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Electrocatalytic action of nano-SiO2 with electrodeposited nickel matrix
Materials Letters 60 (2006) 1247 – 1250 www.elsevier.com/locate/matlet
Electrocatalytic action of nano-SiO2 with electrodeposited nickel matrix Wei-Yi Tu ⁎, Bin-Shi Xu, Shi-Yun Dong, Hai-dou Wang State Key Laboratory of Remanufacture Technology, Armored Force Engineering Institute, Beijing 100072, China Received 1 July 2005; accepted 4 November 2005 Available online 28 November 2005
Abstract The present work focuses on the electrocatalytic effect of nano-SiO2 on nickel electrodeposition and chemical interaction between nano-SiO2 and nickel in composite coating. The electrochemical behavior from n-SiO2/Ni composite brush plating system and quick nickel solution are investigated using cyclic voltammetry. The interaction between n-SiO2 particles and matrix metal nickel is researched by X-ray photoelectron spectrometry. The results show that the n-SiO2 take part in the electrode reaction during nickel electrocrystallization and can catalyze the nickel electrodeposition. The unsaturated bond of oxygen on n-SiO2 particles surface can capture some of the absorbed nickel atoms and form nickel– oxygen chemical bond. It is proved that the chemical binding interaction exists in the interface between nanoparticles surface and matrix metal nickel. © 2005 Elsevier B.V. All rights reserved. Keywords: Nanocomposite; Catalysts; Chemical binding; Composite brush plating
1. Introduction A kind of nanoparticles composite coating superior to the ordinary one has been developed by means of electro-brush plating. The performance of composite coating has an advantage over that of ordinary one considerably. The nanoparticles lead to the evident difference between the formation of composite coating and that of ordinary plating coating, influences structure and properties of composite coating [1,2]. This shows that the electrodeposition process for nanoparticles composite electro-brush plating has its characteristics and principle. The current investigation work is mainly focused on preparing coating, testing performance and developing new brush plating solution [3,4]. Little research has been done on the mechanism of electrodeposition and the influence of nanoparticles over it, which restricts the development of nanoparticles composite electro-brush plating technology. So the relating theoretic research must be done to reveal the mechanism of nanoparticles composite electro-brush plating, which will be of great significance for the technical design and application. ⁎ Corresponding author. E-mail address: [email protected] (W.-Y. Tu). 0167-577X/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2005.11.008
In this paper, the special attention is paid to the role of nanoparticle during the electrodeposition process. Liner sweep voltammetry is used for determining the electrochemical response from n-SiO2/Ni composite brush plating solution and quick nickel solution. The X-ray photoelectron spectrometry (XPS) from pure nickel and composite coating is measured. The results show that the nanoparticles take part in electrode reaction and can catalyze the nickel electrodeposition evidently. Nanoparticles and nickel atoms in the composite coating combine by means of chemical bond and they are not mixed together mechanically only [5]. 2. Experimental The nickel micro-disk electrode sealed in a glass tube was used as the working electrode with 1 mm diameter, the platinum plate was used as the counter electrode with size of 8 mm × 15 mm, and the saturation calomel electrode (SCE) was selected as the reference electrode. Potential was measured and quoted with relative to SCE. Electrochemical measurement was performed with Potentiostat/Galvanostat Model 273A (EG&G Instrumental Inc.). The computer controlled electrochemical system was used in recording the transient response.
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Fig. 1. Cyclic voltammograms measured with quickly nickel brush plating solution (a) and n-SiO2/Ni composite solution (b), scan rate 50 mV/s, potential range 0.00 to − 1.10 V.
Before each measurement, the nickel micro-disk electrode was polished with metallurgical coated abrasive paper to obtain a mirror surface, then ultrasonicated and thoroughly rinsed with distilled water, acetone and distilled water successively, and at last transferred to the brush plating solution without being dried. The solution was bubbled with N2 for 10 min before each experiment in order to eliminate the dissolved oxygen. The working electrode was held at potential 0.0 mV for 2 min before each measurement to ensure reproducible initial steady state at its surface. All experimental were performed at the temperature of 20 °C. All electrochemical experiments were performed in quick nickel plating solution or composite solution. The solution contained 264 g·L− 1 NiSO4·6H2O, 56 g·L − 1 ammonium citrate, 23 g·L− 1 ammonium acetate, 105 g·L− 1 ammonia water and 20 g·L − 1 n-SiO2. The original diameter of nanoparticles was 10 nm for nano-SiO2 powder. The pH of plating solution was about 7.2. All the solution was prepared from analytical grade reagents and distilled water. All coatings were prepared by using electric brush plating technology. DSD-75-S direct current power was used (Armored Force Engineering Institute). The technology procedure for preparing quick nickel and composite coating was as follows: electro-cleaning, activating, basing, quick nickel brush plating
Fig. 2. Steady polarization curves measured with quickly nickel brush plating solution (a) and n-SiO2/Ni composite solution (b). The inset is the corresponding Tafel curve.
