- Email: [email protected]
Synthesis of Ni–Co–ZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating
Journal of Alloys and Compounds xxx (xxxx) xxx
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating Baosong Li a, Weiwei Zhang b, * a b
College of Mechanics and Materials, Hohai University, Nanjing, 211100, China College of Mechanical and Electrical Engineering, Hohai University, Changzhou, 213022, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 September 2019 Received in revised form 20 November 2019 Accepted 22 November 2019 Available online xxx
A novel NieCoeZrO2 nanocomposites doped with ceria particles has been synthesized by pulse electrodeposition as highly protective coating. The effect of current density and duty cycle on its structure and properties were evaluated. The composite coatings are compact with hill-valley like structure. The average roughness (Sa) was about 73e98 nm and the duty cycle of 70% benefits low roughness and finegrained structure. The crystallite size of these coatings is 17e20 nm. The nanocrystalline coating exhibits the preferred orientation of Ni (111) texture. AFM and XPS were utilized to analyze the surface properties. EIS results indicated that the electrodeposition parameters greatly affect the corrosion behavior of the nanocomposites. The electrochemical behavior varied with immersing time. Duty cycle of 30%, current density of 2 A dm2 were the appropriate parameters for the best corrosion and wear resistance and optimal long-term electrochemical stability in 3.5 wt% NaCl corrosive solution. This coating shows good potential for engineering application in aggressive medium. © 2019 Elsevier B.V. All rights reserved.
Keywords: Nanocomposite coating NieCoeZrO2eCeO2 Pulse electrodeposition Corrosion behavior Electrochemical impedance spectroscopy
1. Introduction The performance stability of a material is significant for the applications in corrosive medium, which usually requires high corrosion and wear resistance [1,2]. Electrodeposition exhibits the merits of simple, flexible, inexpensive, controllable and efficient, and was extensively applied in many fields as surface protective coating [3,4]. Nickel or its alloy is an important protective coating and could protect metallic substrate from corrosion and wear when it deposited on its surface [5]. Due to their unique advantages in strength [6], corrosion resistance [7], wear-resistant [8], electrocatalytic [9] and magnetic properties [10], NieCo alloy has attracted extensive attention in application fields of magnetic storage, automobile, electrical and aerospace. However, further improvement in corrosion resistance and anti-wear properties is continuously desired to maintain its service life or broaden its applications in aggressive medium, such as marine engineering, mining, petroleum, and chemical industry. In recent years, many researchers focus on NieCo composite coating reinforced by nanoparticles to enhance its performance to
* Corresponding author. E-mail address: [email protected] (W. Zhang).
meet the special requirements for practical application [11]. The preparation of NieCo composite coating by electrodeposition has been studied by some researchers to enhance their mechanical, anti-corrosion, and thermal stability properties [12,13]. The ceramic particles such as SiC [14,15], TiN [16], Al2O3 [17], TiO2 [18], Cr2O3 [11] and WC [19] has been selected as reinforcing second phase in NieCo matrix. Bakhit [20] reported that the hardness and corrosion resistance of NieCo/SiC coating was significantly affected by the incorporated particles. An [21,22] investigated NieCo/Al2O3 composites and reported that Al2O3 content enhanced the hardness and wear resistance. Elkhoshkhany [7] prepared Ni-Co-WC composite coating and proved the increase in hardness. Hefnawy [16] revealed that corrosion-resistant properties and hardness of NieCoeTiN were substantially strengthened by addition of Co and TiN particles in Ni matrix. Kalaignan [18] prepared NieCoeTiO2 composite coatings from acetate bath and found that the hardness and anti-corrosion capability were reinforced in the presence of TiO2 by pulse reversal methods. Gao [23] fabricated sol-enhanced NieCoeTiO2 coating and found a large improvement in mechanical properties. Due to the excellent characteristics in hardness, strength, thermal stability and fracture toughness [24,25], ZrO2 nanoparticles exhibit potential advantages in the preparation of nanocomposites. It was expected that [26] the presence of ZrO2 particles in NieCo
https://doi.org/10.1016/j.jallcom.2019.153158 0925-8388/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
2
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
matrix could obtain composites with outstanding properties, such as high hardness and wear resistance. As a rare earth oxide, CeO2 owns unique physical and chemical properties. It was reported that CeO2 could effectively improve the corrosion and wear resistance of metallic matrix [27]. So, it is well expected that ZrO2 and CeO2 dual particles doped NieCo matrix coating has more superior corrosion resistance and mechanical properties. However, to our knowledge, no work has been dedicated to the preparation of NieCoeZrO2eCeO2 nanocomposites. Its corrosion behaviors have not been reported yet [28]. Till now, the effect of current density and duty cycle on the structure and corrosion properties of the nanocomposites has not been studied. Therefore, this work aims to prepare NieCoeZrO2 nanocomposites doped with ceria nanoparticles via pulse electrodeposition to improve its structure, electrochemical and anti-wear properties. The effects of electrodeposition conditions on structure, corrosion and wear resistance were investigated. This coating shows good potential for engineering applications in corrosive medium. 2. Experimental 2.1. Coating preparation Fig. 1 illustrated the schematic diagram of the electrodeposition system. A nickel plate was used as anode, which can produce Ni2þ and then replenish the reduced Ni2þ during the deposition process. A copper sheet was used as cathode with 3.0 cm distance from the anode. A one-way pulse current in square wave mode was applied in the experiment. Table 1 listed the chemical composition of the electrolyte and operation parameters. Analytic reagents and distilled water were used to prepare electrolyte. NiSO4$6H2O and NiCl2$6H2O was the main supplier of Ni2þ during the deposition process. Cl could adsorb on the anode and then prevented passivation of nickel anode. H3BO3 stabilized the pH of the plating bath. The Ni2þ, Co2þ ions adsorbed on the cathode were reduced to metal atoms via obtaining electrons. ZrO2 and CeO2 particles were commercially
provided in diameter of 40 nm. Magnetic stirring was conducted to suspend nanoparticles in deposition process. Before electrodeposition, the nanoparticles were ultrasonically treated for 30 min and mechanically agitated for 2 h to guarantee the full suspension in solution. The bath temperature was controlled at 50 C by a constant temperature water bath. The pH was controlled at 4.2 ± 0.1 with dilute sulfuric acid or sodium hydroxide solution. All substrates were first polished with alumina polishing paste (0.1 mm), rinsed by water, and then ultrasonically treated in alcohol for 5 min. It was immersed in a dilute hydrochloric acid solution for about 30 s and then vertically immersed in the electroplating bath. After electrodeposition, the sample was taken out, treated by an ultrasonic cleaner to wash off the adsorbed particles. 2.2. Characterization The nanoparticles were observed by field emission transmission electron microscope (FETEM, JEOL JEM-2000EX, Japan). Atomic force microscope (AFM, NT-MDT Prima) in tapping mode was utilized to analyze the topography and roughness of the coating. The phase composition and crystallite size were measured by D8 advance-Bruker XRD with Cu Ka radiation (l ¼ 0.15406 nm) in 2q 20e90 at 5 /min. The crystallite size was obtained according to the Scherrer Eq. (1).
D¼
kl b cosq
(1)
In Eq. (1), the D represents crystalline size, k is 0.94, l is 0.15406 nm, b represents the FWHM. The surface element was studied by XPS (ESCALAB 250XI). Wear test was measured using a UMT-3 friction and wear tester at frequency 5 Hz and amplitude 5 mm under 10 N for dry-sliding. Counterparts were SiC balls with a diameter of 3 mm. Each sample was measured three times under the same condition and the average value was selected. A surface profiler (Alpha-Step IQ) was used to measure the wear track profile. Electrochemical measurements were carried out in a classic threeelectrode cell by an electrochemical workstation (CHI660E, Chenhua Instruments Co.) in a 3.5 wt% NaCl solution without stirring at ambient temperature. SCE and platinum foil was used as reference and auxiliary electrode, respectively. The as-deposited sample with 1 cm2 exposed area was acted as working electrode. The sample was soaked for 30 min to reach Eocp. EIS was measured from Eocp under 10 mV disturbance amplitude in the frequency of 105e102 Hz. 3. Results and discussion 3.1. Nanoparticles characterization
Fig. 1. Schematic diagram of the electrodeposition system.
