Preparation, ablation behavior and mechanism of high-emissivity TaSi2/MoSi2/SiB4/borosilicate-glass coating prepared under controlled low oxygen partial pressure atmosphere

High-emissivity coatings are vital for thermal protection systems in hypersonic vehicles, but there is often a conflict between the oxidation behaviors of sintering aids and high-emissivity fillers during the preparation. Here, we propose an in-furnace oxygen partial pressure regulation strategy to fabricate TaSi 2 /MoSi 2 /SiB 4 /borosilicate-glass coatings on the oxidisable substrate of carbon-bonded carbon fiber composites. The oxidation behavior of fillers under various oxygen partial pressures were conducted, and their oxidative characteristics were established. Furthermore, the sintering atmosphere and temperature were optimized to achieve a dense, uniform microstructure. The coatings exhibited an average emissivity of ∼0.94 in the 2.5–8 µm wavelength range, and a total hemispherical emissivity of 0.906 over 2.5–25 µm. After ablation for 1200 s at 1650 ℃, the coatings maintained structural integrity, with a mass ablation rate of 2.25 × 10 −4 g/s, a linear ablation rate of 3.75 × 10 −4 mm/s, which resulted from the formation of porous yet robust Ta 2 O 5 -enriched outer layers.