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PreprintCC BYChemRxiv

Sustainable recycling of end-of-life Nd-Fe-B permanent magnets through hydrogen based plasma reduction

  • Rafael Gitti Tortoretto Fim
  • Melissa Röhrig Martins da Silva1,2,3,4
  • Oliver Diehl1,2,5
  • Patricia Jovičević-Klug6,7
  • Jürgen Gassmann5
  • Dierk Raabe1,2
  • Matic Jovičević-Klug1,2
7 affiliations
  1. 1Circular Metallurgy and Alloy Design
  2. 2Max-Planck Institute for Sustainable Materials (MPI-SusMat)
  3. 3Department of Materials Science and Technology
  4. 4Nuclear and Energy Research Institute (IPEN)
  5. 5Fraunhofer Research Institution for Materials Recycling and Resource Strategies - Fraunhofer IWKS
  6. 6Department of Interface Chemistry and Surface Engineering
  7. 7Max-Planck-Institute for Sustainable Materials
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Abstract

Nd–Fe–B permanent magnets are essential for multiple energy, mobility, safety, and decarbonization-related technologies, yet rising demand, environmental impacts, and limited sustainable recycling options increase their material criticality. Herein, we propose Hydrogen Plasma Smelting Reduction (HPSR) as a novel composition-independent recycling strategy, applied for the first time to end-of-life (EoL) Nd–Fe–B magnets, enabling the universal treatment of mixed-quality magnetic scrap. The maximum oxygen content reduction of 66% is realized within tHPSR = 2.5 min of processing, reaching ~810 ppm while preserving the overall alloy stoichiometry, including critical rare-earth elements (REEs = Nd, Pr, and Dy). HPSRrecycled powders present higher remanent polarization (Jr = 0.54 – 0.66 T), intrinsic coercivity (Hcj = 1.02 – 1.45 T), maximum energy product (BH)max = 53.5 – 72.4 kJ m-3) and improved thermal stability, surpassing the magnetic properties of the starting scrap material without the addition of primary elements (Jr = 0.56; Hcj = 0.93 T, (BH)max = 46.5 kJ m-3). Under intentional contamination from the coating material (Ni), the reduction in the overall extrinsic magnetic properties is observed, as expected. These findings establish a foundation for the first fully sustainable and composition-independent so-called intermediate recycling loop for mixedquality REE-based magnet waste.

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Cite

BibTeXRIS
BibTeX
@misc{fim2026sustainable,
  title = {{Sustainable recycling of end-of-life Nd-Fe-B permanent magnets through hydrogen based plasma reduction}},
  author = {Rafael Gitti Tortoretto Fim and Melissa Röhrig Martins da Silva and Oliver Diehl and Patricia Jovičević-Klug and Jürgen Gassmann and Dierk Raabe and Matic Jovičević-Klug},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15008192/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008192/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Sustainable recycling of end-of-life Nd-Fe-B permanent magnets through hydrogen based plasma reduction
AU  - Rafael Gitti Tortoretto Fim
AU  - Melissa Röhrig Martins da Silva
AU  - Oliver Diehl
AU  - Patricia Jovičević-Klug
AU  - Jürgen Gassmann
AU  - Dierk Raabe
AU  - Matic Jovičević-Klug
PY  - 2026
DA  - 2026/09/02
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15008192/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008192/v1
AB  - Nd–Fe–B permanent magnets are essential for multiple energy, mobility, safety, and decarbonization-related technologies, yet rising demand, environmental impacts, and limited sustainable recycling options increase their material criticality. Herein, we propose Hydrogen Plasma Smelting Reduction (HPSR) as a novel composition-independent recycling strategy, applied for the first time to end-of-life (EoL) Nd–Fe–B magnets, enabling the universal treatment of mixed-quality magnetic scrap. The maximum oxygen content reduction of 66% is realized within tHPSR = 2.5 min of processing, reaching ~810 ppm while preserving the overall alloy stoichiometry, including critical rare-earth elements (REEs = Nd, Pr, and Dy). HPSRrecycled powders present higher remanent polarization (Jr = 0.54 – 0.66 T), intrinsic coercivity (Hcj = 1.02 – 1.45 T), maximum energy product (BH)max = 53.5 – 72.4 kJ m-3) and improved thermal stability, surpassing the magnetic properties of the starting scrap material without the addition of primary elements (Jr = 0.56; Hcj = 0.93 T, (BH)max = 46.5 kJ m-3). Under intentional contamination from the coating material (Ni), the reduction in the overall extrinsic magnetic properties is observed, as expected. These findings establish a foundation for the first fully sustainable and composition-independent so-called intermediate recycling loop for mixedquality REE-based magnet waste.
ER  -