Reduced Graphene ... - ACS Publications

Subscriber access provided by - Access paid by the | UCSB Libraries

Article

Synthesis of silanized MoS2/ Reduced Graphene Oxide for Strong Radar Wave Absorption Jing Ran, Lixiang Shen, Li Zhong, and Heqing Fu Ind. Eng. Chem. Res., Just Accepted Manuscript • DOI: 10.1021/acs.iecr.7b02721 • Publication Date (Web): 31 Aug 2017 Downloaded from http://pubs.acs.org on September 3, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Industrial & Engineering Chemistry Research is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Industrial & Engineering Chemistry Research

Synthesis of silanized MoS2/ Reduced Graphene Oxide for Strong Radar Wave Absorption Jing Ran

Lixiang Shen

Li Zhong Heqing Fu*

School of Chemistry and Chemical Engineering, South China University of Technology, Guangzhou, 510640, China *Corresponding author; E-mail address: [email protected]

Abstract: Special materials for radar wave absorption (RWA) and stealth camouflage techniques are desired due to their widespread applications in the military field. In this paper, silanized MoS2 (M/MoS2)/reduced graphene oxidde (rGO) nanosheets were synthesized via ultrasonic and graft method. The Complex permittivity, Cole-Cole plots and RL curve and 3D RL plots indicate that the nanosheets have a remarkable absorption properties. When the content of (M/MoS2)/rGO was 18 wt%, (M/MoS2)/rGO -wax composites exhibited an effective radar absorption bandwidth of 5.81 GHz at the thickness 2.5 mm and a maximum reflection loss (RL) of -49.7 dB. (M/MoS2)/ rGO composites could be used as promising materials for RWA and broad absorption properties.

Keywords: Radar wave absorption; reflection loss; silanized MoS2; reduced graphene oxide Insert For Table of Contents Only

1. Introduction Stealth technology has become an efficient approach for the aircraft protection

ACS Paragon Plus Environment


1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

against attack. Radar wave absorption ( RWA ) materials play a fundamental role in its stealth and shielding technology. In the recent years, scientists had paid attention to the study of the RWA materials, novel nanoporous carbon derived from metal-organic frameworks with tunable electromagnetic wave absorption capabilities1. In order to improve RWA performance, some new composites, such as ZnO, CuS, Bi2S3, Fe3O4, α-MnO2, SiC, TiO2, Fe3O4 / TiO2 and ZnO / Fe2-4 were developed. However, their addition amount is too high. Therefore, it is necessary to study new absorbing materials, especially Permittivity regulating strategy to achieve high-performance electromagnetic wave absorbers with compatibility of impedance matching and energy conservation, those absorbing materials with wide operating frequency band, strong absorption ability, low density, high thermal stability and superior anti-oxidative ability.5 Recently, many scientists study radar wave absorption materials based on pure graphene oxide (GO) and reduced graphene oxide (rGO). Compared with other absorption materials, rGO has more prominent intrinsic physical and chemical properties, including room-temperature electron mobility, theoretical specific surface area and high chemical stability6. rGO can be used as an efficient absorber due to its unique electrical and magnetic performance in a broad bandwidth and sufficient electromagnetic absorption. Obviously, pristine rGO could not meet the demand of ideal electromagnetic wave absorbing materials.7 First, pristine rGO shows high electrical conductivity, which can produce skin effect and affect its absorbing property. Second, the high permittivity and low permeability of pristine rGO will lead to poor impedance matching. Therefore, pristine graphene has poor excellent electromagnetic wave absorption performance. However, up to now, several rGO composites, Such as, excellent microwave absorption


Page 2 of 74

Page 3 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and electromagnetic interference shielding based on reduced graphene oxide@ MoS2/poly (vinylidene fluoride) composites, fabrication of Fe3O4@SiO2@RGO nanocomposites and other well designed radar absorbing materials. Modifying graphene or RGO with other nanoparticles, for example, Fe2O3 / rGO, Fe3O4 / rGO, rGO / Ni, CNTs / rGO and rGO / SiO2 / NiO nanosheets8-10, and conducting polymers, such as polymer-composite with high dielectric constant and enhanced absorption properties based on graphene–CuS nanocomposites and polyvinylidene fluoride, poly (3, 4-ethylenedioxythiophene) (PEDOT) and so on11, have been studied to improve radar wave absorbing properties. Molybdenum disulfide (MoS2) is a kind of new material, which consists of S-Mo-S triple layers bound by weak van der Waals force, which attracts many researcher’s attention due to its particular electrical, optical and mechanical properties.12 Compared with grapheme, SiC, carbon/metal oxide composites and ceramics-based materials, MoS2 owns a band gap of 1.8 eV. It has a broad application in the field of nano-transistors and single electron mobility of transistors up to a maximum of 500 cm-2 /(V·S) and the current rate of 1 x 10-8, therefore it is better than those materials. Recently, it was reported that MoS2 nanosheet had opened up new prospect in the field of radar absorption. It has been proved that combined rGO with MoS2 is an effective way to obtain light weight composites with outstanding radar wave absorbing performance. MoS2 nanosheets on the surface of reduced graphene oxide were prepared by Amxing x et al7, such as self-supported construction of three-dimensional MoS2 hierarchical nanospheres with tunable

high-performance

microwave

absorption

in

broadband.

