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CNTs composites produced by DC electrophoresis
Applied Surface Science 255 (2009) 8359–8362
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Field emission characteristics study for ZnO/Ag and ZnO/CNTs composites produced by DC electrophoresis Yu Ling-mina,b,*, Zhu Chang-chuna a b
School of Electronic and Information Engineering, Institute of Vacuum Microelectronics & Microelectro-mechanical System, Xi’an Jiao Tong University, PR China School of Materials and Chemical Engineering, Xi’an Technological University, PR China
A R T I C L E I N F O
A B S T R A C T
Article history: Received 30 December 2008 Received in revised form 20 May 2009 Accepted 24 May 2009 Available online 23 June 2009
A simple controllable method is reported for the coating of ZnO nanowires with Ag nanoparticles and ZnO/carbon nanotubes (CNTs) composite. It has been achieved through DC electrophoresis AgNO3 electrolyte and CNTs in the presence of isopropanol dispersion of ZnO nanowires. In the present work, the influence of Ag nanoparticles and CNTs on the field emission properties of the composite materials is studied. The results of this research demonstrate a remarkable enhancement of field emission current of ZnO nanowires in case of CNTs mixture and Ag nanoparticles coating. ß 2009 Elsevier B.V. All rights reserved.
Keywords: ZnO nanowires Ag nanoparticles CNT Field emission Electrophoresis
1. Introduction The excellent field emission property is the most important feature of ZnO-based 1D nanomaterials. ZnO nanowires are prior to carbon nanotubes in chemical stability and structural rigidity. Therefore, ZnO has demonstrated to be extremely useful for the development of new field emission display (FED) electrode materials [1]. Various methods and technologies for fabrication of FED cold cathodes are used nowadays, for example, chemical vapor deposition [2–4] and screen printing technologies [5–7]. However, the problems of these technologies are obvious, for example, there are high complexity and high cost of the technological process for the CVD and failure to large scale application because of vacuumproof binders for printing technologies [8]. One of the promising methods of ZnO nanowires based cold cathode fabrication is the electrophoresis method [9–11]. It has been reported [12] that a composite of Ag with f-MWCNTs is prepared by electrophoresis of f-MWCNTs and anodic dissolution of Ag electrode simultaneously in a single bath. However, little research has focused on ZnO nanowire composites for FED cathode material.
* Corresponding author at: School of Electronic and Information Engineering, Institute of Vacuum Microelectronics & Microelectro-mechanical System, Xi’an Jiao Tong University, Xian Ning West Road No. 28, Xi’an, Shan Xi 710049, PR China. Tel.: +86 029 83208231; fax: +86 029 83208078. E-mail address: [email protected] (L.-m. Yu). 0169-4332/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.05.109
In the present paper, the excellent field emission properties of Ag nanoparticles—coating of ZnO nanowires and ZnO/CNTs composite obtained by electrophoresis deposition are firstly reported. 2. Experimental The experimental setup consisted of an indium tin oxide (ITO) glass cathode, a graphite anode and a DC power supply. ZnO nanowires were synthesized by thermal evaporation method. Firstly, these raw ZnO nanowires were dispersed in isopropyl alcohol solution that contained a little dissolved Mg(NO3)26H2O and AgNO3. Secondly, the ZnO nanowire suspension was agitated by magnetic stirrer for 1 day. Then, the electrophoresis process was carried out, in which ITO glass plate (3 cm 4 cm) was used as cathode and graphite plate was employed as the counterelectrode. The compositions could be controlled by simple variables like current, voltage and time. The experiments were repeated for dispersions of ZnO nanowires and grinded CNTs, keeping other parameters unaltered. To enhance the adhesion of ZnO nanowires to the substrate, the cathode was immersed in the inorganic solution of Na2SiO3 when the electrophoresis process terminated. Finally, heat treatment was performed in the baking furnace at 350 8C for 30 min in an ambient of air. Field emission measurements were performed with diode structure in a vacuum chamber under a pressure of 1.8 10 5 Pa at room temperature. The cathode was separated from a green phosphor/ITO/ glass by two Teflon spacers with thickness of 200 mm.
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Fig. 1. SEM images for (a) pure ZnO nanowires obtained by thermal evaporation; (b) the ZnO/Ag nanowires by electrophoresis; (c) ZnO/CNTs composites deposited at cathode; (d) the magnified CNT referred by red arrow in Fig. 1c.
