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The corrosion and degradation of sintered Nd–Fe–B type magnets by hydrogen obtained from moisture in the environment has been termed the Negative Harris Effect. The residual hydrogen from the hydrogen decrepitation process in the manufacture of fully dense magnets is desorbed completely during the vacuum sintering …
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 decrepitation (HD) process and re-sintering NdFeB magnet scrap recycling by processing it in hydrogen, then milling, aligning, pressing and re-sintering it [38–40] Although different methods for NdFeB magnet recycling have been reported in the literature, only one piece of technology has been applied in practice by the Urban MiningNdFeB-based alloys and magnets also react readily with hydrogen, and this has been exploited by the hydrogen decrepitation (HD) process [4]. During HD the material is exposed to hydrogen (at room temperature) and initially the Nd-rich phase absorbs hydrogen (represented approximately by Eq.The hydrogen-absorbing NdFeB powder absorbs heat in the plasma and rapidly decomposes and dehydrogenates. At the same time, in the dehydrogenation process, the particles are cracked and broken to form fine NdFeB powder due to rapid heat absorption and release of a large amount of hydrogen, and the NdFeB powder is at a high …NdFeB ingot exposed to hydrogen atmosphere due to the changes of hydride lattice parameters cracks. The process called HDDR (Hydrogenation - …
A combination of hydrogen decrepitation (HD) and jet milling (JM) has been used to produce powder for the processing of permanent magnets. The procedure has proved to be very successful for both Nd-Fe-B (Neomax) alloys and the ND-Dy-Fe-Nb-B high coercivity alloys. The magnets produced by the HD/JM process showed excellent coercivities when …0.5% -1%. Dysprosium (Dy) 0.8% -1.2%. The method of manufacture of Neodymium Iron Boron magnets is as follows: The Neodymium metal element is initially separated from refined Rare Earth oxides in an electrolytic furnace. The “Rare Earth” elements are lanthanoids (also called lanthanides) and the term arises from the uncommon oxide …A combination of hydrogen decrepitation (HD) and jet milling (JM) has been used to produce powder for the processing of permanent magnets. ... The procedure has proved to be very successful for both NdFeB (Neomax) alloys and the NdDyFeNbB high coercivity alloys. The magnets produced by the HD/JM process showed excellent …
Novel hydrogen decrepitation behaviors of (La, Ce)-Fe-B strips. Jiaying Jin G. Bai +4 authors M. Yan. ... Doping with Dy/Tb is a current solution to improve the coercivity and the operating temperature of NdFeB magnets, by increasing the magnetocrystalline anisotropy of the (Nd, Dy/Tb)2Fe14B (2:14:1) …Jan 1, 2022 · The SC alloy is converted into a fine powder by hydrogen decrepitation and then jet-milling (JM) to produce a fine powder consisting almost entirely of single crystal particles of the Nd 2 Fe 14 B phase. This powder is then filled into fills molds and pressed while a magnetic field is applied to orient the individual particles. The compacted ...
The HD-process converts the magnets possible to recover the hard magnetic powder from a to a powder due to the expansion of the material on particular device (e.g. hard disk drive or electric motor) hydrogen absorption. Recycling of NdFeB magnets by by simply exposing the complete system to a hydrogen this means has been proposed by Rivoirard ...The fabrication of Nd-Fe-B sintered magnets is composed of quite a few processes mainly including strip casting, hydrogen decrepitation, jet-milling, magnetic alignment and pressing, sintering and subsequent heat treatment, machining, and surface coating. ... Possible methods of recycling NdFeB-type sintered magnets using the …The use of 3-D laser confocal microscopy to visualise hydrogen interactions in-sit; The use of hydrogen decrepitation to extract NdFeB magnets from electronic assemblies; In-situ removal of magnets from large magnetic assemblies using hydrogen; Corrosion protection for NdFeB magnets; Recycling of rare earth magnets; Strip casting …An essential information about history and applications of Hydrogen Decrepitation has been generally reported. Very important technical details about the HD route were summarized, as well as fabrication procedure of Nd16Fe76B8 permanent magnet. Some micro strucural of SEM images of hydride and sintered magnets were given to …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 …
The hydrogen decrepitation (HD) behaviors of various forms of the permanent magnet alloy Nd{sub 16}Fe{sub 76}B{sub 8} and stoichiometric composition Nd{sub 11.8}Fe{sub 82.3}B{sub 5.9} have been investigated to provide background information on the production of sintered magnets by the HD process. ... The procedure …
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.
