- Email: [email protected]
gypsum based composites filled with expanded perlite
Accepted Manuscript Electromagnetic wave absorption enhancement of carbon black/gypsum based composites filled with expanded perlite Shuai Xie, Zhijiang Ji, Yang Yang, Guoyan Hou, Jing Wang PII:
S1359-8368(16)30114-7
DOI:
10.1016/j.compositesb.2016.09.014
Reference:
JCOMB 4506
To appear in:
Composites Part B
Received Date: 24 March 2016 Revised Date:
16 June 2016
Accepted Date: 4 September 2016
Please cite this article as: Xie S, Ji Z, Yang Y, Hou G, Wang J, Electromagnetic wave absorption enhancement of carbon black/gypsum based composites filled with expanded perlite, Composites Part B (2016), doi: 10.1016/j.compositesb.2016.09.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Electromagnetic wave absorption enhancement of carbon black/gypsum based composites filled with expanded perlite
RI PT
Shuai Xie a, b, Zhijiang Ji a *, Yang Yang a, Guoyan Hou a, Jing Wang a
a. State Key Laboratory of Green Building Materials, China Building Materials
SC
Academy, Beijing 100024, PR China;
b. School of Materials Science and Engineering, Wuhan University of Technology,
M AN U
Wuhan 430070, PR China.
E-mail address: [email protected] (S. Xie), [email protected] (Z.J. Ji), [email protected] (Y. Yang), [email protected] (G.Y.
TE D
Hou), [email protected] (J. Wang)
EP
Corresponding author: Zhijiang Ji
E-mail address: [email protected]
AC C
Tel: +86 010 51167119
Fax: +86 010 51167119
1 / 37
ACCEPTED MANUSCRIPT
Abstract
2
The electromagnetic (EM) wave absorbing carbon black (CB)/gypsum based
3
composites with high wave absorption properties and wide effective bandwidth were
4
prepared by filling expanded perlite (EP) simply. The influences of CB contents, EP
5
volume concentration, EP particle size, and thickness of samples on EM wave
6
absorption were investigated, and the absorption mechanisms were analyzed as well.
7
The results indicate that the wave absorption of the composites can be remarkably
8
enhanced, due to the improvement of impedance matching as well as the single and
9
multiple scattering and refractions caused by EP particles. The reflectivity is lower
10
than –10 dB in the frequency ranges of 2–3, 5–6.5 and 8–18 GHz for the sample with
11
3% CB, when the EP volume concentration and sample thickness are 40 vol.% and 20
12
mm, respectively, with the EP diameter of 1 mm. The prepared composites with low
13
cost and high efficiency can be considered as a promising candidate used in
14
construction engineering for EM wave absorption.
SC
M AN U
TE D
EP
15
RI PT
1
Keywords: A. Hybrid; B. Electrical properties; B. Mechanical properties; Wave
17
absorption (nominated)
18
AC C
16
2 / 37
ACCEPTED MANUSCRIPT 19
1. Introduction Gypsum is an inorganic cementitious material, which is one of the earliest
21
building materials elaborated by mankind and its utilization history can be traced to
22
4000 years ago [1]. Nowadays, gypsum based material is widespread use in the
23
construction industry as its easy extraction and large reserves especially in China.
24
Meanwhile, the gypsum is a traditional finishing material because of its low cost,
25
convenient application and excellent finishing appearance. The gypsum based
26
products also possess the characteristics of light weight, high strength, noise and
27
thermal isolation, as well as inflaming retarding, and all of these properties of gypsum
28
based products have been extensively studied [2-4]. As the increasing uses of
29
household appliances, communication devices, electronic products, and wireless
30
networks, severe electromagnetic (EM) radiation is being generated everywhere. And
31
it has become a serious pollution issue, not only influence the normal operation of
32
electronic devices, but also do harm to human beings’ health [5-7]. Therefore, the
33
demands for developing EM wave absorbing materials with wider absorbing
34
bandwidth and more effective absorption performance used in construction industry
35
are increasing, and so many EM wave absorbing building materials have been
36
developed, such as cement-based materials [8-10], ceramics [11-14], wood-based
37
materials [15,16], etc. However, by now the EM wave absorption properties of
38
gypsum based materials are seldom reported.
AC C
EP
TE D
M AN U
SC
RI PT
20
39
In previous research of the EM wave absorbing materials, both magnetic loss
40
materials and dielectric loss materials are used as the wave absorbing agent. The 3 / 37
ACCEPTED MANUSCRIPT development of EM wave absorbing materials using magnetic loss materials, such as
42
ferrite, carbonyl iron, etc., was widely achieved [17-19]. But there is an obvious
43
weakness of absorption performance in high frequency ranges, as well as a critical
44
weakness of being heavy. The research of dielectric absorbers using dielectric loss
45
materials as absorbing agent indicate that a weight advantage can be achieved
46
compared to the magnetic loss materials [20-23]. And the absorption performance of
47
the nanoscale dielectric loss materials carbon black (CB) and carbon nanotubes
48
(CNTs) is much better [24-26], due to the effects of their smaller size, lager specific
49
surface and more interfaces. However, as a single agent, either CB or CNTs still
50
possesses some disadvantages, such as small absorption peak and narrow effective
51
absorption bandwidth [27,28], because of the impedance mismatching. Thus, based on
52
the impedance matching principle [29], an effective method to decrease the
53
permittivity of the dielectric loss absorber is the introduction of low EM parameters
54
materials.
TE D
M AN U
SC
RI PT
41
Porous materials, such as expanded polystyrene (EP), hollow glass microspheres
56
(HGM) and expanded perlite (EP), etc., have a series of excellent properties such as
57
low density, low EM parameters and high specific surface. It has been reported that
58
the EM wave absorbing properties of the cement-based materials can be improved
59
obviously by filling EP or EPS beads, and the reflectivity of the cement based
60
materials was lower than –10 dB in 8–18 GHz frequency range [30-32]. Therefore, it
61
is an ideal method to improve the impedance matching and EM wave absorption
62
performance by introducing porous materials into matrix. However, investigation into
AC C
EP
55
4 / 37
ACCEPTED MANUSCRIPT 63
the effects of porous materials on the EM parameters and wave absorbing properties
64
of gypsum based composites, as well as the wave absorption mechanisms are still
65
scarce and remain to be explored, which motivates the major objective of this work. In this work, EM wave absorbing gypsum based composites with good
67
absorption properties, a simple process, low density and low cost were fabricated. The
68
economy and practicability of the composites for construction industry must be
69
considered, thus, the CB with lower price was used as absorption agent and the EP
70
particles were introduced into matrix to enhance the EM wave absorption
71
performance. The aim of this work is to investigate the effects of EP on the EM
72
absorption properties of the CB/gypsum based composites, and the impacts on the
73
wave absorbing effectiveness, such as the volume concentration of EP, the diameter of
74
EP and sample thickness, were analyzed in detail. The absorption mechanisms of the
75
gypsum based composites filled with EP particles were discussed as well.
76
2. Materials and methods
77
2.1 Materials
EP
TE D
M AN U
SC
RI PT
66
Gypsum powders were produced by Inner Mongolia Grassland Gypsum Powder
79
Plant, China, and some basic properties are listed in Table 1. Expanded perlite, with
80
the average diameters of 1 mm and 3 mm, were procured from Shanghai LongYuan
81
Industrial Co., Ltd., China. The bulk density of the EP particles is 150 kg/m3, and the
82
chemical compositions are shown in Table 2. Acetylene carbon black was supplied by
83
Tianjin Jinqiushi Chemical Industry Co., Ltd., China, and the main properties are
84
shown in Table 3. The micro-morphologies and structures of expanded perlite and
AC C
78
5 / 37
ACCEPTED MANUSCRIPT carbon black were studied by SEM and TEM, and the images are shown in Fig. 1.
86
Table 1 Some basic performances of the gypsum
87
Table 2 Chemical compositions of the expanded perlite
88
Table 3 Main properties of the carbon black
89
Fig. 1. Micrograph of the EP and CB particles: (a) SEM image of EP; (b) TEM image of CB.
90
2.2 Preparation process of the gypsum based composites
RI PT
85
The main process for preparing the gypsum based composites was displayed in
92
Fig.2. The gypsum powders, CB and deionized water were first mixed in a mixer for
93
about 3 minutes, and then the EP particles were added into the gypsum plaster
94
gradually with the designed volume concentrations, and mixed for another 3 minutes
95
to achieve the uniform distribution of EP particles. Then the prepared plaster was
96
poured into the moulds with the size of 180 mm × 180 mm × 10/15/20 mm (for the
97
measurement of EM wave reflectivity) and 40 mm × 40 mm × 160 mm (for the
98
measurement of flexural and compressive strength). Then the moulds were vibrated to
99
remove air bubbles. The specimens were removed from their moulds after 2 hours and
100
then dried in a constant-temperature dry box with the temperature of 50℃ until their
101
quality are not changed with time.
102
Fig. 2. Schematic diagram of preparation process of the gypsum based composite.
103
2.3 Measurement of properties
AC C
EP
TE D
M AN U
SC
91
104
The morphologies and microstructures of raw materials and prepared composites
105
are characterized by scanning electron microscopy (SEM, Quanta 200) and
106
transmission electron microscopy (TEM, Tecnai F20 ST). The compressive strength 6 / 37
ACCEPTED MANUSCRIPT 107
and flexural strength of the gypsum based composites are tested by a flexural and
108
compressive strength testing machine (TYE-300D). The EM parameters of raw materials are measured by coaxial line method in the
110
frequency range of 2–18 GHz, and the samples for coaxial line method were prepared
111
by paraffin with 50 vol.% powders of testing materials and compressing into
112
cylindrical shaped (φout = 7 mm, φinner = 3.04 mm and 3 mm thickness). The EM
113
parameters of the prepared gypsum based composites are measured by waveguide
114
method only in X-band and Ku-band, because of the limitation of test equipment. And
115
the samples for waveguide method are rectangles with the sizes of 22.9 mm × 10.2
116
mm × 10.0 mm (for X-band) and 15.8 mm × 7.9 mm × 5.0 mm (for Ku-band),
117
respectively. The EM wave reflectivity is measured by arch reflecting method in the
118
frequency ranges of 2–18 GHz, according to the national standard GJB 2038A-2011.
119
The testing system of arch reflecting method is shown in Fig. 3. The test system
120
should be calibrated before measurement, in order to make sure of the accuracy of the
121
testing results.
EP
TE D
M AN U
SC
RI PT
109
The measurement of EM parameters and EM wave reflectivity are launched in
123
the State Key Laboratory of Green Building Materials in Beijing, China. And the test
124
equipment include an Agilent 5234A Vector Network Analyzer, Agilent 85071E
125
testing software, standard horn antennas, 7 mm coaxial airline clamp, X-band and
126
Ku-band waveguide clamps.
127
Fig. 3. Sketch map of the arch reflecting method system.
128
3. Theory analysis
AC C
122
7 / 37
ACCEPTED MANUSCRIPT To obtain an EM wave absorber with excellent absorption performance, there are
130
two essential requirements needed. One is that the absorber should have a good
131
impedance matching to make the incident EM wave transmit into the absorber easily;
132
another is that the absorber should have a good EM wave dissipation capacity. The
133
propagation of EM wave in an absorber is shown in Fig. 4, when EM waves transmit
134
to the surface of the absorber, part of them will be reflected first. Then, some of the
135
incident wave will be absorbed by the absorber, and some remains will transmit back
136
to the free space. In an EM wave absorber, the equation must be satisfied [33]:
SC
M AN U
137
RI PT
129
t+r+a=1
(1)
where t , r and a represent the transmission coefficient, reflection coefficient and
139
absorption coefficient, respectively. Thus, both improving the impedance matching to
140
reduce the reflection coefficient and enhancing the EM loss characteristic to increase
141
the absorption coefficient are reasonable methods to improve the EM wave absorption
142
properties.
143
Fig. 4. Graphical representation of the propagation of EM wave inside an absorber
144
3.1 Improvement of impedance matching
146 147
EP
AC C
145
TE D
138
As is known that in an optimal situation of impedance matching, the EM
parameters of wave absorber should meet the following equation [29]: ε' = µ', ε" = µ"
(2)
148
where ε', µ', ε" and µ" are the real and imaginary parts of permittivity and permeability,
149
respectively. Therefore, in a dielectric loss absorber, the impedance matching
150
properties can be improved by decreasing the permittivity of the absorber to make the 8 / 37
ACCEPTED MANUSCRIPT 151
values of ε' and ε" close to µ' and µ". The EM parameters of the gypsum, CB and EP are shown in Fig. 5, from which
153
it can be observed that all of the raw materials are non-magnetic loss materials. The ε'
154
and ε" of CB are in the ranges of 38–180 and 40–125, respectively, in the frequency
155
range of 2–18 GHz, indicating that the CB is a kind of strong dielectric loss material.
156
The ε' and ε" of gypsum materials are approximate 5.5 and 0, respectively, in 2–18
157
GHz, implying the insignificant dielectric loss for EM wave. It can be predicted based
158
on the effective medium theory [34,35] that the permittivity of the gypsum based
159
composites can be increased obviously by introducing CB, leading to a serious
160
impedance mismatching. However, the introduction of the EP particles with much
161
lower permittivity (ε' ≈ 2.2，ε" ≈ 0) will reduce the permittivity of the composites, and
162
the impedance matching properties can be improved. In addition, more space network
163
structures will be formed by the porous EP particles in the composites, providing
164
more propagation path for the incident wave, which is beneficial to the improvement
165
of impedance matching as well [30,31].
166
Fig. 5. EM parameters of (a) carbon black, (b) gypsum powders and (c) expanded perlite
167
3.2 Enhancement of EM loss characteristic
SC
M AN U
TE D
EP
AC C
168
RI PT
152
Before introducing EP particles, the CB/gypsum based composites absorb the
169
incident wave only by the tunnel effect, leakage conductance effect, damping
170
vibration, and polarization effect of the CB particles [36-38]. When EP particles are
171
introduced, the complex refractions and scattering of the EP particles will play an
172
important role in wave attenuation. The propagation of the incident wave in a single 9 / 37
ACCEPTED MANUSCRIPT particle is shown in Fig. 6(a). When EM wave propagates in the EP filled composites,
174
the EM wave attenuation of a single particle Iatt includes the absorption attenuation of
175
reflected wave Iab and scattering attenuation of scattered wave Isc, and they satisfied
176
the equation Iatt = Iab + Isc [39].
177
Fig. 6. Schematic diagram of the scattering and reflections of incident wave: (a) in a single particle; (b) between
178
multiple particles.
RI PT
173
Moreover, the multiple scattering and reflections between the particles, which is
180
displayed in Fig. 6(b), must be taken into account. On the one hand, the multiple
181
scattering can increase wave attenuation by the particles; on the other hand, the
182
multiple reflections between particles also increase the propagation length of incident
183
wave in the composite [40], leading to the enhancement of the attenuation by the
184
CB/gypsum matrix.
TE D
M AN U
SC
179
From the above analysis, it can be predicted that the impedance matching
186
property and wave dissipation capacity of CB/gypsum based composite could be
187
improved by introducing EP particles, leading to the enhancement of EM wave
188
absorption. And the effects of EP particles on EM wave absorption are discussed in
189
detail in the following sections.
190
4. Results and discussion
191
4.1 Electromagnetic parameters
AC C
EP
185
192
The complex permittivity of the EP filled gypsum based composites was
193
investigated by waveguide method in 8.2–18 GHz frequency range. The testing
194
system and the measurement results are shown in Fig. 7. The CB mass fraction of the 10 / 37
ACCEPTED MANUSCRIPT 195
test samples is 3%, and the average diameter of the introduced EP particles is 1 mm. As seen from Fig. 7(b) and (c), both the real part ε' and the imaginary part ε" of
197
the complex permittivity can be reduced obviously by introducing EP, and with the
198
increase of EP volume concentration, the values of ε' and ε" decrease constantly.
199
According to Eq (2), for the non-magnetic loss materials, the impedance matching
200
performance can be improved by the decrease of complex permittivity. Therefore, the
201
introduction of EP particles can improve the impedance matching of CB/gypsum
202
based composites assuredly. And the EP volume concentration also plays an important
203
role in the improvement of impedance matching.
204
Fig. 7. The measurement system of waveguide method (a), the real part (b) and imaginary part (b) of the complex
205
permittivity of the composites.
206
4.2 Electromagnetic wave absorption properties
207
4.2.1
TE D
M AN U
SC
RI PT
196
Enhancement of wave absorption properties The EM wave absorption performance of the CB/gypsum composites and EP
209
filled CB/gypsum composites were measured by arch reflecting method as illustrated
210
in Fig. 8. The –10 dB reflectivity means that the absorber can attenuate 90% of the
211
incident wave. The EP particle diameter of the following samples is 1 mm, and the
212
sample thickness is 20 mm.
AC C
213
EP
208
It can be seen from the reflectivity curves shown in Fig. 8 that the EM wave
214
absorbing properties of the gypsum composites can be obviously enhanced by the
215
introduction of EP particles. Meanwhile, the variation of CB contents also plays an
216
important role in the enhancement of wave absorption. When the composite is 11 / 37
ACCEPTED MANUSCRIPT unfilled CB, the enhancement of wave absorption by introducing EP particles is
218
insignificant as shown in Fig. 8 (a). With the increasing of CB content, the effect of
219
EP particles on the enhancement of wave absorption becomes more and more
220
significant. When the composites with 1% or 2% CB as shown in Fig. 8 (b) and (c),
221
only the lowest reflectivity decreases. With the continual increase of CB content, the
222
reflectivity of the EP filled composites becomes lower than those without EP particles
223
in the whole frequency range of 2–18 GHz, which can be observed in Fig. 8 (d)–(f).
224
For the composite filled with 3% CB and 40 vol.% EP, a minimum reflectivity of –15
225
dB at 2 GHz and a wide effective bandwidth (reflectivity less than –10 dB) of 12.5
226
GHz (2–3, 5–6.5 and 8–18 GHz) can be achieved. Hence, the CB/gypsum based
227
composites with excellent absorption properties was really obtained by introducing
228
EP particles. The enhancement of wave absorption by introducing EP particles can be
229
attributed to the improvement of impedance matching and EM dissipation capacity
230
[41]. The decrease of the permittivity can improve the impedance matching between
231
the composite and free space based on Eq. (2). In addition, new EM wave attenuation
232
path such as multiple scattering and reflections has been provided by EP particles,
233
causing the promotion of EM wave dissipation capacity.
SC
M AN U
TE D
EP
AC C
234
RI PT
217
It is worth noting that the wave absorbing properties of the composites with 4%
235
or 5% CB will be weakened, whose minimum reflectivity even cannot reach –10 dB.
236
However, the effect of EP particles on the enhancement of wave absorption is still
237
obvious. The skin depth ∆ of the incident wave can be expressed as [42].
238
∆ = 2 π 2 f 2 µε "
(3) 12 / 37
ACCEPTED MANUSCRIPT where µ is the permeability of absorbing materials; ε" is the imaginary part of
240
absorbing materials; and f is the frequency of incident wave. The permittivity ε″ of the
241
composite can be increased when CB content increases, leading to the decrease of the
242
skin depth, according to Eq. (3). When the skin depth is less than the thickness of the
243
composite, the incident wave cannot penetrate the composite and the propagation
244
length becomes shorter, resulting in the decrease of interference offset and wave
245
attenuation [9]. That is the main reason for the weak absorption peak and poor
246
absorption performance of the composites with 4% or 5% CB as illustrated in Fig. 8
247
(e) and (f).
248
Fig. 8. The enhancement of EM wave absorption by the introduction of EP particles, (a)–(f): CB 0%–5 % and EP
249
concentration is 40 vol.%.
M AN U
SC
RI PT
239
The EM wave absorption properties of some representative cement based
251
absorbing composites filled with porous fillers are summarized in Table 4, and
252
comparing with the experimental results of this work. It can be discovered visibly that
253
the effective bandwidth of the prepared composite in this work is wider than the EP or
254
EPS filled cement based materials, due to the lower permittivity and more lacunose
255
interior structure of gypsum composites which is more beneficial to impedance
256
matching and EM wave transmission [43].
257
Table 4 EM wave absorption properties of some representative porous cement based materials and gypsum based
258
materials prepared in this work
259
4.2.2
260
AC C
EP
TE D
250
Effect of the EP volume concentration
Fig. 9 indicates the effects of EP volume concentration on the EM wave 13 / 37
ACCEPTED MANUSCRIPT absorption performance of the CB/gypsum based composites, from which it can be
262
seen that the wave absorption increases with the increase of EP volume concentration,
263
but it does not increase monotonically. It can be discovered that the composite filled
264
with 40 vol.% EP particles exhibits optimal wave absorption performance. The
265
numbers of EP particles increase with the increase of EP volume concentration, which
266
lead to the increase of the multiple scattering and reflections between EP particles.
267
Besides, the impedance matching property between the composite and free space
268
improved by increasing EP volume concentration, and the incident wave could
269
transmit into the composite much easier. Therefore, the EM wave absorption increases
270
with the EP volume concentration.
M AN U
SC
RI PT
261
However, the further introduction of EP particles will decrease wave absorption
272
as shown in Fig. 9. The decrease of the permittivity, which can lead to a reduction of
273
EM dissipation capacity, may be the main reason for the decrease of wave absorption.
274
Fig. 9. Effects of EP volume concentration on the EM wave absorbing properties.
275
4.2.3
TE D
271
EP
Effect of the EP diameter The effects of EP diameters on the EM wave absorption properties are shown in
277
Fig. 10, from which it can be observed that the filling of 1 mm EP particles is more
278
beneficial to wave absorption. As to the composite with 2 % CB, lower peak values of
279
reflectivity can be obtained by introducing 1 mm EP particles. As to the composites
280
with 3 % CB, the reflectivity of the composite filled with 1 mm EP is lower than that
281
filled with 3 mm EP in the whole range of 2–18 GHz. For the gypsum based
282
composites filled with EP particles, in fact, the decrease of the EP diameter is the
AC C
276
14 / 37
ACCEPTED MANUSCRIPT increase of the particle numbers at the same EP volume concentration, which provides
284
more opportunities for scattering and multiple scattering and refractions of the
285
incident wave. So the EM wave absorption performance of the gypsum composite can
286
be increased visibly by filling EP particles with smaller diameters.
287
Fig. 10. Effects of EP diameters on the EM wave absorbing properties: (a) CB content is 2%; (b) CB content is
288
3%.
289
4.2.4
SC
Effect of the sample thickness
RI PT
283
Fig. 11 presents the effect of thickness variation on the wave absorption of the
291
composites, and the samples for measurement are filled with 3% CB and 40 vol.% EP.
