Fibrous Monolithic Ceramics: I , Fabrication, Microstructure, and Indentation Behavior
نویسندگان
چکیده
Monolithic ceramics have been fabricated from coated green fibers to create fibrous microstructures. The fibrous monoliths consist of high aspect ratio polycrystalline regions (cells) of a primary phase separated by thin secondphase regions (cell boundaries) designed to improve fracture resistance. The cells are the remnants of the green fiber which consists of ceramic powder and a polymer binder. The coating applied on the green fiber forms the cell boundaries. Fabrication and microstructure are described for fibrous monoliths in the SiC/graphite, silicon nitride/BN, alumina/alumina-zirconia, alumina/aluminum titanate, alumina/nickel and Ce-TZP/alumina-Ce-zirconia systems. The SiC/grAphite fibrous monolith displays noncatastrophic Failure in flexure, with shear delamination along the weak graphite layers. Indentations in SiC/graphite cause cells to spall, with crack arrest and extrusion of graphite from the cell boundaries. Crack deflection and spalling of cells are also observed in alumina/alumina-zirconia fibrous monoliths. In the Ce-TZP/alumina system, transformed regions around indentations are significantly modified by the alumina-containing cell boundaries.
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