TEM and XRD methods were used to characterize the nanoparticles. Fig. 2a shows that ZrO2 nanoparticles exhibit polygonal shape in diameters of 20e40 nm. The powder is the mixture of tetragonal and monoclinic ZrO2. The tetrahedral zirconia was the main component. It illustrated that the primary diffraction peak of ZrO2 was located at 30.1. As seen in Fig. 2b, the CeO2 nanoparticles also present polygonal shape in dimension of 15e60 nm. All particles shape is close to sphere. It was reported that spherical shaped particles resulted in better distribution in metal matrix than irregular ones [29]. Agglomeration of the nanoparticles was also noticed. This is because of the high surface energy of the nanopowders. TEM images show that the agglomeration degree of ceria is larger than zirconia. The XRD pattern of CeO2 reveals that the most intensive diffraction peak is located at 28.5 . The typical
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
3
Table 1 Bath formula and process parameters of the composite coating. Electrolyte formula (g L1)
Process parameters 220 g L1 40 g L1 40 g L1 30 g L1 25 g L1 10 g L1 1 g L1 0.01 g L1
NiSO4$6H2O NiCl2$6H2O CoSO4$7H2O H3BO3 ZrO2(f < 50 nm) CeO2 (f < 100 nm) Saccharine Sodium dodecyl sulfate (SDS)
pH temperature deposition time current density (ia) duty cycle (r) Frequency(f) Stirring rate current mode
4.2 ± 0.1 50 ± 1 C 20 min 2e8 A/dm2 30%e90% 100e1200 Hz, 400 ± 50 rpm pulse current
Fig. 2. TEM images and XRD patterns of (a1, a2) ZrO2 and (b1, b2) CeO2 nanoparticles.
intense lines correspond to the fcc structure. 3.2. Phase composition and crystallite size Fig. 3 presents the XRD spectra of the coatings obtained at different current density. The X-ray diffraction patterns are consistent with that of Nickel. The three peaks at about 44.6 , 51.6 and 76.5 correspond to Ni (111), Ni (200) and Ni (220) texture, respectively (PDF No. 04e0850). All coatings present a facecentered cubic structure. The preferred orientation is (111) and (200) planes, and the (111) plane was the dominant growth orientation. It indicated that the orientation of the growth texture has not changed under different current density. The small peak at about 28.6 is ascribed to CeO2 particles embedded in the coating. The small peak at 31.15 belongs to the ZrO2 nanoparticles in coating. The particle peak in X-ray diffraction pattern is small, which is because the nanoparticle content in coating is low. In Fig. 3, tiny Cu peaks were observed for sample of 2 A dm2 due to the thin thickness of the composites. When current density increases, the intensity of Ni (200) and (220) plane was slightly enhanced. The RTC and crystallite size was listed in Table 2. As current density increases from 2 to 8 A dm2, the crystallite size based on (111) plane increases from 16.9 nm up to 19.1 nm. It indicated that the coating has larger grain size and
rougher surface at high current density. The Ni (111) texture was the preferred orientation with dominant advantage. The RTC value of (111) plane slightly decreased from 49.53% down to 45.31%, and the RTC value of (200) texture slightly increased from 37.26% up to 48.0%. It suggested that the preferred orientation of (111) texture slightly decreased and (200) texture enhanced as current density increases. Fig. 4 shows the XRD patterns of the coating electrodeposited at different duty cycle. As seen, the duty cycle does not affect the phase composition, but slight changes in peak intensity were observed. The peak intensity is related to the crystallite size, which is affected by the embedded nanoparticles and Co content in the coating. The Co peak was not found because of the generation of a single solid solution of NieCo matrix. The RTC value varied with the duty cycle. The highest RTC of 51.98% was obtained at duty cycle of 70%, indicating the preferred orientation of (111) texture. The crystallite size was 17e20 nm depending on different duty cycles. The competition between nucleation rate and grain growth rate determines the size of the grain. If the nucleation rate was faster than the grain growth rate, the grain was refined. The embedded nanoparticles could provide a large number of nucleation sites, facilitates nucleation process and restrain grain growth. Pavlatou et al. [30] proposed that the grain refinement was ascribed to the addition of nanoparticles, which multiplies the nucleation sites,
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
4
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 3. (a) X-ray diffraction pattern of the composite coatings obtained at different current density; (b) Partially enlarged details (70%, 100 Hz).
immobilizes the grain boundary and then hinders crystal growth. Table 2 RTC and crystallite size of the nanocomposite coating. Samples
2 4 6 8
A A A A
30% 50% 70% 90%
dm2 dm2 dm2 dm2
RTC (%)
3.3. Cross-sectional observation
Crystallite size (nm)
Constant
(111)
(200)
(220)
(111)
(200)
(220)
49.53 51.98 47.95 45.31
37.26 37.38 41.10 48.00
13.21 10.64 10.96 6.69
16.9 17.3 18.5 19.1
10.8 12.6 12.4 12.4
14.3 13.3 15.1 14.9
70%, 100 Hz
48.39 42.77 51.98 42.00
41.71 47.66 37.38 49.80
9.91 9.57 10.64 8.20
18.9 19.5 17.3 18.8
12.7 12.6 12.6 13.2
15.6 15.6 13.3 13.2
4 A dm2, 100 Hz
Fig. 5 displays the cross-section of the nanocomposites. It can be seen that the coating thickness is about 10 mm. The bulk of the nanocomposites is uniform and compact. Defect such as crack, gap, delaminating has not been noticed in the interface between the coating and substrate, suggesting a satisfactory adhesion. On the top surface of the coating, the protrusion structure was also observed, as indicated in Fig. 5a. Fig. 5b shows the enlarged view of the local region marked with a red rectangle in Fig. 5a. It illustrated that nanoparticles in size about 40 nm have been uniformly and firmly embedded in the NieCo metallic matrix. No gaps, crevice and cracks were observed. It indicated that the nanocomposites were successfully formed.
Fig. 4. (a) X-ray diffraction pattern of the composite coatings obtained at different duty cycle; (b) Partially enlarged details (4 A dm2, 100 Hz).
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
5
Fig. 5. (a) Cross-sectional images of the nanocomposites; (b) Local enlarged details.
3.4. Surface topography and roughness Surface topography of the composite coating fabricated at duty cycle of 70% and 30% were investigated by AFM. As shown in Fig. 6, there are many protrusions and gaps with rough structure on the coating. The diameter of the larger protrusions is about 2e4 mm. It seems that the protrusions like “islands” and the gaps like “valley.” These protrusions are composed of many clusters with different size distributed on the surface. The clusters and protrusions were sparsely dispersed on the relatively flat coating. Carefully observed can found that these clusters were composed of particles and cellular grains and varies in diameter from approximately 1 mm to 3 mm. Partial granules are the nanoparticles coated with fine-sized NieCo grains. Many granules dispersed on the surface of the clusters and also distributed on the dense coating as shown in Fig. 6a. Meanwhile, some gullies were also noticed, as shown in
Fig. 6c,d. Here, the formation of these protrusions, clusters, and gullies are partly attributed to the aggregation of nanoparticles, resulting in a rougher surface. Due to the “tip discharge effect”, once defects such as micro protrusion, cellular bulges or pits appeared on the growth interface, the metallic ions are preferentially adsorbed on the “tip” sites and reduced to metal atom, forming the protrusion structure. Finally, larger protrusions will be formed as the deposition time increases. At the beginning of the electrodeposition, the coating formed on the substrate was relatively flat. However, the surface of the substrate was not absolutely flat and the distribution of electric field line was not completely uniform. The regions where the growth rate is fast would form cellular bulges with a relatively rough surface. Due to the “tip discharge effect”, the electric field lines at the bulge regions are denser. Then, the growth rate is faster in protrusion area. With the extension of time, the protrusion becomes
Fig. 6. 3D topography of the composite coating deposited at (a, b) 70%, (c, d) 30% (4 A dm2, 100 Hz).