3. Result and discussion Fig. 1a shows the SEM images of the as-prepared ZnO nanocrystals obtained by thermal evaporation as direct deposition. It indicates that the major direct deposition products are consisted of disordered-orientation nanowires with 50–100 nm in diameter and tens of micrometers in length, while a minority of cusped-edge nanoplate hybridization presented among the nanowires. Fig. 1b shows SEM images recorded on the products obtained by electrophoresis ZnO nanowires with AgNO3 electrolyte. A coating of spherical Ag nanoparticles about the size of 80 nm seems to be attached to ZnO nanowire and cusped-edge nanoplate. Fig. 1c shows the composition obtained by electrophoresis of ZnO nanowires and CNTs, which reveals virtually endless entangled bundle of CNTs and ZnO nanowires concurrent lying on the substrate. Fig. 1d shows the magnified CNTs remarked by red arrow in Fig. 1c, which exhibites severe glomeration. XRD has been used to get the structural information about the compositions obtained by electrophoresis deposition. Fig. 1a shows the typical XRD spectrum of Ag coated ZnO nanowires, from which it is found that the diffraction peaks can be indexed to the hexagonal wurtzite structure ZnO and a new Ag phase with the face-centered cubic structure, indicating that Ag phase comes from AgNO3 electrolyte in the course of the heat treatment. Fig. 2b shows the typical XRD spectrum of the composition of ZnO/CNTs by dispersion of ZnO nanowires and CNTs in the suspension during the electrophoresis deposition. It is indicated that all diffraction peaks can be indexed to the hexagonal wurtzite structure ZnO, graphite-2H-C and In2O3 respectively, where grahite-2H-C is attributed to CNTs and In2O3 is origined from the substrate.
Fig. 2. XRD pattern of (a) Ag-coated ZnO nanowires; (b) ZnO/CNTs composites.
L.-M. Yu, C.-C. Zhu, et al. / Applied Surface Science 255 (2009) 8359–8362
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Fig. 3. Field emission properties of (a) Ag coated ZnO nanowires; (b) ZnO/CNTs compositions; (c) emission image from ZnO/CNTs compositions with an anode voltage of 1000 V.
Fig. 3 illustrates the curves of field emission current versus electric field from the different ZnO nanowire compositions. The emission current is measured by applying voltage increasing from 0.05 to 1 kV with a sweep step of 50 V. As shown in Fig. 3a, the current emitted from both pure ZnO nanowires and Ag coated ZnO nanowires rises sharply as the electric field increases up to a certain value. However, in the two types of ZnO nanostructures, the emission current of Ag coated ZnO nanowires is higher than that of pure ZnO nanowires, and it demonstrates that the turn-on field (corresponding to the current of 10 mA) of the Ag coated and pure ZnO samples is about 2.1 V/mm and 2.3 V/mm respectively. The I–V characteristic of ZnO nanowires/CNTs compositions is shown in Fig. 3b. The turn-on electric field is about 1.85 V/mm and the maximum current is approximately 218 mA at 5 V/mm of an applied electric field. Fig. 3c indicates the emission image from composition of ZnO/CNTs with an anode voltage of 1000 V. The uniform emission pattern is observed from the whole cathode area. The result in Fig. 3a shows that the field emission of the intrinsic ZnO nanowires is improved by fabricating Ag nanoparticles on it surface. Firstly, the work function of Ag is 4.8 eV, which is larger than ZnO. Therefore, a better ohmic contact can be generated between ZnO and Ag. Secondly, it is believed that there is a contact potential difference between the surface of ZnO and Ag nanoparticles, which generates a contact electric field directed from the surface of ZnO to Ag. Electrons can be easier to transmit from Ag nanoparticles to the surface of ZnO nanowires under the contact electric field. As a result, electron emitter region is formed at the
