Controllable Synthesis of High-purity β-SiAlON Powder

The Gibbs free values of different SiAlON were assessed by the thermodynamic quasi-paraboloid rule in Si3N4-AlN-SiO2-Al2O3 system and the thermodynamic parameter for beta-SiAlON were explored at 1800K. The synthesis of beta-SiAlON based oil coal gangue and carbon black by carbonthermal reduction nitridation method, and phase transformation of beta-SiAlON powder ill various atmospheres (such as air or nitrogen of different Purity) were discussed in detail. Thermodynamic analysis reveals that different SiAlON can be synthesized ill Suitable atmosphere parameter Y(Y = Ig (P-O2/P-theta) - 2/3Ig (P-N2/P-theta)) at 1800K, and low Y value is beneficial to synthesis of beta-SiAlON. When excessive carbon exists in the atmosphere, with the increase of purity (alpha) of initial nitrogen, the Y Value decreases, and the relationship between purity(alpha) and Y value Is Y = 2lg[ (2 - 2 alpha)/(2 - alpha)] - 2/3lg[alpha/(2 - alpha)] - 15.616. The experiment results shows that the suitable initial parameters based on thermodynamic analysis is highly advantageous in controllable synthesis of high-purity beta-SiAlON, the proper initial parameters is that samples, burying in coke, are sintered at 1800K in a flowing nitrogen atmosphere, the purity range of nitrogen is about 0.995-0.999.