La₂O₃-modified C/C-ZrC composites with long-term cyclic ablation resistance

The compactness of in situ protective film for carbon-based composites during ablation is particularly important for improving their service life. Herein, La₂O₃-modified C/C-ZrC composites were designed by vacuum filtration combined with reactive melt infiltration to construct an in situ dense protective structure. Experimental results show that adding La element could improve the cyclic ablation performance of C/C-ZrC composites significantly. As the La₂O₃ addition amount is 5.6 wt.%, the linear ablation rate of La₂O₃-modified C/C-ZrC composites is –2.62 µm/s and 0.18 µm/s after exposure to an oxyacetylene flame (4.2 MW/m²) for 40 s and 240 s, far superior to that of C/C-ZrC composites (40 s, –6.2 µm/s). The excellent ablation resistance was attributed to the introduction of La element partially weakened Zr-O bonds to induce more oxygen vacancies, which facilitated the sintering of ZrO₂ and eventually promoted the compactness and tetragonal phase stability of the Zr-La-O layer.