Article
Materials Science, Multidisciplinary
Srecko Stopic, Buse Polat, Hanwen Chung, Elif Emil-Kaya, Slavko Smiljanic, Sebahattin Gurmen, Bernd Friedrich
Summary: NdFeB magnets are widely used in various technological applications due to their remarkable magnetic properties. However, their limited recycling and China's monopoly on rare earth elements supply pose economic and environmental challenges. This paper proposes a pyrometallurgical recycling method for end-of-life NdFeB magnets by oxidizing them in air. The experimental results show that the material is completely oxidized at 1100 degrees C, resulting in the formation of various metal oxides.
Article
Materials Science, Multidisciplinary
Hanwen Chung, Laras Prasakti, Srecko R. Stopic, Dominic Feldhaus, Vesna S. Cvetkovic, Bernd Friedrich
Summary: This paper presents the results of a study on recycling NdFeB magnets to recover rare earth elements for remanufacturing similar magnets. The viability of extracting rare earth metals from magnet recycling-derived oxide (MRDO) through molten salt electrolysis is investigated. Experimental results show that the electrochemical reduction of the MRDO in NdF3 + LiF and NdF3 + PrF3 + LiF fused salts systems can effectively deposit metallic Nd and Pr on the working substrate. The suitability of the obtained alloy for remanufacturing NdFeB magnets is evaluated.
Review
Chemistry, Physical
Kuankuan Zhang, Ziwen Wang, Jian He, Xiaogang Li, Wenjie Gong, Yunhua Huang
Summary: The study showed that adding Dy and Nb increased the diffusion channels for hydrogen in the magnets, resulting in an increase in hydrogen concentration near the surface and surface roughness of the magnets. During electrochemical hydrogen charging, the magnetic properties of the magnets were affected, with coercivity, magnetic moment, and maximum energy density decreasing.
INTERNATIONAL JOURNAL OF HYDROGEN ENERGY
(2022)
Article
Metallurgy & Metallurgical Engineering
Zhe Wang, Chunjiang Li, Zhancheng Guo
Summary: In this study, the removal of oxide inclusions from waste NdFeB magnets by supergravity technology was investigated and optimized for maximum oxide removal. The supergravity technology was proven to be highly efficient in removing oxide from waste NdFeB magnets for recycling, and a design for an industrial reactor was proposed.
ISIJ INTERNATIONAL
(2023)
Article
Chemistry, Multidisciplinary
Minpeng Lei, Yong He, Wenhui Ma, Rilin Zhang, Yun Lei
Summary: A novel and effective approach for extracting Nd from Nd2O3-containing slag using low-purity Si as a reductant is proposed in this study. Three methods are used to recover Nd from the Nd-containing HCl solution, resulting in increased purity of silicon from 99.2% to 99.997%.
ACS SUSTAINABLE CHEMISTRY & ENGINEERING
(2021)
Review
Materials Science, Multidisciplinary
C. Burkhardt, S. van Nielen, M. Awais, F. Bartolozzi, J. Blomgren, P. Ortiz, M. B. Xicotencatl, M. Degri, S. Nayebossadri, A. Walton
Summary: Rare Earths (RE) permanent magnets are essential for Europe's green and digital transition. However, the dependence on imports for RE magnetic materials in the global supply chain is a vulnerability. To address this, the EU plans to have at least 15% of its annual consumption of permanent magnets covered by recycling capacities by 2030. Researchers have shown that hydrogen can be used as an efficient recycling method to extract NdFeB magnet powder from various end-of-life components.
JOURNAL OF MAGNETISM AND MAGNETIC MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Deddy C. Nababan, Reiza Mukhlis, Yvonne Durandet, Mark Pownceby, Leon Prentice, M. Akbar Rhamdhani
Summary: The study evaluated the high temperature oxidation kinetics of end-of-life NdFeB rare earth permanent magnets with Ni/Cu/Ni coating, showing a diffusion-controlled mechanism and an activation energy of 168 kJ/mol. The presence of the coating was found to reduce overall kinetic rates by ten times.
