Kinetic Mechanism in the Process of Carbothermal Reduction of Ferrum Niobate  

作　　者：李解 李保卫 YANG Yong HAN Jicheng ZHAO Wenyu ZHANG Bangwen 

机构地区：[1]Key Laboratory of Comprehensive Utilization of Bayan Obo Multi-Metal Resources, Inner Mongolia University of Science and Technology

出　　处：《Journal of Wuhan University of Technology(Materials Science)》2015年第5期918-922,共5页武汉理工大学学报（材料科学英文版）

基　　金：Funded by National Natural Science Foundation of China(No.50974073);Inner Mongolia Natural Science Foundation(No.2012MS0714);Significant Special Fund of Inner Mongolia Science & Technology Department;National Key Laboratory of Inner Mongolia University of Science and Technology Foundation(No.BO-13-001)

摘　　要：Ferrum niobate was synthesized by solid-phase sintering method in a vacuum carbon tube furnace at 1 300 ℃ for 180 min. The phase transformation of ferrum niobate carbothermal reduction process was studied by XRD. The reduction reactions of ferrum niobate in different temperature stages were determined by the TG-DSC curve. Meanwhile, according to the TG curve, the reaction kinetics parameters were calculated by A.W.Coats integration and the control steps in different temperature stages were ascertained. The results showed that the reduction of ferrum niobate starts at the temperature of 1 000 ℃, and the reduction process carries out in two steps according to sintering temperature.In a temperature range of 1 000-1 238 ℃(the first step), the main reduction products are Nb O2 and Fe; the kinetic equation of initial stage is [-ln(1-α)]4=kt, controlled by nucleation growth, and the apparent activation energy is 388 k J/mol; with the temperature increasing, the kinetic equation is α+(1-α)ln(1-α)=kt, which is the Valensi two-dimensional diffusion kinetic equation, and the apparent activation energy is 264.4 k J/mol. The main reaction in a range of 1 238-1 344 ℃(the second step) is the reduction of Nb O2 to Nb C, the kinetic equation is [(1-α)-1/3-1]2=kt, which is controlled by the three-dimensional diffusion, and the apparent activation energy is 482.7 k J/mol.Ferrum niobate was synthesized by solid-phase sintering method in a vacuum carbon tube furnace at 1 300 ℃ for 180 min. The phase transformation of ferrum niobate carbothermal reduction process was studied by XRD. The reduction reactions of ferrum niobate in different temperature stages were determined by the TG-DSC curve. Meanwhile, according to the TG curve, the reaction kinetics parameters were calculated by A.W.Coats integration and the control steps in different temperature stages were ascertained. The results showed that the reduction of ferrum niobate starts at the temperature of 1 000 ℃, and the reduction process carries out in two steps according to sintering temperature.In a temperature range of 1 000-1 238 ℃(the first step), the main reduction products are Nb O2 and Fe; the kinetic equation of initial stage is [-ln(1-α)]4=kt, controlled by nucleation growth, and the apparent activation energy is 388 k J/mol; with the temperature increasing, the kinetic equation is α+(1-α)ln(1-α)=kt, which is the Valensi two-dimensional diffusion kinetic equation, and the apparent activation energy is 264.4 k J/mol. The main reaction in a range of 1 238-1 344 ℃(the second step) is the reduction of Nb O2 to Nb C, the kinetic equation is [(1-α)-1/3-1]2=kt, which is controlled by the three-dimensional diffusion, and the apparent activation energy is 482.7 k J/mol.

关 键 词：ferrum niobate carbothermal reduction KINETICS 

分 类 号：O643.12[理学—物理化学]