S. Baskaran et al., FIBROUS MONOLITHIC CERAMICS .1. FABRICATION, MICROSTRUCTURE, AND INDENTATION BEHAVIOR, Journal of the American Ceramic Society, 76(9), 1993, pp. 2209-2216
Monolithic ceramics have been fabricated from coated green fibers to c
reate fibrous microstructures. The fibrous monoliths consist of high a
spect ratio polycrystalline regions (cells) of a primary phase separat
ed by thin second-phase regions (cell boundaries) designed to improve
fracture resistance. The cells are the remnants of the green fiber whi
ch consists of ceramic powder and a polymer binder. The coating applie
d on the green fiber forms the cell boundaries. Fabrication and micros
tructure are described for fibrous monoliths in the SiC/graphite, sili
con nitride/BN, alumina/alumina-zirconia, alumina/aluminum titanate, a
lumina/nickel and Ce-TZP/alumina-Ce-zirconia systems. The SiC/graphite
fibrous monolith displays noncatastrophic failure in flexure, with sh
ear delamination along the weak graphite layers. Indentations in SiC/g
raphite cause cells to spall, with crack arrest and extrusion of graph
ite from the cell boundaries. Crack deflection and spalling of cells a
re also observed in alumina/alumina-zirconia fibrous monoliths. In the
Ce-TZP/alumina system, transformed regions around indentations are si
gnificantly modified by the alumina-containing cell boundaries.