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研究活動

Fabrication of Cr diffused Sm2Fe17Nx core-shell powder by reduction diffusion process

The 25th International Workshop on Rare-Earth and Future Permanent Magnets and theirApplications (REPM2018),2018.8.26-30, Beijing,China

2018年8月28日(火)

Ruka Matsuda, Keisuke Yarimizu, Masashi Matsuura, Nobuki Tezuka, Satoshi Sugimoto (TohokuUniversity),Takashi Ishikawa, Yukinobu Yoneyama (Sumiko Kunitomi Denshi, Co. Ltd.)

Abstract

As Sm2Fe17Nx compound shows high saturation magnetization (Js), anisotropy field (HA) and Curietemperature (Tc), Sm-Fe-N magnet powder is expected as a high performance bonded magnet powder.However, the Sm2Fe17Nx compound decomposes into SmN and α-Fe at temperatures above 600 oC, andhigh heat resistance is needed for expanding its high temperature use such as bonded magnets for vehicles. Inour previous study [1], Cr addition is effective for increase of the decomposition temperature more than 100oC. However, the Js of Sm2(Fe, Cr)17Nx is lower than that of Sm2Fe17Nx. Therefore, in this study, weinvestigated the possibility for the fabrication of Sm2Fe17Nx/ Sm2(Fe, Cr)17Nx core-shell powders, in whichSm2Fe17Nx is core and Sm2(Fe, Cr)17Nx is shell, for achieving both high Js and high heat resistance. We alsoinvestigated their magnetic properties and heat resistance. Sm2Fe17Nx/ Sm2(Fe, Cr)17Nx core-shellpowders were fabricated using a modified reduction diffusion (RD) method. Sm2Fe17 powders were mixed withCr oxide powders and then reduced using Ca powder at temperatures above 800 oC. After nitriding at 400-500 oC, the Ca-reduced materials were washed. Magnetic properties were measured by VSM andmicrostructure were observed by XRD and SEM-EDX. Figure 1 shows cross-sectional BSE image andcorresponded Cr mapping image taken from a Sm-Fe-Cr-N obtained powder. It suggests that Cr condensesnear the surface of the powder. XRD also revealed that the powder consisted of Th2Zn17 phase. Therefore, itis considered that Sm2Fe17Nx/ Sm2(Fe, Cr)17Nx core-shell powders were obtained. The core-shell powdershowed intermediate magnetic properties between Sm2Fe17Nx and Sm2(Fe, Cr)17Nx powders.

その他特記事項

This study is partially supported by the Elemental Strategy Initiative Center forMagnetic Materials (ESICMM) under the outsourcing project of MEXT, JAPAN.


研究活動

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

触媒・電池元素戦略拠点
触媒・電池元素戦略研究拠点 (京都大学)
東工大元素戦略拠点
東工大元素戦略拠点 (東京工業大学)
構造材料元素戦略研究拠点
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