Gradient Structure Design of Flexible Waterborne Polyurethane

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Applications of Polymer, Composite, and Coating Materials

Gradient Structure Design of Flexible Waterborne Polyurethane Conductive Films for Ultra-Efficient Electromagnetic Shielding with Low Reflection Characteristic Yadong Xu, Yaqi Yang, Ding-Xiang Yan, Hongji Duan, Guizhe Zhao, and Yaqing Liu ACS Appl. Mater. Interfaces, Just Accepted Manuscript • DOI: 10.1021/acsami.8b05129 • Publication Date (Web): 16 May 2018 Downloaded from http://pubs.acs.org on May 16, 2018

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ACS Applied Materials & Interfaces

Gradient Structure Design of Flexible Waterborne Polyurethane Conductive Films for Ultra-Efficient Electromagnetic Shielding with Low Reflection Characteristic Yadong Xu1, Yaqi Yang1, Ding-Xiang Yan2,3, Hongji Duan1,3*, Guizhe Zhao1, Yaqing Liu1* 1

Key Laboratory of Functional Nanocomposites of Shanxi Province, College of

Materials Science and Engineering, North University of China, Taiyuan 030051, People’s Republic of China 2

School of Aeronautics and Astronautics, Sichuan University, Chengdu 610065,

People’s Republic of China 3

State Key Laboratory of Polymer Materials Engineering, Sichuan University,

Chengdu 610065, People’s Republic of China ABSTRACT:

Highly efficient electromagnetic shielding materials entailing strong

electromagnetic wave absorption and low reflection have become an increasing requirement for next-generation communication technologies and high-power electronic instruments. In this study, a new strategy is employed to provide flexible waterborne

polyurethane

(WPU)

composite

films

with

an

ultra-efficient

electromagnetic shielding effectiveness (EMI SE) and low reflection by constructing gradient shielding layers with a magnetic ferro/ferric oxide deposited on reduced graphene oxide (rGO@Fe3O4) and silver-coated tetra-needle-like ZnO whisker

∗

Corresponding author. Tel./fax: +86 3513559669.

E-mail addresses: [email protected] (H. Duan); [email protected] (Y. Liu) 1

ACS Paragon Plus Environment

ACS Applied Materials & Interfaces 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

(T-ZnO/Ag) functional nanoparticles. Because of the differences in density between rGO@Fe3O4 and T-ZnO/Ag, a gradient structure is automatically formed during the film formation process. The gradient distribution of rGO@Fe3O4 over the whole thickness range forms an efficient electromagnetic wave absorption network that endows the film with a strong absorption ability on the top side, while a thin layer of high-density T-ZnO/Ag at the bottom constructs a highly conductive network that provides an excellent electromagnetic reflection ability for the film. This specific structure results in an “absorb-reflect-reabsorb” process when electromagnetic waves penetrate into the composite film, leading to an excellent EMI shielding performance with an extremely low reflection characteristic at a very low nanofiller content (0.8 vol% Fe3O4@rGO and 5.7 vol% T-ZnO/Ag): the EMI SE reaches 87.2 dB against the X band with a thickness of only 0.5 mm, while the shielding effectiveness of reflection (SER) is only 2.4 dB, and the power coefficients of reflectivity (R) is as low as 0.39. This result means that only 39% of the microwaves are reflected in the propagation process when 99.9999998% are attenuated, which is the lowest value among the reported references. This composite film with remarkable performance is suitable for application in portable and wearable smart electronics, and this method offers an effective strategy for absorption-dominated EMI shielding. KEYWORDS: electromagnetic interference shielding, low reflection, waterborne polyurethane, flexible conductive films, gradient structure 1. INTRODUCTION With the rapid development of portable and wearable smart electronics, 2


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electromagnetic radiation has been raised to a level never attained before, which justifies the urgent search for novel and highly efficient electromagnetic interference (EMI) shielding material solutions in a wide variety of applications.1-6 Current research shows improving the electrical conductivity of shielding material is an effective strategy to realize higher shielding levels as a significant increase in microwave reflection efficiency.6-10 Very recently, 2D transition-metal carbides (MXenes) have been introduced as a promising alternative to graphene for achieving superior EMI shielding effectiveness (EMI SE) over 70 dB because of their ultrahigh electrical conductivity (5.8×104 S/m).11,12 Using intrinsic conducting polymers as conductive functional components is another trend for fabricating highly efficient flexible EMI materials.13-19 Recent work shows that PEDOT:PSS/waterborne polyurethane composite films possess a conductivity of 7.7×103 S·m-1 and exhibit a high EMI SE of 62 dB.14 However, a constructing network with a high conductivity in a polymer matrix is not a perfect solution to design an ideal shielding material. The excessive conductivity also means a high reflection of electromagnetic waves because of the impedance mismatch between the space wave and the materials. Despite their high EMI shielding efficiency, these shielding materials with homogeneous conductive networks usually exhibit an extremely high reflection coefficient of more than 90%, which cause serious secondary electromagnetic radiation pollution and complicate the electromagnetic environments. Thus, in light of the information regarding safety and operational reliability, ideal EMI shielding materials with high shielding efficiency entailing strong electromagnetic wave absorption and low 3



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reflection have become an increasing requirement for the next-generation of communication technology and high-power electronic instruments.20,21 It is well-known that efficient shielding materials can attenuate electromagnetic (EM) wave through electrical loss, magnetic loss and dielectric loss.13,22-29 The commonly used carbon nanofillers rarely offer magnetic hysteresis loss to the shielding materials, so the contribution of EM wave absorption to total shielding effectiveness is seriously limited due to the limited EMI shielding mechanism of carbon nanofillers. A feasible solution to this problem is hybridizing ferromagnetic nanoparticles, such as nickel-plated multi-walled carbon nanotubes and reduced graphene

oxide

coated

with

magnetic

ferro/ferric

oxide

nanoparticles

(rGO@Fe3O4).22,30 These materials, prompting magnetic and electrical losses, can absorb electromagnetic waves more efficiently and mitigate the impact of secondary electromagnetic radiation to a considerable degree. However, for such materials to achieve a satisfactory EMI SE higher than 50 dB always requires a high nanofiller loading and large material thickness, therefore, presenting inferior process-ability, mechanical properties and low affordability. More importantly, the shielding networks constructed in such composites are usually a homogeneous system of uniform conductivity, which is useless in reducing the secondary electromagnetic radiation because of the strong reflection of the EM wave on the initial incident surface.13-20,32-36 Apparently, when an impedance-matching absorption layer is introduced as the initial shielding layer, and the reflection intensity in the shielding material is gradually increased along the EM wave penetrating direction, the reflected 4


