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Nanocomposite Ni–TiN coatings prepared by ultrasonic electrodeposition
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Current Applied Physics 9 (2009) 44–47 www.elsevier.com/locate/cap www.kps.or.kr
Nanocomposite Ni–TiN coatings prepared by ultrasonic electrodeposition Fa-feng Xia a, Meng-hua Wu b,*, Fan Wang c, Zhen-yuan Jia a, Ai-leng Wang c a
School of Mechanical Engineering, Dalian University of Technology, Dalian 116023, China b School of Mechanical Engineering, Dalian University, Dalian 116622, China c School of Environment and Chemical Engineering, Dalian University, Dalian 116622, China Received 29 October 2007; received in revised form 21 November 2007; accepted 22 November 2007 Available online 8 December 2007
Abstract Nanocomposite Ni–TiN coatings were prepared by ultrasonic electrodeposition and the effects of ultrasonication on the coatings were studied. X-ray diffraction analysis was utilized to detect the crystalline and amorphous characteristics of the composite coatings. The surface morphology and metallurgical structure were observed by scanning electron microscopy, high-resolution transmission electron microscopy and scanning probe microscopy. The results showed that ultrasonication had great effects on TiN nanoparticles in composite coatings. The moderate ultrasonication conduced to homogeneous dispersion of TiN particles in the coatings. Moreover, the TiN nanoparticles that entered and homogeneously dispersed in the composite coating led to an increase in the number of nuclei for nucleation of nickel grains and inhibition of grain growth. Therefore, the introduction of ultrasonication and TiN nanoparticles resulted in the formation of smaller nickel grains. The average grain diameter of TiN particles was 33 nm, while Ni grains measured approximately 53 nm. Ó 2007 Elsevier B.V. All rights reserved. PACS: 78.67.Ch Keywords: Nanocomposite; Ni–TiN; Ultrasonic electrodeposition; Microstructure
1. Introduction Composite electrodeposition technology is a method to obtain composite coatings by adding insoluble micrometeror nanometer-sized solid particles (such as TiN, AlN, SiC, and Al2O3) to the electrolyte to co-deposit the particles and metal matrix with electrodeposition [1–4]. In recent years, there has been a rapid increase in interest in metal–ceramic nanocomposite coatings owing to favorable properties such as specific heat, optical non-linearity and magnetism and mechanical performance such as high hardness, wear resistance and corrosion resistance [5–9]. Owing to the superiority of both traditional composite materials and modern nanomaterials, nanocomposite coatings have become the focus of widespread research [10–14]. *
Corresponding author. Tel.: +86 411 81950418. E-mail address: xiaff[email protected] (M.-h. Wu).
1567-1739/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2007.11.014
Mechanical dispersion is typically used to prepare composite coatings. This method involves agitation to suspend particles in the electrolyte and is less effective once all the particles are in suspension compared to the effect of ultrasonication on the dispersion of tiny particles in the electrolyte. In the present study, Ni–TiN nanocomposite coatings were synthesized by ultrasonic electrodeposition. Compared to conventional methods, this method is more effective and simple. 2. Experimental Nano Ni–TiN composite coatings were deposited on 45 steel substrates by ultrasonic electrodeposition. The anode was a pure Ni plate. The average grain diameter of the TiN nanoparticles (purity >99.9%) was 20 nm. The composition of the electrolyte was as follows: 250 g/l nickel sulfate, 40 g/l nickel chloride, 30 g/l boric acid and 2–10 g/l TiN
F.-f. Xia et al. / Current Applied Physics 9 (2009) 44–47
particles. The temperature of the plating bath was kept at 50 °C at pH 4–5, adjusted using ammonium hydroxide or dilute sulfuric acid. The current density was 2–5 A/dm2. Prior to deposition, the steel substrates were mechanically polished to a 0.10–0.15 lm surface finish and then cleaned to remove contamination on the substrate surface. The substrates were activated for 15 s in a mixed acidic bath after rinsing with distilled water. The Ni–TiN composite coatings were electrodeposited by gradually increasing the ultrasonic power from 0 to 300 W. To determine the crystal properties of Ni–TiN composite coatings, X-ray diffraction (XRD) analysis was performed on a Rigaku D/Max-2400 instrument using Cu Ka radiation (k = 0.15418 nm). The operating target voltage was 40 kV and the tube current was 100 mA. The microstructure of deposit cross-sections was investigated using scanning electron microscopy (SEM, JSM6460LV). The surface morphology and microstructure of composite coatings were observed by SEM, high-resolution transmission electron microscopy (HRTEM; Tecnai-G220-S-Twin) and scanning probe microscopy (SPM, Nanoscope IIIa). 3. Results and analysis 3.1. Effects of ultrasonication on TiN nanoparticles in composite coatings The effects of ultrasonication on the distribution of TiN nanoparticles in composite coatings are depicted in
