2018-Sustainable Industrial Processing Summit
SIPS2018 Volume 5. Zehetbauer Intl. Symp. / SISAM
| Editors: | F. Kongoli, S. Kobe, M. Calin, J.-M. Dubois, T. Turna |
| Publisher: | Flogen Star OUTREACH |
| Publication Year: | 2018 |
| Pages: | 154 pages |
| ISBN: | 978-1-987820-90-4 |
| ISSN: | 2291-1227 (Metals and Materials Processing in a Clean Environment Series) |
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New Sustainable Processing of RE-based Magnetic Materials
Spomenka Kobe1;1JOSEF STEFAN INSTITUTE, Ljubljana, Slovenia;
Type of Paper: General Plenary
Id Paper: 408
Topic: 46
Abstract:
Rare-Earth Transition Metal permanent magnets (RETM-PM) are vital components in the rapidly-developing renewable energy sector, where the motors require strong magnets with the ability to operate at temperatures well over 100°C. To achieve high coercivity, remanence and consequently high energy product (the figure of merit for PM) at elevated temperatures, the addition of heavy rare earths (HREs) to the basic Nd-Fe-B composition is needed. However, HREs are on the very top of the list of Critical Raw Materials (CRM) published by the EC in 2017.
In the frame of the “Magnetic Materials Group” of IJS, Ljubljana, we have developed an innovative, and sustainable way to drastically decrease the amount of HREs needed for the highest-level performance of PM. In the second part of the talk, we will focus on the need for recycling of the end-of-use (EoU) RETM-PM.
To drastically reduce the use of HREs, we focused on developing a new method, which was designed to enable us to achieve the properties needed for high-temperature applications with the lowest amount of scarce elements. With our new inventive technique, further transferred to pilot production, we could minimize down to 0.2 at % the amount of HREs used whereas the improvement of coercivity was 30 % with minimal loss in remanence. The total saving of the HREs turned to be 16-times less for the same performance, which is a significant contribution to the world economy and clean, sustainable environment. In studying the mechanism for such an improvement in coercivity without significantly decreasing the remanence, a detailed microstructure investigation was performed by using high-resolution transmission electron microscopy.
Besides the use of these newly developed high energy magnets for electric and hybrid cars as well as wind turbine generators, another vital application is as the source of the magnetic field in the development of the new magnetic cooling devices.
Since Europe lacks any significant REE deposits that can be exploited to reduce its import dependency, it is essential to be ahead of another rare-earth crisis, like the one witnessed in 2009–2010. European industry needs approximately 2,000–3,000 tons/year of REEs, all of which have to be imported. Producers of REE-based permanent magnets use the vast majority of these REEs. At the same time, the current recycling rate for REEs contained in these magnets is a pitiful < 1%. Whatever the way we look at this, the recovery, reprocessing and reuse of REE permanent magnets represent the only viable route to ensuring a sustainable future for this critical European industry (nearly everything that uses electricity also uses magnets).
With a view at sustainability and circular economy, we will present our continuous efforts to develop and demonstrate innovative pilot plants at Technology Readiness Levels (TRLs) 6–7 for the clean and sustainable recycling of these most critical raw materials from secondary EoU PM sources in the EU.
We are investigating different ways to recycle and reprocess the EoU Nd-Fe-B PMs. As it is vital for the applications to keep or even surpass the properties of the original magnets, we are utilizing a contemporary technique of spark plasma sintering (SPS) that assures a minimized grain coarsening in the 500 nm range. So far, we have demonstrated an improvement in coercivity of the raw powder up to HC = 1120 kA/m with BHmax = 95 kJ/m3, that matches the one achieved in fresh HDDR+SPS-ed samples. From the perspective of chemical recycling of the EoU Nd-Fe-B magnets, we will report on a successful synthesis of Nd-Fe-based deposits using ionic liquids. The XRD, VSM, thermomagnetic, Mössbauer and HRTEM/EDXS/EELS studies are going to be discussed with regards to the properties of the obtained Nd-Fe-deposits.