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EM wave would undoubtedly go through multiple interfacial reflection and absorption events before reflecting back to free space, leading to a significant decrease in secondary electromagnetic radiation pollution. This fact actually indicates that a gradient distribution of shielding networks would be more effective than a homogeneous shielding network and possess a rather low reflection because of this structural advantage. Thus, by turning the impedance-matching degree with a suitable arrangement of impedance-matching absorption and conductive layers, the appropriate gradient shielding network design would bring a new strategy for fabricating ultra-efficient electromagnetic shielding materials with low reflection characteristics. In this work, we fabricated a novel flexible waterborne polyurethane (WPU) composite film with ultra-efficient EMI SE and low reflection characteristics by constructing a gradient shielding network with magnetic ferro/ferric oxide deposited on reduced graphene oxide (rGO@Fe3O4) and silver-coated tetra-needle-like ZnO whisker (T-ZnO/Ag) functional nanoparticles. The gradient structure can be automatically formed during the film formation process because of the density difference between rGO@Fe3O4 and T-ZnO/Ag nanoparticles. The gradient distribution of rGO@Fe3O4 over the whole thickness range serves as an efficient electromagnetic wave absorption layer that endows the film with a strong absorption ability, while the highly conductive T-ZnO/Ag network at the bottom guarantees the film an excellent electromagnetic shielding ability. This specific structure in flexible composite films results in the “absorb-reflect-reabsorb” process when electromagnetic 5



waves penetrate, leading to an excellent EMI shielding performance with extremely low reflection characteristic at very small nanofiller contents. The composite film with a thickness of only 0.5 mm achieves an excellent EMI SE of up to 87 dB in the X band, while the power coefficient of reflectivity (R) is only 0.39. This result is superior to most of the other reported high-performance electromagnetic shielding materials, indicating an absorption dominated the EMI shielding mechanism. 2. MATERIALS AND METHODS 2.1. Materials. Anionic aliphatic waterborne polyurethane (WPU) with solid content of 35 wt% was supplied by Chengdu Organic Chemicals Co. LTD (Chengdu, China). Tetra-needle-like ZnO whisker (T-ZnO) and graphene oxide (GO) were obtained from Tangshan Jianhua Science and Technology Development Co., Ltd. (Hebei, China). The GO had the following features: thickness of 0.5-4.0 nm, lateral dimension of 0.5-3.0 µm, and oxygen content is higher than 30 at. %. All chemical reagents, including FeCl3·6H2O (≥98.0%), FeSO4·7H2O (≥98.0%), AgNO3 (≥99.8%), SnCl2·2H2O (≥98.0%), KNaC4H4O6·4H2O (≥98.0%), PdCl2 (≥99.9%), NaOH (≥99.5%), HCl (38.0%), NH3·H2O (28%), HCHO (≥38.0%), ethanol (≥99.7%) were purchased from Guangfu Fine Chemical Research Institute (Tianjin, China). All chemical reagents were analytical grade and used without further purification. 2.2. Preparation of the rGO@Fe3O4 Dispersion. The rGO@Fe3O4 dispersion was synthesized by a simple and effective coprecipitation method as following process:37 20 mL of GO dispersion (GO content: 40mg) was sonicated for 15 min to prepare GO 6


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suspension. 0.15 g of FeCl3·6H2O and 0.4 g of FeSO4·7H2O was slowly mixed with the as-prepared GO suspension. After degassing with N2 for 30 min, 4 ml of NH3·H2O was added to the solution with vigorous mechanical agitation at 60 °C for 2 h. Finally, the solution was reduced in the presence of hydrazine at 80 °C for 8 h to obtain the rGO@Fe3O4, as shown in Figure 1a. 2.3. Preparation of the T-ZnO/Ag Nanofiller. The T-ZnO/Ag Nanofiller was synthesized via electroless deposition as following process:38-40 a sensitizing treatment of T-ZnO was conducted using a 400 mL sensitization solution composed of 9 g SnCl2·2H2O, 14 g NaOH and 14 g KNaC4H4O6·4H2O, and then ultrasonic treated for 15 min. The T-ZnO was filtrated, washed with water and ethanol. The activating treatment was carried out using a 200 mL solution composed of 0.02 g PdCl2 and 0.2 mL HCl. The T-ZnO was sonicated for 15 min, filtrated, washed respectively with water and ethanol, and dried (Figure S1). The treated T-ZnO was immersed in an electroless plating bath that consisted of 1 g AgNO3, 8mL NH3·H2O in 100 mL deionized water. 4 ml formaldehyde as reduction agent was dropwise added into the bath with vigorously mechanical stirring at 30 ℃ with ultrasonic processing. Finally, the product was filtrated, washed respectively with water and ethanol, and dried. The electrical conductivity of T-ZnO/Ag nanofiller can reach 51200 S/m. By comparing the weight changes of nanofiller before and after the electroless deposition, the calculated mass fraction of Ag is 55%. 2.4. Preparation of the rGO@Fe3O4/T-ZnO/Ag/WPU composite film. The rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various filler contents and 7



thicknesses were fabricated by simple solution mixing. A certain amount of T-ZnO/Ag nanofillers, rGO@Fe3O4 suspension and WPU emulsion were mixed, stirred and sonicated for 30 min. Then the solution was degassed and casted onto culture dish to evaporate water at 60 ℃ for 12 h in the oven. In this process, due to the different deposit velocity of different fillers, gradient structure can be easily formed, in which the T-ZnO/Ag deposited on the bottom of the films and the rGO@Fe3O4 located at the top of the films. Finally, the rGO@Fe3O4/T-ZnO/Ag/WPU composite films with gradient structure can be easily obtained, as shown in Figure 1b, c. In the experimental process, excessive amounts of rGO@Fe3O4 affected the formation of composite films in which a lot of cracks are produced (Figure S2). Therefore, the rGO@Fe3O4 addition is lower than 2 vol%. 2.5. Characterization. The morphology of the nanofillers and composite film was investigated by field emission scanning electron microscopy (FESEM, Hitachi SU8010) at the accelerating voltage of 15 kV. Energy dispersive X-ray spectroscopy (EDX) elemental mapping was conducted to confirm the distribution of fillers within the composite film. The specimens for SEM observations were quickly cryo-fractured after immersing in liquid nitrogen for 30 min. All the samples were sputter-coated with gold before observation. The transmission electron microscopy (TEM) analysis was carried out using JEOL-2100F microscope at 200 kV acceleration voltage with a standard single-tilt holder. The structure of nanofillers was determined by the X-ray diffraction (XRD, Haoyuan 2700B) using Cu Ka (k = 0.1546 nm). The electrical conductivity of the composite film was measured by four-point probes meter 8


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(Qianfeng SB120) at room temperature. EMI shielding properties were performed using an Agilent N5230 vector network analyzer with a coaxial test cell (APC-7 connector) in conjunction according to ASTM ES7-83. All samples were sliced into circular plates. The measured scattering parameters (S11 and S21 or S22 and S12) were used to calculate the EMI SE. From the measured scattering parameters (S11 and S21), The total EMI SE (SETotal), shielding effectiveness of the absorption (SEA), reflection (SER) and the power coefficients of reflectivity (R), the transmissivity (T), the absorptivity (A) could be obtained.