Hydrogen decrepitation (HD) of Nd-Fe-B cast alloys is widely used in the processing of sintered magnets. The oxidation resistance under air of alloy powder …Hydrogen decrepitation as a highly efficient and excellent crushing method is widely used in the preparation of NdFeB magnets. ... Expand. 1. Save. The processing and characterisation of recycled NdFeB based magnets. S. Adrwish. Materials Science, Engineering. 2013; The scrap magnets were turned into a powder using the HD process. …@article{osti_37277, title = {Hydrogen decrepitation of sintered NdFeB magnets}, author = {Stiller, C and Roth, S and Binner, A}, abstractNote = {The kinetics of the hydrogen absorption and desorption behavior of a NdFeB sintered magnet is studied. Hydrogenation at temperatures above 200 C is used to crumble the Nd-enriched phase. …Semantic Scholar extracted view of "A study of the effects of the addition of various amounts of Cu to sintered NdFeB magnets" by O. Ragg et al. ... from an Nd/sub 17/-Fe/sub 76.5/-B/sub 5/-Cu/sub 1.5/ alloy by a two-step heat treatment at 1370 K and 870 K following hydrogen decrepitation (HD)-processing. …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 ...
May 5, 2023 · The first is the hydrogen decrepitation (HD) process, which is already used in the primary production of NdFeB magnets to convert the alloy into powder form before further comminution. 46 The second process, named HDDR, which consists of two different steps, namely hydrogenation–disproportionation (HD) and desorption–recombination (DR), was ... Hydrogen processing of magnetic scrap (HPMS) as one of the best approaches for magnet-to-magnet recycling is thoroughly reviewed in this study in terms …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 hydrogen decrepitation (HD) process are studied in detail based on these results. The hydrogen absorption mechanism of Sm(CoFeCuZr) 7.6 alloy can be regarded as a hydrogen dissolution process without phase transformation. In addition, the existence of a large amount of fine grains in the SC has an adverse effect on the …The hydrogen decrepitation (HD) behaviors of various forms of the permanent magnet alloy Nd 1 6 Fe 7 6 B 8 and stoichiometric composition Nd 11.8 Fe 82.3 B 5.9 have been investigated to provide background information on the production of sintered magnets by the HD process. The influence of the initial microstructures of the alloys on …The oxidation kinetics in air of a commercial NdFeB magnet have been investigated over the temperature range 335–500°C. The oxide microstructure has been characterized by SEM, XRD and cross-sectional TEM. The results show that the external scale formed consists of an outer layer of Fe2O3 and an inner layer of Fe3O4 but that the principal degradation …
Mar 1, 2019 · The Hydrogen Decrepitation process (HD) is used as an alternative method of powder preparation in the manufacturing process of sintered Nd Fe B magnets [1]. During the HD process a NdFeB-type material is hydrogenated by gaseous hydrogen at atmospheric (or elevated) pressure at room (or elevated) temperature.
The scrap sintered Nd–Fe–B magnets were recycled as the raw materials for bonded magnets using the hydrogen decrepitation (HD) process. The HD powders have the lowest oxygen and hydrogen content by hydrogenation at 150 °C with 1 bar H2 pressure and dehydrogenation at 600 °C. The powders with the largest particle size (>380 μm) …magnets. The thermal and mechanical impact of the hydrogen decrepitation process was assessed during hydrogen processing. For all forms of sintered NdFeB scrap the surface condition of the magnets is important as oxidation has been shown to inhibit the onset of the hydrogen decrepitation process. In this Jan 1, 2022 · The SC alloy is converted into a fine powder by hydrogen decrepitation and then jet-milling (JM) to produce a fine powder consisting almost entirely of single crystal particles of the Nd 2 Fe 14 B phase. This powder is then filled into fills molds and pressed while a magnetic field is applied to orient the individual particles. The compacted ... Dec 20, 2020 · Extraction of NdFeB from rotors using hydrogen. Seven semi-embedded rotors and non-embedded rotors were processed separately in two experiments. All the magnets in individual slots were scored in concentric circles using an angle grinder to provide a fresh surface for the hydrogen, as shown in Fig. 3, 15–30 min before being loaded into the ... 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.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 …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. …Due to the high strength and very compact structure of sintered NdFeB magnets, hydrogen decrepitation is a necessary step to break down the magnet mass. On the other hand, the resin-bonded NdFeB magnets have very low strength and can be easily crushed by heating and removing the resin and epoxy used in their fabrication. 39. 3.hydrogen uptake (2043.76 μmol∙g-1) was received for conditions 4 bar and room temperature, while the lowest (925.27 μmol∙g -1 ) for 1 bar at 400 0 C (Figure 4). At room temperature (29The 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 use of 3-D laser confocal microscopy to visualise hydrogen interactions in-sit; The use of hydrogen decrepitation to extract NdFeB magnets from electronic assemblies; In-situ removal of magnets from large magnetic assemblies using hydrogen; Corrosion protection for NdFeB magnets; Recycling of rare earth magnets; Strip casting …
