NaCl-KCl-NdCl3-AlCl3熔盐体系电解制备Nd-Al合金及机理  

Preparation and Reaction Mechanism of Nd-Al Alloys by Electrolysis in Molten NaCl-KCl-NdCl-AlCl

作　　者：耿傲 何几文 刘欢 华中胜 张梦龙[1] 徐亮 Geng Ao;He Jiwen;Liu Huan;Hua Zhongsheng;Zhang Menglong;Xu Liang(School of Metallurgical Engineering,Anhui University of Technology,Ma’anshan 243032,China;Anhui Province Key Laboratory of Metallurgical Engineering&Resources Recycling,Anhui University of Technology,Ma’anshan 243002,China)

机构地区：[1]安徽工业大学冶金工程学院,安徽马鞍山243032 [2]安徽工业大学冶金工程与资源综合利用安徽省重点实验室,安徽马鞍山243002

出　　处：《稀有金属材料与工程》2020年第7期2462-2469,共8页Rare Metal Materials and Engineering

基　　金：国家自然科学基金(51204002,U1703130);高校优秀青年人才支持计划项目(gxyq2018012);冶金工程与资源综合利用安徽省重点实验室开放基金(SKF18-01,SKF19-05)。

摘　　要：在700℃的NaCl-KCl体系中,采用循环伏安法、方波伏安法和开路计时电位法等电化学测试方法研究了钨电极上Nd(Ⅲ)的电化学行为以及与Al(Ⅲ)共沉积的电化学过程。结果表明:在低扫描速率(0.1~0.5V·s^-1)下,NaCl-KCl-NdCl3熔盐中Nd(Ⅲ)的还原是一步交换3个电子的准可逆过程,该还原过程由扩散步骤控制,扩散系数约为1.2×10^-5 cm^2·s^-1。将AlCl3引入NaCl-KCl-NdCl3熔体后,循环伏安、方波伏安以及开路计时电位测试结果表明,电解过程中形成了3种Nd-Al金属间化合物(Nd3Al11、NdAl3和NdAl2),其形成机理为Nd在预先沉积的Al上发生欠电位沉积。通过电动势法,计算了700℃时Nd-Al金属间化合物的热力学参数,如两相共存下Nd的活度和相对偏摩尔吉布斯自由能以及Nd-Al金属间化合物的标准吉布斯自由能。在-2.3 V下进行恒电位电解5 h制备了Nd-Al合金,所得合金由Nd3Al11、NdAl3、NdAl2和Al4种物相组成。The electrochemical behaviors of Nd(Ⅲ)on tungsten electrode and its co-deposition with Al(Ⅲ)in NaCl-KCl salts at 700℃were investigated by a series of electrochemical techniques such as cyclic voltammetry,square wave voltammetry and open-circuit chronopotentiometry,and then Nd-Al alloy were prepared via direct co-deposition of Nd and Al on the inert electrode.The results show that the reduction of Nd(Ⅲ)in NaCl-KCl-NdCl3 melts is a one-step process with three electrons exchanging,and the reaction is an irreversible process controlled by diffusion at low scanning rates(0.1~0.5 V/s)with the calculated diffusion coefficient being approximately 1.2×10^-5cm^2·s^-1.After AlCl3 introduced into the NaCl-KCl-NdCl3 melts,the curves of cyclic voltammetry,square wave voltammetry and open-circuit chronopotentiometry indicate that three kinds of Nd-Al intermetallic compounds(Nd3 Al11,NdAl3 and NdAl2)are formed.It can be deduced that the underpotential deposition of Nd occurs on the tungsten electrode covered with the pre-deposited metal Al from the open circuit chronopotentiometry.Based on the results of open circuit chronopotentiometry,the thermodynamic properties of Nd-Al intermetallic compounds are determined by electromotive force measurement at 700℃,such as the activity of Nd in two-phase coexisting state and relative partial molar Gibbs energies,as well as the standard Gibbs energies of Nd-Al intermetallic compound.Finally,potentiostatic electrolysis was carried out at–2.3 V for 5 h to prepare Nd-Al alloys.X-ray diffraction(XRD)and scan electron micrograph(SEM)-energy dispersive spectrometry(EDS)analysis indicate that the obtained alloys are mainly composed of Nd3 Al11,NdAl3,NdAl2 and Al phases.

关 键 词：熔盐电解 Nd-Al合金 电化学行为 金属间化合物 欠电位沉积 

分 类 号：TF845[冶金工程—有色金属冶金]