Long-term and cyclic ablation behavior of La2O3 modified Cf/ZrB2-SiC composites at 2500 ℃

In this work, long-term and cyclic ablation behavior of the La2O3 modified Cf/ZrB2-SiC composites were studied by air plasma torch at 2500 ℃. It is indicated that a micron-sized ZrO2-La2O3-SiO2 liquid phase layer forms on the ablation surface at 2500 ℃, which reduces the evaporation of SiO2 and decreases the mass recession rates of the composites. However, the ZrO2-La2O3-SiO2 liquid phase layer exhibits poor structure stability. In addition, the La2O3 weakens the pinning effect of bulk ZrO2. Consequently, the oxide layer with low viscosity tends to sputter out due to the mechanical scouring by plasma flame. Therefore, the linear recession rates of the composites are increased during cyclic ablation with the increase of the La2O3 content.