Ablation resistance of C/C-SiCo nanoporous ceramic composites with TaSi2-MoSi2-ZrB2-borosilicate glass coating

The development of high-speed aerial vehicles urgently requires high-performance integrated materials for ablation resistance, thermal insulation and oxidant protection under high temperature. The previously prepared carbon aerogel composites (C/CA), with ultra-high temperature thermal insulation properties, were impregnated with SiCO precursor sol and pyrolysed in nitrogen atmosphere at 1200?C. The impregnation/pyrolysis process was performed once, twice and thrice to obtain three different C/C-SiCO nanoporous ceramic composites. Further, TaSi2-MoSi2-borosilicate glass (TM-BG) coating or TaSi2-MoSi2-ZrB2-borosilicate glass (TMZBG) coating was prepared on the surface of the C/C-SiCO through slurry brushing combined with graphite powder embedded sintering process. By simulating the actual application environment through oxygen acetylene flame ablation test, the ablation resistance of the samples was studied and their oxidation mechanism was analysed. The results show that the ablation rate of the C/C-SiCO after 200 s ablation at 1600 ?C decreases with the increase of the number of impregnation/pyrolysis steps and that the ablation resistance of the coating modified C/C-SiCO was significantly enhanced. The addition of ZrB2 to the coating improves the compatibility between the substrates and the coating, and the TMZ-BG coated sample has better ablation resistance. At high temperature, the borosilicate glass in the coating is in a viscous flow state. Meanwhile the SiO2 generated by the oxidation of other silicide raw materials forms a dense glass layer on the coating surface, which can be used as an oxygen barrier to provide better protection for the substrates. The coating-modified C/C-SiCO porous ceramic composites are expected to be used as a high-temperature ablation-resistant material for the thermal protection system of new aerospace vehicles.