熔盐电解La-Mg-Ni合金及其电化学机理研究

Electrochemical Preparation of La-Mg-Ni Alloys in Molten Fluorides

采用循环伏安法、方波伏安法研究La、Mg在LaF3-LiF体系中的电化学行为,并以Ni作为活性阴极在980℃下采用恒电流法电解法制备了Ni-Mg-La合金.结果表明,在LaF3-LiF-La2O3熔盐体系中,La3+在W固态阴极上通过转移3个电子一步还原为金属La.同样,LaF3-LiF-MgO熔盐体系中Mg2+通过一步还原为金属Mg.LaF3-LiFLa2O3-MgO熔盐体系中,在阴极W上出现了多对氧化还原峰,表明有La-Mg金属间化合物的形成.当以Ni作为活性阴极时,在-0.4V至-1V扫描范围的循环伏安曲线表明至少有3种Ni-Mg-La合金共电沉积.通过对Ni-Mg-La合金微观组织进行分析可知,合金主要由La2Ni3基体相组成,在基体相中存在Mg含量较高的条状LaMgNi相.

In this paper,La-Mg-Ni alloys were prepared by constant current electrolysis method below 980℃with Ni as the active cathode in LaF3-Li F system.The electrochemical behavior of La and Mg in LaF3-Li F was also investigated by cyclic voltammetry(CV)and square wave voltammetry(SWV).The results showed that La3+was reduced to La and Mg2+was reduced to Mg at the W working electode in LaF3-Li F molten salt system.When Ni was used as an active cathode,the CV curve in the scanning range from-0.4 V to-1 V revealed at least three kinds of La-Mg-Ni alloys formed by co-electrodepositions.Analysis of the microstructure of La-Mg-Ni alloy showed that it was mainly composed of La2Ni3 phase with some amount of strip-shaped La MgNi phase with high Mg content.