Fig. 3. XPS spectrograms of nickel: (a) Ni coating, (b) n-SiO2/Ni composite coating.
or composite brush plating. The coating thickness was about 100 μm, the content of n-SiO2 by weight was about 0.72% and its diameter distributed at the range of 30–50 nm in composite coating [4]. XPS measurement was preformed by using ESCA LAB220I-XL (VG SCIENTIFIC). The position sensitive detector (PSD) and aluminium anode target were used with photon energy 1486.6 eV. The pressure in the vacuum room was kept at 2.9 × 10− 7 Pa. The C1s with energy 284.6 eV was used to calibrate spectral series displacement. Before experimental, the coating surface was mechanically polished to remove surface oxide and the fresh surface was exposed, then the sample was placed into the vacuum room immediately to measure. 3. Results and discussion 3.1. Catalytic effect of n-SiO2 on nickel electrodeposition The typical cyclic voltammograms were shown in Fig. 1; the steady-state polarization curves were depicted in Fig. 2. In Fig. 1, it was clear that the general shapes of the curves were similar, except for the overpotential and current efficiency. There was a little current response at the potential range of 0.0 V to −0.5 V. The current increased slowly below −0.85 V or − 0.87 V, then increased quickly for composite solution and quick nickel solution, respectively. In reverse scan process, the dissolution peak of nickel was at − 0.36 V in quick nickel solution and shifted slightly positively for composite solution. The current loops were found in Fig. 1, which indicated that the electrochemical nucleus process was underwent during nickel electrodeposition [6–9]. In Fig. 2, it was depicted distinctly that the overpotential of composite system was lower than that of quick nickel solution at the same currents, while the current was higher at the same potentials These facts showed that n-SiO2 took part in electrode reaction and could catalyze electrodeposition of nickel evidently. The main processes of metal electrodeposition included reactant transfer in liquid, interface reaction and electrocrystallization. The nSiO2 had no electrochemical activity itself and no electron exchange would happen between nanoparticle and electrode. Therefore, nanoparticles had no effect on the electron exchange reaction and their effect should be at the subsequent crystallization process.
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3.2. Combination between nano-SiO2 and matrix nickel in composite coating In general, it is considered that the second phase particle mixes with matrix phase only mechanically in composite coating [5]. In order to understand whether nano-SiO2 and nickel were combined in the composite coating chemically or mechanically, X-ray photoelectron spectrometry was used for analyzing the energy state of elements in coating [5]. The spectrograms of nickel element were depicted in Fig. 3 and the relative parameters were shown in Table 1. The physical shift was deducted. From Fig. 3 and Table 1, it could be seen that two kinds of coating were made of nickel and nickel oxide. The peaks of nickel appeared at the same binding energy, but the proportion of areas for Ni02p3/2 peak and Ni2O32p3/2 one for the pure nickel coating and composite one was different. According to the experimental results in Fig. 3 and data in Table 1, it could be concluded that the two kinds of coating were composed of the same components with different relative content [10,11]. If there were only mechanical but no chemical interaction between matrix nickel and nanoparticles, the proportion of nickel oxide to Ni0 in composite coating would be close to that in quick nickel coating. In fact, relative content of nickel oxide in the composite coating was much higher than that in quick nickel coating. The reason was that the unsaturated chemical bond of oxygen from nanoparticles surface could combine with nickel adatom and form Ni–O chemical bond. The nickel oxide in the composite coating consisted of surface oxide and interior oxide, later mainly derived from Ni–O chemical bond between matrix nickel and nanoparticles. In the interior of coating, there was little nickel oxide derived from oxidized growth surface of metal during plating process. Because the experimental conditions were same for the preparing process of pure nickel and composite coating, the relative content of oxide should be close to each other in two kinds of coating. So the oxide from the preparing process was not the key factor for bringing about the different proportion of peak area between nickel oxide and Ni0 in Fig. 3. In Fig. 3, the symmetry of nickel oxide peaks was poor and halfpeak width expanded, which was suggested that the nickel oxide was a mixture with oxides of many kinds but not only one. The spectrograms of silicon for the n-SiO2 powder and silicon dioxide in the composite coating were depicted in Fig. 4. The binding energy of Si2s in composite coating was lower 1.0 eV than that in the powder. This was a very important evidence for the chemical combination between nanoparticles and matrix nickel [5,8,9]. The results proved that there was chemical bond between n-SiO2 and nickel, and nanoparticles were inclined to acquire electron. In composite coating, the main component contained nickel, oxygen and silicon. The electronegativity of oxygen was higher than that of nickel and silicon. It was impossible that silicon captured Table 1 The electron binding energy from Fig. 3 Nickel
ENi02P3/2 (eV)
ENi02P1/2 (eV)
ENi2O32P3/2 (eV)
E2P3/2–2P1/2 (eV)
Nickel (standard)[15] Ni coating n-SiO2/Ni coating
852.30
869.70
855.60
17.40
852.05 852.20
869.3 869.40
855.40 855.60
17.25 17.20
Fig. 4. (a) XPS spectrograms of n-SiO2 powder. (b) XPS spectrograms of Si2s of n-SiO2/Ni composite coating.