interface of ZnO nanowires and Ag nanoparticles, in which region electrons will be emitted preferentially. Accordingly, electron transport channel will be amplified by Ag nanoparticles coated on the surface of ZnO nanowires. It is the reason that making Ag coated ZnO nanowires exhibits a better field emission property. The reasons for the low turn-on field and large emission current of ZnO/CNTs are the well-graphitized structure of CNT which has low electrical resistivity and enough electrons to be emitted by applied field. Additionally, the electrons are significantly easier to diffuse from ITO to CNTs since the work function of CNTs is larger than that of ITO. Then, a negative space-charge region is generated at the surface of CNTs, resulting in an extremely higher surface electron concentration of CNTs compared to body electron concentration. Based on the analyses made above, it may be safely come to the conclusion that there is an ohmic contact between CNTs and ITO. Therefore, the excellent field emission properties of ZnO/CNTs composite are attributed to the combined effect of ZnO nanowires and CNTs. This approach provides a novel approach for future studies on the field emission display cathode material. 4. Conclusions In conclusion, two kinds of ZnO nanowire-based compositions are successfully obtained by a simple electrophoresis deposition. Field emission characteristics of both these two kinds of compositions and pure ZnO nanowires are measured and investigated. In the three types of ZnO-based nanostructures,
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the turn-on field of ZnO nanowires/CNTs is the lowest, and followed by Ag coated and pure ZnO nanowires. However, the emission current of ZnO nanowires/CNTs is the highest, whereas the current of Ag coated of ZnO nanowires is the second, and that of pure ZnO nanowires is the lowest, suggesting the combined effect of the field emission of ZnO nanowires and CNTs or Ag nanoparticles. Acknowledgements The work was supported by National Natural Science Foundation of China under Grant No. 60801022, 863-Programme of the Ministry of Science and Technology of China (No. 2008AA03A314) and Natural Science Foundation of Shan Xi Province No. 2008K06-11. References [1] H. Ham, G. Shen, J.H. Cho, T.J. Lee, S.H. Seo, C.J. Lee, Vertically aligned ZnO nanowires produced by a catalyst-free thermal evaporation method and their field emission properties, Chemical Physics Letters 404 (2005) 69–73. [2] L. Liao, J.C. Li, D.F. Wang, C. Liu, C.S. Liu, Field emission property improvement of ZnO nanowires coated with amorphous carbon and carbon nitride films, Nanotechnology 16 (2005) 985–989.
[3] S.Y. Li, C.Y. Lee, P. Lin, T.Y. Tseng, Gate-controlled ZnO nanowires for fieldemission device application, Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 24 (2006) 147–151. [4] S.M. Pimenov, V.D. Frolov, A.V. Kudryashov, M.M. Lamanov, Electron field emission from semiconducting nanowires [J], Vacuum 17 (2008) 758–763. [5] S.S. Park, J.M. Lee, S. Yoon II, Lee Dong Gu, Kim Sung Jin, Low-temperature synthesis of one-dimensional ZnO nanostructures on screen-printed carbon nanotube films, Physica E: Low-Dimensional Systems and Nanostructures 40 (2008) 2526–2530. [6] S. Yoon II, S.S. Kim, Y.K. Lee, Effects of constituents in CNT pastes on the field emission characteristics of carbon nanotubes, in: Proceedings of International Meeting on Information Display, Daegu, South Korea, August, (2006), pp. 1206– 1209. [7] S.J. Kyung, J.B. Park, B.J. Park, K.S. Min, J.H. Lee, The effect of Ar neutral beam treatment of screen-printed carbon nanotubes for enhanced field emission, Journal of Applied Physics 101 (2007) 083305. [8] D.A. Kurnosov, A.S. Baturin, A.S. Bugaev, K.N. Nikolski, R.G. Tchesov, Influence of the interelectrode distance in electrophoretic cold cathode fabrication on the emission uniformity, Applied Surface Science 215 (2003) 232–236. [9] Y.C. Wang, I.C. Leu, M.H. Hon, Preparation and characterization of nanosized ZnO arrays by electrophoretic deposition, Journal of Crystal Growth 237–239 (2002) 564–568. [10] F.Q. Tang, Y. Sakka, T. Uchikoshi, Electrophoretic deposition of aqueous nanosized zinc oxide suspensions on a zinc electrode, Materials Research Bulletin 38 (2003) 207–212. [11] S.J. Ciou, K.Z. Fung, K.W. Chiang, Behaviours and mechanism of electrolyte electrophoresis during electrophoretic deposition, Journal of Power Sources 175 (2008) 33–39. [12] K.M. Samant, V.R. Chaudhari, S. Kapoor, Filling and coating of multiwalled carbon nanotubes with silver by DC electrophoresis, Carbon 45 (2007) 2126–2129.
