In-situ PIP-SiC NWs-toughened SiC–CrSi₂–Cr₃C₂–MoSi₂–Mo₂C coating for oxidation protection of carbon/carbon composites

A novel precursor infiltration and pyrolysis (PIP) technique was used to in-situ synthesize SiC nanowires (NWs) on C/C composites, and then pack cementation was applied to prepare a silicide coating. The results show that the NWs could not only grow uniformly on the C/C surface but also be synthesized in some microholes through PIP technique. During thermogravimetry tests from 800 °C to 1400 °C in simulated air, the mass loss of the coated specimen decreased from 11.8% to 1.5% after incorporating PIP-SiC NWs. The introduction of PIP-SiC NWs also increased the thermal shock resistance of the coated specimens. After 24 times thermal cycles between room temperature and 1500 °C, the final mass loss reduced from 3.23% to 0.37%. The improvement of thermal shock resistance of the coated specimens was owing to the nanoscale toughening mechanism including pulling-out, debonding and bridging of PIP-SiC NWs. In addition, NWs at the coating/substrate interface could play as a barrier to restrain the propagation of microcrack and thus decreased the size of micocrack.