Novel powder processing technologies for production of rare-earth permanent magnets

Takagi, Kenta; Hirayama, Yusuke; Okada, Shusuke; Yamaguchi, Wataru; Ozaki, Kimihiro

doi:10.1080/14686996.2021.1875791

Cited by 17 publications

(13 citation statements)

References 54 publications

(52 reference statements)

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“…Fig. 5 shows the relationship between the particle size and coercivity of the Sm 2 Fe 17 N 3 powder (Hirayama Y. et al, 2016;Okada S. et al, 2017;Dong Y. et al, 2019;Tada S. et al, 2012;Takagi K. et al, 2021). Okada et al revealed that Sm 2 Fe 17 N 3 fine powder synthesized by the R-D method exhibited high coercivity even at the submicron size, unlike powders prepared by milling.…”

Section: Chemical Synthesismentioning

confidence: 99%

“…Okada et al revealed that Sm 2 Fe 17 N 3 fine powder synthesized by the R-D method exhibited high coercivity even at the submicron size, unlike powders prepared by milling. In particular, they reported that Sm 2 Fe 17 N 3 with a giant coercive force of 2.5 MA/m and an average particle diameter of about 400 nm can be produced by improving various processing steps Okada S. et al, 2017;Takagi K. et al, 2021). They employed a synthesis process in which Sm-Fe oxide powders synthesized by coprecipitation were subjected to hydrogen reduction, reduction-diffusion and nitridation.…”

Section: Chemical Synthesismentioning

confidence: 99%

“…Vapor phase methods are able to synthesize ultrafine particles much smaller than those prepared by the breakdown methods described in Section 2.1.1, and these ultrafine particles are also extremely pure, as they Hirayama ( 2016) Okada ( 2017) Okada ( 2019) Tada ( 2012) Takagi ( 2021) Dong (2019) Fig. 5 Particle size dependency of coercivity of Sm 2 Fe 17 N 3 powder (Hirayama Y. et al, 2016;Okada S. et al, 2017;Dong Y. et al, 2019;Tada S. et al, 2012;Takagi K. et al, 2021).…”

Section: Physical Synthesismentioning

confidence: 99%

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Recent Research Trend in Powder Process Technology for High-Performance Rare-Earth Permanent Magnets

Takagi

Hirayama

Okada

et al. 2023

KONA

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Higher performance is constantly required in rare earth permanent magnets, which are an indispensable component of the motors of electric vehicles. When producing sintered magnets, advanced structural control is necessary in the powder metallurgy process in order to achieve high performance. Especially in recent years, it has become important to develop processes for Sm-Fe-N magnets and metastable phase magnets as next-generation magnets to replace the Nd-Fe-B magnets. Because the crystal grain refinement of sintered magnets is most effective for improving coercivity, production methods for raw powders have evolved from the traditional pulverization to chemical synthesis approaches, and as a result, a submicron-sized Sm-Fe-N powder with huge coercivity has been developed. State-ofthe-art physical synthesis methods have also been applied successfully to the synthesis of nanopowders. Since control of the grain boundary is very effective in Nd-Fe-B magnets, this approach has also been evolved to Sm-Fe-N magnets by nano coating. On the other hand, since technologies for crystalline orientation control and high-density sintering are indispensable for improvement of remanence, new low-thermal load consolidation techniques such as spark plasma sintering are being developed for Sm-Fe-N magnets and metastable phase magnets in order to overcome the inherent low thermal stability of these materials.

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Section: Chemical Synthesismentioning

confidence: 99%

Section: Chemical Synthesismentioning

confidence: 99%

Section: Physical Synthesismentioning

confidence: 99%

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Recent Research Trend in Powder Process Technology for High-Performance Rare-Earth Permanent Magnets

Takagi

Hirayama

Okada

et al. 2023

KONA

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“…Finally, MD calculation and radial distribution function (RDF) analysis [22] were carried out to reveal the relationship between the RDF and the coordination number of each component in the solution. The average coordination number of each component was calculated by Equation (1).…”

Section: Mechanism Of Maintaining the Metastable State By Naclmentioning

confidence: 99%

“…Rare earths are strategic metal resources that are used in a wide range of industries. For example, they can be found in the development of high-tech advanced materials for permanent magnets, luminescence, catalysis and hydrogen storage, as well as in basic industries such as metallurgy, machinery and petrochemicals in general [1][2][3][4][5].…”

