Electromagnetic wave absorbing properties of SiC/SiO2 composites with ordered inter-filled structure

Article abstract of DOI:10.1016/j.jallcom.2016.03.309

Silicon carbide/silica (SiC/SiO₂) monoliths with ordered inter-filled structure were prepared via nanocasting and cold-pressing, using polycarbosilane as precursor and ordered mesoporous silica SBA-15 as template. The SiC grains were incorporated, in form of ordered rodlike arrays, into nanochannels of SBA-15. Their electromagnetic (EM) wave absorbing properties were investigated in X-band, in which SiC acted as EM wave absorber and SiO₂ as transparent matrix. The results indicated that the composites had good EM absorbing properties due to the enhanced dielectric loss resulting from their intrinsic physical properties and special structures. The optimal absorbing properties were determined by impedance match and quarter-wavelength law.

Full text of DOI:10.1016/j.jallcom.2016.03.309

Journal of Alloys and Compounds 680 (2016) 604e611
Contents lists available at ScienceDirect
Journal of Alloys and Compounds
journal homepage: http://www.elsevier.com/locate/jalcom
Electromagnetic wave absorbing properties of SiC/SiO composites
2
with ordered inter-filled structure
Xiaoyan Yuan , Laifei Cheng , Litong Zhang a
b
a, *
a
State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi’an 710072, China
School of Materials Science and Engineering, Shaanxi University of Science and Technology, Xi’an 710021, China
b
a r t i c l e i n f o
a b s t r a c t
Article history:
Received 18 December 2015
Received in revised form
Silicon carbide/silica (SiC/SiO ) monoliths with ordered inter-filled structure were prepared via nano-
casting and cold-pressing, using polycarbosilane as precursor and ordered mesoporous silica SBA-15 as
template. The SiC grains were incorporated, in form of ordered rodlike arrays, into nanochannels of SBA-
2
14 March 2016
15. Their electromagnetic (EM) wave absorbing properties were investigated in X-band, in which SiC
Accepted 17 March 2016
Available online 21 April 2016
acted as EM wave absorber and SiO as transparent matrix. The results indicated that the composites had
2
good EM absorbing properties due to the enhanced dielectric loss resulting from their intrinsic physical
properties and special structures. The optimal absorbing properties were determined by impedance
match and quarter-wavelength law.
Keywords:
SiC/SiO composites
2
Ordered inter-filled structure
©
2016 Elsevier B.V. All rights reserved.
Electromagnetic wave absorption
1. Introduction
ordered mesostructural C/SBA-15 composites as promising EM
wave absorbing materials [19,20]. He et al. synthesized the meso-
With the rapid developments of wireless communications and
microwave circuits in gigahertz (GHz) range, serious electromag-
netic (EM) interference problems have emerged and harmed to the
equipments and biological systems [1e4]. At present, radar stealth
technology is one of the commanding heights in the military
strategy, and the radar monitor frequency focuses on X-band
2
structure FeeC/SiO nanocomposites with an enhanced microwave
absorbing properties [21]. Above that indicated the ordered inter-
filled mesostructure could reflect and scatter the incident EM
wave many times and then the EM energy could be completely
absorbed in the confined space [22,23]. Meanwhile, these com-
posites had an effective three-dimensional (3D) conductive inter-
connection structure, which was conducive to attenuate the EM
wave energy [19]. Besides that, the chemical composition of the
inter-filled materials was easily modulated to obtain the hybrid
composites. Inspired by above results, the composite of the SiC
nanoparticles full-filled the nanochannels of SBA-15 will be a good
EM wave absorbing material.
(
8.2e12.4 GHz). Therefore, considerable attentions have been
aroused and devoted to the EM wave absorbing materials with
lightweight and strong absorption at X-band [5e9]. SiC nano-
materials and SiC-based composites, such as SiC nanowires [10],
yttria-stabilized zirconia/SiC [11], NeSiC [5], NiOeSiC [12], SiC/
CNTs [13,14], vitrified bonded SiC [15], SiCf/SiC [7] and SiC-based
ceramic woven fabrics [16], had been reported as the good EM
wave absorbing materials, which was because of their excellent
chemical stability, good thermal stability and semiconducting
properties.
On the other hand, Shi et al. [24] and our group [25] had
respectively synthesized the SiC powder and monolith with high
ordered mesoporous structure, using PCS as preceramic precursor
and the SBA-15 as a start template. These reports indicated that PCS
In recent years, ordered mesoporous SBA-15 has been widely
used as hard-template and EM wave transparent matrix due to
their high ordered structure, good pore-connectivity, good thermal
stability and low dielectric constant [17,18]. Liu’s group reported the
2
had a good ability to fill into the nanochannels of SiO templates.
