Near theoretical ultra-high magnetic performance of rare-earth nanomagnets via the synergetic combination of calcium-reduction and chemoselective dissolution

Rare earth permanent magnets with superior magnetic performance have been generally synthesized through many chemical methods incorporating calcium thermal reduction. However, a large challenge still exists with regard to the removal of remaining reductants, byproducts, and trace impurities generate...

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Bibliographic Details
Published in:Scientific reports 2018-10, Vol.8 (1), p.15656-11, Article 15656
Main Authors: Lee, Jimin, Hwang, Tae-Yeon, Cho, Hong-Baek, Kim, Jongryoul, Choa, Yong-Ho
Format: Article
Language:English
Subjects:
639/166/898
639/301/357/997
639/301/930/1032
Ammonium chloride
Calcium
Cobalt
Dissolution
Earth
Humanities and Social Sciences
Impurities
Intermediates
Magnetic properties
Magnetism
multidisciplinary
Samarium
Science
Science (multidisciplinary)
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Summary:Rare earth permanent magnets with superior magnetic performance have been generally synthesized through many chemical methods incorporating calcium thermal reduction. However, a large challenge still exists with regard to the removal of remaining reductants, byproducts, and trace impurities generated during the purifying process, which serve as inhibiting intermediates, inducing productivity and purity losses, and a reduction in magnetic properties. Nevertheless, the importance of a post-calciothermic reduction process has never been seriously investigated. Here, we introduce a novel approach for the synthesis of a highly pure samarium-cobalt (Sm-Co) rare earth nanomagnet with near theoretical ultra-high magnetic performance via consecutive calcium-assisted reduction and chemoselective dissolution. The chemoselective dissolution effect of various solution mixtures was evaluated by the purity, surface microstructure, and magnetic characteristics of the Sm-Co. As a result, NH 4 Cl/methanol solution mixture was only capable of selectively rinsing out impurities without damaging Sm-Co. Furthermore, treatment with NH 4 Cl led to substantially improved magnetic properties over 95.5% of the M s for bulk Sm-Co. The mechanisms with regard to the enhanced phase-purity and magnetic performance were fully elucidated based on analytical results and statistical thermodynamics parameters. We further demonstrated the potential application of chemoselective dissolution to other intermetallic magnets.
ISSN:2045-2322
2045-2322
DOI:10.1038/s41598-018-33973-z