Effect of the SiC powder microscopic morphology on properties of Si/SiC ceramics prepared by spark plasma sintering

Abstract

To solve the problem that Si was volatile and dense Si/SiC ceramics were difficult to achieve by spark plasma sintering (SPS) under a low sintering temperature and pressure, three kinds of SiC powders were used for particle grading and then ball‐milled with different time to further change and regulate their particle size and morphology, and finally nearly dense Si/SiC ceramics were prepared by SPS. The effect of milling time on particle size, morphology, tap density, phase, and microstructure of the SiC powders, as well as on bulk density, microhardness, thermal conductivity, phase, and microstructure of the Si/SiC ceramic, was researched. When the mixed SiC powders were ball‐milled for 12 min, the bulk density, microhardness, and thermal conductivity of Si/SiC ceramic were 2.96 g/cm3, 22.95 GPa, and 152.84 W/(m K), respectively. Ball milling changed the particle gradation and micro‐powder morphology and then affected the powder particle stacking state. Forming continuous pore channels was conducive for the volatile liquid Si to flowing and filling pores in a short time, resulting in denser Si/SiC ceramics at a lower sintering temperature and pressure. This study was useful for the preparation of ceramics containing volatile liquid phase by SPS.