Article
Nanoscience & Nanotechnology
Yuan Cao, Min Zhu, Min Zhi Rong, Ming Qiu Zhang
Summary: The authors propose an approach based on Diels-Alder (DA) chemistry to apply the injection molding technique to rubber-bonded magnets. By functionalizing the oligomers of hydroxyl-terminated polybutadiene rubber and modifying the magnetic NdFeB particles, cross-linkages are established using the reversible DA reaction. The resulting composite exhibits low viscosity and good separation of fillers in the melt state, and retains the robustness of traditional thermosets. The polybutadiene-bonded magnets can be injection molded with high magnetic and mechanical properties, self-healability, and recyclability.
ADVANCED COMPOSITES AND HYBRID MATERIALS
(2023)
Article
Engineering, Chemical
Dominik Boehm, Konrad Czerski, Stephan Gottlieb, Armin Huke, Goetz Ruprecht
Summary: This article presents a sustainable separation concept for large-scale recycling of NdFeB magnets. It combines two separation concepts from the literature: selective pre-separation by in situ chlorination and evaporation, and subsequent distillation for high-purity recovery of recyclable material components, including Rare Earth Elements (REEs).
Review
Engineering, Chemical
Aarti Kumari, Sushanta Kumar Sahu
Summary: The paper emphasizes on the importance of critical raw materials (CRMs) for green energy technologies, particularly in the windmill and electric vehicle (EVs) sectors. The Neodymium-Iron-Boron (NdFeB) magnet is an essential component of these technologies, containing rare earth elements (neodymium, praseodymium, and dysprosium) that fall under critical category due to their limited availability and high demand. The paper reviews the supply risk associated with these materials and explores the potential of recycling rare earth metals from spent NdFeB magnets. Different recycling methods, including direct recycling and various extraction techniques, are critically examined. Future research is needed to develop an efficient and eco-friendly process for selective extraction and separation of critical rare earths from spent NdFeB magnets in order to avoid the supply risk of these materials.
SEPARATION AND PURIFICATION TECHNOLOGY
(2023)
Article
Geochemistry & Geophysics
Anna Klemettinen, Zbigniew Adamski, Ida Chojnacka, Anna Lesniewicz, Leszek Rycerz
Summary: The hydrometallurgical route for recycling NdFeB magnets involves leaching in acidic solutions, but selective recovery of rare earths from the solution is challenging due to high iron ion concentration. In this study, selective precipitation of rare earth oxalates using oxalic acid was proposed as a potential separation method. Experimental tests on model and real solutions showed that using stoichiometric amounts of oxalic acid achieved high rare earth precipitation efficiency, while increasing the amount of oxalic acid further improved separation. Additionally, oxidizing iron from Fe2+ to Fe3+ before precipitation of rare earth oxalates enhanced the separation process.
Review
Materials Science, Multidisciplinary
Jeotikanta Mohapatra, Pramanand Joshi, J. Ping Liu
Summary: When ferromagnetic materials reduce their size to the nanometer scale, their magnetic ordering and properties change due to size-sensitive physical phenomena. This review discusses the scientific and technological problems of low-dimensional ferromagnetic materials, including their synthesis strategies and the effects of geometric confinement on magnetic properties. These materials, including metals, alloys, and ceramics, find applications in green energy, information storage, and biomedicine. Research in this area is important for both technological applications and understanding magnetic anisotropy and interactions.
PROGRESS IN MATERIALS SCIENCE
(2023)
Article
Materials Science, Multidisciplinary
Emir Poskovic, Fausto Franchini, Marta Ceroni, Claudia Innocenti, Luca Ferraris, Claudio Sangregorio, Andrea Caneschi, Marco Actis Grande
Summary: Nowadays, the circular economy is gaining attention in sectors where raw material supply is critical. Recycling of rare earth elements, particularly NdFeB magnets, is important due to cost and environmental concerns. A new mechanical method for recycling without hydrogen, high temperature, or chemical processes has been proposed and compared with a traditional method. Analysis of the obtained NdFeB powders includes magnetic properties and chemical composition, specifically oxygen content.
Article
Engineering, Manufacturing
Tej Nath Lamichhane, Timothy R. Charlton, Brian Andrews, Devanshi Malaviya, Arjun K. Pathak, Haile Ambaye, Mathieu Doucet, Valeria Lauter, John Katsaras, Brian K. Post, Mariappan Parans Paranthaman
Summary: Halbach arrays, known for their efficiency in generating directed magnetic fields, were printed using additive manufacturing technology for polarized neutron reflectometry. The customized Halbach rings maintained a high level of polarization for neutron beams, which are essential in studying various phenomena in physics, chemistry, and biology. Additive manufacturing was demonstrated to be effective in producing prototype Halbach arrays and preserving magnetic field properties.
