A Thermoanalytical Study of the Conversion of Amorphous Si–Ti–C–O Fibers to SiC

Authors


nathan.s.jacobson@nasa.gov

Abstract

The conversion of polytitanocarbosilane fibers to SiC has been studied from 1400°C to 1600°C. Thermochemical modeling indicated the stable phases were SiC and TiC. Kinetics were studied with a thermogravimetric method and post heat-treatment phases, and microstructures were studied with X-ray diffraction and scanning electron microscopy. Kinetics exhibit a strong temperature dependence and an activation energy of 443.3 ± 11.7 kJ/mol. This suggests that a chemical reaction step is rate-limiting. X-ray diffraction shows the conversion of an amorphous phase to crystalline SiC. Electron microscopy shows the development of internal porosity and large grains on the fiber surface, particularly at the higher temperatures.

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