MoS2/rGO

nanocomposites were made by hydrothermal growth method. However, this synthetic



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

process is easy to agglomerate and the reaction is incomplete. It limits the addition of MoS2/rGO nanocomposites to the matrix since their weak interaction and dispersion, especially for fabricating MoS2/rGO radar wave absorption coatings14-21. Herein, MoS2 needs to be modified. In this paper, first 3-methacryloxypropyl trimethoxysilane (KH570) modified MoS2 (M/MoS2)/rGO was prepared. Second reduced graphene oxide( rGO) was synthesized by reducing graphene oxide (GO). Finally, (M/MoS2)/rGO nanosheets were synthesized . Compared with the composites prepared by other methods, this method of synthesis of (M/MoS2)/rGO is of a more homogeneous nanosheets. What’s more, this method can solve the problem of aggregation and incomplete reaction. Even if the content of (M/MoS2)/rGO nanocomposites in the wax matrix is as low as 18 wt%, the composites exhibited good absorption properties. With a maximum reflection loss (RL) of -49.7 dB, (M/MoS2)/rGO composites exhibited an effective radar bandwidth of 5.81 GHz at the thickness 2.5 mm. M/MoS2 and rGO could be used as promising materials for RWA and broad absorption properties at low content and thin thickness.

2. Experimental section 2.1. Materials All commercial reagents used herein were of analytical grade and used without further purification. MoS2 and graphite were obtained from Shanghai McLean bio-tech Inc. 3-methacryloxypropyl trimethoxysilane (KH570), polyvinylpyrrolidone (PVP), sulfuric acid, Potassium permanganate (KMnO4), hydrochloric acid (HCL), potassium hydroxide (KOH), ethanol, hydrazine hydrate, H2O2 (30%) were supplied by Guangdong


Page 4 of 74

Page 5 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Guanghua Chemical Reagent Co.Ltd. Distilled water obtained from Direct-Q3UV, Millipore. 2.2. Preparation of M/MoS2 First, 0.5 g MoS2 and 0.75 g KH570 were dispersed in aqueous ethanol solution (180 mL ethanol and 60 mL deionized water) by ultrasonication for 2 h. Some acetic acid was added to the solution to adjust pH value to 4, and then the hydrolysis of KH570 was carried out at 60 ℃ for 4 h. After that, the solution was centrifuged at 4000 r/min for 10 min and washed four times with ethanol-water solution. The product was freeze dried for 24 hours to obtain M/MoS2 powder. 2.3. Synthesis of rGO GO was synthesized by modified Hummers method20. 3.0 g of graphite was mixed with 85 mL sulfuric acid solution for 30 minutes while the temperature of the mixture was cooled to 0 ℃. Then, 8 g of KMnO4 was slowly added to the solution below 10 ℃ for stirring 2 h. The reaction mixture was then incubated in a 35 ℃ water bath for 3 h, forming a thick paste. After additional 180 mL of distilled water was added, followed by a slow addition of 30 mL H2O2 (30wt%), and a bright yellow dispersion of GO appeared during this process. The mixture was filtered and washed with a 1:10 HCl aqueous solution (300 mL) to remove metal ion, and repeated washing with water and centrifugation until the solution became neutral. The mixture was sonicated for 30 min, and followed by adding 0.3 g KOH and 2mL hydrazine hydrate to the solution. The reaction was continued for 24 h at 98 ℃. Finally, the mixture was washed with ethanol and water for several times, and the rGO was obtained and dried at 60 ℃ under vacuum. 2.4. Synthesis of (M/MoS2)/rGO nanosheets



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(M/MoS2)/rGO composites were fabricated by sonicating the mixture of M/MoS2 and rGO. First, 3 g rGO and 0.3 g PVP were added to 650 mL ethanol aqueous solution and sonicated for 3 h, then 1g M/MoS2 was added to the previous mixture. Similarly, it was sonicated for 3 h. After that, the solution was centrifuged at 3000 r/min for 10 min and washed with water several times. The product was freeze dried for 24 hours to obtain (M/MoS2)/rGO nanosheets for further use. This synthetic process has been summarized in Figure 1. Insert Figure 1 As shown in Figure 1, the synthetic process include three steps:（1）The ultrasonic GO is reduced to rGO. （2）Ultrasonic MoS2 composites were stripped into single layer structure, and then added KH570 to modify. (3) The rGO and M/MoS2 nanosheets were mixed and stirred for 3 hours, then washed and dried to obtain the (M/MoS2)/rGO nanosheets.

2.5. Characterization The FTIR spectra were recorded using Perkin-Elmer spectrum-2000(American) in KBr pellets. The spectrum was scanned 16 times from 4000 to 400 cm-1. X-ray diffraction (XRD) patterns were obtained on a D235 diffractometer (Bruker, Germany) equipped with a rotating-anode generator system using Cu Kα radiation (λ=0.154 nm) at a scan rate of 3 ° min-1 ranging from 5 to 90 °. Raman spectroscopy was carried out on a Renishaw in Via Raman Microscope equipped with a 514 nm laser. X-ray photoelectron spectra (XPS) were recorded using a Thermo Scientific ESCALAB 250Xi X-ray photoelectron spectrometer equipped with a monochromatic Al Ka X-ray source (1486.6


Page 6 of 74

Page 7 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


eV). The morphologies of the (M/MoS2)/rGO composites were observed on a scanning electron microscope (SEM, 1530, Germany) equipped with an energy dispersive X-ray spectrometer (EDS), a transmission electron microscope (TEM, Tecnai 12, FEI) and a high resolution transmission electron microscope (HRTEM, Tecnai G2 F20, FEI). The fabricated (M/MoS2)/rGO samples were well-distributed with wax at 80 ℃ in different filler loading 3, 6, 12, and 18 wt% of (M/MoS2)/rGO hybrid. The relative complex permittivity (εr) and permeability (μr ) values were measured by the coaxial wire method in the frequency range of 2–18 GHz with a vector network analyzer (VNA, N5242A PNA-X, Agilent).

