直写成型h-BN增强SiCw/SiC陶瓷基复合材料中温抗氧化性能研究

Study on Medium Temperature Oxidation Resistance of h-BN Reinforced SiCw/SiC Ceramic-based Composite Formed by Direct Ink Writing Molding

采用直写成型与先驱体转化相结合的工艺制备了h-BN增强SiCw/SiC陶瓷基复合材料。复合材料打印构件氧化后在外壳表面生成了玻璃态氧化膜,具有独特的流体壳加氧化膜的复合结构。相较于普通SiC陶瓷的SiO_(2)氧化膜,玻璃态硼硅酸盐氧化膜能更有效地降低氧向复合材料内部扩散的速率,从而使复合材料的氧含量从12.33%降至5.75%。此外,适量的增强相(如h-BN/PCS=0.5)能进一步改善复合材料的抗氧化性能,其在800℃、900℃、1 000℃和1 100℃氧化后的增重变化不大,生成的玻璃态氧化膜完整且连续,能修补氧化表面的裂纹和孔隙,提高材料致密度,减少氧向材料内部扩散的路径。

h-BN reinforced SiCw/ SiC ceramic-based composites were fabricated by a technology combining directink writing molding with precursor conversion. After being oxidized, the printed composite components formedglassy oxide film on the surface of shell, had a unique composite structure consisting of fluid shell and oxide film.Compared with the SiO2 oxide film of ordinary SiC ceramics, the glassy borosilicate oxide film can more effectivelyreduce the diffusion rate of oxygen to the interior, and thereby reduce the oxygen content of the composite from12.33% to 5.75%. In addition, an appropriate amount of reinforcing phase (e.g., h-BN/ PCS = 0.5) can furtherimprove the oxidation resistance of the composite,their weights gain after being oxidized at temperatures of 800 ℃,900 ℃, 1 000 ℃, and 1 100 ℃ vary little, the generated glassy oxide film is complete and continuous, can repairthe cracks and pores on the oxidized surface, thus being capable of improving the compactness of the material andof reducing the path of diffusion of oxygen to the material interior.