3D PRINTING AND ADDITIVE MANUFACTURING
(2022)
Article
Materials Science, Multidisciplinary
Tarini Prasad Mishra, Lennart Leich, Martin Krengel, Sebastian Weber, Arne Roettger, Martin Bram
Summary: Electric current-assisted sintering technologies show great promise for processing NdFeB magnets, allowing for easy sintering of powders with suboptimal particle size distribution and morphology. Flash spark plasma sintering, especially when combined with external pressure, can achieve pronounced anisotropic magnetic properties. These ECAS technologies also have potential for recycling waste magnet materials and are compared to established processing technologies.
ADVANCED ENGINEERING MATERIALS
(2022)
Article
Materials Science, Multidisciplinary
Heike C. Herper, Konstantin P. Skokov, Semih Ener, Patrik Thunstroem, Leopold V. B. Diop, Oliver Gutfleisch, Olle Eriksson
Summary: This study presents a comprehensive theoretical and experimental investigation of the magnetic properties of NdFe11Ti and RE-free YFe11Ti, aiming to elucidate the influence of the 4f electrons. The localized 4f electrons of Nd are found to be the driving force behind the complex magnetocrystalline anisotropy behavior, transitioning from cone to uniaxial above 170 K. The experimental data are compared with density functional theory, supplemented with a Hartree-Fock correction (+U) and an approximate dynamical mean-field theory.
Article
Chemistry, Multidisciplinary
Lukas Schaefer, Konstantin Skokov, Fernando Maccari, Iliya Radulov, David Koch, Andrey Mazilkin, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Oliver Gutfleisch
Summary: A novel magnetic hardening mechanism is described, where modified Nd-Fe-B alloys undergo a solid-state phase transformation to increase coercivity. The presence of FeMo2B2 precipitates after thermal treatment refines the Nd2Fe14B grains and further enhances coercivity.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Materials Science, Ceramics
A. Aubert, J. S. Garitaonandia, F. Maccari, J. Broetz, K. Skokov, O. Gutfleisch
Summary: Recent research has shown that uniaxial magnetic anisotropy can be induced in Cobalt ferrite (CFO) by reactive sintering using spark plasma sintering (SPS), improving its magnetostrictive properties. This study investigates the parameters responsible for the induced anisotropy and identifies that it arises during cooling under SPS's uniaxial compression. Additionally, the study explores the fundamental origin of the magnetic anisotropy and find that it is caused by the ionic distribution of Co2+ in the CFO's spinel lattice. These findings advance the understanding of the relationship between SPS processing and magnetic properties of cobalt ferrite.
CERAMICS INTERNATIONAL
(2023)
Article
Chemistry, Physical
I. Dirba, P. Pattur, I. Soldatov, E. Adabifiroozjaei, L. Molina-Luna, O. Gutfleisch
Summary: This study investigates the effect of grain boundary phase magnetism on coercivity in the quaternary Nd-Fe-Ga-Cu system. It is found that adjusting the Ce and Fe content, as well as infiltrating different materials, can effectively enhance the coercivity and temperature stability of magnets. The findings provide a better understanding of the influence of grain boundary phase magnetism on coercivity.
JOURNAL OF ALLOYS AND COMPOUNDS
(2023)
Article
Physics, Applied
I Dirba, C. K. Chandra, Y. Ablets, J. Kohout, T. Kmjec, O. Kaman, O. Gutfleisch
Summary: In this study, alternative materials systems with high magnetization and low anisotropy are investigated for their potential in delivering enhanced heating power in magnetic fluid hyperthermia. The performance of iron-nitrogen (Fe-N), iron-boron (Fe-B) and iron-carbon (Fe-C) compounds is compared to conventional iron oxides. The findings show that materials with high magnetization but low anisotropy provide the best combination for maximizing the specific loss power (SLP) in alternating magnetic fields.
JOURNAL OF PHYSICS D-APPLIED PHYSICS
(2023)
Article
Materials Science, Multidisciplinary
Kilian Schafer, Tobias Braun, Stefan Riegg, Jens Musekamp, Oliver Gutfleisch
Summary: Bonded permanent magnets are crucial components in energy conversion, sensor, and actuator devices. This study investigates the behavior and influence of large platelet-shaped magnetic fillers in laser powder bed fusion (LPBF) for producing bonded magnets. The 3D distribution and orientation of the fillers were examined using computed tomography and digital image analysis. The findings show that the platelet-shaped particles align themselves perpendicular to the build-up direction during the LPBF process, offering a new and cost-effective approach for producing anisotropic structural and functional composites.