Figure 1. Schematic of the fabrication of the rGO@Fe3O4/T-ZnO/Ag/WPU composite films, insets of the schematic show the (a) magnetic rGO@Fe3O4 nanofiller, (b) as well as the flexibility and (c) magnetism of the composite film. 3. RESULTS AND DISCUSSION 3.1. Characterization of rGO@Fe3O4. Figure 2a shows the laminar structure of the 9



GO with wrinkles and a large aspect ratio. Cambiform Fe3O4 nanocrystals with a mean diameter of 150 nm are uniformly anchored on the surface of rGO (Figure 2b). These nanoparticles are expected to prevent restacking of the rGO.22 The high-resolution TEM images (Figure 2c) of the Fe3O4 nanocrystals are shown with measured periodic lattice fringe spacing of 0.210 nm and 0.485 nm, which corresponds to interplanar spacings of the (400) and (111) planes of Fe3O4.41,42 Figure 2d shows the XRD pattern of the rGO@Fe3O4 hybrid. The characteristic diffraction peaks of Fe3O4 at approximately 35°, 57°, and 62° are indexed to the (311), (511), and (440) planes of Fe3O4, respectively, corresponding to the cubic inverse spinel structure of magnetic ferro/ferric oxide (JCPDS Card No. 19-0629).42 These results demonstrate the successful synthesis of the rGO@Fe3O4 hybrids.

Figure 2. TEM images of (a) GO and (b) rGO@Fe3O4. (c) An HRTEM image of the 10


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Fe3O4 nanocrystals embedded in the rGO matrix. (d) The XRD pattern of rGO@Fe3O4. 3.2. Characterization of T-ZnO/Ag Particle. The Conductivity of the nanofiller and their dimensional structures are the most important factors impacting the EMI shielding performance of the shielding materials. As the SEM images show in Figure 3a, b, T-ZnO exhibits a tetrapod stereo conformation with four needles 5-10 µm in length and 0.5-1 µm in width. Hence, T-ZnO readily connect with each other and form the network structure by means of their three-dimensional four-needle structure. Figure 3c-e shows SEM images of the T-ZnO/Ag nanofiller. After electroless deposition of Ag, the Ag nanocrystals evenly coat on the surface of T-ZnO and form a compact layer (Figure 3d), which is crucial to realizing the high conductivity of T-ZnO. The Ag-Zn mapping image of the T-ZnO/Ag nanofiller in Figure 3f overlapped with the corresponding SEM image also confirms the completed deposition of Ag on the surface of T-ZnO. The average thickness of the Ag shell is approximately 100 nm, as confirmed by SEM analysis (Figure S3). To further identify the chemical compositions of the T-ZnO/Ag nanofiller, XRD analysis is performed and the spectra are shown in Figure 4. The peaks at 38.10°, 44.32°, 64.46° and 77.40° represent the (111), (200), (220) and (311) faces of the face-centered cubic structure of silver (JCPDS Card No. 04-0783), confirming that the Ag nanocrystals are successfully deposited onto T-ZnO.

11



Figure 3. SEM images of (a, b,) T-ZnO and (c-e) T-ZnO/Ag nanofiller, (f) The SEM elemental map of the T-ZnO/Ag nanofiller.

12


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Figure 4. XRD patterns of T-ZnO whiskers and T-ZnO/Ag nanofillers. 3.3. Microstructure of rGO@Fe3O4/T-ZnO/Ag/WPU composite films. Because of the large densities of T-ZnO (5.606 g/cm3) and Ag (10.49 g/cm3), the T-ZnO/Ag nanofiller easily generates a sedimentary layer during the formation process of the film. The cross-section morphology of the rGO@Fe3O4/T-ZnO/Ag/WPU film in Figure 5 reveals a dense conductive layer consisting of the deposited T-ZnO/Ag at the bottom of the film. The SEM image in Figure S4 further confirms the well-interconnected T-ZnO/Ag conductive network. At the same time, the thickness of the conductive layer increases with enhanced T-ZnO/Ag content. The thickness of the conductive layer is approximately 20 µm at 1.5 vol% T-ZnO/Ag loading (Figure 5b). As the T-ZnO/Ag content increases to 5.7 vol%, the average thickness of the conductive layer reaches 60 µm (Figure 5h). The thicker T-ZnO/Ag conductive network is beneficial to achieving a higher conductivity and higher EM wave reflection efficiency, providing the film with greater EMI SE. At the same time, to 13



confirm the implementation of gradient distribution of rGO@Fe3O4 and T-ZnO/Ag, Fe and Ag EDX element mappings of the rGO@Fe3O4/T-ZnO/Ag/WPU composite film are obtained to determine the distribution of each filler (Figure 5j, k). The distributions of Fe and Ag elements reveal a clear boundary in the image, in which Ag mainly deposits at the bottom of the composite film and Fe forms a gradient distribution in the upper layer of the composite film. All the above results suggest that a gradient structure of the composite film is successfully realized by utilizing the density difference of the fillers.

Figure 5. SEM images of the rGO@Fe3O4/T-ZnO/Ag/WPU composite films at a thickness of 0.2 mm with various filler contents: (a-c) 0.8 vol% rGO@Fe3O4, 1.5 vol% 14


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T-ZnO/Ag; (d-f) 0.8 vol% rGO@Fe3O4, 3.4 vol% T-ZnO/Ag; and (g-i) 0.8 vol% rGO@Fe3O4,

5.7

vol%

T-ZnO/Ag.

An

EDX

map

of

the

rGO@Fe3O4

/T-ZnO/Ag/WPU composite film with 0.8 vol% rGO@Fe3O4, 3.4 vol% T-ZnO/Ag: (j) Ag element map, (k) Fe element map. 3.4. Electrical Conductivity of rGO@Fe3O4/T-ZnO/Ag/WPU composite films. To further verify this gradient conductive network, the surface and bottom electrical conductivities of the rGO@Fe3O4/T-ZnO/Ag/WPU composite film with 0.8 vol% rGO@Fe3O4 and 1.5 vol% T-ZnO/Ag are characterized. As shown in Figure 6a, the bottom conductivity of composite film is nine orders of magnitude higher than the surface conductivity. This result is consistent with the structure from the SEM image. In addition, the bottom conductivity of the rGO@Fe3O4/T-ZnO/Ag/WPU film increases significantly with T-ZnO/Ag content (Figure 6b). At a T-ZnO/Ag content of 1.5 vol%, the conductivity of the composite film is 11190 S/m. When the T-ZnO/Ag loading is increased to 5.7 vol%, the conductivity of the composite film increases sharply and reaches to 22700 S/m. This outstanding conductivity higher than most reported values for conductive polymer composites,43-50 is attributed to the extremely high conductivity of T-ZnO/Ag and its high connected network derived from the specific four-needled structure. In addition, the T-ZnO/Ag nanofiller forms a dense conductive layer at the bottom instead of being uniformly dispersed in the film, which is favorable to obtaining excellent EMI SE.