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
6
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
bigger and bigger. Finally, the growth on top of the bulges was preferred, forming many cauliflower-like protrusion clusters. These small cellular bulges like seeds. With the extending of deposition time, seeds grew continuously and formed clusters. Defects such as pinholes, pitting, and nodules, which are associated with the hydrogen evolution and impurities (dust, hydroxide, anode muds) on cathode surface, caused uneven distribution of the electric field line and promoted the formation of large protuberance and clusters. Fig. 7 shows that some protrusion clusters and gaps are dispersed on the surface of the coating. Table 3 shows the average roughness (Sa) and root mean square roughness (Sq) of these coatings. It shows that the coating obtained at duty cycle of 70% has the Sa, Sq of 74e85 nm, 105e118 nm, respectively. The coating deposited at 30% owns the Sa, Sq of 82e98 nm, 105e127 nm, respectively. It indicated that the roughness increased when duty cycle decreased to 30%. The coatings electrodeposited at 70% exhibited more finer hill-like protrusions. At low duty cycle of 30%, large “valley” was noticed and the granule size is large; the diameter of the dispersed hill-like protrusions is wider than 2 mm, and its
Table 3 The average (Sa) and root mean square (Sq) roughness of the nanocomposite coating. Coatings
Sa (nm)
Sq (nm)
Max height (nm)
a, r ¼ 70% b, r ¼ 70% c, r ¼ 30% d, r ¼ 30%
73.9 85.4 81.9 98.0
105.0 117.8 105.1 127.3
1052.6 1669.2 770.3 1002.2
height is about 770e1002 nm. When duty cycle is 70%, many small granules emerged containing distributed fine grains. The gap between the protrusions was deeper at duty cycle of 30%. The granule size of 70% is finer than that of 30%. It suggested that the duty cycle of 70% benefits smooth and fine-grained structure. This composite coating has numerous micro protrusions and poor flatness, resulting in high roughness. 3.5. Chemical composition Fig. 8 shows that the Ni, Co, Zr, Ce, and O elements were
Fig. 7. Surface morphology of the composite coating deposited at (a, b) 70%, (c, d) 30% (4 A dm2, 100 Hz).
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
7
Fig. 9. Chemical composition of the nanocomposites obtained at different duty cycle.
uniformly distributed throughout the coating. However, the distribution of ZrO2 and CeO2 nanoparticles in the nanocomposite coating are not very homogeneous. Some agglomerations were observed on the coating which was related to the high surface energy of the nanomaterial. Now, aggregations of nanoparticles have not been completely resolved. In general, the particles distribution in the nanocomposite is approximately uniform.
Fig. 8. (a) EDS spectrum and (b) chemical composition of the nanocomposites obtained at different current density.
3.6. Formation mechanism
presented in the EDS pattern. As shown in Fig. 8, the content of Ni increased from 45.87 wt% up to 63.34 wt% as current density increased from 2 to 8 A dm2, Meanwhile, the Co content in the composite coating decreased from 36.89 wt% down to 20.87 wt%. It shows that the amount of Co in NieCo matrix was decreased and the Ni content was increased as current density increases, indicating that low current density is beneficial to the co-deposition of Co in the NieCo matrix. The composite coating also contains 13.53e14.36 wt% Zr, 0.22e0.78 wt% Ce and 2.04e2.95 wt% O elements. The content of ZrO2, CeO2 should be determined according to the content of Zr, Ce measured by EDS and the stoichiometry of ZrO2 and CeO2 oxide, respectively. The maximum Co content in NieCo alloy was 36.89 wt% at 2 A dm2. Compared to the ZrO2, the CeO2 content in the coating is low. The composition of the composite coating slightly varied at different current density. Fig. 9 presents the effects of duty cycle on the EDS results. It shows that the content of Ni, Co, Zr, and Ce element in the coating varied with the duty cycle. The composite coating contains 53.34e66.08 w.% Ni, 19.54e29.23 wt% Co, 12.35e14.36 wt% Zr, 0.17e2.09 wt% Ce and 1.58e2.9 wt% O elements. The minimum content of Ni was 53.34 wt%, and the maximum content of Co was 29.23 wt%, which was obtained at duty cycle of 70%. At the same time, the Zr content reaches the maximum value at duty cycle of 70%. The content of Zr slightly varied in the range of 12.3e14.4 wt% with different duty cycles. It was noticed that the content of Ce was more sensitive to the duty cycle. The highest content of 2.09 wt% was obtained at 30% and the lowest content of 0.17 wt% was achieved at duty cycle of 70%. These results indicate that the amount of Co and Ce incorporated in Ni matrix are affected by duty cycles. Fig. 10 shows the EDS mapping of NieCoeZrO2eCeO2 nanocomposites. It indicated that the nanocomposite comprises Ni, Co, Zr, Ce and O elements. It was confirmed that Ni and Co were
Fig. 11a shows the formation mechanism of the nanocomposites. Suspended in electrolyte, the nanoparticles were absorbed with some Ni2þ and Co2þ ions and positively charged. When the current is applied, the electric field was simultaneously formed between the anode and cathode. Then, driven by the electric field force and mechanical agitation, the metal ions (Ni2þ, Co2þ) and positively charged particles begin to transport to cathode along the electric field lines [31]. Subsequently, Ni2þ, Co2þ ions were quickly reduced to metal atoms on the cathode, and the absorbed particles were incorporated into NieCo matrix, forming particles doped NieCo matrix coating [31]. The forming mechanism of protrusion clusters was also shown in Fig. 11b. When the surface was relatively flat, the growth rate over the substrate is basically the same, and the crystal cells grew uniformly. At this stage, the coating was composed of crystal grains in similar size. Due to the “tip discharge effect”, the growth rate on bulges is faster than other areas [31]. Therefore, the Ni2þ ions were preferentially reduced at the protrusions, forming many crystal nuclei on it. Therefore, the composite coating is more likely to grow at the bulges. As a result, the larger protrusions formed. Besides, the protrusions were charged in electric field with the same electric charge. Then, the repulsive force was emerged between them to ensure vertical growth. Finally, the clusters were formed [32]. The detailed growing process for the composite coating was proposed in Fig. 12. Firstly, the particles were absorbed with some Ni2þ and Co2þ ions and positively charged in electrolyte. Then, the metal ions and charged particles were transported to and loosely absorbed on the cathode surface. At this “weak adsorption” stage, most of the nanoparticles could be removed under the scouring of the solution. As well known, the size of nanoparticles is larger than Ni2þ and Co2þ ions, and they are hard to adhere to the cathode surface [33]. Soon, the nickel ions both in solution and covered on the nanoparticles had been reduced to metal atoms on the cathode surface, which produces strong adsorption force. In this “strong
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
8
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 10. EDS element mapping of the nanocomposite coating.
Fig. 11. Schematic diagram of (a) the co-deposition mechanism and (b) the formation of protrusion cluster and gap structure.
adsorption” stage, the nanoparticles were strongly adsorbed onto the newly formed coating matrix. This process is in accordance with the co-deposition mechanism reported by Guglielm [34].
3.7. XPS analysis Fig. 13 shows the XPS patterns of the nanocomposites fabricated at 100 Hz, 70% and 4 A dm2. The survey spectrum (Fig. 13a) illustrated the presence of Ni, Co, Zr, Ce, O and C components. Fig. 13b depicts that the Ni 2p3/2 XPS has three peaks. The diffraction peak at 851.84 eV with the area of 9.03 103 is related to zero valence nickel metal (Ni0). The peak at 855.20 eV with area of 1.22 105 is related to Ni2þ species such as NiO, Ni(OH)2. The nickel oxide originated from surface oxidation of the nickel matrix [35]. The presence of nickel hydroxide is related to the hydrogen evolution in cathode during the electrodeposition. The peak at 860.93 eV with area of 4.84 104 is ascribed to satellite nickel in
the form of Ni3þ species, such as NiOOH. Fig. 13c depicts the Co2p3/2 XPS of the coating. The peak at 777.26 eV with the area of 4.96 103 is related to elemental cobalt (Co0). The peak at 780.52 eV with area of 9.32 104 belongs to oxidized cobalt (Co2þ). The peak at 785.22 eV with area of 1.80 104 belongs to satellite cobalt. The Co element comes from the reduction of Co2þ in plating bath. Combined with EDS results, it was found that the Co content was higher at duty cycle of 70% and 2 A dm2. Fig. 13d displays the Zr 3d XPS. The peaks at 181.85 eV, 184.19 eV belong to Zr3d5/2 and Zr3d3/2, respectively. Also, their corresponding peak area is 2.67 104, 1.74 104, respectively. It illustrated the incorporation of ZrO2 in the NieCo matrix. The Zr element comes from the source of ZrO2 added in the electrolyte. Fig. 13e presents the Ce3d XPS spectra. Cerium primarily exists in form of Ce4þ species, which is attributed to the doped CeO2 particles. The peak intensity of cerium is relatively weak because of the low amount doped in the coating. Fig. 13f shows that C 1s XPS has
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
9
Fig. 12. Schematic of the growing process for the nanocomposites.
