Soft magnetic composites (SMCs)
are vital in modern power electronics, including transformers, motors, and
generators, where high permeability, low core loss, and high-frequency
stability are critical. This chapter presents a comprehensive study on the structural
and magnetic performance of FeSi-based and Fe/Fe₃O₄-based SMCs synthesised via
the hot-press sintering technique, focusing on the influence of magnetic
nanoparticle doping on their soft magnetic behaviour.
In Fe–6.5 wt% Si/Fe₂O₃ SMCs, the
incorporation of high-resistivity Fe₂O₃ nanoparticles effectively filled
interparticle gaps and enhanced densification. All samples exhibit excellent
effective permeability frequency stability, ranging from 10 kHz to 100 kHz.
Furthermore, as the Fe2O3 content increased from 0 to 2 wt%, the effective
permeability (μₑ) significantly improved from 22.32 to 30.45 (a 36.4%
increase). Adding Fe2O3 nanopowders from 0–5 wt% also enhanced electrical
resistivity from 29.55 to 50.70 mΩ.cm. This, in turn, decreased the value of Pe
at f = 100 kHz and Bm=10 mT from 6.61 to 4.15 kW/cm3 (a 37.21% reduction),
compared to undoped samples. Furthermore, as Fe2O3 content increases from 0 to
5 wt%, the power loss Pcv of the Fe2O3-doped Fe-6.5Si SMCs decreases from 25.63
kW/m3 to 16.13 kW/m3, a 37.0% reduction.
Similarly, in Fe–6.5 wt% Si/(Fe:
TiO₂) nanocomposites, with increased doping concentration of Fe nanopowder from
0 to 1.66 vol%, both the density and electrical resistivity significantly
increased from 6.72 g/cm³ to 7.11 g/cm³ (up 5.78 %) and from 29. 36 mΩ.cm to
37.16 mΩ.cm, respectively. This can be attributed to reduced interparticle
voids and carrier scattering. The value of saturation magnetisation (Ms)
increased first from 180.89 emu/g to 189.5 emu/g as the Fe NP content increased
from 0 to 1.66 vol%, reaching a maximum value of about 189.5 emu/g for a sample
with 1.66 vol% of Fe nanopowder content. Furthermore, all the composites
exhibit low coercivity (<15 Oe) and excellent effective permeability
frequency stability in the 0-1 MHz range. The eddy current loss at f =100 kHz
and Bm=10 mT is significantly decreased from 50.09 kW/m3 to 8.168 kW/m3
(decreased by 83.69 %) as the Fe nanoparticle content increased from 0 to 1.66
vol%. However, with further increase of Fe nanoparticles from 1.66 vol% to 3.32
vol%, the value of Pe increased from 8.168 kW/m3 to 71.92 kW/m3. Furthermore,
the lowest value of Ph observed in our case for a sample containing 2.49 vol%
of Fe is 0.677 kW/m3.
Furthermore, Fe/Fe₃O₄–Co
composites, developed via surface oxidation and Co nanoparticle doping,
demonstrated superior magnetic performance. The value of Ms is significantly
increased from 207 emu/g to 216 emu/g as Fe (NP) content changed from 0-1 wt%.
The μe measured in the frequency range of 0-2 MHz initially drops first from
97.30 to 61.72 as the content changes from 0 to 1 wt%. However, with the
further increase of Co nano powder content, μe increased, reaching a maximum
value of 237.42 (144 % compared to the sample with 0 wt% of Co NP). Moreover,
the composites also exhibit excellent DC bias performance in the DC bias field
range of 0-110 Oe; the % permeability for all composites is higher than 65.16
%, at 100 kOe, with a peak value of about 72.01. The Co-doped samples also
showed significantly reduced total core loss and enhanced electrical
resistance, which contributed to improved particle bonding and magnetic
coupling. The electrical resistivity increased from 15 mΩ.cm to 55.54 mΩ.cm as
the Co (NP) content changed from 0 to 1 wt%. This in turn reduced Pe from 470
kW/m3 to 396 kW/m3 at f=100 kHz and Bm=10 mT.
The results highlight that
optimal nanopowder doping combined with hot pressing promotes favourable
microstructural evolution, leading to significant enhancement in the magnetic
and electrical properties of Fe-based soft magnetic composites and optimises
the balance between permeability and core loss. This design strategy enables
the development of high-density, low-loss, and frequency-stable Fe-based SMCs,
making them highly suitable for next-generation high-power, high-frequency, and
energy-efficient electronic applications.
Author(s)
Details :-
Muhammad Arif
Department of Applied Physics and Institute of Natural Sciences, Kyung Hee
University, Yongin 17104, Republic of Korea.
Young-Kwang Kim
Technical Research Lab, R-Materials Co. Ltd., Yongin, 17111, Republic of
Korea.
Jong-Soo Rhyee
Department of Applied Physics and Institute of Natural Sciences, Kyung Hee
University, Yongin 17104, Republic of Korea.
Please see the book
here :- https://doi.org/10.9734/bpi/psniad/v4/6648
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