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Received 21st February 2020, Accepted 5th March 2020. meric portion. The PA-free magnet powder was found to retain >90% of its original magnetic properties. Two epoxy-bonded magnets produced with this recycled magnet powder showed magnetic properties. DOI: 10.1039/d0gc00647e.
Abstract. Some fully dense, sintered NdFeB-type magnets (employed in VCM disc drives) have been subjected to a recycling process using the hydrogen decrepitation (HD) process. After a brief milling treatment, the powder was aligned, pressed and re-sintered and this procedure was repeated four times with a progressive fall in the density …Hydrogen Decrepitation is a process step used in the production of Neodymium magnets to create extremely small grains in the material. Neodymium magnets must have very small grains averaging about 5 micrometers in order to have the best magnetic properties. But the grain sizes after casting are much larger than that, so they must be ground down ... Hydrogen decrepitation and recycling of NdFeB-type sintered magnets Zakotnik M, Devlin E, Harris IR, Williams AJ ... Environmental degradation of NdFeB magnets Yan GL, McGuiness PJ, Farr JPG, Harris IR Journal of Alloys and Compounds 2009;478:188-92 Oxidation of NdFeB-type magnets modified with additions of Co, Dy, Zr and V ...Various anti-corrosion coatings used on commercially available NdFeB-type magnets were comparatively examined for their durability and suitability for magnet reprocessing by hydrogen-assisted recycling (HPMS). Layer thickness and structure were determined by systematic microstructural analysis, and a standardized corrosion test …NdFeB sintered magnet material has been developed. The magnets are produced by powder metallurgy route involving hydrogen decrepitation technique for making fine powder. After melting and casting ...
The invention relates to a hydrogen decrepitation process for sintered Nd-Fe-B permanent magnets and belongs to the technical field of magnetic materials. The hydrogen decrepitation process includes melting metal materials, quickly solidifying the metal materials into cast pieces, activating the cast pieces under a certain condition, namely …The influence of the alloy granulation grade, temperature and surface oxidation on the kinetics and the course of the fracture processes during the hydrogenation of Nd16−xDyxFe76B8 (x=0–3) alloy was studied. The average particle sizes of the alloy were 1 mm, 5 mm and 3 cm and the temperature range between 20 and 200 °C. Pre-oxidation …
Nov 14, 2017 · Abstract: 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 (Nd2Fe14BHx) and RE-rich grain boundary phase. The grain boundary phase in the HD powder is <2 m in size. The MMG has been active in the field of rare earth alloys and processing of permanent magnets using hydrogen for over 40 years. Originated by Professor Emeritus Rex Harris, the hydrogen decrepitation method, which is used to reduce NdFeB alloys to a powder, is now ubiquitously employed in worldwide magnet processing.
Nov 1, 2017 · Fig. 1. Illustration of the Hydrogen Decrepitation Press-Less Process (HD-PLP) recycling of anisotropic sintered NdFeB magnet. Passivated commercial N48M sintered magnets were used as starting material and hydrogen was applied to disintegrate the magnets inside a ball milling container. The hydride powder was both used directly and some powder ... As starting materials, magnets of different grades were used, which were processed by hydrogen decrepitation and blending the powder with NdH x. Composition inhomogeneity in the Nd 2 Fe 14 B-based magnetic phase grains in the recycled magnets and the existence of a core-shell structure consisting of a Nd-rich (Dy-depleted) core and …The Hydrogen Decrepitation and the Hydrogen Disproportionation Desorption Recombination processes for the preparation and the recycling of the two industrially produced phases of SmCo alloys, SmCo5 and Sm2Co17, are reviewed. The effects of the chemical composition, the microstructure, the exposure time, the hydrogen …Abstract. This paper reports the room temperature hydrogen decrepitation (HD) of fully dense, 2/17-type sintered magnets based on the composition, Sm (Co 0.69 Fe 0.21 Cu 0.068 Zr 0.019) 7.49. These magnets absorb significant amounts of hydrogen over an extended period (∼48 h) at room temperature and at a pressure of 10 bar to give a …