Fig. 13. XPS survey spectra (a) and the core level spectra of (b) Ni 2p3/2, (c) Co 2p3/2, (d) Zr 3d, (e) Ce 3d and (f) C1s of the composite coating in as-deposited state.
four deconvoluted peaks, corresponding to CeH (284.12 eV), CeC (284.58 eV), CeO (284.81 eV) and COx (288.16 eV), respectively. Their area is 1.75 104, 1.28 104, 2.83 104 and 1.21 104, respectively. The carbon came from organic additives (SDS, saccharine) in bath or external carbon contamination. 3.8. Corrosion and wear resistance The stability is crucial to their applications in industrial field, especially the corrosion and wear behavior. Fig. 14 depicts the
Nyquist plots of the nanocomposites obtained at different current density and duty cycle after immersed 7 days in 3.5 wt% NaCl solution. Fig. 15 shows the equivalent electrical circuits (EEC) for fitting the EIS curves, where the Rs, Rct and CPEdl is solution resistance, charge transfer resistance and double layer capacitance, respectively. All the EIS curves could be well fitted by the one-time constant Rs(RctCPEdl) EEC model. So, the EEC model as shown in Fig. 15 was used to fit the Nyquist curves. As shown in Fig. 14, all Nyquist curves present a depressed capacitive loop in various radius. The corrosion parameters were
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
10
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 14. Effect of (a) current density and (b) duty cycle on Nyquist plots of the composite coatings after immersed for 7 days, other parameters (a) 70%, 100 Hz; (b) 4 A dm2, 100 Hz.
Fig. 15. Equivalent electrical circuit (EEC) model.
listed in Table 4. When immersed for 7 days, the Rct of the composite coating was 57.12, 30.75, 35.83 and 42.63 kU cm2 corresponding to the coating obtained at 2, 4, 6 and 8 A dm2, respectively. The Rct of the coating obtained at 2, 8 A dm2 are larger than 42 kU cm2, while the coating of 4 and 6 A dm2 is less than 36 kU cm2. This may be due to the dense and compact structure of the coating deposited at 2 A dm2, which exhibits better performance. Due to the large current density, the coating of 8 A dm2 has large thickness, which is helpful to the physical shielding. It shows that the capacitance loop radius of 2 A dm2 was the largest, indicating the highest corrosion resistance [36].
Table 4 The fitted corrosion parameters of the nanocomposites. Time
Rct (kU$cm2)
CPEdl (mF cm2)
2
Samples
1h
2 4 6 8
A A A A
dm dm2 dm2 dm2
48.169 75.777 59.941 54.019
26.64 29.94 24.41 25.59
7 days
2 4 6 8
A A A A
dm2 dm2 dm2 dm2
57.120 30.753 35.828 42.631
60.96 72.18 45.11 40.45
1h
30% 70% 90%
100.98 75.777 93.397
23.13 29.84 29.71
7 days
30% 70% 90%
67.136 30.753 41.295
44.03 72.18 63.91
Compared to other samples, the coating prepared at 2 A dm2 has the maximum Rct value of 57.12 kU cm2 and presents distinct advantages in corrosion resistance during the long-term immersion in 3.5 wt% NaCl corrosive medium. Fig. 14b shows the Nyquist diagrams for the composite obtained at different duty cycle. It indicated that the coating prepared at 30% has the largest Rct value of 67.14 kU cm2 when immersed for 168 h. The anti-corrosion capability of these coating is: 30% > 90%>70%. In general, the Rct of the coating obtained at 30% has the best corrosion resistance and electrochemical stability than other coatings. Fig. 16 shows the Bode diagrams for the samples obtained at different conditions after immersed 1 h and 7 days. In the first 1 h, the bode plot presents a broaden peak, suggesting a corrosion mechanism with one-time constant EEC model. In the initial stage of immersion (1 h), the corrosion resistance of the coating prepared at 2 A dm2 has no advantages compared to other samples. It should be noted that to improve the service life of a coating, the performance in the later stage of immersion is more important than in the initial stage, which determined its stability. Therefore, we pay more importance to the corrosion data immersed 7 days compared to 1 h. When immersed 7 days, the most of Bode plots still displayed one-time constant corrosion mechanism. As shown in Table 4, when immersion time increased to 7 days, the Rct of the sample at 2 A dm2 increases, but the Rct of the other samples decreases. It indicated that the sample at 2 A dm2 has the better electrochemical stability with the immersion time. The Rct of the coating obtained at 30% has the best electrochemical stability. It revealed that as the immersion time increases, the coating prepared at 2 A dm2, 30% has the largest Rct value of 57.12 and 67.14 kU cm2, respectively. It implied that the coating prepared at duty cycle of 30% and 2 A dm2 has excellent corrosion resistance and stability than other coatings. Corrosion was usually initiated from the surface. When the surface has defects (e.g., pores, pits and cracks), the corrosion solution can easily penetrate the inner part of the coating and accelerate its corrosion. The addition of nanoparticles supplied many nucleating sites for crystal growing and refined the grains, leading to uniform and dense structure. Moreover, nanoparticles could be effectively absorbed in the defects, playing a role in filling micropores and microcracks. Then, the compactness of the coating was improved. This prevents the corrosion media from permeating the coating and the corrosion resistance was enhanced. Besides, the
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
11
Fig. 16. Effects of (a, b) current density and (c, d) duty cycle on Bode diagrams of the composite coating after immersed (a, c) 1 h and (b, d) 7 days, other parameters (a, b) 70%, 100 Hz; (c, d) 4 A dm2, 100 Hz.
doped ZrO2 and CeO2 particles also enhanced the physical shielding effect due to its stable chemical properties. The nanocomposite coating formed without CeO2 in electrolyte was also investigated to confirm the role of CeO2 in the nanocomposite coating. Fig. 17a presents the XRD pattern of the NieCo/ ZrO2 composite coating. It illustrated that the CeO2 peaks at 28.6 were not appeared, indicating the absence of the CeO2 in the nanocomposites. The 3D topography (Fig. 17b) indicated that the presence of Ce in the coating has not changed the morphology much. They exhibit hill-valley like morphology. Fig. 17c, d present the Nyquist and Bode plots of NieCo/ZrO2 composite coating. When immersion time reaches 7 days, the Rct of the sample without CeO2 content is less than 40 kU cm2. However, the Rct of NieCo/ ZrO2eCeO2 nanocomposite could be more than 50 kU cm2. It revealed that the addition of CeO2 in the NieCo/ZrO2 composite could improve its corrosion resistance. Fig. 18 presents the friction coefficient and wear track profile of the nanocomposites prepared at different current density under dry-sliding condition (10 N, 5 Hz). Fig. 18a shows that the friction coefficient of the composites increases with the increase of the current density. The change of friction coefficient is related to the roughness, structure and phase composition of the composites which is affected by the current density. The wear track profiles are intuitive way to compare the wear rates of different samples. Large depth of the wear track profiles indicates the more wear volume
loss and high wear rate. Fig. 18b indicated that the depth of the wear track profiles for the coating obtained at 2 A dm2 was the smallest. It indicated that under the dry-sliding condition, the nanocomposites prepared at 2 A dm2 has the best wear resistance, which has the least volume loss in the wear tests. As well known, many factors could affect the wear resistance, such as structure, phase composition, nanoparticles, roughness, grain size, etc. Therefore, many influencing factors and mechanism about the wear behavior of the nanocomposites have not been fully clarified yet, and further research is still needed in the future works. Besides, it was known that CeO2 is nobler than nickel. The doped CeO2 in NieCo coating could shift corrosion potential to more positive values. Due to all the above factors, protective performance of the nanocomposite coatings was largely enhanced. However, the process parameters are interactive, and the relationship between them is complex. The interaction and coupling effect between parameters on the electrodeposition and protective performance is still needed to be further studied. 4. Conclusions A novel NieCoeZrO2 nanocomposite doped with ceria particles were synthesized by pulse current electrodeposition process. The influences of current density and duty cycle on structure, electrochemical and anti-wear behaviors were investigated. The
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
12
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 17. (a) XRD pattern, (b) AFM surface topography, (c, d) Nyquist and Bode plots of NieCo/ZrO2 composite coating.