292
The experimental results indicate that the intensity of the reflectivity peak is sensitive
293
to the thickness, and the number of peaks increases with the increase of sample
294
thickness. Moreover, the shape of the reflectivity curve becomes smoother with the
295
increase of sample thickness. The variation of the reflectivity peaks of the samples
296
with different thickness can be explained by the interference theory [44]:
TE D
f =
( 2n + 1) c n=0, 1, 2, 3…
EP
297
M AN U
290
4d ε r µ r
(4)
where f is the frequency of incident wave; n is the number of peaks; εr and µr are the
299
complex permittivity and complex permeability of the sample, respectively; c is the
300
velocity of EM wave in free space; and d is the thickness. From Eq. (4), it can be seen
301
that the increase of thickness d could lead to the increase of the number of peaks,
302
when εr and µr are invariable. Simultaneously, the increase of thickness makes the
303
possibility of incident wave penetrating the sample becomes smaller, decreasing the
304
interference offset of the reflection wave between the top and the bottom of the
AC C
298
15 / 37
ACCEPTED MANUSCRIPT 305
sample [9]. Therefore, the reflectivity curves tend to be smoother as the increase of
306
sample thickness.
307
Fig. 11. Effects of sample thickness on the EM wave absorbing properties.
308
4.2.5
311
RI PT
310
According to the transmission line theory and impedance matching principle, the EM wave reflectivity can be expressed as follows [45-47]:
R = 20 log
Z in − Z 0 µ0 µ r j 2π fd tanh , Z in = ⋅ ε 0ε r µ 0 µ r Z in + Z 0 ε 0ε r c
SC
309
Comparison of calculated and experimental wave absorption properties
(5)
where Zin is the input impedance of the absorber; εr = ε' – jε" and µr = µ' – jµ" are the
313
complex permittivity and complex permeability of the absorber, respectively; ε0 and
314
µ0 are the permittivity and permeability of free space, respectively; c is the velocity of
315
EM wave in free space; f is the frequency of incident EM waves; and d is the
316
thickness of the absorber. According to Eq. (5) and the measured EM parameters
317
shown in Fig. 7, the EM wave absorption of several samples (with CB 3% and EP
318
particles 0–60 vol.%) was calculated in 8.2–18 GHz frequency range.
EP
TE D
M AN U
312
Fig. 12 reveals the differences between calculated and experimental reflectivity
320
values, from which it can be discovered that the errors between the calculated and
321
experimental reflectivity values cannot be avoided. It is obvious that the experimental
322
reflectivity values are lower than the calculated results in the whole X and Ku band,
323
when EP particles were introduced into the composites. The main reason for this
324
phenomenon is that the effects of multiple scattering and reflections on EM wave
325
reflectivity are not considered in the calculated equations. In addition, it can be seen
326
that the vibration of the calculated curves is larger compared with those experimental
AC C
319
16 / 37
ACCEPTED MANUSCRIPT curves, which can be attributed to the large volatility of the measured EM parameters
328
values as shown in Fig. 7. However, it is can be discovered from Fig. 12 that the
329
variation trend of the calculated and experimental results of each sample are basically
330
coincident, and the improvement of wave absorption by introduction of EP can be
331
observed clearly.
332
Fig. 12. Comparison of calculated and experimental reflectivity of the composites with 3% CB and 0 vol.%–60
333
vol.% (a)–(d) EP with 1 mm diameter.
334
4.3 Mechanical properties
M AN U
SC
RI PT
327
The effects of EP particles on the flexural and compressive strength were
336
investigated as well, and the experimental results are shown in Fig. 13. It can be
337
discovered easily from Fig. 13 that both the flexural strength and compressive
338
strength are reduced by the EP introduction, when the composite with 20 vol.% EP,
339
the flexural strength and compressive strength are 4.6143 and 8.4684 MPa,
340
respectively, which is approximately 15 % and 30 % lower than the composite
341
without EP. And substantial reductions in the flexural and compressive strength were
342
obtained also for the higher EP contents. When the EP content is 60 vol.%, the
343
flexural and compressive strength are only 2.6347 and 5.0437 MPa, respectively. The
344
compressive strength can be reduced due to the low strength and specific gravity of
345
EP [48]. Also, the adhesive performance between gypsum plaster is reduced by filling
346
EP, which can cause the reduction of flexural strength. The decrease of mechanical
347
properties is an important problem to be resolved in our following work.
348
Fig. 13. The flexural and compressive strength of the gypsum based composites with 3% CB and different volume
AC C
EP
TE D
335
17 / 37
ACCEPTED MANUSCRIPT 349
concentration of EP.
350
5 Conclusions The EM wave absorption performance of CB/gypsum based composite has been
352
remarkably enhanced through introducing expanded perlite, owing to the
353
improvement of impedance matching, as well as the single and multiple scattering and
354
refractions caused by EP particles. The EM absorption properties increase with the
355
increase of CB contents and EP volume concentration, but there is an optimal
356
concentration for CB and EP, respectively. Moreover, the smaller EP diameters and
357
larger thickness are beneficial to the enhancement of wave absorption. With an EP
358
volume concentration of 40 vol.%, CB content of 3 % and EP diameter of 1 mm, this
359
composite with a thickness of 20 mm exhibits the best wave absorption performance.
360
The effective bandwidth for –10 dB can be 12.5 GHz (2–3, 5–6.5 and 8–18 GHz),
361
which is wider than most of the reported cement composites filled with porous
362
aggregates. However, the flexural and compressive strength were reduced due to the
363
filling of EP, and this issue will be resolved in our following works.
364
Acknowledgements
SC
M AN U
TE D
EP
AC C
365
RI PT
351
This work was supported by the National Science & Technology Pillar Program during the
366
12th Five-year Plan Period of P. R. China (No. 2014BAB15B02-02).
367
References
368
[1] Yu QL, Brouwers HJH. Development of a self-compacting gypsum–based lightweight
369 370 371
composite. Cem Concr Compos 2012; 34: 1033–43. [2] Zhou TY, Darkwa J, Kokogiannakis G. Thermal evaluation of laminated composite phase change material gypsum board under dynamic conditions. Renew Energ 2015; 78: 448–56.
372
[3] Raghavendra T, Udayashankar BC. Engineering properties of controlled low strength
373
materials using fly ash and waste gypsum wall boards. Constr Build Mater 2015; 101: 18 / 37
ACCEPTED MANUSCRIPT 374 375 376
448–57. [4] Keerthan P, Mahendran M. Numerical studies of gypsum plasterboard panels under standard fire conditions. Fire Safety J 2012; 53: 105–19.
377
[5] Zhang J, Xiao P, Zhou W, Hong W, Luo H. Preparation and microwave absorbing properties
378
of carbon fibers/epoxy composites with grid structure. J Mater Sci: Mater Electr 2015; 26:
379
651–58. [6] Gogoi JP, Bhattacharyya NS, James Raju KC. Synthesis and microwave characterization of
381
expanded graphite/novolac phenolic resin composite for microwave absorber applications.
382
Composites: Part B 2011; 42: 1291-97.
RI PT
380
[7] Gogoi JP, Bhattacharyya NS, Bhattacharyya S. Single layer microwave absorber based on
384
expanded graphite-novolac phenolic resin composite for X-band applications. Composites:
385
Part B 2014; 58: 518-23.
SC
383
[8] Nam IW, Lee HK. Synergistic effect of MWNT/fly ash incorporation on the EMI
387
shielding/absorbing characteristics of cementitious materials. Constr Build Mater 2016; 115:
388
651–61.
389 390
M AN U
386
[9] Wang BM, Guo ZQ, Han Y. Electromagnetic wave absorbing properties of multi–walled carbon nanotube/cement composites. Constr Build Mater 2013; 46: 98–103.
391
[10] Li KZ, Wang C, Li HJ, Li XT, Ouyang HB, Wei J. Effect of chemical vapor deposition
392
treatment of carbon fibers on the reflectivity of carbon fiber-reinforced cement-based
393
composites. Compos Sci Technol, 2008; 68: 1105–14.
395
[11] Yin XW, Kong L, Zhang LT, Cheng LF, Travitzky N, Greil P. Electromagnetic properties of
TE D
394
Si–C–N based ceramics and composites. Int Mater Rev 2014; 59: 326-55. [12] Han MK, Yin XW, Duan WY, Ren S, Zhang LT, Cheng LF. Hierarchical graphene/SiC
397
nanowire networks in polymer-derived ceramics with enhanced electromagnetic wave
398
absorbing capability. J Eur Ceram Soc 2016; 36: 2695-703.
EP
396
[13] Bantsis G, Sikalidis C, Betsiou M, Yioultsis T, Xenos T. Electromagnetic absorption,
400
reflection and interference shielding in X–band frequency range of low cost ceramic building
401
bricks and sandwich type ceramic tiles mill scale waste as an admixture. Ceram Int 2011; 37:
402
AC C
399
3535–45.
403
[14] Yao R, Liao SY, Dai CL, Liu YC, Chen XY, Zheng F. Preparation and characterization of
404
novel glass–ceramic tile with microwave absorption properties from iron ore tailings. J Magn
405
Magn Mater 2015; 378: 367–75.
406
[15] Oka H, Kataoka Y, Osada H, Aruga Y, Izumida F. Experimental study on electromagnetic
407
wave absorbing control of coating–type magnetic wood using a grooving process. J Magn
408
Magn Mater 2007; 310: e1028–29.
409
[16] Oka H, Terui M, Osada H, Sekino N, Namizaki Y, Dawson FP. Electromagnetic wave
410
absorption characteristics adjustment method of recycled powder–type magnetic wood for
411
use as a building material. IEEE Trans Magn 2012; 48: 3496–500.
412
[17] Yang
RG.
Electromagnetic
properties
and
microwave
absorption
properties
of
19 / 37
ACCEPTED MANUSCRIPT 413
BaTiO3–carbonyl iron composites in S and C bands. J Magn Magn Mater 2011; 323:
414
1805–10.
415 416
[18] Feng YB, Qiu T, Shen CY, Li XY. Electromagnetic and absorption properties of carbonyl iron/rubber radar absorbing materials. IEEE Trans Magn, 2006; 3: 463–68. [19] Ye JW, Liu Y, Zhang J, Chen XF, Yao MY. Preparation and electromagnetic wave absorption
418
properties of Sm2O3/α–Fe/Sm2Fe17Nx composites. J Magn Magn Mater 2013; 335: 32–35.
419
[20] Oh JH, Oh KS, Kim CG, Hong CS. Design of radar absorbing structures using glass/epoxy
420
composite containing carbon black in X–band frequency ranges. Composites: Part B 2004;
421
35: 49–56.
RI PT
417
[21] Du YC, Liu T, Yu B, Gao HB, Xu P, Wang JY, Wang XH, Han XJ. The electromagnetic
423
properties and microwave absorption of mesoporous carbon. Mater Chem Phys 2012; 135:
424
884–91.
SC
422
[22] Han MK, Yin XW, Kong L, Li M, Duan WY, Zhang LT, Cheng LF. Graphene-wrapped ZnO
426
hollow spheres with enhanced electromagnetic wave absorption properties. J Mater Chem A
427
2014; 2: 16403–09.
M AN U
425
428
[23] Han MK, Yin XW, Ren S, Duan WY, Zhang LT, Cheng LF. Core/shell structured C/ZnO
429
nanoparticles composites for effective electromagnetic wave absorption. RSC Adv 2016; 6:
430
6467-74.
[24] Micheli D, Apollo C, Pastore R, Marchetti M. X–Band microwave characterization of
432
carbon–based nanocomposite material, absorption capability comparison and RAS design
433
simulation. Compos Sci Technol 2010; 70: 400–9.
