Silicon carbide coated carbon fibre tows by chemical vapour deposition

Small diameter ceramic fibres have been produced by coating commercial carbon fibre tows with silicon carbide coatings. In a cold wall reactor a deposition rate of more than 30 nm.s(-1) was obtained in static tests. A very high conversion efficiency of trichloromethylsilane was obtained (12% per pass). Fibres retained good tensile strength (1.7-2.5 GPa) and tow flexibility; coatings up to 3 mu m thick have fewer than 5% bridging fibres. Bridging was suppressed by continuous agitation of the fibres by Lorentz forcing during deposition. A hot-wall reactor was designed to produce continuous tows of 12 000 silicon carbide coated fibres. This equipment has been used to deposit 1 mu m coatings on unsized, untwisted commercial carbon fibre.