45
Fig. 1 for current density of 4 A/dm2 and TiN content of 6 g/l at pH 4.5. Fig. 1a shows that TiN particles in a composite coating electrodeposited by mechanical dispersion are few in quantity and appear to aggregate to some extent. TiN particles in the composite coating prepared by electrodeposition with appropriate ultrasonic parameters (200 W) are much greater in number and are dispersed homogeneously in the deposit (Fig. 1b). And the Ni–TiN composite coating exhibits a dense structure. When the ultrasonic power was further increased, TiN particles in the composite coating were small in number and exhibited slight aggregation (Fig. 1c). The reason for this behavior is that mechanical dispersion involves agitation to suspend particles in the electrolyte, and is less effective once the particles are in suspension; in comparison, the effect of ultrasonication on the dispersion of tiny particles in the electrolyte is more efficient. Acoustic streams produced by ultrasonic power lead to homogeneous dispersion of TiN particles in the electrolyte. Furthermore, high-pressure waves and violent vibrations generated by ultrasonication shatter groups of aggregated particles, leading to further homogenization on a microscopic level. According to Guglielmi’s adsorption model of composite electrodeposition, the process may be divided into weak and strong adsorption of particles on the electrode surface, in which the weak adsorption process is reversible. When high ultrasonic power is applied, the greater cavitation effects will lead to violent collision and aggregation of TiN nanoparticles, while the greater stirring effect will
Fig. 1. Distribution of TiN nanoparticles in composite coatings prepared under different conditions: (a) mechanical dispersion; (b) moderate ultrasonication (200 W); and (c) strong ultrasonication (300 W).
46
F.-f. Xia et al. / Current Applied Physics 9 (2009) 44–47
dislodge nanoparticles that are not firmly adsorbed on the cathode surface, affecting oriented deposition of the particles and thus decreasing the TiN nanoparticle content in the composite coating. 3.2. Effects of ultrasonication on XRD patterns of composite coatings XRD patterns of Ni–TiN nanocomposite coatings prepared by electrodeposition with and without ultrasonication are displayed in Fig. 2. It can be seen that the diffraction peaks of nickel crystals appeared at 0 W. With the increase of ultrasonic power, the diffraction peaks became more distensible and wider, suggesting a decrease in the mean size of the nickel crystals. The intensity of the Ni peaks showed a tendency to decrease as the ultrasonic power increased from 0 to 200 W, in agreement with a previous study by Wu et al. [15]. When the ultrasonic power was 300 W, the diffraction peaks of the nickel crystals had a little change. During ultrasonic electrodeposition, the nickel crystals are fine and growth changes to a random direction. The reason for this is that nanoparticles that enter and homogeneously disperse in the composite coating lead to an increase in the number of nuclei for nucleation of nickel grains and inhibition of grain growth. Furthermore, the mechanical force produced by acoustic streams during ultrasonication may break the normal growth of grains and disrupt larger grains to produce smaller nuclei. Thus, the critical radius of the nuclei is decreased and nucleation is promoted. This increase in nucleation and decrease in growth lead to smaller nickel grains. When the high ultrasonic power (300 W) is applied, the ultrasonication can break the normal growth of nickel crystals and disrupt larger crystals to produce smaller nuclei. But on the other hand, the high ultrasonic power affects the oriented deposition and content of TiN nanoparticles in the coatings, leading to a decrease in the number of nuclei for nucleation
of nickel crystals. Therefore, the diffraction peaks of the nickel crystals change slightly. 3.3. Analysis of the microstructure Fig. 3 is the XRD pattern of a Ni–TiN nanocomposite coating in cross-section. The XRD patterns showed that it consisted of Ni phase and TiN phase. This is also evidences a two-phase nanocomposite. For Ni, the diffraction peaks at 44.82°, 52.21° and 76.77° correspond to (1 1 1), (2 0 0) and (2 2 0). For TiN, the diffraction peaks at 36.66°, 42.60° and 61.81° correspond to (1 1 1), (2 0 0) and (2 2 0). Using the Scherrer equation, the average grain diameter can be calculated as follows: L¼
Kk ; b cos h
ð1Þ
where K is the figure factor of the grain (K = 0.89), k is the wavelength, b is the width at half height of the diffraction peak and h is the Bragg angle.
