LaB_(6)改性C/C-ZrC-SiC复合材料的制备及其抗烧蚀性能

Preparation and Ablation Properties of LaB_(6)-Modified C/C-ZrC-SiC Composites

采用料浆浸渍结合树脂浸渍裂解法制备了含质量分数9.73%LaB_(6)的LaB_(6)-C/C预制体,再利用反应熔体浸渍法(RMI)制备了LaB_(6)改性C/C-ZrC-SiC复合材料,考察了材料的微观结构和烧蚀行为,探究LaB_(6)对材料抗烧蚀性能的作用机理。结果表明:在热流密度为2380kW/m^(2)的氧乙炔焰烧蚀120s后,LaB_(6)改性C/C-ZrC-SiC复合材料的质量烧蚀率和线烧蚀率分别为1.05×10^(-3)g/s和2.17×10^(-3)mm/s,较未改性C/C-ZrC-SiC复合材料分别降低了74.8%和61.9%。烧蚀过程中,LaB_(6)发生氧化反应生成La_(2)O_(3)和B_(2)O_(3),La_(2)O_(3)与ZrO_(2)之间的固溶作用以及化学反应,再加之液态B_(2)O_(3)具有促进固相反应传质的作用,使得材料表面形成大面积连续稳定的ZrO_(2)-La_(2)Zr_(2)O_(7)-La_(0.1)Zr_(0.9)O_(1.95)熔融态保护层,这是材料优异抗烧蚀性能的主要原因。

LaB_(6)-C/C preform containing 9.73wt%LaB_(6)was prepared by slurry impregnation combined with resin infiltration pyrolysis,and then LaB_(6)-modified C/C-ZrC-SiC composites were obtained by reactive melt impregnation(RMI).The microstructure and ablative behavior of the composites were studied,and the effect mechanism of LaB_(6)on the ablation properties of the composites was investigated.The results show that after oxyacetylene ablation at the heat flux of 2380 kW/m^(2) for 120 s,the mass ablation rate and linear ablation rate of LaB_(6)-modified C/C-ZrC-SiC composites are 1.05×10^(-3) g/s and 2.17×10^(-3) mm/s,which are 74.8%and 61.9%lower than those of unmodified C/C-ZrC-SiC composites,respectively.During ablation,LaB_(6)is oxidized to La_(2)O_(3) and B_(2)O_(3),the solid solution and chemical reaction occur between La_(2)O_(3) and ZrO2,and the liquid B_(2)O_(3) can promote mass transfer in solid phase reaction.These phenomena jointly result in the formation of a large area of continuous and stable ZrO2-La2Zr2O7-La0.1Zr0.9O1.95 molten protective layer on the material surface,which is the main reason for the excellent ablation performance of the material.