The electrochemical reaction of Bi(Ⅲ)and co-reduction behaviour of Bi(Ⅲ)and Y(Ⅲ)ions were researched in molten LiCl-KCl on a ttmgsten(W)electrode employing a range of electrochemical teclmiques.Cyclic voltammetric and square-wave voltanunetric results revealed that the reduction of Bi(Ⅲ)was a one-step process,with the exchange of three electrons on a W electrode,and diffusion-controlled.The electrochemical curves showed two reduction peaks pertaining to the formation of Bi-Y alloy compounds,because of the co-reduction of Bi(Ⅲ)and Y(Ⅲ) by metallic Y deposited on the pre-deposited Bi-coated W electrode and reacting with Bi metal in molten LiCl-KCl. Furthermore,galvanostatic electrolysis was conducted using liquid Bi as cathode to extract yttrium at different current intensities,and the extractive products were analyzed by SEM,EDS and XRD.The results indicated that BiY intermetallic compotmd was formed in the molten LiCl-KCl-YCl3 system.
LI MeiLIU YichuanSUN ZhongxuanHAN WeiZHANG MilinYANG XiaoguangSUN Yang
Rare earth(RE) metals and their alloys have attracted considerable practical interests due to their functional properties. Because of their negative deposition potentials, RE metals cannot be electrochemically deposited from aqueous media. Using molten salt as medium provides a unique opportunity for the electrowinning and electrore?ning of high-purity RE metals, as well as for the electrochemical formation of their alloys and intermetallic compounds. Certainly, the electrochemical behaviors of RE metals and their alloys have been investigated in a number of different molten salts comprising all-?uorides,all-chlorides and mixed chloride-?uoride media. Based on the results, RE and their alloys were produced by molten salt electrolysis. In this paper, the developments of preparation of RE metals and their alloys by electrolysis in molten salts in recent years were systematically summarized on both the local and international levels. Attention was paid mainly to the electrodeposition of RE metals and their alloys, including RE–Mg, RE–Al, RE–Ni, RE–Co,RE–Cu, RE–Fe and RE–Zn alloys.
The electrochemical behavior of Mg,Li,Al and Er were investigated by electrochemical techniques in LiClKCl-MgCl2-AlCl3-ErCl3 melts at 823 K.The cyclic voltammetry and chronopotentiometry indicated that the co-reduction of Mg,Li,Al and Er occurs at current densities more negative than-0.89 A.cm-2.Er(III) under-potential deposited on pre-reduced Al electrode formed Al-RE alloys.X-ray diffraction(XRD) results indicated that Mg17Al12,Al2Er,Al2Er3 and Al4Li9 phases were prepared by galvanostatic electrolysis.ICP analyses of samples showed that lithium and aluminum contents of Mg-Li-Al-Er alloys could be controlled by concentration of AlCl3 and cathodic current density.
Yi SUNMilin ZHANGWei HANMei LIYusheng YANGYongde YANMeng ZHANG
The reduction of Tm(Ⅲ) on a liquid Zn electrode was investigated in a Li Cl-KCl melt via cyclic voltammetry,square wave voltammetry, and open circuit chronopotentiometry. On a liquid Zn electrode, the reduction mechanism of Tm(Ⅲ) ions is through one step with the exchange of three electrons via the formation of a Zn-Tm alloy. This differs from that on an inert electrode, as the reduction is Tm(Ⅲ) ions were though two consecutive steps. Galvanostatic electrolysis was carried out at a liquid Zn electrode at different current densities in a LiClKCl-TmCl3 melt. The Tm2Zn17 intermetallic compound was identified in the deposit, except in the Zn phase,by X-ray Diffraction(XRD).
The chlorination of rare earth oxides by MgCl2 was investigated in the molten chlorides. To reduce the solvent salt volatility, the LiCl-NaCl mixture was selected as a solvent by comparing the mass loss of the Li ClNaCl with LiCl-KCl melts after the addition of MgCl2 in the temperature range of 873 K to 1073 K. The dissolution behavior of La2O3 was investigated in the LiCl-NaCl-MgCl2 melts by XRD measurements and ICP-AES analysis of the melts, which indicated that La2O3 was chlorinated by Mg Cl2 to produce La Cl3. The reduction peak of La(Ⅲ) in the LiCl-Na Cl-MgCl2-La2O3 melts was observed from cyclic voltammogram and square wave voltammogram. The Mg-La alloy obtained by galvanostatic electrolysis in the LiCl-NaCl-MgCl2-La2O3 melts was characterized by XRD and SEM-EDS, indicating that the Mg-La alloy consisted of Mg and La2Mg17 phases.