15



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Figure 6. (a) Surface and bottom conductivities of the rGO@Fe3O4/T-ZnO/Ag/WPU composite film with 0.8 vol% rGO@Fe3O4 and 1.5 vol% T-ZnO/Ag. (b) The bottom conductivities of rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various filler contents. 3.5. EMI Shielding Performance of the rGO@Fe3O4/T-ZnO/Ag/WPU composite films.

The

EMI

SE

against

the

X-band

frequency

range

for

rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various T-ZnO/Ag loadings and thicknesses are displayed in Figure 7. It is worth noting that the composite film containing only 0.8 vol% rGO@Fe3O4 and 1.5 vol% T-ZnO/Ag already exhibits an EMI SE of 51.3 dB even at a thickness of 0.2 mm, far exceeding the requirement of commercial EMI shielding applications (20 dB). As the T-ZnO/Ag loading rises to 5.7 vol%, the composite achieves an ultrahigh EMI SE of 67.8 dB. Compared with composite films in which the T-ZnO/Ag filler is distributed homogeneously in the film thickness direction, the composite films with the gradient structure show superior EMI SE (Figure S5). Figure 7b shows that the increased SETotal of the composite film is mainly based on the improved absorption rather than the reflection of electromagnetic waves, and the SER is only 4.0 dB. Generally, the EMI shielding 16


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effectiveness of shielding materials increases with the thickness. The total SE of the composite films increases as the thickness increases from 0.2 mm to 0.5 mm, as shown in Figure 7a, c. When the T-ZnO/Ag content is 1.5 vol%, the average SE value of the composite film with a thickness of 0.5 mm is 87.2 dB. More interestingly, the results in Figure 7b, d shows an evident adsorption-dominated shielding mechanism, and the dominant contribution of SEA increases to 97.3% as the thickness rises from 0.2 mm to 0.5 mm. We further investigate the influence of the rGO@Fe3O4 content on the EMI SE of the composite films, and examinations of the total values of EMI SE for the composite films reveal a slight increase in the EMI SE as the rGO@Fe3O4 content is increased (Figure S6). To obtain a better understanding of the function of the gradient structure, a comparison

of

SER

and

R

between

rGO@Fe3O4/T-ZnO/Ag/WPU

and

T-ZnO/Ag/WPU composite films is performed. Compared with T-ZnO/Ag/WPU composite films, the SER and power coefficient (R) can be reduced significantly for the rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various filler loadings (see Figure S7). The average R value is 0.39 for the rGO@Fe3O4/T-ZnO/Ag/WPU composite film with 0.8 vol% rGO@Fe3O4 and 5.7 vol% T-ZnO/Ag, while the average R value is 0.73 for the T-ZnO/Ag/WPU composite film with 5.7 vol% T-ZnO/Ag, indicating that absorption-dominated shielding occurs when rGO@Fe3O4 is present in the composite film. This phenomenon is mainly ascribed to the following two properties. First, rGO@Fe3O4 with magnetic and dielectric losses, can act as a strong electromagnetic wave absorber to increase the wave absorption ability of the 17



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composite films (Figure S8). The improved complex permittivity of the rGO@Fe3O4 hybrid mainly results from the relaxation and polarization caused by rGO, and the complex permeability of rGO@Fe3O4 is derived from the additional nonmagnetic Fe3O4. At the same time, the values for the impedance-matching condition for rGO@Fe3O4 are close to 1 over the whole frequency range; this indicates that microwaves can easily enter the composite films, resulting in a good microwave absorption performance. Another important reason is the specific gradient distribution of rGO@Fe3O4 and T-ZnO/Ag, which induces the special “absorb-reflect-reabsorb” process when EM waves penetrate. The gradient structure with a suitable arrangement of the impedance-matching absorption layer and conductive layer can prolong the pathway of reflected waves and induce more multiple interfacial reflection and absorption events, leading to the absorption-dominated shielding mechanism and low reflection characteristics of the composite films. Additionally,

the

EMI

SE

against

the

X-band

for

the

rGO@Fe3O4/T-ZnO/Ag/WPU composite films at different incident directions are tested, as shown in Figure 8. The EMI SE against the X-band for the rGO@Fe3O4/T-ZnO/Ag/WPU composite films at different incident directions are labeled 12 and 22 (inset image of Figure 8a). SEtotal-12 and SEtotal-21 of the composite films increase as the filler content is increased; at the same time, they are nearly the same at equal amounts of filler content. This result illustrates that the incident direction has no clear effect on the SEtotal of the composite films. However, the SER-12 and SER-21 of the composite films show a huge difference at equal amounts of filler 18


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content. Because of the high conductivity of T-ZnO/Ag layer, SER-21 value of the composite film with 0.8 vol% rGO@Fe3O4 and 1.5 vol% T-ZnO/Ag is greater than 20 dB, which has nearly reached the upper limit of reflection efficiency, while the SER-12 value is limited to 4.0 dB. These results indicate that the gradient structure design can significantly attenuate backscattered signals.

Figure 7. EMI SE and a comparison of SETotal, SEA, and SER against the X-band for the rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various thicknesses: (a, b) 0.2 mm and (c, d) 0.5 mm.

19



Figure 8. EMI SE against the X-band for the rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various filler contents at different incident directions: (a) 0.8 vol% rGO@Fe3O4, 1.5 vol% T-ZnO/Ag; (b) 0.8 vol% rGO@Fe3O4, 3.4 vol% T-ZnO/Ag; and (c) 0.8 vol% rGO@Fe3O4, 5.7 vol% T-ZnO/Ag. To give a comprehensive understanding of the microwave attenuation mechanism for the prepared composite films, the power coefficient of reflectivity (R), transmissivity (T), and absorptivity (A) are obtained from the measured scattering parameters (S11, S21), and then the EMI SE (SETotal), microwave reflection (SER) and microwave absorption (SEA) can be calculated as follows: R |11| 20


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T |21| 1A+R+T SE −10 log −10 log(1 − )

