Si-C-N_(np)/Si_3N_4复合材料的室温和高温显微结构与力学性能

Microstructure and Mechanical Properties of Si_3N_4/Nano-sized Si-C-N Powders at Room and Elevated Temperature

以 Si- C- N纳米微粉为增强相 ,Si3N4 为基相 ,采用热压的方法制备了 Si Cp/ Si3N4 纳米复相陶瓷。应用扫描电镜 (SEM)、高分辨透射电镜 (HRTEM)对其结构进行了观察 ,并讨论了结构与性能之间的关系。结果表明 ,所得的 Si Cp/ Si3N4 复相陶瓷的室温力学性能比氮化硅单相陶瓷有较大的提高 ,而 135 0℃断裂韧性达 14 .6 6 MPa· m1 / 2 。Si C微晶在晶粒内和在晶界玻璃相内的钉扎作用是材料高温性能提高的主要因素。

Nano sized Si C N powders mixed with Si 3N 4 ,Y 2O 3,La 2O 3 was hot press sintered to form the SiC/Si 3N 4 composites The microstructure of the composite was observed by means of SEM and HRTEM The results show that the toughness and three point bending strength of the composite at room temperature is higher than those of monolithic Si 3N 4 The fracture toughness at room temperature and 1350℃ is 11 78 MPa·m 1/2 and 14 69 MPa·m 1/2 respectively The bending strength at room temperature and 1350℃ is 934MPa and 696MPa respectively the pinning effect of the SiC micro crystal in Si 3N 4 grain and in grain boundary glass phase prevents the strength loss and increases the toughness of the composites at elevated temperature