Electrochemical Formation of Nd-Fe Alloys in Molten LiF-CaF₂-NdF₃

Abstract

In the present study, as a fundamental study for recycling Nd from Nd-Fe-B permanent magnet scrap, the electrochemical Nd-alloying behavior of Fe was investigated in a molten LiF-CaF2-NdF3 (0.3 or 0.5 mol%) system at 1123 K. Herein, the equilibrium potential of Nd3+/Nd was determined as 0.18 V (vs Li+/Li) by open-circuit potentiometry using a Mo electrode. Cyclic voltammetry and open-circuit potentiometry were conducted using an Fe electrode, and the results suggested the formation of multiple phases within the Nd-Fe alloys. Alloy samples were prepared via one- or two-step potentiostatic electrolysis of Fe electrodes at various potentials. The formation of liquid Nd-Fe alloy was confirmed through one-step potentiostatic electrolysis at 0.10 V. The solid Nd2Fe17 alloy was formed via a two-step potentiostatic electrolysis, wherein the potential was changed to 0.25 V after the initial electrolysis at 0.10 V, indicating that the Nd2Fe17 phase is thermodynamically stable at 0.25 V. The equilibrium potentials of the coexistence states of liq. Nd-Fe + Nd2Fe17 and Nd2Fe17 + Fe were determined as 0.19 and 0.31 V, respectively, which are in good agreement with the previously reported thermodynamic data.

Electrochemical Formation of Dy–Fe Alloys in Molten LiF–CaF2–DyF3

“…[28][29][30] In the above-mentioned studies, we used solid alloys of RE elements with Ni or Ni-based alloys, as candidate materials for the diaphragm; however, the diffusion of RE elements is expected to be much faster in liquid alloys than in solids. 31 Therefore, we focused on liquid Nd-Fe alloys as candidates for liquid alloy diaphragms and have already reported the results of our investigation of the electrochemical Nd alloying behavior of Fe electrodes in molten LiF-CaF 2 -NdF 3 at 1123 K. 32 In the previous study, we found that liquid Nd-Fe alloys were formed by potentiostatic electrolysis at 0.10 V vs Li + /Li. 32 In this study, the electrochemical formation of Dy-Fe alloys in molten LiF-CaF 2 -DyF 3 at 1123 K was investigated using cyclic voltammetry, open-circuit potentiometry, and potentiostatic electrolysis.…”

“…31 Therefore, we focused on liquid Nd-Fe alloys as candidates for liquid alloy diaphragms and have already reported the results of our investigation of the electrochemical Nd alloying behavior of Fe electrodes in molten LiF-CaF 2 -NdF 3 at 1123 K. 32 In the previous study, we found that liquid Nd-Fe alloys were formed by potentiostatic electrolysis at 0.10 V vs Li + /Li. 32 In this study, the electrochemical formation of Dy-Fe alloys in molten LiF-CaF 2 -DyF 3 at 1123 K was investigated using cyclic voltammetry, open-circuit potentiometry, and potentiostatic electrolysis. Saïla et al investigated the electrochemical behavior of Dy 3+ in LiF-CaF 2 -DyF 3 at 1113-1203 K with the purpose of partitioning and transmutation of long-lived fission products and minor actinides for nuclear waste management.…”

Electrochemistry of Neodymium in an Equimolar NaCl-KCl Melt without and with Addition of Fluoride Ions

“…26-30 indicated the reduction of Nd(III) to Nd in two z E-mail: s.kuznetsov@ksc.ru; kuznet@chemy.kolasc.net.ru consecutive steps. There are many studies on the recovery of neodymium with utilization of different cathodes made of Ni, 4,[31][32][33][34][35][36][37][38][39] Cd, 12 Cu, 23,34 Fe, 40 Bi, 41,42 Sn, 42 Al. 12,23,43 The main goal of this study is to determine the standard rate constants of charge transfer (k s ) for the Nd(III)/Nd(II) redox couple and formal standard redox potentials E * Nd(III)/Nd(II) in an equimolar NaCl-KCl mixture.…”