TE D
431
[25] Kim JB, Lee SK, Kim CG. Comparison study on the effect of carbon nano materials for
435
single–layer microwave absorbers in X–band. Compos Sci Technol 2008; 68: 2909–16.
436
[26] Yang QX, Liu L, Hui D, Chipara M. Microstructure, electrical conductivity and microwave
437
absorption properties of γ-FeNi decorated carbon nanotube composites. Composites: Part B
438
2016; 87: 256–62.
440
[27] Liu XX, Zhang ZY, Wu YP. Absorption properties of carbon black/silicon carbide microwave absorbers. Composites: part B 2011; 42: 326–29.
AC C
439
EP
434
441
[28] Fan ZJ, Luo GH, Zhang ZF, Zhou L, Wei F. Electromagnetic and microwave absorbing
442
properties of multi–walled carbon nanotubes/polymer composites. Mater Sci Eng B 2006;
443
132: 85–9.
444
[29] Zhang ZL, Ji ZJ, Duan YP, Gu SC, Guo JB. The superior electromagnetic properties of
445
carbonyl–iron/Fe91.2Si3.1P2.9Sb2.8 composites powder and impedance matching. J Mater Sci:
446
Mater Electr 2013; 24: 968–73.
447 448 449 450 451
[30] Guan HT, Liu SH, Duan YP. Investigation of the electromagnetic characteristics of cement based composites filled with EPS. Cem Concr Compos 2007; 28: 49–54. [31] Li BY, Duan YP, Zhang YF. Electromagnetic wave absorbing properties of cement–based composites filled with porous materials. Mater Des 2011; 32: 3017–20. [32] Li BY, Duan YP, Liu SH. The electromagnetic characteristics of fly ash and absorbing 20 / 37
ACCEPTED MANUSCRIPT 452
properties of cement–based composites using fly ash as cement replacement. Constr Build
453
Mater 2012; 27: 184–88.
455 456 457 458 459 460 461
[33] Musil J, Zacek F. Microwave Measurements of Complex Permittivity by Free Space Methods and Their Applications. Elsevier, New York, 1986. [34] Zhang H, Shen YQ, Xu YC, Zhu HY, Lei M. Effective medium theory for two-dimensional random media composed of core-shell cylinders. Opt Commun 2013; 306: 9–16. [35] Vincenti MA, Ceglia D. de. Effective medium theories, in: Haus J (Eds.), Fundamentals and
RI PT
454
Applications of Nanophotonics, Woodhead Publishing, 2016: 211-32.
[36] Wang M, Duan YP, Liu SH, Li XG, Ji ZJ. Absorption properties of carbonyl–iron/carbon black double–layer microwave absorbers. J Magn Magn Mater 2009; 321: 3442–46.
[37] Vinayasree S, Soloman MA, Sunny V, Mohanan P, Kurian P, Anantharaman MR. A
463
microwave absorber based on strontium ferrite–carbon black–nitrile rubber for S and X–band
464
applications. Compos Sci Tech 2013; 82: 69–75.
SC
462
[38] A. Al-Ghamdi A, A. A l-Hartomy O, R. Al-Solamy F, Dishovsky N, Malinova P, Atanasova G,
466
Atanasov N. Conductive carbon black/magnetite hybrid fillers in microwave absorbing
467
composites based on natural rubber. Composites: Part B 2016; 96: 231-41.
469 470 471 472 473
[39] Duan YP, Liu SH, Wen B, Guan HT, Wang GQ. A discrete slab absorber: absorption efficiency and theory analysis. J Compos Mater 2006; 20: 1841–51. [40] Guan HT, Liu SH, Duan YP. Expanded polystyrene as an admixture in cement–based composites for electromagnetic absorbing. J Mater Eng Perform 2007; 16: 68–72. [41] Hu SG, Tian K, Ding QJ. Design and test of new cement based microwave absorbing
TE D
468
M AN U
465
materials. ISAPE 2008. 8th International Symposium 2–5 Nov. 2008: pp956–59. [42] Idris FM, Hashim M, Abbas Z, Ismail I, Nazlan R, Ibrahim IR. Recent developments of smart
475
electromagnetic absorbers based polymer–composites at gigahertz frequencies. J Magn Magn
476
Mater 2016; 405: 197–208.
478 479 480 481 482 483 484 485
[43] Zhang XZ, Sun W. Microwave absorbing properties of double–layer cementitious composites containing Mn–Zn ferrite. Cem Concr Compos 2010; 32: 726–30. [44] Xie S, Yang Y, Hou GY, Wang J, Ji ZJ. Development of layer structured wave absorbing
AC C
477
EP
474
mineral wool boards for indoor electromagnetic radiation protection. J Build Eng 2016; 5: 79–85.
[45] Zou CW, Yao YD, Wei ND, Gong YC, Fu WD, et al. Electromagnetic wave absorption properties of mesoporous Fe3O4/C nanocomposites. Composites Part: B 2015; 77: 209–14.
[46] Li WP , Zhu LQ, Gu J, Liu HC. Microwave absorption properties of fabric coated absorbing material using modified carbonyl iron power. Composites: Part B 2011; 42: 626–30.
486
[47] Shan LM, Chen XN, Tian X, Chen JJ, Zhou ZW, Jiang M, Xu XL, Hui D. Fabrication of
487
polypyrrole/nano-exfoliated graphite composites by in situ intercalation polymerization and
488
their microwave absorption properties. Composites: Part B 2015; 73: 181-7.
489 490
[48] Oktaya H, Yumrutaşb R, Akpolatb A. Mechanical and thermophysical properties of lightweight aggregate concretes. Constr Build Mater 2015; 96: 217–25. 21 / 37
ACCEPTED MANUSCRIPT Table Captions Table 1 Some basic performances of the gypsum Table 2 Chemical compositions of the expanded perlite Table 3 Main properties of the carbon black Table 4 EM wave absorption properties of some representative porous cement based materials and gypsum based
AC C
EP
TE D
M AN U
SC
RI PT
materials prepared in this work
22 / 37
ACCEPTED MANUSCRIPT Figure Captions Fig. 1. Micrograph of the EP and CB particles: (a) SEM image of EP; (b) TEM image of CB. Fig. 2. Schematic diagram of preparation process of the gypsum based composite. Fig. 3. Sketch map of the arch reflecting method system. Fig. 4. Graphical representation of the propagation of EM wave inside an absorber Fig. 5. EM parameters of (a) carbon black, (b) gypsum powders and (c) expanded perlite
multiple particles.
RI PT
Fig. 6. Schematic diagram of the scattering and reflections of incident wave: (a) in a single particle; (b) between
Fig. 7. The measurement system of waveguide method (a), the real part (b) and imaginary part (b) of the complex permittivity of the composites.
Fig. 8. The enhancement of EM wave absorption by the introduction of EP particles, (a)–(e):CB 0%–5 % and EP concentration is 40 vol.%.
SC
Fig. 9. Effects of EP volume concentration on the EM wave absorbing properties.
Fig. 10. Effects of EP diameters on the EM wave absorbing properties: (a) CB content is 2%; (b) CB content is 3%.
Fig. 11. Effects of sample thickness on the EM wave absorbing properties.
vol.% (a)–(d) EP with 1 mm diameter.
M AN U
Fig. 12. Comparison of calculated and experimental reflectivity of the composites with 3% CB and 0 vol.%–60
Fig. 13. The flexural and compressive strength of the gypsum based composites with 3% CB and different volume
AC C
EP
TE D
concentration of EP.
23 / 37
ACCEPTED MANUSCRIPT Table 1 Some basic performances of the gypsum Final setting
3 d Flexural
3 d compressive
28 d Flexural
28 d compressive
time / min
time / min
strength / MPa
strength / MPa
strength / MPa
strength / MPa
10
30
4.2
8.9
7.1
18.8
Table 2 Chemical compositions of the expanded perlite Component
SiO2
Al2O3
Fe2O3
MgO
CaO
Na2O
K2O
Content range (wt.%)
73.4
13.5
1.2
0.5
1.3
4.2
5.4
Resistivity
Ignition
(ml/100g)
(Ω·cm)
loss
≥260
2.0
≤0.3%
PH
0.5
Iodine adsorption number
BET specific surface
(g/kg)
(m2/g)
≥280
66.5
6-8
M AN U
DBP
MnO2
SC
Table 3 Main properties of the carbon black
RI PT
Initial setting
Table 4 EM wave absorption properties of some representative porous cement based materials and gypsum based materials prepared in this work Porous filler
Cement
Cement
(vol.%)
(mm) EPS
60 vol.%
1 mm
EPS 50 vol.%
3 mm
EPS 50 vol.%
1 mm
EP
60 vol.%
1 mm
EP
AC C
Cement
Diameter
Gypsum
40 vol.%
Thickness
(wt.%)
(mm)
TE D
Cement
Filling ratio
EP
Matrix
Absorbent
1 mm
Frequency range (GHz)
References
(R＜–10 dB)
/
20
12–18
[30]
6 % CB
20
4–5, 7.5–9 and 11–18
[31]
6 % MnO2
15
6.5–7.5
[32]
5 % Graphite
20
14.5–18
[41]
3 % CB
20
2–3, 5–6.5 and 8–18
This work
24 / 37
ACCEPTED MANUSCRIPT (b)
RI PT
(a)
AC C
EP
TE D
M AN U
SC
Fig. 1. Micrograph of the EP and CB particles: (a) SEM image of EP; (b) TEM image of CB.
25 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 2. Schematic diagram of preparation process of the gypsum based composite.
26 / 37
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Fig. 3. Sketch map of the arch reflecting method system.
27 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 4. Graphical representation of the propagation of EM wave inside an absorber.
28 / 37
ACCEPTED MANUSCRIPT
SC
RI PT
(a)
AC C
EP
(c)
TE D
M AN U
(b)
Fig. 5. EM parameters of (a) carbon black, (b) gypsum powders and (c) expanded perlite.
29 / 37
ACCEPTED MANUSCRIPT (a)
RI PT
(b)
Fig. 6. Schematic diagram of the scattering and reflections of incident wave: (a) in a single particle; (b) between
AC C
EP
TE D
M AN U
SC
multiple particles.
30 / 37
ACCEPTED MANUSCRIPT Sample
SC
RI PT
(a)
AC C
EP
(c)
TE D
M AN U
(b)
Fig. 7. The measurement system of waveguide method (a) and the real part (b) and imaginary part (b) of the complex permittivity of the composites.
31 / 37
(b)
(c)
(d)
M AN U
SC
(a)
RI PT
ACCEPTED MANUSCRIPT
(e)
EP
TE D
(f)
Fig. 8. The enhancement of EM wave absorption by the introduction of EP particles, (a)–(e):CB 0%–5 % and EP
AC C
concentration is 40 vol.%.
32 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 9. Effects of EP volume concentration on the EM wave absorbing properties.
33 / 37
ACCEPTED MANUSCRIPT
SC
RI PT
(a)
TE D
M AN U
(b)
Fig. 10. Effects of EP diameters on the EM wave absorbing properties: (a) CB content is 2%; (b) CB content is
AC C
EP
3%.
34 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 11. Effects of sample thickness on the EM wave absorbing properties.
35 / 37
(b)
(c)
(d)
M AN U
SC
(a)
RI PT
ACCEPTED MANUSCRIPT
Fig. 12. Comparison of calculated and experimental reflectivity of the composites with 3% CB and 0 vol.%–60
AC C
EP
TE D
vol.% (a)–(d) EP with 1 mm diameter.
36 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
Fig. 13. The flexural and compressive strength of the gypsum based composites with 3% CB and different volume
AC C
EP
TE D
M AN U
concentration of EP.
