定向SiC晶须增韧Si_3N_4陶瓷的制备及热震性能研究

Preparation and Thermal Shock Property of Si_3N_4 Ceramic Reinforced by Orientation SiC Whiskers

通过SiC晶须在载体纤维中定向挤出和热压烧结工艺制备了高度定向SiC晶须增韧Si_3N_4复合材料,利用SEM观察了晶须的定向方向和复合材料的断口形貌. 实验结果表明,70％以上SiC晶须的定向角在0～10°之间,具有较好的方向性.过高的烧结温度和晶须含量使材料抗弯强度降低。晶须定向方向的断裂韧性(单迫切口垂直于定向晶须)比横向方向高出20％.1000和500℃温差的热震实验表明,定向SiC晶须复合材料比随机SiC晶须复合材料的抗热震性能高得多.

A highly orientation SiC whisker reinforced Si3N4 composite was fabricated by fiber extrusion and hot-pressing technique, which SiC whiskers were unidirectional oriented in the extruded carrier fiber. Microstructure of the composites was observed by SEM. Whisker directions were image-processed to quantify SiC whisker orientation in the extruded fibers and the composites. Effects of sintering temperature and SiC whisker content on the flexural strength and fracture toughness of the composites were investigated. The experimental results show that the flexural strength and fracture toughness of the orientation SiC whisker toughened Si3N4 composites are higher than that of the random SiC whisker toughened Si3N4 composites after thermal shock experiment, in temperature of 1000°C and 500°C respectively.