Fig. 3. XRD pattern of a nano Ni–TiN composite coating in crosssection.
Fig. 2. XRD patterns of nano Ni–TiN composite coatings.
Fig. 4. HRTEM image of a nano Ni–TiN composite coating.
F.-f. Xia et al. / Current Applied Physics 9 (2009) 44–47
47
Fig. 5. SPM images of nano Ni–TiN composite coatings.
The average diameter of Ni grains calculated from the XRD peak intensities using Eq. (1) was approximately 52.85 nm. Ni–TiN composite coatings were peeled from the matrix, polished on 2000-grit abrasive paper, and then reduced on a Gatan-600 double-ion reducing instrument to thin films. The microstructure observed by HRTEM is shown in Fig. 4. The black sections in Fig. 4 are TiN nanoparticles, and the average diameter is approximately 30 nm. It is also evident that the Ni grains are of nanometer size, measured as approximately 55 nm. To determine the microstructure of the coatings and the size of the grains, the coating surfaces were observed by SPM. Two- and three-dimensional coating images are shown in Fig. 5. It is evident that the coating contained TiN nanoparticles of approximately 35 nm in diameter, larger than the size calculated from HRTEM analysis. The average diameter of Ni grains is approximately 50 nm. Taking all the calculations into consideration, the average diameter of TiN particles was approximately 33 nm and the average diameter of Ni grains was approximately 53 nm. 4. Conclusions Ultrasonication had great effects on TiN nanoparticles in composite coatings. SEM analysis showed that Ni–TiN composite coatings exhibited a dense structure. And the TiN particles were homogeneously dispersed in composite coatings prepared using appropriate parameters (current density, 4 A/dm2; TiN particles, 6 g/l; ultrasonic power, 200 W; pH 4.5). XRD analysis of the coatings showed that ultrasonication and TiN nanoparticles led to smaller nickel grains. And XRD, HRTEM and SPM analyses revealed the presence of TiN nanoparticles in the composite
coatings. According to calculations, the average particle diameter was approximately 33 nm. Ni grains were also nano-sized, measured as approximately 53 nm. Acknowledgements This work was supported by the National Natural Science Foundation of China under Grant No. 50475108 and the Natural Science Foundation of Liaoning province under Grant No. 20042123. References [1] N.Q. Minh, J. Am. Ceram. Soc. 76 (1993) 563–588. [2] P.H. Chong, H.C. Man, Surf. Coat. Technol. 145 (2001) 51–59. [3] J.K.N. Murthy, D.S. Rao, B. Venkataraman, Wear 249 (2001) 592–600. [4] J.W. Moon, H.L. Lee, J.D. Kim, G.D. Kim, D.A. Lee, Mater. Lett. 38 (1999) 214–220. [5] Y. Li, Z.L. Tang, Y.S. Xie, Z.T. Zhang, Mater. Sci. Technol. 9 (2001) 91–94. [6] J. Przybylowicz, J. Kusinski, J. Mater. Process. Technol. 109 (2001) 154–160. [7] T. Fukui, S. Ohara, M. Naito, K. Nogi, J. Eur. Ceram. Soc. 23 (2003) 2963–29677. [8] Y.X. Chen, W.M. Liu, C.F. Ye, S.K. Qi, Mater. Res. Bull. 36 (2001) 2605–2612. [9] J. Li, X.D. Bai, D.L. Zhang, Appl. Surf. Sci. 252 (2006) 7436–7441. [10] I. Garcia, J. Fransaer, J.P. Celis, Surf. Coat. Technol. 148 (2001) 171– 176. [11] P. Wu, H.M. Du, X.L. Chen, Z.Q. Li, H.L. Bai, E.Y. Jiang, Wear 257 (2004) 142–147. [12] C.X. Li, Z.G. Wang, Chem. J. 5 (2001) 268–274. [13] B. Subramanian, S. Mohan, Sobha Jayakrishnan, M. Jayachandran, Curr. Appl. Phys. 7 (2007) 305–313. [14] Q. Li, G.M. Song, Y.Z. Zhang, T.C. Lei, W.Z. Chen, Wear 254 (2003) 222–229. [15] M.H. Wu, Z. Li, F.F. Xia, X.X. Fu, J. Funct. Mater. 35 (2004) 776– 778, in Chinese.
