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Recent Topics of Permanent Magnet Researches in Japan

12th International Conference on Ferrites (ICF 12)

2019年10月31日(木)

Satoshi Sugimoto (Tohoku Univerisity)

Abstract

 Permanent magnets are widely used in many applications such as motors in hybrid electric vehicles (HEV) and electric vehicles (EV). In this talk, recent progress of techniques for obtaining high coercive Nd-Fe-B magnets and researches for aiming to develop new-type magnets in Japan, will be introduced.
Interfacial microstructure controls such as grain boundary diffusion (GBD) process and grain refinement are established methods for increasing coercivity of Nd-Fe-B sintered magnets. We decreased the size of jet-milled powder to around 1 m by He jet-milling (He-JM) in Dy-free Nd-Fe-B sintered magnets and obtained high coercivity (0HcJ) with high (BH)max. We also succeeded further decrease in the size to 0.3 m, which is comparable to the single domain particle size of Nd2Fe14B, by combining HDDR, hydrogen decrepitation (HD) and He-JM. In addition, GBD process was found as a good method for increasing coercivity of the powders. On the other hand, much attention has been paid to Nd-Fe-B hot deformed magnets because of their small grain size and high temperature coefficient of coercivity. Very recently, heavy rare-earth-free Nd-Fe-B hot deformed magnets were adopted to the motors of HEV in Japan.
No bulk new permanent magnet, which shows higher magnetic properties than Nd-Fe-B magnets, has been found. However, iron-rich compounds with the tetragonal ThMn12-type structure, which were prepared using thin film techniques and decrease in the amount of stabilizing elements such as Ti and V, have been refocused because of their potential to meet current demands for rare-earth-lean permanent magnets with high energy density. Sm-Fe-N magnets using Sm2Fe17Nx compound has been used in bonded magnets because of its high saturation magnetization, large anisotropy field, and high Curie temperature. Recently, we improved magnetic properties of Zn-bonded Sm-Fe-N magnets by using fine powders with low oxygen.

その他特記事項

This work was partially supported by the Future Pioneering Program “Development of magnetic material technology for high-efficiency motors” commissioned by the New Energy and Industrial Technology Development Organization (NEDO), the Elements Strategy Initiative Center for Magnetic Materials (ESICMM) under the outsourcing project of the Ministry of Education, Culture, Sports, Science and Technology (MEXT)


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文部科学省

文部科学省
元素戦略プロジェクト(活動紹介)
NIMS磁石パートナーシップ

元素戦略拠点

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触媒・電池元素戦略研究拠点 (京都大学)
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東工大元素戦略拠点 (東京工業大学)
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構造材料元素戦略研究拠点 (京都大学)
高効率モーター用磁性材料技術研究組合
高効率モーター用 磁性材料技術研究組合