Sm–Fe–N bulk magnets produced by compression shearing method

Saito, Tetsuji; Fukui, Masato; Takeishi, Hiroyuku

doi:10.1016/j.scriptamat.2005.07.025

Cited by 35 publications

(13 citation statements)

References 11 publications

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“…[1][2][3] It has been argued that bulk Sm-Fe-N magnets cannot be produced because of the thermal decomposition, but this drawback is being overcome according to recent research activity. [4][5][6][7] On the other hand, many researchers have been striving to improve the coercivity of the ingredient powder for producing bulk magnets by refining particle size. 3,[8][9][10][11][12] Several researchers however demonstrated that overnitridation of relatively coarse powder (∼ 60 µm) of Sm 2 (FeMn) 17 N x magnets (x > 3) introduces a unique microstructure that is composed of nanocrystalline cells (= below 100 nm) surrounded by amorphous cell walls into formerly monocrystalline powder, making it possible to achieve quite high coercivity (∼12 kOe) without reducing the particle size.…”

Section: Introductionmentioning

confidence: 99%

Multi-scale electron microscopy of overnitrided Sm-Fe-Mn-N powder

Hosokawa

Takagi

2018

AIP Advances

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Multi-scale electron microscopy technique that combines transmission electron microscopy (TEM) and focused ion beam - scanning electron microscopy (FIB-SEM) was utilized to investigate the influences of the change in microstructure of Sm2(Fe0.95Mn0.05)17Nx by overnitridation on the magnetic properties. The recent high-contrast backscatter electron imaging technique in SEM machines enabled us to reveal the formation events of cell-like microstructure from a quite large field of view. In addition, detailed TEM observations revealed the crystallographic orientations of the cells as well as the local chemical fluctuation. The combination of these techniques allows us to understand the microstructural hierarchy in this material, verifying that the original orientations of the individual particles are inherited to the nanocrystalline cells formed by overnitridation.

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Section: Introductionmentioning

confidence: 99%

Multi-scale electron microscopy of overnitrided Sm-Fe-Mn-N powder

Hosokawa

Takagi

2018

AIP Advances

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“…These methods utilize explosive energy or extremely high strain deformation and can yield a magnet with a relatively high density. 5,6) However, such methods afford low yield and are expensive.…”

Section: Introductionmentioning

confidence: 99%

Correlation between Microstructure and Magnetic Properties in Sm2Fe17N3 Magnet Prepared by Pulsed Current Sintering

et al. 2012

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The consolidation of Sm 2 Fe 17 N 3 powder was examined by pulsed current sintering below its decomposition temperature. Although decomposition of the powder was not observed, its coercivity decreased dramatically. Annealed powder was observed by transmission electron microscopy in order to clarify the mechanism for the reduction in the coercivity. In powder annealed at 673 K, a thin nanostructured layer was formed around the Sm 2 Fe 17 N 3 particles. The crystal structure of this thin layer had a crystallographic symmetry higher than that of the Sm 2 Fe 17 N 3 structure. This higher symmetry layer appeared to have a smaller magnetic anisotropic energy, allowing it to act as a nucleation site for a reverse magnetic domain, when a reverse magnetic field is applied to the magnetized powder. Therefore, the coercivity of the powder decreased below its decomposition temperature. Irregular growth of the thin layer was observed in powder annealed above the decomposition temperature, and the grown region was confirmed to be an iron phase.

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“…A recently developed consolidation technique, called compression shearing, can consolidate powders into bulk form at room temperature by the application of shear stress to them [12,13].…”

Section: Introductionmentioning

confidence: 99%