Current Applied Physics 9 (2009) 44–47 www.elsevier.com/locate/cap www.kps.or.kr
Nanocomposite Ni–TiN coatings prepared by ultrasonic electrodeposition Fa-feng Xia a, Meng-hua Wu b,*, Fan Wang c, Zhen-yuan Jia a, Ai-leng Wang c a
School of Mechanical Engineering, Dalian University of Technology, Dalian 116023, China b School of Mechanical Engineering, Dalian University, Dalian 116622, China c School of Environment and Chemical Engineering, Dalian University, Dalian 116622, China Received 29 October 2007; received in revised form 21 November 2007; accepted 22 November 2007 Available online 8 December 2007
Abstract Nanocomposite Ni–TiN coatings were prepared by ultrasonic electrodeposition and the effects of ultrasonication on the coatings were studied. X-ray diffraction analysis was utilized to detect the crystalline and amorphous characteristics of the composite coatings. The surface morphology and metallurgical structure were observed by scanning electron microscopy, high-resolution transmission electron microscopy and scanning probe microscopy. The results showed that ultrasonication had great effects on TiN nanoparticles in composite coatings. The moderate ultrasonication conduced to homogeneous dispersion of TiN particles in the coatings. Moreover, the TiN nanoparticles that entered and homogeneously dispersed in the composite coating led to an increase in the number of nuclei for nucleation of nickel grains and inhibition of grain growth. Therefore, the introduction of ultrasonication and TiN nanoparticles resulted in the formation of smaller nickel grains. The average grain diameter of TiN particles was 33 nm, while Ni grains measured approximately 53 nm. Ó 2007 Elsevier B.V. All rights reserved. PACS: 78.67.Ch Keywords: Nanocomposite; Ni–TiN; Ultrasonic electrodeposition; Microstructure
1. Introduction Composite electrodeposition technology is a method to obtain composite coatings by adding insoluble micrometeror nanometer-sized solid particles (such as TiN, AlN, SiC, and Al2O3) to the electrolyte to co-deposit the particles and metal matrix with electrodeposition [1–4]. In recent years, there has been a rapid increase in interest in metal–ceramic nanocomposite coatings owing to favorable properties such as specific heat, optical non-linearity and magnetism and mechanical performance such as high hardness, wear resistance and corrosion resistance [5–9]. Owing to the superiority of both traditional composite materials and modern nanomaterials, nanocomposite coatings have become the focus of widespread research [10–14]. *
Corresponding author. Tel.: +86 411 81950418. E-mail address: xiaff[email protected] (M.-h. Wu).
1567-1739/$ - see front matter Ó 2007 Elsevier B.V. All rights reserved. doi:10.1016/j.cap.2007.11.014
Mechanical dispersion is typically used to prepare composite coatings. This method involves agitation to suspend particles in the electrolyte and is less effective once all the particles are in suspension compared to the effect of ultrasonication on the dispersion of tiny particles in the electrolyte. In the present study, Ni–TiN nanocomposite coatings were synthesized by ultrasonic electrodeposition. Compared to conventional methods, this method is more effective and simple. 2. Experimental Nano Ni–TiN composite coatings were deposited on 45 steel substrates by ultrasonic electrodeposition. The anode was a pure Ni plate. The average grain diameter of the TiN nanoparticles (purity >99.9%) was 20 nm. The composition of the electrolyte was as follows: 250 g/l nickel sulfate, 40 g/l nickel chloride, 30 g/l boric acid and 2–10 g/l TiN
F.-f. Xia et al. / Current Applied Physics 9 (2009) 44–47
particles. The temperature of the plating bath was kept at 50 °C at pH 4–5, adjusted using ammonium hydroxide or dilute sulfuric acid. The current density was 2–5 A/dm2. Prior to deposition, the steel substrates were mechanically polished to a 0.10–0.15 lm surface finish and then cleaned to remove contamination on the substrate surface. The substrates were activated for 15 s in a mixed acidic bath after rinsing with distilled water. The Ni–TiN composite coatings were electrodeposited by gradually increasing the ultrasonic power from 0 to 300 W. To determine the crystal properties of Ni–TiN composite coatings, X-ray diffraction (XRD) analysis was performed on a Rigaku D/Max-2400 instrument using Cu Ka radiation (k = 0.15418 nm). The operating target voltage was 40 kV and the tube current was 100 mA. The microstructure of deposit cross-sections was investigated using scanning electron microscopy (SEM, JSM6460LV). The surface morphology and microstructure of composite coatings were observed by SEM, high-resolution transmission electron microscopy (HRTEM; Tecnai-G220-S-Twin) and scanning probe microscopy (SPM, Nanoscope IIIa). 3. Results and analysis 3.1. Effects of ultrasonication on TiN nanoparticles in composite coatings The effects of ultrasonication on the distribution of TiN nanoparticles in composite coatings are depicted in
