Study On The Preparation And Mechanism Of Cerium Nickel,Neodymium Nickel,magnesium Nickel And Bismuth Dysprosium Alloys By Molten Salt Electrolysis

Molten salt electrolysis plays an extremely important role in the preparation of active metals and their alloys.While alloy electrolysis has obvious advantages,such as the controllable alloy phase composition,uniform elements distribution,the depolarization and alloying greatly reduce the electrolysis temperature,which make them develop rapidly in recent years.In the LiCl-KCl molten salt system,several electrochemical methods such as cyclic voltammetry(CV),square wave voltammetry(SWV),anodic stripping voltammetry(ASV)and open-circuit chronopotentiometry(OCP)were used to study the electrochemical behavior of RE(?)(Ce?Y?Nd)and Mg(?)on Ni electrode was studied and the electrocrystallization mechanism of Ce on Ni electrode was discussed;The precipitation potential of Ce(?),Nd(?)and Mg(?)on Ni cathode was determined according to several electrochemical methods.The Ce-Ni,Nd-Ni and Mg-Ni alloys with single phase composition were obtained and the controllable preparation of the intermetallic compounds with single phase composition was successfully realized;The electrochemical behaviors of Dy(?)on the Bi film electrode,and the relevant thermodynamic parameters of Bi-Dy alloy were calculated.The concentration of Ce(?)and Nd(?)ions in the process of preparing Ce-Ni and Nd-Ni alloys were detected online by electrochemical technology.The detailed researches are as follows:The electrochemical behavior of Ce(?),Y(?),Nd(?)and Mg(?)on W electrode in LiCl-KCl molten salt system were studied.The results showed that the reduction of Ce(?)and Y(?)at the W electrode was a quasi-reversible process controlled by diffusion with three electrons transferred in one step;In the case of high concentration,the Nd(?)reduction process is a process of 3 electron transfer(Nd(?)?Nd),and in the case of low concentration,that was two step processes of Nd(?)?Nd(?)and Nd(?)?Nd;the reduction of Mg(?)at the W electrode was a quasi-reversible process controlled by diffusion with two electrons transferred in one step;CV,CP,OCP and SWV methods were used to determine the diffusion coefficient(D)and the thermodynamic parameters of the reduction of Ce(?),Nd(?)and Mg(?).In LiCl-KCl molten salt system,Ce(?)and Nd(?)depolarized on the Ni electrode,and according to square wave voltammetry,the depolarization values were 0.72 V and 1.2 V,respectively.On the Ni electrode,the equilibrium potential of Nd-Ni and Ce-Ni alloys were obtained according to OCP curve.The single phase composition of CeNi,CeNi5 and Ce2Ni7 alloys were prepared by electrolysis at-2.0 V,-1.4 V and-1.6 V,respectively;NdNi2,Nd2Ni7 and Nd2Ni7 alloys with single phase were prepared by electrolysis at-1.7 V,-1.5 V and-1.3 V,respectively;It was also found that the prolonged electrolysis time plays an important role on the preparation of single-phase alloy.For example,Ce(?)was deposited on the Ni cathode,the composite of CeNi2 and CeNi3 alloys were obtained by-1.8 V electrolysis for 18 h,and CeNi2 pure phase alloy was obtained by electrolysis for 36 h;NdNi2 and NdNi alloys were obtained by electrolysis at-1.8 V for 8 h,and NdNi pure phase alloy was obtained by electrolysis for 18 h.It was found that in the OCP curve,both the equilibrium potential of Ce-Ni and Nd-Ni intermetallic compounds could be detected,and the potential pairs of these intermetallic compounds were plotted,corresponding to the composition-temperature phase diagram,the thermostatic phase diagram was drawn,and got the regularity formula.In LiCl-KCl molten salt system,the reduction process of Mg(II)on the Ni electrode was studied by electrochemical methods,such as CV,SWV and CP.It was found that the precipitation potential shifs towards to more positive owing to alloying and depolarization,the depolarization values were 0.28 V.The thermodynamic parameters,such as the standard Gibbs free energy of the Mg-Ni intermetallic compound,were calculated by OCP.Potentiostatic electrolysis was carried out by controlling applied potential,the single phase composition of Mg2Ni alloy was prepared by electrolysis at-2.0 V.In addition,in this paper,Dy-Bi alloy was prepared by using Bi as liquid cathode electrolysis and the experimental results showed that the liquid cathode had an obvious depolarization effect The depolarization values were 0.67 V.In this paper,the concentration changes of Ce(?)and Nd(?)in the electrolytic deposition process were monitored online by electrochemical technique.This work can provide an effective and reliable experimental basis for some studies on electrolytic refining and purification.