Section: Introductionmentioning

confidence: 99%

Maintenance of the Metastable State and Induced Precipitation of Dissolved Neodymium (III) in an Na2CO3 Solution

Yang

Zhang

et al. 2021

Minerals

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Rare earths dissolved in carbonate solutions exhibit a metastable state. During the period of metastability, rare earths dissolve stably without precipitation. In this paper, neodymium was chosen as a representative rare earth element. The effects of additional NaCl and CO2 on the metastable state were investigated. The metastable state can be controlled by adding NaCl to the Na2CO3 solution. Molecular dynamics studies indicated that the Cl− provided by the additional NaCl partially occupied the coordination layer of Nd3+, causing the delayed formation of neodymium carbonate precipitation. In addition, the additional NaCl decreased the concentration of free carbonate in the solution, thereby reducing the behavior of free contact between carbonate and Nd, as well as resulting in the delay of Nd precipitate formation. Consequently, the period of the metastable state was prolonged in the case of introduction of NaCl. However, changing the solution environment by introducing CO2 can destroy the metastable state rapidly. Introduction of CO2 gas significantly decreased the CO32− content in the solution and increased its activity, resulting in an increase of the free CO32− concentration of the solution in the opposite direction. As a result, the precipitation process was accelerated and the metastable state was destroyed. It was possible to obtain a large amount of rare earth carbonate precipitation in a short term by introducing CO2 into the solution with dissolved rare earths in the metastable state to achieve rapid separation of rare earths without introducing other precipitants during the process.

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Development of Flexible Rare Earth–Fe–B Rubber Magnets toward Efficient Utilization of Ce, La, and Y Elements

Zhou,

Huang,

Fan

et al. 2023

Adv Eng Mater

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The microstructure, magnetic properties, corrosion and aging resistance, and mechanical properties of Nd‐Fe‐B, (Nd,La,Ce)‐Fe‐B, and (Ce,La,Y)‐Fe‐B rubber magnets have been investigated. For Nd‐Fe‐B magnets, increasing particle size and filling ratio of magnetic particles not only improves the overall magnetic properties but also increases the tensile strength. Using the Nd26.4Fe67.6Co5B powder with particle size of 75∽106 μm and filling ratio of 90%, the optimum magnetic properties with the coercivity Hcj = 738.2 kA/m, remanence Jr = 0.51 T, and maximum energy product (BH)max = 43.5 kJ/m3 were obtained. The magnet also exhibited an enhanced tensile strength of 4.52 MPa owing to its compact and uniform microstructure. In addition, the magnetic properties of Hcj = 518 kA/m, Jr = 0.34 T, and (BH)max = 20.6 kJ/m3 were obtained in the partial high‐abundance (Nd,La,Ce)‐Fe‐B rubber magnet, which is superior to some of commercial Nd‐Fe‐B rubber magnets. For full high‐abundance (Ce,La,Y)‐Fe‐B magnet, these values are 320 kA/m, 0.27 T, and 10.5 kJ/m3, respectively. Despite its lower magnetic properties than Nd‐based rubber magnets, (Ce,La,Y)‐Fe‐B rubber magnet exhibits competitive advantage over the Nd‐containing magnets in terms of corrosion resistance and aging resistance performance. Moreover, (Ce,La,Y)‐Fe‐B magnet shows a tensile strength of 7.86 MPa, which is nearly 74.2 % and 56.8 % higher than the Nd‐Fe‐B and (Nd,La,Ce)‐Fe‐B rubber magnets. The present results indicate that the Ce, La and Y elements can be reasonably selected to manufacture flexible RE‐Fe‐B rubber magnets with high performance/cost ratio and good performance stability.This article is protected by copyright. All rights reserved.

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Novel powder processing technologies for production of rare-earth permanent magnets

Abstract: Ozaki (2021): Novel powder processing technologies for production of rareearth permanent magnets, Science and Technology of Advanced Materials,

Cited by 17 publications

References 54 publications

Recent Research Trend in Powder Process Technology for High-Performance Rare-Earth Permanent Magnets

Recent Research Trend in Powder Process Technology for High-Performance Rare-Earth Permanent Magnets

Maintenance of the Metastable State and Induced Precipitation of Dissolved Neodymium (III) in an Na2CO3 Solution

Development of Flexible Rare Earth–Fe–B Rubber Magnets toward Efficient Utilization of Ce, La, and Y Elements

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