Boron nitride composites by chemical vapor deposition

Composites of boron nitride (BN) were made by the chemical vapor deposition of a BN matrix on a BN felt fiber substrate. Reactant gases were boron trifluoride and ammonia. The composites had a relatively high density (1.70 g/cm$sup 3$), a crystallite size L/sub C/ = 150 A, and an interlayer spacing d$sub 002$ = 3.35 A. Measurements of elastic modulus and thermal conductivity and expansion showed some anisotropy as a result of the preferred fiber orientation of the substrate. (7 tables, 5 fig) (auth)