37 / 37
S1359-8368(16)30114-7
DOI:
10.1016/j.compositesb.2016.09.014
Reference:
JCOMB 4506
To appear in:
Composites Part B
Received Date: 24 March 2016 Revised Date:
16 June 2016
Accepted Date: 4 September 2016
Please cite this article as: Xie S, Ji Z, Yang Y, Hou G, Wang J, Electromagnetic wave absorption enhancement of carbon black/gypsum based composites filled with expanded perlite, Composites Part B (2016), doi: 10.1016/j.compositesb.2016.09.014. This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT
Electromagnetic wave absorption enhancement of carbon black/gypsum based composites filled with expanded perlite
RI PT
Shuai Xie a, b, Zhijiang Ji a *, Yang Yang a, Guoyan Hou a, Jing Wang a
a. State Key Laboratory of Green Building Materials, China Building Materials
SC
Academy, Beijing 100024, PR China;
b. School of Materials Science and Engineering, Wuhan University of Technology,
M AN U
Wuhan 430070, PR China.
E-mail address: [email protected] (S. Xie), [email protected] (Z.J. Ji), [email protected] (Y. Yang), [email protected] (G.Y.
TE D
Hou), [email protected] (J. Wang)
EP
Corresponding author: Zhijiang Ji
E-mail address: [email protected]
AC C
Tel: +86 010 51167119
Fax: +86 010 51167119
1 / 37
ACCEPTED MANUSCRIPT
Abstract
2
The electromagnetic (EM) wave absorbing carbon black (CB)/gypsum based
3
composites with high wave absorption properties and wide effective bandwidth were
4
prepared by filling expanded perlite (EP) simply. The influences of CB contents, EP
5
volume concentration, EP particle size, and thickness of samples on EM wave
6
absorption were investigated, and the absorption mechanisms were analyzed as well.
7
The results indicate that the wave absorption of the composites can be remarkably
8
enhanced, due to the improvement of impedance matching as well as the single and
9
multiple scattering and refractions caused by EP particles. The reflectivity is lower
10
than –10 dB in the frequency ranges of 2–3, 5–6.5 and 8–18 GHz for the sample with
11
3% CB, when the EP volume concentration and sample thickness are 40 vol.% and 20
12
mm, respectively, with the EP diameter of 1 mm. The prepared composites with low
13
cost and high efficiency can be considered as a promising candidate used in
14
construction engineering for EM wave absorption.
SC
M AN U
TE D
EP
15
RI PT
1
Keywords: A. Hybrid; B. Electrical properties; B. Mechanical properties; Wave
17
absorption (nominated)
18
AC C
16
2 / 37
ACCEPTED MANUSCRIPT 19
1. Introduction Gypsum is an inorganic cementitious material, which is one of the earliest
21
building materials elaborated by mankind and its utilization history can be traced to
22
4000 years ago [1]. Nowadays, gypsum based material is widespread use in the
23
construction industry as its easy extraction and large reserves especially in China.
24
Meanwhile, the gypsum is a traditional finishing material because of its low cost,
25
convenient application and excellent finishing appearance. The gypsum based
26
products also possess the characteristics of light weight, high strength, noise and
27
thermal isolation, as well as inflaming retarding, and all of these properties of gypsum
28
based products have been extensively studied [2-4]. As the increasing uses of
29
household appliances, communication devices, electronic products, and wireless
30
networks, severe electromagnetic (EM) radiation is being generated everywhere. And
31
it has become a serious pollution issue, not only influence the normal operation of
32
electronic devices, but also do harm to human beings’ health [5-7]. Therefore, the
33
demands for developing EM wave absorbing materials with wider absorbing
34
bandwidth and more effective absorption performance used in construction industry
35
are increasing, and so many EM wave absorbing building materials have been
36
developed, such as cement-based materials [8-10], ceramics [11-14], wood-based
37
materials [15,16], etc. However, by now the EM wave absorption properties of
38
gypsum based materials are seldom reported.
AC C
EP
TE D
M AN U
SC
RI PT
20
39
In previous research of the EM wave absorbing materials, both magnetic loss
40
materials and dielectric loss materials are used as the wave absorbing agent. The 3 / 37
ACCEPTED MANUSCRIPT development of EM wave absorbing materials using magnetic loss materials, such as
42
ferrite, carbonyl iron, etc., was widely achieved [17-19]. But there is an obvious
43
weakness of absorption performance in high frequency ranges, as well as a critical
44
weakness of being heavy. The research of dielectric absorbers using dielectric loss
45
materials as absorbing agent indicate that a weight advantage can be achieved
46
compared to the magnetic loss materials [20-23]. And the absorption performance of
47
the nanoscale dielectric loss materials carbon black (CB) and carbon nanotubes
48
(CNTs) is much better [24-26], due to the effects of their smaller size, lager specific
49
surface and more interfaces. However, as a single agent, either CB or CNTs still
50
possesses some disadvantages, such as small absorption peak and narrow effective
51
absorption bandwidth [27,28], because of the impedance mismatching. Thus, based on
52
the impedance matching principle [29], an effective method to decrease the
53
permittivity of the dielectric loss absorber is the introduction of low EM parameters
54
materials.
TE D
M AN U
SC
RI PT
41
Porous materials, such as expanded polystyrene (EP), hollow glass microspheres
56
(HGM) and expanded perlite (EP), etc., have a series of excellent properties such as
57
low density, low EM parameters and high specific surface. It has been reported that
58
the EM wave absorbing properties of the cement-based materials can be improved
59
obviously by filling EP or EPS beads, and the reflectivity of the cement based
60
materials was lower than –10 dB in 8–18 GHz frequency range [30-32]. Therefore, it
61
is an ideal method to improve the impedance matching and EM wave absorption
62
performance by introducing porous materials into matrix. However, investigation into
AC C
EP
55
4 / 37
ACCEPTED MANUSCRIPT 63
the effects of porous materials on the EM parameters and wave absorbing properties
64
of gypsum based composites, as well as the wave absorption mechanisms are still
65
scarce and remain to be explored, which motivates the major objective of this work. In this work, EM wave absorbing gypsum based composites with good
67
absorption properties, a simple process, low density and low cost were fabricated. The
68
economy and practicability of the composites for construction industry must be
69
considered, thus, the CB with lower price was used as absorption agent and the EP
70
particles were introduced into matrix to enhance the EM wave absorption
71
performance. The aim of this work is to investigate the effects of EP on the EM
72
absorption properties of the CB/gypsum based composites, and the impacts on the
73
wave absorbing effectiveness, such as the volume concentration of EP, the diameter of
74
EP and sample thickness, were analyzed in detail. The absorption mechanisms of the
75
gypsum based composites filled with EP particles were discussed as well.
76
2. Materials and methods
77
2.1 Materials
EP
TE D
M AN U
SC
RI PT
66
Gypsum powders were produced by Inner Mongolia Grassland Gypsum Powder
79
Plant, China, and some basic properties are listed in Table 1. Expanded perlite, with
80
the average diameters of 1 mm and 3 mm, were procured from Shanghai LongYuan
81
Industrial Co., Ltd., China. The bulk density of the EP particles is 150 kg/m3, and the
82
chemical compositions are shown in Table 2. Acetylene carbon black was supplied by
83
Tianjin Jinqiushi Chemical Industry Co., Ltd., China, and the main properties are
84
shown in Table 3. The micro-morphologies and structures of expanded perlite and
AC C
78
5 / 37
ACCEPTED MANUSCRIPT carbon black were studied by SEM and TEM, and the images are shown in Fig. 1.
86
Table 1 Some basic performances of the gypsum
87
Table 2 Chemical compositions of the expanded perlite
88
Table 3 Main properties of the carbon black
89
Fig. 1. Micrograph of the EP and CB particles: (a) SEM image of EP; (b) TEM image of CB.
90
2.2 Preparation process of the gypsum based composites
RI PT
85
The main process for preparing the gypsum based composites was displayed in
92
Fig.2. The gypsum powders, CB and deionized water were first mixed in a mixer for
93
about 3 minutes, and then the EP particles were added into the gypsum plaster
94
gradually with the designed volume concentrations, and mixed for another 3 minutes
95
to achieve the uniform distribution of EP particles. Then the prepared plaster was
96
poured into the moulds with the size of 180 mm × 180 mm × 10/15/20 mm (for the
97
measurement of EM wave reflectivity) and 40 mm × 40 mm × 160 mm (for the
98
measurement of flexural and compressive strength). Then the moulds were vibrated to
99
remove air bubbles. The specimens were removed from their moulds after 2 hours and
100
then dried in a constant-temperature dry box with the temperature of 50℃ until their
101
quality are not changed with time.
102
Fig. 2. Schematic diagram of preparation process of the gypsum based composite.
103
2.3 Measurement of properties
AC C
EP
TE D
M AN U
SC
91
104
The morphologies and microstructures of raw materials and prepared composites
105
are characterized by scanning electron microscopy (SEM, Quanta 200) and
106
transmission electron microscopy (TEM, Tecnai F20 ST). The compressive strength 6 / 37
ACCEPTED MANUSCRIPT 107
and flexural strength of the gypsum based composites are tested by a flexural and
108
compressive strength testing machine (TYE-300D). The EM parameters of raw materials are measured by coaxial line method in the
110
frequency range of 2–18 GHz, and the samples for coaxial line method were prepared
111
by paraffin with 50 vol.% powders of testing materials and compressing into
112
cylindrical shaped (φout = 7 mm, φinner = 3.04 mm and 3 mm thickness). The EM
113
parameters of the prepared gypsum based composites are measured by waveguide
114
method only in X-band and Ku-band, because of the limitation of test equipment. And
115
the samples for waveguide method are rectangles with the sizes of 22.9 mm × 10.2
116
mm × 10.0 mm (for X-band) and 15.8 mm × 7.9 mm × 5.0 mm (for Ku-band),
117
respectively. The EM wave reflectivity is measured by arch reflecting method in the
118
frequency ranges of 2–18 GHz, according to the national standard GJB 2038A-2011.
119
The testing system of arch reflecting method is shown in Fig. 3. The test system
120
should be calibrated before measurement, in order to make sure of the accuracy of the
121
testing results.
EP
TE D
M AN U
SC
RI PT
109
The measurement of EM parameters and EM wave reflectivity are launched in
123
the State Key Laboratory of Green Building Materials in Beijing, China. And the test
124
equipment include an Agilent 5234A Vector Network Analyzer, Agilent 85071E
125
testing software, standard horn antennas, 7 mm coaxial airline clamp, X-band and
126
Ku-band waveguide clamps.
127
Fig. 3. Sketch map of the arch reflecting method system.
128
3. Theory analysis
AC C
122
7 / 37
ACCEPTED MANUSCRIPT To obtain an EM wave absorber with excellent absorption performance, there are
130
two essential requirements needed. One is that the absorber should have a good
131
impedance matching to make the incident EM wave transmit into the absorber easily;
132
another is that the absorber should have a good EM wave dissipation capacity. The
133
propagation of EM wave in an absorber is shown in Fig. 4, when EM waves transmit
134
to the surface of the absorber, part of them will be reflected first. Then, some of the
135
incident wave will be absorbed by the absorber, and some remains will transmit back
136
to the free space. In an EM wave absorber, the equation must be satisfied [33]:
SC
M AN U
137
RI PT
129
t+r+a=1
(1)
where t , r and a represent the transmission coefficient, reflection coefficient and
139
absorption coefficient, respectively. Thus, both improving the impedance matching to
140
reduce the reflection coefficient and enhancing the EM loss characteristic to increase
141
the absorption coefficient are reasonable methods to improve the EM wave absorption
142
properties.