Meanwhile, the PCS-silica powders can easily press into any
monoliths without any binder [25,26]. After nanocasting and sin-
2
tering, the SiC/SiO composites had the ordered inter-filled meso-
porous structure, which can effectively attenuate EM wave energy.
Therefore, our article presents a competitive and important work.
2
In present work, the SiC/SiO monolithic composites with or-
dered mesoporous inter-filled structure were prepared by a simple
synthesis route. The influences of the microstructures on EM wave
*
Corresponding author.
E-mail addresses: xiaoyanyuan0519@163.com (X. Yuan), chenglf@nwpu.edu.cn
(
L. Cheng).
http://dx.doi.org/10.1016/j.jallcom.2016.03.309
925-8388/© 2016 Elsevier B.V. All rights reserved.
0

X. Yuan et al. / Journal of Alloys and Compounds 680 (2016) 604e611
605
an onyx mortar and sieving with the 300 mesh sieve. Subsequently,
the powders were equally divided into four parts and each was
added into a stainless steel mould to cold-press into a cuboids
monolith under a pressure of 10.0 MPa for 2.0 min. Finally, the
2
polymer/SiO monolith was transferred into a horizontal ceramic
tube furnace and subjected to the thermal treatment in Ar atmo-
ꢀ
sphere at x C (x ¼ 1200, 1300, 1400 or 1500) for 2 h with a heating
ꢀ
ꢁ1
2
rate of 1 C min , to generate SiC/SiO monolithic ceramic. The
monoliths pyrolyzed at different temperatures were denoted as
SiC/SiO -1200, SiC/SiO -1300, SiC/SiO -1400 and SiC/SiO -1500,
respectively.
2
2
2
2
2.3. Characterization
2
Scheme 1. Schematic illustration of the ordered inter-filled SiC/SiO composite.
Powder small-angle X-ray diffraction (SA-XRD) and wide-angle
X-ray diffraction (WA-XRD) patterns were achieved using a Philipps
X’Pert PRO X-ray diffraction system (Cu K radiation, 0.15406 nm).
a
absorption performances were investigated at X-band. The results
clearly indicated that the combination of the specific structure and
high crystallinity SiC can be contributed to an enhanced microwave
absorption property. To find the optimal reflection loss (RL) and
matching thickness, the quarter-wavelength thicknesses and
impedance match degree plots were constructed and the relevant
loss mechanisms were proposed herein.
The surface morphology was investigated by a field emission
scanning electron microscope (FE-SEM, S4700). Transmission
electron microscopy (TEM) measurement was conducted on a FEI
T20 microscope operated at 200 kV. Nitrogen adsorption-
desorption isotherm measurements were performed on a Micro-
ꢀ
metitics ASAP 2020 volumetric adsorption analyzer at ꢁ196 C. The
mechanical compressive strength of the monoliths was evaluated
using a universal tensile testing machine (SHIMADZU Universal
Testing Machine AGS-X 5kN) at room temperature. Direct current
2
. Experimental details
(
DC) conductivity was performed with a standard two lines method
2
.1. Chemicals
using the DC Source (Precise Current Source by Keithley, 6220,
USA). The dielectric properties were measured by a vector network
analyzer (VNA, MS4644A, Anritsu, Atsugi, Japan) in X-band
Triblock poly(ethylene oxide)-b-poly(propylene oxide)-b-
poly(ethylene oxide) copolymer Pluronic P123 (M
EO20PO70EO20) was purchased from Sigma-Aldrich. Polycarbosilane
PCS) was obtained from lab of ceramic fiber and composites, Na-
w
¼ 5800,
(8.2e12.4 GHz) using the wave-guide method. The as-prepared
sample was placed vertically in the center of test chamber during
measurement.
(
tional University of Defense Technology, China. Others chemicals
were purchased from Shanghai Reagents Co., Ltd. All chemicals
were used as received state without any further purification. High-
purity argon (99.99%) was used in their as-received state during the
ceramic preparation.
