Development of Long-length Silicon Carbide Fiber for Ceramic Composite Material, having Super High Fracture Toughness

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(1)Since the long-length, amorphous SiC fiber being well-known, started from an organo-silicon compound as its precursor, has a limited heat-proof-temperature, a basically different approach was carried out by the reaction between long-length carbon fibres and SiO under several reduced pressures in order to prepare a polycrystalline structure. Only in the case of the pressure of -76cmHg(gauge)during the reaction, a soft and flexible fiber was obtained, which showed a unique sectional structure in SEM(Scanning Electron Microscopy).(2)It was, however, found that the fiber thus obtained showed a poor mechanical strength, suggesting a difficulty in the forming process such as FW(filament winding). Then, the initial purpose of this research was obliged to change to an approach to improve the resistivity of carbon fibres vs.oxidation by making use of above obtained conclusion. As a result, B-SiC coated- carbon fibres remaining enough strength was obtained at 1400ﾟC for only a few minutes under -76cmHg(gauge). The temperature where 2 wt-% was lost by air-oxidation, was found to be raised over 100ﾟC comparing with 400ﾟC observed in non-coated carbon fiber.