Fig. 18. Friction coefficient and wear track profiles of the samples with current density under dry-sliding condition (10 N, 5 Hz).
nanocomposite coatings are rough, compact with hill-valley like morphology. The coating surface is rough with the average roughness (Sa) about 73e98 nm. The duty cycle of 70% benefits low roughness and fine-grained structure. The crystallite size of these coating is 17e20 nm. The nanocrystalline coating exhibits the preferred orientation of Ni (111) texture. As current density increases, the growth of Ni (200) and (220) texture is relatively
enhanced. Electrochemical measurements illustrated that the electrodeposition parameters significantly affect the corrosion behavior of the composites. The corrosion resistance varied with immersing time. Duty cycle of 30% and current density of 2 A dm2 was the suitable parameter for the optimal corrosion and wear resistance and desirable electrochemical stability in the long-term service in aggressive media.
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Author contributions sections Baosong Li: Investigation, Methodology, Resources, Writing e Original Draft & Editing. Weiwei Zhang: Conceptualization, Resources, Funding acquisition. Author agreement We warrant that the article is the authors’ original work, hasn’t received prior publication and isn’t under consideration for publication elsewhere. We certify that all authors have seen and approved the final version of the manuscript being submitted. Declaration of competing interest I would like to declare on behalf of my co-authors that no conflict of interest exists in the submission of this manuscript. There have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was supported by the National Natural Science Foundation of China (51679076), the Fundamental Research Funds for the Central Universities (2019B15914). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jallcom.2019.153158. References [1] W. Jiang, L. Shen, M. Qiu, X. Wang, M. Fan, Z. Tian, Preparation of Ni-SiC composite coatings by magnetic field-enhanced jet electrodeposition, J. Alloy. Comp. 762 (2018) 115e124. [2] C. Wang, L. Shen, M. Qiu, Z. Tian, W. Jiang, Characterizations of Ni-CeO 2 nanocomposite coating by interlaced jet electrodeposition, J. Alloy. Comp. 727 (2017) 269e277. [3] M. Xu, L. Shen, W. Jiang, F. Zhao, Y. Chen, Z. Tian, Fabrication of Ni-SiC superhydrophilic surface by magnetic field-assisted scanning electrodeposition, J. Alloy. Comp. 799 (2019) 224e230. [4] W. Jiang, L. Shen, M. Xu, Z. Wang, Z. Tian, Mechanical properties and corrosion resistance of Ni-Co-SiC composite coatings by magnetic field-induced jet electrodeposition, J. Alloy. Comp. 791 (2019) 847e855. [5] L. Shen, M. Fan, M. Qiu, W. Jiang, Z. Wang, Superhydrophobic nickel coating fabricated by scanning electrodeposition, Appl. Surf. Sci. 483 (2019) 706e712. [6] S.M. Lari Baghal, A. Amadeh, M. Heydarzadeh Sohi, Investigation of mechanical properties and operative deformation mechanism in nano-crystalline NieCo/SiC electrodeposits, Mater. Sci. Eng. A 542 (2012) 104e112. [7] N. Elkhoshkhany, A. Hafnway, A. Khaled, Electrodeposition and corrosion behavior of nano-structured NieWC and NieCoeWC composite coating, J. Alloy. Comp. 695 (2017) 1505e1514. [8] L. Shi, C. Sun, P. Gao, F. Zhou, W. Liu, Mechanical properties and wear and corrosion resistance of electrodeposited NieCo/SiC nanocomposite coating, Appl. Surf. Sci. 252 (2006) 3591e3599. lez-Buch, I. Herraiz-Cardona, E. Ortega, J. García-Anto n, V. Pe rez[9] C. Gonza Herranz, Synthesis and characterization of macroporous Ni, Co and NieCo electrocatalytic deposits for hydrogen evolution reaction in alkaline media, Int. J. Hydrogen Energy 38 (2013) 10157e10169. [10] L.L. Tian, J.C. Xu, C.W. Qiang, The electrodeposition behaviors and magnetic properties of Ni-Co films, Appl. Surf. Sci. 257 (2011) 4689e4694. [11] A. Rasooli, M.S. Safavi, M. Kasbkar Hokmabad, Cr2O3 nanoparticles: a promising candidate to improve the mechanical properties and corrosion
13
resistance of Ni-Co alloy coatings, Ceram. Int. 44 (2018) 6466e6473. [12] Y. Yang, Y.F. Cheng, Mechanistic aspects of electrodeposition of Ni-Co-SiC composite nano-coating on carbon steel, Electrochim. Acta 109 (2013) 638e644. [13] B. Bakhit, A. Akbari, Synthesis and characterization of NieCo/SiC nanocomposite coatings using sediment co-deposition technique, J. Alloy. Comp. 560 (2013) 92e104. [14] Y. Yang, Y.F. Cheng, Fabrication of NieCoeSiC composite coatings by pulse electrodeposition d effects of duty cycle and pulse frequency, Surf. Coat. Technol. 216 (2013) 282e288. [15] Y. Yang, Y.F. Cheng, Electrolytic deposition of NieCoeSiC nano-coating for erosion-enhanced corrosion of carbon steel pipes in oilsand slurry, Surf. Coat. Technol. 205 (2011) 3198e3204. [16] A. Hefnawy, N. Elkhoshkhany, A. Essam, NieTiN and NieCoeTiN composite coatings for corrosion protection: fabrication and electrochemical characterization, J. Alloy. Comp. 735 (2018) 600e606. [17] G.-f. Wang, S.-s. Jiang, Z. Lu, K.-f. Zhang, Preparation and tensile properties of Al2O3/Ni-Co nanocomposites, Trans. Nonferrous Metals Soc. China 21 (2011) s374es379. [18] B. Ranjith, G. Paruthimal Kalaignan, NieCoeTiO2 nanocomposite coating prepared by pulse and pulse reversal methods using acetate bath, Appl. Surf. Sci. 257 (2010) 42e47. [19] Y. Wang, Z. Xu, Nanostructured NieWCeCo composite coatings fabricated by electrophoretic deposition, Surf. Coat. Technol. 200 (2006) 3896e3902. [20] B. Bakhit, The influence of electrolyte composition on the properties of NieCo alloy coatings reinforced by SiC nano-particles, Surf. Coat. Technol. 275 (2015) 324e331. [21] L.M. Chang, M.Z. An, H.F. Guo, S.Y. Shi, Microstructure and properties of Ni-Co/ nano-Al2O3 composite coatings by pulse reversal current electrodeposition, Appl. Surf. Sci. 253 (2006) 2132e2137. [22] L.M. Chang, H.F. Guo, M.Z. An, Electrodeposition of Ni-Co/Al2O3 composite coating by pulse reverse method under ultrasonic condition, Mater. Lett. 62 (2008) 3313e3315. [23] Y. Wang, S.L. Tay, S. Wei, C. Xiong, W. Gao, R.A. Shakoor, R. Kahraman, Microstructure and properties of sol-enhanced Ni-Co-TiO2 nano-composite coatings on mild steel, J. Alloy. Comp. 649 (2015) 222e228. [24] H. Luo, X. Wang, S. Gao, C. Dong, X. Li, Synthesis of a duplex NiePeYSZ/NieP nanocomposite coating and investigation of its performance, Surf. Coat. Technol. 311 (2017) 70e79. [25] B. Ma, Y. Li, J. Zhao, X. Li, W. Xin, Novel structural functional films based on self-assembly template and electrodeposition: synthesis and characterization of porous Ni/YSZ films, Thin Solid Films 517 (2009) 5172e5175. [26] M. Zarabian, A.Y. Yar, S. Vafaeenezhad, M.A.F. Sani, A. Simchi, Electrophoretic deposition of functionally-graded NiOeYSZ composite films, J. Eur. Ceram. Soc. 33 (2013) 1815e1823. [27] J.K. Pancrecious, J.P. Deepa, V. Jayan, U.S. Bill, T.P.D. Rajan, B.C. Pai, Nanoceria induced grain refinement in electroless Ni-B-CeO2 composite coating for enhanced wear and corrosion resistance of Aluminium alloy, Surf. Coat. Technol. 