Abstract
The chemical stability of Si-C-O fiber at high temperatures was investigated. The amorphous fiber was pyrolyzed to crystallize to β-SiC under an atmosphere of inert gas at 1473K and higher. During the pyrolysis, both SiO and CO were evolved. The pyrolytic rate was described by the Avrami-Erofeev equation, and was determined by the crystal growth of SiC controlled by the diffusion of carbon in fiber. The oxide film, which was formed around the fiber by heating in O2 gas stream, was amorphous silica at the biginning of the oxidation and low temperatures, and changed to cristobalite at longer time and at high temperatures. The temperature dependence of the oxidation rate was complicated, because of wide variation in the morphology of the oxide film. The oxidation rate was analyzed by the parabolic rate law. The oxidation was controlled by the gaseous diffusion through the pores in the oxide film. This film suppressed the pyrolysis of the amorphous core of the fiber.