Contents lists available at ScienceDirect
Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc
Field emission characteristics study for ZnO/Ag and ZnO/CNTs composites produced by DC electrophoresis Yu Ling-mina,b,*, Zhu Chang-chuna a b
School of Electronic and Information Engineering, Institute of Vacuum Microelectronics & Microelectro-mechanical System, Xi’an Jiao Tong University, PR China School of Materials and Chemical Engineering, Xi’an Technological University, PR China
A R T I C L E I N F O
A B S T R A C T
Article history: Received 30 December 2008 Received in revised form 20 May 2009 Accepted 24 May 2009 Available online 23 June 2009
A simple controllable method is reported for the coating of ZnO nanowires with Ag nanoparticles and ZnO/carbon nanotubes (CNTs) composite. It has been achieved through DC electrophoresis AgNO3 electrolyte and CNTs in the presence of isopropanol dispersion of ZnO nanowires. In the present work, the influence of Ag nanoparticles and CNTs on the field emission properties of the composite materials is studied. The results of this research demonstrate a remarkable enhancement of field emission current of ZnO nanowires in case of CNTs mixture and Ag nanoparticles coating. ß 2009 Elsevier B.V. All rights reserved.
Keywords: ZnO nanowires Ag nanoparticles CNT Field emission Electrophoresis
1. Introduction The excellent field emission property is the most important feature of ZnO-based 1D nanomaterials. ZnO nanowires are prior to carbon nanotubes in chemical stability and structural rigidity. Therefore, ZnO has demonstrated to be extremely useful for the development of new field emission display (FED) electrode materials [1]. Various methods and technologies for fabrication of FED cold cathodes are used nowadays, for example, chemical vapor deposition [2–4] and screen printing technologies [5–7]. However, the problems of these technologies are obvious, for example, there are high complexity and high cost of the technological process for the CVD and failure to large scale application because of vacuumproof binders for printing technologies [8]. One of the promising methods of ZnO nanowires based cold cathode fabrication is the electrophoresis method [9–11]. It has been reported [12] that a composite of Ag with f-MWCNTs is prepared by electrophoresis of f-MWCNTs and anodic dissolution of Ag electrode simultaneously in a single bath. However, little research has focused on ZnO nanowire composites for FED cathode material.
* Corresponding author at: School of Electronic and Information Engineering, Institute of Vacuum Microelectronics & Microelectro-mechanical System, Xi’an Jiao Tong University, Xian Ning West Road No. 28, Xi’an, Shan Xi 710049, PR China. Tel.: +86 029 83208231; fax: +86 029 83208078. E-mail address: [email protected] (L.-m. Yu). 0169-4332/$ – see front matter ß 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2009.05.109
In the present paper, the excellent field emission properties of Ag nanoparticles—coating of ZnO nanowires and ZnO/CNTs composite obtained by electrophoresis deposition are firstly reported. 2. Experimental The experimental setup consisted of an indium tin oxide (ITO) glass cathode, a graphite anode and a DC power supply. ZnO nanowires were synthesized by thermal evaporation method. Firstly, these raw ZnO nanowires were dispersed in isopropyl alcohol solution that contained a little dissolved Mg(NO3)26H2O and AgNO3. Secondly, the ZnO nanowire suspension was agitated by magnetic stirrer for 1 day. Then, the electrophoresis process was carried out, in which ITO glass plate (3 cm 4 cm) was used as cathode and graphite plate was employed as the counterelectrode. The compositions could be controlled by simple variables like current, voltage and time. The experiments were repeated for dispersions of ZnO nanowires and grinded CNTs, keeping other parameters unaltered. To enhance the adhesion of ZnO nanowires to the substrate, the cathode was immersed in the inorganic solution of Na2SiO3 when the electrophoresis process terminated. Finally, heat treatment was performed in the baking furnace at 350 8C for 30 min in an ambient of air. Field emission measurements were performed with diode structure in a vacuum chamber under a pressure of 1.8 10 5 Pa at room temperature. The cathode was separated from a green phosphor/ITO/ glass by two Teflon spacers with thickness of 200 mm.
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Fig. 1. SEM images for (a) pure ZnO nanowires obtained by thermal evaporation; (b) the ZnO/Ag nanowires by electrophoresis; (c) ZnO/CNTs composites deposited at cathode; (d) the magnified CNT referred by red arrow in Fig. 1c.
