ZHAI Fengrui 1, SHAN Ke 1, LI Nan 1, YI Zhongzhou 1, LU Min 1, XIE Zhipeng 2
(1. Honghe University, Mengzi 661199, Yunnan, China; 2. State Key Laboratory of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China)
Abstract: The hexagonal boron nitride (h-BN) ceramics were prepared by low temperature hot-pressing sintering (HP) with high purity h-BN powders as raw materials and B2O3 as a sintering aid. The effects of sintering temperature and sintering pressure on the densification, mechanical properties and microstructure of h-BN ceramics were investigated. The results show that increasing sintering temperature and sintering pressure can obviously improve the density and flexural strength of h-BN ceramics. However, the increase of fracture toughness is small. The better comprehensive performance is obtained at 1450°C under 30 MPa, and the relative density, flexural strength and fracture toughness are about 96%, 90 MPa and 2.76 MPa·m1/2, respectively. SEM analysis shows that h-BN ceramics with uniform and fine grains can be obtained by hot-pressing sintering at lower sintering temperature, and the grain size increases slightly with the increase of sintering temperature. While the larger fracture toughness value is caused by the influence of grain size. In addition, the fine flake grains are conducive to the movement of grains and can promote the sintering and densification of h-BN ceramics.
Key words: boron nitride ceramics; low temperature sintering; densification; mechanical properties