Temperature-responsive self-healing coating with excellent resistances to oxidation and thermal shock from core-shell SiB6@Al2O3 microcapsule

To improve the oxidation resistance of carbon/carbon (C/C) composites at intermediate temperatures, we present a novel design concept for an antioxidative coating that incorporates ceramic microcapsules engineered for self-healing and in situ toughening. These microcapsules, featuring a SiB 6 @Al 2 O 3 core-shell structure, were synthesized via a sol-gel process and embedded into a SiB 6 @Al 2 O 3 -SiC-C/C composite through dip-coating. Upon crack formation, the microcapsules rupture, releasing a healing agent that facilitates crack closure. Concurrently, the oxidation product SiO 2 from the core reacts with Al 2 O 3 , forming mullite whiskers at the damage site, thereby enhancing toughness. This combined self-healing and toughening mechanism significantly enhances the antioxidative performance of the coating. After 540 hours of exposure to an oxidizing environment at 1573 K, the coating demonstrated minimal oxidation, with a weight loss of just 0.27% and a specific weight loss of 6.80×10 -4 g/cm 2 .