The effect of silicon carbide powder particle size on the densification of ceramic sintering

After sintering with a mixture of coarse and fine powders, the bonding of SiC ceramic particles is smaller and tighter compared to single powder sintering. Due to the moderate difference in particle size between the coarse and fine powders used, the fine particles can better fill the pores between the coarse particles. Therefore, after sintering, the grain size is more consistent, and the distribution of carbon and pores is more uniform, without obvious aggregation or abnormal grain growth.

The coarse-grained silicon carbide used has a larger particle size, and the filling of fine particles is not sufficient. Therefore, it can be observed that after sintering, there is insufficient grain bonding, uneven size distribution, and uneven distribution of pores. When using a single small silicon carbide powder for sintering, the finer particles of the silicon carbide powder exhibit interwoven grain growth, tighter bonding, and more uniform pore distribution after sintering, while the coarser particles exhibit uneven grain growth, uneven pore distribution, and an increasing trend after sintering.

The bending strength and density of the samples sintered using a mixture of coarse and fine silicon carbide powders are higher than those sintered using a single powder, which is consistent with the microstructure. The density and flexural strength of the sintered SiC ceramic samples reached 3.13 g/cm3 and 410 Mpa, slightly higher than the samples sintered with a single powder. Although there is still a significant gap in its mechanical properties compared to samples sintered with a single powder, this can still provide an idea for low-cost atmospheric pressure sintering of SiC ceramics. Experiments have shown that if the particle distribution of coarse and fine silicon carbide powders is optimized in a reasonable proportion, it is highly possible to use partially mixed powders to replace all fine particle powders to achieve atmospheric pressure densification sintering of SiC ceramics.