Dielectric and mechanical properties of polyimide composite films reinforced with graphene nanoribbon

SCT-21795; No of Pages 6 Surface & Coatings Technology xxx (2016) xxx–xxx

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Dielectric and mechanical properties of polyimide composite films reinforced with graphene nanoribbon Xiaoxu Liu a,b,c,⁎, Yanpeng Li a, Wenmao Guo a, Xiaonan Sun a, Yu Feng c, Duo Sun b, Yuanyuan Liu b, Kai Yan b, Zhonghua Wu d, Bo Su b, Jinghua Yin b,⁎⁎ a

Heilongjiang University of Science and Technology, Harbin 150027, China School of Applied Science, Harbin University of Science and Technology, Harbin 150080, China Harbin institute of Technology, Harbin 150001, China d Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049, China b c

a r t i c l e

i n f o

Article history: Received 31 August 2016 Revised 10 November 2016 Accepted in revised form 14 November 2016 Available online xxxx Keywords: Dielectric Mechanical property Polyimide Graphene nanoribbon

a b s t r a c t Graphene nanoribbon (GNR) was introduced into in the polyimide (PI) composite films. The effects on dielectric and mechanical properties of PI/GNR composites were investigated. Results show that the dielectric and mechanical properties of the composite films are significantly enhanced compared to pure PI. This can attribute the excellent dispersion of and the strong interfacial interaction between GNR and the PI matrix. Tensile strength of PI/ GNR composite films shows a first increasing and then decreasing trend with increased GNR content. With 0.1 wt% loading, the tensile strength is increased from 120.1 MPa to 166.7 MPa, and the dielectric constant of PI/GNR composite film is decreased from 3.6 to 3.1 compared to pure PI, respectively. The success of this preparation is believed to afford new avenue for the development of high strength polyimide based composites. © 2016 Published by Elsevier B.V.

1. Introduction The research on polyimide (PI) based composites, thanks to their remarkable insulation properties, superior mechanical properties, excellent thermal stability, and good resistance to solvents, has been catching great attention [1–6]. With rapid development in some special applications, the properties of pure PI film need be enhanced to meet the extreme requirements. Recently, it was found that the mechanical, dielectric and electrical properties of PI films are significantly improved by the incorporation of some inorganic contents [7–9]. Graphene, an intriguing single-atom thick layered carbon material possessing outstanding properties, becomes very promising new material for PI based composites in various applications [10–16]. In that sense, graphene has been widely used as an effective content mixture to enhance mechanical and dielectric properties of PI [17,18]. At present, two methods, the solution-mixing and the in-situ polymerization, are used to prepare PI/graphene composites by incorporating the functionalized graphene. Liu et al. obtained the maximum mechanical property in PI/graphene oxide composite with 2 wt% graphene oxide, and the tensile strength and the Young's modulus increased 34% and 31%, respectively [19]. However, Tseng and co-workers found the mechanical property of PI/ ⁎ Corresponding author at: Heilongjiang University of Science and Technology, Harbin 150027, China. ⁎⁎ Corresponding author. E-mail address: [email protected] (X. Liu).

FG composite with 10 wt% FG enhanced (what perities?) slightly [20]. Shi et al. prepared (3-aminopropyl) trimethoxysilane (APTMS)-functionalized reduced graphene oxide (APTMS-rGO)/polyimide (PI) composite (APTMS-rGO/PI). The results exhibited that the uniform dispersion of APTMS-rGO increases the glass transition temperature and the thermal decomposition temperature and, the tensile strength of the composites with 0.3 wt% APTMS-rGO is 31% higher than that of pure PI, and Young's modulus is 35% higher than that of pure PI [17]. S. Ramakrishnan et al., reported that adding up to 2 wt% Graphene oxide (GO) to PI leads to an improvement in the storage modulus from 1.4 × 108 to 3.8 × 108 Pa and an improvement in the glass transition temperature from 317 to 323 °C over pure PI [21]. T. Huang et al., reported that the PI based composites with 2 wt% modified graphene exhibited a 20-fold increase in wear resistance and a 12% reduction in friction coefficient, constituting a potential breakthrough for future tribiological application [22]. These results show that the incorporation of graphene with PI matrix plays a crucial role for improving the mechanical property of resulting composites. Lots of studies have focused on the mechanical behavior of PI composites at a high graphene loading, however, few studies report the interfacial behavior and the mechanical property of PI/graphene composite at ultralow contents. Graphene nanoribbon (GNR), thin elongated strips of graphene, can be fabricated by unzipping carbon nanotubes [23]. The outstanding electronic and spin transport properties of GNR make them attractive materials in a wide range of device applications [24–27]. GNRs have been produced by several techniques including lithographic [28], chemical [29],

