Oxidation behaviour of Carbon/Carbon Composites impregnated with silica and silicon oxycarbide Original Research Article

Carbon/Carbon Composites made with high strength carbon fibers as reinforcement and pitch as matrix precursor have been impregnated with silica sol and silicon oxycarbide precursor (in sol form). On subsequent heat treatment to 1000°C and 1600°C, these composites have been found to exhibit slag and glassy coatings. Apparent density of the composites at different stages has been measured by water penetration while pore volume and pore size distribution have been measured by mercury porosimeter. The porosity of composites made with surface cleaned fibers and impregnated with silica has been found to increase while of those impregnated with silicon oxycarbide to decrease on heat treatment from 1000°C to 1600°C. Oxidation behavior and inhibition of oxidation of the impregnated composites has been studied using TGA in the temperature range 40–800°C (up to 20% burn off). The effect of impregnation towards oxidation inhibition has been studied through SEM investigation on partially oxidized samples. It has been found that silicon oxycarbide is better oxidation inhibitor than silica.