High-performance flexible electromagnetic shielding polyimide fabric prepared by nickel-tungsten-phosphorus electroless plating

Journal of Alloys and Compounds 777 (2019) 1265e1273

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High-performance flexible electromagnetic shielding polyimide fabric prepared by nickel-tungsten-phosphorus electroless plating Xiaodong Ding, Wei Wang, Yu Wang, Rui Xu, Dan Yu* College of Chemistry, Chemical Engineering and Biotechnology, Donghua University, Shanghai, 201620, China

a r t i c l e i n f o

a b s t r a c t

Article history: Received 3 August 2018 Received in revised form 9 November 2018 Accepted 10 November 2018 Available online 12 November 2018

In this paper, functional polyimide (PI) fabric with high electrically conductive and electromagnetic shielding effect was prepared by nickel-tungsten-phosphorus (Ni-W-P) electroless plating. Firstly, a wave-absorbing and conductive polyaniline (PANI) layer was in-situ polymerized on the surface of fabric. Secondly, the PANI reduced the palladium ions to palladium particles acting as catalytically active sites. Finally, Ni-W-P electroless plating was initiated and formed a uniform and dense layer. The features of Ni-W-P alloy layer on PI fabric were characterized by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The thermal stability of the sample was also evaluated by thermogravimetric analysis (TGA). The results showed that the electrical conductivity was 0.08 U/sq and the outstanding electromagnetic shielding effectiveness (SE) could reach 103 dB. Moreover, the robust SE performance after multiple ultrasonic washing and bending tests also implied the resultant material had a great potential in the textile protection fields. © 2018 Elsevier B.V. All rights reserved.

Keywords: Electromagnetic shielding Polyimide fabric Nickel-tungsten-phosphorus electroless plating Conductive Polyaniline

1. Introduction In recent years, various electronic devices and communication technologies have mushroomed in the modern life. The technological revolution brings great convenient and at the same time inevitably produces a large number of byproducts, and electromagnetic wave pollution is one of them, which becomes the fourth largest pollution followed by water pollution, air pollution, and noise pollution [1e3]. Excessive electromagnetic waves not only cause interference to electronic instruments and communication facilities, but also incur serious harm to human health [4e6]. Hence, more attentions have been paid to produce electromagnetic shielding materials. At present, these materials are developed to shield electromagnetic wave through such mechanisms as absorption, reflection and internal multiple reflections [7e9]. The electromagnetic shielding mechanism of metals is the reflection of electromagnetic waves due to their large amount of mobile electronics, while polymer conductive polymers (such as polypyrrole, polyaniline, polythiophene, and polyacetylene) achieved electromagnetic shielding by absorbing electromagnetic waves.

* Corresponding author. E-mail address: [email protected] (D. Yu). https://doi.org/10.1016/j.jallcom.2018.11.120 0925-8388/© 2018 Elsevier B.V. All rights reserved.

Polyaniline (PANI), as a typical intrinsically conductive polymer, has been widely used for its many advantages, such as easy synthesis, low cost, low density, excellent electrical conductivity and thermal stability [10]. The combination of conducting polymer and metal on the fabric can serve as the dual functions of absorption and reflection to decrease electromagnetic wave, leading to a flexible composite material with excellent electromagnetic shielding properties [11e13]. The eager demand for electromagnetic shielding materials in the commercial, civil and military fields has led to the emergence of smart textiles with electromagnetic shielding effects, which are obtained through the functional finishing of fabrics with flexible and lightweight advantages. There is a positive correlation between conductivity and electromagnetic shielding performance. That is, to metalize the surface of fabrics can obtain both excellent conductive and electromagnetic shielding properties. But this goal is still challenge to textiles as their loose structure and inherent nature. Generally, the main methods are focused on electroplating [14e16], magnetron sputtering [17], vacuum deposition [18,19], and electroless plating [20,21]. Among them, electroless plating has been favored due to its low cost and simplicity of processing [22]. It is well known that traditional electromagnetic interference (EMI) shielding fabrics were prepared by using metallization of Cu, Ni and Ag layers [20,23e26]. The application of electroless copper plating