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sonochemical [30], and chemical vapor deposition (CVD) [31]. To the best of our knowledge, the preparation of composites with PI and graphene nanoribbon (GNR) has not been reported so far. In this paper, we evaluated the effects of the incorporation of GNR on mechanical, dielectric and electrical properties of PI composite. The results indicate that the GNR not only can dissolve in N, Ndimethylacetamide (DMAC) well, but also provide a starting platform for the in-situ fabrication of composite films. The PI/GNR composites exhibit a dramatic enhancement in mechanical properties at very low GNR doping. We found that the elongation at break and tensile strengths of synthesized PI/GNR composites is greatly enhanced in comparison with pure PI film. For example, with an incorporation of only 0.1 wt% GNR, the elongation at break is increased from 7.2% to 11.7%, which is N50% improvement compared to that of pure PI film. In addition, the volume resistivity and hydrophobic performance are also enhanced. The potential applications of PI/GNR composites with these enhanced properties are greatly increased in future. 2. Experimental setup 2.1. Synthesis of graphene nanoribbon The Formation of graphene nanoribbon from multiwalled carbon annotates(MWCNTs) is synthesized in two steps as previously described [29]. First, MWCNTs (150 mg) were suspended in 30 mL of concentrated H2SO4 for a minimum of 1 h and up to 12 h. KMnO4 (750 mg) was then added, and the mixture was constantly stirred for 1 h at room temperature. The reaction mixture was poured onto 100 mL of ice containing H2O2 (30%, 5 mL). The resulting light-brown colored precipitate was collected on a 200 nm pore size PTFE membrane, washed several times with HCl (20 vol%) and re-suspended in H2O by stirring for 2 h. Then HCl (30 vol%, 60 mL) was added to coagulate the product, which was then collected on the same PTFE membrane, washed several times with HCl (20%, 6 mL each), and dispersed in ethanol (40 mL) for 2 h with stirring. Then the product was again coagulated, filtered over the same PTFE membrane, washed several times with ether, and freeze dry to obtain graphene nanoribbon oxide. Second, graphene nanoribbon was prepared by high temperature annealing graphene nanoribbon oxide powder in Ar. 500 mg of graphene nanoribbon oxide powder was put in a tube furnace under a flow of Ar (50 sccm) and annealed for 1 h after reaching the desired annealing temperature (1000 °C).