directly electron from oxygen or nickel. The binding energy of Si2s seems not be decreased. The experimental result could be explained reasonably as follows: the unsaturated chemical bond of oxygen on nano-silicon dioxide surface could combine with nickel adatom and lead to the increasing of the electron cloud density outside of oxygen atom nucleus, and part of the electron cloud could be transferred to outside of silicon atom nucleus near this oxygen atom; therefore, the electron cloud density outside of silicon atom nucleus increased and binding energy decreased. During the electrodeposition process, Ni2+ and n-SiO2 particles in solution were carried to fluid boundary layer near electrode surface by hydromechanical effect from convection of solution. Then, Ni2+ and nSiO2 particles arrived at electrode surface by electric field and hydromechanical effect. Ni2+ was absorbed on the growth metal surface, acquired electrons and became adatom; and simultaneously some of n-SiO2 particles were captured by electrode surface. Some of captured nanoparticles combining weakly with electrode were carried away electrode surface by friction of brush pen and convection of solution, while the nanoparticles combining strongly with electrode surface were held on the growing surface of metal. The absorbed nickel atoms would diffuse on the electrode surface. Some of diffusing atoms could arrive at the interface between captured nanoparticles and growing metal surface, and combine with unsaturated chemical bond of oxygen atom on the surface of nanoparticles. As a result, Ni–O chemical bond was formed. These results had been proved that there were not only mechanical but also chemical interaction at the interface between n-SiO2 particles and matrix nickel in composite coating. Part sites of nanoparticles
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surface could combine with matrix metal by means of chemical bond. So the structure of composite coating was continuous. This was structure foundation on which composite coating had excellent performance.
4. Conclusions (1) Nanoparticles take part in electrode reaction and can catalyze the nickel electrodeposition evidently. (2) Nanoparticles combine with matrix nickel atoms by means of chemical bond at some sites of their interface in the composite coating. Acknowledgments The work was supported by National Natural Science Foundation of China (No. 50235030), 973 Project of National (No. G1999065009) and Cooperative Foundation of Science and Technology of Sino-Britain Government (No. 2002M3).
References [1] Derek Vanek, Metal Finishing 7 (2002) 18. [2] S.B. Hu, J.P. Tu, Z. Mei, Surface and Coatings Technology 141 (2001) 174. [3] Y.J. Ma, Z.X. Zhu, Surface Technology 30 (6) (2001) 5. [4] W.Y. Tu, B.S. Xu, B. Jiang, Chinese Journal of Materials Research 10 (5) (2003) 530. [5] W. Wang, H.T. Gau, J.P. Gao, Q.X. Qin, Chinese Journal of Materials Research 11 (2) (1997) 143. [6] M.Y. Abyaneh, M. Fleischmann, Journal of Electroanalytical Chemistry 119 (1981) 187. [7] M.Y. Abyaneh, M. Fleischmann, Journal of Electroanalytical Chemistry 119 (1981) 197. [8] B. Scharifker, G. Hills, Electrochimica Acta 28 (7) (1983) 879. [9] J. Amblard, M. Forment, G. Maurin, Elecrtochimica Acta 28 (7) (1983) 909. [10] A. Galtayries, J. Grimblot, Journal of Electron Spectroscopy and Related Phenomena 98–99 (1999) 267. [11] C.D. Wanger, W.M. Riggs, L.E. Davis, Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corporation Physical Electronic Division, Minnesota, 1979.