Hydrogen decrepitation of Nd-Fe-B type magnet alloys is a two stage process. Firstly, the hydrogen reacts with the Nd-rich phase at or close to room …
The Hydrogen Decrepitation and the Hydrogen Disproportionation Desorption Recombination processes for the preparation and the recycling of the two industrially produced phases of SmCo alloys, SmCo5 and Sm2Co17, are reviewed. The effects of the chemical composition, the microstructure, the exposure time, the hydrogen …
Jan 1, 2020 · Hydrogen decrepitation (HD) can be used as a direct reuse approach and effective method of recycling process to turn solid sintered magnets into a demagnetised powder for further processing. Another example of the coercivity recovery in crushed NdFeB-type sintered magnets was made by adding the DyF 3 salt [8]. Furthermore, the production of anisotropic RE–Fe–B–Cu powders have also been produced by hydrogen decrepitation of hot deformed ingots [9] followed by degassing.Investigating the properties of recycled NdFeB magnets. We report investigations on the processing by Spark Plasma Sintering (SPS) of RE Fe B (RE Abstract 2 14 = Nd, Pr. . . ) powders obtained by hydrogen decrepitation of decommissioned magnets and the magnetic properties of the consolidated magnets.High performance NdFeB permanent magnets are widely manufactured using the conventional powder metallurgy route involving distinct steps: alloy synthesis by strip casting, pulverization by hydrogen decrepitation and jet milling, shaping by compaction and sintering followed by annealing [32]. Every step of this manufacturing process has …This way of powdering known as hydrogen decrepitation (HD) is a well-established stage of manufacturing technologies of sintered [2], [3] and bonded [4] Nd–Fe–B magnets. The interstitial hydrogen in the ferromagnetic Nd 2 Fe 14 B phase reduces significantly its anisotropy field H A. That is why desorption of hydrogen is necessary in …The U.S. Department of Energy's Office of Scientific and Technical InformationThe room temperature hydrogenation causes decrepitation of the material, where the Nd-rich material forms NdH 2.7 and the Nd 2 Fe 14 B matrix grains form an interstitial hydrogen solution. The material expands by ∼5% and because of its brittle nature and differential expansion, undergoes decrepitation [16] .
The nature of hydrogen decrepitation when applied to a cast Nd-Fe-B permanent magnet alloy has been studied by following the microstructural changes on polished surfaces of the material exposed to hydrogen at a pressure of 4 bar. The milling of the material decrepitated at a pressure of 10 bar has also been studied by determining …Aug 4, 2022 · Here, we describe a room temperature, electrolytic decrepitation process applied to sintered Nd 2 Fe 14 B magnet fragments taken from end-of-life computer hard disk drives. In this process, fine grain, Nd-magnet-hydride powder is rapidly produced by atomic hydrogen in a 2 M KOH electrolyte. The intrinsic magnetic coercivity (H ci) of Nd‐Fe‐B‐based permanent magnet material is profoundly affected by hydrogen absorbed during the hydrogen decrepitation (HD) process for producing anisotropic powders from bulk anisotropic hot‐deformed MAGNEQUENCH (MQ) magnets.Hydrogen (H) content and x‐ray diffraction …The decrepitation process and related changes in the sample temperature are analysed to explain the experimentally observed weight gain curve of a Nd–Fe–B sample due to hydrogen uptake. It is shown that the expansion of the specific surface resulting from decrepitation of the sample is the most important parameter controlling …Hydrogen Decrepitation is a process step used in the production of Neodymium magnets to create extremely small grains in the material. Neodymium magnets must have very small grains averaging about 5 micrometers in order to have the best magnetic properties. But the grain sizes after casting are much larger than that, so they must be ground down ... Aug 4, 2022 · Here, we describe a room temperature, electrolytic decrepitation process applied to sintered Nd 2 Fe 14 B magnet fragments taken from end-of-life computer hard disk drives. In this process, fine grain, Nd-magnet-hydride powder is rapidly produced by atomic hydrogen in a 2 M KOH electrolyte.