The resulting sample was obtained after washing repeatedly with DI water and drying at 60 °C for 24 h. 2.2. In-situ synthesis of PI/GNR composite film The GNR (0.5 g) was dispersed in N, N-dimethylacetamide (DMAC) (500 mL) by ultrasonic mixing for 1.5 h, followed by centrifugation at 4000 rpm for 20 min to remove the precipitates. However, nearly no precipitate was found after that, indicating that most is well dispersed in DMAC. Equivalent molar ratios of 2 g 4, 4′-oxy dianiline (ODA) and 2.2 g pyromellitic dianhydride (PMDA) were dissolved in the GNR/ DMAC dispersion solution to make solutions containing 0.1, 0.3, 0.5, 1 and 3 wt% of GNR (compared to monomers), respectively. After that, viscous polymer solutions of polyamic acid (PAA)/GNR were obtained. The PAA/GNR solutions were then cast onto glass substrates and dried at room temperature overnight. Next, the PAA composite films were imidized through a sequence of heat treatments at 100, 200, 260, 310, and 350 °C, each for 1 h under nitrogen environment, forming the composite films (PI/GNR) with thicknesses of 30–40 μm (see Fig. 1). All chemicals were bought from the Sinopharm Chemical Reagent Co. Ltd. (china). 2.3. Measurements Cross section scanning electron microscope (SEM) images were obtained on a JEOL field-emission SEM machine, model JSM-6700F, at operating voltage of 15 kV. TEM was carried out on model JEOL JEM-2010. The small angle x-ray scattering (SAXS) experiments were carried out at beam line 4B9A at Beijing Synchrotron Radiation Facility. The storage ring was operated at 2.2 GeV with current about 80 mA. The incident X-ray wavelength was selected to be 0.154 nm by a double-crystal Si (111) monochromator. The tensile strength and elongation at break were measured on XLD-series liquid screen electronic tensile apparatus with specimens in accordance with GB/T13541-92 at a drawing rate of 50 mm/min. The average of five individual measurements is used with three significant digits, and the unit is MPa. The contact angles of water droplets on the films were measured using a goniometer (JY82) equipped with a camera to catch images of the water droplets on the surface of the PI composite films. The dielectric constant of hybrid PI films was tested using an impedance analyzer (Agilent 4294A) with 16451B Dielectric Test Fixture in the frequency range of 1–107 Hz. The

OAD,PDMA

0 ć, 5h

80

, 12h

Thermal Imidization

GNR/PI film

GNR/PAA film

Fig. 1. Schematic flow of in-situ polymerization processes for PI/GNR composite film preparation.

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DC volume resistivity measurements are performed using a Keithley electrometer with 8009 resistivity measurement kit at a voltage of 500 V. 3. Results Some thin elongated strips GNRs were shown in Fig. 2a, and the GNRs uniform dispersed in Polyimide matrix (see Fig. 2b). The SEM images of sample cross-sections were used to evaluate the dispersion and compatibility of GNR in a polyimide matrix. Fig. 2 also shows a crosssection SEM image of a cold fractured PI/GNR composite film containing 0.1 and 1 wt% GNR sheets. The PI/GNR composite containing 0.1 wt% GNR shows no obvious stripping and few defects in cross-section area (see Fig. 2c). The Fig. 2(d) shows a zoom-in view of the PI/GNR with the 0.1 wt% content cross section area that no distinguishable GNR layers are visible in the cross section SEM image of composite. However the homogeneously dispersed agglomeration of polyimide containing GNR is observed as indicated by the GNR in the SEM image, and all of the agglomeration are separated and sizes of the hybrid containing 0.1% GNR are b100 nm. Furthermore, the SEM image also shows the fracture surface of the composite film is rough. This could be attributed to the strong interfacial adhesion, as well as the good compatibility between the PI matrix and GNR sheets. Such strong interfacial bonding likely favors efficient stress transfer from the PI matrix to the GNR sheets and thus enhanced mechanical properties of the composite

(a)

3

films. As GNR content increased to 1 wt%, many small holes appear on the cross-sectioned surface and can be contributed to the GNR pulledouts, and GNR exhibits obviously aggregation due to the Van der Waals interaction between planar structures (See Fig. 2e and f). A three dimensional SAXS signal of a PI/GNR composite with a 0.1% GNR doping concentration is shown in Fig. 3(a). The PI/GNR composite films with different GNR doping concentrations have quite similar SAXS signals. The SAXS signal of a PI/GNR composite film possesses rotation symmetry, which implies that the composite material is isotropic. Thus, the scattering intensity can be converted into scalar function of the scattering vector due to its rotation symmetry. The characteristic of microstructure of PT/GNR can be studied by classic SAXS theory using the scattering signal as shown in Fig. 3(a) [32]. The plots of ln[q3I(q)] versus q2 from PI/GNR composite films with different GNR doping concentrations are given in Fig. 3(b). As shown in Fig. 3(b), the SAXS intensity plots of the PI/GNR composite films show negative deviations indicating the existence of the interface between GNR and PI molecular chains. We believe that the interaction between organic polymer molecular chains and inorganic GNR sheets leads to interfaces which are responsible to the deviations observed. It is quite obvious that thickness of interface was decreased with increasing of GNR doped concentration (see Fig. 3d), indicating heavy doping induced drastic change of electronic energy states. The fractal dimension parameter D is used to quantify the mass or the surface changes of the scatters in our previous reports [32,33]. The ln(I(q)) vs. ln(q) plots for all composites films, as

