Facilitating Si-O bond transformation in Si-Al-C-O fibers by fast Joule heating

The decomposition of the SiCxOy phase constitutes the critical pathway for the evolution of Si-Al-C-O fibers into highly crystalline silicon carbide (SiC) fibers. However, the traditional pyrolysis process is limited by the slow heating rate and fails to realize the efficient transformation of high-bond-energy Si-O bonds to Si-C bonds. In this work, a fast Joule heating (JH) method was employed, and the transformation of Si-O bonds to Si-C bonds and the growth process of beta-SiC microcrystals of Si-Al-C-O fibers under ultrafast high-temperature treatment were investigated, contrasting with the traditional heating method. Two types of Si-Al-C-O fibers, one retaining Si-CHx-Si moieties and the other fully inorganic, exhibit distinct transformation behaviors. In the Si-Al-C-O fibers containing residual Si-CHx-Si groups, the dehydrogenation reaction and SiCxOy phase decomposition reaction were coupled under ultrafast high-temperature treatment, which effectively reduced the transformation temperature of Si-O bonds to Si-C bonds and promoted the growth of beta-SiC microcrystals. The synergistic regulation strategy of fast JH and residual organic structures proposed in this study expands the paradigms for designing advanced precursor-derived ceramic materials.