3. Results and discussion 3.1 FITR Figure 2 is the FITR spectra of the KH570, M/MoS2, rGO and (M/MoS2)/rGO, respectively. As shown in Figure 2, KH570 presents the characteristic absorption bands of the Si-O groups stretching at 810 cm-1. In comparison with the FTIR of KH570, the Si-O peak of M/MoS2 at 810 cm-1 was disappeared. The peak intensity of (M/MoS2)/rGO at 2915 cm-1, 2838 cm-1 and 1111 cm-1 increased, which is mainly due to KH-570 in the Si(OCH3) hydrolysis of silicon hydroxyl and the other part of the formation of alkoxylation condensation.Therefore, the disappearing of 810 cm-1 can prove the MoS2 was successfully modified by KH570. On the other hand,The rGO nanosheet presents the characteristic absorption bands corresponding to the -OH groups stretching at 3420 cm-1, the C=O groups stretching at 1725 cm-1 and the C-O stretching at 1058 cm-1. Meanwhile, the absorption bands of -OH groups was weak, this is due to the introduction of M/MoS2.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Therefore, it was proved that the M/MoS2 was grafted onto the surface of rGO23-25. Insert Figure 2

3.2 SEM Typical SEM images of the as-prepared (M/MoS2)/rGO composites are shown in Figure 3. It is obvious that the flexible two-dimensional sheet-like structures are found in figure 3a, bulk composites are the agglomerate of MoS2 nanosheets. Compared with the surface of rGO (figure 3b), the roughness of (M/MoS2)/rGO (figure 3c) composites increased clearly, and the agglomerate of MoS2 nanosheets decreased. EDS of Figure 3f, the (M/MoS2)/rGO composites were found to be composed of C, O, Si, S and Mo elements, as show in Figure 3g, the ratio of S and Mo element is approximately 2. It was also proved that (M/MoS2) nanosheet was attached to the surface of rGO. Element mapping was performed by using an EDS attached to SEM to identify the element distribution in the composite. The results are presented in Figure 3h-3l. It was observed from Figure 3h-3l that C, O, Mo, S and Si elements were distributed in the composites, and its distribution at the micro-scale in the composite is more uniform. (M/MoS2)/rGO composites are promising material of RWA and the broad absorption properties are due to the fold and compact surface. Insert Figure 3 3.3 TEM and SAED The crumpled paper-like microstructure of the composites was further confirmed by TEM images. Figure 4 is TEM images of rGO (a), M/MoS2 (b) and (M/MoS2)/rGO (c, d). HRTEM images (e) and the corresponding SAED pattern (f). As revealed in Figure 4a, 4b


Page 8 of 74

Page 9 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and 4c, the electron beam transparent two-dimensional flexible sheets are observed by TEM. Consistent with SEM, lower agglomerate and uniform distribution of M/MoS2 nanosheets are also found by TEM (Figure 4c, 4d). Figure 4e is the HRTEM image of a rGO plate with M/MoS2 nanosheets attached to it, further confirming that they are M/MoS2 composites. It was observed from figure (4e) that there are lattice fringes with the spacing of 0.621 nm at the edges of the crumpled paper-like structures, indicating that nanosheets are few-layer MoS2. The corresponding selected area electron diffraction (SAED) pattern of the composites is presented in Figure 4f, two diffraction rings corresponding to the 110 and 100 reflections of MoS2 and graphene sheets, further confirming the nature of nanosheets. (M/MoS2)/rGO composites have remained the innate character of MoS2 in the fabricate process. The absence of reflection with hkl and l ≠ 0 is because both the rGO and (M/MoS2) nanosheets preferably lie on the TEM grid with their c axes parallel with the electron beam26. Insert Figure 4 3.4 XRD The XRD patterns of GO, rGO, M/MoS2 and (M/MoS2)/rGO were shown in Figure 5, the GO (Figure 5a) exhibited one characteristic diffraction peaks at 2θ=9.8 °, corresponding to the diffraction of the (002). From 2dsinθ=nλ, we calculated the interlayer spacing of (002) of GO was d=0.816 nm. The (M/MoS2) displayed diffraction peak at 2θ =14.37 °, 32.67 °, 35.86 °, 39.53 °, 44.16 °, 49.76 °, 58.32 ° and 60.12 ° , corresponding to the diffraction of the (002), (100), (102), (103), (104), (105), (110) and (112) of M/MoS2 (Figure 5c), respectively. From Figure 5d, we found that (M/MoS2)/rGO presented all the diffraction peak of M/MoS2, this confirmed the



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

existence of (M/MoS2), but it also displayed small diffraction peak at 2θ =14.37 °, which is similar to the patterns of rGO (Figure 5b), this maybe caused by the incompletely reduced GO. However, except the peak at 2θ =14.37 °, signals of rGO can hardly be observed from the spectrum due to the low crystallinity. Insert Figure 5 3.5 Raman spectrum Figure 6a is Raman spectrum of (M/MoS2)/rGO (a), GO (b) and M/MoS2 (c), Figure 6b is the magnify of Figure 6a of circle area. Figure 6c shows the Raman spectrum of rGO and GO nanosheets. RGO in hybrid can be easily identified by Roman spectroscopy. As a kind of graphite material, the Raman scattering of rGO exhibits two Raman-active modes, the characteristic D band (1344 cm-1) represents the disordered structure (including boundaries and flaws) of graphite crystallites, the G peak (1587 cm-1) indicates the integral graphite structure of the graphite crystallites. Based on previous studies, D band is due to breathing mode of k-point photons of A1g symmetry, and the G band arises from the first-order scattering of E2g phonons with sp2 carbon atoms27. Apparently, weak E2g and A1g peaks of (M/MoS2) are also observed at 381 and 407 cm-1. Compared with GO (Figure 6c-a), the disordered structures of rGO (Figure 6c-b) were found after the reduction procedure, respectively, R= ID/IG, the higher value of R, the larger spacing of nanosheets. The ID/IG increased from 0.84 in GO to 1.03 in (M/MoS2)/rGO. The value of R showed that the spacing of (M/MoS2)/rGO nanosheets was enlarged during the process. At last, the agglomerate of composites decreased. Insert Figure 6

