COATING OF CARBON-FIBERS WITH AMORPHOUS SIC FILMS AS DIFFUSION-BARRIERS BY CHEMICAL-VAPOR-DEPOSITION WITH TRIISOPROPYLSILANE

Carbon fibers 6.5 mu m in diameter were coated with amorphous SiC film s by chemical vapor deposition at temperatures as low as 800-900 degre es C, using triisopropylsilane in hydrogen. The morphology of the film s was strongly affected by the reaction conditions. The tensile streng th of the coated fibers was decreased by the coating, but was little a ffected by the coating method if smooth and tight films were formed. S iC films formed under optimized conditions effectively protected the f ibers from oxidation. When the fibers were enclosed with aluminum at 1 000 degrees C, SiC films effectively retarded the diffusion of aluminu m.