3
. Results and discussion
3
.1. Morphology and microstructure
The synthetic approach for the ordered mesoporous inter-filled
2.2. Synthesis of mesoporous SBA-15 and SiC/SiO
2
monolithic
2
SiC/SiO monoliths was shown in Scheme 1. The microsturctures of
composites
the SBA-15 were shown in Fig. S1 in the SI. The SBA-15 exhibited 2-
D P6mm hexagonal symmetry with a specific surface area of
2
ꢁ1
and an average pore diameter of 8.9 nm (shown in
Mesoporous silica SBA-15 was prepared by hydrothermal syn-
thesis method according to established procedures [17], using P123
as structure directing agent and TEOS as a precursor. A detailed
explanation on the synthesis and characterization of the meso-
porous SBA-15 were given in the Support Information (SI).
573 m
g
Table 1). These results indicated that the SBA-15 had good ordered
mesoporous structure, high specific surface area and narrow pore-
size distribution.
The typical cross-section SEM images of SiC/SiO
were shown in Fig. 1. The samples of SiC/SiO -1200, SiC/SiO
and SiC/SiO -1400 all exhibited interconnected particles with a
uniform size of about 1.0 m (shown in Fig. 1aec). The morphol-
2
monoliths
The SiC/SiO
2
monoliths were synthesized by a combined process
2
2
-1300
of nanocasting and cold-pressing. A flow chart of the synthesis
2
procedure was shown in Scheme 1. In a typical process, 4.0 g of SBA-
m
ꢀ
1
5 was placed in a flask, dried at 150 C under a vacuum for 4.0 h
ogies of these monoliths were similar to that of the SBA-15, which
and cooled down to room temperature (RT), and then added in the
solution of 5.0 g PCS and 45.0 ml THF to stir for 6.0 h. After that, the
THF solvent was removed under vacuum to generate a powdery
mixture. The fine powdery mixtures were obtained by grinding in
confirmed that the SiC grains were restricted into channels of the
SBA-15 [25,27]. When the calcination temperature was 1500 C, the
as-prepared composite was constructed from unconnected parti-
cles (shown in Fig. 1d). Meanwhile, there were many big pores in
ꢀ
Table 1
Textural data of the samples.
BET (m2
g
ꢁ1
)
Pore volume (cm3
g )
ꢁ1
Pore size (nm)
Compression strength (MPa, RT)
Sample
SBA-15
S
573.0
25.3
38.5
60.7
15.6
1.0
e
8.9
e
e
SiC/SiO
SiC/SiO
SiC/SiO
SiC/SiO
2
-1200
-1300
-1400
-1500
43.8
52.0
68.5
39.2
2
2
2
0.1
0.13
e
3.8
4.0
e

606
X. Yuan et al. / Journal of Alloys and Compounds 680 (2016) 604e611
Fig. 1. Cross-section SEM images of the SiC/SiO
2
-1200 (a), SiC/SiO
2 2 2
-1300 (b), SiC/SiO -1400 (c) and SiC/SiO -1500 (d), respectively.
ꢀ
the composite. The possible reason was the template SiO
with free carbon from PCS pyrolysis at 1500 C to produce and then
2
reacted
at 1500 C to cause the ordered structure collapse. Therefore, the
ꢀ
ordered mesoporous inter-filled structure was also destroyed at
ꢀ
escape some small-molecule gases, such as SiO, CO, CO
2
and so on,
1500 C.
to form these macropores. Meanwhile, the SiC crystals were growth
Evidence of the maintenance of ordered mesoporous inter-filled
2 2 2 2
Fig. 2. TEM images of the SiC/SiO -1200 (a), SiC/SiO -1300 (b), SiC/SiO -1400 (c) and SiC/SiO -1500 (d), respectively. The inset in (c) is the corresponding HR-TEM image.

X. Yuan et al. / Journal of Alloys and Compounds 680 (2016) 604e611
607
[
1
24,25]. As shown in Fig. 2d, the ordered structure was destroyed at
500 C, which was consisted with that of the SEM. Therefore,
SiC/SiO2-1200
SiC/SiO2-1300
SiC/SiO2-1400
SiC/SiO2-1500
(111)
ꢀ
through the polymer-to-ceramic conversion process and the
calcination temperature less than 1500 C, the ordered mesoporous
ꢀ
inter-filled arrays can be conserved for SiC/SiO
composites.
2
monolithic
SiO2
(220)
(311)
Fig. 3 showed the typical WA-XRD patterns of the SiC/SiO
2
composites. It was clear to see that the crystallinity of the as-
prepared composites increased with the increasing calcination
temperature. The diffraction peaks in each pattern were indexed to
the
b-SiC according to the JCPDS 01-1119. Using Scherrer’s formula,
the SiC grain sizes were estimated to be 0.4, 4.2, 6.3 and 18.4 nm for
SiC/SiO
2
-1200, SiC/SiO
2
-1300, SiC/SiO
2
-1400 and SiC/SiO
2
-1500.
