Journal of Materials Science: Materials in Electronics (2018) 29:4711–4716
Fabrication and microwave absorption properties of the ﬂaky carbonyl
iron/FeSiAl composite in S-band
· Guozhi Xie
· Ningyan Xie
· Jun Li
· Jiangwei Chen
· Rongqing Xu
· Jing Chen
Received: 22 September 2017 / Accepted: 13 December 2017 / Published online: 3 January 2018
© Springer Science+Business Media, LLC, part of Springer Nature 2018
The ﬂaky carbonyl iron powder (CIP) was prepared by high-energy ball milling, and then the CIP/FeSiAl composites were
obtained with diﬀerent mass ratios by ultrasonic mixing method in this paper. Here, scanning electron microscopy and Fourier
transform infrared spectroscopy were used to demonstrate the microstructure and functional groups of the prepared samples.
The element distribution was detected by energy dispersive spectrometer. The complex permittivity and permeability were
determined by vector network analysis in the frequency range of 1–18 GHz. The reﬂection loss (RL) was calculated accord-
ing to the transmission line theory. The composites exhibit typical ﬂake shapes, which can exceed Snoek limit due to the
enhanced shape anisotropy. The results show that the absorption property of composites can be tuned in S-band by changing
the mass ratio of CIP and FeSiAl. For the composite (mass ratio of 1:4) with the thickness of only 1 mm, the RL reaches
a minimum of − 6.4 dB at 2.3 GHz. Moreover, the absorption bandwidth less than − 5 dB is 2.3 GHz. This study indicates
that the CIP/FeSiAl composites can be potential microwave absorbers in S-band.
With the rapid development of wireless communications
and high-frequency circuit devices, electromagnetic inter-
ference (EMI) has grown to a severe problem to be solved
. Nowadays the application of absorbing material is one
of the most eﬀective means of suppressing EMI . It is well
known that the microwave properties of absorbing materials
depend heavily on the dielectric and magnetic loss. In order
to improve microwave absorption, it is necessary to increase
high permeability values, especially high imaginary parts of
permeability for absorbing materials . As a traditional soft
magnetic material, FeSiAl alloy has been widely employed
in absorbing materials due to its high permeability, high
saturation ﬂux densities and good machinability [2, 4, 5].
However, the high permittivity (> 50 in general) accompa-
nied with a relatively low permeability in FeSiAl alloy is not
conducive to impedance matching [6–8].
For the purpose of obtaining impedance matching, much
work has been conducted on FeSiAl to improve its elec-
tromagnetic property. Surface modiﬁcation was regarded as
an eﬀective way to decrease the permittivity. Zhang et al.
reported they fabricated FeSiAl ﬂakes of good properties
after surface modiﬁcation with nylon . Taghvaei et al. and
Fan et al. used organic and inorganic matter respectively as
a high resistivity layer to coat on particles’ surface [9, 10].
Other researchers found the carbon-based materials had an
excellent absorbing property when mixed with magnetic
absorbents [11, 12]. As a traditional ultraﬁne metal powder
absorber, the carbonyl iron powder (CIP) possesses a high
Curie temperature, the high speciﬁc saturation magnetiza-
tion and the advantage of good temperature stabilization
. Compared with FeSiAl, carbonyl iron has a relatively
lower permittivity (< 30 in general) and permeability .
Increasing electronic devices for special functions in S-band
(2–4 GHz) have attracted much attention, such as local area
network communication, communication satellites and
mobile satellite services [15–17].
In this study, the CIP/FeSiAl composite was fabricated
using a simple two-step process. Flaky CIPs were ini-
tially prepared by ball milling. Furthermore, we ultrasoni-
cally mixed diﬀerent proportions of prepared CIP and raw
FeSiAl alloy to synthesize composite absorbing materials.
The microstructure and microwave properties of composites
* Guozhi Xie
College of Electronic and Optical Engineering &
College of Microelectronics, Nanjing University
of Posts and Telecommunications, Nanjing 210023,
People’s Republic of China