Infrared radiative performance and anti-ablation behaviour of Sm₂O₃ modified ZrB₂/SiC coatings

To improve the emissivity of ZrB₂/SiC coatings for serving in more serious environment, ZrB₂/SiC coatings with varying contents of high emissivity Sm₂O₃ were fabricated using atmospheric plasma spraying. The microstructure, infrared radiative performance and anti-ablation behaviour of the modified coatings were investigated. The results showed that as the content of Sm₂O₃ increased, the density of the coatings increased because of the low melting point of Sm₂O₃. When the content of Sm₂O₃ was 10 vol%, the coating had the highest emissivity in the 2.5–5 μm band at 1000 °C, up to 0.85, because of the oxygen vacancies promoting additional electronic transitions. Due to the high emissivity, the surface temperature of the coating modified with 10 vol% Sm₂O₃ decreased by 300 °C, which led to little volatilisation of the sealing phase. Further, the mass ablation ratio of the above coating was 3.19 × 10⁻⁴ g/s, decreasing 31% compared to that of a ZrB₂/SiC coating. The formed dense surface structure of the coatings showed considerable oxygen obstructive effects. These findings indicate that the modified coatings show considerable anti-ablation performance, which provides effective anti-ablation protection for the C/C composite substrate.