H_(2)气基还原V_(2)O_(3)制备VO

Preparation of VO via H_(2)-based V_(2)O_(3)reduction

VO由于其独特的物理化学性质,是一种极具潜力的锂离子电池材料。本文研究了在H_(2)条件下通过还原V_(2)O_(3)制备VO的工艺。首先通过热力学计算确定还原条件;然后在1623 K、1648 K和1673 K下进行等温还原试验和动力学分析。热力学计算结果表明,V_(2)O_(3)的还原主要受温度和p(H_(2))/p(H_(2)O)影响,反应温度随p(H_(2))/p(H_(2)O)升高而降低。V_(2)O_(3)还原过程符合未反应收缩核模型,反应过程可分为2个步骤:第一步由化学反应控制,反应动力学方程为G(α)=[-ln(1-α)]^(1/3),表观活化能为107.3 kJ·mol^(-1);第二步由气体扩散控制,反应动力学方程为G(α)=[1-(1-α)^(1/3)]^(1/2),表观活化能为45.5 kJ·mol^(-1);还原过程未发现其他中间化合物。显微分析表明,所制备的VO粉末结晶良好,表面致密。

VO is one of the most promising energy materials due to its specific physical and chemical properties.Herein,preparation VO via the reduction of V_(2)O_(3)in an H_(2) atmosphere was presented.The thermodynamic calculation was first performed to ensure the reduction conditions and isothermal reduction experiments were then carried out at 1623 K,1648 K,and 1673 K under a H_(2) gas flow.Thermodynamic calculations results indicated that the reduction of V_(2)O_(3)is mainly affected by temperature and p(H_(2))/p(H_(2)O),and the reaction temperature can be typically decreased with increasing p(H_(2))/p(H_(2)O).The results show that the V_(2)O_(3)reduction process conforms to the unreacted shrinkage core model,and the reaction process can be divided into two steps.The first step is controlled by a chemical reaction,the kinetic equation of the reaction is G(α)=[-ln(1-α)]^(1/3),and the apparent activation energy is 107.3 kJ·mol^(-1).The second stage is controlled by gas diffusion.The kinetic equation of the reaction is G(α)=[1-(1-α)^(1/3)]^(1/2),and the apparent activation energy is 45.5 kJ·mol^(-1).No other intermediate compounds were found in this study.The microanalysis indicated that the as-prepared VO powder is well-crystallized and the surface is compact.