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technology is limited due to its low oxidation resistance and low electromagnetic shielding performance. Metal nickel is widely used with the drawback of low conductivity and electromagnetic shielding performance. The silver electroless plating fabric has a stronger shielding effect because of its higher electrical conductivity. We have produced Ag/PANI/PI fabric with SE of 54e90 dB and Ag/PANI/PET fabric with SE of 50e90 dB [26,27]. However, the bottleneck of silver plating technology is difficult to realize largescale production due to its high price. Moreover, a single plating metal layer cannot obtain excellent comprehensive performance and meet the high demand of aerospace and other military fields. Therefore, alloy electroless plating has become an effective method and is favored by researchers. For example, in order to further improve the properties of electroless Ni-P coatings, a number of ternary Ni-X-P coatings have been developed, where X is typically a transition metal such as Co, Cu, Mo and W [28e31]. Gao et al. demonstrated that cobalt improved the corrosion resistance and shielding performance of 60e112 dB when coated with Ni-Co-P layer on aluminum substrates [4]. Zhang et al. have developed a layered structure of Fe-Si-B/Ni-Cu-P metal glass composites by electroless Ni-Cu-P coating on Fe-Si-B metal. The 0.1 mm thick composite shows 40 dB of EMI shielding effectiveness in the X-band frequency range, which is higher than that of conventional metals [32]. Shi et al. electroless plated Ni-Mo-P ternary alloys on birch wood boards, with surface resistivity up to 208 mU/cm2, and electromagnetic shielding effectiveness higher than 45 dB from 9 kHz to 1.5 GHz [33]. Tungsten exhibits a significant advantage in Ni-W-P electroless plating due to its high melting point, high hardness and anti-nuclear radiation properties [34,35]. Hence, Ni-W-P alloy coating has attracted our attention because of its superior properties, and its potential has yet to be further developed. Herein, a layered structure of shielding composite was designed by in-situ polymerization of PANI and followed by Ni-W-P electroless plating, in which PANI acted as conductive polymer as well as reductive agent. PI fabrics were herein selected as the substance as a novel high performance fabric. The features of Ni-W-P alloy layer on PI fabric were characterized by SEM, EDS, XPS and XRD. The thermal stability of the sample was also evaluated. The electrical conductivity and electromagnetic shielding effect were systematically tested. In addition, other properties which related to practical application like washing fastness, bending fastness and chemical resistance were investigated as well. 2. Experimental 2.1. Materials The polyimide fabric (PI, Kylon Suplon, 200 g/m2) was purchased from Jiangsu Aoshen New Materials Co., Ltd. and was precisely cut into pieces of 4 cm
4 cm in size. Aniline (AN) monomer, nitric acid, ammonium chloride, ammonium persulfate (APS), palladium chloride, nickel sulfate hexahydrate, sodium citrate, and sodium hypophosphite were obtained from Sino pharm Group Chemical Reagents Co., Ltd. Sodium tungstate dihydrate was purchased from Shanghai Titan Technology Co., Ltd. All reagents were of analytical grade and were used without further purification unless otherwise mentioned. 2.2. In-situ polymerization of PANI and palladium chloride activation Firstly, pristine PI fabric was cleaned under 80  C for 10 min to remove oils and particulates covering the fiber surfaces, typically, liquor to material ratio 1:50; then it was completely rinsed by

