Synthesis of Bauxite Based β-SiAlON by Compound Reduction Nitridation

The process of synthesizing bauxite based β-SiAlON by using carbon silicon composite reducing agent was studied. Specimens prepared by mixing bauxite (Al2O3 68%), carbon black and silicon are nitrided at 1100~1550°C for 6h. The mass change ratio of the specimens are determined; Phase composition and microstructure of some specimens are examined by XRD, SEM and EDS. The results are compared with those of specimens using Si and C separately as reducing agent. It is found that at 1100~1200°C only Si reacts with N2 and SiO2 to form Si2N2O; At 1300~1400°C, C takes part in reduction-nitridation with subsequent formation of SiAlON; At 1450~1550°C, there is noticeable increase in β-SiAlON formation, the optimum temperature is 1500°C. The amount of β-SiAlON formed is higher and crystale growth is better than that of single reducing agent.