Electrocatalytic action of nano-SiO2 with electrodeposited nickel matrix Wei-Yi Tu ⁎, Bin-Shi Xu, Shi-Yun Dong, Hai-dou Wang State Key Laboratory of Remanufacture Technology, Armored Force Engineering Institute, Beijing 100072, China Received 1 July 2005; accepted 4 November 2005 Available online 28 November 2005
Abstract The present work focuses on the electrocatalytic effect of nano-SiO2 on nickel electrodeposition and chemical interaction between nano-SiO2 and nickel in composite coating. The electrochemical behavior from n-SiO2/Ni composite brush plating system and quick nickel solution are investigated using cyclic voltammetry. The interaction between n-SiO2 particles and matrix metal nickel is researched by X-ray photoelectron spectrometry. The results show that the n-SiO2 take part in the electrode reaction during nickel electrocrystallization and can catalyze the nickel electrodeposition. The unsaturated bond of oxygen on n-SiO2 particles surface can capture some of the absorbed nickel atoms and form nickel– oxygen chemical bond. It is proved that the chemical binding interaction exists in the interface between nanoparticles surface and matrix metal nickel. © 2005 Elsevier B.V. All rights reserved. Keywords: Nanocomposite; Catalysts; Chemical binding; Composite brush plating
1. Introduction A kind of nanoparticles composite coating superior to the ordinary one has been developed by means of electro-brush plating. The performance of composite coating has an advantage over that of ordinary one considerably. The nanoparticles lead to the evident difference between the formation of composite coating and that of ordinary plating coating, influences structure and properties of composite coating [1,2]. This shows that the electrodeposition process for nanoparticles composite electro-brush plating has its characteristics and principle. The current investigation work is mainly focused on preparing coating, testing performance and developing new brush plating solution [3,4]. Little research has been done on the mechanism of electrodeposition and the influence of nanoparticles over it, which restricts the development of nanoparticles composite electro-brush plating technology. So the relating theoretic research must be done to reveal the mechanism of nanoparticles composite electro-brush plating, which will be of great significance for the technical design and application. ⁎ Corresponding author. E-mail address: [email protected] (W.-Y. Tu). 0167-577X/$ - see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2005.11.008
In this paper, the special attention is paid to the role of nanoparticle during the electrodeposition process. Liner sweep voltammetry is used for determining the electrochemical response from n-SiO2/Ni composite brush plating solution and quick nickel solution. The X-ray photoelectron spectrometry (XPS) from pure nickel and composite coating is measured. The results show that the nanoparticles take part in electrode reaction and can catalyze the nickel electrodeposition evidently. Nanoparticles and nickel atoms in the composite coating combine by means of chemical bond and they are not mixed together mechanically only [5]. 2. Experimental The nickel micro-disk electrode sealed in a glass tube was used as the working electrode with 1 mm diameter, the platinum plate was used as the counter electrode with size of 8 mm × 15 mm, and the saturation calomel electrode (SCE) was selected as the reference electrode. Potential was measured and quoted with relative to SCE. Electrochemical measurement was performed with Potentiostat/Galvanostat Model 273A (EG&G Instrumental Inc.). The computer controlled electrochemical system was used in recording the transient response.
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Fig. 1. Cyclic voltammograms measured with quickly nickel brush plating solution (a) and n-SiO2/Ni composite solution (b), scan rate 50 mV/s, potential range 0.00 to − 1.10 V.
Before each measurement, the nickel micro-disk electrode was polished with metallurgical coated abrasive paper to obtain a mirror surface, then ultrasonicated and thoroughly rinsed with distilled water, acetone and distilled water successively, and at last transferred to the brush plating solution without being dried. The solution was bubbled with N2 for 10 min before each experiment in order to eliminate the dissolved oxygen. The working electrode was held at potential 0.0 mV for 2 min before each measurement to ensure reproducible initial steady state at its surface. All experimental were performed at the temperature of 20 °C. All electrochemical experiments were performed in quick nickel plating solution or composite solution. The solution contained 264 g·L− 1 NiSO4·6H2O, 56 g·L − 1 ammonium citrate, 23 g·L− 1 ammonium acetate, 105 g·L− 1 ammonia water and 20 g·L − 1 n-SiO2. The original diameter of nanoparticles was 10 nm for nano-SiO2 powder. The pH of plating solution was about 7.2. All the solution was prepared from analytical grade reagents and distilled water. All coatings were prepared by using electric brush plating technology. DSD-75-S direct current power was used (Armored Force Engineering Institute). The technology procedure for preparing quick nickel and composite coating was as follows: electro-cleaning, activating, basing, quick nickel brush plating
Fig. 2. Steady polarization curves measured with quickly nickel brush plating solution (a) and n-SiO2/Ni composite solution (b). The inset is the corresponding Tafel curve.
