硅粉直接氮化反应热力学分析及动力学机理研究

用TG-DSC热重同步热实验分析的方法，研究不同升温速率下，硅粉氮化机理及化学反应动力学.发现温度在1 000~1 300 ℃时:差示扫描量热曲线各出现一个吸热、一个放热峰，说明氮化机理已发生改变.在1 000~1 100 ℃温度范围内，氮化硅转化率显著增加，即温度是影响其转化率的主要因素.实验表明:氮化反应的限制性环节由反应开始阶段的界面化学反应控制和之后的界面化学反应与内扩散混合控制组成；通过动力学计算得到表观活化能E=404.5 kJ/mol，频率因子A=9.57×1015 m/s，反应级数n=0.95，最终得到反应的速率方程的数学表达式. 

Thermodynamic analysis and kinetics mechanism for direct nitridation reaction

The mechanism and chemical kinetics of nitridation reaction at different heating rates was investigated by thermogravimetry. It is found that there is an exothermic peak and an endothermic peak in the differential scanning calorimetry curve at 1 000~1 300 ℃ centigrade, which indicates that the mechanism has changed. The conversion rate of silicon nitride is significantly increased within 1 000 to 1 100 ℃, and it indicates temperature is the dominant factor affecting the conversion rate. Experiments results show that the restrictive step of nitridation reaction is composed of chemical reaction in early stage of reaction and the mixed-control of chemical reaction and intraparticle diffusion in the subsequent reaction; the apparent activation energy is kinetically calculated to be 404.5 kJ/mol, the frequency factor A=9.57 ×1015 min/s, the reaction order n=0.95, and mathematical expression of reaction rate equation is finally obtained.