Dual-feedback healing mechanism redefining anti-oxidation coatings in fiber-reinforced composites

This study introduces a pioneering design concept termed the “dual-feedback healing mechanism”, which investigates the relationship between oxidation products and protective coatings. Specifically, it focuses on channeling oxidation products generated at exposed cracks in the substrate to interact with the antioxidant coatings, enabling a self-repair mechanism for cracks. BN_f/SiBN was chosen as the ceramic matrix, while the Si‒O‒Al system served as the antioxidant coating. The dynamic process of obtaining Si–O–Al (SOAC) coating involving the pyrolysis of organic precursors and the dual-feedback healing mechanism were systematically investigated. These findings indicate that when the temperature surpasses 1150 °C, the exposed BN fibers at the cracks are oxidized, transforming into B₂O₃(g). Subsequently, B₂O₃(g) reacts with SiO₂, forming a SiBO mixture. The mixture effectively diminishes the viscosity of the coating, enabling it to flow and form a fresh protective layer that effectively blocks O₂ infiltration. Consequently, after oxidation at 1500 °C, the coated samples experience a mere 3% weight loss. This technology emphasizes the interconnectivity during material transformation, utilizing matrix oxidation products as a driving force for self-healing of the coating. This approach achieves intelligent-like, targeted closure of oxygen pathways, thereby pioneering a novel concept and direction for the advancement of antioxidant coatings. Consequently, this approach not only enhances our understanding of the fundamental nature of “self-healing” but also holds significant potential in the development of reparable antioxidant coatings.