ꢀ
We can see that the size of SiC crystals at 1500 C were clearly
bigger than the channels size of SBA-15, as a further evidence for
20
40
60
80
2
Theta (degrees)
the disordered structure of SiC/SiO
at 21e23 existed in each pattern was related with SiO
2
-1500. Moreover, a broad band
ꢀ
Fig. 3. WA-XRD patterns of the SiC/SiO
2
composites.
2
suggesting
its amorphous nature.
Nitrogen isotherms adsorption-desorption isotherms and pore-
structure for the SiC/SiO
ages. As shown in Fig. 2aec, the composites of SiC/SiO
SiO -1300 and SiC/SiO -1400 exhibited characteristic cylindrically
rod-like arrays in large domains, as evident in the inset of high-
resolution TEM (HT-TEM) image of SiC/SiO -1400 shown in
Fig. 2c. The inter-filled SiC nanoparticles and SiO matrix were in
2
samples was also provided by TEM im-
size distributions of the SiC/SiO composites were shown in the SI.
2
2
-1200, SiC/
From Fig. S2a, the isotherms of SiC/SiO -1200 and SiC/SiO -1500
2
2
2
2
didn’t show the hysteretic loop characteristic in each curve, which
was due to the amorphous SiC were fully filled mesopores of the
2
SBA-15 for SiC/SiO -1200 and the mesostructure totally damaged at
2
2
high temperature for SiC/SiO -1500. Their corresponding pore size
2
tight contact with each other and no cavities. These results indi-
cated that the nanochannels of the SBA-15 were almost filled by SiC
grains, which had been proved that the ordered mesoporous SiC
distributions also proved the above results. However, a relatively
obvious hysteretic loop was exhibited in the each isotherm of the
SiC/SiO -1300 and SiC/SiO -1400. Base on models of pore-filling
2
2
powder and monolith were obtained after removing the SiO
2
mechanisms [28], the above phenomenon indicated SiC
2
Fig. 4. The real (a) and imaginary parts (b) of complex permittivity, the dielectric loss (c) and the complex permeability (d) as a function of frequency for the SiC/SiO composites.

608
X. Yuan et al. / Journal of Alloys and Compounds 680 (2016) 604e611
2
Fig. 5. The DC conductivity (a), absorption coefficients (b) and schematic diagram representing the EM wave attenuate mechanisms (c) for the SiC/SiO composites.
0
0
0
nanocrystals filled inside nanochannels of the SBA-15. The specific
BET surface areas and average pore sizes of the SiC/SiO composites
were shown in Table 1. Although the equal PCS inter-filled mate-
rials, the mesopore data of SiC/SiO composites had a little differ-
ence. The probable reasons were that the mass of SiC from PCS
pyrolyzed at different temperatures had a little difference and the
pores formed by the accumulational SiC crystals at high tempera-
tures to increase the specific BET surface areas. In addition, the
(
m
¼
m
ꢁ j
m
2
) of the SiC/SiO composites were all close to 1 and 0 in
r
2
this case (shown in Fig. 4d), due to their non-magnetic properties.
The ordered inter-filled mesoporous structures and SiC nano-
crystals interaction had numerous complicated interfaces, at which
EM radiation with charges can enhance the polarization capability
[10,29]. Therefore, this special structure and complicated interfaces
leaded to the high ε for the SiC/SiO
pore-connectivity, the complex conductance paths were easily
formed by the SiC grains to increase the electric conductivity. This
was beneficial to the high ε for the SiC/SiO
2
0
2
-1400. As the SBA-15 with
average value of compressive strength for SiC/SiO
increased firstly and then decrease with the increasing calcination
temperature (shown in Table 1). The enhancement for the SiC/SiO
2
composites
00
2
-1400. Although the
2
-
SiC/SiO -1500 had high crystallinity, the particular structure was
2
00
0
1400 was mainly due to the high crystallinity and compactness.
destroyed and leaded to their ε and ε values all decrease (shown in
Fig. 4a and b). Therefore, the ordered inter-filled structure of the
composites in this case was a main contributor for depleting EM
wave energy.
It is well known that ε has a similar tendency with conductivity
at the same temperature, ε z
2
However, the reduction for the SiC/SiO -1500 was mainly due to
the low compactness caused by the big pores.
