Electrochemical Formation of Dy-Ni Alloys in Molten LiF-CaF<sub>2</sub>-DyF<sub>3</sub>

Kobayashi, Seitaro; Nohira, Toshiyuki; Kobayashi, Katsutoshi; Yasuda, Kouji; Hagiwara, Rika; Oishi, Tadashi; Konishi, Hisatoshi

doi:10.1149/2.053212jes

Cited by 48 publications

(58 citation statements)

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“…In this study, a Mo electrode was occasionally used for comparison with the Ni electrode, because no alloys exist in the binary Mo-Pr, MoLi, Mo-Ca, Mo-Na, and Mo-K systems at the present experimental temperatures according to their phase diagrams. 18 Open-circuit potentiometry.-To determine the deposition potential of Pr metal, the measurement was conducted for a Mo electrode in molten LiF-CaF 2 -PrF 3 (0.50 mol%) at 1123 K. By using the same procedures as those employed in our previous studies on Nd and Dy in a LiF-CaF 2 melt, 8,9 the deposition potential of Pr was measured from the transient curve for the open-circuit potential after galvanostatic electrolysis at -3.0 A cm −2 for 10 s. The potential stays at 0.21 V for around 120 s, which corresponds to the Pr(III)/Pr potential.…”

Section: Resultsmentioning

confidence: 99%

“…[7][8][9][10][11][12]19 Thus, open-circuit potentiometry was carried out for the Ni plate electrode after galvanostatic electrolysis at -0.15 A cm −2 for 10 min in the same melt. The same measurements were successively repeated thrice to obtain more distinct potential plateaus.…”

Section: Resultsmentioning

confidence: 99%

“…4,[6][7][8][9][10][11] According to our previous studies, a specific RE element can be alloyed and de-alloyed rapidly with iron-group (IG) * Electrochemistry Society Active Member z E-mail: yasuda.kouji.3v@kyoto-u.ac.jp; nohira@energy.kyoto-u.ac.jp metals in molten salts by using electrochemical methods. 12 In the proposed process, Nd, Dy, and Pr are separated because of differences in both the formation potentials and formation rates of the RE-IG alloys used as the diaphragm.…”

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Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts

Yasuda

Kondo

Hagiwara

2014

J. Electrochem. Soc.

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For the establishment of a process for the electrochemical recovery of rare earth elements from used magnet scraps, the electrochemical formation of Pr-Ni alloys in molten LiF-CaF 2 -PrF 3 and NaCl-KCl-PrCl 3 salts at 1123 K and 973 K, respectively, was investigated.Cyclic voltammetry and open-circuit potentiometry indicated the formation of several phases of Pr-Ni alloys. Alloy samples were prepared by one-or two-step potentiostatic electrolysis using a Ni plate electrode at various potentials. Scanning electron microscopy observations and X-ray diffraction measurements confirmed the formation of PrNi 2 , PrNi 3 , Pr 2 Ni 7 , and PrNi 5 . The formation potential for each Pr-Ni alloy phase was determined from experimental results. In addition, the optimum electrolysis conditions for the separation of Nd, Dy, and Pr are discussed.Rare earth (RE) metals have several superior characters such as electric, magnetic, and fluorescence properties and are therefore indispensable as industrial materials throughout the world. Among the many applications of RE metals, the use of neodymium-ironboron (Nd-Fe-B) magnets-the so-called neodymium permanent magnets-has been remarkably increasing recently. Neodymium permanent magnets composed of a Nd 2 Fe 14 B main phase have several advantages such as superior magnetic properties and high mechanical strength, and are used for voice coil motors in hard disk drives (HDDs), magnetic resonance imaging (MRI), speakers/vibrators in cell phones, and motors in electric vehicles (EVs) and hybrid electric vehicles (HEVs). Since praseodymium (Pr) and Nd have similar chemical properties, they are found in nature in the same ores and their separation is difficult. Thus, in some applications including permanent magnets, a Nd-Pr alloy called didymium (Di) is sometimes utilized. On the other hand, Nd-Fe-B magnets have the drawback of a relatively low Curie temperature of ∼583 K. In order to maintain its superior coercive force even at high temperatures (above 473 K), where high-performance motors in EVs and HEVs operate, dysprosium (Dy) is necessary as an additive.One of the concerns pertaining to RE magnets is the uneven distribution of RE resources: in 2011, China had 50% of the proven RE reserves and produced over 97% of the global RE supply. 1 In 2010-2012, the price of REs increased sharply, causing supply problems for the magnets. While the present RE production capacity satisfies the demand and their price has lowered, there remains the potential for RE shortage in the future.On the basis of these supply circumstances, it can be concluded that the recycling or waste management of Nd-Fe-B magnet scraps is currently an urgent task. The conventional wet processes for RE recycling from Nd-Fe-B magnet scraps have several disadvantages such as their multistep and complicated processes, high environmental loads, and large energy consumption. As new recycling methods, pyrometallurgical processes such as chemical vapor transport, 2 selective reduction, 3 molten salt electrolysis, 4 and ionic liquid e...

