "publication_date": "1991", "pages": "3-17" }, { "id": "authors:4q3w1-axd62", "collection": "authors", "collection_id": "4q3w1-axd62", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329983", "type": "article", "title": "Residual Stresses in a Two-Phase Microcracking Ceramic", "author": [ { "family_name": "Magley", "given_name": "David J.", "clpid": "Magley-D-J" }, { "family_name": "Winholtz", "given_name": "R. A.", "clpid": "Winholtz-R-A" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Residual stresses in a SiC-TiB_2 particulate composite before and after stressing have been measured using X-ray diffraction. Tensile residual stresses in the TiB_2 drop by 60% after bending stresses of 250 MPa are applied. Likewise, the compressive residual stresses in the SiC phase decrease accordingly. Such behavior is consistent with stress-induced microcracking.", "doi": "10.1111/j.1151-2916.1990.tb09808.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1990-06", "series_number": "6", "volume": "73", "issue": "6", "pages": "1641-1644" }, { "id": "authors:ehh2p-16072", "collection": "authors", "collection_id": "ehh2p-16072", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181329879", "type": "article", "title": "Segregant-enhanced fracture in magnesium oxide", "author": [ { "family_name": "Conner", "given_name": "C. L.", "clpid": "Conner-C-L" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The fracture toughness of MgO has been studied as a function of the concentration of an intergranular LiF phase, added to enhance densification. The fracture toughness increases as lithium and fluorine are volatilized from the MgO while the fracture morphology changes from intergranular to transgranular. The data are interpreted with respect to competing embrittlement and crack-deflection toughening mechanisms, and a scheme is proposed for determining conditions for embrittlement and toughening.", "doi": "10.1007/BF00584873", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "1990-06", "series_number": "6", "volume": "25", "issue": "6", "pages": "2737-2742" }, { "id": "authors:01499-ndc26", "collection": "authors", "collection_id": "01499-ndc26", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330094", "type": "article", "title": "Interfacial shear stresses in fiber-reinforced glasses", "author": [ { "family_name": "Goettler", "given_name": "R. W.", "clpid": "Goettler-R-W" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The single fiber pull-out test has been used to measure interfacial properties of SiC fibers in soda-borosilicate glass matrices. Two parameters are examined: the SiC to free carbon ratio at the surface of the SiC fiber is varied to test the effect of interfacial chemistry and the glass expansion is varied to investigate the effect of residual stresses. A carbon coating is shown to be effective in preventing strong fiber-matrix bonding and oxidation of the SiC fibers by the glass. However, coatings with higher carbon content result in stronger bonding to the soda-borosilicate glass. Both the interfacial shear strength and the frictional shear stress increase linearly with residual stress and reach a maximum of nearly double the strain-free value above which the interfacial strength decreases as a result of radial crack formation in the glass matrix. The measured interfacial shear properties are also found to be stress rate dependent.", "doi": "10.1016/0266-3538(90)90096-N", "issn": "0266-3538", "publisher": "Elsevier", "publication": "Composites Science and Technology", "publication_date": "1990-01", "series_number": "1-3", "volume": "37", "issue": "1-3", "pages": "129-147" }, { "id": "authors:67wa6-5rz06", "collection": "authors", "collection_id": "67wa6-5rz06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140917-175220552", "type": "book_section", "title": "Microcrack Toughening in a SiC-TiB_2 Composite", "book_title": "Proceedings of the American Society for Composites Fifth Technical Conference : composite materials in transition", "author": [ { "family_name": "Cai", "given_name": "H.", "clpid": "Cai-H" }, { "family_name": "Gu", "given_name": "W.-H.", "clpid": "Gu-W-H" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Transmission electron microscopy observations of a fractured SiC-TiB_2\ncomposite have provided conclusive evidence of stress-induced microcracking\nin this system. The microcrack density parameter around a steadily growing\ncrack has been measured as a function of the distance from the crack plane.\nMicrocrack toughening in this system has been assessed using a discrete\nmodel based on the measured microcrack density parameter. The\ncomputation results indicate that nearly half of the toughening arises from\nstress-induced microcracking. Other possible toughening mechanisms are\nalso discussed.", "isbn": "0877627673", "publisher": "Technomic Publishing", "place_of_publication": "Lancaster, PA", "publication_date": "1990", "pages": "892-901" }, { "id": "authors:9j2cb-wey17", "collection": "authors", "collection_id": "9j2cb-wey17", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330183", "type": "article", "title": "Dislocation structures in In-doped and undoped GaAs deformed at 700-1100\u00b0C", "author": [ { "family_name": "Rai", "given_name": "R. S.", "clpid": "Rai-R-S" }, { "family_name": "Guruswamy", "given_name": "S.", "clpid": "Guruswamy-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hirth", "given_name": "J. P.", "clpid": "Hirth-J-P" } ], "abstract": "Dislocation structures in In-doped and undoped GaAs single crystals deformed at 700-1100\u00b0C have been studied by transmission electron microscopy. The results for (Ga, In)As, similar to earlier findings for Si and Ge, provide the basis for a proposed model for recovery processes. The observed structures together with their mechanical properties indicate that the role of In is consistent with an athermal contribution to the frictional stress arising from a solid-solution-hardening effect.", "doi": "10.1080/01418618908213866", "publisher": "Taylor & Francis", "publication": "Philosophical Magazine A", "publication_date": "1989-09", "series_number": "3", "volume": "60", "issue": "3", "pages": "339-353" }, { "id": "authors:6s4t2-qdr05", "collection": "authors", "collection_id": "6s4t2-qdr05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330279", "type": "article", "title": "Influence of solute doping on the high-temperature deformation behavior of GaAs", "author": [ { "family_name": "Guruswamy", "given_name": "S.", "clpid": "Guruswamy-S" }, { "family_name": "Rai", "given_name": "R. S.", "clpid": "Rai-R-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hirth", "given_name": "J. P.", "clpid": "Hirth-J-P" }, { "family_name": "Clemans", "given_name": "J. E.", "clpid": "Clemans-J-E" }, { "family_name": "McGuigan", "given_name": "S.", "clpid": "McGuigan-S" }, { "family_name": "Thomas", "given_name": "R. N.", "clpid": "Thomas-R-N" }, { "family_name": "Mitchel", "given_name": "W.", "clpid": "Mitchel-W" } ], "abstract": "The role of isovalent dopants in the high\u2010temperature deformation of GaAs has been studied in the temperature range 500\u20131150\u2009\u00b0C. Additions of In, Sb, and B increase the critical resolved shear stress for deformation at a given strain rate and result in lowering the dislocation density of as\u2010grown liquid\u2010encapsulated Czochralski GaAs crystals. Phosphorus, because of its minor influence on the lattice strain, shows little enhancement of the yield stress. These results are consistent with a solute hardening model, in which the solute atom surrounded tetrahedrally by four Ga or As atoms comprise the hardening cluster. Codoping with In and Si hardens GaAs, but codoping with Si is less effective than the isovalent solutes In, Sb, and B, and produces softening at high temperatures. The effect of solutes on both dislocation nucleation and multiplication are reviewed here.", "doi": "10.1063/1.342797", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1989-03-15", "series_number": "6", "volume": "65", "issue": "6", "pages": "2508-2512" }, { "id": "authors:smahz-q0137", "collection": "authors", "collection_id": "smahz-q0137", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330391", "type": "article", "title": "Toughening by Stress-Induced Microcracking in Two-Phase Ceramics", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Iwagoshi", "given_name": "Thawi", "clpid": "Iwagoshi-T" }, { "family_name": "Ghosh", "given_name": "Asish", "clpid": "Ghosh-A" } ], "abstract": "Two glass/alumina composites were examined as potential systems for srress-induced\nmicrocrack roughening. A borosilicate glass/alumina material having a\nthermal mismatch strain of approximately 0.8% demonstrated toughness up to twice that of an aluminosilicate glass/alumina composite and other reported\nglass/alumina composites. High-sensitvity density measurements confirmed a\ndensity reduction on application of a stress in the borosilicate glass/alumina system, providing indirect evidence for stress-induced microcracking.", "doi": "10.1111/j.1151-2916.1988.tb06419.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1988-09", "series_number": "9", "volume": "71", "issue": "9", "pages": "C399-C401" }, { "id": "authors:fm918-yxs92", "collection": "authors", "collection_id": "fm918-yxs92", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-142040172", "type": "book_section", "title": "Toughening in ZrO_2-Based Materials", "book_title": "Advanced Ceramics", "author": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Saito", "given_name": "Shinroku", "clpid": "Saito-S" } ], "abstract": "Fracture toughening processes in transformation toughened zirconia and related\nsystems are reviewed. The main toughening derives from the martensitic transformation of\ntetragonal ZrO_2 particles to their monoclinic form ahead of a crack as analyzed by\nthermodynamic and continuum approaches. The implications for crack-length dependent\nfracture resistance based upon the toughening models are included. Additional toughening\ncontributions are evaluated for microcracking and crack deflection processes using recent\nmodels. Systems where transformation toughening occurs are summerized, including\nmaterials which are surface-strengthened through the tetragonal-monoclinic transformation.\nThe effects of temperature and environment on mechanical behavior are also\nconsidered.", "isbn": "0198563353", "publisher": "Oxford University Press", "place_of_publication": "New York, NY", "publication_date": "1988", "pages": "76-94" }, { "id": "authors:6efb9-vhv88", "collection": "authors", "collection_id": "6efb9-vhv88", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-201611322", "type": "book_section", "title": "Interfacial Shear Stresses in SiC and Al_2O_3 Fiber-Reinforced Glasses", "book_title": "Proceedings of the 12th Annual Conference on Composites and Advanced Ceramic Materials", "author": [ { "family_name": "Goettler", "given_name": "R. W.", "clpid": "Goettler-R-W" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Wachtman", "given_name": "John B., Jr.", "clpid": "Wachtman-J-B-Jr" } ], "abstract": "Single fiber pullout tests were performed on silicon carbide and sapphire filaments embedded in glass matrices to determine the interfacial shear strengths both as a function of residual stress and as a function of fiber coating. The effect of residual stress on the interfacial shear stress was studied by altering the glass matrix composition, and hence, the thermal mismatch between fiber and matrix. The interfacial shear strength exhibits a maximum with increasing thermal mismatch after which it drops precipitously and levels off. The presence of a carbon coating on sapphire is sufficient to reduce the interfacial shear stress to measurable levels, while excess carbon at the SiC/glass interface increases the interfacial shear stress. In the silicon carbide-reinforced systems, the interfacial shear strengths are also shown to be stressing-rate dependent.", "doi": "10.1002/9780470310496.ch37", "isbn": "9780470374801", "publisher": "American Ceramic Society", "place_of_publication": "Westerville, OH", "publication_date": "1988", "pages": "861-870" }, { "id": "authors:k2nez-9d339", "collection": "authors", "collection_id": "k2nez-9d339", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-121838056", "type": "book_section", "title": "Segregant enhanced fracture of mechanics", "book_title": "Interfacial structure, properties, and design : symposium held April 5-8, 1988, Reno, Nevada, U.S.A.", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hickenbottom", "given_name": "Cynthia C.", "clpid": "Hickenbottom-C-C" } ], "contributor": [ { "family_name": "Yoo", "given_name": "M. H.", "clpid": "Yoo-M-H" }, { "family_name": "Clark", "given_name": "W. A. T.", "clpid": "Clark-W-A-T" }, { "family_name": "Briant", "given_name": "C. L.", "clpid": "Briant-C-L" } ], "abstract": "The fracture toughness and failure mode of ceramic materials are highly\nsensitive to the presence of impurities at grain boundaries. Magnesium\noxide serves as a model material to investigate fracture with respect to\nimpurity levels at grain boundaries. Lithium fluoride, added to MgO as a\nsintering aid, is retained as an intergranular phase. By post-fabrication\nheat treatment, the LiF is removed and a change in fracture mode follows.