Microstructure, phase compositions and mechanical properties of slip cast sintered SiC/Si3N4 composites

Abstract

In this study, a slurry containing a mixture of Si and SiC powders was used to fabricate the SiC/Si3N4 composites by slip casting method and sintering in a nitrogen-controlled furnace. The effects of mixing ratios of Si and SiC powders, different particle sizes of SiC powders as well as three sintering temperatures (1400, 1450, 1490 °C) were evaluated for SiC–Si3N4 composites. The results demonstrated that the best slurry was prepared using the weight ratio of Si/SiC of 30/70 and the fine-particle size of SiC powders with an average particle size of d50 ≤ 0.45 μm. The results of XRD and FESEM determined that the sintered composites at 1450 °C have the minimum porosity without the SiO2 phase. Besides, with an increase in the sintering temperature, the α/β-Si3N4 phase ratio increased while the hardness and flexural strength were strongly dependent on the α/β-Si3N4 phase ratio in the SiC–Si3N4 composites.