1Institute of Space and Aeronautical Science, University of Tokyo, Tokyo
Chemical vapour deposition of silicon carbide onto carbon fibres has been carried out at temperatures between 1050 and 1400°C using trichloromethylsilane vapour carried with hydrogen. A carbon fibre tow used as a substrate was heated by the direct passage of an electric current. The flow rates of hydrogen gas were 70, 140 and 210 cm3/min. The temperature of trichloro-methylsilane vapour was 24±4°C. The total pressure of reaction gases was 1 atm. At the hydrogen flow rates of 70 cm3/min and 140 cm3/min, silicon carbide was deposited throughout the bulk tow, but the deposit obtained at the outer part of the tow was thinner than at the central part. The thickness of the deposit layer calculated as cylindrical surface deposition increased linearly with the deposition time, rapidly up to about 1 min and thereafter slowly. X-ray analysis revealed that the deposit was predominantly β -SiC. The activation energy for the deposition of silicon carbide was 61 kJ/mol, except when the deposition time was very short. The relation between the surface morphology of deposited silicon carbide and the coating conditions was investigated and three types of deposition were found.
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