MATERIALS RESEARCH BULLETIN
(2023)
Article
Materials Science, Multidisciplinary
Halil Ibrahim Soezen, Semih Ener, Fernando Maccari, Bahar Fayyazi, Oliver Gutfleisch, Joerg Neugebauer, Tilmann Hickel
Summary: In this paper, an ab initio based approach was used to modify the stability of Laves phases in the Ce-Fe-Ti system by adding 3d and 4d elements, resulting in improved thermodynamic stability. The critical annealing temperature for the formation of Ce(Fe,X)11Ti was determined using accurate free-energy calculations and efficient screening technique. Promising transition metals such as Zn and Tc were predicted to enhance the stability of the hard-magnetic phase. Comparison with other alloy experiments highlighted the importance of additional phases and quaternary elements.
PHYSICAL REVIEW MATERIALS
(2023)
Article
Materials Science, Multidisciplinary
Franziska Staab, Enrico Bruder, Lukas Scha, Konstantin Skokov, David Koch, Benjamin Zingsem, Esmaeil Adabifiroozjaei, Leopoldo Molina-Luna, Oliver Gutfleisch, Karsten Durst
Summary: Textured nanocrystalline SmCo5-Cu magnets are produced by high-pressure torsion (HPT) of powder blends consisting of SmCo5 and Cu powder. The process overcomes limitations imposed by the phase diagram as in conventional sintering routes, enabling a free selection of the magnetic phase and the grain boundary phase. Increasing number of rotations during HPT leads to structural refinement, increasing coercivity, and amorphous structure of strongly deformed SmCo5 particles. The magnetic hardening is attributed to microstructural refinement and magnetic decoupling of hard magnetic SmCo5 grains by Cu.
Article
Materials Science, Multidisciplinary
Benedikt Beckmann, David Koch, Lukas Pfeuffer, Tino Gottschall, Andreas Taubel, Esmaeil Adabifiroozjaei, Olga N. Miroshkina, Stefan Riegg, Timo Niehoff, Nagaarjhuna A. Kani, Markus E. Gruner, Leopoldo Molina-Luna, Konstantin P. Skokov, Oliver Gutfleisch
Summary: Ni-Mn-based Heusler alloys, especially all-d-metal Ni(-Co)-Mn-Ti, show promising potential for energy-efficient solid-state refrigeration. The study focuses on the transition entropy change and reveals a significant contribution from the structural entropy change, as well as a negative entropy change from the magnetic subsystem at lower temperatures. This phenomenon limits the utilization of these alloys for gas liquefaction at cryogenic temperatures.
Article
Materials Science, Multidisciplinary
Fernando Maccari, Tarini Prasad Mishra, Monica Keszler, Tobias Braun, Esmaeil Adabifiroozjaei, Iliya Radulov, Tianshu Jiang, Enrico Bruder, Olivier Guillon, Leopoldo Molina-Luna, Martin Bram, Oliver Gutfleisch
Summary: Flash spark plasma sintering (flash SPS) is an attractive method to obtain anisotropic Nd-Fe-B magnets with high magnetic performance by starting from melt-spun powders. The process promises electroplasticity and reduced tool wear, while maximizing magnetic properties through tailored microstructure. A parameter study reveals the importance of presintering conditions and preheating temperature on grain size and texture control. The best compromise between remanence and coercivity is achieved through a combination of specific parameters, resulting in a magnet with high energy product.
ADVANCED ENGINEERING MATERIALS
(2023)
Article
Chemistry, Multidisciplinary
Mohammad Farhan Tanzim, Nuno Fortunato, Ilias Samathrakis, Ruiwen Xie, Ingo Opahle, Oliver Gutfleisch, Hongbin Zhang
Summary: In this study, the anomalous Hall conductivities (AHC) and anomalous Nernst conductivities (ANC) of thermodynamically stable ferro/ferri-magnetic all-d-metal regular Heusler compounds were evaluated through high-throughput first-principles calculations. It was found that several materials exhibited giant AHC and ANC values, such as cubic Re2TaMn with an AHC of 2011 S cm(-1) and tetragonal Pt2CrRh with an AHC of 1966 S cm(-1) and an ANC of 7.50 A m(-1)K(-1). The high AHC values were attributed to the presence of Weyl nodes or gapped nodal lines near the Fermi level. The correlations between these transport properties and the number of valence electrons were also thoroughly investigated, providing a practical guide for tailoring AHC and ANC through chemical doping for transverse thermoelectric applications.
