Effects of a carbothermal reduction reaction on the microstructure of nano-silicon nitride ceramics

In this study, using amorphous nano-Si3N4 as the starting powder, the oxides on the Si3N4 powder surface were removed by carbothermal reduction to prevent the formation of the O′-sialon phase in the sintered product. The results indicate that carbothermal reduction can be effectively induced at 1250°C and produce single-phase Si3N4. However, as the temperature increased, the liquid phase that formed during Si3N4 sintering began to impede the carbothermal reduction. Analysis revealed that when the temperature exceeded 1350°C, the reaction gradually shifted from that of carbothermal reduction to that of decomposition, and residual carbon and O′-sialon phase were observed in the sintered product.