Synthesis and reaction process of β-Si3N4 by means of carbothermal nitridation of serpentine

Abstract

Abstract The reaction process of carbothermal nitridation synthesis of β-Si3N4 from serpentine is investigated in this paper. Samples with different molar ratios of carbon black to serpentine were calcined under nitrogen atmosphere at 1300 °C, 1400 °C and 1500 °C for 3 hrs. The phase composition and microstructure of the synthesized powders were determined using X-ray diffraction and scanning electron microscopy. The reaction process was analyzed by means of differential thermal analysis. The results show that the main reaction was that forsterite from serpentine reacted with carbon black to form SiO, Mg vapor and CO, then SiO and N2 generated β-Si3N4. Fine β-Si3N4 powders were produced under nitrogen atmosphere at 1500 °C when the carbon black/serpentine molar ratio was 6.0. The synthesized β-Si3N4 powders had uniform grain size and high β-Si3N4 content.