在Si_3N_4-SiO_2-Al_2O_3-AlN体系中, 采用拟抛物面规则对不同组成SiAlON相的热力学性能进行了评估, 并研究了β-SiAlON相的合成热力学条件. 以煤矸石为主要原料, 加入适量碳黑作为还原剂,在不同气氛(空气或不同纯度的氮气)下合成了β-SiAlON, 并研究了β-SiAlON粉料在不同气氛下的相转化. 热力学分析表明,不同的SiAlON相可以在合适的气氛参数Y=lg(P_(O_2)/P~θ)-2/3lg(P_(N_2)/P~θ)下合成, 较低的Y值有利于β-SiAlON相的合成. 过量碳存在时提高通氮纯度α将会降低气氛中的Y值, 其关系式为Y=2lg[(2-2α)/(2-α)]-2/3lg[α/(2-α)]-15.616. 实验结果表明:热力学分析得到的合适初始参数可以实现高纯β-SiAlON的可控合成, 当初始参数为T=1800K, 埋焦炭保护, 通入氮气纯度α＝0.995～0.999时可获得较好的结果.
The Gibbs free values of different SiAlON were assessed by the thermodynamic quasi-paraboloid rule in Si_3N_4-AlN-SiO_2-Al_2O_3 system and the thermodynamic parameter for β-SiAlON were explored at 1800K. The synthesis of β-SiAlON based on coal gangue and carbon black by carbonthermal reduction nitridation method, and phase transformation of β-SiAlON powder in various atmospheres (such as air or nitrogen of different purity) were discussed in detail. Thermodynamic analysis reveals that different SiAlON can be synthesized in suitable atmosphere parameter Y(Y=lg(P_(O_2)/P~θ)-2/3lg(P_(N_2)/P~θ)) at 1800K, and low Y value is beneficial to synthesis of β-SiAlON. When excessive carbon exists in the atmosphere, with the increase of purity (α) of initial nitrogen, the Y value decreases, and the relationship between purity(α) and Y value is Y=2lg[(2-2α)/(2-α)]-2/3lg[α/(2-α)]-15.616. The experiment results shows that the suitable initial parameters based on thermodynamic analysis is highly advantageous in controllable synthesis of high-purity β-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.
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