Si_3N_4复合陶瓷材料的微观组织和断裂机制

使用AEM和HREM研究了添加纳米SiC颗粒和同时添加纳米SiC颗粒及SiC晶须的两种Si3N4 复合陶瓷材料的微观组织和断裂机制。结果表明 ,部分SiC颗粒分布在Si3N4 晶内 ,SiC晶须分布在Si3N4 晶粒之间 ,SiC颗粒和晶须与Si3N4 界面之间不存在第二相组织 ,非晶组织大多分布在Si3N4 三叉晶界。断裂裂纹主要沿晶界和相界面扩展 ,也可能穿过少数Si3N4 晶粒。当裂纹扩展遇到SiC颗粒和 /或SiC晶须时 ,会发生转弯 ,产生分枝裂纹或微裂纹并在Si3N4 晶内和Si3N4 晶粒的断裂表面引起晶格畸变 ,这降低了裂纹扩展能量 ,从而改善复合陶瓷材料的断裂强度和断裂韧性

Microstructure and fracture mechanism of Si_3N_4 composite ceramic materials

The microstructure and fracture mechanism of the Si 3N 4 composite ceramics with the addition of nano SiC powder, and nano SiC powder and SiC whisker were studied with AEM and HREM. A part of SiC particles distribute in the interior of Si 3N 4 grain, the SiC whiskers distribute between the Si 3N 4 grains and most of the amorphous structure is at the triple grain junction of the Si 3N 4. There is no second phase in the interface between the SiC particle, whisker and Si 3N 4. Fracture cracks expand mainly along the interface, also may pass through small amount of Si 3N 4 grains. Crack expanding direction is changed and branching crack and microcrack is created when the crack expanding meets the SiC particle and/or whisker. The lattice distortion is produced in the Si 3N 4 and fractured surface layer of Si 3N 4, that will decrease the expanding energy of crack and so improve fracture strength and fracture toughness of the composite ceramics.