\nTransmission and scanning electron microscopy, along with analytical (atomic\nabsorption spectroscopy and selective electrode analysis) and microanalytical\n(scanning Auger microprobe) techniques are used to follow the progression of LiF with heat treatment. The results of this study are compared\nto other oxides and carbide systems in which the fracture toughness has also\nbeen found to be sensitive to the amount and location of segregants.", "isbn": "0931837928", "publisher": "Materials Research Society", "publication_date": "1988", "pages": "475-483" }, { "id": "authors:dsknz-6av68", "collection": "authors", "collection_id": "dsknz-6av68", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330496", "type": "article", "title": "Deformation behavior of undoped and In-doped GaAs in the temperature range 700\u20131100\u2009\u00b0C", "author": [ { "family_name": "Guruswamy", "given_name": "S.", "clpid": "Guruswamy-S" }, { "family_name": "Rai", "given_name": "R. S.", "clpid": "Rai-R-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hirth", "given_name": "J. P.", "clpid": "Hirth-J-P" } ], "abstract": "Compressive deformation of undoped and In\u2010doped GaAs single crystals has been carried out in [001] and [123] orientations in the temperature range 700\u20131100\u2009\u00b0C. Indium additions, at levels of 1\u20132\u00d710^(20) atoms cm^(\u22123), result in critical resolved shear stress (CRSS) values that are about twice as large as the undoped crystals in the temperature range of 700\u20131100\u2009\u00b0C. The CRSS was weakly dependent on temperature in the temperature range investigated as expected for a model of athermal solid solution hardening. The CRSS value of 3.3 MPa for the In\u2010doped crystal is sufficient to eliminate profuse dislocation formation in a 75\u2010mm\u2010diam crystal on the basis of current theories for the magnitude of the thermal stress experienced during growth. The results also suggest that the process of dislocation climb is slowed appreciably by In doping.", "doi": "10.1063/1.339129", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1987-11-15", "series_number": "10", "volume": "62", "issue": "10", "pages": "4130-4134" }, { "id": "authors:mta4k-j3f23", "collection": "authors", "collection_id": "mta4k-j3f23", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330605", "type": "article", "title": "Computer Simulations of R-Curve Behavior in Microcracking Materials", "author": [ { "family_name": "Bowling", "given_name": "Gregory D.", "clpid": "Bowling-G-D" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hoagland", "given_name": "R. G.", "clpid": "Hoagland-R-G" } ], "abstract": "A computer program has been developed which simulates the process of microcracking in two-phase ceramic materials. This simulation provides a method of examining the complex interactions which occur between a propagating crack and the residually stressed particles around it. As the residual stresses near second-phase inclusions are relieved by microcrack formation, a process zone forms around the main crack, partially shielding it. The resulting crack resistance curves, or R curves, associated with crack shielding mechanisms are generated by the program. Three variables\u2014 the microcrack density (f_s), the dilatant strain associated with each microcracked particle (\u03b8), and the orientation of the microcracks (\u03a8)\u2014 were used to determine their influence on fracture toughness. The steady-state toughness was found to increase with second-phase particle additions, increased dilatant strain, and the formation of microcracks parallel to the direction of applied stress. However, the magnitude of toughening increase attained in these-simulations was generally lower than that predicted by continuum models. This discrepancy is attributed to the fact that interactions between microcracks produce frontal zones which result in a positive \u0394k, and hence, a lower steady-state toughness. This behavior is enhanced when microcracks link with the main crack to promote further extension.", "doi": "10.1111/j.1151-2916.1987.tb05639.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1987-11", "series_number": "11", "volume": "70", "issue": "11", "pages": "849-854" }, { "id": "authors:gq04z-j8e08", "collection": "authors", "collection_id": "gq04z-j8e08", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330707", "type": "article", "title": "Fracture of ceramics and glasses", "author": [ { "family_name": "Clarke", "given_name": "D. R.", "clpid": "Clarke-D-R" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "The rich variety of fracture behavior exhibited by glasses and ceramic materials is reviewed with particular emphasis on the understanding gained through the use of deliberately introduced, controlled cracks. After a brief summary of the mechanics of indentation cracks four major topics are discussed, the structure of crack tips, environment assisted crack growth, high temperature fracture and the toughening of ceramics. Resolution of the sharp vs blunt crack dilemma is presented together with recent microscopy observations of crack tips in brittle solids. In describing fracture in polycrystalline ceramics we explore some of the complexities beyond the simple Griffith behavior relating strength to flaw size, and show how the scale of the microstructure with respect to the crack length affects the observed toughness. It is shown that the interaction of a crack with the microstructure provides a unifying theme for interpreting much of the current work in the literature and leads to important concepts discussed here, such as the discrete-continuum transition, R-curve behavior, toughening due to crack deflection and crack bridging, transformation toughening and stress-induced microcrack toughening.", "doi": "10.1016/0022-3697(87)90121-1", "issn": "0022-3697", "publisher": "Elsevier", "publication": "Journal of Physics and Chemistry of Solids", "publication_date": "1987", "series_number": "11", "volume": "48", "issue": "11", "pages": "1115-1157" }, { "id": "authors:3hevj-1p593", "collection": "authors", "collection_id": "3hevj-1p593", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-125902002", "type": "book_section", "title": "Temperature-Dependent Toughening in Whisker-Reinforced Ceramics", "book_title": "Ceramic Microstructures '86: Role of Interfaces", "author": [ { "family_name": "Shaw", "given_name": "M. C.", "clpid": "Shaw-M-C" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Pask", "given_name": "Joseph