45
Fig. 1 for current density of 4 A/dm2 and TiN content of 6 g/l at pH 4.5. Fig. 1a shows that TiN particles in a composite coating electrodeposited by mechanical dispersion are few in quantity and appear to aggregate to some extent. TiN particles in the composite coating prepared by electrodeposition with appropriate ultrasonic parameters (200 W) are much greater in number and are dispersed homogeneously in the deposit (Fig. 1b). And the Ni–TiN composite coating exhibits a dense structure. When the ultrasonic power was further increased, TiN particles in the composite coating were small in number and exhibited slight aggregation (Fig. 1c). The reason for this behavior is that mechanical dispersion involves agitation to suspend particles in the electrolyte, and is less effective once the particles are in suspension; in comparison, the effect of ultrasonication on the dispersion of tiny particles in the electrolyte is more efficient. Acoustic streams produced by ultrasonic power lead to homogeneous dispersion of TiN particles in the electrolyte. Furthermore, high-pressure waves and violent vibrations generated by ultrasonication shatter groups of aggregated particles, leading to further homogenization on a microscopic level. According to Guglielmi’s adsorption model of composite electrodeposition, the process may be divided into weak and strong adsorption of particles on the electrode surface, in which the weak adsorption process is reversible. When high ultrasonic power is applied, the greater cavitation effects will lead to violent collision and aggregation of TiN nanoparticles, while the greater stirring effect will
Fig. 1. Distribution of TiN nanoparticles in composite coatings prepared under different conditions: (a) mechanical dispersion; (b) moderate ultrasonication (200 W); and (c) strong ultrasonication (300 W).
46
F.-f. Xia et al. / Current Applied Physics 9 (2009) 44–47
dislodge nanoparticles that are not firmly adsorbed on the cathode surface, affecting oriented deposition of the particles and thus decreasing the TiN nanoparticle content in the composite coating. 3.2. Effects of ultrasonication on XRD patterns of composite coatings XRD patterns of Ni–TiN nanocomposite coatings prepared by electrodeposition with and without ultrasonication are displayed in Fig. 2. It can be seen that the diffraction peaks of nickel crystals appeared at 0 W. With the increase of ultrasonic power, the diffraction peaks became more distensible and wider, suggesting a decrease in the mean size of the nickel crystals. The intensity of the Ni peaks showed a tendency to decrease as the ultrasonic power increased from 0 to 200 W, in agreement with a previous study by Wu et al. [15]. When the ultrasonic power was 300 W, the diffraction peaks of the nickel crystals had a little change. During ultrasonic electrodeposition, the nickel crystals are fine and growth changes to a random direction. The reason for this is that nanoparticles that enter and homogeneously disperse in the composite coating lead to an increase in the number of nuclei for nucleation of nickel grains and inhibition of grain growth. Furthermore, the mechanical force produced by acoustic streams during ultrasonication may break the normal growth of grains and disrupt larger grains to produce smaller nuclei. Thus, the critical radius of the nuclei is decreased and nucleation is promoted. This increase in nucleation and decrease in growth lead to smaller nickel grains. When the high ultrasonic power (300 W) is applied, the ultrasonication can break the normal growth of nickel crystals and disrupt larger crystals to produce smaller nuclei. But on the other hand, the high ultrasonic power affects the oriented deposition and content of TiN nanoparticles in the coatings, leading to a decrease in the number of nuclei for nucleation
of nickel crystals. Therefore, the diffraction peaks of the nickel crystals change slightly. 3.3. Analysis of the microstructure Fig. 3 is the XRD pattern of a Ni–TiN nanocomposite coating in cross-section. The XRD patterns showed that it consisted of Ni phase and TiN phase. This is also evidences a two-phase nanocomposite. For Ni, the diffraction peaks at 44.82°, 52.21° and 76.77° correspond to (1 1 1), (2 0 0) and (2 2 0). For TiN, the diffraction peaks at 36.66°, 42.60° and 61.81° correspond to (1 1 1), (2 0 0) and (2 2 0). Using the Scherrer equation, the average grain diameter can be calculated as follows: L¼
Kk ; b cos h
ð1Þ
where K is the figure factor of the grain (K = 0.89), k is the wavelength, b is the width at half height of the diffraction peak and h is the Bragg angle.