3. Result and discussion Fig. 1a shows the SEM images of the as-prepared ZnO nanocrystals obtained by thermal evaporation as direct deposition. It indicates that the major direct deposition products are consisted of disordered-orientation nanowires with 50–100 nm in diameter and tens of micrometers in length, while a minority of cusped-edge nanoplate hybridization presented among the nanowires. Fig. 1b shows SEM images recorded on the products obtained by electrophoresis ZnO nanowires with AgNO3 electrolyte. A coating of spherical Ag nanoparticles about the size of 80 nm seems to be attached to ZnO nanowire and cusped-edge nanoplate. Fig. 1c shows the composition obtained by electrophoresis of ZnO nanowires and CNTs, which reveals virtually endless entangled bundle of CNTs and ZnO nanowires concurrent lying on the substrate. Fig. 1d shows the magnified CNTs remarked by red arrow in Fig. 1c, which exhibites severe glomeration. XRD has been used to get the structural information about the compositions obtained by electrophoresis deposition. Fig. 1a shows the typical XRD spectrum of Ag coated ZnO nanowires, from which it is found that the diffraction peaks can be indexed to the hexagonal wurtzite structure ZnO and a new Ag phase with the face-centered cubic structure, indicating that Ag phase comes from AgNO3 electrolyte in the course of the heat treatment. Fig. 2b shows the typical XRD spectrum of the composition of ZnO/CNTs by dispersion of ZnO nanowires and CNTs in the suspension during the electrophoresis deposition. It is indicated that all diffraction peaks can be indexed to the hexagonal wurtzite structure ZnO, graphite-2H-C and In2O3 respectively, where grahite-2H-C is attributed to CNTs and In2O3 is origined from the substrate.
Fig. 2. XRD pattern of (a) Ag-coated ZnO nanowires; (b) ZnO/CNTs composites.
L.-M. Yu, C.-C. Zhu, et al. / Applied Surface Science 255 (2009) 8359–8362
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Fig. 3. Field emission properties of (a) Ag coated ZnO nanowires; (b) ZnO/CNTs compositions; (c) emission image from ZnO/CNTs compositions with an anode voltage of 1000 V.
Fig. 3 illustrates the curves of field emission current versus electric field from the different ZnO nanowire compositions. The emission current is measured by applying voltage increasing from 0.05 to 1 kV with a sweep step of 50 V. As shown in Fig. 3a, the current emitted from both pure ZnO nanowires and Ag coated ZnO nanowires rises sharply as the electric field increases up to a certain value. However, in the two types of ZnO nanostructures, the emission current of Ag coated ZnO nanowires is higher than that of pure ZnO nanowires, and it demonstrates that the turn-on field (corresponding to the current of 10 mA) of the Ag coated and pure ZnO samples is about 2.1 V/mm and 2.3 V/mm respectively. The I–V characteristic of ZnO nanowires/CNTs compositions is shown in Fig. 3b. The turn-on electric field is about 1.85 V/mm and the maximum current is approximately 218 mA at 5 V/mm of an applied electric field. Fig. 3c indicates the emission image from composition of ZnO/CNTs with an anode voltage of 1000 V. The uniform emission pattern is observed from the whole cathode area. The result in Fig. 3a shows that the field emission of the intrinsic ZnO nanowires is improved by fabricating Ag nanoparticles on it surface. Firstly, the work function of Ag is 4.8 eV, which is larger than ZnO. Therefore, a better ohmic contact can be generated between ZnO and Ag. Secondly, it is believed that there is a contact potential difference between the surface of ZnO and Ag nanoparticles, which generates a contact electric field directed from the surface of ZnO to Ag. Electrons can be easier to transmit from Ag nanoparticles to the surface of ZnO nanowires under the contact electric field. As a result, electron emitter region is formed at the
