In situ preparation of C-SiC O coatings with controllable composition on continuous oxygen-enriched SiC fibres

Oxygen-enriched SiC fibres derived from polycarbosilane are exposed to chlorine at 500 to 750 °C for up to 60 min. After chlorination, uniform coatings with controllable thickness are formed in situ on the SiC fibres. Evolution of the coating composition and its relation to the electrical properties are investigated. Results indicate that the porous nature of the coating realizes a reaction-controlling mechanism of the coating growth. By enhancing the chlorination temperature within the selected range, SiC, SiCO₃ and SiC₂O₂ phases in the fibre can be successively etched as free carbon to give C-SiC O hybrid coatings with increased content of C and decreased content of O. Accordingly, the specific resistivity of the coated SiC fibre declines continuously from 5.01 × 10⁶ to 0.39 Ω cm.