# Fileset

[REPM2025_O1-5_Opelt.pdf](https://mdr.nims.go.jp/filesets/9e21d841-6c22-448c-9127-11618213b6df/download)

## Creator

Konrad Opelt, Mario Schönfeldt, Chi-Chia Lin, Jürgen Gassmann, Imants Dirba, Abdullatif Durgun, Matic Jovičević-Klug, Oliver Gutfleisch

## Rights

[Creative Commons BY Attribution 4.0 International](https://creativecommons.org/licenses/by/4.0/)

## Other metadata

[Enabling the production of large HRE lean magnets with homogeneous microstructure - the particle size effect in the 2-powder method and core-shell development in large magnets](https://mdr.nims.go.jp/datasets/604bc717-9c0c-4921-8953-2091653de387)

## Fulltext

PowerPoint-PräsentationEnabling the production of large HRE lean magnets with homogeneous microstructure –The particle size effect in the 2-powder method and core-shell development in large magnetsFraunhofer Research Institution for Materials Recycling and Resource Strategies28th of July 2025 | REPM 2025 Tsukuba, Japan | Konrad OpeltLogobereich▪ © 2025. This work is openly licensed via CC BY 4.0.https://creativecommons.org/licenses/by/4.0/Content 1 September 2025Slide 1 © Fraunhofer IWKS▪ Introduction▪ The particle size effect ▪ Manufacturing of large magnets via the 2-powder method▪ Life-Cycle-Assessment▪ Summary & OutlookIntroduction1 September 2025© Fraunhofer IWKSSlide 2Fraunhofer-Gesellschaft worldwide© Fraunhofer IWKSSlide 31 September 2025Fraunhofer Representative Office, Tokyo Fraunhofer Innovation Platform for Fibers, Processing and Recycling Solutions at Innovative Composite Center, KanazawaIntroductionCriticality of NdFeB magnets© Fraunhofer IWKS▪ The NdFeB market is driven by rising demand for electromobility and wind power▪ Demand for NdFeB in the EU will increase from 10 kt to 55 kt between 2020 and 2050▪ Import volume 2023: approx. 700 million € (9,000 t) of NdFeB magnets, Germany second largest importer worldwide after Japan▪ High need to reduce dependency especially of HREs on third countries▪ Elemental cost (metal)▪ Neodymium: $ 75.95 per kg ▪ Praseodymium: $ 82.89 per kg▪ Dysprosium: $ 298.70 per kg▪ Terbium: 1229.60 $ per kg R. Gauß, et al, Rare Earth Magnets and Motors: A European Call for Action. A report by the Rare Earth Magnets and Motors Cluster of the European Raw Materials Alliance, Berlin, 2021.CEPS, Developing a supply chain for recycled rare earth permanent magnets in the EU, 2022.www.mineralprices.comSlide 41 September 2025Demand for NdFeB magnets in the EU for selected applications in kt per yearhttp://www.mineralprices.com/Pilot plant for magnet production and recycling @ IWKS© Fraunhofer IWKSSlide 5Synthesis and analyticsResearch focusDevelopment of technologies for the magnet production and recycling in the batch size of 10 – 50 kg and technology transfer to industrial size manufacturing→ Sintered magnets | rapid-quenching | additive manufacturing1 September 2025Introduction© Fraunhofer IWKSSlide 62-powder methodProcess for grain boundary modification▪ Blending of two different RE2Fe14B powders ▪ Heavy rare earth free main phase powder (MP) with ideally at least 50 % - 100 % higher average particle size ▪ Mixed with a HRE (such as Dy) containing anisotropy powder (AP) ▪ During the sintering process the smaller AP particles turn earlier into the liquid phase and surround the MP particles▪ Formation a core-shell structure▪ Advantage compared to GBDP▪ No additional HRE source▪ No additional coating step▪ No additional cost and time-intensive heat treatment▪ No limitation of magnet sizeK. Opelt et al., Acta Mat. 270 (2024) 119871WO 2016/180912 AI, November 2016.WO 2025/082920 October 2023.K. Opelt et al., Acta Mat. 270 (2024) 1198711 September 2025The particle size effect1 September 2025© Fraunhofer IWKSSlide 7© Fraunhofer IWKSSlide 8The particle size effect1 September 2025Manuscript under preparation▪ Two HRE free MP and four HRE containing AP▪ All APs include 10 wt.% Dy▪ Blending of MP and AP with a ratio of 80/20▪ All powder mixtures include 2 wt.