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Fig. 2. (a) the TEM image of GNR (b) the TEM images of PI/GNR with 0.1 wt% doping concentration; SEM images of a cross section view of PI/GNR films: (c, d) the PI/GNR with 0.1 wt% doping concentration; (e, f) the PI/GNR with 1 wt% doping concentration.

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Fig. 3. (a) Typical three dimensional image of SAXS, (b) The plots of ln[q3I(q)] versus q2, (c) Typical ln(I(q)) versus ln(q) plots, (d) the mass, surface fractal and interface from PI/GNR composite films with different GNR doping concentrations.

shown in Fig. 3c, clearly show that mass fractal (Dm) and surface fractal (Ds) coexist in the two specimens (which two?), from the slope changes. The mass and surface fractal data of two films from curve fitting were collected and are shown in Fig. 3d. The mass and surface fractal of the PI/ GNR composite containing only 0.3 wt% GNR is increased by up to max value. Increasing the GNR content from 0.3 to 3 wt% inversely decreases the fractal. It is indicated that the composite structure becomes looser with GNR content further increasing. PI is known for its excellent thermal and mechanical properties due to strong intermolecular interaction, known as inter-chain charge transfer complex electrical interaction [34]. The mechanical properties can be improved under doping GNR into polymer matrix (see Table 1). The mechanical properties of PI/GNR composite films are studied, as well, to gauge the impact of GNR doping. The tensile property improvements of PI/GNR composites are plotted in Fig. 4a, b. The typical stress–strain curves of PI/GNR composite which exhibit superior mechanical properties compared to that of pure PI films for various compositions are shown in Fig. 4(a). Increasing GNR doping concentration from 0.1 to 3 wt%, the tensile strength of PI/GNR films first increases to 166.7 MPa, then decreases down to131.1 MPa, as shown in Fig. 4(b). The tensile strength of the PI/GNR film containing 0.1 wt% of GNR loading is 38% higher than that of pure PI film. Meanwhile, the elongation at break of PI/GNR film containing 0.1 wt% GNR loading is 11.7%, which this is about 50.1% greater than that of pure PI film. The data in Fig. 4

indicates that the slight mixing of GNR (0.1 wt%) into PI matrix can greatly improve the mechanical properties of the PI/GNR composite. More important, such small amount of GNR mixing in mechanical property improvement of PI potentially means relatively low cost in practical applications. This mechanical property improvement of PI/GNR films over pure PI films is expected. We have been indirectly detected the GNR sheets coated PI molecules slight orientation inside PI films in SEM images, we suspect that, due to the PI/GNR composite casting and drying process (the film thickness shrank during drying), the GNR sheets have tendency to align with the film surface in less doping GNR to composite. Thus, the GNR sheets inside PI, not only help to strengthen the composite, but also hold PI together like net, which like strings holding PI polymers together and avoiding slippage under stress. As GNR sheets doping concentration increases, however, GNR sheets start cramping close together and the sheets' orientation alignment become more random; as result, the PI/GNR composite mechanical property degrades. Another effect as GNR doping increase is that the distance between its sheets gets smaller, and effectively, PI polymers are separated into thinner layers. Thus, as GNR sheets doping increases beyond a certain threshold (about 0.1 wt%), the enhancement of tensile strength and elongation at break of the PI/GNR composites is no longer there. Fig. 4c, d shows the dependence of the PI composite dielectric constant and loss tangent (from 1 to 1000 kHz) on increasing the GNR content, the incorporation of GNR increase the dielectric constant

Table 1 The mechanical and electrical property of polymer/GNR. Name

Stress (MPa)

Elongation at break (%)

Volume resistivity (Ω cm−1)

Ref.

