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Phase Evolution During Extraction and Recovery of Pure Nd from Magnet

Rasheed Mohammad Zarar, Nam Sun-Woo, Lee Sang-Hoon, Park Sang-Min, Cho Ju-Young, Kim Taek-Soo

Archives of Metallurgy and Materials

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2021

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Vol. 66, iss. 4

1001--1005

EN

Liquid Metal Extraction process using molten Mg was carried out to obtain Nd-Mg alloys from Nd based permanent magnets at 900°C for 24 h. with a magnet to magnesium mass ratio of 1:10. Nd was successfully extracted from magnet into Mg resulting in ~4 wt.% Nd-Mg alloy. Nd was recovered from the obtained Nd-Mg alloys based on the difference in their vapor pressures using vacuum distillation. Vacuum distillation experiments were carried out at 800°C under vacuum of 2.67 Pa at various times for the recovery of high purity Nd. Nd having a purity of more than 99% was recovered at distillation time of 120 min and above. The phase transformations of the Nd-Mg alloy during the process, from Mg12Nd to α-Nd, were confirmed as per the phase diagram at different distillation times. Pure Nd was recovered as a result of two step recycling process; Liquid Metal Extraction followed by Vacuum Distillation.

2

Effect of Mg Ratio on the Extraction of Dy from (Nd,Dy)-Fe-B Permanent Magnet Using Liquid Mg

Park Sang-Min, Nam Sun-Woo, Cho Ju-Young, Lee Sang-Hoon, Hyun Seung-Keun, Kim Taek-Soo

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1281--1285

EN

Recently, since the demand of rare earth permanent magnet for high temperature applications such as an electric motor has increased, dysprosium (Dy), a heavy rare earth element, is becoming important due to severe bias in its production. To fulfillthe increasing need of Dy, recycling offers as a promising alternative. In recycling of rare earths, Hydro-metallurgical extraction method is mainly used however it has adverse environmental effects. Liquid metal extraction on the other hand, is an eco-friendly and simple method as far as the reduction of rare earth metal oxide is concerned. Therefore, liquid metal extraction was studied in this research as an alternative to the hydro-metallurgical recycling method. Magnesium (Mg) is selected as solvent metal because it doesn’t form intermetallic compounds with Fe, B and has a low melting and low boiling point. Extraction behavior of Dy in (Nd,Dy)-Fe-B magnet is observed and effect of Mg ratio on extraction of Dy is confirmed.

3

Effect of Magnet Scrap Size on the Extraction Behavior of Heavy Rare Earth Elements by Liquid Metal Extraction

Nam Sun-Woo, Rasheed Mohammad Zarar, Park Sang-Min, Lee Sang-Hoon, Kim Do-Hyang, Kim Taek-Soo

Archives of Metallurgy and Materials

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2020

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Vol. 65, iss. 4

1273--1276

EN

Liquid metal extraction (LME) process results in 100% neodymium (Nd) extraction but the highest extraction efficiency reportedfor Dysprosium (Dy) so far is 74%. Oxidation of Dy is the major limiting factor for incomplete Dy extraction. In order to enhance the extraction efficiency and to further investigate the limiting factors for incomplete extraction, experiments were carried out on six different particle sizes of under 200 μm, 200-300 μm, 300-700 μm, 700-1000 μm, 1000-2000 μm and over 2000 μm at 900°C with magnesium-to-magnet scrap ratio of 15:1 for 6, 24 and 48 hours, respectively. This research identified Dy2 Fe17 in addition toDy2 O3 phase to be responsible for incomplete extraction. The relationship between Dy2 Fe17 and Dy2O3 phase was investigated, and the overall extraction efficiency of Dy was enhanced to 97%.