Spark Plasma Sintering and Characterization of Mixed <i>h</i>-BN Powders with Different Grain Sizes

Mixtures of two grades of hexagonal boron nitride ( h -BN) powder differing in their grain size and crystallinity were spark plasma sintering in a vacuum. The influences of the mixing ratio of h -BN powders on the densification, microstructure and mechanical properties were investigated in detail. The results show that the smaller grain size, the lower crystallization degree and the higher density and mechanical properties. While the orientation degree of flake h -BN grains can be greatly enhanced by using h -BN powder with larger particle size. As the increasing of nanometer h -BN powder adding amount, the relative density has the same “V” shape changing trends with mechanical properties. In addition, the orientation of boron nitride grains varied widely, and a nearly isotropic material was prepared from a mixture containing 90wt.% nanometer powder.