高纯β-SiAlON粉料的可控合成

Controllable Synthesis of High-purity β-SiAlON Powder

在Si3N4-SiO2-Al2O3-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(PO2/Pθ)-2/3lg(PN2/Pθ)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 Si3N4-AlN-SiO2-Al2O3 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（PO2/Pθ）-2/3lg（PN2/Pθ）） 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.