Preparation of ultrafine jet-milled powders for Nd-Fe-B sintered magnets using hydrogenation–disproportionation–desorption–recombination and hydrogen decrepitation processes

Nakamura, Misato; Matsuura, M.; Tezuka, Nobuki; Sugimoto, Satoshi; Une, Yasuhiro; Kubo, Hirokazu; Sagawa, M.

doi:10.1063/1.4813399

Cited by 44 publications

(19 citation statements)

References 13 publications

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“…1113) A promising combination of HDDR and hydrogen decrepitation has been identified as a fabrication method for ultrafine Nd-Fe-B powders: hydrogen decrepitation and He jet milling was used to obtain ultrafine Nd-Fe-B powders with an average particle size of 0.33 µm from a HDDRtreated Nd-Fe-B alloy. 14) However, the relationship between the HDDR processing parameters and the grain size of the resulting HDDR alloy has not been reported thus far, and the effects of these parameters on the particle size of the ultrafine jet-milled powder obtained when the HDDR alloy is pulverized is not known. In this study, the effects of different HDDR processing parameters on the grain size of the HDDR alloy and the particle size of the jet-milled powder obtained from it were investigated.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Hydrogenation-Disproportionation-Desorption-Recombination Processing Parameters on the Particle Size of Ultrafine Jet-Milled Nd-Fe-B Powders

et al. 2015

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The effects of variations in the hydrogenation-disproportionation-desorption-recombination (HDDR) processing parameters on the size of Nd-Fe-B ultrafine powders were investigated. The ultrafine powders were fabricated by hydrogen decrepitation and jet milling of the HDDR alloys. Before pulverization, the crystal grain size of the HDDR alloys obtained by changing the HD processing temperature (T HD ) varied from 0.27 to 0.55 µm, and decreased as T HD was lowered. The ultrafine powder of the HDDR alloy became finer as T HD decreased, with sizes in the range of 0.33 to 0.58 µm.

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Section: Introductionmentioning

confidence: 99%

“…The coercivity can also be increased by grain refinement of the Nd 2 Fe 14 B phase. 14) Fine Nd-Fe-B powders about 1.1 µm in size have been prepared from strip-cast (SC) Nd-Fe-B alloys by He jet milling.…”

Section: Introductionmentioning

confidence: 99%

Effects of Hydrogenation-Disproportionation-Desorption-Recombination Processing Parameters on the Particle Size of Ultrafine Jet-Milled Nd-Fe-B Powders

et al. 2015

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“…To prepare ultrafine Nd-Fe-B jet-milled powders (<1 µm), development of a Nd-Fe-B alloy consisting of homoge- We have previously reported the fabrication of ultrafine Nd-Fe-B powders with an average particle size of 0.33 µm from HDDR-treated Nd-Fe-B alloy through hydrogen decrepitation and He jet milling. 14) However, no reports have covered the effects of annealing on ultrafine Nd-Fe-B powders. Understanding the effect of annealing on the magnetic properties and morphology of ultrafine Nd-Fe-B powders provides useful information for using these powders in sintering because the sintering conditions strongly depend on particle size.…”

Section: Introductionmentioning

confidence: 99%

“…Addition of Dy increases the coercivity of Nd-Fe-B sintered magnets, but decreases their saturation magnetization and increases their price. Grain refinement of the Nd 2 Fe 14 B phase increases the coercivity of Nd-Fe-B sintered magnets; 14) therefore, preparation of finer Nd-Fe-B powders is needed in order to obtain high coercivity in sintered magnets. Une and Sagawa 57) used He jet milling to prepare fine Nd-Fe-B powders with a particle size of approximately 1.1 µm from strip-cast (SC) Nd-Fe-B alloys.…”

Section: Introductionmentioning

confidence: 99%

Effect of Annealing on Magnetic Properties of Ultrafine Jet-Milled Nd-Fe-B Powders

et al. 2014

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This paper reports the effects of annealing on the magnetic properties of ultrafine Nd-Fe-B powders with an average particle size of 0.67 µm. The powder was fabricated from hydrogenationdisproportionationdesorptionrecombination (HDDR)-treated Nd-Fe-B alloys by hydrogen decrepitation and helium jet milling. The coercivity of the ultrafine powders was slightly increased by annealing below 500°C, and was drastically increased by annealing above 600°C. These two stepwise increases in coercivity were attributed to hydrogen desorption and formation of a liquid Nd-rich phase. In addition, after annealing below 500°C, the coercivity (® 0 H c ) of the ultrafine powder was higher than that of the conventional powder, which was prepared from a strip-cast Nd-Fe-B alloy power with a particle size of 1.12 µm, because of a decrease in particle size. In contrast, after annealing above 600°C, the ® 0 H c of the ultrafine powder was smaller than that of the conventional powder. The rare earth element content (Nd + Pr) was lower in the ultrafine powders than in the conventional powder. These results indicate that the rare earth element content was insufficient in the ultrafine powders.

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“…Nakamura et al fabricated ultra ne Nd-Fe-B powders with an average particle size of 0.33 µm from Nd-Fe-B alloy subjected to hydrogenation-disproportionation-desorption-recombination (HDDR) treatment through hydrogen decrepitation (HD) and He-JM. [6][7][8] They reported that the coercivity of the ultra ne powder was dependent on annealing temperature and that the maximum coercivity of the ultra ne powder was 1210 kA m . Une et al prepared ultra ne-grained Nd-Fe-B sintered magnets and reported a coercivity of around 1034 kA m −1 .…”

Section: Introductionmentioning

confidence: 99%

Improvement of Coercivity of Nd-Fe-B Powder by Nd-Cu Sputtering

et al. 2017

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This paper reports improvement of the coercivity of Nd-Fe-B powder by Nd-Cu sputtering. The total rare earth element content of the Nd-Fe-B powder increased by 0.8 mass% after Nd-Cu sputtering, and the sputtered Nd-Cu was observed at the surface of Nd-Fe-B powder by microstructural observation. The coercivity (H c ) of the Nd-Cu-sputtered Nd-Fe-B powder improved after annealing at temperatures above 600 C, and H c of the sputtered powder reached a maximum value of 1312 kA m −1 after annealing at 900 C. This H c value was 470 kA m higher than that of the compact prepared from powder without sputtering after annealing at 900 C. Microstructure observation showed that the improvement of H c was due to an increase in the Nd-rich phase in the compact by Nd-Cu sputtering.

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Preparation of ultrafine jet-milled powders for Nd-Fe-B sintered magnets using hydrogenation–disproportionation–desorption–recombination and hydrogen decrepitation processes

Cited by 44 publications

References 13 publications

Effects of Hydrogenation-Disproportionation-Desorption-Recombination Processing Parameters on the Particle Size of Ultrafine Jet-Milled Nd-Fe-B Powders

Effects of Hydrogenation-Disproportionation-Desorption-Recombination Processing Parameters on the Particle Size of Ultrafine Jet-Milled Nd-Fe-B Powders

Effect of Annealing on Magnetic Properties of Ultrafine Jet-Milled Nd-Fe-B Powders

Improvement of Coercivity of Nd-Fe-B Powder by Nd-Cu Sputtering

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