The effect of aluminum content and oxygen content on the sintering performance of silicon carbide ceramic fibers

Aluminum-doped SiC ceramic fibers are attractive for their excellent mechanical properties and oxidation resistance at high temperatures. The oxygen and aluminum contents have significant effects on the mechanical properties of aluminum-doped SiC ceramic fibers. In this work, continuous SiC fibers were fabricated by the curing process, pyrolysis, and heat treatment. A two-stage curing approach was employed to tune the oxygen content of SiC fibers. The first stage involves air pre-oxidation, while the second stage employs thermal crosslinking. The aluminum content was tuned by altering the reaction ratio between liquid polycarbosilane and aluminum acetylacetonate. After optimization of Al and O content, SiC fibers with 0.6 wt% Al content and 10.32 wt% O content exhibited optimal properties, such as smooth surface, high mechanical properties (1.35 GPa) and high density structure. Polyaluminum carbosilane fibers with deficient oxygen content exhibited poor thermosetting properties, which caused melting or deformation when subjected to pyrolysis temperatures. Excessive oxygen content incorporation during pre-oxidation results in a loose structure, porous surface, and inferior mechanical properties (0.35 GPa). The limited Al concentration provides insufficient sintering aid activity, resulting in loose, porous fiber structures with inferior mechanical properties (0.91 GPa). Compared with the air pre-oxidation, the two-stage curing approach provides a cost-effective solution.