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

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Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts

Yasuda

Kondo

Hagiwara

2014

J. Electrochem. Soc.

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“…The separation and production of RE metal using electrolysis was first studied by Kobayashi et al [52,80,81] using molten fluoride (LiF-CaF 2 -NdF 3 ) and an iron group (RE-IG) alloy diaphragm. Waste containing RE was used as the anode, and REs were anodically dissolved by molten salt electrolysis as shown in Fig.…”

Section: Electrolysis Using Molten Salt and Ionic Liquidsmentioning

confidence: 99%

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

Firdaus

Rhamdhani

Durandet

et al. 2016

J. Sustain. Metall.

105

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Rare-earth metals, particularly neodymium, dysprosium, and praseodymium are becoming increasingly important in the transition to a green economy due to their essential role in permanent magnet applications such as in electric motors and generators. With the increasingly limited rare-earth supply and complexity of processing Nd, Dy, and Pr from primary ores, recycling of rare-earth based magnets has become a necessary option to manage supply and demand. Depending on the form of the starting material (sludge or scrap), there are different routes that can be used to recover neodymium from secondary sources, ranging from hydrometallurgical (based on its primary production process), electrochemical to pyrometallurgical. Pyrometallurgical routes provide solution in cases where water is scarce and generation of waste is to be limited. This paper presents a systematic review of previous studies on the high-temperature (pyrometallurgical) recovery of rare earths from magnets. The features and conditions at which the recycling processes had been studied are mapped and evaluated technically. The review also highlights the reaction mechanisms, behaviors of the rare-earth elements, and the formation of intermediate compounds in high-temperature recycling processes. Recommendations for further scientific research to enable the development of recovery of the rare-earth and magnet recycling are also presented.

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“…(a) 0.50 V： DyCu 2 + Dy(III) + 3e -⇌ 2DyCu [1] (b) 0.68 V： 2 3 DyCu 5 + Dy(III) + 3e -⇌ 5 3 DyCu 2 [2] (c) 0.88 V： 5Cu + Dy(III) + 3e -⇌ DyCu 5 [3] Separation of Dy and Nd…”

Section: Dy-cuunclassified

Electrochemical Formation of RE-Cu (RE=Dy, Nd) Alloys in a Molten LiCl-KCl System

et al. 2013

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The electrochemical formation of RE-Cu (RE=Dy, Nd) alloys were investigated in a molten LiCl-KCl-RECl 3 (0.50 mol% added) at 723 K. Open-circuit potentiometry was carried out with a Cu electrode after depositing Dy metal by potentiostatic electrolysis at 0.40 V (vs. Li + / Li) for 120 s in a molten LiCl-KCl-DyCl 3 (0.50 mol%) at 723 K. There were four potential plateaus at (a) 0.50 V, (b) 0.68 V, (c) 0.88 V and (d) 0.95 V. An alloy sample was prepared at 0.55 V for 4 h. From the XRD pattern of the sample, the alloy phase was identified as DyCu 2 . In the sample obtained at 0.78 V, the existence of DyCu 5 was seen. The phase of the sample obtained at 1.50 V was transformed to Cu. On the basis of these results, alloy samples were prepared by potentiostatic electrolysis at 0.45-0.75 V for 1 h using Cu plates in a molten LiCl-KClDyCl 3 -NdCl 3 . The mass ratios of Dy/Nd in the alloy samples were found to be 6-12 by ICP-AES.

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Electrochemical Formation of Dy-Ni Alloys in Molten LiF-CaF₂-DyF₃

Cited by 48 publications

References 10 publications

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

Electrochemical Formation of RE-Cu (RE=Dy, Nd) Alloys in a Molten LiCl-KCl System

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Electrochemical Formation of Dy-Ni Alloys in Molten LiF-CaF2-DyF3

Cited by 48 publications

References 10 publications

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF2–PrF3and NaCl–KCl–PrCl3Melts

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF2–PrF3and NaCl–KCl–PrCl3Melts

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

Electrochemical Formation of RE-Cu (RE=Dy, Nd) Alloys in a Molten LiCl-KCl System

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Electrochemical Formation of Dy-Ni Alloys in Molten LiF-CaF₂-DyF₃

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts

Electrochemical Formation of Pr–Ni Alloys in LiF–CaF₂–PrF₃and NaCl–KCl–PrCl₃Melts