distilled water and dried in an oven. Secondly, the PANI/PI fabric was prepared by in-situ polymerization of aniline monomers. The pre-treated PI fabric was immersed in a monomer solution containing 0.25 mol/L AN monomer and 0.5 mol/L HNO3 under 25  C for 60 min in order to fully adsorb AN monomer in the fiber gap. Next, 0.25 mol/L ammonium persulfate (APS) was dissolved in the above-prepared solution as an oxidizing agent to oxidize the small molecule aniline monomer to a polymer, which was carried out at room temperature for 3 h. Finally, the PANI/PI fabric was taken out and washed with deionized water and dried at a constant temperature. The PANI/PI fabric was prepared, and then placed in 1 g/L PdCl2 solution at room temperature for 1 h, in order to restore Pd2þ to Pd0 as a catalytically active center. 2.3. Ni-W-P electroless plating The electroless plating was carried out immediately after Pd0 activation. The electroless bath composition were sodium tungstate dihydrate (15 g/L), nickel sulfate hexahydrate (22.5 g/L), sodium hypophosphite (27.5 g/L), sodium citrate (25 g/L), and ammonium chloride (30 g/L), lactic acid (5 m$props_value{literPattern}/L). The as-prepared fabric was immersed into the solution, pH ¼ 9, liquor to material ratio 1:50, stirred for 2 h at 90  C. Involved reactions are displayed as the follows:

Ni2þ þ 2e /Ni   WO2 4 þ 6e þ 4H2 O/W þ 8OH þ  H2 PO 2 þ 2H þ e /P þ 2H2 O 2   H2 PO 2 þ 3OH /HPO3 þ 2H2 O þ 2e

Then, the Ni-W-P/PANI/PI fabric was washed by distilled water and dried at room temperature. Finally, the Ni-W-P/PANI/PI fabric composite with layered structures was obtained. The whole preparation routin was displayed in Fig. 1. 2.4. Characterization and measurement The surface morphology of samples was observed using Scanning electron microscope (SEM, TM-1000, Hitachi). The chemical composition of the fabric surface at various stages of electroless plating was determined using an energy dispersive spectrometer (EDS, IE 3000, UK) attached to a SEM. The surface electronic state of the sample was refracted to X-ray photoelectron spectroscopy (XPS) testing using a Thermo Escalab 250Xi spectrometer equipped with an Al anode (AlK ¼ 1486.7 eV). Thermogravimetric analysis (TGA) was performed in 209 F1 analyzer (Netzsch, Germany) at N2 atmosphere with a heating rate of 10  C/min and the temperature was ranged from 30  C to 900  C. X-ray diffraction (XRD, D/Max2550, Rigaku, Japan) was used to observe the crystal structure of samples at room temperature with 2q ranges from 5 to 90 . The conductivity of Ni-W-P/PANI/PI fabric was measured using a fourpoint probe square resistance tester (Daming Instrument Co., Ltd., Nanjing, China). The electromagnetic shielding effectiveness was assessed by DR-913 anti-electromagnetic radiation tester (Wenzhou Darong Textile Co.). Furthermore, the corrosion resistance was tested by the changes of the electrical conductivity and SE of the samples in different pH solutions with treatment for 12 h. The wash fastness was measured by placing the Ni-W-P/PANI/PI fabric in an ultrasonic cleaner (SY-180, Shanghai, Chengxian Co., Ltd) [36]. Measure the bond strength between metal layer and fiber using standard transparent tape method. In addition, fabric thickness was

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Fig. 1. Preparation of Ni-W-P/PANI/PI fabric.

measured by a spiral micrometer (Nanjing Suce Instruments Co., Ltd). The weight increasing percentage was calculated by the following equation [37].