3.6 XPS


Page 10 of 74

Page 11 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


The (M/MoS2)/rGO nanosheets were also characterized by XPS. Only signals for C, O, S, Si and Mo were detected in the survey spectrum (Figure 7a). The atomic percent contents of O, S, Mo, Si and C derived from the survey spectrum are 32.54%, 0.37%, 1.09%, 0.01%, 65.99%, respectively. The high content of O indicated that only a part of GO was reduced to rGO in the preparation process. In comparison with previous works, the core-level spectra of Mo and S element reflected the presence of MoS2 (Figures 7b and 7c), whereas Si indicated the existence of KH570 (Figure 7d). The C 1s XPS spectra of (M/MoS2)/rGO and GO were shown in Figures 7e and 7f. The presence of strong characteristic peaks of C-O and C=O indicates that graphite has been highly oxidized. However, compared with the core level spectrum of GO, signals of O-bonded C have significantly decreased in the C 1s spectrum of (M/MoS2)/rGO. Insert Figure 7

3.7 Complex permittivity Figure 8 shown the complex permittivity of rGO and the (M/MoS 2)/rGO-wax composites. The composites presented typical frequency dependent permittivity. As Figure 8c and 8d shown, with the increasing of frequency, the value of real (  ，) and imaginary (  ,, ) part of the permittivity decreased. The  ， and  ,, increased with the increasing of (M/MoS2)/rGO (Figure 8a and 8b) content. When the content of (M/MoS2)/rGO increased from 6 to 12 wt%, the complex permittivity enhanced significantly. The increment of  ，and  ,, may be attributed to the fact that the dipolar polarization of the composites increases with the increasing of (M/MoS2)/rGO content. Figure 8e shown the  ，,  ,, , μ, and μ,, values of relative complex permeability with 18



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

wt% rGO . Compared with Figure 8a-8d, after introducing of (M/MoS2) naosheets, the magnetic increased, which was seen from enhanced permeability. We have also calculated the dielectric tangent loss (tan δ=  ,, /  ，) based on the permeability and permittivity of rGO, which was shown in Figure 8f. Figure 8e demonstrated the  ，,  ,, , μ, and μ,, values of relative complex permeability for rGO with the content of 18 wt%. Compared with Figures 8a-8d, with the introduction of (M/MoS2) naosheets, the magnetic increased,which could been seen from enhanced permeability. We have also calculated the dielectric tangent loss (tan δ=  ,, /  ，) based on the permeability and permittivity of rGO, shown in Figure 8f. To reveal the radar absorption performance of (M/MoS2)/rGO composites, the reflection loss (RL) values of (M/MoS2)/rGO were calculated using the relative complex permeability and permittivity at a given layer thickness according to the transmission line theory,28 which is backed by a perfect conductor for single absorber layer, as follows:

r   

s     ,  j , , 1  j 2f

1

Where f ,  s ,   , and  are frequency, static permittivity, relative dielectric permittivity at the high-frequency limit, and polarization relaxation time, respectively. Debye theory is a helpful tool to study the mechanism for the enhanced performance of the composite with the filler loading of (M/MoS2)/rGO. Thus,  ， and  ,, can be described by

s   1 （2f）2 2

2

2f  s     2 1  2f   2

(3)

 ，   

 ,, 


Page 12 of 74

Page 13 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Where 2πfω is angular frequency,  is polarization relaxation time, according to eq 2, from the frequency range investigated, the decreasing of  ，is attributed to the increasing of  . It may be due to the polarization relaxation in the lower frequency. According to eq (2) and (3), the relationship between ε, and ε,, can be deduced29.  ， s    ,,     2   2

 

2

     s    2 

2

(4)

Thus, the plot ofε, versus ε,, would be a single semicircle at ((εs+ε-)/2,0), which can be defined as the Cole–Cole semicircle, each semicircle corresponds to one Debye relaxation process.30 Insert Figure 8

3.8 Cole-Cole plots Cole-Cole plots of of (M/MoS2)/rGO-wax composites with 12 wt% and 18 wt% of (M/MoS2)/rGO were shown in Figure 9a and 9b. And 18 wt% of rGO was shown in Figure 9c. Compared Figure 9c with Figure 9a and Figure 9b, there is a lager arc of rGO than the (M/MoS2)/rGO composites. Because pure rGO possesses high electronic conductivity, leading to a high value of  ,, , as well as the strong dielectric loss of rGO. There is no obvious change when the content of (M/MoS2)/rGO is 12 wt% and 18 wt%, respectively. This is due to the less network in the wax matrix. Although they both include complicated semicircles, they are much closer to a straight line. The Cole-Cole semicircle curve presents the Debye dielectric relaxation process. In Figure 9a and 9b, the plot of ε′ versus ε″ is a single semicircle, this maybe a highly conductive network forms with the increase of (M/MoS2)/rGO content. we usually think it is the one Debye