A.", "clpid": "Pask-J-A" }, { "family_name": "Evans", "given_name": "Anthony G.", "clpid": "Evans-A-G" } ], "abstract": "The mechanical response of whisker-reinforced ceramics, which is dominated by interfacial chemistry-arid stress, is expected to vary as thermal mismatch stresses diminish and grain boundary phases soften with increasing temperature. To examine the temperature dependence of the toughening process two silicon carbide whisker-reinforced systems have been studied: alumina and mullite. The systems represent a range of thermal mismatch conditions and potential crack-whisker interactions including crack bridging, whisker pull-out and crack deflection. For both systems, fracture toughness and hardness are measured as a function of temperature. The fracture toughness of both materials shows little change to 1100\u00b0C. However, post-mortem fractography indicates that limited pullout occurs in the mullite/SiC_w system at elevated temperatures. Only whiskers oriented normal to the fracture plane are pulled out without fracture due to the additional bending stresses on the whiskers. In the alumina/SiC_w system, the mode of fracture remains invariant with temperature because of high whisker compressive stresses. These observations indicate that for randomly-oriented whiskers substantial toughening by pull-out is contingent upon low interfacial stresses coupled with high strength whiskers which can sustain large bending stresses.", "doi": "10.1007/978-1-4613-1933-7_92", "isbn": "978-1-4612-9074-2", "publisher": "Plenum Press", "place_of_publication": "New York, NY", "publication_date": "1987", "pages": "929-938" }, { "id": "authors:pv0pz-1x848", "collection": "authors", "collection_id": "pv0pz-1x848", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140915-114401795", "type": "book_section", "title": "TEM Studies of Dislocations in Deformed Ga_(x)In_(1-x)As Single Crystals", "author": [ { "family_name": "Rai", "given_name": "R. S.", "clpid": "Rai-R-S" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Guruswamy", "given_name": "S.", "clpid": "Guruswamy-S" }, { "family_name": "Hirth", "given_name": "J. P.", "clpid": "Hirth-J-P" } ], "contributor": [ { "family_name": "Bailey", "given_name": "G. W.", "clpid": "Bailey-G-W" } ], "abstract": "The control of dislocation density during the growth of GaAs and related\ncompounds is highly desirable for obtaining improved performance and\nreliability of opto-electronic devices. Doping of single crystal GaAs grown\nby the LEC process with Indium has been known to reduce the dislocation\ndensity significantly. Substitutional solid-solution strengthening of GaAs\nas an InAs unit been suggested to be responsible for reduction of\ndislocation density. To understand the mechanism involved in dislocation\ndensity reduction deformation tests have been performed on [001] oriented\nGa_XIn_(1-x)As single crystals in the temperature range 700-1100\u00b0C and this\npaper reports some results of the TEM characterization of dislocations in\nthese deformed single crystals.", "publisher": "San Francisco Press", "publication_date": "1987" }, { "id": "authors:384rk-gxf34", "collection": "authors", "collection_id": "384rk-gxf34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140918-144111634", "type": "book_section", "title": "Low Thermal Expansion Coatings for Carbon/Carbon Composites", "author": [ { "family_name": "Kerans", "given_name": "R. J.", "clpid": "Kerans-R-J" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Buckley", "given_name": "John D.", "clpid": "Buckley-J-D" } ], "abstract": "Two classes of materials are considered for low expansion protective\ncoatings for carbon/carbon composites. They include composites containing\nparticles which undergo allotropic phase transformations accompanied by\nnegative volume changes with increasing temperature and anisotropic oxides\nwhich demonstrate low expansion due to microcracking. Conditions for\nfailure of coatings by either cracking or spallation due to thermal\nmismatch are evaluated.", "publisher": "NASA", "publication_date": "1987" }, { "id": "authors:brgva-4nr58", "collection": "authors", "collection_id": "brgva-4nr58", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181330802", "type": "article", "title": "High-temperature hardness of Ga_(1\u2212x)In_xAs", "author": [ { "family_name": "Guruswamy", "given_name": "S.", "clpid": "Guruswamy-S" }, { "family_name": "Hirth", "given_name": "J. P.", "clpid": "Hirth-J-P" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "Substantial solid\u2010solution strengthening of GaAs by In acting as InAs_4 units has recently been predicted for an intermediate\u2010temperature plateau region. This strengthening could account, in part, for the reduction of dislocation density in GaAs single crystals grown from the melt. Hardness measurements at high temperatures up to 900\u2009\u00b0C have been carried out on (100) GaAs, Ga_(0.9975)In_(0.0025)As, and Ga_(0.99)In_(0.01)As wafers, all of which contain small amounts of boron. Results show a significant strengthening effect in In\u2010doped GaAs. A nominally temperature\u2010independent flow\u2010stress region is observed for all three alloys. The In\u2010doped GaAs shows a higher plateau stress level with increasing In content. The results are consistent with the solid\u2010solution strengthening model. The magnitude of the solid\u2010solution hardening is sufficient to explain the reduction in dislocation density with In addition.", "doi": "10.1063/1.337495", "issn": "0021-8979", "publisher": "American Institute of Physics", "publication": "Journal of Applied Physics", "publication_date": "1986-12-15", "series_number": "12", "volume": "60", "issue": "12", "pages": "4136-4140" }, { "id": "authors:cv30h-1t852", "collection": "authors", "collection_id": "cv30h-1t852", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331002", "type": "article", "title": "Frictional Stress Evaluation along the Fiber-Matrix Interface in Ceramic Matrix Composites", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Advani", "given_name": "S. H.", "clpid": "Advani-S-H" }, { "family_name": "Lees", "given_name": "J. K.", "clpid": "Lees-J-K" }, { "family_name": "Jinn", "given_name": "J.-T.", "clpid": "Jinn-J-T" } ], "abstract": "A finite element algorithm, developed for frictional contact problems, has been used to evaluate the shear stresses along the fiber-matrix interface in a ceramic composite and the load point fiber displacements dining fiber compression. The induced peak shear stress and the shear stress gradient were found to increase with increasing coefficients of friction. Calculated fiber displacements asymptotically decayed to the perfectly bonded condition as the coefficient of friction was increased. The computed average interfacial shear stress showed remarkable agreement with recent experimental findings hi the SiC-LAS system.", "doi": "10.1111/j.1151-2916.1986.tb07480.