u¼

m2  m1
100% m1

(1)

where u is the weight increasing percentage, m1 the mass (g) of PANI/PI fabric, and m2 the mass (g) of Ni-W-P/PANI/PI fabric. 3. Results and discussion 3.1. Surface morphology observation Fig. 2 depicted the SEM micrographs of PI fabric, PANI/PI fabric, PdCl2 reduced PANI/PI fabric and Ni-W-P/PANI/PI fabric. The upper right corner of each SEM image corresponds to the optical photos of the fabric. Fig. 2(a) showed that after the pre-treatment of the PI fabric, the oil was removed and grooves were formed on the surface of the fiber, which provided a larger surface area for the attachment of the aniline monomer, thereby increasing the adhesion fastness. It can be seen that PANI/PI fabric was relatively rougher owing to the existence of PANI in Fig. 2(b), and silver-white palladium particles

were reduced by PANI and evenly distributed as show in Fig. 2(c). In Fig. 2(d), the fibers were completely wrapped by the compact and uniform Ni-W-P alloy layer. 3.2. EDS analysis From the following figure, it can be seen that the four different phases in the electroless plating process correspond to the changes in the content of several elements, the further information of fabric surface could be obtained. Comparing Fig. 3(a) and Fig. 3(b), it can be found that the relative content of oxygen was decreased, and conversely, the relative content of nitrogen was increased, which was attributed to the fact that the relative content of nitrogen in polyaniline was larger than PI fabric and that oxygen was not contained in polyaniline. The above data once again demonstrated the in-situ polymerization of polyaniline on the fiber surface. As seen in Fig. 3(c), the peak of palladium was clearly observed. Although its content was low as 4.06% and atomic percentage was 0.51%, it was sufficient to initiate electroless plating. It needs to be explained here that the presence of chlorine was due to the activation of palladium chloride. It can be seen from Fig. 3(d) that only the Ni-W-P element were detected and the carbon-oxygennitrogen element disappeared, which can be explained by the fact that the Ni-W-P metal layer was sufficiently thick and the detection thickness of the instrument was limited, further indicating that the presence of the Pt element was because of the platinum spray before the test. In summary, this demonstrated that the fibers were completely covered by a uniform and dense Ni-W-P alloy layer. 3.3. XPS analysis

Fig. 2. SEM images and optical photos of PI fabric (a), PANI/PI fabric (b), PdCl2 reduced PANI/PI fabric (c), and Ni-W-P/PANI/PI fabric (d).

The elemental composition and chemical state on the surface of the fabric were further analyzed by XPS. As shown in Fig. 4, (a), (b), (c), and (d) are XPS spectrum of PI fabric, PANI/PI fabric, PdCl2 reduced PANI/PI fabric and Ni-W-P/PANI/PI fabric, respectively. Comparing (a) and (b), it is obvious that the peak of (b) relative to the (a) nitrogen element increased, the atomic ratio increased from 2.49% to 6%. Moreover, the XPS spectrum of N1s with three decomposed peaks is shown in Fig. 4(b), the fitted peaks at 399.8eV and 399.2 eV belong to benzenoid diamine nitrogen (eNH-) and quinoid di-imine (-N¼), respectively. The corresponding nitrogen peak at 400.9 eV indicated positively charged nitrogen (Nþ) in the acid-doped PANI structure [38,39]. The above results were consistent with the SEM and EDS test. A weak peak of Pd3d appeared in Fig. 4(c) as its atomic ratio is only 0.28%. The peaks at 335.9 eV and 341.3 eV could be corresponding to respectively a Pd 3d5/2 signal and a Pd 3d3/2 signal, which confirmed that the Pd species were

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Fig. 3. EDS spectra of PI fabric (a), PANI/PI fabric (b), PdCl2 reduced PANI/PI fabric (c) and Ni-W-P/PANI/PI fabric (d).

mainly existed as metallic Pd (Pd0) [40,41]. This again demonstrated the formation of a palladium catalytically active center. The peaks of Ni and W can be observed from the XPS spectrum of the Fig. 4(d). The Ni 2p spectrum showed a 2p1/2 peak at around 873.3 eV with a satellite at 879.9 eV and a Ni 2p3/2 peak at around 856.1 eV with a satellite at 861.5 eV [40]. The high-resolution W 4f spectrum showed a 4f 7/2 peak at around 37.6eV and a W 4f 5/2 peak at around 35.6 eV can be attributed to metallic W and W6þ [42].