Fig. 3. XPS spectrograms of nickel: (a) Ni coating, (b) n-SiO2/Ni composite coating.
or composite brush plating. The coating thickness was about 100 μm, the content of n-SiO2 by weight was about 0.72% and its diameter distributed at the range of 30–50 nm in composite coating [4]. XPS measurement was preformed by using ESCA LAB220I-XL (VG SCIENTIFIC). The position sensitive detector (PSD) and aluminium anode target were used with photon energy 1486.6 eV. The pressure in the vacuum room was kept at 2.9 × 10− 7 Pa. The C1s with energy 284.6 eV was used to calibrate spectral series displacement. Before experimental, the coating surface was mechanically polished to remove surface oxide and the fresh surface was exposed, then the sample was placed into the vacuum room immediately to measure. 3. Results and discussion 3.1. Catalytic effect of n-SiO2 on nickel electrodeposition The typical cyclic voltammograms were shown in Fig. 1; the steady-state polarization curves were depicted in Fig. 2. In Fig. 1, it was clear that the general shapes of the curves were similar, except for the overpotential and current efficiency. There was a little current response at the potential range of 0.0 V to −0.5 V. The current increased slowly below −0.85 V or − 0.87 V, then increased quickly for composite solution and quick nickel solution, respectively. In reverse scan process, the dissolution peak of nickel was at − 0.36 V in quick nickel solution and shifted slightly positively for composite solution. The current loops were found in Fig. 1, which indicated that the electrochemical nucleus process was underwent during nickel electrodeposition [6–9]. In Fig. 2, it was depicted distinctly that the overpotential of composite system was lower than that of quick nickel solution at the same currents, while the current was higher at the same potentials These facts showed that n-SiO2 took part in electrode reaction and could catalyze electrodeposition of nickel evidently. The main processes of metal electrodeposition included reactant transfer in liquid, interface reaction and electrocrystallization. The nSiO2 had no electrochemical activity itself and no electron exchange would happen between nanoparticle and electrode. Therefore, nanoparticles had no effect on the electron exchange reaction and their effect should be at the subsequent crystallization process.
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3.2. Combination between nano-SiO2 and matrix nickel in composite coating In general, it is considered that the second phase particle mixes with matrix phase only mechanically in composite coating [5]. In order to understand whether nano-SiO2 and nickel were combined in the composite coating chemically or mechanically, X-ray photoelectron spectrometry was used for analyzing the energy state of elements in coating [5]. The spectrograms of nickel element were depicted in Fig. 3 and the relative parameters were shown in Table 1. The physical shift was deducted. From Fig. 3 and Table 1, it could be seen that two kinds of coating were made of nickel and nickel oxide. The peaks of nickel appeared at the same binding energy, but the proportion of areas for Ni02p3/2 peak and Ni2O32p3/2 one for the pure nickel coating and composite one was different. According to the experimental results in Fig. 3 and data in Table 1, it could be concluded that the two kinds of coating were composed of the same components with different relative content [10,11]. If there were only mechanical but no chemical interaction between matrix nickel and nanoparticles, the proportion of nickel oxide to Ni0 in composite coating would be close to that in quick nickel coating. In fact, relative content of nickel oxide in the composite coating was much higher than that in quick nickel coating. The reason was that the unsaturated chemical bond of oxygen from nanoparticles surface could combine with nickel adatom and form Ni–O chemical bond. The nickel oxide in the composite coating consisted of surface oxide and interior oxide, later mainly derived from Ni–O chemical bond between matrix nickel and nanoparticles. In the interior of coating, there was little nickel oxide derived from oxidized growth surface of metal during plating process. Because the experimental conditions were same for the preparing process of pure nickel and composite coating, the relative content of oxide should be close to each other in two kinds of coating. So the oxide from the preparing process was not the key factor for bringing about the different proportion of peak area between nickel oxide and Ni0 in Fig. 3. In Fig. 3, the symmetry of nickel oxide peaks was poor and halfpeak width expanded, which was suggested that the nickel oxide was a mixture with oxides of many kinds but not only one. The spectrograms of silicon for the n-SiO2 powder and silicon dioxide in the composite coating were depicted in Fig. 4. The binding energy of Si2s in composite coating was lower 1.0 eV than that in the powder. This was a very important evidence for the chemical combination between nanoparticles and matrix nickel [5,8,9]. The results proved that there was chemical bond between n-SiO2 and nickel, and nanoparticles were inclined to acquire electron. In composite coating, the main component contained nickel, oxygen and silicon. The electronegativity of oxygen was higher than that of nickel and silicon. It was impossible that silicon captured Table 1 The electron binding energy from Fig. 3 Nickel
ENi02P3/2 (eV)
ENi02P1/2 (eV)
ENi2O32P3/2 (eV)
E2P3/2–2P1/2 (eV)
Nickel (standard)[15] Ni coating n-SiO2/Ni coating
852.30
869.70
855.60
17.40
852.05 852.20
869.3 869.40
855.40 855.60
17.25 17.20
Fig. 4. (a) XPS spectrograms of n-SiO2 powder. (b) XPS spectrograms of Si2s of n-SiO2/Ni composite coating.
