Preparation of α-Si3N4 and SiC powders by carbothermic reduction of SiO2

α-Si 3 N 4 and SiC powders were prepared from reaction between SiO 2 and carbon black in different atmosphere. The effects of atmospheres, raw material particle sizes, and C/SiO 2 molar ratio on the syntheses of Si 3 N 4 and SiC powders were investigated. The optimal parameters for preparing α-Si 3 N 4 were determined to be a temperature of 1500 °C for 8 h with a C/SiO 2 molar ratio of 4.0. In addition, the results demonstrated that H 2 atmosphere facilitated SiC synthesis by lowering its formation temperature. SiC powders were synthesized under a flowing H 2 atmosphere at 1500 °C for 5 h. N 2 -H 2 mixed atmosphere inhibited Si 3 N 4 formation while promoting SiC synthesis, with increasing SiC content as the H 2 partial pressure rose. Meanwhile, the size reduction of raw materials was conducive to promoting the formation of Si 3 N 4 and SiC and reducing the granularity of the final product. However, if the particle size of the raw materials was too fine, the product will tend to agglomerate.