% Dy ▪ Coercivity gain between        350 kA/m and 450 kA/m➢ 100 kA/m difference is related to the particle size effect, meaning that smaller grain sizes lead to higher coercivityΔ Hc ~450 kA/mΔ Hc ~350 kA/m▪ Development of a core-shell structure for all magnets▪ Even for similar particle sizes of MP and AP© Fraunhofer IWKSSlide 9The particle size effectSEM investigations1 September 2025Manuscript under preparationMP (3.7 µm)MP (5.4 µm) AP 2.5 µm3.1 µm3.6 µm4.0 µm© Fraunhofer IWKSSlide 10The particle size effectCore-shell development1 September 2025Manuscript under preparationgrain size~9 µmgrain size~11 µm▪ The average grain size after sintering for the mixtures with MP (5.4 µm) is larger compared to the MP (3.7 µm)▪ The same trend is observed for the core thickness of the core-shell structure▪ However, the shell thicknesses are in the similar range for all sintered magnets, independent of the initial powders▪ The thickness of the shells (~ 2 µm) is assumed to be only related to the presence of the APs ➢ The mechanism for the core-shell development is assumed to be the precipitation of the Dy atoms during the sintering procedurecore coreshellshellManufacturing of large magnets via the 2-powder method1 September 2025© Fraunhofer IWKSSlide 11© Fraunhofer IWKSSlide 12Manufacturing of large magnets via the 2-powder methodMagnetic properties▪ 350g magnet with dimensions of approx. 45 mm in height and 40 mm in diameter▪ Cut out smaller samples with 5 mm in height and 12 mm in diameter➢ Homogeneous magnetic properties throughout the whole big magnet1 September 2025Manuscript under preparation© Fraunhofer IWKSSlide 13Manufacturing of large magnets via the 2-powder methodSEM investigation➢ SEM shows the formation of a homogeneous core-shell structure in the whole volume of the 350g magnet1 September 2025Manuscript under preparation© Fraunhofer IWKSSlide 14Manufacturing of large magnets via the 2-powder methodAtom probe tomography1 September 2025Manuscript under preparationElement at. %Nd 10.93Dy 0.94Pr 0.55B 5.0550 nm▪ Nd, Dy, Pr, Cu, increase at GB▪ Fe, B  decrease at GB© Fraunhofer IWKSSlide 15Manufacturing of large magnets via the 2-powder methodAtom probe tomography1 September 2025Manuscript under preparationB Nd CuElement at. %Nd 12.16Dy 0.1Pr 0.13B 4.6450 nm▪ Higher Nd content and lower Dy content in the core siteLife-Cycle-Assessment1 September 2025© Fraunhofer IWKSSlide 16© Fraunhofer IWKS1 September 2025Slide 17Life-Cycle-AssessmentManuscript under preparationhttps://www.horiba.com/esp/applications/energy-and-environment/energy-usage-optimization/lca/© Fraunhofer IWKS1 September 2025Slide 18Life-Cycle-AssessmentManuscript under preparation▪ Industrial production shows about 10 times less climate change potential compared to our technical scale processes▪ Therefore the values shown here has to be compared relatively▪ Roughly 8 percent higher CO2-eq./kg more consumption for the additional GBDP steps (only valid for thin magnets)➢ LCA demonstrates the energy-saving potential of the 2-powder methodSummary & Outlook1 September 2025© Fraunhofer IWKSSlide 19© Fraunhofer IWKS1 September 2025Slide 20▪ The investigation of different particle sizes for MP and AP shows a coercivity gain up to 450 kA/m with 2 wt.% Dy, whereby the shell thickness is the same for all magnets ➢ Core-shell development is assumed to be the precipitation of the HREs from the AP▪ 350g huge magnets with a homogeneous core-shell structure through                                                                         the whole volume were produced, which is not possible with the GBDP▪ This shows a large potential also for the utilization of the rare earth balance➢ Increasing the Ce content by engineering a high Ce-containing grain and                                                         performing the magnetic hardening with a Nd rich shell ▪ LCA shows the CO2-eq. saving potential of the 2PM compared with the GBDP▪ Next step is to adjust the HRE content in the AP to further improve the coercivity gain by using the 2PMSummary & OutlookC.-C Lin et al., Adv. Eng. Mater. 2025, 2500054Contact—Konrad Opelt, M.Sc.Magnetic MaterialsTel. +49 6023 32039-853Konrad.opelt@iwks.fraunhofer.deFraunhofer IWKSAschaffenburger Str. 12163457 Hanau, Germanywww.iwks.fraunhofer.deLogobereichThank you very much for your attention—Konrad Opelt, M.Sc.Magnetic MaterialsTel. +49 6023 32039-853konrad.opelt@iwks.fraunhofer.deFollow us for more information:This work was funded by the German Ministry of Educationand Research in the framework of the project „Scale2PM“(Skalierung der 2-Pulvermethode zur Herstellung vonPermanentmagneten mit reduziertem Gehalt kritischerElemente) [grant number 03VP10552]mailto:Konrad.opelt@iwks.fraunhofer.demailto:Konrad.opelt@iwks.fraunhofer.dehttps://www.linkedin.com/company/fraunhofer-iwks/https://www.linkedin.com/company/fraunhofer-iwks/