00
3.2. EM wave absorption properties
00
s
=2p
ε0f . As a function of synthesized
composites was
0
The mesoporous silica SBA-15 has small dielectric constant (ε
temperature, DC conductivity of the SiC/SiO
shown in Fig. 5a, which had the same tendency with the ε . In our
2
00
00
¼
3.9e4.2 and ε ¼ 0e0.2) at GHz frequency range [18]. As known
00
0
ꢁ5
to all, the real part (ε ) and imaginary part (ε ) of relative complex
case, the DC conductivities of samples were 5.46 ꢂ 10 for SiC/
00
0
ꢁ3
ꢁ
ꢁ2
permittivity (ε
r
¼ ε ꢁ jε ) represent the energy storage and dissi-
SiO
2
-1200, 1.8 ꢂ 10 for SiC/SiO
2
-1300, 7.25 ꢂ 10 for SiC/SiO
2
-
4
pation capability, respectively. So the SBA-15 is a good EM wave
1400 and 6.2 ꢂ 10
2
for SiC/SiO -1500, respectively. The SiC
00
0
transparent matrix. In Fig. 4a and b, the values of ε and ε increased
nanoparticles with high crystallinity and ordered connective
00
0
firstly and then decreased. The values of ε and ε for the SiC/SiO
2
-
structure could increase the sample’s conductivity. And the electric
conductance paths were destroyed at 1500 C to cause the low
conductivity for the SiC/SiO
From the dielectric measurement, the S-parameters (S11 and S21
were obtained. According to S-parameters, the reflection coefficient
(R), absorption coefficient (A), and transmission coefficient (T) were
00
0
ꢀ
1
400 were the highest. The dielectric loss (tan
SiO composites were illustrated in Fig. 4c. The tan
SiC/SiO -1400 were higher than others, which indicated the SiC/
SiO -1400 had stronger EM wave loss abilities. Moreover, the real
part (
d
E
¼ ε /ε ) of the SiC/
2
d
E
values of the
2
-1500.
2
)
2
00
0
m
) and imaginary part ( ) of relative complex permeability
m

X. Yuan et al. / Journal of Alloys and Compounds 680 (2016) 604e611
609
Therefore, the ordered inter-filled mesostructure was beneficial to
EM wave attenuation.
To predict the EM wave absorption of the SiC/SiO
2
composites,
the RL was calculated by the following equations: [32]
RLðdBÞ ¼ 20 log10jðZin ꢁ Z Þ=ðZ þ Z Þj
(1)
(2)
0
in
0
ꢀ
ꢁ
pffiffiffiffiffiffiffiffiffiffiffi
pffiffiffiffiffiffiffiffiffiffiffi
2
p
fd
Zin ¼ Z0
m
=ε
r
tanh j
m
*ε
r
r
r
c
where d is the absorption layer thickness, c is the velocity of light
and Zin is the normalized input impedance the EM absorption
layer, respectively. According to Eqn (1) and (2), 3-D images of
2
RL, thickness and frequency for the SiC/SiO composites were
illustrated in Fig. 6. Due to the destructive interference, the
plots of each composite exhibited the undulate shape as the
thickness. The destructive interference is caused by the inverse
ꢀ
phase (phase difference of 180 ) of the reflection EM wave from
the upper and bottom surfaces of the materials [33]. This is so-
called the quarter-wavelength principle: d ¼ ðn=4Þ
l
¼ ðn=4Þ
l =
0
1
=2
ðjε
r
jj
m
jÞ (n ¼ 1, 3, 5, 7 …), where
l
0
is the free space wave-
and , respectively.
r
length, jε
r
j and j
m
j are the moduli of ε
r
m
r
r
Therefore, combining the absorbing ability of material itself and
destructive interference caused by the thickness of material
should be the main path to loss EM wave energy. Compared the
images in Fig. 6, it was clear to see that the SiC/SiO
showed in Fig. 6c) had stronger absorbing ability than others.
