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Preparation and Reaction Mechanism of Nd-Al Alloys by Electrolysis in Molten NaCl-KCl-NdCl3-AlCl3
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School of Metallurgical Engineering,Anhui University of Technology,Ma’anshan

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    Abstract:

    : The electrochemical behaviors of Nd(III) on tungsten electrode and its co-deposition with Al(III) in NaCl-KCl salts at 700 °C were investigated by a series of electrochemical techniques such as cyclic voltammetry, square wave voltammetryand open-circuit chronopotentiometry, and thus Nd-Al alloy was prepared via direct co-deposition of Nd and Al on the inert electrode. The results show thatthe reduction of Nd(III) in NaCl-KCl-NdCl3 melts isa one-step process with three electrons exchanged, and the reaction is anirreversible processcontrolled by diffusionat low scan rate (0.1~0.5V/s) with the calculated diffusion coefficient is approximately 7.6×10-5cm2/s. After AlCl3introduced into the NaCl-KCl-NdCl3 melts, the curves of cyclic voltammetry, square wave voltammetryand open-circuit chronopotentiometry indicate that three kinds of Nd-Al intermetallic compounds (Nd11Al3, NdAl3 and NdAl2) were 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 chronopotentiometriy. Based on the results of open circuit chronopotentiometriy, the thermodynamic properties of Nd-Al intermetallic compounds were determined by electromotive force measurement at 700 °C, such as the activity of Nd in two-phase coexisting state and relative partial molar Gibbs energies, as well as the standard Gibbs energies ofNd-Al intermetallic compound. Finally, potentiostatic electrolysis was carried out at -2.3Vfor 5h to obtain a product alloys. X-ray diffraction (XRD) and scan electron micrograph (SEM)-energy dispersive spectrometry (EDS) analysis indicated that the obtained alloys were mainly composed of Nd11Al3, NdAl3, NdAl2 and Al phases.

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[Geng Ao, He Jiwen, Liu Huan, Hua Zhongsheng, ZHang Menglong, Xu Liang. Preparation and Reaction Mechanism of Nd-Al Alloys by Electrolysis in Molten NaCl-KCl-NdCl3-AlCl3[J]. Rare Metal Materials and Engineering,2020,49(7):2462~2469.]
DOI:10.12442/j. issn.1002-185X.20190522

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History
  • Received:June 19,2019
  • Revised:June 28,2019
  • Adopted:July 24,2019
  • Online: August 31,2020
  • Published: