Recent developments of rare-earth-free hard-magnetic materials

Li, Da; Pan, Dongmei; Li, ShaoJie; Zhang, ZhiDong

doi:10.1007/s11433-015-5760-x

Cited by 50 publications

(21 citation statements)

References 115 publications

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“…Permanent magnets can provide a high efficiency and reliability for renewable energy technologies, such as wind turbines and hybrid electric vehicles [1]. Rare-earth-free permanent magnets, expected to be the next generation of permanent magnetic materials, have been paid much attention due to abundant resources, low cost, large coercivity and high Curie temperatures [2]. Body-centered tetragonal (bct) α"-Fe 16 N 2 , being an ordered nitride, is one of the most promising candidates for future applications of rare-earth-free permanent magnets because of the excellent magnetocrystalline anisotropy (7.8 × 10 5 J/m 3 ) and the highest saturation magnetization reported so far [3][4][5][6][7][8].…”

Section: Introductionmentioning

confidence: 99%

“…Anisotropic α″-Fe 16 N 2 magnets were prepared by starting from pure bulk Fe with urea as the nitrogen source [ 14 ]. Because of optimal coercivity performance of single-domain nanoparticles, the lower dimensionality of the enhanced hard magnetic properties of magnetic nanostructures has been attractive in the area of hard magnetic nanomaterials [ 2 , 15 , 16 ]. Well-controlled nanostructures of hard magnets are a possible future choice for controlling texture and magnetic alignment to support high-density magnetic storage and giant energy density [ 17 ].…”

Section: Introductionmentioning

confidence: 99%

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Anisotropic Growth and Magnetic Properties of α″-Fe16N2@C Nanocones

Kuang

Men

et al. 2021

Nanomaterials

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α″-Fe16N2 nanomaterials with a shape anisotropy for high coercivity performance are of interest in potential applications such as rare-earth-free permanent magnets, which are difficult to synthesize in situ anisotropic growth. Here, we develop a new and facile one-pot microemulsion method with Fe(CO)5 as the iron source and tetraethylenepentamine (TEPA) as the N/C source at low synthesis temperatures to fabricate carbon-coated tetragonal α″-Fe16N2 nanocones. Magnetocrystalline anisotropy energy is suggested as the driving force for the anisotropic growth of α″-Fe16N2@C nanocones because the easy magnetization direction of tetragonal α″-Fe16N2 nanocrystals is along the c axis. The α″-Fe16N2@C nanocones agglomerate to form a fan-like microstructure, in which the thin ends of nanocones direct to its center, due to the magnetostatic energy. The lengths of α″-Fe16N2@C nanocones are ~200 nm and the diameters vary from ~10 nm on one end to ~40 nm on the other end. Carbon shells with a thickness of 2–3 nm protect α″-Fe16N2 nanocones from oxidation in air atmosphere. The α″-Fe16N2@C nanocones synthesized at 433 K show a room-temperature saturation magnetization of 82.6 emu/g and a coercive force of 320 Oe.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Anisotropic Growth and Magnetic Properties of α″-Fe16N2@C Nanocones

Kuang

Men

et al. 2021

Nanomaterials

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“…The former method is too expensive and the latter one produces flakes with random crystallographic orientation due to the large ductility of MnAl, thus impeding proper orientation of the grains in a magnetic field 13 , 23 – 25 . Consequently, the preparation of powders consisting of regularly shaped single grain particles would be critically important for the success of a high performance anisotropic permanent magnet material 26 .…”

Section: Introductionmentioning

confidence: 99%

Structural, microstructural and magnetic evolution in cryo milled carbon doped MnAl

Fang

Cedervall

Hedlund

et al. 2018

Sci Rep

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The low cost, rare earth free τ-phase of MnAl has high potential to partially replace bonded Nd2Fe14B rare earth permanent magnets. However, the τ-phase is metastable and it is experimentally difficult to obtain powders suitable for the permanent magnet alignment process, which requires the fine powders to have an appropriate microstructure and high τ-phase purity. In this work, a new method to make high purity τ-phase fine powders is presented. A high purity τ-phase Mn0.55Al0.45C0.02 alloy was synthesized by the drop synthesis method. The drop synthesized material was subjected to cryo milling and followed by a flash heating process. The crystal structure and microstructure of the drop synthesized, cryo milled and flash heated samples were studied by X-ray in situ powder diffraction, scanning electron microscopy, X-ray energy dispersive spectroscopy and electron backscatter diffraction. Magnetic properties and magnetic structure of the drop synthesized, cryo milled, flash heated samples were characterized by magnetometry and neutron powder diffraction, respectively. The results reveal that the 2 and 4 hours cryo milled and flash heated samples both exhibit high τ-phase purity and micron-sized round particle shapes. Moreover, the flash heated samples display high saturation magnetization as well as increased coercivity.

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“…Particularly, it shows a positive temperature coefficient for coercivity and magnetic anisotropy which makes it even more interesting for high temperature applications [7,8,9]. It is possible to improve the magnetic moment and also the energy density for MnBi using it as hard magnetic component in combination with a soft magnetic phase in an exchange spring magnet configuration [10].…”

Section: Introductionmentioning

confidence: 99%