Densification behavior and microstructure evolution of hot-pressed SiC–SiBCN ceramics

Abstract

Densification behavior and microstructure evolution of hot-pressed SiC–SiBCN ceramics were studied between 1660°C and 1830°C. Polyborosilazane was chosen as the SiBCN precursor and pyrolyzed at 1000°C in inert atmosphere before use. Samples with SiBCN contents of 10% and 20% in weight were prepared. During the sintering, at temperatures <1660°C, the density of all the samples showed a minor increase because of solid state particles rearrangement. Above 1660°C, the density increased rapidly because of the grain boundary sliding with a non-Newtonian viscous boundary phase. After grain boundary sliding, grain-boundary diffusion enhanced by B and C elements from the SiBCN material was responsible for the further densification. The microstructure of the samples hot pressed at 1660°C appeared particle packing state. The two samples can achieve almost full density when they were hot pressed at 1830°C/40MPa for 90min.