氯化物熔盐体系共电沉积法制备Mg-Li-Gd合金的研究

STUDY ON ELECTROCHEMICAL CODEPOSITION OF Mg-Li-Gd ALLOYS FROM CHLORIDE MELTS

在LiCl-KCl-MgCl_2-Gd_2O_3熔盐体系中采用电化学共沉积法制备Mg-Li-Gd合金,借助循环伏安和计时电位技术对熔盐电化学行为进行探讨,并运用XRD,SEM,EDS和OM对所得合金进行测试.研究结果表明,Gd_2O_3在LiCl-KCl熔盐体系中几乎不溶,而在LiCl-KCl-MgCl_2熔盐中有一定的溶解度,而且随着温度的升高,Gd_2O_3的溶解度也随之增大.循环伏安和计时电位研究表明,添加MgCl_2和Gd_2O_3后,Li的沉积电位向正向移动,当阴极电位小于-2.30 V或阴极电流密度大于0.776 A/cm^2时,可以实现Li,Mg和Gd共同析出.通过对电解条件的考察可知,电解温度对电流效率影响很大,当电解温度为873 K时,电流效率最大为78.87%.阴极电流密度高,则制备的Mg-Li-Gd合金中Li的含量较高.合金微观组织分析表明,在Mg-Li-Gd合金中存在Mg_3Gd相.Gd对Mg-Li合金有细化作用,而且随着Gd含量的增多,合金的晶粒细化越明显.由Gd元素的面扫描可知,Gd主要分布在晶界处.

cMg Li-Gd alloys were obtained by electrochemical codeposition method in LiC1-KC1- MgC12-Gd203 molten salt on molybdenum electrode at 1073 K. Transient electrochemical techniques, such as cyclic voltammetry and chronopotentiometry, were used in order to study the reaction mechanism. XRD, SEM, EDS and OM were employed to characterize Mg Li-Gd alloys. The results suggested that Gd203 could dissolve in LiC1 KC1-MgC12 molten salt while it could not in LiC1-KC1 melt. Cyclic voltammograms and chronopotentiometry measurements indicated that the potential of Li metal deposition, after the addition of MgC12 and Gd203, was more positive than the one of Li metal depositionbefore the addition. The codeposition of Mg, Li and Gd occurred when applied potentials were more negative than -2.30 V （vs. Ag/AgC1） or current densities were higher than 0.776 A/cm2 in LiC1- KCI-MgC12-Gd203. Electrolysis temperature exerted a great influence on current efficiency, 78.87% current efficiency was obtained when electrolysis temperature was 873 K. Li content in Mg Li-Gd alloys increased with the high current densities. XRD results showed that Mg3Gd intermetallic compounds formed in Mg Li-Gd alloys. Grain size became smaller as the Gd metal content increased in the alloy. The analysis of SEM and EDS demonstrated that the element of Gd was mainly distributed at grain boundaries.