碳化硅晶须粉体热压烧结制备陶瓷的微结构与性能研究

SiC ceramics with high fracture toughness were fabricated by the hot-pressed sintering process, using β-SiC whiskers as raw materials and Al-B-C as sintering assistant. The effects of different sintering additives content (4%~14%), sintering temperature (1800~1875 ℃) and sintering time (30~75 min) on the relative density, microstructure and mechanical properties of SiC ceramics were investigated. The results show that the high content of sintering additives, high sintering temperature and the long sintering time can result in the high relative density and the big grain size of SiC ceramics. At the same time, the grain size of SiC ceramics grows up, the number of whiskers observed in the cross section of SiC ceramics is less, and the fracture toughness SiC ceramics is also weakened. The growth of SiC grains can be ascribed to the whisker dissolution and re-precipitation in the sintering assistant. There are a lot of whisker pull-out, whisker fracture and pores in the section of SiC ceramics with the less content of additive, the low sintering temperature and the short sintering time. At the meanwhile, the relative density of ceramics is relatively low. When the mass fraction of sintering additive is 10%, the hot-pressed time is 60 min and the hot-pressed temperature is 1850 ℃, the fracture toughness of SiC ceramics reaches the maximum value of (18.18±1.07) MPaom1/2, which is about 2.6 times higher than that of SiC ceramics prepared from SiC particle powder.