−10 log SE − − 1− The SEM can be considered negligible when SETotal is beyond 15 dB.51 Further analysis of the experimental results indicates that the microwave shielding mechanism of the composite films consists of a strong absorption and low reflection mechanism, as shown in Figure 9. At a fixed rGO@Fe3O4 loading, the SER and R of the rGO@Fe3O4/T-ZnO/Ag/WPU composite films increase with the T-ZnO/Ag content. This can be ascribed to the increased conductivity of the composite films with the improved T-ZnO/Ag content. The higher conductivity and denser conductive layer lead to higher reflection. The SER of the composite film with 0.8 vol% rGO@Fe3O4 and 1.5 vol% T-ZnO/Ag at a thickness of 0.2mm is approximately 4.0 dB, corresponding to a 60% reflection of the incident electromagnetic waves. Furthermore, with an increase in film thickness, the composite film with 0.8 vol% rGO@Fe3O4 and 1.5 vol% T-ZnO/Ag exhibits an outstanding SER of only 1.9 dB at a thickness of 0.5 mm, corresponding to a 33% reflection of the incident electromagnetic waves. It is observed that with the introduction of rGO@Fe3O4, a peak in the R value appears. This can be mainly attributed to the specific absorbing ability of Fe3O4 for a particular frequency band.27 This reduced reflection is mainly due to the enhancement in the absorption ability of the composite films with increasing thickness of the rGO@Fe3O4 21



layer. The study of the influence of the rGO@Fe3O4 content on the reflection and absorption portions of the shielding for the composite films indicates that absorption ability is further enhanced by the rGO@Fe3O4 content up to 1.6 vol% (Figure 10). This result is far superior to other EMI shielding materials with various fillers reported in the literature.

Figure 9. (a, c) SER and (b, d) power coefficient of reflectivity (R) against the X-band for the rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various thicknesses.

22


Page 22 of 38

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Figure 10. (a-c) SER and (d-f) power coefficient of reflectivity (R) against the X-band for the rGO@Fe3O4/T-ZnO/Ag/WPU composite films at a thickness of 0.2 mm with various filler contents. Table 1 shows a comparison of the EMI SE, SER and R of different EMI shielding materials reported in the recent literature. For conventional EMI shielding materials, a high conductivity is always required to realize a superior EMI shielding performance. Therefore, the aggravation of the impedance mismatch issue dramatically increases the reflection property of shielding materials. For example, the EMI SE of outstanding EMI shielding materials usually exceeds 60 dB, and the SER of these materials always exceeds 10 dB, which means over 99% of the incident electromagnetic waves are reflected as secondary electromagnetic radiation pollution.9,10,16 In this work, the advantages of this novel gradient structure design result in not only an excellent EMI SE but also low reflection characteristics that can be realized simultaneously in rGO@Fe3O4/T-ZnO/Ag/WPU composite films. The 23



Page 24 of 38

average EMI SE of 87.2 dB for the composite films is higher than those of the most recently reported EMI shielding materials. Meanwhile, the average SER and R values of only 2.4 dB and 0.39, respectively, are also superior to those of other reported EMI shielding materials. These superior low-reflection characteristics attest to the strong microwave absorbing ability of rGO@Fe3O4 and the efficient gradient structure design of the film. Table 1. Comparison of the SER and R of different materials with the present results. EMI SE Composites

SER (dB)

R

Ref.

(dB)

WPU/MWCNT

49.3

8.9

0.87

2

Epoxy/MWCNT/Ag

61.7

12.8

0.95

4

MXenes

57

20

0.99

8

PS-MXene

62

6.5

0.78

12

G-CNT-Fe2O3/PEDOT: PSS

133

11

0.92

13

PU/PEDOT: PSS

62

20

0.99

14

PANI/AgNW

37.7

10.8

0.92

16

PANI/BF

29.6

6.2

0.76

17

PEDOT: PSS/Fe3O4

46

10

0.90

18

PMMA/rGO/ Fe3O4

57.1

6.1

0.75

25

MCMB/MWCNTs/ Fe3O4

57

8

0.84

28

WPU/MWCNT

62

15

0.97

54

rGO/AgNWs/rGO

38

11

0.92

55

24


Page 25 of 38 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


rGO@Fe3O4/T-ZnO/Ag/WPU

Figure

11.

87.2

illustrates

the

2.4

EMI

0.39

shielding

Our Work

mechanism

of

the

rGO@Fe3O4/T-ZnO/Ag/WPU composite films against incident microwaves. The incident microwaves are first absorbed by the gradient rGO@Fe3O4 layer. The rGO@Fe3O4 nanoparticles located at the upper surface of the film induce a strong dielectric loss and magnetic hysteresis loss to absorb and attenuate incident electromagnetic waves. Meanwhile, these nanoparticles, with a comparatively low conductivity, provide proper impedance matching to reduce the reflection. Then, the penetrating microwaves are reflected and attenuated by the dense and highly-efficient conductive T-ZnO/Ag layer before transmitting through the film. Throughout this process, the microwaves undergo the “absorb-reflect-reabsorb” process, and in this manner, the composite films significantly attenuate the backscattered signals and exhibit an excellent EMI SE.

Figure

11.

Schematic

representation

of

the

shielding

25


mechanism

for

the


rGO@Fe3O4/T-ZnO/Ag/WPU composite films.

4. CONCLUSIONS In this study, flexible WPU composite films with ultra-efficient EMI SE and low reflection characteristics are fabricated by constructing gradient shielding layers with rGO@Fe3O4 and T-ZnO/Ag. The gradient distribution of rGO@Fe3O4 in the upper surface endows the film with a strong absorption ability because of the significant magnetic hysteresis loss and dielectric loss of rGO@Fe3O4, while the dense T-ZnO/Ag network deposited at the bottom of the film provides an excellent electromagnetic shielding ability because of its remarkable conductivity. This specific structure results in the “absorb-reflect-reabsorb” process for the incident electromagnetic waves, leading to an excellent EMI shielding performance with an extremely low reflection property at a very low nanofiller content. The composite film with a thickness of only 0.5 mm can achieve an excellent EMI SE of up to 87 dB against the X band with a power coefficient of reflectivity (R) of only 0.39. This novel gradient shielding network design can serve as a strategy for designing highly efficient EMI shielding materials with low reflection characteristics. This composite film with a remarkable shielding performance shows potential for application next-generation communication technologies and high-power electronic instruments such as portable and wearable smart electronic devices. ASSOCIATED CONTENT Supporting Information: The Supporting Information is available free of charge on the ACS Publications 26


Page 26 of 38

Page 27 of 38 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


website at DOI: SEM image of the T-ZnO whiskers; digital images of composite films with various rGO@Fe3O4 loadings; SEM images of the Ag shell; SEM images of the T-ZnO/Ag/WPU composite films with various filler contents; EMI SE of the T-ZnO/Ag/WPU composite films with various filler contents, which T-ZnO/Ag fillers distributed homogeneously in the film thickness direction; EMI SE of the rGO@Fe3O4/T-ZnO/Ag/WPU composite films with various rGO@Fe3O4 contents; the comparison of the SER and Power coefficient of reflectivity (R) of composite films with different filler; electromagnetic parameter of the rGO@Fe3O4. (PDF) AUTHOR INFORMATION Corresponding Authors *E-mail: [email protected] (H. Duan); [email protected] (Y. Liu) ORCID Hongji Duan: 0000-0002-9035-5029; Yaqing Liu: 0000-0002-2643-5139 Notes The authors declare no competing financial interest. ACKNOWLEDGMENTS The authors gratefully acknowledge the financial support from the National Natural Science Foundation of China (Grant No. 21704070, 51673134), Natural Science Foundation of Shanxi Province (Grant No. 201701D221089), and the Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (Grant No. sklpme2017409 and sklpme2017306). 27



Page 28 of 38

REFERENCES

(1) Yan, D. X.; Pang, H.; Li, B.; Vajtai, R.; Xu, L.; Ren, P. G.; Wang, J. H.; Li, Z. M.

