High-temperature stability of SiC-based ceramics has beenwell-known, and therefore its composite materials have beeninvestigated for the application to thermostructural materials.However, well-known SiC-based fibers and matrix- materials stainedwith salt are easily oxidized at high temperatures in air. This wouldbe serious problem when these materials are used near the ocean or ina combustion gas containing alkali elements. We have developed a newtype of sintered SiC fiber with prominent alkali resistance. Thisfiber also shows highstrength, high-modulus, excellenl high-temperature stability and superior creep resistance. Moreover, thisfiber indicated very high thermal conductivily about 20-fold largerthan ordinary SiC based fibers. Furthermore, we also have developed anew type of sintered SiC fiber- bonded ceramics using an intermediatefiber for preparing above mentioned fiber. This composite materialmaintained initial strength up to 1600 deg C, and what is more,showed very high fracture energy and thermal conductivity.
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