Epoxy/GNR Functionalized GNRs GNR filled silicone rubber Polyurethane/GNR Polyimide/GNR

b70 b95 b0.4 b7 N7

b6 – b165 b50 N8

– – – – N1

[35] [24] [36] [37] This work

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Fig. 4. (a) Curves of tensile strength vs. strain, (b) The tensile strengths and elongation at break, (c) The dielectric permittivity, (d) loss tangent of the PI/GNR composites with different doping concentration.

obviously. However, the dielectric constant of PI/GNR films with 0.1 wt% content was reached to 3.1 lower than pure PI (about 3.4). Two-dimensional GNR would result in a large amount of heterostructure when they are embedded into PI matrices even at a very low filling. The dielectric confinement and strong self-polarization-induced radial localization of electronic density arising from the heterostructure between insulating and semiconducting components were likely to lead to remarkable decrease of dielectric constant. The dielectric loss of all PI/GNR films still remained very low (0.007) at 1000 Hz as shown in Fig. 4d. The low dielectric permittivity and dielectric loss will make the PI based composites more attractive for the practical applications in the future. Contact angle measurements on pure PI and PI/GNR films were carried out to evaluate the hydrophobic performance of each surface and the contact angle results are plotted in Fig. 5a. The contact angle of a

pure PI film is 61°, and increases with the presence of GNR. Contact angles of FG/PI films are slightly higher than that of pure film indicating the superior hydrophobic surface of PI/GNR compared to the pure PI, which can be attributed to the hydrophobic nature of GNR. The contact angles of the PI/GNR films are 65° (0.1 wt%), 69° (0.3 wt%), 71° (0.5 wt%), 75° (1.0 wt%) and 79° (3.0 wt%), respectively. The PI/GNR films exhibit a better hydrophobic property than that of a pure PI, which is also significant for the application of this film in electrical, electronics and microelectronics fields. Since PI films are primarily used for electrical insulation, the PI/GNR composite electrical property was checked as well. Fig. 5(b) shows the volume resistivity of the PI/GNR composite with different content of GNR. The volume resistivity of the PI/GNR composite was monotonically decreased from 4.1 to1.3 × 1016 Ω cm−1 with the increase of the GNR doping. In

Fig. 5. (a) Effect of GNR content on the contact angles of GNR/PI composite film (b) Dependence of volume resistivity on doping concentration of GNR.