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1986-09", "series_number": "9", "volume": "69", "issue": "9", "pages": "C208-C209" }, { "id": "authors:hq2mj-yhs05", "collection": "authors", "collection_id": "hq2mj-yhs05", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-213750146", "type": "book_section", "title": "Mechanical Properties of Ga_(1\u2013x)In_xAs", "book_title": "Semiconductor-on-Insulator and Thin Film Transistor Technology", "author": [ { "family_name": "Guruswamy", "given_name": "S.", "clpid": "Guruswamy-S" }, { "family_name": "Hirth", "given_name": "J. P.", "clpid": "Hirth-J-P" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Chiang", "given_name": "A.", "clpid": "Chiang-A" }, { "family_name": "Geis", "given_name": "M. W.", "clpid": "Geis-M-W" }, { "family_name": "Pfeiffer", "given_name": "L.", "clpid": "Pfeiffer-L" } ], "abstract": "Substantial solid solution strengthening of GaAs by In acting as InAs_4 units has recently been predicted. This strengthening could account for the reduction of dislocation density in GaAs single crystals grown from the melt. High temperature hardness measurements up to 700\u00baC have been carried out on (100) GaAs and Ga_(0.9975)In_(0.0025)As wafers. Results show a significant strengthening effect in In-doped GaAs even at concentration levels of about 0.2 wt%. A temperature independent flow stress region is observed for both these alloys. The In-doped GaAs shows a higher plateau stress level compared to the undoped GaAs. The results are consistent with the solid solution strengthening model.", "doi": "10.1557/PROC-53-329", "isbn": "0931837189", "publisher": "Materials Research Society", "place_of_publication": "Pittsburgh, PA", "publication_date": "1986", "pages": "329-336" }, { "id": "authors:rgk4b-vj048", "collection": "authors", "collection_id": "rgk4b-vj048", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-203214745", "type": "book_section", "title": "Surface Energy as an Indicator of Interfacial Mechanical Response", "book_title": "Tailoring multiphase and composite ceramics", "author": [ { "family_name": "Godard", "given_name": "H. T.", "clpid": "Godard-H-T" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Tressler", "given_name": "Richard E.", "clpid": "Tressler-R-E" }, { "family_name": "Messing", "given_name": "Gary L.", "clpid": "Messing-G-L" }, { "family_name": "Pantano", "given_name": "Carlo G.", "clpid": "Pantano-C-G" }, { "family_name": "Newnham", "given_name": "Robert E.", "clpid": "Newnham-R-E" } ], "abstract": "Contact angles between silicon and a variety of silicon carbide-based\nfibers have been measured and correlated to the mechanical behavior of the\nfiber-matrix interface. Infiltration by the molten silicon into the fibers\nand/or reaction with excess carbon to form silicon carbide gives rise to low\ncontact angles and high toughness interfaces. It is suggested that the high\ntoughness of the interface is morphology-controlled.", "doi": "10.1007/978-1-4613-2233-7_54", "isbn": "0306423812", "publisher": "Plenum Press", "place_of_publication": "New York, NY", "publication_date": "1986", "pages": "687-696" }, { "id": "authors:qtbf5-ave12", "collection": "authors", "collection_id": "qtbf5-ave12", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331116", "type": "article", "title": "Evaluation of Reliability of Brittle Components by Thermal Stress Testing", "author": [ { "family_name": "Johnson-Walls", "given_name": "D.", "clpid": "Johnson-Walls-D" }, { "family_name": "Drory", "given_name": "M. D.", "clpid": "Drory-M-D" }, { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-A-G" }, { "family_name": "Marshall", "given_name": "D. B.", "clpid": "Marshall-D-B" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A thermal stressing technique was applied to evaluate two distinct flaw populations (surface and corner) in BaTiO_3 multilayer capacitors. The mechanical reliability of the capacitors was deduced by relating the thermal stress response to the mechanical strength of the material. The surface flaw population alone yields relatively high survival probabilities, whereas incorporation of the corner flaw population severely reduces the probability of survival.", "doi": "10.1111/j.1151-2916.1985.tb10143.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1985-07", "series_number": "7", "volume": "68", "issue": "7", "pages": "363-367" }, { "id": "authors:73npf-f4c50", "collection": "authors", "collection_id": "73npf-f4c50", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331228", "type": "article", "title": "Crack-Growth Resistance of Microcracking Brittle Materials", "author": [ { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-A-G" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "A mechanics model of microcrack toughening is presented. The model predicts the magnitude of microcrack toughening as well as the existence of R-curve effects. The toughening is predicated on both the elastic modulus diminution in the microcrack process zone and the dilatation induced by microcracking. The modulus effect is relatively small and process-zone-size-independent. The dilatational effect is potentially more substantial, as well as being the primary source of the R curve. The dilatational contribution is also zone-size-dependent. The analysis demonstrates that microcrack toughening is less potent than transformation toughening.", "doi": "10.1111/j.1151-2916.1984.tb18842.