Dissolution And Electrochemical Reduction Of Multivalent Refractory Metal Oxide In NaKClF Molten Salt

Refractory metal has special properties,widely used in metallurgy,aviation,aerospace and other fields.At present,there are many methods of preparing refractory metal but some problems exist.By studying the dissolution behavior and the electrodeposition characteristics of refractory metal oxides in NaCl-KCl-NaF system,a new way to extract the refractory metal is created.The dissolution behavior of V₂O₅ in molten NaKClF system was studied by isothermal saturation method.The results show that saturated dissolving time of V₂O₅ is required at least 7 hours at 650?.At 680?,it ‘s required at least 60 min to reach dissolved equilibrium again.The solubility of V₂O₅ increases with the increase of temperature and Na F content in the molten salt system.Based on the analysis of the possible reaction of the system by using Fact Sage7.0 thermodynamic software,the results of XRD analysis for the quench sample of molten salt were combined.The results show that the dissolution mechanism of V₂O₅ in NaCl-KCl-NaF is chemical dissolution,and the reaction process is 4V₂O₅+6NaF=6NaVO₃ +2VF₃+O₂.Combined with other refractory metal oxides dissolving in this molten salt,it is found that multivalent difficult molten metal oxides mainly dissolve in chemistry and single difficult molten metal oxides mainly dissolve in physics.The electrochemical reaction mechanism and crystallization process of V in NaCl-KCl-NaFV₂O₅ system were studied by the method of cyclic voltammetry,chronopotentiometry and chronoamperometry.The results show that the reduction reaction of VO₃^-is a reversible reaction of 5electrons in one step,and the electrical crystallization process of V is the instantaneous nucleation process of the three-dimensional growth of the hemisphere.The carbon steel was used as cathode and the graphite as anode.V in the NaCl-KCl-NaF-V₂O₅ system was successfully deposited.Optimum conditions: XNaCl=0.45,XKCl=0.45,XNaF=0.1,deposition temperature 710?,current density 150 m A/cm2,deposition time 120 minutes.Current waveform is bidirectional pulse.Under the condition of electrodeposition,V has a low diffusion velocity in carbon steel.To increase temperature and current density is beneficial to improvig diffusion velocity of V in carbon steel.