Annealing effect on microstructure and magnetic properties of flake-shaped agglomerates of Ni–20wt%Fe nanopowder

•A new concept of flake-shaped Ni–20wt%Fe nanopowder agglomerate was investigated.•The porous nanopowder agglomerates were easily deformed into flake shape by milling.•Microstructure changes during annealing improved the soft magnetic property.•The flake agglomerate will provide unique loss-properti...

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Bibliographic Details
Published in:Journal of alloys and compounds 2014-11, Vol.613, p.164-169
Main Authors: Lee, Geon-Yong, Kwon, Sang-Kyun, Lee, Jai-Sung
Format: Article
Language:English
Subjects:
Agglomerates
Anisotropy
Annealing
Coercive force
Condensed matter: electronic structure, electrical, magnetic, and optical properties
Cross-disciplinary physics: materials science
rheology
Crystallites
Exact sciences and technology
Flake-milling
Magnetic properties
Magnetic properties and materials
Magnetic properties of nanostructures
Magnetic property
Materials science
Microstructure
Nanopowders
Nanoscale materials and structures: fabrication and characterization
Nanostructure
Nickel
Ni–Fe nanopowder
Physics
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Summary:•A new concept of flake-shaped Ni–20wt%Fe nanopowder agglomerate was investigated.•The porous nanopowder agglomerates were easily deformed into flake shape by milling.•Microstructure changes during annealing improved the soft magnetic property.•The flake agglomerate will provide unique loss-properties of magnetic and dielectric. The present study has been performed to develop a flake-shaped Ni–20wt%Fe magnetic nanopowder agglomerate for the application of electromagnetic absorption media in a high frequency range. The spherical agglomerates with 10μm in diameter consisting of 30nm nanoparticles were deformed into thin plate-like powders of 1μm in thickness by milling and then annealed at various temperatures. The structural analysis revealed that with elevating annealing temperature the crystallite size was increased by sintering effect. In magnetic properties, the saturation magnetization was not changed regardless of milling and annealing conditions. On the other hand, the milling treatment induced nanopowder agglomerates to have shape anisotropy. The coercivity was increased due to the generation of internal stress but it vanished by annealing. It is concluded that the flake-shaped nanopowder agglomerates can be easily magnetized and demagnetized to incident magnetic wave by post annealing treatment.
ISSN:0925-8388
1873-4669
DOI:10.1016/j.jallcom.2014.06.019