143
Fig. 4. Graphical representation of the propagation of EM wave inside an absorber
144
3.1 Improvement of impedance matching
146 147
EP
AC C
145
TE D
138
As is known that in an optimal situation of impedance matching, the EM
parameters of wave absorber should meet the following equation [29]: ε' = µ', ε" = µ"
(2)
148
where ε', µ', ε" and µ" are the real and imaginary parts of permittivity and permeability,
149
respectively. Therefore, in a dielectric loss absorber, the impedance matching
150
properties can be improved by decreasing the permittivity of the absorber to make the 8 / 37
ACCEPTED MANUSCRIPT 151
values of ε' and ε" close to µ' and µ". The EM parameters of the gypsum, CB and EP are shown in Fig. 5, from which
153
it can be observed that all of the raw materials are non-magnetic loss materials. The ε'
154
and ε" of CB are in the ranges of 38–180 and 40–125, respectively, in the frequency
155
range of 2–18 GHz, indicating that the CB is a kind of strong dielectric loss material.
156
The ε' and ε" of gypsum materials are approximate 5.5 and 0, respectively, in 2–18
157
GHz, implying the insignificant dielectric loss for EM wave. It can be predicted based
158
on the effective medium theory [34,35] that the permittivity of the gypsum based
159
composites can be increased obviously by introducing CB, leading to a serious
160
impedance mismatching. However, the introduction of the EP particles with much
161
lower permittivity (ε' ≈ 2.2，ε" ≈ 0) will reduce the permittivity of the composites, and
162
the impedance matching properties can be improved. In addition, more space network
163
structures will be formed by the porous EP particles in the composites, providing
164
more propagation path for the incident wave, which is beneficial to the improvement
165
of impedance matching as well [30,31].
166
Fig. 5. EM parameters of (a) carbon black, (b) gypsum powders and (c) expanded perlite
167
3.2 Enhancement of EM loss characteristic
SC
M AN U
TE D
EP
AC C
168
RI PT
152
Before introducing EP particles, the CB/gypsum based composites absorb the
169
incident wave only by the tunnel effect, leakage conductance effect, damping
170
vibration, and polarization effect of the CB particles [36-38]. When EP particles are
171
introduced, the complex refractions and scattering of the EP particles will play an
172
important role in wave attenuation. The propagation of the incident wave in a single 9 / 37
ACCEPTED MANUSCRIPT particle is shown in Fig. 6(a). When EM wave propagates in the EP filled composites,
174
the EM wave attenuation of a single particle Iatt includes the absorption attenuation of
175
reflected wave Iab and scattering attenuation of scattered wave Isc, and they satisfied
176
the equation Iatt = Iab + Isc [39].
177
Fig. 6. Schematic diagram of the scattering and reflections of incident wave: (a) in a single particle; (b) between
178
multiple particles.
RI PT
173
Moreover, the multiple scattering and reflections between the particles, which is
180
displayed in Fig. 6(b), must be taken into account. On the one hand, the multiple
181
scattering can increase wave attenuation by the particles; on the other hand, the
182
multiple reflections between particles also increase the propagation length of incident
183
wave in the composite [40], leading to the enhancement of the attenuation by the
184
CB/gypsum matrix.
TE D
M AN U
SC
179
From the above analysis, it can be predicted that the impedance matching
186
property and wave dissipation capacity of CB/gypsum based composite could be
187
improved by introducing EP particles, leading to the enhancement of EM wave
188
absorption. And the effects of EP particles on EM wave absorption are discussed in
189
detail in the following sections.
190
4. Results and discussion
191
4.1 Electromagnetic parameters
AC C
EP
185
192
The complex permittivity of the EP filled gypsum based composites was
193
investigated by waveguide method in 8.2–18 GHz frequency range. The testing
194
system and the measurement results are shown in Fig. 7. The CB mass fraction of the 10 / 37
ACCEPTED MANUSCRIPT 195
test samples is 3%, and the average diameter of the introduced EP particles is 1 mm. As seen from Fig. 7(b) and (c), both the real part ε' and the imaginary part ε" of
197
the complex permittivity can be reduced obviously by introducing EP, and with the
198
increase of EP volume concentration, the values of ε' and ε" decrease constantly.
199
According to Eq (2), for the non-magnetic loss materials, the impedance matching
200
performance can be improved by the decrease of complex permittivity. Therefore, the
201
introduction of EP particles can improve the impedance matching of CB/gypsum
202
based composites assuredly. And the EP volume concentration also plays an important
203
role in the improvement of impedance matching.
204
Fig. 7. The measurement system of waveguide method (a), the real part (b) and imaginary part (b) of the complex
205
permittivity of the composites.
206
4.2 Electromagnetic wave absorption properties
207
4.2.1
TE D
M AN U
SC
RI PT
196
Enhancement of wave absorption properties The EM wave absorption performance of the CB/gypsum composites and EP
209
filled CB/gypsum composites were measured by arch reflecting method as illustrated
210
in Fig. 8. The –10 dB reflectivity means that the absorber can attenuate 90% of the
211
incident wave. The EP particle diameter of the following samples is 1 mm, and the
212
sample thickness is 20 mm.
AC C
213
EP
208
It can be seen from the reflectivity curves shown in Fig. 8 that the EM wave
214
absorbing properties of the gypsum composites can be obviously enhanced by the
215
introduction of EP particles. Meanwhile, the variation of CB contents also plays an
216
important role in the enhancement of wave absorption. When the composite is 11 / 37
ACCEPTED MANUSCRIPT unfilled CB, the enhancement of wave absorption by introducing EP particles is
218
insignificant as shown in Fig. 8 (a). With the increasing of CB content, the effect of
219
EP particles on the enhancement of wave absorption becomes more and more
220
significant. When the composites with 1% or 2% CB as shown in Fig. 8 (b) and (c),
221
only the lowest reflectivity decreases. With the continual increase of CB content, the
222
reflectivity of the EP filled composites becomes lower than those without EP particles
223
in the whole frequency range of 2–18 GHz, which can be observed in Fig. 8 (d)–(f).
224
For the composite filled with 3% CB and 40 vol.% EP, a minimum reflectivity of –15
225
dB at 2 GHz and a wide effective bandwidth (reflectivity less than –10 dB) of 12.5
226
GHz (2–3, 5–6.5 and 8–18 GHz) can be achieved. Hence, the CB/gypsum based
227
composites with excellent absorption properties was really obtained by introducing
228
EP particles. The enhancement of wave absorption by introducing EP particles can be
229
attributed to the improvement of impedance matching and EM dissipation capacity
230
[41]. The decrease of the permittivity can improve the impedance matching between
231
the composite and free space based on Eq. (2). In addition, new EM wave attenuation
232
path such as multiple scattering and reflections has been provided by EP particles,
233
causing the promotion of EM wave dissipation capacity.
SC
M AN U
TE D
EP
AC C
234
RI PT
217
It is worth noting that the wave absorbing properties of the composites with 4%
235
or 5% CB will be weakened, whose minimum reflectivity even cannot reach –10 dB.
236
However, the effect of EP particles on the enhancement of wave absorption is still
237
obvious. The skin depth ∆ of the incident wave can be expressed as [42].
238
∆ = 2 π 2 f 2 µε "
(3) 12 / 37
ACCEPTED MANUSCRIPT where µ is the permeability of absorbing materials; ε" is the imaginary part of
240
absorbing materials; and f is the frequency of incident wave. The permittivity ε″ of the
241
composite can be increased when CB content increases, leading to the decrease of the
242
skin depth, according to Eq. (3). When the skin depth is less than the thickness of the
243
composite, the incident wave cannot penetrate the composite and the propagation
244
length becomes shorter, resulting in the decrease of interference offset and wave
245
attenuation [9]. That is the main reason for the weak absorption peak and poor
246
absorption performance of the composites with 4% or 5% CB as illustrated in Fig. 8
247
(e) and (f).
248
Fig. 8. The enhancement of EM wave absorption by the introduction of EP particles, (a)–(f): CB 0%–5 % and EP
249
concentration is 40 vol.%.
M AN U
SC
RI PT
239
The EM wave absorption properties of some representative cement based
251
absorbing composites filled with porous fillers are summarized in Table 4, and
252
comparing with the experimental results of this work. It can be discovered visibly that
253
the effective bandwidth of the prepared composite in this work is wider than the EP or
254
EPS filled cement based materials, due to the lower permittivity and more lacunose
255
interior structure of gypsum composites which is more beneficial to impedance
256
matching and EM wave transmission [43].
257
Table 4 EM wave absorption properties of some representative porous cement based materials and gypsum based
258
materials prepared in this work
259
4.2.2
260
AC C
EP
TE D
250
Effect of the EP volume concentration
Fig. 9 indicates the effects of EP volume concentration on the EM wave 13 / 37
ACCEPTED MANUSCRIPT absorption performance of the CB/gypsum based composites, from which it can be
262
seen that the wave absorption increases with the increase of EP volume concentration,
263
but it does not increase monotonically. It can be discovered that the composite filled
264
with 40 vol.% EP particles exhibits optimal wave absorption performance. The
265
numbers of EP particles increase with the increase of EP volume concentration, which
266
lead to the increase of the multiple scattering and reflections between EP particles.
267
Besides, the impedance matching property between the composite and free space
268
improved by increasing EP volume concentration, and the incident wave could
269
transmit into the composite much easier. Therefore, the EM wave absorption increases
270
with the EP volume concentration.
M AN U
SC
RI PT
261
However, the further introduction of EP particles will decrease wave absorption
272
as shown in Fig. 9. The decrease of the permittivity, which can lead to a reduction of
273
EM dissipation capacity, may be the main reason for the decrease of wave absorption.
274
Fig. 9. Effects of EP volume concentration on the EM wave absorbing properties.
275
4.2.3
TE D
271
EP
Effect of the EP diameter The effects of EP diameters on the EM wave absorption properties are shown in
277
Fig. 10, from which it can be observed that the filling of 1 mm EP particles is more
278
beneficial to wave absorption. As to the composite with 2 % CB, lower peak values of
279
reflectivity can be obtained by introducing 1 mm EP particles. As to the composites
280
with 3 % CB, the reflectivity of the composite filled with 1 mm EP is lower than that
281
filled with 3 mm EP in the whole range of 2–18 GHz. For the gypsum based
282
composites filled with EP particles, in fact, the decrease of the EP diameter is the
AC C
276
14 / 37
ACCEPTED MANUSCRIPT increase of the particle numbers at the same EP volume concentration, which provides
284
more opportunities for scattering and multiple scattering and refractions of the
285
incident wave. So the EM wave absorption performance of the gypsum composite can
286
be increased visibly by filling EP particles with smaller diameters.
287
Fig. 10. Effects of EP diameters on the EM wave absorbing properties: (a) CB content is 2%; (b) CB content is
288
3%.
289
4.2.4
SC
Effect of the sample thickness
RI PT
283
Fig. 11 presents the effect of thickness variation on the wave absorption of the
291
composites, and the samples for measurement are filled with 3% CB and 40 vol.% EP.
