Effect of the properties of a carbon substrate on its reaction with silica for silicon carbide formation

Abstract

The carbothermal formation of silicon carbide is studied in the case of carbon fibres coated with a continuous silica film obtained by a solgel process. The paper discusses the influence of the properties of the carbon fibre on the yield, the morphology and the structure of the as-obtained SiC material. Two types of carbon fibres heat-treated at 1200 and 2500 °C and representative of a non-graphitized and a graphitized carbon were selected, respectively. The SiO 2-coated fibre was heat-treated in the temperature range (1400–1650 °C) in argon and further characterized by X-ray analysis. Cubic (β) silicon carbide is obtained above 1400 °C for these experimental conditions and its shape is similar to that of the SiO 2-coated fibre. In the case of a graphitized fibre the conversion of SiO 2 into SiC tends to decrease and the formation of SiC whiskers is observed. It is established that the reactivity of the graphitized carbon surface with SiO (gaseous intermediate of the carbothermal reaction) is lower compared to that of a non-graphitized carbon fibre.