2019-Sustainable Industrial Processing Summit
SIPS2019 Volume 3: Kobe Intl. Symp. / Science of Innovative and Sustainable Alloys and Magnets (SISAM)
| Editors: | F. Kongoli, M. Calin, J.M. Dubois, K. Zuzek-Rozman |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2019 |
| Pages: | 156 pages |
| ISBN: | 978-1-989820-02-5 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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Effective Eectrochemical and Physical Reprocessing of Nd-Fe-B and Sm-Co Permanent Magnets, Approaching the Zero Waste Economy
Kristina Zuzek-Rozman1; Xuan Xu1; Awais Ikram1; Farhan Mehmood1; Richard Sheridan2; Allan Walton2; Muhammad Awais2; Anas Eldosoukey3; Spomenka Kobe4; Saso Sturm5;1JOZEF STEFAN INSTITUTE, Ljubljana, Slovenia; 2UNIVERSITY OF BIRMINGHAM, Birmingham, United Kingdom; 3MAGNETI LJUBLJANA, D.D., Ljubljana, Slovenia; 4JOSEF STEFAN INSTITUTE, Ljubljana, Slovenia; 5HEAD OF DEPARTMENT FOR NANOSTRUCTURED MATERIALS, Ljubljana, Slovenia;
Type of Paper: Regular
Id Paper: 189
Topic: 42
Abstract:
Currently, less than 1% of the rare-earth elements (REEs) that reach the end of their useful lives are recycled. This is a very small percentage, especially if we consider that the recycling of end-of-life (EoL) (Dy, Nd)-Fe-B magnets is an important strategy for reducing the environmental dangers associated with rare-earth mining, and overcoming the well-documented supply risks associated with the REEs. We report on possibilities of direct electrochemical recycling and electrochemical reprocessing of Nd-Fe(B)-based magnets. Previous attempts to deposit alloys of rare earths from solutions at mild temperatures have met little success. Excitingly, in this investigation, we were able to electrodeposit Nd-Fe from the 1-ethyl-3-methylimidizolium dicyanamide ([EMIM][DCA]) ionic liquid. We observed that Nd(III) cannot be reduced independently, although it can be co-deposited inductively as substrate with the addition of Fe(II), proven by electron-energy-loss spectroscopy. Further, we propose a new concept of recycling the sintered (Dy, Nd)-Fe-B magnets by directly recovering the (Dy, Nd)2Fe14B matrix phase. Via an electrochemical etching method, we are able to recover pure individual(Dy, Nd)2Fe14B grains that can be re-used for new types of magnet production. In terms of energy consumption, the proposed electrochemical recycling route is comparable to the established direct re-use methods. These direct methods are considered as the most economical and ecological ways for recycling the sintered (Dy, Nd)-Fe-B magnets. In the frame of physical reprocessing, we have successfully synthesised new magnets out of hydrogen-recycled stocks with contemporary sintering technique of pulsed electric current sintering. The SmCo5 magnets for recycling were first decrepitated by hydrogen gas to produce the powder. The sample sintered at 900°C showed the best internal coercivity (jHc) of higher than 1500 kA/m with high remanence (Br) value of 0.47 T. The optimal SPS conditions yielded fully dense Nd-Fe-B magnets with the coercivity Hc = 1060 kA/m, which was boosted to 1160 kA/m after the post-SPS thermal treatment. The Br and Hc were tackled further, and increased applied pressures of 100-150 MPa resulted in Br = 1.01 T. Via the addition of DyF3, 17.5% higher coercivity than the optimally SPS-ed magnet was obtained due to Dy substituting the Nd in the matrix Nd2Fe14B phase. We showed that with a fine tune of the SPS and post annealing, together with variations in Br and Hc, it is possible to revitalize the recycled Nd-Fe-B and Sm-Co magnets.