Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods:: Effect of hydrogenation pre-treatment and magnet composition

Mehmet Ali Onal; Christian Jönsson; Wei Zhou; Tom Van Gerven; Muxing Guo; Allan Walton; Bart Blanpain

doi:10.1016/j.jallcom.2017.09.046

Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods: Effect of hydrogenation pre-treatment and magnet composition

Mehmet Ali Onal, Christian Jönsson, Wei Zhou, Tom Van Gerven, Muxing Guo, Allan Walton, Bart Blanpain

Research output: Contribution to journal › Article › peer-review

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Abstract

Recycling of Nd-Fe-B magnets is one of the few solutions to alleviate the supply risks of certain rare earth elements (REE) such as Nd and Dy. One of the most promising solutions with regards to extraction of end-of-life (EOL) magnets is to apply hydrogen decrepitation and to physically separate the Nd-Fe-B as a demagnetized hydrogenated powder. Such a powder can be directly recycled into new sintered magnets, or indirectly recycled by a conventional oxidation roasting and acid leaching flowsheet. The oxidation stability of powders, the microstructure after oxidation and the role of compositional variations can be of importance for the success of such subsequent direct or indirect recycling routes. In this study, magnets with varying compositions were subjected to different hydrogen treatments (e.g. hydrogenation, partial or full degassing and vacuum or conventional disproportionation) and subsequently studied for their comparative oxidation behavior and microstructural changes. While initial magnet composition was found to have little or no effect on oxidation behavior, the treatment type was found to have a direct impact on both the particle size distribution and the oxidation mechanism. The general oxidation rate was found to be the equally highest for hydrogenated and partially degassed samples followed by fully degassed and then disproportionated samples. After complete oxidation, complex REE-Fe-O compounds were formed more extensively in hydrogenated and fully degassed NdFeB samples than in the disproportionated samples.

Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods: Effect of hydrogenation pre-treatment and magnet composition. Available from: https://www.researchgate.net/publication/319592801_Comparative_oxidation_behavior_of_Nd-Fe-B_magnets_for_potential_recycling_methods_Effect_of_hydrogenation_pre-treatment_and_magnet_composition [accessed Nov 02 2017].

Original language	English
Pages (from-to)	727-738
Journal	Journal of Alloys and Compounds
Volume	728
Early online date	8 Sept 2017
DOIs	https://doi.org/10.1016/j.jallcom.2017.09.046
Publication status	Published - 25 Dec 2017

Keywords

Recycling
Nd-Fe-B magnet
Hydrogenation
Decrepitation
Disproportionation
Oxidation

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@article{17402112f7bd435481257a7d5d178793,

title = "Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods:: Effect of hydrogenation pre-treatment and magnet composition",

abstract = "Recycling of Nd-Fe-B magnets is one of the few solutions to alleviate the supply risks of certain rare earth elements (REE) such as Nd and Dy. One of the most promising solutions with regards to extraction of end-of-life (EOL) magnets is to apply hydrogen decrepitation and to physically separate the Nd-Fe-B as a demagnetized hydrogenated powder. Such a powder can be directly recycled into new sintered magnets, or indirectly recycled by a conventional oxidation roasting and acid leaching flowsheet. The oxidation stability of powders, the microstructure after oxidation and the role of compositional variations can be of importance for the success of such subsequent direct or indirect recycling routes. In this study, magnets with varying compositions were subjected to different hydrogen treatments (e.g. hydrogenation, partial or full degassing and vacuum or conventional disproportionation) and subsequently studied for their comparative oxidation behavior and microstructural changes. While initial magnet composition was found to have little or no effect on oxidation behavior, the treatment type was found to have a direct impact on both the particle size distribution and the oxidation mechanism. The general oxidation rate was found to be the equally highest for hydrogenated and partially degassed samples followed by fully degassed and then disproportionated samples. After complete oxidation, complex REE-Fe-O compounds were formed more extensively in hydrogenated and fully degassed NdFeB samples than in the disproportionated samples. Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods: Effect of hydrogenation pre-treatment and magnet composition. Available from: https://www.researchgate.net/publication/319592801_Comparative_oxidation_behavior_of_Nd-Fe-B_magnets_for_potential_recycling_methods_Effect_of_hydrogenation_pre-treatment_and_magnet_composition [accessed Nov 02 2017].",

keywords = "Recycling, Nd-Fe-B magnet, Hydrogenation, Decrepitation, Disproportionation, Oxidation",

author = "Onal, {Mehmet Ali} and Christian J{\"o}nsson and Wei Zhou and {Van Gerven}, Tom and Muxing Guo and Allan Walton and Bart Blanpain",

year = "2017",

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day = "25",

doi = "10.1016/j.jallcom.2017.09.046",

language = "English",

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TY - JOUR

T1 - Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods:

