A new type of skin-core structure SiC ceramic fibers was prepared from polycarbosilane by employing the curing process of alternating air and vacuum atmosphere periodically at thermal oxidation temperature. High-temperature degradation characteristics and mechanism of the skin-core structure SiC fibers were investigated at temperature from 1473 to 1773 K in air and nitrogen atmosphere, respectively. The ceramic fibers took place passive oxidation reaction in air atmosphere and underwent active oxidation in nitrogen. The main crystal phase of the high-temperature-treated ceramic fibers in air was alpha-cristobalite. By contrast, the alpha-cristobalite and beta-SiC phases can be detected in nitrogen atmosphere. Compared with traditional fine diameter SiC ceramic fibers, this novel skin-core structure made the SiC ceramic fibers form thinner ring-like layer in nitrogen which was beneficial to the integrity of microstructure and retain strength. The surface defect which was formed by high-temperature exposure had significant influence on mechanical performance. The ceramic fibers lost the strength completely at 1673 K under air atmosphere, while the strength can still be maintained about 0.48 +/- 0.06 GP at 1773 K in nitrogen. The skin-core structure was conducive to maintaining the high-temperature mechanical properties in oxygen-free atmosphere.
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