The investigation of silicothermic reduction of CaO·MgO was carried out using a self-developed thermogravimetric analysis(TGA)instrument under vacuum and high temperature conditions.The TG data of pellets prepare...The investigation of silicothermic reduction of CaO·MgO was carried out using a self-developed thermogravimetric analysis(TGA)instrument under vacuum and high temperature conditions.The TG data of pellets prepared with calcined dolomite,ferrosilicon and fluorite were determined at the heating rates of 1.5,2.0,2.5 and 3.0℃/min in 5 Pa vacuum at 300−1400℃,respectively.Model-free analysis and model-based analysis were applied for simulating the kinetic mechanism.By analyzing the characteristics of the initial and final reaction temperatures of TG curve,ratio of half-width of derivative TG curve and kinetic parameters,a conclusion was made that the most probable mechanism function is the first order formal chemical reaction with activation energy of 233.42 kJ/mol and pre-exponential factor of 5.14×1010 s−1.This study provides the basic data of dynamics of silicothermic magnesium production under vacuum conditions.展开更多
X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy were used to analyze the complexes in LiCl−KCl eutectic salt containing VCl_(3) and KF.The additional fluoride ions would replace chloride ions and combine w...X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy were used to analyze the complexes in LiCl−KCl eutectic salt containing VCl_(3) and KF.The additional fluoride ions would replace chloride ions and combine with V(Ⅲ)to form VF_(6)^(3-).The electrochemical behavior of V(Ⅲ)was evaluated under condition of the molar concentration ratio of F−to Vn+(α)equal to 0:1,1:1,2:1,5:1,20:1 and 50:1,respectively.The results showed that a new reduction step appeared:VF_(6)^(3-)→V^(2+),and the reduction mechanism of vanadium ions became more complicated.The metallic vanadium was deposited on the tungsten electrode at−2.90 V in the LiCl−KCl melts for 6 h,and the products were characterized by SEM−EDS.It was indicated that the particle size of the product decreased with adding fluoride ions for the forming of the coordination compound VF_(6)^(3-).展开更多
基金Project(2016YFB0301100)supported by the National Key R&D Program of ChinaProject(51804277)supported by the National Natural Science Foundation of ChinaProject(2018ZE007)supported by the Rare and Precious Metal Materials Genome Engineering Project of Yunnan Province,China。
文摘The investigation of silicothermic reduction of CaO·MgO was carried out using a self-developed thermogravimetric analysis(TGA)instrument under vacuum and high temperature conditions.The TG data of pellets prepared with calcined dolomite,ferrosilicon and fluorite were determined at the heating rates of 1.5,2.0,2.5 and 3.0℃/min in 5 Pa vacuum at 300−1400℃,respectively.Model-free analysis and model-based analysis were applied for simulating the kinetic mechanism.By analyzing the characteristics of the initial and final reaction temperatures of TG curve,ratio of half-width of derivative TG curve and kinetic parameters,a conclusion was made that the most probable mechanism function is the first order formal chemical reaction with activation energy of 233.42 kJ/mol and pre-exponential factor of 5.14×1010 s−1.This study provides the basic data of dynamics of silicothermic magnesium production under vacuum conditions.
基金supports from the National Key Research and Development Program of China (No.2021YFC2901600)supported by the State Key Laboratory of Special Rare Metal Materials (No.SKL2020K004)。
文摘X-ray photoelectron spectroscopy(XPS)and Raman spectroscopy were used to analyze the complexes in LiCl−KCl eutectic salt containing VCl_(3) and KF.The additional fluoride ions would replace chloride ions and combine with V(Ⅲ)to form VF_(6)^(3-).The electrochemical behavior of V(Ⅲ)was evaluated under condition of the molar concentration ratio of F−to Vn+(α)equal to 0:1,1:1,2:1,5:1,20:1 and 50:1,respectively.The results showed that a new reduction step appeared:VF_(6)^(3-)→V^(2+),and the reduction mechanism of vanadium ions became more complicated.The metallic vanadium was deposited on the tungsten electrode at−2.90 V in the LiCl−KCl melts for 6 h,and the products were characterized by SEM−EDS.It was indicated that the particle size of the product decreased with adding fluoride ions for the forming of the coordination compound VF_(6)^(3-).
