The low oxygen permeability of the (La₂Zr_xO_y-ZrO₂)@ZrC coating contributed to the superior ablation performance of the modified C/C composites in a simulated atmospheric re-entry environment

To enhance the ablation resistance of ultra-high temperature ceramic (UHTC) coatings on modified C/C composites, doping is often adopted to increase melt viscosity, yet it may simultaneously accelerate oxygen permeation. In this work, a composite oxide (La₂Zr_xO_y-ZrO₂) coated ZrC powder was synthesized via a sol-gel method and deposited as a (La₂Zr_xO_y-ZrO₂)@ZrC coating onto a SiC-interlayered C/C substrate by supersonic atmospheric plasma spraying. Plasma ablation tests were performed on coated nose-cone-shaped specimens under multiple incidence angles to better simulate realistic spacecraft re-entry conditions. The coating exhibited outstanding ablation resistance, with mass and linear ablation rates as low as 0.083 mg/s and 1.67 μm/s, respectively. A stable oxygen barrier, composed of monoclinic ZrO₂ crystals and molten La₂Zr₂O₇, formed during ablation, effectively impeding oxygen penetration without rare-earth dissolution into the ZrC oxide. This study confirms that a core-shell structured composite oxide coating can provide durable protection for C/C composites under extreme conditions.