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

(1)由于以有机硅化合物为先驱体的无定形长碳化硅纤维具有有限的耐热温度，因此，长碳纤维与二氧化硅在几个减压条件下进行反应以制备多晶结构是一种根本不同的方法。只有在反应压力为-76 cmHg(表压)的情况下，才能得到柔软而柔软的纤维，这在扫描电子显微镜(SEM)中显示出独特的截面结构。(2)然而，发现这样得到的纤维的机械强度很低，这表明在成型过程中存在FW(纤维缠绕)等困难。然后，本研究的最初目的被迫改变为利用上述结论来提高碳纤维的抗氧化性的方法。结果表明，B-碳化硅涂层碳纤维在1400ﾟC下，在-76 cmHg(表压)下仅能保持几分钟的强度。空气氧化损失2wt-%的温度与未涂覆碳纤维的400ﾟC相比提高了100ﾟC以上。

(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.