Microstructural evolution and mechanical properties of h‐BN composite ceramics with Y ₂ O ₃ –AlN addition by liquid‐phase sintering

Abstract

Abstract Hexagonal boron nitride (h‐BN) composite ceramics were prepared by hot pressing with the addition of Y 2 O 3 and AlN. The effects of different Y 2 O 3 –AlN contents on microstructural evolution, mechanical properties and thermal diffusion coefficients of h‐BN composite ceramics were investigated. The results indicate that Y 2 O 3 –AlN forms a liquid phase during the sintering process, achieving a good wettability with h‐BN grains. In pure h‐BN ceramic and h‐BN composite ceramic with 40 wt% Y 2 O 3 –AlN, the h‐BN grains grow well when controlled through solid‐phase and liquid‐phase diffusion, respectively. With the increase in Y 2 O 3 –AlN content, mechanical properties and thermal diffusion coefficients of h‐BN composite ceramics first decrease and then increase, and the properties of h‐BN composite ceramic with 10 wt% Y 2 O 3 –AlN are the inflection points. Such properties are highly related to the phase compositions, porosity and microstructure.