Structured

Reduced

Graphene

Oxide/Polymer

Composites

for

Ultra-Efficient Electromagnetic Interference Shielding. Adv. Funct. Mater. 2015, 25 (4), 559-666. (2) Zeng, Z. H.; Jin, H.; Chen, M. J.; Li, W. W.; Zhou, L. C.; Zhang, Z. Lightweight and Anisotropic Porous MWCNT/WPU Composites for Ultrahigh Performance Electromagnetic Interference Shielding. Adv. Funct. Mater. 2016, 26 (2), 303-310. (3) Yang, Y.; Li, M.; Wu, Y. P.; Wang, T.; Eugene, S. G. C.; Ding, J.; Zong, B. Y.; Yang, Z. H.; Xue, J. M. Nanoscaled Self-Alignment of Fe3O4 Nanodiscs in Ultrathin rGO Films with Engineered Conductivity for Electromagnetic Interference Shielding. Nanoscale 2016, 8, 15989-15998. (4) Xu, Y.; Li, Y.; Hua, W.; Zhang, A. M.; Bao, J. J. Light-Weight Silver Plating Foam and Carbon Nanotube Hybridized Epoxy Composite Foams with Exceptional Conductivity and Electromagnetic Shielding Property. ACS Appl. Mater. Inter. 2016, 8 (36), 24131-24142. (5) Huang, Z. Y.; Chen, H. H.; Huang, Y.; Ge, Z.; Zhou, Y.; Yang, Y.; Xiao, P. S.

Liang, J. J.; Zhang, T. F.; Shi, Q.; Li, G. H.; Chen Y. S. Ultra-Broadband

Wide-Angle Terahertz Absorption Properties of 3D Graphene Foam. Adv. Funct. Mater. 2017, 28 (2), 1704363. (6) Zhang, Y.; Huang, Y.; Zhang, T. F.; Chang, H. C.; Xiao, P. S.; Chen, H. H.; 28


Page 29 of 38 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


Huang, Z. Y.; Chen Y. S. Broadband and Tunable High-Performance Microwave Absorption of an Ultralight and Highly Compressible Graphene Foam. Adv. Mater. 2015, 27 (12), 2049-2053. (7) Zhou, E. Z.; Xi, J. B.; Liu, Y. J.; Xu, Z.; Guo, Y.; Peng, L.; Gao, W. W.; Ying, J.; Chen, Z. C.; Gao C. Large-Area Potassium-Doped Highly Conductive Graphene Films for Electromagnetic Interference Shielding. Nanoscale 2017, 9, 18613-18618. (8) Shahzad, F.; Alhabeb, M.; Hatter, C. B.; Anasori, B.; Man Hong, S.; Koo, C. M.; Gogotsi, Y. Electromagnetic Interference Shielding with 2D Transition Metal Carbides (MXenes). Science 2016, 353 (6304), 1137-1140. (9) Li, J.; Liu, H.; Guo, J.; Hu, Z.; Wang, Z. J.; Wang, B.; Liu, L.; Huang, Y. D.; Guo

Z.

H.

Flexible,

Conductive,

Porous,

Fibrillar

Polymer-Gold

Nanocomposites with Enhanced Electromagnetic Interference Shielding and Mechanical Properties. J. Mater. Chem. C 2017, 5, 1095-1105. (10) Lee, J.; Liu, Y.; Liu, Y.; Park, S. J.; Park, M.; Kim, H. Y. Ultrahigh Electromagnetic Interference Shielding Performance of Lightweight, Flexible, and Highly Conductive Copper-Clad Carbon Fiber Nonwoven Fabrics. J. Mater. Chem. C 2017, 5, 7853-7861. (11)Liu, J.; Zhang, H. B.; Sun, R. H.; Liu, Y. F.; Liu, Z. S.; Zhou, A. G.; Yu, Z. Z. Hydrophobic,

Flexible,

and

Lightweight

MXene

Foams

for

High-Performance Electromagnetic-Interference Shielding. Adv. Mater. 2017, 29 (38), 1702367. 29



Page 30 of 38

(12)Sun, R. H.; Zhang, H. B.; Liu, J.; Xie, X.; Yang, R.; Li, Y.; Hong, S.; Yu, Z. Z.

Highly

Conductive

Transition

Metal

Carbide/Carbonitride-(MXene)@Polystyrene Nanocomposites Fabricated by Electrostatic Assembly for Highly Efficient Electromagnetic Interference Shielding. Adv. Funct. Mater. 2017, 27 (45), 1702807. (13) Lee, S. H.; Kang, D. H.; Oh, IlK. Multilayered Graphene-Carbon Nanotube-Iron Oxide

Three-Dimensional

Heterostructure

for

Flexible

Electromagnetic

Interference Shielding Film. Carbon 2017, 111, 248-257. (14) Li, P. C.; Du, D. H.; Guo, L.; Guo, Y. X.; Ouyang J. Y. Stretchable and Conductive Polymer Films for High-Performance Electromagnetic Interference Shielding. J. Mater. Chem. C 2016, 4, 6525-6532.

(15)Zhao,

H.;

Hou,

L.;

Bi,

S.

Y.;

Lu,

Y.

X.

Enhanced

X-Band

Electromagnetic-Interference Shielding Performance of Layer-Structured Fabric-Supported Polyaniline/Cobalt–Nickel Coatings. ACS Appl. Mater. Interfaces 2017, 9 (38), 33059-33070. (16)Fang, F.; Li, Y. Q.; Xiao, H. M.; Hu, N.; Fu, S. Y. Layer-Structured Silver Nanowire/Polyaniline Composite Film as A High Performance X-Band EMI Shielding Material. J. Mater. Chem. C 2016, 4, 4193-4203. (17)Zhang, Y.; Qiu, M. N.; Yu, Y.; Wen, B. Y.; Cheng, L. L. A Novel Polyaniline-Coated

Bagasse

Fiber

Composite

with

Core−Shell

Heterostructure Provides Effective Electromagnetic Shielding Performance. ACS Appl. Mater. Interfaces 2017, 9 (1), 809-818. 30


