基于第一抗热震因子的BN纳米管/Si_3N_4复合材料抗热震性能评价

利用Kingery抗热震断裂理论构建了BN纳米管(BNNTs)强韧化陶瓷复合材料的第一抗热震因子模型,通过真空热压烧结法制备了四组BNNTs含量分别为0.5wt%、1.0wt%、1.5wt%和2.0wt%的BNNTs/Si_3N_4复合材料,并采用水浴淬冷法和三点弯曲法测试了复合材料的抗热震性能(震后弯曲强度和临界热震断裂温差)。测试结果验证了在急剧加热和急剧冷却条件下第一抗热震因子模型的正确性。结果表明:添加BNNTs使BNNTs/Si_3N_4复合材料第一抗热震因子增大,抗热震性能提升。分布在晶界上的BNNTs起到裂纹钉扎、桥联和裂纹偏转作用,增加了裂纹扩展的阻力;纳米管孔隙的存在改变了裂纹扩展路径,提高了BNNTs/Si_3N_4的断裂韧度,从而有效提高了其抗热震断裂能力。

Evaluation of thermal shock resistance of BNNTs/Si3N4 composites based on first heat shock factor

The first heat shock factor model of BNNTs reinforced ceramic composites was constructed based on Kingery thermal shock theory.The BNNTs/Si3N4 composites with mass fractions of 0.5wt%, 1.0wt%, 1.5wt% and 2.0wt% were prepared by hot pressed sintering process.The thermal shock resistance of the BNNTs/Si3N4 composites, including bending strength after thermal shock and critical fracture temperature difference, was tested by water bath quenching and three point bending method.The first heat shock factor model is verified by the thermal shock resistance test, which indicates that the thermal shock performance of BNNTs/Si3N4 is enhanced by the BNNTs.BNNTs which are distributed on the grain boundary make the crack pinned and deflected, increasing the crack propagation resistance.Moreover, the hole of the nanotube changes the crack propagation path, improving the fracture resistance and thermal shock resistance of the BNNTs/Si3N4 composites.