Chemical‐Vapor‐Infiltrated Silicon Nitride, Boron Nitride, and Silicon Carbide Matrix Composites

Abstract

Composites of carbon/chemical‐vapor‐deposited (CVD) Si3N4, carbon/CVD BN, mullite/CVD SiC, and SiC yarn/CVD SiC were prepared to determine if there were inherent toughness in these systems. The matrices were deposited at high enough temperatures to ensure that they were crystalline, which should make them more stable at high temperatures. The fiber‐matrix bonding in the C/Si3N4 composite appeared to be too strong; the layers of BN in the matrix of the C/BN were too weakly bonded; and the mullite/SiC composite was not as tough as the SiC/SiC composites. Only the SiC yarn/CVD SiC composite exhibited both strength and toughness.