Microstructural evolution and mechanical properties of h-BN composite ceramics with Y2O3–AlN addition by liquid-phase sintering

Abstract

Hexagonal boron nitride (h-BN) composite ceramics were prepared by hot pressing with the addition of Y2O3 and AlN. The effects of different Y2O3–AlN contents on microstructural evolution, mechanical properties and thermal diffusion coefficients of h-BN composite ceramics were investigated. The results indicate that Y2O3–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% Y2O3–AlN, the h-BN grains grow well when controlled through solid-phase and liquid-phase diffusion, respectively. With the increase in Y2O3–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% Y2O3–AlN are the inflection points. Such properties are highly related to the phase compositions, porosity and microstructure.