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

relaxation process. The absorption mechanism also have Maxwell-Wagner relaxation, conductance loss, interfacial polarization and dipolar polarization. The existed defect and functional groups in (M/MoS2)/rGO have two relaxation processes. First, the defect maybe the polarization center, which would generate polarization relaxation under the altering electromagnetic field and attenuate electromagnetic wave, resulting in a profound effect on the loss of electromagnetic. Second, there are oxygen containing chemical bonds such as C=O in the rGO. The different ability to catch electrons between carbon atom and oxygen atom results in electronic dipole polarization, while this kind of dipole polarization is absent for (M/MoS2). Therefore, through the synergic effect, the (M/MoS2)/rGO composites will have better absorbing property. Insert Figure 9 3.9 RL curve and 3D RL plots To study the electromagnetic absorption property, the reflection loss (RL) of the electromagnetic radiation under the normal incidence of the electromagnetic field was calculated.30 The tested frequency range was from 2 to 18 GHz, thus this measurement process can be thought under the far field, because the distance of source-to-shield is much longer than that of the free-space wavelength. According to transmission line theory, the normalized input impedance (Zin) is given by

Z in  Z 0

  2 fd   r tanh  j  r  r  r   c  

5

Where Z0 ≈ 378 Ω is the impedance of free space,  r and  r are the complex permittivity


Page 14 of 74

Page 15 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


and permeability of the composite absorber, respectively,  r   ,  j ,, ,  r   ,  j ,, , f is the frequency, d is the thickness of the absorber, and c is the velocity of light in free space, c  3 108 ms-1. The flection loss (RL) related to Zin is as fellow31-32:

RL dB  20 log

Z in  1 Z in  1

6

Insert Figure 10

Thus, the theoretical reflection loss (RL) of rGO content of 18 wt% (Figure 10a), and the (M/MoS2)/rGO composites with (M/MoS2)/rGO content of 12 wt% (Figure 10b) , 18 wt% (Figure 10c) and 20 wt% (Figure 10d) at a thickness of 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.5 mm, respectively can be obtained through eqn (5) and (6) (Figure 10a,10b 10c and 10d). The calculated RL of rGO is relatively poor and there is no bandwidth under -10.0 dB, and only a narrow bandwidth under -5.0 dB exists for frequencies between 2 and 18 GHz. It can be seen that the minimum RL decreases and shifts to a lower frequency with the increasing of (M/MoS2)/rGO content. This is mainly due to the increasing of interface between (M/MoS2) and rGO. More interfaces will produce more interfacial polarization.33 And the interfacial polarization can be more easily induced at lower frequency. The minimum RL can also be tuned by altering the concentration of the (M/MoS2)/rGO. As expected from the regular pattern of complex permittivity (Figure10e 10f and 10g), the maximum reflection loss of (M/MoS2)/rGO composites reach -49.7 dB at 13.68 GHz with 18 wt% of (M/MoS2)/rGO when the thickness is 3 mm, which is obviously stronger than that of 12 wt% and 20 wt% of (M/MoS2)/rGO. On the other hand,



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Page 16 of 74

the maximum effective RWA bandwidth is above 5.4 GHz, ranging from 10.3 to 15.74 GHz. The maximum reflection loss of (M/MoS2)/rGO composites reach -44.9 dB with 20 wt% of (M/MoS2)/rGO when the thickness is 3 mm. This indicates the radar absorbing ability of (M/MoS2)/rGO-wax composites at different frequency can be tuned by controlling the thickness of the absorbers. Compared with 18 wt% of (M/MoS2)/rGO, the sample with 12 wt% and 20 wt% of (M/MoS2)/rGO shown a narrative bandwidth and weaker absorb property, which is attributed to a slight increase of complex permittivity (Figure 10h, 10i and 10j). Owing to M/MoS2 nanosheets, the sample of (M/MoS2)/rGO composites exhibited an effective bandwidth of 5.81 GHz, with a maximum RL value of -49.7dB and a thickness of 2.5 mm. There are three reasons for this. First, dipole polarization in the (M/MoS2)/rGO hybrid. Second, multiple interfacial polarizations in the (M/MoS2)/rGO hybrid. Third, defect dipole polarization of rGO. Table 1. Radar Wave Absorption Properties of Typical Materials reported in This Work and Recent Literatures filler

matrix

thickness

Loading ratio (wt%)

Frequency range (GHz)

Effective bandwidth (GHz) 5.81

ref

(M/MoS2)/rGO

wax

2.5

18

10.35-16.16

this work

MoS2/rGO

wax

2.0

10

11.72-17.44

5.72

1

rGO rGO/Fe3O4 rGO/ZnO rGO/CNTs rGO/NiO rGO/Co3O4 rGO/Ni

PVDF wax wax wax wax wax wax

4.0 3.0 2.5 3.0 3.0 2.5 2.0

3 10 50 5 8 20 30

8.48-12.80 9.20-15.00 11.60-18.00 7.10-10.40 10.20-16.90 5.50-16.00 10.90-15.40

4.32 5.80 6.40 3.30 6.70 10.50 4.50

8 13 12 17 4 6 29

The radar wave absorption properties of MoS2/rGO hybrid absorber together with other rGO-based materials reported in recent literatures were summarized in Table 1. In comparing with the recently reported other RGO-based materials, (M/MoS2)/rGO-wax composites exhibited superior performance at a rather thin thickness, indicating the


