Enhanced thermal shock resistance of BN-based composites sintered by hot-pressing with the introduction of nano oxides

Abstract

In this study, the BN-SiC composites were enhanced using individual or composite nano additives (Al2O3, ZrO2) sintered by hot pressing. The phase compositions, microstructure, mechanical properties, and thermal shock resistance of BN-based composites were comparatively investigated. The results showed that: the collaborative addition of nano ZrO2 or Al2O3 stimulated the solid diffusion and promoted the densification behavior. Meanwhile, the BN-SiC composites presented suitable development of BN plates and exhibited excellent structural uniformity due to the nano particles incorporated. As a result, the flexural strengths and fracture toughness of 10 wt% Al2O3 and 10 wt% ZrO2 improved significantly to 355.7 MPa and 5.78 MPa m1/2, respectively. In addition, BN-based composites exhibited excellent thermal shock resistance up to temperature difference (ΔT) = 1200 °C, where no catastrophic failure has been observed for all the specimens except the individual 10 wt% Al2O3 containing specimens. The main enhancing mechanisms were attributable to the “crack deflection”, “crack bridging” and “pulling-out” of BN plates, and the prolonged crack propagation paths along the fine particles.