[ { "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: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: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" } ]