Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8156722 | Journal of Magnetism and Magnetic Materials | 2014 | 8 Pages |
Abstract
In this research synthesis of FeCo@C core-shell nanoparticles was done using a novel two step process including the microemulsion technique and alcohol catalytic chemical vapor deposition. X-ray diffraction, transmission electron microscopy, electron beam diffraction and energy dispersive spectroscopy confirm the formation of FeCo@graphite core-shell nanostructure. Compared with FeCo nanoparticles with an oxide shell, the graphite shell restricts the growth of the FeCo nanoparticles, leading to lower saturation magnetization and higher natural-resonance frequency. The electromagnetic characteristics including permittivity, permeability and loss tangents of FeCo nanoparticles/nanoencapsulates were determined in the frequency range of 2-18 GHz. Results show that the graphite coating dramatically improves electromagnetic wave absorption of FeCo nanoparticles due to several dielectric/magnetic loss mechanisms. The main mechanism enhancing the dielectric loss tangent is Deby׳s dual relaxation phenomenon and for magnetic loss is the ferromagnetic resonance. The maximum reflection loss of â40 dB at 2.5 mm thickness and the maximum effective absorption bandwidth (RL<â20 dB) of 5.6 GHz at 3 mm thickness were obtained for FeCo nanoencapsulates.
Keywords
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
S.S.S. Afghahi, A. Shokuhfar,