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1984-04", "series_number": "4", "volume": "67", "issue": "4", "pages": "255-260" }, { "id": "authors:3ce7d-tbj70", "collection": "authors", "collection_id": "3ce7d-tbj70", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210114-140535869", "type": "book_section", "title": "Observations of Intergranular, Crack Deflection Toughening Mechanisms in Silicon Carbide", "book_title": "Fracture in Ceramic Materials: Toughening Mechanisms, Machining Damage, Shock", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-Anthony-Glyn" } ], "contributor": [ { "family_name": "Evans", "given_name": "Anthony Glyn", "clpid": "Evans-Anthony-Glyn" } ], "abstract": "The fracture toughness of three silicon carbide-based materials were examined in the light of operative toughening mechanisms. Crack deflection along grain boundaries in a hot-pressed SiC-Al\u2082O\u2083 and a hot-pressed SiC-ZrO\u2082 provided notable toughness increases compared with a sintered alpha -SiC, which fractures transgranularly. The existence of a crack deflection mechanism was confirmed using scanning electron microscopy.", "isbn": "9780815510055", "publisher": "Noyes Publications", "place_of_publication": "Park Ridge, NJ", "publication_date": "1984", "pages": "99-108" }, { "id": "authors:czbme-g7c19", "collection": "authors", "collection_id": "czbme-g7c19", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-143540784", "type": "book_section", "title": "Microcracking Contributions to the Toughness of ZrO_2-Based Ceramics", "book_title": "Science and technology of zirconia II", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Claussen", "given_name": "Nils", "clpid": "Claussen-N" }, { "family_name": "R\u00fchle", "given_name": "Manfred", "clpid": "R\u00fchle-M" }, { "family_name": "Heuer", "given_name": "Arthur Harold", "clpid": "Heuer-A-H" } ], "abstract": "Analyses are presented to evaluate two microcrack toughening situations in\nZr_O2-based ceramics. The first analysis considers toughening due to stress-induced\nmicrocracking of residually strained monoclinic ZrO_2 particles. The second assesses\nmicrocracking that occurs as a consequence of the stress-induced tetragonal-monoclinic\ntransformation. Both toughening mechanisms are characterized by a\npermanent dilatational strain and a modulus reduction; however, only the latter may\nresult in a toughness enhancement or reduction. Conditions under which toughness\nenhancement and reduction are observed are established. The magnitudes of\ntoughening increases from transformation-toughening and microcrack-toughening\nare also compared.", "isbn": "0916094642", "publisher": "American Ceramic Society", "place_of_publication": "Columbus, OH", "publication_date": "1984", "pages": "293-305" }, { "id": "authors:x27xf-n8x34", "collection": "authors", "collection_id": "x27xf-n8x34", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20210114-141918270", "type": "book_section", "title": "On the Crack Growth Resistance of Microcracking Brittle Materials", "book_title": "Fracture in Ceramic Materials: Toughening Mechanisms, Machining Damage, Shock", "author": [ { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-Anthony-Glyn" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Evans", "given_name": "Anthony Glyn", "clpid": "Evans-Anthony-Glyn" } ], "abstract": "A mechanics model of microcrack toughening has been presented. The model predicts the magnitude of microcrack toughening as well as the existence of R-curve effects. The toughening is predicated on both the elastic modulus diminution in the microcrack process zone and the dilatation induced by microcracking. The modulus effect is relatively small and process zone size independent. The dilatational effect is potentially more substantial, as well as being the primary source of the R-curve. The dilatational contribution is also zone size dependent. The analysis demonstrates that microcrack toughening is less potent than transformation toughening, by virtue of the damaging effect of microcracks on the material ahead of the crack.", "isbn": "9780815510055", "publisher": "Noyes Publications", "place_of_publication": "Park Ridge, NJ", "publication_date": "1984", "pages": "109-136" }, { "id": "authors:5ye8q-q9a63", "collection": "authors", "collection_id": "5ye8q-q9a63", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-115438203", "type": "book_section", "title": "Toughening Mechanisms for Ceramics in Automotive Applications", "book_title": "Proceedings of the 12th Automotive Materials Conference", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "contributor": [ { "family_name": "Smothers", "given_name": "William", "clpid": "Smothers-W" } ], "abstract": "Insuring the strength of ceramic materials in automotive applications requires the\nunderstanding of the operative strength-determining parameters, one of which is\nthe fracture toughness. Toughening mechanisms in ceramics will be reviewed here,\nincluding crack shielding and crack interaction mechanisms. Also covered in this\nreview will be a discussion of surface strengthening effects, as well as recent\ndevelopments in ceramic matrix fiber composites. Experimental examples of each\nof the toughening mechanisms will be presented.", "doi": "10.1002/9780470320211.ch12", "isbn": "9780470374108", "publisher": "Wiley", "place_of_publication": "Hoboken, NJ", "publication_date": "1984", "pages": "408-439" }, { "id": "authors:z1jge-a1c40", "collection": "authors", "collection_id": "z1jge-a1c40", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331664", "type": "article", "title": "Intergranular Crack-Deflection Toughening in Silicon Carbide", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Evans", "given_name": "Anthony G.", "clpid": "Evans-A-G" } ], "abstract": "The fracture toughness of three SiC-based materials was examined and correlated to toughening mechanisms. Crack deflection along grain boundaries in hot-pressed SiC-Al_2O_3 and SiC-ZrO_2 provided notable toughness increases compared to sintered \u03b1-Sic, which fractures transgranularly. The existence of a crack-deflection mechanism was confirmed by scanning electron microscopy.", "doi": "10.1111/j.1151-2916.1983.tb10084.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1983-06", "series_number": "6", "volume": "66", "issue": "6", "pages": "C94-C96" }, { "id": "authors:ae5vw-a0v46", "collection": "authors", "collection_id": "ae5vw-a0v46", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331426", "type": "article", "title": "Crack deflection processes\u2014II. Experiment", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-A-G" } ], "abstract": "Two microstructural characteristics, particle morphology and size, have been examined with respect to toughening by crack deflection. Particle morphology effects were evaluated in a series of hot-pressed silicon nitrides comprised of rod-shaped grains of various aspect ratios and a bariumsilicate glass ceramic containing spherulites. Lithium-alumino-silicate glass ceramics containing Li_2Si_2O_5 lath-shaped crystals were studied for particle size effects. Independent measures of the fracture toughness and the crack deflection process were performed and results were correlated with a crack deflection model.", "doi": "10.1016/0001-6160(83)90047-0", "issn": "0001-6160", "publisher": "Elsevier", "publication": "Acta