To further discussion the EM absorbing property, the SiC/SiO
2
-1400
(
2
-
1400 was taken as an example. Its 2-D map of RL was shown in
Fig. 7a, in which the optimal absorptions were observed at the
thickness around 3.0 mm. The detailed RL at different thicknesses
was shown in Fig. 7b. With increasing the thickness from 2.5 mm
to 3.25 mm, the peak of RL shifted to lower frequency. When the
thickness was 2.75 mm, the minimum RL value reached ꢁ52 dB at
10.8 GHz. And the thick layer of 3.0 mm, the effective absorption
bandwidth (RL < ꢁ10 dB) covered the whole X-band, at which the
0% of incident EM wave can be attenuated. Moreover, the vertical
dot lines from the RL peaks were extended and crossed with the
1/4) curve in Fig. 7d and the crossover points were denoted by
the asteroid dots. We can see that the thicknesses of all the
asteroid dots located on the (1/4) curve were scarcely less with
9
(
l
l
that of composite. Therefore, the attenuation of EM wave
absorbing material could be modulated simply by manipulating
the material’s thickness for applications at different frequency
bands.
Impedance match is an important factor too. Cao et al. had
studied the matching and mismatching on absorbing performance
and obtained the design rules for single layer absorption materials
[
34]. In this case, the magnetic loss was about zero, due to the
Fig. 6. Three-dimensional (3-D) images of the calculated RL for the SiC/SiO
SiC/SiO -1300 (b), SiC/SiO -1400 (c) and SiC/SiO -1500 (d), respectively.
2
-1200 (a),
2
2
2
composites’ non-magnetic properties. The attenuation was
mainly caused by dielectric loss. Meanwhile, Ma et al. had pointed
ꢂ
ꢂ
ꢂ
ꢂ
2
out that
D
(
D
¼ sinh ðKfdÞ ꢁ M ) represented the impedance
2
calculated [30]. Here R and T were primarily given as R ¼ jS j and
1
1
matching degree [35], where K and M are determined by the
complex permittivity and permeability. When
2
T ¼ jS j , respectively. We can use the relation A þ R þ T ¼ 1 to
21
D
tends to zero, it
obtain A from the results of R and T. Variation of absorption co-
efficients of the SiC/SiO composites with a thickness of 2.5 mm
were given in Fig. 5b. It was clear to see that the SiC/SiO -1400 had
means that the material has a good impedance match and a good
EM wave absorption will be obtained at the corresponding
thickness. Fig. 7c showed the
2
2
D as function as thickness and fre-
a relatively higher absorption coefficient than others. The EM wave
absorbing mechanism was indicated by a schematic diagram
shown in Fig. 5c). The incident EM waves were confined within the
ordered inter-filled mesostructure and multiple reflections induced
quency for the SiC/SiO -1400. From that, the thicknesses were
2
around 3.0 mm for the good impedance match, which was
consistent with the above results. Therefore, the optimal
absorbing properties should obey the quarter-wavelength prin-
ciple and impedance matching degree.
(
the energy dissipation occurring in many different sites [20,31].

610
X. Yuan et al. / Journal of Alloys and Compounds 680 (2016) 604e611
Fig. 7. The SiC/SiO
2
-1400: (a) two-dimensional (2-D) color map of RL; (b) RL values at the various thicknesses; (c) 2-D color map of impedance match degree; (d) the (1/4)l curve.
The vertical dashed lines in (b) from RL peaks at different thicknesses to cross with (1/4)l curve in (d), and the crossover points are indicated by the asteroid dots.
4
. Conclusions
absorbing properties of 2.5D SiCf/SiC composites fabricated by a modified
precursor infiltration and pyrolysis process, J. Alloys Compd. 637 (2015)
2
61e266.
In summary, an effect EM wave absorbing material of SiC/SiO
monolith with ordered inter-filled mesostructure was prepared by
nanocasting and cold-pressing. In X-band, the SiC/SiO -1400 dis-
2
[
3] H.J. Yang, W.Q. Cao, D.Q. Zhang, T.J. Su, H.L. Shi, W.Z. Wang, J. Yuan, M.S. Cao,
NiO hierarchical nanorings on SiC: enhancing relaxation to tune microwave
absorption at elevated temperature, ACS Appl. Mater. Interfaces 7 (2015)
2
7073e7077.
played a minimum RL of ꢁ52.0 dB at 10.8 GHz and effective ab-
sorption bandwidth (RL < ꢁ10 dB) exceed the whole X-band. The
EM wave attenuation was contributed to their special structures
and intrinsic physical properties. Meanwhile, the optimal thickness
was obeyed the impedance match law and destructive interference.
Therefore, such ordered inter-filled mesostructural SiC/SiO com-
2
posites will be suitable as EM wave absorption materials for the
application at high-temperature.
[
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Acknowledgments
This work is supported by the funds of the State Key Laboratory
of Solidification Processing in NWPU (SKLSP201503) and the Nat-
ural Science Foundation of China (51502164).
Appendix A. Supplementary data
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