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comparison to pure PI, the volume resistivity of the PI/GNR composite with 0.1 wt% of GNR is decreased modestly to about 4.0 × 1016 Ω cm−1, still satisfying the requirement in practice use. 4. Conclusions In conclusion, advanced PI/GNR composites films with excellent mechanical properties, low dielectric permittivity and acceptable resistivity have been fabricated by using in-situ polymerization method in low GNR doping. Incorporation The synergistic effect between layered GNR and PI matrix has been achieved, which make the GNR sheets provide great reinforcement to the PI composites at low doping. A PI/GNR composite film 0.1 wt% GNR as a functional filler, prepared by the same in-situ polymerization, exhibits the tensile strength of 166.7 MPa and the elongation at break of 11.7%, which are 38.2% and 50.1% higher than those of a pure PI film, respectively. We believed that the property enhancement in PI/GNR composite films in low GNR doping in this study provides the strong support for a potential material candidate in applications for electrical insulation, microelectronics and aerospace industries. Acknowledgements The authors would like to acknowledge support from the National Natural Science Foundation of China (Grant No. 51307046), Natural Science Foundation of Heilongjiang Province of China (Grant No. E2016062), Foundation of Harbin Science and Technology Bureau of Heilongjiang Province (Grant No. RC2014QN017034), the China Postdoctoral Science Foundation (General Financial Grant No. 2014M561345), the Heilongjiang Postdoctoral Science Foundation (LBH-Z14105), the Scientific Research Foundation for the Returned Overseas Chinese Scholars of the State Education Ministry (No. 20151098), the University Nursing Program for Young Scholars with Creative Talents in Heilongjiang province (No. 2015082), and the Open Project Program of the Key Laboratory for Photonic and Electric Band Gap Materials of the Ministry of Education of Harbin Normal University (No.PEBM201405). References [1] L. Ma, G.J. Wang, J.F. Dai, J. Appl. Polym. Sci. 133 (2016). [2] X. Liu, J. Yin, Y. Kou, M. Chen, L. Yuanyuan, J. Li, N. Zhang, Y. Lei, Z. Wu, B. Su, Nanosci. Nanotechnol. Lett. 7 (2015) 262–267. [3] L. Weng, L.W. Yan, H.X. Li, L.Z. Liu, J. Nanosci. Nanotechnol. 16 (2016) 1638–1644. [4] F. Ali, S. Saeed, S.S. Shah, F. Rahim, L. Duclaux, J.M. Leveque, L. Reinert, Recent Pat. Nanotechnol. (2016).