3.4. XRD analysis The typical XRD patterns for PI fabric, PANI/PI fabric, PdCl2 activated fabric and Ni-W-P/PANI/PI fabric were represented in Fig. 5. It can be seen that the XRD pattern for pristine PI fabric showed three peaks (located at 2q ¼ 14.32 , 18.31, and 26.22 ) [43]. Comparing (a) and (b), it can be concluded that PANI has no significant effect on the crystal structure of PI fiber macromolecules as PANI was amorphous. A comparison of (c) and (b) shows that the

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Fig. 4. XPS spectrum of PI fabric (a), PANI/PI fabric (b), PdCl2 reduced PANI/PI fabric (c) and Ni-W-P/PANI/PI fabric (d).

crystallinity of the PANI/PI fabric decreases after palladium activation. Moreover, the diffraction peak at 2q ¼ 44.536 was the

reflection of nanocrystalline Ni (111), which corresponded to Ni (111) of the faced centered cubic (FCC) crystalline phase (JCPDS 04e0850) [30]. By comparison of curve (d) and curve (a, b, c), only the characteristic diffraction peak of nickel (111) appears, indicating that the fabric had been completely covered by the alloy layer. The crystalline size of the coating was calculated by the Scherrer formula: t ¼ nl/bcosq, where t, n, l, b and q, represent mean crystalline size, Scherrer constant (0.89), Cu Ka radiation wave-length (usually 0.154 nm), full width half maximum at 2q, diffraction angle, respectively [11]. Calculating from the formula and the particle size was found to be 10.11 nm. In addition, P was not detected in the alloy coatings because of its amorphous phase in nature. Similarly, it was noticed that there was no tungsten or any tungsten compound reflection from Fig. 5, the same phenomenon was also appeared in related research [35].

3.5. TGA analysis

Fig. 5. XRD patterns of PI fabric(a), PANI/PI fabric (b), PdCl2 reduced PANI/PI fabric (c), and Ni-W-P/PANI/PI fabric (d).

In order to analyze the thermal stability of the PI fabric, PANI/PI fabric, PdCl2 reduced PANI/PI fabric, and Ni-W-P/PANI/PI fabric, TGA was used at N2 atmosphere with a heating rate of 10  C/min and the temperature was ranged from 30  C to 900  C. As demonstrated in Fig. 6(a), it is obvious that the first decomposition reaction of PI fabric occurred in the range of 126 Ce206  C, which was due to the decomposition of some impurities and oligomers at this temperature range, and the residual contents were more than 90.8%. As shown in Fig. 6, four samples all started thermal degradation from 546  C, with the increase of temperature, the quality of the residue

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Fig. 6. TGA curves of PI fabric (a), PANI/PI fabric(b), PdCl2 reduced PANI/PI fabric (c), and Ni-W-P/PANI/PI fabric (d).

decreases rapidly, which is related to the degradation of polyimide macromolecular chains. However, decomposition rate of the sample tends to be slow after 620  C. The residual components of these three samples at 900  C were 53.8%, 62.4%, 59.7% and 85.9%, respectively. It could be deduced from the results that the content of Ni-W-P plating was about 62.5%. The result was basically consisted with weight increasing value 60.8% calculated according to equation (1). 3.6. Shielding effectiveness and electrical conductivity Numerous studies have shown that the shielding effectiveness (SE, an important indicator for electromagnetic interference) is the summation of reflection, absorption, and multiple internal reflections [44,45], which can be expressed by the following equation, SEðdBÞ ¼ SER þ SEA þ SEMR . Here, SER, SEA and SEMR represent reflection, absorption, and multiple internal reflections, respectively. The shielding mechanism of Ni-W-P/PANI/PI composite fabric satisfies the above equation, as shown in the following Fig. 7. As shown in Fig. 8(A), shielding effectiveness (SE) under electromagnetic radiation ranging from 300 kHz to 3 GHz, in which curve (a), (b), and (c) represented PI fabric, PANI/PI fabric, Ni-W-P/ PANI/PI fabric, respectively. The existence of PANI and the Ni-W-P alloy layer imparted electrical conductivity to the insulating PI

