Infrared radiative performance and ablation resistance of coatings sprayed with Pr₆O₁₁ core–shell-structured ZrB₂-SiC powders

To improve the ablation resistance of carbon/carbon (C/C) composites, ZrB₂-SiC coatings sprayed with Pr₆O₁₁ core–shell-structured ZrB₂-SiC powders were prepared via atmospheric plasma spraying. The phase composition, microstructure, infrared radiative performance, and ablation resistance of the powders and coatings were investigated. The results show that the Pr₆O₁₁ shell is uniformly distributed around the induction plasma spheroidization-treated (IPS) ZrB₂-SiC powder and reduces the formation of low-emissivity phases, such as ZrO₂ and SiO₂, induced by oxidation during spraying. Stripe-shaped Pr₆O₁₁ appears in the coatings as a sealing phase, and the emissivity of the modified coating improves due to the high emissivity of Pr₆O₁₁. When the molar percent of Pr₆O₁₁ is 10 %, the coating indicates the highest emissivity (i.e. 0.94) in the 3–6 μm band at 750 °C. During a 60 mm-180 s oxyacetylene torch test, the surface temperature of the coating modified with 10 % Pr₆O₁₁ decreases by 150 K and reaches 1923 K owing to its high emissivity, resulting in minimal volatilization in the sealing phase. Furthermore, the mass ablation and linear ablation rates of the coating above are 1.67 × 10⁻⁴ g/s and 1.82 × 10⁻⁴ mm/s, respectively, which are 34 % and 42 % lower than those of unmodified coating. These results confirm that the introduction of Pr₆O₁₁ can increase the emissivity of the coating in the 3–6 μm band and provide considerable ablation protection for the C/C composites.