Physicochemical Properties Of NaCl - KCl - Na <2> 4 Molten Salt System And Study On The Electrochemical Mechanism Of Preparation Of Tungsten Powder

On the basis of the Na Cl-KCl-Na2WO4 system Electrolytic Preparation of Tungsten powder research, by using Archimedes method, rotation method, pull tube method and AC electrode method, it studied the system in a certain range of density, viscosity, surface tension and electrical conductivity;by using cyclic voltammetry, square wave voltammetry,chronopotentiometry, and chronoamperometry method, it studied the electrode process and electrochemistry mechanism of the Na Cl-KCl-Na2WO4 system under a certain temperature and different Na2WO4 content.The above findings indicate that:While the temperature is between 1173 K~1233 K, the system’s density rises at first,then fall, as the Na2WO4 content increasing; Na Cl-KCl system’s density shows a similar law as the temperature rises; the density of molten salt system made by Na2WO4(5 wt%~10 wt%)and mixed electrolyte falls as temperature rises; the density of Na Cl-KCl-Na2WO4(15 wt%)molten salt system showed an opposite law as temperature rises, it’s a linear relationship.When the temperature is 1173 K, the system’s viscosity falls as the Na2WO4 content increasing, and firstly rises then falls when the temperature rises between 1188 K and 1233 K.While the Na Cl-KCl system’s viscosity stays the same as the temperature rises; the viscosity of molten salt system made by Na2WO4(5 wt% ~10 wt%) and mixed electrolyte rises at first then falls as the temperature rises; the viscosity of Na Cl-KCl-Na2WO4(15 wt%)molten salt system rises as temperature rises.Surface tension of molten salt system mixed by Na2WO4( 0 wt%~10 wt%) and mixed electrolyte decreases as the temperature increases, it is a linear relationship.Surface tension of Na Cl-KCl-Na2WO4(15 wt%) molten salt system decays rapidly and then stays the same as the temperature increase, it is greatly influenced by temperature.Na Cl-KCl molten salt conductivity decreases with increasing temperature, it is a linear relationship. Na Cl-KCl-Na2WO4(5 wt%~15 wt%) molten salt system increases conductivity increases with increasing temperature, it is a linear relationship.Cyclic voltammetry analysis demonstrated W6+ions for the two-step reduction process,namely: W6++2e â†' W4+, W4++4e â†' W,W6+ between W4+ isreversible redox reactions. WO42-restore process is diffusion controlled. Na2WO4 concentration is too low to affect theelectrochemical performance of WO42-, with the increase of the concentration of Na2WO4 or temperature effects, can weaken thepolarization effect, conducive to the occurrence of WO42-in molten salt oxidation reduction reaction.Square wave voltammetry and the results obtained by cyclic voltammetry same.Chronoamperometry, potential method will also be given W6+ions is reduced to a two-step reaction, cathodic reduction process is diffusion controlled steps. Meanwhile,chronoamperometry indicate to W does not exist in the precipitation process of nucleation polarization, a three-dimensional instantaneous nucleation process; Chronopotentiometric With increasing current density, the cathodic reduction reaction reversibility decreases.