Controlling the width of particle size distribution of Si powder and properties of sintered reaction-bonded silicon nitride (SRBSN) ceramics with high thermal conductivity

Sintered reaction-bonded silicon nitride (SRBSN) for high-thermal-conductivity ceramic substrates was fabricated from waste Si scrap. To prepare homogenously sized Si powder, the width of the particle size distribution (WPSD) was selected for the first time as the main index to characterize the milled Si powder and was systematically controlled. The coarse and irregular shape of the as-received Si scrap was carefully pulverized by controlling planetary milling parameter and then processed. As the WPSD of Si powder was narrower, the thermal conductivity of SRBSN ceramics increased from 67 to 81 W/mK with enhancing grain growth under the same sintering condition. Furthermore, to fabricate SRBSN ceramics with higher thermal conductivity, the effects of the milling fluid and the amount of sintering additive were investigated. It was proven that a smaller amount of a sintering additive was effective for enhancing the thermal and mechanical properties of SRBSN. Selection of the fluid for milling Si powders was an important inflection point for the surface properties of Si powder, which greatly influence the nitridation and thermal conductivity of the SRBSN ceramics.