[5] Z. Xu, X. Zhuang, C. Yang, J. Cao, Z. Yao, Y. Tang, J. Jiang, D. Wu, X. Feng, Adv. Mater. 28 (2016) 1981–1987. [6] X. Liu, J. Yin, Y. Kong, M. Chen, Y. Feng, K. Yan, X. Li, B. Su, Q. Lei, Thin Solid Films 544 (2013) 352–356. [7] Z. Ahmad, J.E. Mark, Chem. Mater. 13 (2001) 3320–3330. [8] A.D. Adamczak, A.A. Spriggs, D.M. Fitch, W. Awad, C.A. Wilkie, J.C. Grunlan, J. Appl. Polym. Sci. 115 (2010) 2254–2261. [9] A. Alias, Z. Ahmad, A.B. Ismail, Mater. Sci. Eng. B 176 (2011) 799–802. [10] L.H. Hu, F.Y. Wu, C.T. Lin, A.N. Khlobystov, L.J. Li, Nat. Commun. 4 (2013). [11] X. Liu, J. Liu, D. Zhan, J. Yan, J. Wang, D. Chao, L. Lai, M. Chen, J. Yin, Z. Shen, RSC Adv. 3 (2013) 11601. [12] Z.S. Wu, W.C. Ren, L. Xu, F. Li, H.M. Cheng, ACS Nano 5 (2011) 5463–5471. [13] A. Sumboja, C.Y. Foo, X. Wang, P.S. Lee, Adv. Mater. 25 (2013) 2809–2815. [14] X. Liu, D. Chao, Y. Li, J. Hao, X. Liu, J. Zhao, J. Lin, H. Jin Fan, Z. Xiang Shen, Nano Energy 17 (2015) 43–51. [15] Y.W. Zhu, S. Murali, M.D. Stoller, K.J. Ganesh, W.W. Cai, P.J. Ferreira, A. Pirkle, R.M. Wallace, K.A. Cychosz, M. Thommes, D. Su, E.A. Stach, R.S. Ruoff, Science 332 (2011) 1537–1541. [16] X. Liu, D. Chao, Q. Zhang, H. Liu, H. Hu, J. Zhao, Y. Li, Y. Huang, J. Lin, Z.X. Shen, Sci. Rep. 5 (2015) 15665. [17] L. Cao, Q. Sun, H. Wang, X. Zhang, H. Shi, Compos. A: Appl. Sci. Manuf. 68 (2015) 140–148. [18] P. Zhang, J. Zhao, K. Zhang, R. Bai, Y. Wang, C. Hua, Y. Wu, X. Liu, H. Xu, Y. Li, Compos. A: Appl. Sci. Manuf. 84 (2016) 428–434. [19] D. Chen, H. Zhu, T.X. Liu, ACS Appl. Mater. Interfaces 2 (2010) 3702–3708. [20] I.H. Tseng, J.C. Chang, S.L. Huang, M.H. Tsai, Polym. Int. 62 (2013) 827–835. [21] S. Ramakrishnan, M. Dhakshnamoorthy, E.J. Jelmy, R. Vasanthakumari, N.K. Kothurkar, RSC Adv. 4 (2014) 9743–9749. [22] T. Huang, Y.S. Xin, T.S. Li, S. Nutt, C. Su, H.M. Chen, P. Liu, Z.L. Lai, ACS Appl. Mater. Interfaces 5 (2013) 4878–4891. [23] X. Li, X. Wang, L. Zhang, S. Lee, H. Dai, Science 319 (2008) 1229–1232. [24] R. Nadiv, M. Shtein, M. Buzaglo, S. Peretz-Damari, A. Kovalchuk, T. Wang, J.M. Tour, O. Regev, Carbon 99 (2016) 444–450. [25] Y. Gan, M. Feng, H. Zhan, Appl. Phys. Lett. 104 (2014) 171105. [26] M. Liu, Y. Du, Y.-E. Miao, Q. Ding, S. He, W.W. Tjiu, J. Pan, T. Liu, Nanoscale 7 (2015) 1037–1046. [27] Q. Ma, W. Yu, X. Dong, M. Yang, J. Wang, G. Liu, Sci. Rep. 5 (2015) 14583. [28] Z. Chen, Y.-M. Lin, M.J. Rooks, P. Avouris, Physica E Low Dimens. Syst. Nanostruct. 40 (2007) 228–232. [29] D.V.K. Amanda, L. Higginbotham, A. Sinitskii, Z. Sun, J.M. Tour, ACS Nano 4 (2010) 2059–2069. [30] A.L.H. Dmitry, V. Kosynkin, A. Sinitskii, J.R. Lomeda, A. Dimiev, B.K. Price, J.M. Tour, Nature 458 (2009) 872–876. [31] J.M.R.-H. Jessica Campos-Delgado, X. Jia, D.A. Cullen, H. Muramatsu, Y.A. Kim, T. Hayashi, Z. Ren, D.J. Smith, Y. Okuno, T. Ohba, H. Kanoh, K. Kaneko, M. Endo, H. Terrones, M.S. Dresselhaus, M. Terrones, Nano Lett. 8 (2008) 2773–2778. [32] L. Xiao-Xu, Y. Jing-Hua, S. Dao-Bin, B. Wen-Bin, C. Wei-Dong, W. Zhong-Hua, Chin. Phys. Lett. 27 (2010) 096103. [33] X. Liu, J. Yin, M. Chen, W. Bu, W. Cheng, Z. Wu, Nanosci. Nanotechnol. Lett. 3 (2011) 226–229. [34] G.Y. Kim, M.-C. Choi, D. Lee, C.-S. Ha, Macromol. Mater. Eng. 297 (2012) 303–311. [35] W.L. Mohammad, A. Rafiee, A.V. Thomas, A. Zandiatashbar, J. Rafiee, J.M. Tour, N.A. Koratkar, ACS Nano 4 (2010) 7415–7420. [36] L. Gan, S. Shang, C.W.M. Yuen, S.-X. Jiang, N.M. Luo, Compos. Part B 69 (2015) 237–242. [37] P.J.C. Changsheng Xiang, A. Kukovecz, B. Genorio, D.P. Hashim, Z. Yan, Z. Peng, C.-C. Hwang, G. Ruan, E.L.G. Samuel, P.M. Sudeep, X.R.V.Z. Konya, P.M. Ajayan, J.M. Tour, ACS Nano 7 (2013) 10380–10386.

Please cite this article as: X. Liu, et al., Surf. Coat. Technol. (2016), http://dx.doi.org/10.1016/j.surfcoat.2016.11.049