fabric. The surface resistance of PANI/PI fabric and Ni-W-P/PANI/PI fabric measured with a four-point probe were 1.10U/sq and 0.08U/ sq, respectively. As reported, good electrical conductivity indicates excellent SE performance [26], the SE of resultant fabric reaches 65e105 dB as we expected, the favorable SE are mainly attributed to the wave-absorption of PANI and the wave-reflection of Ni-W-P alloy layer. In order to investigate the corrosion resistance of the NiW-P alloy layer, a composite fabric was divided into three equal parts and soaked in solutions with different pH values for 12 h. The electrical conductivity of the fabric was averaged over 10 tests and shown in Fig. 8(B). The surface resistances of the three samples after the different treatments have slightly increased to some extent, due to the corrosive ions embedded in the dense nickeltungsten-phosphorus alloy layer. In sum, the resultant fabric maintained good conductivity after chemical resistance tests. As can be seen from Fig. 8(C) and (D), in which (a), (b), (c), (d) and (e) represented Ni-W-P/PANI/PI fabric and after 0, 100, 300, 500,1000 bending tests, respectively. With the increasing of the bending numbers, the SE and electrical conductivity of the resultant fabric have no obvious decrease and confirmed that this textile-based shielding material have good resistance to bending or reformation. The SEM image in the illustration shows that the metal layer wrapped on the fiber does not rupture significantly. It is worth noting that after 300 bending tests, the SE and the electrical conductivity decreased slowly. After 1000 bending tests, the peak SE reached 90 dB and the surface resistance was less than 0.15U/sq. As shown in Fig. 8(E), wherein (a), (b), (c), (d), (e) and (f) represent SE of Ni-W-P/PANI/PI fabric, corresponding to ultrasonic cycle water washing 0, 1, 3, 5, 10, 20 times. Fig. 8(F) showed the surface resistance of the fabric after repeated washing cycles. To electrically conductive or electromagnetic materials, this test is still challenge so far, as during the washing most of the conductive layer will deteriorate seriously. This is also the reason why this kind materials cannot be used in practical daily wear or not durable in long-term service. In experiments, we found after the first cycle of washing, the SE and electrical conductivity were reduced sharply, while after 3, 5, 10, 20 cycles of water washing, the SE and electrical conductivity were only slightly decreased. This is due to the loosely parts or redundant metal particles has been washed away in the first washing cycle. For confirmation, the SEM test of the composite fabric after water washing was conducted and a little crack was found in a part of the metal layer. Over all, it could remain above 55e90 dB with the surface resistance of 0.14U/sq after 20 cycles of water washing, which fully demonstrated that the fiber coated with Ni-W-P alloy layer has excellent washing fastness and these results have not been reported by other papers so far. As shown in Fig. 8(G), the DHU-shaped composite fabric acts as a guidewire, the small

Fig. 7. Electromagnetic shielding mechanism of Ni-W-P/PANI/PI fabric.

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Fig. 8. (A) a, b, c represent the SE of PI, PANI/PI, Ni-W-P/PANI/PI fabrics; (B) is the conductivity of the three samples before and after corrosion resistance test; (C) and (D) represent the SE and electrical conductivity of 0, 100, 300, 500 and 1000 bending tests, respectively; (E) and (F) represent the SE and electrical conductivity of 0, 1, 3, 5, 10, 20 cycles of ultrasonic washing; (G) Composite fabric as a wire forming a pathway to light two small bulbs.

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Fig. 9. (A), (B), and (C) are PI, PANI/PI, Ni-W-P/PANI/PI fabrics thickness tests, respectively; (D) is a photo showing the lightweight of the composite fabric; (E) and (F) are Scotch-tape test, the illustration is an SEM picture of the corresponding fabric.