The method combines hydrogen decrepitation (HD) disintegration of the initial magnet, powder sieving and the Press-Less Process (PLP), where hydride powder is sintered in a …
The scrap sintered Nd–Fe–B magnets were recycled as the raw materials for bonded magnets using the hydrogen decrepitation (HD) process. The HD powders have the lowest oxygen and hydrogen content by hydrogenation at 150 °C with 1 bar H2 pressure and dehydrogenation at 600 °C. The powders with the largest particle size (>380 μm) …A Hydrogen Decrepitation Press-Less Process (HD-PLP) recycling method for recycling of anisotropic NdFeB magnets is demonstrated. The method combines hydrogen decrepitation (HD) disintegration of the initial magnet, powder sieving and the Press-Less Process (PLP), where hydride powder is sintered in a graphite mold.Jan 1, 2006 · Several recycling methods for NdFeB magnets have been developed, such as direct reuse,4 hydrogen decrepitation (HD) and regeneration of new NdFeB,5–7 pyrometallurgical methods,8,9 hydrometallurgical methods,10–13 gas-phase extraction. Direct reuse is only suitable for large magnets, such as those used for wind turbines, electric motors, and ... The hydrogen decrepitation (HD) process are studied in detail based on these results. The hydrogen absorption mechanism of Sm(CoFeCuZr) 7.6 alloy can be regarded as a hydrogen dissolution process without phase transformation. In addition, the existence of a large amount of fine grains in the SC has an adverse effect on the …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 …This means that NdFeB magnets are prone to galvanic corrosion, in particular, intergranular corrosion attack. The corrosion mechanism as well as the hydrogen decrepitation behaviour of microcrystalline (i.e. sintered) magnets has been studied extensively [11], [12], [13], [14].This means that NdFeB magnets are prone to galvanic corrosion, in particular, intergranular corrosion attack. The corrosion mechanism as well as the hydrogen decrepitation behaviour of microcrystalline (i.e. sintered) magnets has been studied extensively [11], [12], [13], [14].Hydrogen decrepitation (HD) of the sintered block was used to return the annealed material back into a powder [33]. During this step, the material reacts with hydrogen resulting in volume expansion of both the Nd-rich phase, at triple junctions and grain boundaries, and the Nd 2 Fe 14 B matrix phase [34]. This expansion leads to …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 …
In this paper we describe and discuss the use of hydrogen in the processing ofNdFeB-type magnets. The roles of hydrogen in the hydrogen decrepitation (HD) and …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), …Oct 1, 2015 · Hydrogen is already used to process cast NdFeB in the Hydrogen Decrepitation (HD) process. The HD process is used extensively to reduce bulk (or strip) cast NdFeB ingots to friable, hydrogenated NdFeB granules/powder, prior to the production of jet milled powder which is then aligned, compressed and sintered to form fully dense sintered magnets ... Instagram:https://instagram. hapygeslyegsscomo es la posicion del 69rain x latitude wonkws kyr A Hydrogen Decrepitation Press-Less Process (HD-PLP) recycling method for recycling of anisotropic NdFeB magnets is demonstrated. The method combines hydrogen decrepitation (HD) disintegration of the initial magnet, powder sieving and the Press-Less Process (PLP), where hydride powder is sintered in a graphite mold. thibmovies like the hate u give The use of 3-D laser confocal microscopy to visualise hydrogen interactions in-sit; The use of hydrogen decrepitation to extract NdFeB magnets from electronic assemblies; In-situ removal of magnets from large magnetic assemblies using hydrogen; Corrosion protection for NdFeB magnets; Recycling of rare earth magnets; Strip casting …Hydrogen decrepitation (HD) is based on the selective synthesis of neodymium hydrides though the reaction of hydrogen gas with neodymium located in the Nd-Fe-B magnet. HD process was originally designed and patented by Harris et al. (1979) as a way to break down SmCo and Sm 2(Co,Fe,Cu,Zr) alloys. 5 17. ysyqvfpq High-temperature oxidation resistance of Nd–Fe–B magnetic powder is of great importance for its application in bonded magnet fields. In this work, the refinement and surface modification of Nd–Fe–B magnetic powders were integrated and achieved simultaneously. The effects of phosphoric acid, isopropyl tris-(dioctyl pyrophosphate …The behavior of hydrogen absorption in the NdFeB Hydrogen Decrepitation process is affected by the shape of the NdFeB alloy, pressure and temperature curves of the reaction process, which makes the reaction process with characteristics of nonlinear, time-varying parameters and coupling. In this study, we proposed a state space modeling …2.1. Introduction of this section. HDDR treatment is used to obtain Nd-Fe-B magnet powders with good magnetic anisotropy and high coercivity [6,8,19].Therefore, HDDR treatment has been used to produce anisotropic bonded magnets for high-performance motors in automobiles and electronic devices [20,21].In typical HDDR …