292
The experimental results indicate that the intensity of the reflectivity peak is sensitive
293
to the thickness, and the number of peaks increases with the increase of sample
294
thickness. Moreover, the shape of the reflectivity curve becomes smoother with the
295
increase of sample thickness. The variation of the reflectivity peaks of the samples
296
with different thickness can be explained by the interference theory [44]:
TE D
f =
( 2n + 1) c n=0, 1, 2, 3…
EP
297
M AN U
290
4d ε r µ r
(4)
where f is the frequency of incident wave; n is the number of peaks; εr and µr are the
299
complex permittivity and complex permeability of the sample, respectively; c is the
300
velocity of EM wave in free space; and d is the thickness. From Eq. (4), it can be seen
301
that the increase of thickness d could lead to the increase of the number of peaks,
302
when εr and µr are invariable. Simultaneously, the increase of thickness makes the
303
possibility of incident wave penetrating the sample becomes smaller, decreasing the
304
interference offset of the reflection wave between the top and the bottom of the
AC C
298
15 / 37
ACCEPTED MANUSCRIPT 305
sample [9]. Therefore, the reflectivity curves tend to be smoother as the increase of
306
sample thickness.
307
Fig. 11. Effects of sample thickness on the EM wave absorbing properties.
308
4.2.5
311
RI PT
310
According to the transmission line theory and impedance matching principle, the EM wave reflectivity can be expressed as follows [45-47]:
R = 20 log
Z in − Z 0 µ0 µ r j 2π fd tanh , Z in = ⋅ ε 0ε r µ 0 µ r Z in + Z 0 ε 0ε r c
SC
309
Comparison of calculated and experimental wave absorption properties
(5)
where Zin is the input impedance of the absorber; εr = ε' – jε" and µr = µ' – jµ" are the
313
complex permittivity and complex permeability of the absorber, respectively; ε0 and
314
µ0 are the permittivity and permeability of free space, respectively; c is the velocity of
315
EM wave in free space; f is the frequency of incident EM waves; and d is the
316
thickness of the absorber. According to Eq. (5) and the measured EM parameters
317
shown in Fig. 7, the EM wave absorption of several samples (with CB 3% and EP
318
particles 0–60 vol.%) was calculated in 8.2–18 GHz frequency range.
EP
TE D
M AN U
312
Fig. 12 reveals the differences between calculated and experimental reflectivity
320
values, from which it can be discovered that the errors between the calculated and
321
experimental reflectivity values cannot be avoided. It is obvious that the experimental
322
reflectivity values are lower than the calculated results in the whole X and Ku band,
323
when EP particles were introduced into the composites. The main reason for this
324
phenomenon is that the effects of multiple scattering and reflections on EM wave
325
reflectivity are not considered in the calculated equations. In addition, it can be seen
326
that the vibration of the calculated curves is larger compared with those experimental
AC C
319
16 / 37
ACCEPTED MANUSCRIPT curves, which can be attributed to the large volatility of the measured EM parameters
328
values as shown in Fig. 7. However, it is can be discovered from Fig. 12 that the
329
variation trend of the calculated and experimental results of each sample are basically
330
coincident, and the improvement of wave absorption by introduction of EP can be
331
observed clearly.
332
Fig. 12. Comparison of calculated and experimental reflectivity of the composites with 3% CB and 0 vol.%–60
333
vol.% (a)–(d) EP with 1 mm diameter.
334
4.3 Mechanical properties
M AN U
SC
RI PT
327
The effects of EP particles on the flexural and compressive strength were
336
investigated as well, and the experimental results are shown in Fig. 13. It can be
337
discovered easily from Fig. 13 that both the flexural strength and compressive
338
strength are reduced by the EP introduction, when the composite with 20 vol.% EP,
339
the flexural strength and compressive strength are 4.6143 and 8.4684 MPa,
340
respectively, which is approximately 15 % and 30 % lower than the composite
341
without EP. And substantial reductions in the flexural and compressive strength were
342
obtained also for the higher EP contents. When the EP content is 60 vol.%, the
343
flexural and compressive strength are only 2.6347 and 5.0437 MPa, respectively. The
344
compressive strength can be reduced due to the low strength and specific gravity of
345
EP [48]. Also, the adhesive performance between gypsum plaster is reduced by filling
346
EP, which can cause the reduction of flexural strength. The decrease of mechanical
347
properties is an important problem to be resolved in our following work.
348
Fig. 13. The flexural and compressive strength of the gypsum based composites with 3% CB and different volume
AC C
EP
TE D
335
17 / 37
ACCEPTED MANUSCRIPT 349
concentration of EP.
350
5 Conclusions The EM wave absorption performance of CB/gypsum based composite has been
352
remarkably enhanced through introducing expanded perlite, owing to the
353
improvement of impedance matching, as well as the single and multiple scattering and
354
refractions caused by EP particles. The EM absorption properties increase with the
355
increase of CB contents and EP volume concentration, but there is an optimal
356
concentration for CB and EP, respectively. Moreover, the smaller EP diameters and
357
larger thickness are beneficial to the enhancement of wave absorption. With an EP
358
volume concentration of 40 vol.%, CB content of 3 % and EP diameter of 1 mm, this
359
composite with a thickness of 20 mm exhibits the best wave absorption performance.
360
The effective bandwidth for –10 dB can be 12.5 GHz (2–3, 5–6.5 and 8–18 GHz),
361
which is wider than most of the reported cement composites filled with porous
362
aggregates. However, the flexural and compressive strength were reduced due to the
363
filling of EP, and this issue will be resolved in our following works.
364
Acknowledgements
SC
M AN U
TE D
EP
AC C
365
RI PT
351
This work was supported by the National Science & Technology Pillar Program during the
366
12th Five-year Plan Period of P. R. China (No. 2014BAB15B02-02).
367
References
368
[1] Yu QL, Brouwers HJH. Development of a self-compacting gypsum–based lightweight
369 370 371
composite. Cem Concr Compos 2012; 34: 1033–43. [2] Zhou TY, Darkwa J, Kokogiannakis G. Thermal evaluation of laminated composite phase change material gypsum board under dynamic conditions. Renew Energ 2015; 78: 448–56.
372
[3] Raghavendra T, Udayashankar BC. Engineering properties of controlled low strength
373
materials using fly ash and waste gypsum wall boards. Constr Build Mater 2015; 101: 18 / 37
ACCEPTED MANUSCRIPT 374 375 376
448–57. [4] Keerthan P, Mahendran M. Numerical studies of gypsum plasterboard panels under standard fire conditions. Fire Safety J 2012; 53: 105–19.
377
[5] Zhang J, Xiao P, Zhou W, Hong W, Luo H. Preparation and microwave absorbing properties
378
of carbon fibers/epoxy composites with grid structure. J Mater Sci: Mater Electr 2015; 26:
379
651–58. [6] Gogoi JP, Bhattacharyya NS, James Raju KC. Synthesis and microwave characterization of
381
expanded graphite/novolac phenolic resin composite for microwave absorber applications.
382
Composites: Part B 2011; 42: 1291-97.
RI PT
380
[7] Gogoi JP, Bhattacharyya NS, Bhattacharyya S. Single layer microwave absorber based on
384
expanded graphite-novolac phenolic resin composite for X-band applications. Composites:
385
Part B 2014; 58: 518-23.
SC
383
[8] Nam IW, Lee HK. Synergistic effect of MWNT/fly ash incorporation on the EMI
387
shielding/absorbing characteristics of cementitious materials. Constr Build Mater 2016; 115:
388
651–61.
389 390
M AN U
386
[9] Wang BM, Guo ZQ, Han Y. Electromagnetic wave absorbing properties of multi–walled carbon nanotube/cement composites. Constr Build Mater 2013; 46: 98–103.
391
[10] Li KZ, Wang C, Li HJ, Li XT, Ouyang HB, Wei J. Effect of chemical vapor deposition
392
treatment of carbon fibers on the reflectivity of carbon fiber-reinforced cement-based
393
composites. Compos Sci Technol, 2008; 68: 1105–14.
395
[11] Yin XW, Kong L, Zhang LT, Cheng LF, Travitzky N, Greil P. Electromagnetic properties of
TE D
394
Si–C–N based ceramics and composites. Int Mater Rev 2014; 59: 326-55. [12] Han MK, Yin XW, Duan WY, Ren S, Zhang LT, Cheng LF. Hierarchical graphene/SiC
397
nanowire networks in polymer-derived ceramics with enhanced electromagnetic wave
398
absorbing capability. J Eur Ceram Soc 2016; 36: 2695-703.
EP
396
[13] Bantsis G, Sikalidis C, Betsiou M, Yioultsis T, Xenos T. Electromagnetic absorption,
400
reflection and interference shielding in X–band frequency range of low cost ceramic building
401
bricks and sandwich type ceramic tiles mill scale waste as an admixture. Ceram Int 2011; 37:
402
AC C
399
3535–45.
403
[14] Yao R, Liao SY, Dai CL, Liu YC, Chen XY, Zheng F. Preparation and characterization of
404
novel glass–ceramic tile with microwave absorption properties from iron ore tailings. J Magn
405
Magn Mater 2015; 378: 367–75.
406
[15] Oka H, Kataoka Y, Osada H, Aruga Y, Izumida F. Experimental study on electromagnetic
407
wave absorbing control of coating–type magnetic wood using a grooving process. J Magn
408
Magn Mater 2007; 310: e1028–29.
409
[16] Oka H, Terui M, Osada H, Sekino N, Namizaki Y, Dawson FP. Electromagnetic wave
410
absorption characteristics adjustment method of recycled powder–type magnetic wood for
411
use as a building material. IEEE Trans Magn 2012; 48: 3496–500.
412
[17] Yang
RG.
Electromagnetic
properties
and
microwave
absorption
properties
of
19 / 37
ACCEPTED MANUSCRIPT 413
BaTiO3–carbonyl iron composites in S and C bands. J Magn Magn Mater 2011; 323:
414
1805–10.
415 416
[18] Feng YB, Qiu T, Shen CY, Li XY. Electromagnetic and absorption properties of carbonyl iron/rubber radar absorbing materials. IEEE Trans Magn, 2006; 3: 463–68. [19] Ye JW, Liu Y, Zhang J, Chen XF, Yao MY. Preparation and electromagnetic wave absorption
418
properties of Sm2O3/α–Fe/Sm2Fe17Nx composites. J Magn Magn Mater 2013; 335: 32–35.
419
[20] Oh JH, Oh KS, Kim CG, Hong CS. Design of radar absorbing structures using glass/epoxy
420
composite containing carbon black in X–band frequency ranges. Composites: Part B 2004;
421
35: 49–56.
RI PT
417
[21] Du YC, Liu T, Yu B, Gao HB, Xu P, Wang JY, Wang XH, Han XJ. The electromagnetic
423
properties and microwave absorption of mesoporous carbon. Mater Chem Phys 2012; 135:
424
884–91.
SC
422
[22] Han MK, Yin XW, Kong L, Li M, Duan WY, Zhang LT, Cheng LF. Graphene-wrapped ZnO
426
hollow spheres with enhanced electromagnetic wave absorption properties. J Mater Chem A
427
2014; 2: 16403–09.
M AN U
425
428
[23] Han MK, Yin XW, Ren S, Duan WY, Zhang LT, Cheng LF. Core/shell structured C/ZnO
429
nanoparticles composites for effective electromagnetic wave absorption. RSC Adv 2016; 6:
430
6467-74.
[24] Micheli D, Apollo C, Pastore R, Marchetti M. X–Band microwave characterization of
432
carbon–based nanocomposite material, absorption capability comparison and RAS design
433
simulation. Compos Sci Technol 2010; 70: 400–9.
TE D
431
[25] Kim JB, Lee SK, Kim CG. Comparison study on the effect of carbon nano materials for
435
single–layer microwave absorbers in X–band. Compos Sci Technol 2008; 68: 2909–16.