T2 - Effect of hydrogenation pre-treatment and magnet composition

AU - Onal, Mehmet Ali

AU - Jönsson, Christian

AU - Zhou, Wei

AU - Van Gerven, Tom

AU - Guo, Muxing

AU - Walton, Allan

AU - Blanpain, Bart

PY - 2017/12/25

Y1 - 2017/12/25

N2 - Recycling of Nd-Fe-B magnets is one of the few solutions to alleviate the supply risks of certain rare earth elements (REE) such as Nd and Dy. One of the most promising solutions with regards to extraction of end-of-life (EOL) magnets is to apply hydrogen decrepitation and to physically separate the Nd-Fe-B as a demagnetized hydrogenated powder. Such a powder can be directly recycled into new sintered magnets, or indirectly recycled by a conventional oxidation roasting and acid leaching flowsheet. The oxidation stability of powders, the microstructure after oxidation and the role of compositional variations can be of importance for the success of such subsequent direct or indirect recycling routes. In this study, magnets with varying compositions were subjected to different hydrogen treatments (e.g. hydrogenation, partial or full degassing and vacuum or conventional disproportionation) and subsequently studied for their comparative oxidation behavior and microstructural changes. While initial magnet composition was found to have little or no effect on oxidation behavior, the treatment type was found to have a direct impact on both the particle size distribution and the oxidation mechanism. The general oxidation rate was found to be the equally highest for hydrogenated and partially degassed samples followed by fully degassed and then disproportionated samples. After complete oxidation, complex REE-Fe-O compounds were formed more extensively in hydrogenated and fully degassed NdFeB samples than in the disproportionated samples. Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods: Effect of hydrogenation pre-treatment and magnet composition. Available from: https://www.researchgate.net/publication/319592801_Comparative_oxidation_behavior_of_Nd-Fe-B_magnets_for_potential_recycling_methods_Effect_of_hydrogenation_pre-treatment_and_magnet_composition [accessed Nov 02 2017].

AB - Recycling of Nd-Fe-B magnets is one of the few solutions to alleviate the supply risks of certain rare earth elements (REE) such as Nd and Dy. One of the most promising solutions with regards to extraction of end-of-life (EOL) magnets is to apply hydrogen decrepitation and to physically separate the Nd-Fe-B as a demagnetized hydrogenated powder. Such a powder can be directly recycled into new sintered magnets, or indirectly recycled by a conventional oxidation roasting and acid leaching flowsheet. The oxidation stability of powders, the microstructure after oxidation and the role of compositional variations can be of importance for the success of such subsequent direct or indirect recycling routes. In this study, magnets with varying compositions were subjected to different hydrogen treatments (e.g. hydrogenation, partial or full degassing and vacuum or conventional disproportionation) and subsequently studied for their comparative oxidation behavior and microstructural changes. While initial magnet composition was found to have little or no effect on oxidation behavior, the treatment type was found to have a direct impact on both the particle size distribution and the oxidation mechanism. The general oxidation rate was found to be the equally highest for hydrogenated and partially degassed samples followed by fully degassed and then disproportionated samples. After complete oxidation, complex REE-Fe-O compounds were formed more extensively in hydrogenated and fully degassed NdFeB samples than in the disproportionated samples. Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods: Effect of hydrogenation pre-treatment and magnet composition. Available from: https://www.researchgate.net/publication/319592801_Comparative_oxidation_behavior_of_Nd-Fe-B_magnets_for_potential_recycling_methods_Effect_of_hydrogenation_pre-treatment_and_magnet_composition [accessed Nov 02 2017].

KW - Recycling

KW - Nd-Fe-B magnet

KW - Hydrogenation

KW - Decrepitation

KW - Disproportionation

KW - Oxidation

U2 - 10.1016/j.jallcom.2017.09.046

DO - 10.1016/j.jallcom.2017.09.046

M3 - Article

SN - 0925-8388

VL - 728

SP - 727

EP - 738

JO - Journal of Alloys and Compounds

JF - Journal of Alloys and Compounds

ER -

Comparative oxidation behavior of Nd-Fe-B magnets for potential recycling methods: Effect of hydrogenation pre-treatment and magnet composition

Abstract

Keywords

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