Page 17 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


promising perspective of (M/MoS2)/rGO hybrid absorber in the development of light weighted, thin electromagnetic wave absorbing coatings. 3.10 The radar wave absorbing mechanism A imagined schematic diagram is presented in Figure11, which gives a clearly demonstration of the radar wave absorbing mechanism. Inside the dielectric (M/MoS2)/rGO composites: (1) the inherent dielectric polarization resulted from (M/MoS2)/rGO composites, (2) spontaneous polarization coupling among the (M/MoS2) and rGO composites. When the electromagnetic wave irradiated to the surface of (M/MoS2) and rGO composites, most of it was absorbed, and a little was reflected. Lots of defects lead to multiple scattering and interfacial electrical polarizations, which provides an important absorbing mechanism. The high aspect ratio and layered structure of (M/MoS2)/rGO composites will lead to multiple reflection in the absorber. By extending the route of electromagnetic wave propagation, which will further enhance the absorbing ability of the composites. In general, compared with pure rGO, the enhanced radar absorbing performance of composites is attributed to the compensatory properties of rGO and MoS2, which has been described in the previously proposed electromagnetic complementary effect. From above, we can see clearly that (M/MoS2)/rGO composites have a great potential in the development of lightweight and high-efficiency radar absorbing materials. Insert Figure 11

Conclusions Laminated magnetic (M/MoS2)/rGO has been successfully synthesized from a facile



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

route, avoiding the problem of aggregation and incomplete reaction, meanwhile improving the efficiency of absorb materials. The results show that (M/MoS2)/rGO composites have significant electromagnetic properties of the as-prepared magnetic (M/MoS2)/rGO composites. The dimension of rGO and MoS2 interlayer spacing range from several nm to above 0.816 nm. The dielectric Cole–Cole semicircle suggests that there are Debye relaxation processes in the laminated magnetic (M/MoS2)/rGO, which is benefit for the enhancement of dielectric loss, and the impedance matching level for electromagnetic wave absorbing materials. MoS2 and rGO could have the advantage of MoS2 and rGO, this could be defined as an electromagnetic complementary effect. When the content of (M/MoS2)/rGO is 18 wt%, (M/MoS2)/rGO-wax composites exhibited good absorption properties. With a maximum reflection loss (RL) of -49.7 dB, (M/MoS2)/rGO -wax composites exhibited an effective EVA bandwidth of 5.81 GHz at the thickness 2.5 mm. The strong absorption capability of (M/MoS2) and rGO could be used as promising materials for RWA and broad absorption properties. The experimental results indicate that the enhanced absorbing performance of composites is attributed to the compensatory properties of (M/MoS2) and rGO. (M/MoS2)/rGO composites have a great potential in the development of lightweight and high-efficiency radar wave absorbing materials.

Acknowledgement We appreciate the financial support from the Science Foundation of State Key Laboratory of Structural Chemistry, China, under grant of No. 20160027. References (1) Liang, X. H.; Quan, B. Novel nanoporous carbon derived from metal-organic frameworks with tunable electromagnetic wave absorption capabilities. Inorganic Chem.


Page 18 of 74

Page 19 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Front. 2016, 12, 1516-1526. (2) Xing, L.; Ma, Z. A glassy carbon electrode modified with a nanocomposite consisting of MoS2 and reduced graphene oxide for electrochemical simultaneous determination of ascorbic acid, dopamine, and uric acid. Micro. Acta. 2016, 183, 257-263. (3) Yang, Z.; Qiu, M.; Ying, Y.; Wen, B. Y.; Cheng, L. A Novel Polyaniline-Coated Bagasse Fiber Composite with Core-Shell Heterostructure Provides Effective Electromagnetic Shielding Performance. Acs Appl. Mater. Interfaces. 2017, 9, 809-818. (4) Liang, X.; Zhang, X.; Liu, W.; Tang, D.; Zhang, B.; Ji, G. A simple hydrothermal process to grow MoS2 nanosheets with excellent dielectric loss and microwave absorption performance. J. Mater. Chem. C . 2016, 4, 6816-6821. (5) Biswas, S.; Arief, I.; Panja, S. S.; Bose, S. Absorption-Dominated Electromagnetic Wave Suppressor Derived from Ferrite-Doped Cross-Linked Graphene Framework and Conducting Carbon. Acs Appl. Mater. Interfaces. 2017, 9, 3030-3039. (6) Qu, B.; Zhu, C.; Li, C.; Zhang, X.; Chen, Y. Coupling Hollow Fe3O4-Fe Nanoparticles with Graphene Sheets for High-Performance Electromagnetic Wave Absorbing Material. Acs Appl. Mater. Interfaces. 2016, 8, 3730-3735. (7) Pan, Y. F.; Wang, G. S.; Yue, Y. H. Fabrication of Fe3O4@SiO2@RGO nanocomposites and their excellent absorption properties with low filler content. Rsc. Adv. 2015, 5, 71718-71723. (8) Zhang, X. J.; Wang, G. S.; Cao, W. Q.; Wei, Y. Z.; Cao, M. S.; Guo, L. Fabrication of multi-functional PVDF/RGO composites via a simple thermal reduction process and their enhanced electromagnetic wave absorption and dielectric properties. Rsc. Adv.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