directly electron from oxygen or nickel. The binding energy of Si2s seems not be decreased. The experimental result could be explained reasonably as follows: the unsaturated chemical bond of oxygen on nano-silicon dioxide surface could combine with nickel adatom and lead to the increasing of the electron cloud density outside of oxygen atom nucleus, and part of the electron cloud could be transferred to outside of silicon atom nucleus near this oxygen atom; therefore, the electron cloud density outside of silicon atom nucleus increased and binding energy decreased. During the electrodeposition process, Ni2+ and n-SiO2 particles in solution were carried to fluid boundary layer near electrode surface by hydromechanical effect from convection of solution. Then, Ni2+ and nSiO2 particles arrived at electrode surface by electric field and hydromechanical effect. Ni2+ was absorbed on the growth metal surface, acquired electrons and became adatom; and simultaneously some of n-SiO2 particles were captured by electrode surface. Some of captured nanoparticles combining weakly with electrode were carried away electrode surface by friction of brush pen and convection of solution, while the nanoparticles combining strongly with electrode surface were held on the growing surface of metal. The absorbed nickel atoms would diffuse on the electrode surface. Some of diffusing atoms could arrive at the interface between captured nanoparticles and growing metal surface, and combine with unsaturated chemical bond of oxygen atom on the surface of nanoparticles. As a result, Ni–O chemical bond was formed. These results had been proved that there were not only mechanical but also chemical interaction at the interface between n-SiO2 particles and matrix nickel in composite coating. Part sites of nanoparticles
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surface could combine with matrix metal by means of chemical bond. So the structure of composite coating was continuous. This was structure foundation on which composite coating had excellent performance.
4. Conclusions (1) Nanoparticles take part in electrode reaction and can catalyze the nickel electrodeposition evidently. (2) Nanoparticles combine with matrix nickel atoms by means of chemical bond at some sites of their interface in the composite coating. Acknowledgments The work was supported by National Natural Science Foundation of China (No. 50235030), 973 Project of National (No. G1999065009) and Cooperative Foundation of Science and Technology of Sino-Britain Government (No. 2002M3).
References [1] Derek Vanek, Metal Finishing 7 (2002) 18. [2] S.B. Hu, J.P. Tu, Z. Mei, Surface and Coatings Technology 141 (2001) 174. [3] Y.J. Ma, Z.X. Zhu, Surface Technology 30 (6) (2001) 5. [4] W.Y. Tu, B.S. Xu, B. Jiang, Chinese Journal of Materials Research 10 (5) (2003) 530. [5] W. Wang, H.T. Gau, J.P. Gao, Q.X. Qin, Chinese Journal of Materials Research 11 (2) (1997) 143. [6] M.Y. Abyaneh, M. Fleischmann, Journal of Electroanalytical Chemistry 119 (1981) 187. [7] M.Y. Abyaneh, M. Fleischmann, Journal of Electroanalytical Chemistry 119 (1981) 197. [8] B. Scharifker, G. Hills, Electrochimica Acta 28 (7) (1983) 879. [9] J. Amblard, M. Forment, G. Maurin, Elecrtochimica Acta 28 (7) (1983) 909. [10] A. Galtayries, J. Grimblot, Journal of Electron Spectroscopy and Related Phenomena 98–99 (1999) 267. [11] C.D. Wanger, W.M. Riggs, L.E. Davis, Handbook of X-ray Photoelectron Spectroscopy, Perkin-Elmer Corporation Physical Electronic Division, Minnesota, 1979.