356 (2018) 29e37. [28] Z. Qu, X. Cheng, J. Wu, R. He, Y. Pei, D. Fang, An investigation on erosion behavior of nanostructured 7YSZ coatings at elevated temperature, Surf. Coat. Technol. 299 (2016) 129e134. [29] E. Beltowska-Lehman, P. Indyka, A. Bigos, M.J. Szczerba, M. Kot, NieW/ZrO2 nanocomposites obtained by ultrasonic DC electrodeposition, Mater. Des. 80 (2015) 1e11. [30] E.A. Pavlatou, M. Stroumbouli, P. Gyftou, N. Spyrellis, Hardening effect induced by incorporation of SiC particles in nickel electrodeposits, J. Appl. Electrochem. 36 (2005) 385e394. [31] I. Tudela, Y. Zhang, M. Pal, I. Kerr, A.J. Cobley, Ultrasound-assisted electrodeposition of thin nickel-based composite coatings with lubricant particles, Surf. Coat. Technol. 276 (2015) 89e105. [32] Z. Wang, L. Shen, W. Jiang, M. Fan, D. Liu, J. Zhao, Superhydrophobic nickel coatings fabricated by scanning electrodeposition on stainless steel formed by selective laser melting, Surf. Coat. Technol. 377 (2019) 124886. [33] A. Mukhopadhyay, T.K. Barman, P. Sahoo, Friction and wear performance of electroless Ni-B coatings at different operating temperatures, Silicon 11 (2018) 721e731. [34] N. Guglielmi, Kinetics of the deposition of inert particles from electrolytic baths, J. Electrochem. Soc. 119 (1972). [35] J. Winiarski, B. Cieslikowska, W. Tylus, P. Kunicki, B. Szczygieł, Corrosion of nanocrystalline nickel coatings electrodeposited from choline chloride: ethylene glycol deep eutectic solvent exposed in 0.05 M NaCl solution, Appl. Surf. Sci. 470 (2019) 331e339. [36] T. He, Y. He, H. Li, Z. Su, Y. Fan, Z. He, Fabrication of Ni-W-B4C composite coatings and evaluation of its micro-hardness and corrosion resistance properties, Ceram. Int. 44 (2018) 9188e9193.
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
Contents lists available at ScienceDirect
Journal of Alloys and Compounds journal homepage: http://www.elsevier.com/locate/jalcom
Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating Baosong Li a, Weiwei Zhang b, * a b
College of Mechanics and Materials, Hohai University, Nanjing, 211100, China College of Mechanical and Electrical Engineering, Hohai University, Changzhou, 213022, China
a r t i c l e i n f o
a b s t r a c t
Article history: Received 28 September 2019 Received in revised form 20 November 2019 Accepted 22 November 2019 Available online xxx
A novel NieCoeZrO2 nanocomposites doped with ceria particles has been synthesized by pulse electrodeposition as highly protective coating. The effect of current density and duty cycle on its structure and properties were evaluated. The composite coatings are compact with hill-valley like structure. The average roughness (Sa) was about 73e98 nm and the duty cycle of 70% benefits low roughness and finegrained structure. The crystallite size of these coatings is 17e20 nm. The nanocrystalline coating exhibits the preferred orientation of Ni (111) texture. AFM and XPS were utilized to analyze the surface properties. EIS results indicated that the electrodeposition parameters greatly affect the corrosion behavior of the nanocomposites. The electrochemical behavior varied with immersing time. Duty cycle of 30%, current density of 2 A dm2 were the appropriate parameters for the best corrosion and wear resistance and optimal long-term electrochemical stability in 3.5 wt% NaCl corrosive solution. This coating shows good potential for engineering application in aggressive medium. © 2019 Elsevier B.V. All rights reserved.
Keywords: Nanocomposite coating NieCoeZrO2eCeO2 Pulse electrodeposition Corrosion behavior Electrochemical impedance spectroscopy
1. Introduction The performance stability of a material is significant for the applications in corrosive medium, which usually requires high corrosion and wear resistance [1,2]. Electrodeposition exhibits the merits of simple, flexible, inexpensive, controllable and efficient, and was extensively applied in many fields as surface protective coating [3,4]. Nickel or its alloy is an important protective coating and could protect metallic substrate from corrosion and wear when it deposited on its surface [5]. Due to their unique advantages in strength [6], corrosion resistance [7], wear-resistant [8], electrocatalytic [9] and magnetic properties [10], NieCo alloy has attracted extensive attention in application fields of magnetic storage, automobile, electrical and aerospace. However, further improvement in corrosion resistance and anti-wear properties is continuously desired to maintain its service life or broaden its applications in aggressive medium, such as marine engineering, mining, petroleum, and chemical industry. In recent years, many researchers focus on NieCo composite coating reinforced by nanoparticles to enhance its performance to
* Corresponding author. E-mail address: [email protected] (W. Zhang).
meet the special requirements for practical application [11]. The preparation of NieCo composite coating by electrodeposition has been studied by some researchers to enhance their mechanical, anti-corrosion, and thermal stability properties [12,13]. The ceramic particles such as SiC [14,15], TiN [16], Al2O3 [17], TiO2 [18], Cr2O3 [11] and WC [19] has been selected as reinforcing second phase in NieCo matrix. Bakhit [20] reported that the hardness and corrosion resistance of NieCo/SiC coating was significantly affected by the incorporated particles. An [21,22] investigated NieCo/Al2O3 composites and reported that Al2O3 content enhanced the hardness and wear resistance. Elkhoshkhany [7] prepared Ni-Co-WC composite coating and proved the increase in hardness. Hefnawy [16] revealed that corrosion-resistant properties and hardness of NieCoeTiN were substantially strengthened by addition of Co and TiN particles in Ni matrix. Kalaignan [18] prepared NieCoeTiO2 composite coatings from acetate bath and found that the hardness and anti-corrosion capability were reinforced in the presence of TiO2 by pulse reversal methods. Gao [23] fabricated sol-enhanced NieCoeTiO2 coating and found a large improvement in mechanical properties. Due to the excellent characteristics in hardness, strength, thermal stability and fracture toughness [24,25], ZrO2 nanoparticles exhibit potential advantages in the preparation of nanocomposites. It was expected that [26] the presence of ZrO2 particles in NieCo
https://doi.org/10.1016/j.jallcom.2019.153158 0925-8388/© 2019 Elsevier B.V. All rights reserved.