Table 1 Comparison of the different composite fabric for EMI shielding. Composite fabric

Working components

Substrate

Shielding effectiveness(dB)

Refs.

Ni-W-P/PANI/PI Cu/PPy/CF Ni/PPy/LF Ag/PANI/PI Co-Ni/PANI/Lyocell Ag/PANI/PET Ni/PANI/PET

Ni-W-P and PANI Cu and PPy Ni and PPy Ag and PANI Co-Ni and PANI Ag and PANI Ni and PANI

Polyimide fabric (PI) Cuprammonium fabric Linen fabric (LF) Polyimide fabric (PI) Lyocell fabric Polyester fabric (PET) Polyester fabric (PET)

65-105(0.3e3000 MHz) 30.3e50.4(30e1000 MHz) 20.22e43.51(30e1000 MHz) 54-90(0.3e3000 MHz) 33.95-46.22(8000e12000 MHz) 50-90(0.3e3000 MHz) 40-45(30e2500 MHz)

This work [12] [46] [27] [47] [26] [13]

bulbs in series emitted light after the switch was closed, which confirmed that the resultant fabric has excellent conductivity. 3.7. Thickness of resultant fabric and adhesion test

following Table 1. Obviously, we have prepared Ni-W-P/PANI/PI composite fabric with more robust SE compared with other studies, which means that the resultant fabric of this work can meet the higher electromagnetic shielding requirements of aerospace and other military fields.

As demonstrated in Fig. 9(A), (B) and (C), the thicknesses of PI, PANI/PI and Ni-W-P/PANI/PI were respectively measured using a spiral micrometer, and their values were 0.298 mm, 0.380 mm and 0.487 mm, respectively. It can be calculated that the thickness of the polyaniline and nickel-tungsten-phosphorus alloy layers were 0.082 mm and 0.107 mm, respectively. A slight increase in thickness, but it does not change the flexibility or hand feeling of the fabric. Similarly, this lightweight fabric can be placed at the end of a palm branch without deforming it, as shown in Fig. 9(D). As an electromagnetic shielding protective fabric, the fastness of the NiW-P metal layer is one of the most important parameters. This was measured using the Scotch-tape test. The tape (Polar bear Tape, CC-188, 18 mm
18 m) was completely attached to the composite fabric, as shown in Fig. 9(E), and then peeled off quickly. Compared with Fig. 9(E) and (F), the SEM image shows that only a small amount of particles on the outside of the metal layer were peeled off, and the entire metal layer remains intact. This resultant fabric was shown to have excellent adhesion fastness.

High-performance PI fabric with electromagnetic shielding performance and electrical conductivity was designed by combining wave-absorbing conductive polymer PANI and wavereflective alloy Ni-W-P layer. Uniform and dense Ni-W-P alloy layer on PI fabric were verified by SEM, XRD, XPS and EDS. The surface resistance of resultant fabric was 0.08 U/sq and the SE of resultant fabric reached 65e103 dB, which is far superior to other related research in the field of electromagnetic shielding and makes it possible to apply in high-precision areas. After multiple cycles of ultrasonic washing, bending and adhesion tests, the resultant fabric can maintain robust SE and electrical conductivity, also indicating the firm adhesion of Ni-W-P alloy layer to the substrate. These superior properties demonstrate the Ni-W-P/PANI/PI fabric has a great potential when applied in long-term practical protection fields.

3.8. Comparison of SE performance of fabrics with other reports

Acknowledgements

The flexible and lightweight fiber-based supported conductive polymer materials and metal layers have become hot spots in the field of electromagnetic shielding due to their dual properties of absorption and reflection. Here, we reviewed the relevant literature and focused on the performance of this resultant fabric with layered structure. The specific parameters were shown in the

The research was supported by National Science Foundation of China (NSFC) (No. 51403032).

4. Conclusions

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