Hydrogen absorption and desorption characteristics for high coercivity NdDyFeCoNbCuB sintered bulk magnets were studied, by differential scanning calorimetry (DSC) measurement and hydrogenation kinetics measurement. The DSC measurements showed that hydrogenation of Nd-rich phase occurred in the temperature range of …
The behavior of hydrogen absorption and release in hydrogen decrepitation (HD) process of Nd-Fe-B alloys were investigated. The results reveal that the reactivity and the amount of hydrogen absorption in HD process are related to the surface activity of the alloy so that the fresh and active surface has a higher efficiency. The presence of Nd-rich phase at the …Hydrogen Decrepitation is a process step used in the production of Neodymium magnets to create extremely small grains in the material. Neodymium magnets must have very small grains averaging about 5 micrometers in order to have the best magnetic properties. But the grain sizes after casting are much larger than that, so they must be ground down ... This work could have implications with regard to the mechanism of hydrogen decrepitation of sintered NdFeB magnets during the well-established recycling process described by Walton et al. [19] and [20]. During this process, scrap sintered NdFeB magnets are damaged in air to expose a clean surface suitable for hydrogen decrepitation. …Abstract: Hydrogen decrepitation (HD) is an effective and environmentally friendly technique for recycling of neodymium-iron-boron (NdFeB) magnets. During the …Apr 15, 2022 · An effective and complete processing route for the recycling of sintered Nd-Fe-B scrap magnets was proposed. Sintered Nd-Fe-B magnets were subjected to the Hydrogen Decrepitation (HD) process at various temperatures in the range of 50–300 °C, at two different pressures, 50 kPa and 200 kPa, followed by vacuum dehydrogenation in the range of 720–820 °C. Jul 1, 2002 · The effective diffusivity of hydrogen in NdFeB magnets is reduced with Co and Ga additions and as a result of the texture induced in the microstructure via die-upsetting process. In addition to the results shown in Fig. 8 , the thermal desorption behaviour related to the hydrogenation of a die-upset MQU-G magnet is different for the two ... PDF (11 MB) Get e-Alerts SUBJECTS: Grain, Hydrogen, Hydrogenation, Magnetic properties, Organic reactions Abstract Regarding the restrictions recently imposed by China on the export of rare-earth elements (REEs), …Jan 1, 2006 · In this paper it is demonstrated that hydrogen could play a vital role in this process. Fully dense, sintered NdFeB-type magnets have been subjected to the hydrogen decrepitation (HD) process. The resultant powder has been subsequently processed in one of two ways in order to produce permanent magnets. The room temperature hydrogenation causes decrepitation of the material, where the Nd-rich material forms NdH 2.7 and the Nd 2 Fe 14 B matrix grains form an interstitial hydrogen solution. The material expands by ∼5% and because of its brittle nature and differential expansion, undergoes decrepitation [16].
In this paper it is demonstrated that hydrogen could play a vital role in this process. Fully dense sintered NdFeB-type magnets have been subjected to the hydrogen decrepitation (HD) process.
Broadening the knowledge about the hydrogen decrepitation of the NdFeB type materials is needed to better service the process e.g. for recycling (at room temperature only 4 out of 10 scrap magnets undergo decrepitation which is likely to be the result of the number and character of pin holes in the electroplated coatings and/or to possible ...
Sep 17, 2021 · It is therefore expected that cracks are decreased by performing hydrogen decrepitation at higher temperature. To confirm this, the relationship between T dec (23°C–600°C) and the crack density D c was investigated. Here, D c was estimated by dividing the crack length in an SEM image by the cross-sectional area of the same image. Apr 15, 2022 · An effective and complete processing route for the recycling of sintered Nd-Fe-B scrap magnets was proposed. Sintered Nd-Fe-B magnets were subjected to the Hydrogen Decrepitation (HD) process at various temperatures in the range of 50–300 °C, at two different pressures, 50 kPa and 200 kPa, followed by vacuum dehydrogenation in the range of 720–820 °C. The nature of hydrogen decrepitation when applied to a cast Nd-Fe-B permanent magnet alloy has been studied by following the microstructural changes on polished surfaces of the material exposed to hydrogen at a pressure of 4 bar. The milling of the material decrepitated at a pressure of 10 bar has also been studied by determining …Hydrogen Decrepitation and Recycling of NdFeB-type Sintered Magnets. Miha Zakotnik, E. Devlin, +1 author. A. Williams. Published 2006. Materials Science, Engineering. Journal of Iron and Steel Research International. View via Publisher. Save to Library.International Journal of Hydrogen Energy. Volume 24, Issues 2–3, 1 March 1999, Pages 257-261. Application of hydrogen vibration milling in theprocessing of NdFeB and (Nd, Pr)FeB permanent magnets. Author links open overlay panel R.S Mottram 1, V Yartys 2, P.W Guegan 1, I.r Harris 1. Show more.So exposure at LOW temperature to hydrogen leads the NdFeB pieces to react via intergranular fracturation (decrepitation), the mass of Nd2Fe14B grains forminfg a metal hydride with max ... The processing and characterisation of recycled NdFeB-type sintered magnets. M. Degri. Materials Science, Engineering. 