2014, 4, 19594-19601. (9)Zhang, X.; Wang, G.; Wei, Y.; Guo, L.; Cao, M. Polymer-composite with high dielectric constant and enhanced absorption properties based on graphene-CuS nanocomposites and polyvinylidene fluoride. J. Mater. Chem. A. 2013, 1, (39), 12115. (10) Guo, A.; Zhang, X.; Qu, J.; Wang, S.; Zhu, J.; Wang, G.; Guo, L. Improved microwave absorption and electromagnetic interference shielding properties based on graphene-barium titanate and polyvinylidene fluoride with varying content. Mater. Chem. Front. 2017. DOI: 10.1039/C7QM00204A (11) Yan, L.; Wang, X.; Zhao, S.; Li, Y.; Zhe, G.; Zhang, B.; Cao, M.; Yong, Q. Highly Efficient Microwave Absorption of Magnetic Nanospindle-Conductive Polymer Hybrids by Molecular Layer Deposition. Acs Appl. Mater. Interfaces. 2017, 9, 11116. (12) Tao, Z.; Huang, Y.; Liu, X.; Chen, J.; Lei, W.; Wang, X.; Pan, L.; Pan, J.; Huang, Q.; Zhang, Z. High-Performance Photo-Modulated Thin-Film Transistor Based on Quantum dots/Reduced Graphene Oxide Fragment-Decorated ZnO Nanowires. Nano. Micro. Lett. 2016, 8, 247-253. (13) Xie, A.; Sun, M.; Zhang, K.; Jiang, W.; Wu, F.; He, M. In situ growth of MoS2 nanosheets on reduced graphene oxide (RGO) surfaces: interfacial enhancement of absorbing performance against electromagnetic pollution. Chem. Physics. Pccp. 2016, 18, 24931-24936. (14) Bhattacharya, P.; Das, C. K. In Situ Synthesis and Characterization of CuFe. Chem. Eng. Res. 2013, 52, 9594-9606. (15) Sun, X.; He, J.; Li, G.; Tang, J.; Wang, T.; Guo, Y.; Xue, H. Laminated magnetic graphene with enhanced electromagnetic wave absorption properties. J. Mater. Chem. C.


Page 20 of 74

Page 21 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


2012, 1, 765-777. (16) Chen, Z.; Xu, C.; Ma, C.; Ren, W.; Cheng, H. Lightweight and Flexible Graphene Foam Composites for High-Performance Electromagnetic Interference Shielding. Adv. Mater. 2013, 25, 1296-1300. (17) Zhang, H.; Zhang, G.; Li, J.; Fan, X.; Jing, Z.; Li, J.; Shi, X. Lightweight, multifunctional microcellular PMMA/Fe3O4 @MWCNTs nanocomposite foams with efficient electromagnetic interference shielding. Appl. Sci. 2017, 100, 128-138. (18) Li, J.; Zhang, G.; Ma, Z.; Fan, X.; Fan, X.; Qin, J.; Shi, X. Morphologies and electromagnetic interference shielding performances of microcellular epoxy/multi-wall carbon nanotube nanocomposite foams. Sci. Technol. 2016, 129, 70-78. (19) Yang, Y.; Gupta, M. C.; Dudley, K. L.; Lawrence, R. W. Novel Carbon Nanotube Polystyrene Foam Composites for Electromagnetic Interference Shielding. Nano. Lett. 2005, 5, 2131-2134. (20) Durmus, Z.; Durmus, A.; Bektay, M. Y.; Kavas, H.; Unver, I. S.; Aktas, B. Quantifying structural and electromagnetic interference (EMI) shielding properties of thermoplastic polyurethane–carbon nanofiber/magnetite nanocomposites. J. Mater. Sci. 2016, 51, 8005-8017. (21) Ren, Y.; Wu, H.; Lu, M.; Chen, Y.; Zhu, C.; Gao, P.; Cao, M.; Li, C.; Ouyang, Q. Quaternary Nanocomposites Consisting of Graphene/Fe. Acs Appl. Mater. Interfaces. 2012, 4, 6436-6442. (22) Kumar, R.; Singh, R. K.; Vaz, A. R.; Savu, R.; Moshkalev, S. A. Self-Assembled and One-Step Synthesis of Interconnected 3D Network of Fe. Acs Appl. Mater. Interfaces. 2017, 9, 8880-8890.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

(23) Song, W.; Guan, X.; Fan, L.; Zhao, Y.; Cao, W.; Wang, C.; Cao, M. Strong and thermostable polymeric graphene/silica textile for lightweight practical microwave absorption composites. Carbon. 2016, 100, 109-117. (24) Li, X.; Li, X.; Liao, K.; Min, P.; Liu, T.; Dasari, A.; Yu, Z. Thermally Annealed Anisotropic Graphene Aerogels and Their Electrically Conductive Epoxy Composites with Excellent Electromagnetic Interference Shielding Efficiencies. Acs Appl. Mater. Interfaces. 2016, 8, 33230-33239. (25) Wang, C.; Han, X.; Xu, P.; Zhang, X.; Du, Y.; Hu, S.; Wang, J.; Wang, X. The electromagnetic property of chemically reduced graphene oxide and its application as microwave absorbing material. Appl. Phys. Lett. 2011, 98, 217. (26) Li, X.; Li, X.; Liao, K.; Min, P.; Liu, T.; Dasari, A.; Yu, Z. Thermally Annealed Anisotropic Graphene Aerogels and Their Electrically Conductive Epoxy Composites with Excellent Electromagnetic Interference Shielding Efficiencies. Acs Appl. Mater. Interfaces. 2016, 8, 33230-33239. (27) Park, S.; Chung, D. Y.; Ko, D.; Sung, Y.; Piao, Y. Three-dimensional carbon foam/N-doped graphene@MoS. J. Mater. Chem. A. 2016, 4, 12720-12725. (28) Zhou, W.; Zhou, K.; Hou, D.; Liu, X.; Li, G.; Sang, Y.; Liu, H.; Li, L.; Chen, S. Three-Dimensional Hierarchical Frameworks Based on MoS. Acs Appl. Mater. Interfaces. 2014, 6, 21534-21540. (29) Zhang, H.; Yan, Q.; Zheng, W.; He, Z.; Yu, Z. Tough Graphene−Polymer Microcellular Foams for Electromagnetic Interference Shielding. Acs Appl. Mater. Interfaces. 2011, 3, 918-924. (30) Wu, Y.; Wang, Z.; Liu, X.; Shen, X.; Zheng, Q.; Xue, Q.; Kim, J. Ultralight