Page 31 of 38 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


(18)Xia, Y. J.; Fang, J.; Li, P. C.; Zhang, B. M.; Yao, H. Y.; Chen, J. S.; Ding, J.; Ouyang, J. Y. Solution-Processed Highly Superparamagnetic and Conductive PEDOT: PSS/Fe3O4 Nanocomposite Films with High Transparency and High Mechanical Flexibility. ACS Appl. Mater. Interfaces 2017, 9 (22), 19001-19010. (19)Zou, L. H.; Zhang, S. L.; Li, X. P.; Lan, C. T.; Qiu, Y. P.; Ma, Y. Step-by-Step Strategy for Constructing Multilayer Structured Coatings toward High-Efficiency Electromagnetic Interference Shielding. Adv. Mater. Interfaces 2016, 3 (5), 1500476. (20)Lu, Z. G.; Ma, L. M.; Tan, J. B.; Wang, H. Y.; Ding, X. M. Graphene, Microscale Metallic Mesh, and Transparent Dielectric Hybrid Structure for Excellent Transparent Electromagnetic Interference Shielding and Absorbing. 2D Mater. 2017, 4, 025021. (21)Zhang, J. J.; Li, J. W.; Tan, G. G.; Hu, R. C.; Wang, J. Q.; Chang, C. T.; Wang, X. M. Thin and Flexible Fe–Si–B/Ni–Cu–P Metallic Glass Multilayer Composites for Efficient Electromagnetic Interference Shielding. ACS Appl. Mater. Interfaces 2017, 9 (48), 42192-42199. (22)Chen, Y.; Wang, Y. L.; Zhang, H. B.; Li, X. F.; Gui C. X.; Yu, Z. Z. Enhanced

Electromagnetic

Interference

Shielding

Efficiency

of

Polystyrene/Graphene Composites with Magnetic Fe3O4 Nanoparticles. Carbon 2015, 82, 67-76. (23)Chen, Y.; Zhang, H. B.; Huang, Y. Q.; Jiang, Y.; Zheng, W. G.; Yu, Z. Z. 31



Magnetic and Electrically Conductive Epoxy/Graphene/Carbonyl Iron Nanocomposites for Efficient Electromagnetic Interference Shielding. Composites Science and Technology 2015, 118, 178-185. (24)Injamamul, A.; Sourav, B.; Suryasarathi, B. FeCo-Anchored Reduced Graphene Oxide Framework-Based Soft Composites Containing Carbon Nanotubes as Highly Efficient Microwave Absorbers with Excellent Heat Dissipation Ability. ACS Appl. Mater. Interfaces 2017, 9 (22), 19202-19214. (25) Farbod, S.; Mohammad, A.; Aref, A. M.; Uttandaraman, S.; Edward, P. L. R. Segregated

Hybrid

Poly

(methyl

methacrylate)/Graphene/Magnetite

Nanocomposites for Electromagnetic Interference Shielding. ACS Appl. Mater.

Interfaces 2017, 9 (16), 14171-14179. (26)Lim, G. H.; Woo, S. W.; Lee, H. Y.; Moon, K. S.; Sohn, H. S.; Lee, S. E.; Lim, B. K. Mechanically Robust Magnetic Carbon Nanotube Papers Prepared with CoFe2O4 Nanoparticles for Electromagnetic Interference Shielding and Magnetomechanical Actuation. ACS Appl. Mater. Interfaces 2017, 9 (46), 40628-40637. (27)Li, Z. X.; Li, X. H.; Zong, Y.; Tan, G. G.; Sun, Y.; Lan, Y. Y.; He, M.; Ren, Z. Y.; Zheng, X. L. Solvothermal Synthesis of Nitrogen-Doped Graphene Decorated by Superparamagnetic Fe3O4 Nanoparticles and Their Applications as Enhanced Synergistic Microwave Absorbers. Carbon 2017, 115, 493-502. (28)Anisha, C.; Rajeev, K.; Satish, T.; Dhawana, S. K.; Sanjay, R. D.; Saroj, K. Integration of MCMBs/MWCNTs with Fe3O4 in A Flexible and Light 32


Page 32 of 38

Page 33 of 38 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


Weight Composite Paper for Promising EMI Shielding Applications. J. Mater. Chem. C 2017, 5, 322-332. (29) Li, N.; Huang, G. W.; Li, Y. Q.; Xiao, H. M.; Feng, Q. P.; Hu, N.; Fu, S. Y. Enhanced Microwave Absorption Performance of Coated Carbon Nanotubes by Optimizing the Fe3O4 Nanocoating Structure. ACS Appl. Mater. Interfaces 2017,

9 (3), 2973-2983. (30)Yim, Y. J.; Rhee, K. Y.; Park, S. J. Electromagnetic Interference Shielding Effectiveness

of

Nickel-Plated

MWCNTs/High-Density

Polyethylene

Composites. Composites Part B 2016, 98, 120-125. (31)Jia, L. C.; Li, Y. K.; Yan, D. X. Flexible and Efficient Electromagnetic Interference Shielding Materials from Ground Tire Rubber. Carbon 2017, 121, 267-273. (32)Lee, T. W.; Lee, S. E.; Jeong, Y. G. Carbon Nanotube/Cellulose Papers with High Performance in Electric Heating and Electromagnetic Interference Shielding. Composites Science and Technology 2016, 131, 77-87. (33)Wang, Y.; Gu, F. Q.; Ni, L .J.; Liang, K.; Marcus, K.; Liu, S. L.; Yang, F.; Chen, J. J.; Feng, Z. S. Easily Fabricated and Lightweight PPy/PDA/AgNW Composites for Excellent Electromagnetic Interference Shielding. Nanoscale 2017, 9, 18318-18325. (34)Zeng, Z. H.; Jin, H.; Chen, M. J.; Li, W. W.; Zhou, L. C.; Xue, X.; Zhang, Z. Microstructure Design of Lightweight, Flexible, and High Electromagnetic

33



Page 34 of 38

Shielding Porous Multiwalled Carbon Nanotube/Polymer Composites. Small 2017, 13 (34), 1701388. (35)Lee, T. W.; Lee, S. E.; Jeong, Y. G. Highly Effective Electromagnetic Interference Shielding Materials based on Silver Nanowire/Cellulose Papers. ACS Appl. Mater. Interfaces 2016, 8 (20), 13123-13132. (36)Zeng, Z. H.; Chen, M. J.; Pei, Y. M.; Seyed, I. S. S.; Che, B. Y.; Wang, P. Y.; Lu,

X.

H.

