1994 Volume 102 Issue 1190 Pages 950-956
The conversion mechanism from oxidation-cured polycarbosilane to SiC ceramic fibers have been investigated. The fibers were heated isothermally and the conversion rate was determined by thermogravimetry at temperatures from 553 to 1673K in an Ar stream. The heat-treated fiber was examined by X-ray diffraction, infra-red spectroscopy, specific resistance measurement and tensile test. Below 800K, the fiber was in organic state. In the temperature range of 800 to 1000K, the conversion produced a very large increase in tensile strength. And then, in the temperature range from 1000 to 1500K, β-SiC crystallites grew and the maximum strength was obtained. Above 1500K, the pyrolysis coarsened the SiC crystals and lowered the strength. The conversion rate was described by the first order rate equation. The activation energy was 42.8kJ⋅mol-1. The conversion is considered to be controlled by the chemical reaction and the mass transfer through the gas film.