Fig. 3. XRD pattern of a nano Ni–TiN composite coating in crosssection.
Fig. 2. XRD patterns of nano Ni–TiN composite coatings.
Fig. 4. HRTEM image of a nano Ni–TiN composite coating.
F.-f. Xia et al. / Current Applied Physics 9 (2009) 44–47
47
Fig. 5. SPM images of nano Ni–TiN composite coatings.
The average diameter of Ni grains calculated from the XRD peak intensities using Eq. (1) was approximately 52.85 nm. Ni–TiN composite coatings were peeled from the matrix, polished on 2000-grit abrasive paper, and then reduced on a Gatan-600 double-ion reducing instrument to thin films. The microstructure observed by HRTEM is shown in Fig. 4. The black sections in Fig. 4 are TiN nanoparticles, and the average diameter is approximately 30 nm. It is also evident that the Ni grains are of nanometer size, measured as approximately 55 nm. To determine the microstructure of the coatings and the size of the grains, the coating surfaces were observed by SPM. Two- and three-dimensional coating images are shown in Fig. 5. It is evident that the coating contained TiN nanoparticles of approximately 35 nm in diameter, larger than the size calculated from HRTEM analysis. The average diameter of Ni grains is approximately 50 nm. Taking all the calculations into consideration, the average diameter of TiN particles was approximately 33 nm and the average diameter of Ni grains was approximately 53 nm. 4. Conclusions Ultrasonication had great effects on TiN nanoparticles in composite coatings. SEM analysis showed that Ni–TiN composite coatings exhibited a dense structure. And the TiN particles were homogeneously dispersed in composite coatings prepared using appropriate parameters (current density, 4 A/dm2; TiN particles, 6 g/l; ultrasonic power, 200 W; pH 4.5). XRD analysis of the coatings showed that ultrasonication and TiN nanoparticles led to smaller nickel grains. And XRD, HRTEM and SPM analyses revealed the presence of TiN nanoparticles in the composite
coatings. According to calculations, the average particle diameter was approximately 33 nm. Ni grains were also nano-sized, measured as approximately 53 nm. Acknowledgements This work was supported by the National Natural Science Foundation of China under Grant No. 50475108 and the Natural Science Foundation of Liaoning province under Grant No. 20042123. References [1] N.Q. Minh, J. Am. Ceram. Soc. 76 (1993) 563–588. [2] P.H. Chong, H.C. Man, Surf. Coat. Technol. 145 (2001) 51–59. [3] J.K.N. Murthy, D.S. Rao, B. Venkataraman, Wear 249 (2001) 592–600. [4] J.W. Moon, H.L. Lee, J.D. Kim, G.D. Kim, D.A. Lee, Mater. Lett. 38 (1999) 214–220. [5] Y. Li, Z.L. Tang, Y.S. Xie, Z.T. Zhang, Mater. Sci. Technol. 9 (2001) 91–94. [6] J. Przybylowicz, J. Kusinski, J. Mater. Process. Technol. 109 (2001) 154–160. [7] T. Fukui, S. Ohara, M. Naito, K. Nogi, J. Eur. Ceram. Soc. 23 (2003) 2963–29677. [8] Y.X. Chen, W.M. Liu, C.F. Ye, S.K. Qi, Mater. Res. Bull. 36 (2001) 2605–2612. [9] J. Li, X.D. Bai, D.L. Zhang, Appl. Surf. Sci. 252 (2006) 7436–7441. [10] I. Garcia, J. Fransaer, J.P. Celis, Surf. Coat. Technol. 148 (2001) 171– 176. [11] P. Wu, H.M. Du, X.L. Chen, Z.Q. Li, H.L. Bai, E.Y. Jiang, Wear 257 (2004) 142–147. [12] C.X. Li, Z.G. Wang, Chem. J. 5 (2001) 268–274. [13] B. Subramanian, S. Mohan, Sobha Jayakrishnan, M. Jayachandran, Curr. Appl. Phys. 7 (2007) 305–313. [14] Q. Li, G.M. Song, Y.Z. Zhang, T.C. Lei, W.Z. Chen, Wear 254 (2003) 222–229. [15] M.H. Wu, Z. Li, F.F. Xia, X.X. Fu, J. Funct. Mater. 35 (2004) 776– 778, in Chinese.