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
2
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
matrix could obtain composites with outstanding properties, such as high hardness and wear resistance. As a rare earth oxide, CeO2 owns unique physical and chemical properties. It was reported that CeO2 could effectively improve the corrosion and wear resistance of metallic matrix [27]. So, it is well expected that ZrO2 and CeO2 dual particles doped NieCo matrix coating has more superior corrosion resistance and mechanical properties. However, to our knowledge, no work has been dedicated to the preparation of NieCoeZrO2eCeO2 nanocomposites. Its corrosion behaviors have not been reported yet [28]. Till now, the effect of current density and duty cycle on the structure and corrosion properties of the nanocomposites has not been studied. Therefore, this work aims to prepare NieCoeZrO2 nanocomposites doped with ceria nanoparticles via pulse electrodeposition to improve its structure, electrochemical and anti-wear properties. The effects of electrodeposition conditions on structure, corrosion and wear resistance were investigated. This coating shows good potential for engineering applications in corrosive medium. 2. Experimental 2.1. Coating preparation Fig. 1 illustrated the schematic diagram of the electrodeposition system. A nickel plate was used as anode, which can produce Ni2þ and then replenish the reduced Ni2þ during the deposition process. A copper sheet was used as cathode with 3.0 cm distance from the anode. A one-way pulse current in square wave mode was applied in the experiment. Table 1 listed the chemical composition of the electrolyte and operation parameters. Analytic reagents and distilled water were used to prepare electrolyte. NiSO4$6H2O and NiCl2$6H2O was the main supplier of Ni2þ during the deposition process. Cl could adsorb on the anode and then prevented passivation of nickel anode. H3BO3 stabilized the pH of the plating bath. The Ni2þ, Co2þ ions adsorbed on the cathode were reduced to metal atoms via obtaining electrons. ZrO2 and CeO2 particles were commercially
provided in diameter of 40 nm. Magnetic stirring was conducted to suspend nanoparticles in deposition process. Before electrodeposition, the nanoparticles were ultrasonically treated for 30 min and mechanically agitated for 2 h to guarantee the full suspension in solution. The bath temperature was controlled at 50 C by a constant temperature water bath. The pH was controlled at 4.2 ± 0.1 with dilute sulfuric acid or sodium hydroxide solution. All substrates were first polished with alumina polishing paste (0.1 mm), rinsed by water, and then ultrasonically treated in alcohol for 5 min. It was immersed in a dilute hydrochloric acid solution for about 30 s and then vertically immersed in the electroplating bath. After electrodeposition, the sample was taken out, treated by an ultrasonic cleaner to wash off the adsorbed particles. 2.2. Characterization The nanoparticles were observed by field emission transmission electron microscope (FETEM, JEOL JEM-2000EX, Japan). Atomic force microscope (AFM, NT-MDT Prima) in tapping mode was utilized to analyze the topography and roughness of the coating. The phase composition and crystallite size were measured by D8 advance-Bruker XRD with Cu Ka radiation (l ¼ 0.15406 nm) in 2q 20e90 at 5 /min. The crystallite size was obtained according to the Scherrer Eq. (1).
D¼
kl b cosq
(1)
In Eq. (1), the D represents crystalline size, k is 0.94, l is 0.15406 nm, b represents the FWHM. The surface element was studied by XPS (ESCALAB 250XI). Wear test was measured using a UMT-3 friction and wear tester at frequency 5 Hz and amplitude 5 mm under 10 N for dry-sliding. Counterparts were SiC balls with a diameter of 3 mm. Each sample was measured three times under the same condition and the average value was selected. A surface profiler (Alpha-Step IQ) was used to measure the wear track profile. Electrochemical measurements were carried out in a classic threeelectrode cell by an electrochemical workstation (CHI660E, Chenhua Instruments Co.) in a 3.5 wt% NaCl solution without stirring at ambient temperature. SCE and platinum foil was used as reference and auxiliary electrode, respectively. The as-deposited sample with 1 cm2 exposed area was acted as working electrode. The sample was soaked for 30 min to reach Eocp. EIS was measured from Eocp under 10 mV disturbance amplitude in the frequency of 105e102 Hz. 3. Results and discussion 3.1. Nanoparticles characterization
Fig. 1. Schematic diagram of the electrodeposition system.
TEM and XRD methods were used to characterize the nanoparticles. Fig. 2a shows that ZrO2 nanoparticles exhibit polygonal shape in diameters of 20e40 nm. The powder is the mixture of tetragonal and monoclinic ZrO2. The tetrahedral zirconia was the main component. It illustrated that the primary diffraction peak of ZrO2 was located at 30.1. As seen in Fig. 2b, the CeO2 nanoparticles also present polygonal shape in dimension of 15e60 nm. All particles shape is close to sphere. It was reported that spherical shaped particles resulted in better distribution in metal matrix than irregular ones [29]. Agglomeration of the nanoparticles was also noticed. This is because of the high surface energy of the nanopowders. TEM images show that the agglomeration degree of ceria is larger than zirconia. The XRD pattern of CeO2 reveals that the most intensive diffraction peak is located at 28.5 . The typical
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
3
Table 1 Bath formula and process parameters of the composite coating. Electrolyte formula (g L1)
Process parameters 220 g L1 40 g L1 40 g L1 30 g L1 25 g L1 10 g L1 1 g L1 0.01 g L1
NiSO4$6H2O NiCl2$6H2O CoSO4$7H2O H3BO3 ZrO2(f < 50 nm) CeO2 (f < 100 nm) Saccharine Sodium dodecyl sulfate (SDS)
pH temperature deposition time current density (ia) duty cycle (r) Frequency(f) Stirring rate current mode
4.2 ± 0.1 50 ± 1 C 20 min 2e8 A/dm2 30%e90% 100e1200 Hz, 400 ± 50 rpm pulse current
Fig. 2. TEM images and XRD patterns of (a1, a2) ZrO2 and (b1, b2) CeO2 nanoparticles.
intense lines correspond to the fcc structure. 3.2. Phase composition and crystallite size Fig. 3 presents the XRD spectra of the coatings obtained at different current density. The X-ray diffraction patterns are consistent with that of Nickel. The three peaks at about 44.6 , 51.6 and 76.5 correspond to Ni (111), Ni (200) and Ni (220) texture, respectively (PDF No. 04e0850). All coatings present a facecentered cubic structure. The preferred orientation is (111) and (200) planes, and the (111) plane was the dominant growth orientation. It indicated that the orientation of the growth texture has not changed under different current density. The small peak at about 28.6 is ascribed to CeO2 particles embedded in the coating. The small peak at 31.15 belongs to the ZrO2 nanoparticles in coating. The particle peak in X-ray diffraction pattern is small, which is because the nanoparticle content in coating is low. In Fig. 3, tiny Cu peaks were observed for sample of 2 A dm2 due to the thin thickness of the composites. When current density increases, the intensity of Ni (200) and (220) plane was slightly enhanced. The RTC and crystallite size was listed in Table 2. As current density increases from 2 to 8 A dm2, the crystallite size based on (111) plane increases from 16.9 nm up to 19.1 nm. It indicated that the coating has larger grain size and
rougher surface at high current density. The Ni (111) texture was the preferred orientation with dominant advantage. The RTC value of (111) plane slightly decreased from 49.53% down to 45.31%, and the RTC value of (200) texture slightly increased from 37.26% up to 48.0%. It suggested that the preferred orientation of (111) texture slightly decreased and (200) texture enhanced as current density increases. Fig. 4 shows the XRD patterns of the coating electrodeposited at different duty cycle. As seen, the duty cycle does not affect the phase composition, but slight changes in peak intensity were observed. The peak intensity is related to the crystallite size, which is affected by the embedded nanoparticles and Co content in the coating. The Co peak was not found because of the generation of a single solid solution of NieCo matrix. The RTC value varied with the duty cycle. The highest RTC of 51.98% was obtained at duty cycle of 70%, indicating the preferred orientation of (111) texture. The crystallite size was 17e20 nm depending on different duty cycles. The competition between nucleation rate and grain growth rate determines the size of the grain. If the nucleation rate was faster than the grain growth rate, the grain was refined. The embedded nanoparticles could provide a large number of nucleation sites, facilitates nucleation process and restrain grain growth. Pavlatou et al. [30] proposed that the grain refinement was ascribed to the addition of nanoparticles, which multiplies the nucleation sites,
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
4
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 3. (a) X-ray diffraction pattern of the composite coatings obtained at different current density; (b) Partially enlarged details (70%, 100 Hz).
immobilizes the grain boundary and then hinders crystal growth. Table 2 RTC and crystallite size of the nanocomposite coating. Samples
2 4 6 8
A A A A
30% 50% 70% 90%
dm2 dm2 dm2 dm2
RTC (%)
3.3. Cross-sectional observation
Crystallite size (nm)
Constant
(111)
(200)
(220)
(111)
(200)
(220)
49.53 51.98 47.95 45.31
37.26 37.38 41.10 48.00
13.21 10.64 10.96 6.69
16.9 17.3 18.5 19.1
10.8 12.6 12.4 12.4
14.3 13.3 15.1 14.9
70%, 100 Hz
48.39 42.77 51.98 42.00
41.71 47.66 37.38 49.80
9.91 9.57 10.64 8.20
18.9 19.5 17.3 18.8
12.7 12.6 12.6 13.2
15.6 15.6 13.3 13.2
4 A dm2, 100 Hz
Fig. 5 displays the cross-section of the nanocomposites. It can be seen that the coating thickness is about 10 mm. The bulk of the nanocomposites is uniform and compact. Defect such as crack, gap, delaminating has not been noticed in the interface between the coating and substrate, suggesting a satisfactory adhesion. On the top surface of the coating, the protrusion structure was also observed, as indicated in Fig. 5a. Fig. 5b shows the enlarged view of the local region marked with a red rectangle in Fig. 5a. It illustrated that nanoparticles in size about 40 nm have been uniformly and firmly embedded in the NieCo metallic matrix. No gaps, crevice and cracks were observed. It indicated that the nanocomposites were successfully formed.
