Formation of C-doped SiO2 coatings on carbon fibers by the sol-dipping process

The carbon-doped silicon dioxide (C-doped SiO2) coatings are prepared on the surface of carbon fibers by a facile sol-dipping method using tetraethoxysilane (TEOS) and diethoxydimethylsilane (DMDES) as precursors. The effect of heat treatment temperature and dipping times on the formation of the C-doped SiO2 coatings is studied. The structure and morphology of C-doped SiO2 coatings are analyzed by the scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The oxidation resistance of the carbon fibers with and without coatings is investigated by thermogravimetric analysis (TG) and static isothermal oxidation experiments. The results show that the C-doped SiO2 products obtained by pyrolysis of the gel at 900 degrees C displays high crystallinity and low carbon content. The continuous and uniform coatings with the thickness about 200 nm are formed after three times dipping, which improves the initial oxidation temperature of carbon fibers about 110 degrees C.