A Ceramic-Ceramic Composite with Low Dielectric Constant and Nonbrittle Failure

A composite having low dielectric constant and displaying nonbrittle failure was prepared using a cordierite-based matrix reinforced with boron aluminosilicate fibers. Since these fibers are normally chemically attacked by an oxide matrix during composite consolidation at high temperatures, good composite behavior required the application of a barrier/debonding coating on the fibers prior to composite fabrication. A boron nitride coating was applied using a known process, in which B{sub 2}O{sub 3} within the fiber diffuses to the surface and is nitrided. Fiber tensile testing showed that the coating process did not significantly lower the fiber strength, and the composite prepared with fibers coated by this process showed better mechanical properties than composites in which the barrier coating was either BN or carbon applied by chemical vapor deposition.