436
[26] Yang QX, Liu L, Hui D, Chipara M. Microstructure, electrical conductivity and microwave
437
absorption properties of γ-FeNi decorated carbon nanotube composites. Composites: Part B
438
2016; 87: 256–62.
440
[27] Liu XX, Zhang ZY, Wu YP. Absorption properties of carbon black/silicon carbide microwave absorbers. Composites: part B 2011; 42: 326–29.
AC C
439
EP
434
441
[28] Fan ZJ, Luo GH, Zhang ZF, Zhou L, Wei F. Electromagnetic and microwave absorbing
442
properties of multi–walled carbon nanotubes/polymer composites. Mater Sci Eng B 2006;
443
132: 85–9.
444
[29] Zhang ZL, Ji ZJ, Duan YP, Gu SC, Guo JB. The superior electromagnetic properties of
445
carbonyl–iron/Fe91.2Si3.1P2.9Sb2.8 composites powder and impedance matching. J Mater Sci:
446
Mater Electr 2013; 24: 968–73.
447 448 449 450 451
[30] Guan HT, Liu SH, Duan YP. Investigation of the electromagnetic characteristics of cement based composites filled with EPS. Cem Concr Compos 2007; 28: 49–54. [31] Li BY, Duan YP, Zhang YF. Electromagnetic wave absorbing properties of cement–based composites filled with porous materials. Mater Des 2011; 32: 3017–20. [32] Li BY, Duan YP, Liu SH. The electromagnetic characteristics of fly ash and absorbing 20 / 37
ACCEPTED MANUSCRIPT 452
properties of cement–based composites using fly ash as cement replacement. Constr Build
453
Mater 2012; 27: 184–88.
455 456 457 458 459 460 461
[33] Musil J, Zacek F. Microwave Measurements of Complex Permittivity by Free Space Methods and Their Applications. Elsevier, New York, 1986. [34] Zhang H, Shen YQ, Xu YC, Zhu HY, Lei M. Effective medium theory for two-dimensional random media composed of core-shell cylinders. Opt Commun 2013; 306: 9–16. [35] Vincenti MA, Ceglia D. de. Effective medium theories, in: Haus J (Eds.), Fundamentals and
RI PT
454
Applications of Nanophotonics, Woodhead Publishing, 2016: 211-32.
[36] Wang M, Duan YP, Liu SH, Li XG, Ji ZJ. Absorption properties of carbonyl–iron/carbon black double–layer microwave absorbers. J Magn Magn Mater 2009; 321: 3442–46.
[37] Vinayasree S, Soloman MA, Sunny V, Mohanan P, Kurian P, Anantharaman MR. A
463
microwave absorber based on strontium ferrite–carbon black–nitrile rubber for S and X–band
464
applications. Compos Sci Tech 2013; 82: 69–75.
SC
462
[38] A. Al-Ghamdi A, A. A l-Hartomy O, R. Al-Solamy F, Dishovsky N, Malinova P, Atanasova G,
466
Atanasov N. Conductive carbon black/magnetite hybrid fillers in microwave absorbing
467
composites based on natural rubber. Composites: Part B 2016; 96: 231-41.
469 470 471 472 473
[39] Duan YP, Liu SH, Wen B, Guan HT, Wang GQ. A discrete slab absorber: absorption efficiency and theory analysis. J Compos Mater 2006; 20: 1841–51. [40] Guan HT, Liu SH, Duan YP. Expanded polystyrene as an admixture in cement–based composites for electromagnetic absorbing. J Mater Eng Perform 2007; 16: 68–72. [41] Hu SG, Tian K, Ding QJ. Design and test of new cement based microwave absorbing
TE D
468
M AN U
465
materials. ISAPE 2008. 8th International Symposium 2–5 Nov. 2008: pp956–59. [42] Idris FM, Hashim M, Abbas Z, Ismail I, Nazlan R, Ibrahim IR. Recent developments of smart
475
electromagnetic absorbers based polymer–composites at gigahertz frequencies. J Magn Magn
476
Mater 2016; 405: 197–208.
478 479 480 481 482 483 484 485
[43] Zhang XZ, Sun W. Microwave absorbing properties of double–layer cementitious composites containing Mn–Zn ferrite. Cem Concr Compos 2010; 32: 726–30. [44] Xie S, Yang Y, Hou GY, Wang J, Ji ZJ. Development of layer structured wave absorbing
AC C
477
EP
474
mineral wool boards for indoor electromagnetic radiation protection. J Build Eng 2016; 5: 79–85.
[45] Zou CW, Yao YD, Wei ND, Gong YC, Fu WD, et al. Electromagnetic wave absorption properties of mesoporous Fe3O4/C nanocomposites. Composites Part: B 2015; 77: 209–14.
[46] Li WP , Zhu LQ, Gu J, Liu HC. Microwave absorption properties of fabric coated absorbing material using modified carbonyl iron power. Composites: Part B 2011; 42: 626–30.
486
[47] Shan LM, Chen XN, Tian X, Chen JJ, Zhou ZW, Jiang M, Xu XL, Hui D. Fabrication of
487
polypyrrole/nano-exfoliated graphite composites by in situ intercalation polymerization and
488
their microwave absorption properties. Composites: Part B 2015; 73: 181-7.
489 490
[48] Oktaya H, Yumrutaşb R, Akpolatb A. Mechanical and thermophysical properties of lightweight aggregate concretes. Constr Build Mater 2015; 96: 217–25. 21 / 37
ACCEPTED MANUSCRIPT Table Captions Table 1 Some basic performances of the gypsum Table 2 Chemical compositions of the expanded perlite Table 3 Main properties of the carbon black Table 4 EM wave absorption properties of some representative porous cement based materials and gypsum based
AC C
EP
TE D
M AN U
SC
RI PT
materials prepared in this work
22 / 37
ACCEPTED MANUSCRIPT Figure Captions Fig. 1. Micrograph of the EP and CB particles: (a) SEM image of EP; (b) TEM image of CB. Fig. 2. Schematic diagram of preparation process of the gypsum based composite. Fig. 3. Sketch map of the arch reflecting method system. Fig. 4. Graphical representation of the propagation of EM wave inside an absorber Fig. 5. EM parameters of (a) carbon black, (b) gypsum powders and (c) expanded perlite
multiple particles.
RI PT
Fig. 6. Schematic diagram of the scattering and reflections of incident wave: (a) in a single particle; (b) between
Fig. 7. The measurement system of waveguide method (a), the real part (b) and imaginary part (b) of the complex permittivity of the composites.
Fig. 8. The enhancement of EM wave absorption by the introduction of EP particles, (a)–(e):CB 0%–5 % and EP concentration is 40 vol.%.
SC
Fig. 9. Effects of EP volume concentration on the EM wave absorbing properties.
Fig. 10. Effects of EP diameters on the EM wave absorbing properties: (a) CB content is 2%; (b) CB content is 3%.
Fig. 11. Effects of sample thickness on the EM wave absorbing properties.
vol.% (a)–(d) EP with 1 mm diameter.
M AN U
Fig. 12. Comparison of calculated and experimental reflectivity of the composites with 3% CB and 0 vol.%–60
Fig. 13. The flexural and compressive strength of the gypsum based composites with 3% CB and different volume
AC C
EP
TE D
concentration of EP.
23 / 37
ACCEPTED MANUSCRIPT Table 1 Some basic performances of the gypsum Final setting
3 d Flexural
3 d compressive
28 d Flexural
28 d compressive
time / min
time / min
strength / MPa
strength / MPa
strength / MPa
strength / MPa
10
30
4.2
8.9
7.1
18.8
Table 2 Chemical compositions of the expanded perlite Component
SiO2
Al2O3
Fe2O3
MgO
CaO
Na2O
K2O
Content range (wt.%)
73.4
13.5
1.2
0.5
1.3
4.2
5.4
Resistivity
Ignition
(ml/100g)
(Ω·cm)
loss
≥260
2.0
≤0.3%
PH
0.5
Iodine adsorption number
BET specific surface
(g/kg)
(m2/g)
≥280
66.5
6-8
M AN U
DBP
MnO2
SC
Table 3 Main properties of the carbon black
RI PT
Initial setting
Table 4 EM wave absorption properties of some representative porous cement based materials and gypsum based materials prepared in this work Porous filler
Cement
Cement
(vol.%)
(mm) EPS
60 vol.%
1 mm
EPS 50 vol.%
3 mm
EPS 50 vol.%
1 mm
EP
60 vol.%
1 mm
EP
AC C
Cement
Diameter
Gypsum
40 vol.%
Thickness
(wt.%)
(mm)
TE D
Cement
Filling ratio
EP
Matrix
Absorbent
1 mm
Frequency range (GHz)
References
(R＜–10 dB)
/
20
12–18
[30]
6 % CB
20
4–5, 7.5–9 and 11–18
[31]
6 % MnO2
15
6.5–7.5
[32]
5 % Graphite
20
14.5–18
[41]
3 % CB
20
2–3, 5–6.5 and 8–18
This work
24 / 37
ACCEPTED MANUSCRIPT (b)
RI PT
(a)
AC C
EP
TE D
M AN U
SC
Fig. 1. Micrograph of the EP and CB particles: (a) SEM image of EP; (b) TEM image of CB.
25 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 2. Schematic diagram of preparation process of the gypsum based composite.
26 / 37
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
SC
Fig. 3. Sketch map of the arch reflecting method system.
27 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 4. Graphical representation of the propagation of EM wave inside an absorber.
28 / 37
ACCEPTED MANUSCRIPT
SC
RI PT
(a)
AC C
EP
(c)
TE D
M AN U
(b)
Fig. 5. EM parameters of (a) carbon black, (b) gypsum powders and (c) expanded perlite.
29 / 37
ACCEPTED MANUSCRIPT (a)
RI PT
(b)
Fig. 6. Schematic diagram of the scattering and reflections of incident wave: (a) in a single particle; (b) between
AC C
EP
TE D
M AN U
SC
multiple particles.
30 / 37
ACCEPTED MANUSCRIPT Sample
SC
RI PT
(a)
AC C
EP
(c)
TE D
M AN U
(b)
Fig. 7. The measurement system of waveguide method (a) and the real part (b) and imaginary part (b) of the complex permittivity of the composites.
31 / 37
(b)
(c)
(d)
M AN U
SC
(a)
RI PT
ACCEPTED MANUSCRIPT
(e)
EP
TE D
(f)
Fig. 8. The enhancement of EM wave absorption by the introduction of EP particles, (a)–(e):CB 0%–5 % and EP
AC C
concentration is 40 vol.%.
32 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 9. Effects of EP volume concentration on the EM wave absorbing properties.
33 / 37
ACCEPTED MANUSCRIPT
SC
RI PT
(a)
TE D
M AN U
(b)
Fig. 10. Effects of EP diameters on the EM wave absorbing properties: (a) CB content is 2%; (b) CB content is
AC C
EP
3%.
34 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
AC C
EP
TE D
M AN U
Fig. 11. Effects of sample thickness on the EM wave absorbing properties.
35 / 37
(b)
(c)
(d)
M AN U
SC
(a)
RI PT
ACCEPTED MANUSCRIPT
Fig. 12. Comparison of calculated and experimental reflectivity of the composites with 3% CB and 0 vol.%–60
AC C
EP
TE D
vol.% (a)–(d) EP with 1 mm diameter.
36 / 37
SC
RI PT
ACCEPTED MANUSCRIPT
Fig. 13. The flexural and compressive strength of the gypsum based composites with 3% CB and different volume
AC C
EP
TE D
M AN U
concentration of EP.
37 / 37