Improved HDDR processing route for production of anisotropic powder from sintered NdFeB type magnets

Sheridan, Richard; Williams, A.; Harris, I.R.; Walton, Allan

doi:10.1016/j.jmmm.2013.09.042

Cited by 53 publications

(38 citation statements)

References 10 publications

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“…A medical device magnet was measured in a similar way along the two perpendicular directions. It was necessary to determine the temperature and the hydrogen pressure required for an initialization of the disproportionation reaction because the hydrogenation, disproportionation, desorption and recombination process (HDDR) process is considered as a possible method for recycling of the magnets [9]. Hydrogen disproportionation phase diagrams were constructed for both kinds of the magnets at various temperatures in a range of 500-100 • C. The HDDR reaction is based on a reversal phase transformation (disproportionation and recombination) described by the following formula:…”

Section: Methodsmentioning

confidence: 99%

Complex Characteristics of Sintered Nd-Fe-B Magnets in Terms of Hydrogen Based Recycling

et al. 2017

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Sintered Nd-Fe-B magnets, dismantled by the P.P.H.U. Polblume company from scrap hard disc drives and medical device, were thermally demagnetized and analyzed in terms of their chemical composition, structure and magnetic properties. Magnets from hard disc drives drives had a magnetic structure of two opposite poles in a plane of a magnet and were covered with a nickel coating (around 50 µm in thick), which however was often discontinuous and deeply scratched. The majority of the magnets were partially destroyed (broken or corroded). The magnet from hard disc drives were basically made of iron (65±1 wt%) and neodymium (30±2 wt%) however, they also included alloying elements such as Co (1-2.5 wt%), Dy (0-1 wt%) or Pr (0-5 wt%). The magnets from medical device consisted only of iron (65±1 wt%) and neodymium (34±1 wt%). Magnets of both kinds were textured thus their XRD patterns were amended. Diffraction patterns, typical for the Nd2Fe14B (ϕ) phase, were achieved after mechanical crushing of the bulk magnets. A regular X-ray diffraction pattern was achieved after mechanical crushing of the magnets. The microstructure of both types of the magnets, observed by scanning electron microscopy, consisted of grey grains of a Nd2Fe14B (ϕ) phase and a Nd-rich grain boundary phase. The magnets from hard disc drives exhibited excellent magnetic properties and anisotropy: maximum energy product above 300 kJ/m 3 , remanence around 1.4 T and coercivity around 1000 kA/m, slightly varying between each magnet. Magnetic properties of medical magnet were only a little worse: maximum energy product above 200 kJ/m 3 , remanence around 1.1 T and coercivity around 900 kA/m. Hydrogen disproportionation phase diagrams (temperature vs. pressure) were constructed for both kinds of the magnets, revealing possible conditions for the hydrogenation, disproportionation, desorption and recombination reaction.

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Section: Methodsmentioning

confidence: 99%

Complex Characteristics of Sintered Nd-Fe-B Magnets in Terms of Hydrogen Based Recycling

et al. 2017

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“…The nominal composition of the alloy was Nd 15 Fe 79 B 6 . There is an excess of neodymium (Nd/Fe = 0,19) in respect to the stochiometric Nd 2 Fe 14 B phase (Nd/Fe = 0,14).…”

Section: Methodsmentioning

confidence: 99%

Structure and Properties of Nd-Fe-B Alloy Subjected to HDDR Process

Szymański¹,

Michalski²,

Leonowicz³

et al. 2016

Archives of Metallurgy and Materials

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In this paper the Hydrogenation, Disproportionation, Desorption and Recombination (HDDR) route was tested, for the Nd-Fe-B master alloy, as a prospective procedure for recycling of sintered scrap neodymium magnets. The HDDR method is based on the hydrogen induced reversal phase transformation of Nd-Fe-B alloy: Nd2Fe14B + (2±x) H2 = 2NdH2±x + Fe2B + 12Fe. Microstructural observations (SEM), phase constitution studies (XRD) and measurement of magnetic properties (VSM) were done to investigate the HDDR transformation progress. It was observed that disproportionation reaction starts at the grain boundaries, where the Nd-rich phase is located. Average grain size was reduced and coercive material was produced as a result of the HDDR process. Obtained results are similar to literature data.

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“…Hydrogen decrepitation (HD)/hydrogenation disproportionation desorption recombination (HDDR) is a process used in manufacturing REPM and carried out as pretreatment before green body sintering. During hydrogenation, the Nd-rich grain boundary phase in NdFeB magnets initially absorbs hydrogen forming Nd hydride: [49].…”

Section: Recycling Via Hydrogenationmentioning

confidence: 99%

“…The powder can be used in the production of resin bonded magnets either by degassing the hydrogen under vacuum and mixing with an appropriate binder or by further processing of the powder by the HDDR route. This process has been further developed [46,47,49,50] to increase the recycling efficiency. Périgo et al [77] employed the HDDR process to recycle N42 sintered magnets to make isotropic powders and investigated the effect of recombination temperature and H 2 pressure on the magnetic properties of recycled magnets.…”

Section: Recycling Via Hydrogenationmentioning

confidence: 99%

“…Figure 15 shows qualitatively the processing conditions and hydrogen pressure evolution during the combined d-HDDR process. Sheridan et al [49] found that the best magnetic properties were achieved by processing at 1153 K, producing a sample with a magnetic remanence of 1.08 (70.02) T and an intrinsic coercivity of around 840 kA/m. However, magnetic properties of the lower Dy content magnet were affected significantly by the processing temperature with a peak in properties observed at 1153 K.…”

Section: Recycling Via Hydrogenationmentioning

confidence: 99%

See 1 more Smart Citation

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

Firdaus

Rhamdhani

Durandet

et al. 2016

J. Sustain. Metall.

108

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Rare-earth metals, particularly neodymium, dysprosium, and praseodymium are becoming increasingly important in the transition to a green economy due to their essential role in permanent magnet applications such as in electric motors and generators. With the increasingly limited rare-earth supply and complexity of processing Nd, Dy, and Pr from primary ores, recycling of rare-earth based magnets has become a necessary option to manage supply and demand. Depending on the form of the starting material (sludge or scrap), there are different routes that can be used to recover neodymium from secondary sources, ranging from hydrometallurgical (based on its primary production process), electrochemical to pyrometallurgical. Pyrometallurgical routes provide solution in cases where water is scarce and generation of waste is to be limited. This paper presents a systematic review of previous studies on the high-temperature (pyrometallurgical) recovery of rare earths from magnets. The features and conditions at which the recycling processes had been studied are mapped and evaluated technically. The review also highlights the reaction mechanisms, behaviors of the rare-earth elements, and the formation of intermediate compounds in high-temperature recycling processes. Recommendations for further scientific research to enable the development of recovery of the rare-earth and magnet recycling are also presented.

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Improved HDDR processing route for production of anisotropic powder from sintered NdFeB type magnets

Cited by 53 publications

References 10 publications

Complex Characteristics of Sintered Nd-Fe-B Magnets in Terms of Hydrogen Based Recycling

Complex Characteristics of Sintered Nd-Fe-B Magnets in Terms of Hydrogen Based Recycling

Structure and Properties of Nd-Fe-B Alloy Subjected to HDDR Process

Review of High-Temperature Recovery of Rare Earth (Nd/Dy) from Magnet Waste

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