SiC-conversion coating from silica sol for improved oxidation resistance of carbon-fiber insulator in solar-cell ingot-growing crucibles

•SiC coating via a carbothermal reduction between the silica sol and graphite.•An economical process for large-capacity coating on carbon fibers was investigated.•A thin 30–80 nm polycrystalline SiC film gives a thermal stress resistance.•SiC coating for oxidation resistance maintains the adiabatic property. Carbon fibers, which have excellent mechanical and thermal properties, are used in many fields; however, they are very vulnerable to oxidation and have limited service life. Various studies have attempted to address this. In this study, a SiC–C composite material was prepared using a silica sol to coat the carbon surface and improve the oxidation resistance of a carbon-fiber insulator as a material for solar-cell ingot-growing crucibles. The SiC coating was formed on the carbon surface under various conditions by controlling the composition of the silica sol, and its characteristics were examined. Via SiC-conversion coating through a carbothermal reaction, a film of thickness 30–80 nm film was uniformly formed over the entire sample. In addition, the oxidation characteristics were enhanced by a factor of three to five, when compared with conventional carbon materials.