Multimodal particle size distribution by mixing nanopowders for full densification of spark plasma sintered SiC ceramics

Highly pure free of additives fully dense SiC ceramics (>99 % theoretical density) were manufactured by Spark Plasma Sintering. The mixing of two initial nanopowders, exhibiting different average particle sizes, was favorable for densification, thanks to wider particle size distribution and modification of the powder rheological behavior. Furthermore, this mixing step lessened the cohesive and electrostatic behaviors of the initial powders, making it possible to reach densities higher than 99 % of the theoretical density, without exaggerated grain growth. In addition to promoting the densification, the mixing step enabled easier handling, facilitating the die filling process, and enhanced their compaction ability. Finally, fully dense SiC ceramics were obtained at 2100 C-degrees without any dwell time. The produced ceramics exhibited an average Knoop hardness of 24 GPa (HK1), which is similar to the Hexoloy (R) SA reference. Notably, the Young's Modulus was slightly higher at 429 GPa versus the 404 GPa of the reference.