interface of ZnO nanowires and Ag nanoparticles, in which region electrons will be emitted preferentially. Accordingly, electron transport channel will be amplified by Ag nanoparticles coated on the surface of ZnO nanowires. It is the reason that making Ag coated ZnO nanowires exhibits a better field emission property. The reasons for the low turn-on field and large emission current of ZnO/CNTs are the well-graphitized structure of CNT which has low electrical resistivity and enough electrons to be emitted by applied field. Additionally, the electrons are significantly easier to diffuse from ITO to CNTs since the work function of CNTs is larger than that of ITO. Then, a negative space-charge region is generated at the surface of CNTs, resulting in an extremely higher surface electron concentration of CNTs compared to body electron concentration. Based on the analyses made above, it may be safely come to the conclusion that there is an ohmic contact between CNTs and ITO. Therefore, the excellent field emission properties of ZnO/CNTs composite are attributed to the combined effect of ZnO nanowires and CNTs. This approach provides a novel approach for future studies on the field emission display cathode material. 4. Conclusions In conclusion, two kinds of ZnO nanowire-based compositions are successfully obtained by a simple electrophoresis deposition. Field emission characteristics of both these two kinds of compositions and pure ZnO nanowires are measured and investigated. In the three types of ZnO-based nanostructures,
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the turn-on field of ZnO nanowires/CNTs is the lowest, and followed by Ag coated and pure ZnO nanowires. However, the emission current of ZnO nanowires/CNTs is the highest, whereas the current of Ag coated of ZnO nanowires is the second, and that of pure ZnO nanowires is the lowest, suggesting the combined effect of the field emission of ZnO nanowires and CNTs or Ag nanoparticles. Acknowledgements The work was supported by National Natural Science Foundation of China under Grant No. 60801022, 863-Programme of the Ministry of Science and Technology of China (No. 2008AA03A314) and Natural Science Foundation of Shan Xi Province No. 2008K06-11. References [1] H. Ham, G. Shen, J.H. Cho, T.J. Lee, S.H. Seo, C.J. Lee, Vertically aligned ZnO nanowires produced by a catalyst-free thermal evaporation method and their field emission properties, Chemical Physics Letters 404 (2005) 69–73. [2] L. Liao, J.C. Li, D.F. Wang, C. Liu, C.S. Liu, Field emission property improvement of ZnO nanowires coated with amorphous carbon and carbon nitride films, Nanotechnology 16 (2005) 985–989.
[3] S.Y. Li, C.Y. Lee, P. Lin, T.Y. Tseng, Gate-controlled ZnO nanowires for fieldemission device application, Journal of Vacuum Science and Technology B: Microelectronics and Nanometer Structures 24 (2006) 147–151. [4] S.M. Pimenov, V.D. Frolov, A.V. Kudryashov, M.M. Lamanov, Electron field emission from semiconducting nanowires [J], Vacuum 17 (2008) 758–763. [5] S.S. Park, J.M. Lee, S. Yoon II, Lee Dong Gu, Kim Sung Jin, Low-temperature synthesis of one-dimensional ZnO nanostructures on screen-printed carbon nanotube films, Physica E: Low-Dimensional Systems and Nanostructures 40 (2008) 2526–2530. [6] S. Yoon II, S.S. Kim, Y.K. Lee, Effects of constituents in CNT pastes on the field emission characteristics of carbon nanotubes, in: Proceedings of International Meeting on Information Display, Daegu, South Korea, August, (2006), pp. 1206– 1209. [7] S.J. Kyung, J.B. Park, B.J. Park, K.S. Min, J.H. Lee, The effect of Ar neutral beam treatment of screen-printed carbon nanotubes for enhanced field emission, Journal of Applied Physics 101 (2007) 083305. [8] D.A. Kurnosov, A.S. Baturin, A.S. Bugaev, K.N. Nikolski, R.G. Tchesov, Influence of the interelectrode distance in electrophoretic cold cathode fabrication on the emission uniformity, Applied Surface Science 215 (2003) 232–236. [9] Y.C. Wang, I.C. Leu, M.H. Hon, Preparation and characterization of nanosized ZnO arrays by electrophoretic deposition, Journal of Crystal Growth 237–239 (2002) 564–568. [10] F.Q. Tang, Y. Sakka, T. Uchikoshi, Electrophoretic deposition of aqueous nanosized zinc oxide suspensions on a zinc electrode, Materials Research Bulletin 38 (2003) 207–212. [11] S.J. Ciou, K.Z. Fung, K.W. Chiang, Behaviours and mechanism of electrolyte electrophoresis during electrophoretic deposition, Journal of Power Sources 175 (2008) 33–39. [12] K.M. Samant, V.R. Chaudhari, S. Kapoor, Filling and coating of multiwalled carbon nanotubes with silver by DC electrophoresis, Carbon 45 (2007) 2126–2129.