ADVANCED FUNCTIONAL MATERIALS
(2023)
Article
Physics, Applied
Jianing Liu, Ruiwen Xie, Alex Aubert, Lukas Schaefer, Hongbin Zhang, Oliver Gutfleisch, Konstantin Skokov
Summary: The understanding of the coercivity mechanism in Nd-Fe-B permanent magnets relies on the analysis of magnetic properties of all phases present in the magnets. In this study, Nd6Fe13Cu single crystals were grown and their magnetic properties were studied. It was observed that Nd6Fe13Cu is antiferromagnetic below the Neel temperature and exhibits a spin-flop transition in a magnetic field. Atomistic spin dynamics simulation confirmed the change in antiferromagnetic coupling between Nd layers above and below the Cu layers, which causes the spin-flop transition. These findings suggest that the role of the Nd6Fe13Cu grain boundary phase in the coercivity enhancement of Nd-Fe-B-Cu magnets is more complex than previously thought.
APPLIED PHYSICS LETTERS
(2023)
Article
Chemistry, Multidisciplinary
Weiwei He, Yan Yin, Qihua Gong, Richard F. L. Evans, Oliver Gutfleisch, Bai-Xiang Xu, Min Yi, Wanlin Guo
Summary: The existence of giant magnetocaloric effect (MCE) and its strain tunability in monolayer magnets, including CrX3 (X = F, Cl, Br, I), CrAX (A = O, S, Se; X = F, Cl, Br, I), and Fe3GeTe2, has been revealed through multiscale calculations. The maximum values of adiabatic temperature change (Delta T-ad(max)), isothermal magnetic entropy change, and specific cooling power in monolayer CrF3 are found to be as high as 11 K, 35 mu J m(-2) K-1, and 3.5 nW cm(-2) under a magnetic field of 5 T, respectively. The application of compressive strain can significantly increase Delta T-ad(max) of CrCl3 and CrOF by 230% and 37% (up to 15.3 and 6.0 K), respectively. It is observed that a large net magnetic moment per unit area favors improved MCE. These findings provide new opportunities for magnetic cooling at the nanoscale.
Article
Chemistry, Multidisciplinary
Nuno M. Fortunato, Andreas Taubel, Alberto Marmodoro, Lukas Pfeuffer, Ingo Ophale, Hebert Ebert, Oliver Gutfleisch, Hongbin Zhang
Summary: Magnetic refrigeration is an efficient and eco-friendly alternative to traditional vapor-cooling, but its implementation relies on materials with tailored magnetic and structural properties. This study introduces a high-throughput computational workflow for designing magnetocaloric materials, using density functional theory calculations to screen potential candidates in the MM'X compound family (M/M' = metal, X = main group element). Out of 274 stable compositions, 46 magnetic compounds are found to stabilize in both austenite and martensite phases. By evaluating and comparing the structural phase transition and magnetic ordering temperatures, nine compounds with structural transitions are identified as potential candidates based on the concept of the Curie temperature window. Additionally, the use of doping to tailor magnetostructural coupling and isostructural substitution as a general approach to engineer magnetocaloric materials is suggested.
Article
Energy & Fuels
Wei Liu, Tino Gottschall, Franziska Scheibel, Eduard Bykov, Nuno Fortunato, Alex Aubert, Hongbin Zhang, Konstantin Skokov, Oliver Gutfleisch
Summary: Magnetocaloric hydrogen liquefaction has the potential to revolutionize the liquid hydrogen industry. Light rare-earth based materials offer a more sustainable alternative to heavy rare-earth compounds, with higher abundances and greater magnetocaloric effects in the required temperature range. By tuning the Curie temperature of light rare-earth alloys and mixing different rare-earth elements, a fully light rare-earth intermetallic series is developed, showcasing competitive maximum effects for hydrogen liquefaction compared to heavy rare-earth compounds like DyAl2.
JOURNAL OF PHYSICS-ENERGY
(2023)
