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.