Development of high tensile strength silicon carbide fibre using an organosilicon polymer precursor

THE high tensile strength SiC fibre developed in our laboratory1–5 is extremely heat-resistant and its wettability by metals is good. Metal–matrix composites reinforced with the SiC fibre should therefore be of practical use. Polycarbosilane, the precursor of the fibre, is synthesised by thermal decomposition under high pressure of poly dimethylsilane in an autoclave. To produce the SiC fibre on an industrial scale, polycarbosilane needs to be produced in large quantities with high yield. The autoclave method requires a large amount of space, so the operation is inconvenient and uneconomic. We have, therefore, developed a new method of synthesising the polycarbosilane at normal pressure by adding several wt % of polyborodiphenylsiloxane6 to polydimethylsilane. The structure and properties of the new polycarbosilane, and the SiC fibre obtained from it are described here.