2014. A study of the processing and characterisation of sintered NdFeB magnets made from recycled feed stock was undertaken. Initially the hydrogen decrepitated (HD) powder was investigated using two…. Expand. The influence of the alloy granulation grade, temperature and surface oxidation on the kinetics and the course of the fracture processes during the hydrogenation of Nd16−xDyxFe76B8 (x=0–3) alloy was studied. The average particle sizes of the alloy were 1 mm, 5 mm and 3 cm and the temperature range between 20 and 200 °C. Pre-oxidation …magnets from electrical and electronic equipment. These materials are then processed using hydrogen decrepitation to transform the NdFeB magnets into a hydrogenated powder. This powder can then be extracted mechanically from the obsolete devices, and can then be processed further to produce either sintered or bonded rare earth magnets.Sep 17, 2021 · It is therefore expected that cracks are decreased by performing hydrogen decrepitation at higher temperature. To confirm this, the relationship between T dec (23°C–600°C) and the crack density D c was investigated. Here, D c was estimated by dividing the crack length in an SEM image by the cross-sectional area of the same image.
This paper studied the corrosion behavior of c ∥ and c ⊥ surfaces in sintered (Ce 0.15 Nd 0.85) 30 Fe bal B magnets. The conclusions are as follows: (1) The distribution of RE-rich phase is improved after Ce substitution compared with the sintered Nd-Fe-B magnets, and the value of A0 / A1 is approximate for both c ∥ and c ⊥ surfaces.Hydrogen Decrepitation (HD) has been used as an efficient and economical method in producing coarse NdFeB powder. This article studied the effects of hydrogen on the Nd-Dy-Fe-B magnets, such as HD ...Hydrogen absorption/adsorption properties of high coercivity NdDyFeCoNbCuB sintered magnets were determined. Hydrogenation kinetics were analyzed using both differential scanning calorimetry (DSC) and X-ray diffraction (XRD). Hydrogenation of the Nd-rich intergranular phase results in a rather broad and large peak …Instagram:https://instagram. 10dollar stocksfc155da2 88e1 406c b996 4c347e241160vill vinstall dbt core 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 (Nd2Fe14BHx) and RE-rich grain boundary phase. The grain boundary phase in the HD powder is <2 μm in size. Recycled NdFeB material has …The process of hydrogen decrepitation (HD), which is used in the primary production and recycling of Nd magnets, takes place at low temperatures, even at room temperature, so that the entire microstructure decomposes only in powder form and the grain size is reduced. eddiepercent27s carryoutno hard feelings showtimes near west wind sacramento 6 drive in Step #5 Hydrogen Decrepitation While the grains are very small from strip casting, the material from strip casting comes out of the caster in sheets that must be reduced to powder in order to make magnets. The next step after this is Hydrogen Decrepitation –a process that introduces hydrogen to purposely disintegrate the magnet material. NdFeB sintered magnet material has been developed. The magnets are produced by powder metallurgy route involving hydrogen decrepitation technique for making fine powder. After melting and casting ... dodge grand caravan won The invention relates to a hydrogen decrepitation process for sintered Nd-Fe-B permanent magnets and belongs to the technical field of magnetic materials. The hydrogen decrepitation process includes melting metal materials, quickly solidifying the metal materials into cast pieces, activating the cast pieces under a certain condition, namely …Originated by Professor Rex Harris, the hydrogen decrepitation method, which is used to reduce NdFeB alloys to a powder, is now ubiquitously employed in worldwide magnet processing.Abstract. Some fully dense, sintered NdFeB-type magnets (employed in VCM disc drives) have been subjected to a recycling process using the hydrogen decrepitation (HD) process. After a brief milling treatment, the powder was aligned, pressed and re-sintered and this procedure was repeated four times with a progressive fall in the density …