Hierarchical-design coating on C/C composite with excellent combination of autonomously self-healing ability and low oxygen permeability from 973 K to 1273 K

Abstract

Antioxidant SiO2 coating exhibits low cost and great compatibility with existing uses, but is strongly limited by its poor fluidity and high oxygen permeability from 973 K to 1273 K. Therefore, the hierarchical-design Glass/MoSi2-B2O3@SiO2-SiC coating was fabricated on C/C composite by a simple embedding method, and followed by a hot dip process. This composite yielded excellent combination of long-term antioxidant abilities and thermal shock resistances. As oxidized at 973 K for 1500 h, its mass loss was 0.35 %, and only 0.66 % at 1073 K for 2600 h. After thermal shocks 270 times, the weight loss was only 0.56 %. Interestingly, the Glass/MoSi2 coating acted as a self-healing encapsulation shelter against oxygen, whilst the B2O3@SiO2 layer yielded stable healing effect. The B2O3@SiO2 microcapsule facilitated the activation of B2O3, SiO2 phases, and borosilicate glass sequentially as temperature rose, leveraging their unique advantages in defect healing. Through the synergistic effects of interface encapsulation and defect self-healing, the oxygen kept osmotic diffusion. This study underscores the significance of hierarchical designs in coatings, facilitating structure optimizations and enhancing antioxidant capabilities at multiple levels.