Ultralight

Nanocomposites

with

and

Flexible

Unidirectional

Polyurethane/Silver Pores

for

Highly

Nanowire Effective

Electromagnetic Shielding. ACS Appl. Mater. Interfaces 2017, 9 (37), 32211-32219. (37)Ren, P. G.; Wang, H.; Yan, D. X.; Huang, H. D.; Wang, H. B.; Zhang, Z. P.; Xu, L.; Li, Z. M. Ultrahigh Gas Barrier Poly (Vinyl Alcohol) Nanocomposite Film Filled with Congregated and Oriented Fe3O4@GO Sheets Induced by Magnetic-Field. Composites: Part A 2017, 97, 1-9. (38)Duan, H. J.; Xu, Y. D.; Yan, D. X.; Yang, Y. Q.; Zhao, G. Z.; Liu, Y. Q. Ultrahigh Molecular Weight Polyethylene Composites with Segregated Nickel

Conductive

Network

for

Highly

Efficient

Electromagnetic

Interference Shielding. Mater. Lett. 2017, 209, 353-356. (39)Xu, Y. D.; Yang, Y. Q.; Yan, D. X.; Duan, H. J.; Dong, C. Y.; Zhao, G. Z.; Liu, Y. Q. Anisotropically Conductive Polypropylene/Nickel Coated Glass Fiber Composite via Magnetic Field Inducement. J. Mater. Sci.: Mater. Electron. 2017, 28, 9126-9131. 34


Page 35 of 38 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


(40)Duan, H. J.; Yang, J. M.; Yang, Y. Q.; Zhao, G. Z.; Liu, Y. Q. TiO2 Hybrid Polypropylene/Nickel Coated Glass Fiber Conductive Composites for Highly Efficient Electromagnetic Interference Shielding. J. Mater. Sci.: Mater. Electron. 2017, 28, 5725-5732. (41)Si, S. F.; Li, C. H.; Wang, X.; Yu, D. P.; Peng, Q.; Li, Y. D. Magnetic Monodisperse Fe3O4 Nanoparticles. Crystal Growth & Design 2005, 5 (2), 391-393. (42)Shen, B.; Zhai, W. T.; Tao, M. M.; Ling, J. Q.; Zheng, W. G. Lightweight, Multifunctional Polyetherimide/Graphene@Fe3O4 Composite Foams for Shielding of Electromagnetic Pollution. ACS Appl. Mater. Interfaces 2013, 5 (21), 11383-11391. (43)Huang, H. D.; Liu, C. Y.; Zhou, D.; Jiang, X.; Zhong, G. J.; Yan, D. Y.; Li, Z. M. Cellulose Composite Aerogel for Highly Efficient Electromagnetic Interference Shielding. J. Mater. Chem. A 2015, 3, 4983-4991. (44)Cui, C. H.; Yan, D. X.; Pang, H.; Xu, X.; Jia L. C.; Li, Z. M. Formation of a Segregated

Electrically

Low-Melt-Viscosity

Conductive

Polymer

for

Network

Highly

Structure

Efficient

in

a

Electromagnetic

Interference Shielding. ACS Sustainable Chem. Eng. 2016, 4, 4137-4145. (45)Yan, D. X.; Pang, H.; Xu, L.; Bao, Y.; Ren, P. G.; Lei, J.; Li, Z. M. Electromagnetic Interference Shielding of Segregated Polymer Composite with An Ultralow Loading of in Situ Thermally Reduced Graphene Oxide, Nanotechnology 2014, 25, 145705. 35



(46)Jia, L. C.; Yan, D. X.; Cui, C. H.; Ji, X.; Li, Z. M. A Unique Double Percolated Polymer Composite

for Highly Effcient Electromagnetic

Interference Shielding, Macromol. Mater. Eng. 2016, 10, 1232-1241. (47)Jia, L. C.; Yan, D. X.; Cui, C. H.; Jiang, X.; Ji, X.; Li, Z. M. Electrically Conductive and Electromagnetic Interference Shielding of Polyethylene Composites with Devisable Carbon Nanotube Networks, J. Mater. Chem. C 2015, 3, 9369-9378. (48)Jia, L. C.; Li, M. Z.; Yan, D. X.; Cui, C. H.; Wu, F. Y.; Li, Z. M. A Strong and Tough Polymer–Carbon Nanotube Film for Flexible and Efficient Electromagnetic Interference Shielding, J. Mater. Chem. C 2017, 5, 8944-8951. (49) Huang, W. J.; Dai, K.; Zhai, Y.; Liu, H.; Zhan, P. F.; Gao, J. C.; Zheng, G. Q.; Liu, C. T.; Shen, C. Y. Flexible and Lightweight Pressure Sensor Based on Carbon Nanotube/Thermoplastic Polyurethane Aligned Conductive Foam with Superior Compressibility and Stability. ACS Appl. Mater. Interfaces 2017, 9 (48), 42266-42277. (50) Wang, Y. L.; Hao, J.; Huang, Z. Q.; Zheng, G. Q.; Dai, K.; Liu, C. T.; Shen, C. Y. Flexible Electrically Resistive-Type Strain Sensors Based on Reduced Graphene Oxide-Decorated Electrospun Polymer Fibrous Mats for Human Motion Monitoring. Carbon 2018, 126, 360-371.

(51)Jia, L. C.; Yan, D. X.; Yang, Y. C.; Zhou, D.; Cui, C. H.; Bianco, V; Lou, J.; Robert, V.; Li, B.; Ajayan, P. M.; Li, Z. M. High Strain Tolerant EMI 36


Page 36 of 38

Page 37 of 38 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


Shielding Using Carbon Nanotube Network Stabilized Rubber Composite, Adv. Mater. Technol. 2017, 2 (7), 1700078. (52) Gupta, T. K.; Singh, B. P.; Dhakate, S. R.; Singh, V. N.; Mathur, R. B. Improved Nanoindentation and Microwave Shielding Properties of Modified MWCNT Reinforced Polyurethane Composites. J. Mater. Chem. A 2013, 1, 9138-9149. (53) Chen, H. H.; Huang, Z. Y.; Huang, Y.; Zhang, Y.; Ge, Z.; Qin, B.; Liu, Z. F.; Shi, Q.; Xiao, P. S.; Yang, Y.; Zhang, T. F.; Chen, Y. S. Synergistically Assembled MWCNT/Graphene Foam With Highly Efficient Microwave Absorption in Both C and X Bands. Carbon 2017, 124, 506-514.

(54)Zeng, Z. H.; Chen, M. J.; Jin, H.; Li, W. W.; Xue, X.; Zhou, L. C.; Pei, Y. M.; Zhang,

H.;

Zhang,

Z.

Thin

and

Flexible

Multi-Walled

Carbon

Nanotube/Waterborne Polyurethane Composites with High-Performance Electromagnetic Interference Shielding. Carbon 2016, 96, 768-777. (55) Kumar, P.; Shahzad, F.; Hong, S. M.; Koo, C. M. A Flexible Sandwich

Graphene/Silver Nanowires/Graphene Thin Film for High-Performance Electromagnetic Interference Shielding. RSC Adv. 2016, 6, 101283-101287.

37



Table of Content 105x73mm (300 x 300 DPI)


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Gradient Structure Design of Flexible Waterborne Polyurethane

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