REE Recovery from End-of-Life NdFeB Permanent Magnet Scrap: A Critical Review

Yang, Yongxiang; Walton, Allan; Sheridan, Richard; Güth, K.; Gauß, Roland; Gutfleisch, Oliver; Buchert, Matthias; Steenari, Britt‐Marie; Gerven, Tom Van; Jones, Peter Tom; Binnemans, Koen

doi:10.1007/s40831-016-0090-4

Cited by 397 publications

(274 citation statements)

References 98 publications

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“…A stable relationship of risk was constructed between governments in the EU and in the US, and a common object of risk agreed upon that was evident in narratives of "supply risk". In response, many publicly funded projects have developed technologies for REE-separation and recycling on a lab-scale (see i.e., EC-funded FP7 or H2020 projects such as [77][78][79][80][81][82][83][84]) and the potential for recycling was discussed (e.g., [37,[85][86][87][88][89]). Surprisingly little progress occurred from lab-scale tests of the technologies to commercial implementation.…”

Section: Resultsmentioning

confidence: 99%

Governance and Risk–Value Constructions in Closing Loops of Rare Earth Elements in Global Value Chains

2017

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This article addresses a research gap on the challenges-specifically risk and value-connected to realizing the potential for closing loops for rare earth elements (REE). We develop an analytical framework from conceptual elements of the global value chain (GVC) framework and the relational theory of risk to examine several empirical REE industry cases for loop closure. The aim of the paper is to identify how risk-value relationships are constructed by different actors as governance structures form in transactions prior to price setting and how these have impacts on the closure of REE loops. Often, REE loops are not closed, and we find that constructions of the risk-value relationship by industrial actors and by government agencies are unstable as they pursue different motivations, consequently hindering REE loop closure in GVCs. In light of this, we propose that governments mediate against the construction of risk-value relationships by facilitating information on the characteristics of end-of-life materials that qualify these for re-entry into loops.

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Section: Resultsmentioning

confidence: 99%

Governance and Risk–Value Constructions in Closing Loops of Rare Earth Elements in Global Value Chains

2017

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“…These are the locations where the local demagnetizing field of the magnet reach the highest values [38]. Furthermore, near these edges the demagnetizing field is tilted with respect to the magnetization direction which reduces the local Stoner-Wohlfarth switching field according to (3). While the dependence of the local switching field on the grain orientation is known from the basic micromagnetic theory [19], the influence of the position of the grain on the local coercive field strength is less obvious.…”

Section: Discussionmentioning

confidence: 99%

Magnetic microstructure machine learning analysis

et al. 2018

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We use a machine learning approach to identify the importance of microstructure characteristics in causing magnetization reversal in ideally structured large-grained Nd 2 Fe 14 B permanent magnets. The embedded Stoner-Wohlfarth method is used as a reduced order model for determining local switching field maps which guide the data-driven learning procedure. The predictor model is a random forest classifier which we validate by comparing with full micromagnetic simulations in the case of small granular test structures. In the course of the machine learning microstructure analysis the most important features explaining magnetization reversal were found to be the misorientation and the position of the grain within the magnet. The lowest switching fields occur near the top and bottom edges of the magnet. While the dependence of the local switching field on the grain orientation is known from theory, the influence of the position of the grain on the local coercive field strength is less obvious. As a direct result of our findings of the machine learning analysis we show that edge hardening via Dy-diffusion leads to higher coercive fields.

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“…About 48% of total NdFeB magnets produced in 2012 were used in the production of motors, generators, HDD, CDs and DVDs. The amount being used varies between a few grams (e.g., loudspeakers) to tonnes of materials (e.g., wind turbines) [2].…”

Section: Introductionmentioning

confidence: 99%

Hydrocyclone Separation of Hydrogen Decrepitated NdFeB

et al. 2017

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Hydrogen decrepitation (HD) is an effective and environmentally friendly technique for recycling of neodymium-iron-boron (NdFeB) magnets. During the HD process, the NdFeB breaks down into a matrix phase (Nd 2 Fe 14 BH x ) and RE-rich grain boundary phase. The grain boundary phase in the HD powder is <2 µm in size. Recycled NdFeB material has a higher oxygen content compared to the primary source material. This additional oxygen mainly occurs at the Rare Earth (RE) rich grain boundary phase (GBP), because rare earth elements oxidise rapidly when exposed to air. This higher oxygen level in the material results in a drop in density, coercivity, and remanence of sintered NdFeB magnets. The particle size of the GBP is too small to separate by sieving or conventional screening technology. In this work, an attempt has been made to separate the GBP from the matrix phase using a hydrocyclone, and to optimise the separation process. HD powder, obtained from hard disk drive (HDD) scrap NdFeB sintered magnets, was used as a starting material and passed through a hydrocyclone a total number of six times. The X-ray fluorescence (XRF) analysis and sieve analysis of overflows showed the matrix phase had been directed to the underflow while the GBP was directed to the overflow. The optimum separation was achieved with three passes. Underflow and overflow samples were further analysed using an optical microscope and MagScan and matrix phase particles were found to be magnetic.

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REE Recovery from End-of-Life NdFeB Permanent Magnet Scrap: A Critical Review

Cited by 397 publications

References 98 publications

Governance and Risk–Value Constructions in Closing Loops of Rare Earth Elements in Global Value Chains

Governance and Risk–Value Constructions in Closing Loops of Rare Earth Elements in Global Value Chains

Magnetic microstructure machine learning analysis

Hydrocyclone Separation of Hydrogen Decrepitated NdFeB

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