Page 22 of 74

Page 23 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Graphene Foam/Conductive Polymer Composites for Exceptional Electromagnetic Interference Shielding. Acs Appl. Mater. Interfaces. 2017, 9, 9059-9069. (31) Yang, J.; Zhang, J.; Liang, C.; Wang, M.; Zhao, P.; Liu, M.; Liu, J.; Che, R. Ultrathin BaTiO3 Nanowires with High Aspect Ratio: A Simple One-Step Hydrothermal Synthesis and Their Strong Microwave Absorption. Acs Appl. Mater. Interfaces. 2013, 5, 7146-7151. (32) Wang, H.; Wang, W.; Gui, M.; Asif, M.; Wang, Z.; Yu, Y.; Xiao, J.; Liu, H. Uniform Fe. Acs Appl. Mater. Interfaces. 2017, 9, 335-344. (33) Naeem, S.; Baheti, V.; Tunakova, V.; Militky, J.; Karthik, D.; Tomkova, B. Development of porous and electrically conductive activated carbon web for effective EMI shielding applications. Carbon. 2017, 111, 439-447.



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

For Table of Contents Only 247x157mm (96 x 96 DPI)


Page 24 of 74

Page 25 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 1 Synthesis of (M/MoS2)/rGO nanosheets 247x157mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 2 FITR spectrum of the KH570, M/MoS2, rGO and (M/MoS2)/rGO 119x91mm (96 x 96 DPI)


Page 26 of 74

Page 27 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


146x132mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

179x179mm (96 x 96 DPI)


Page 28 of 74

Page 29 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


179x179mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

146x132mm (96 x 96 DPI)


Page 30 of 74

Page 31 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


146x132mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

146x132mm (96 x 96 DPI)


Page 32 of 74

Page 33 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


146x132mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

146x137mm (96 x 96 DPI)


Page 34 of 74

Page 35 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


146x137mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

146x137mm (96 x 96 DPI)


Page 36 of 74

Page 37 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


146x137mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 3 SEM images of pure MoS2 (a), rGO (b) and (M/MoS2)/rGO (c and d); EDS of (M/MoS2)/rGO nanosheets (f and g); EDS mapping area of (M/MoS2)/rGO nanosheets (e) and the element signals of C (h), O (l), Mo (j), S (k), and Si(l). 146x137mm (96 x 96 DPI)


Page 38 of 74

Page 39 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


145x128mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

150x128mm (96 x 96 DPI)


Page 40 of 74

Page 41 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


145x127mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

145x129mm (96 x 96 DPI)


Page 42 of 74

Page 43 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


146x132mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 4 TEM images of pure rGO (a), M/MoS2 (b), (M/MoS2)/rGO (c) and (d), HRTEM images of (M/MoS2)/rGO (e) and the corresponding SAED pattern (f) 200x147mm (96 x 96 DPI)


Page 44 of 74

Page 45 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 5 XRD spectrum of GO (a), rGO (b), M/MoS2 (c) and (M/MoS2)/rGO (d) 167x118mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

159x108mm (96 x 96 DPI)


Page 46 of 74

Page 47 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


150x118mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 6 a shows the Raman spectrum of (M/MoS2)/rGO (a), GO (b) and M/MoS2 (c), 6b is the magnify of the 6a circle area, 6c shows the Raman spectrum of rGO and GO nanosheets. 122x115mm (96 x 96 DPI)


Page 48 of 74

Page 49 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


154x114mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

152x116mm (96 x 96 DPI)


Page 50 of 74

Page 51 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


165x119mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

172x125mm (96 x 96 DPI)


Page 52 of 74

Page 53 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


163x118mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure7 XPS core-level spectra of survey spectrum (a), Mo 3d (b), S 2p (c), Si 1s (d) and C 1s (e) of (M/MoS2)/rGO; core-level spectrum of C1s (f) in GO 156x112mm (96 x 96 DPI)


Page 54 of 74

Page 55 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


156x115mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

166x126mm (96 x 96 DPI)


Page 56 of 74

Page 57 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


148x114mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

147x112mm (96 x 96 DPI)


Page 58 of 74

Page 59 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


252x176mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure 8 Real (a and b) and imaginary (c and d) parts of therelative complex permittivity of (M/MoS2)/rGOwax composites with different contents of (M/MoS2)/rGO; Frequency dependence of (e) complex relative permittivity and permeability, and (f) the dielectric loss tangent of the rGO composites. 252x176mm (96 x 96 DPI)


Page 60 of 74

Page 61 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


147x114mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

148x110mm (96 x 96 DPI)


Page 62 of 74

Page 63 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 9 Cole-Cole plots of (M/MoS2)/rGO-wax composites: (a) 12 wt%, (b) 18 wt%; 18 wt% of rGO were shown in (c). 252x175mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

247x191mm (96 x 96 DPI)


Page 64 of 74

Page 65 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


251x175mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

251x175mm (96 x 96 DPI)


Page 66 of 74

Page 67 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


249x192mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

253x176mm (96 x 96 DPI)


Page 68 of 74

Page 69 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


253x176mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

250x193mm (96 x 96 DPI)


Page 70 of 74

Page 71 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


253x176mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

254x177mm (96 x 96 DPI)


Page 72 of 74

Page 73 of 74

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60


Figure 10 RL curve of rGO-wax composites with 18 wt% (a), and 3D RL plots of (M/MoS2)/rGO-wax composites with different contents (12 wt% (b, e, h) ，18 wt% (c, f, g)) and 20 wt% (h, i, j) of (M/MoS2)/rGO. 240x185mm (96 x 96 DPI)



1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60

Figure11 The radar wave absorbing mechanism. 151x108mm (96 x 96 DPI)


Page 74 of 74

Reduced Graphene ... - ACS Publications

Recommend Documents