Metallurgica", "publication_date": "1983-04", "series_number": "4", "volume": "31", "issue": "4", "pages": "577-584" }, { "id": "authors:44yc7-qxt87", "collection": "authors", "collection_id": "44yc7-qxt87", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331325", "type": "article", "title": "Crack deflection processes\u2014I. Theory", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-A-G" } ], "abstract": "A fracture mechanics approach has been used to predict fracture toughness increases due to crack deflection around second phase particles. The analysis is based on a determination of the initial tilt and the maximum twist of the crack front between particles, which provides the basis for evaluating the deflection-induced reduction in crack driving force. Features found to be important in determining the toughness increase include the volume fraction of second phase, the particle morphology and aspect ratio, and the distribution of interparticle spacing. Predictions are compared with expected surface area increases.", "doi": "10.1016/0001-6160(83)90046-9", "issn": "0001-6160", "publisher": "Elsevier", "publication": "Acta Metallurgica", "publication_date": "1983-04", "series_number": "4", "volume": "31", "issue": "4", "pages": "565-576" }, { "id": "authors:6qnf8-59z32", "collection": "authors", "collection_id": "6qnf8-59z32", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331539", "type": "article", "title": "Characterization of AIN ceramics containing long-period polytypes", "author": [ { "family_name": "Van Tendeloo", "given_name": "G", "clpid": "Van-Tendeloo-G" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Thomas", "given_name": "G.", "clpid": "Thomas-G" } ], "abstract": "Two AIN-SiO_2 materials have been investigated by means of electron microscopy; fracture toughness has been used to characterize both materials. Three new long-period polytypes, close to the 2H hexagonal AIN structure, have been identified by high-resolution electron microscopy, namely 33R, 24H and 39R. These polytypes are built on the same stacking principle as those in the previously observed shorter polytypes in the AIN system. Indentation measurements indicate similar hardness and toughness for the different polytypes in these ceramics.", "doi": "10.1007/BF00560642", "issn": "0022-2461", "publisher": "Springer", "publication": "Journal of Materials Science", "publication_date": "1983-02", "series_number": "2", "volume": "18", "issue": "2", "pages": "525-532" }, { "id": "authors:3mj39-rk708", "collection": "authors", "collection_id": "3mj39-rk708", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140916-210935712", "type": "book_section", "title": "A Statistical Analysis of Crack Deflection as a Toughening Mechanism in Ceramic Materials", "book_title": "Measurements, transformations, and high-temperature fracture", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-A-G" }, { "family_name": "Drory", "given_name": "M. D.", "clpid": "Drory-M-D" } ], "contributor": [ { "family_name": "Bradt", "given_name": "Richard C.", "clpid": "Bradt-R-C" } ], "abstract": "A coupled stress intensity probabilistic treatment of toughening\nby crack deflection around spherical second phase particles\nis presented. Both the tilting of the crack around particles and\nThe twisting of the crack front between particles have been evaluated.\nImportant features of the analysis include particle volume\nfraction effects on the toughening increment, and the absence of\na particle size effect.", "isbn": "0306410222", "publisher": "Plenum Press", "place_of_publication": "New York, NY", "publication_date": "1983", "pages": "77-91" }, { "id": "authors:azm62-2b755", "collection": "authors", "collection_id": "azm62-2b755", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181331971", "type": "article", "title": "Glass microstructure characterization by laser light scattering, small angle X-ray scattering and electron microscopy", "author": [ { "family_name": "Rindone", "given_name": "G. E.", "clpid": "Rindone-G-E" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Kumar", "given_name": "B.", "clpid": "Kumar-B" }, { "family_name": "Olix", "given_name": "W. F.", "clpid": "Olix-W-F" }, { "family_name": "Sproull", "given_name": "J. F.", "clpid": "Sproull-J-F" } ], "abstract": "Transmission electron microscopy (TEM), small angle X-ray scattering (SAXS) and laser light scattering (LLS) have been used to characterize the microstructures of mixed alkali-lithia-potassia-silica glasses and soda lime silica glasses. In most cases the three methods complement one another very well. In the mixed alkali silicate glasses LLS measurements of particle size correlate very well with TEM measurements. In addition, there is a direct correlation between particle size measurements by both methods and flaw sizes calculated from strength measurements using the Griffith equation. In the soda lime silica system LLS measurements of the glasses prior to heat treatment in the temperature region of metastable liquid immiscibility correlate very well with SAXS measurements of the heat treated glasses. The merits of each method in studies involving these glass systems will be discussed.", "doi": "10.1016/0022-3093(82)90123-5", "issn": "0022-3093", "publisher": "Elsevier", "publication": "Journal of Non-Crystalline Solids", "publication_date": "1982-05", "series_number": "1-3", "volume": "49", "issue": "1-3", "pages": "253-262" }, { "id": "authors:s9pde-jkh66", "collection": "authors", "collection_id": "s9pde-jkh66", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181332773", "type": "article", "title": "Toughening of Ceramics by Circumferential Microcracking", "author": [ { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-A-G" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" } ], "abstract": "An approximate analysis is presented of the toughening induced by the incorporation of second-phase particles subject to microcracking. It is demonstrated that the toughening becomes appreciable for a narrow size distribution of particles of appropriate size. The magnitude of the toughening is determined by the mismatch strain (due to thermal contraction incompatibility) and the microfracture resistance of the particle/matrix interface. Implications for designing optimally tough ceramics are presented.", "doi": "10.1111/j.1151-2916.1981.tb09877.