Controllable growth of (Hf, Zr)B2 solid solution coating via CVD for ultra-high temperature ablation of C/C composites

In this paper, we have successfully addressed the challenges of cracking and spalling in HfB2 coatings during ablation through the novel synthesis of (Hf, Zr)B2 solid solution coatings using the chemical vapor deposition (CVD) method. The ablation resistance of the coating exhibited an initially improving trend followed by a subsequently deterioration as the Zr content increased. When the Hf/Zr molar ratio in the (Hf, Zr)B2 solid solution coating was 1:1, a thicker Hf-Zr-O amorphous oxide layer was formed during ablation, which acted as a barrier, preventing the inward diffusion of oxygen. As a result, the (Hf0.5Zr0.5)B2 solid solution coating exhibited superior ablation resistance with a mass ablation rate of only -0.216 mg/s and a linear rate of -0.089 mu m/s. These findings underscore the enormous potential of boride solid solution UHTC as exceptional candidates for ultra -high temperature ablation resistant applications.