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Magnetic powders for sintered NdFeB magnets have been prepared by using an advanced processing method including strip casting, hydrogen decrepitation, jet milling and rubber isotropic press. The effects of Dy, Ga and Co addition on the microstructure and magnetic properties of sintered magnets have been investigated. By adopting a suitable …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 thisHigh 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 …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), …Step 3: Hydrogen Decrepitation. Rare earth elements have hydrogen absorption effect. NdFeB magnet alloy sheets are placed in a vacuum tube rotary furnace. As hydrogen gas is filled, rare earth-rich phase in the grain boundary of NdFeB magnet alloy absorbs hydrogen gas. After hydrogen absorption saturated, the rare earth-rich phase turns to ...T D ACCEPTED MANUSCRIPT The Use of Hydrogen to Separate and Recycle Neodymium-Iron-Boron-type Magnets from Electronic Waste A. Walton a, Han Yi , N.A. Rowson b, J.D. Speight , V.S.J. Mann a, R.S. Sheridan , A. Bradshaw a, I.R. Harris a, A.J. Williams School of Metallurgy and Materials a and School of Chemical Engineering b, …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 …Oct 1, 2020 · INET-3 is efficient to recover and separate Dy, Nd, and Co from NdFeB leachates. Its ΔpH 0.5 values of Fe-Dy, Dy-Nd, and Nd-Co are 0.35, 0.79, and 2.49, respectively. It is better to remove Fe 3+ by selective leaching and precipitation before Dy, Nd, and Co recovery and separation. 98% of Dy 3+ is recovered after four-stage counter-current extraction at A/O = 1:2 and equilibrium pH = 2.52. Over the last ten years several groups have been carrying out research into metal injection moulding (MIM) of neodymium-iron-boron (NdFeB) powders to produce isotropic or …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 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. Coercivities up to 534 kA/m were obtained in porous samples based on powder size d < 100 µm. Adding a ball milling step resulted in full density …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].Jul 14, 2000 · 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 the hydrogen ... The powders were produced by hydrogen decrepitation and on heating, hydrogen evolution occurred in two stages: firstly from the matrix phase (~170 ~ and then from the neodymium-rich phase (350-750 ~ The neodymium-rich phase melted at ~630 ~ and no significant microstructural changes occurred below this temperature.Seven methods of production have been summarized, starting with the conventional powder metallurgy route and ending by the Hydrogen Decrepitation (HD) route, as they are the most applicable routes in this field. The advantages and disadvantages of the reported routes were mentioned. In fact, the HD method was found to have the following ...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 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 …

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 Feb 5, 2009 · 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 and in ... As noted above, the calculated Gibbs energy of reactions of individual REE with atomic hydrogen (Table 1) is strongly negative, thereby predictive of rapid chemical decrepitation of the two-phase Nd-magnet within the temperature range of interest. These reactions can be expected to take place immediately … See moreThe 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) …

The subject of this paper is method (4) together with other aspects of the use of hydrogen in the processing of NdFeB-type magnets. 2. The hydrogen decrepitation process The manufacture of rare earth-transition metal magnets by the HD route was first proposed in a 1978 patent by Harris et al. [7].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.…

Reader Q&A - also see RECOMMENDED ARTICLES & FAQs. Nov 1, 2017 · Fig. 1. Illustration of the Hydrogen Decrep. Possible cause: calcium [12] and hydrogen decrepitation [1,13-19]. Many of these are under current.