Abstract: A process for the production of a composite material with matrix and reinforcing fibers of carbon. The process comprises: (a) forming a porous substrate (2) of carbon fibers; (b) covering the surface of each fiber wih a fine silicon carbide coating (6) by chemical vapor deposition; (c) shaping the substrate; (d) embedding the substrate in a carbon matrix (4) containing at most 20% by weight siliconcarbide; (e) covering the outer surface of the matrix with an outer silicon carbide covering (10) which contains cracks (12); and (f) filling the cracks in the outer covering with at least a borosilicate glass (16).

Abstract: Silicon carbide is deposted by chemical vapor deposition from a vapor source having a single molecular species that provides both the silicon and the carbon. The molecular species has the composition C.sub.n Si.sub.n H.sub.m, where m ranges from 2n+1 to 4n+1 inclusive and n ranges from 2 to 6 inclusive, and exhibits a primary pyrolysis mechanism producing reactive fragments containing both silicon and carbon atoms. Unbalanced decomposition paths are avoided. The silicon and carbon atoms are necessarily codeposited in equal numbers and at equal rates onto the substrate, producing stoichiometric deposited silicon carbide. Preferred molecular sources include H.sub.3 SiCH.sub.2 CH.sub.2 SiH.sub.3, a silacycloalkane of the form (--SiH.sub.2 CH.sub.2 --).sub.p, where p is 2, 3, 4, or 5, and a cyclic structure of the form (--SiH(CH.sub.3)--).sub.q, where q is 4 or 5.