铝热法制备钒铝合金热力学及动力学研究

Study on Thermodynamic and Kinetics for Preparation of Vanadium-aluminum Alloy Based on Thermite Reaction

基于原子-分子理论建立了计算Al-V二元合金系结构单元质量作用浓度的热力学模型。利用文献报道的2 000、2 073、2 173、2 273 K下Al-V二元系的活度计算了生成Al8V5、Al4V反应的平衡常数,并进一步得到其摩尔标准吉布斯自由能的表达式。同时采用TG-DSC热重同步热试验分析的方法,研究了不同升温速率下,铝热法合成钒铝合金反应机理及化学反应动力学。结果发现温度在660~690℃时,差示扫描量热曲线各出现一个吸热、放热峰,说明反应机理已发生改变。然后分别运用Kissinger法、Kissinger-Crane法求解铝热反应动力学参数,建立动力学方程,通过动力学计算得到表观活化能E=448.96 k J/mol,频率因子A=1.98×10^(29)m/s,反应级数n=0.83。

A thermodynamic model for calculating the mass action concentration of structural units in A1-V binary melts system was established based on the atom-molecule theory. The standard equilibrium constants for generating AlsV5 and AI4V were calculated using the activities of A1-V binary system respectively at 2 000,2 073,2 173 and 2 273 K reported on the literatures and the expressions of standard mole Gibbs free energy for the reactions were further obtained. Meanwhile, the mechanism and chemical kinetics for prepara- tion of vanadium-aluminum alloy based on thermite reaction at different heating rates were investigated by TG-DSC. There was respectively an exothermic and endothermic peak on the differential scanning calorime- try curve （DSC curve） at 660 -690 ℃ indicating the variation of reaction mechanism. The kinetics parame- ters of the thermite reactions were separately calculated by Kissinger and Kissinger-Crane equations and the kinetics equation was established. The apparent activation energy （E） was calculated to be 448.96 kJ mol-1, the frequency factor A = 1.98 × 1029 m - s-m and the reaction order n = 0.83.