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1981-07", "series_number": "7", "volume": "64", "issue": "7", "pages": "394-398" }, { "id": "authors:8wa7m-jzh33", "collection": "authors", "collection_id": "8wa7m-jzh33", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181332665", "type": "article", "title": "Quantitative Studies of Thermal Shock Based Upon a Novel Test Technique", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Huang", "given_name": "M. D.", "clpid": "Huang-M-D" }, { "family_name": "Evans", "given_name": "A. G.", "clpid": "Evans-A-G" } ], "abstract": "A thermal shock test was designed which permits the thermal fracture resistance and the mechanical strength of brittle materials to be quantitatively correlated. Thermal shock results for two materials, Al_2O_3 and SiC, were accurately predicted from biaxial strength measurements and a transient thermal stress analysis (performed using a finite element method). General implications for the prediction of thermal shock resistance, with special reference to ceramic components, are discussed.", "doi": "10.1111/j.1151-2916.1981.tb09606.x", "issn": "0002-7820", "publisher": "Wiley-Blackwell", "publication": "Journal of the American Ceramic Society", "publication_date": "1981-05", "series_number": "5", "volume": "64", "issue": "5", "pages": "296-301" }, { "id": "authors:0rx18-j4g06", "collection": "authors", "collection_id": "0rx18-j4g06", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140908-181332978", "type": "article", "title": "Small Angle X-ray Scattering and Transmission Electron Microscopy of Water Containing Phase Separated Soda Lime Silica Glasses", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Rindone", "given_name": "G. E.", "clpid": "Rindone-G-E" } ], "abstract": "The phase separation characteristics of a soda-lime-silica\nglass composition located in the metastable liquid\nimmiscibility region were studied as a function of water\ncontent in the glass structure. The water content was\nvaried by the batching process, using dry and gel\nbatches, and by melting under different water vapour\npartial pressures. The glasses were analysed for their\nwater contents which were evaluated as a function of the\nraw materials and melting atmosphere. Variations in the\nphase separation characteristics as a function of water\ncontent were observed by small angle x-ray scattering\nmeasurements and transmission electron microscopy.\nThe most profound effect was an increase in nucleation\nfrequency with increasing water content in the glass.", "issn": "0031-9090", "publisher": "Society of Glass Technology", "publication": "Physics and Chemistry of Glasses", "publication_date": "1980-10", "series_number": "5", "volume": "21", "issue": "5", "pages": "171-177" }, { "id": "authors:5fhrq-tj346", "collection": "authors", "collection_id": "5fhrq-tj346", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140918-150539131", "type": "book_section", "title": "High temperature properties of sintered alpha silicon carbide", "author": [ { "family_name": "Coppola", "given_name": "J. A.", "clpid": "Coppola-J-A" }, { "family_name": "Srinivasan", "given_name": "M.", "clpid": "Srinivasan-M" }, { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Smoak", "given_name": "R. H.", "clpid": "Smoak-R-H" } ], "contributor": [ { "family_name": "S\u014dmiya", "given_name": "Shigeyuki", "clpid": "S\u014dmiya-S" }, { "family_name": "Sait\u014d", "given_name": "Shinroku", "clpid": "Sait\u014d-S" } ], "abstract": "Sintered alpha silicon carbides are being developed to meet the requirements\nof conventional and advanced heat engine systems. Through pressureless sintering,\nlow cost, near-net complex shapes requiring little finish grinding can be\nfabricated from this form of silicon carbide.\nThe use of ceramics such as silicon carbide as engine components requires\ndetailed data collection and understanding of material's performance especially\nat high temperatures. Much data have been generated on sintered alpha SiC (1-5)\nover the past two years. Specifically, it has been shown that the fast fracture\nstrength of a sintered alpha silicon carbide tested in air is constant from room\ntemperature to above 1400\u00b0 (2) and that an increase in strength has been\nobserved when tested in argon (1,2).\nSome physical properties of sintered alpha SiC are listed in Table 1. These\ndata are typical of the high purity, low porosity nature of a densified silicon\ncarbide. Figure 1 shows the four point bend strength of sintered alpha SiC as\na function of temperature.\nIt has been shown (3,4) that the strength of fine grain, less than 10 \u00b5m\naverage grain size, sintered alpha SiC is presently limited by the presence of\nprocessing defects. It has also been reported (4) that evidence of slow crack\ngrowth has been observed at 1500 \u00b0C in air for sintered alpha SiC having an\nextremely coarse grain structure. This coarse grain microstructure was caused\nby post-sintering heat treatment of a fine grain material promoting the occurance\nof exaggerated grain growth. An evaluation of various experimental techniques\nfor determining the fracture toughness (K_(Ic)) of sintered alpha SiC has also been\nreported (5).\nThis paper presents further work on the high temperature properties of\na sintered alpha SiC. Specifically, data on the oxidation behavior and stress-rupture\nas a function of temperature and atmosphere will be presented.", "publisher": "Gakujutsu Bunken Fukyu-kai", "publication_date": "1979" }, { "id": "authors:p7tpb-tsa51", "collection": "authors", "collection_id": "p7tpb-tsa51", "cite_using_url": "https://resolver.caltech.edu/CaltechAUTHORS:20140909-211212745", "type": "article", "title": "The separation, identification and characterization of radioactive particles in topsoil", "author": [ { "family_name": "Faber", "given_name": "K. T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Landingham", "given_name": "R. L.", "clpid": "Landingham-R-L" } ], "abstract": "We have developed and used a method of isolating, identifying and characterizing low-level concentrations (in the parts per billion range) of radioactive debris in topsoil samples from Area 13 of the Nevada Nuclear Test Site. This method would be applicable in studies of high-density particles dispersed to such a degree that they are below normal detection levels. We used wet sieving and continuous centrifugal sedimentation in dense liquids to separate the desired particles, monitoring the radioactivity throughout the separation process. The particles were then characterized with the aid of the scanning electron microscope (SEM) and analyzed in the SEM by X-ray fluorescence. Elements identified on these particles were as follows (in order of highest to lowest intensity): Si, Al, Fe, Nb, Sn, Ca, I, Ti, K, Cs, In, Zn and Pu.", "doi": "10.1016/0032-5910(77)87008-3", "issn": "0032-5910", "publisher": "Elsevier", "publication": "Powder Technology", "publication_date": "1977-03", "series_number": "2", "volume": "16", "issue": "2", "pages": "209-216" } ]