Fig. 4. (a) X-ray diffraction pattern of the composite coatings obtained at different duty cycle; (b) Partially enlarged details (4 A dm2, 100 Hz).
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
5
Fig. 5. (a) Cross-sectional images of the nanocomposites; (b) Local enlarged details.
3.4. Surface topography and roughness Surface topography of the composite coating fabricated at duty cycle of 70% and 30% were investigated by AFM. As shown in Fig. 6, there are many protrusions and gaps with rough structure on the coating. The diameter of the larger protrusions is about 2e4 mm. It seems that the protrusions like “islands” and the gaps like “valley.” These protrusions are composed of many clusters with different size distributed on the surface. The clusters and protrusions were sparsely dispersed on the relatively flat coating. Carefully observed can found that these clusters were composed of particles and cellular grains and varies in diameter from approximately 1 mm to 3 mm. Partial granules are the nanoparticles coated with fine-sized NieCo grains. Many granules dispersed on the surface of the clusters and also distributed on the dense coating as shown in Fig. 6a. Meanwhile, some gullies were also noticed, as shown in
Fig. 6c,d. Here, the formation of these protrusions, clusters, and gullies are partly attributed to the aggregation of nanoparticles, resulting in a rougher surface. Due to the “tip discharge effect”, once defects such as micro protrusion, cellular bulges or pits appeared on the growth interface, the metallic ions are preferentially adsorbed on the “tip” sites and reduced to metal atom, forming the protrusion structure. Finally, larger protrusions will be formed as the deposition time increases. At the beginning of the electrodeposition, the coating formed on the substrate was relatively flat. However, the surface of the substrate was not absolutely flat and the distribution of electric field line was not completely uniform. The regions where the growth rate is fast would form cellular bulges with a relatively rough surface. Due to the “tip discharge effect”, the electric field lines at the bulge regions are denser. Then, the growth rate is faster in protrusion area. With the extension of time, the protrusion becomes
Fig. 6. 3D topography of the composite coating deposited at (a, b) 70%, (c, d) 30% (4 A dm2, 100 Hz).
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
6
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
bigger and bigger. Finally, the growth on top of the bulges was preferred, forming many cauliflower-like protrusion clusters. These small cellular bulges like seeds. With the extending of deposition time, seeds grew continuously and formed clusters. Defects such as pinholes, pitting, and nodules, which are associated with the hydrogen evolution and impurities (dust, hydroxide, anode muds) on cathode surface, caused uneven distribution of the electric field line and promoted the formation of large protuberance and clusters. Fig. 7 shows that some protrusion clusters and gaps are dispersed on the surface of the coating. Table 3 shows the average roughness (Sa) and root mean square roughness (Sq) of these coatings. It shows that the coating obtained at duty cycle of 70% has the Sa, Sq of 74e85 nm, 105e118 nm, respectively. The coating deposited at 30% owns the Sa, Sq of 82e98 nm, 105e127 nm, respectively. It indicated that the roughness increased when duty cycle decreased to 30%. The coatings electrodeposited at 70% exhibited more finer hill-like protrusions. At low duty cycle of 30%, large “valley” was noticed and the granule size is large; the diameter of the dispersed hill-like protrusions is wider than 2 mm, and its
Table 3 The average (Sa) and root mean square (Sq) roughness of the nanocomposite coating. Coatings
Sa (nm)
Sq (nm)
Max height (nm)
a, r ¼ 70% b, r ¼ 70% c, r ¼ 30% d, r ¼ 30%
73.9 85.4 81.9 98.0
105.0 117.8 105.1 127.3
1052.6 1669.2 770.3 1002.2
height is about 770e1002 nm. When duty cycle is 70%, many small granules emerged containing distributed fine grains. The gap between the protrusions was deeper at duty cycle of 30%. The granule size of 70% is finer than that of 30%. It suggested that the duty cycle of 70% benefits smooth and fine-grained structure. This composite coating has numerous micro protrusions and poor flatness, resulting in high roughness. 3.5. Chemical composition Fig. 8 shows that the Ni, Co, Zr, Ce, and O elements were
Fig. 7. Surface morphology of the composite coating deposited at (a, b) 70%, (c, d) 30% (4 A dm2, 100 Hz).
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
7
Fig. 9. Chemical composition of the nanocomposites obtained at different duty cycle.
uniformly distributed throughout the coating. However, the distribution of ZrO2 and CeO2 nanoparticles in the nanocomposite coating are not very homogeneous. Some agglomerations were observed on the coating which was related to the high surface energy of the nanomaterial. Now, aggregations of nanoparticles have not been completely resolved. In general, the particles distribution in the nanocomposite is approximately uniform.
Fig. 8. (a) EDS spectrum and (b) chemical composition of the nanocomposites obtained at different current density.
3.6. Formation mechanism
presented in the EDS pattern. As shown in Fig. 8, the content of Ni increased from 45.87 wt% up to 63.34 wt% as current density increased from 2 to 8 A dm2, Meanwhile, the Co content in the composite coating decreased from 36.89 wt% down to 20.87 wt%. It shows that the amount of Co in NieCo matrix was decreased and the Ni content was increased as current density increases, indicating that low current density is beneficial to the co-deposition of Co in the NieCo matrix. The composite coating also contains 13.53e14.36 wt% Zr, 0.22e0.78 wt% Ce and 2.04e2.95 wt% O elements. The content of ZrO2, CeO2 should be determined according to the content of Zr, Ce measured by EDS and the stoichiometry of ZrO2 and CeO2 oxide, respectively. The maximum Co content in NieCo alloy was 36.89 wt% at 2 A dm2. Compared to the ZrO2, the CeO2 content in the coating is low. The composition of the composite coating slightly varied at different current density. Fig. 9 presents the effects of duty cycle on the EDS results. It shows that the content of Ni, Co, Zr, and Ce element in the coating varied with the duty cycle. The composite coating contains 53.34e66.08 w.% Ni, 19.54e29.23 wt% Co, 12.35e14.36 wt% Zr, 0.17e2.09 wt% Ce and 1.58e2.9 wt% O elements. The minimum content of Ni was 53.34 wt%, and the maximum content of Co was 29.23 wt%, which was obtained at duty cycle of 70%. At the same time, the Zr content reaches the maximum value at duty cycle of 70%. The content of Zr slightly varied in the range of 12.3e14.4 wt% with different duty cycles. It was noticed that the content of Ce was more sensitive to the duty cycle. The highest content of 2.09 wt% was obtained at 30% and the lowest content of 0.17 wt% was achieved at duty cycle of 70%. These results indicate that the amount of Co and Ce incorporated in Ni matrix are affected by duty cycles. Fig. 10 shows the EDS mapping of NieCoeZrO2eCeO2 nanocomposites. It indicated that the nanocomposite comprises Ni, Co, Zr, Ce and O elements. It was confirmed that Ni and Co were
Fig. 11a shows the formation mechanism of the nanocomposites. Suspended in electrolyte, the nanoparticles were absorbed with some Ni2þ and Co2þ ions and positively charged. When the current is applied, the electric field was simultaneously formed between the anode and cathode. Then, driven by the electric field force and mechanical agitation, the metal ions (Ni2þ, Co2þ) and positively charged particles begin to transport to cathode along the electric field lines [31]. Subsequently, Ni2þ, Co2þ ions were quickly reduced to metal atoms on the cathode, and the absorbed particles were incorporated into NieCo matrix, forming particles doped NieCo matrix coating [31]. The forming mechanism of protrusion clusters was also shown in Fig. 11b. When the surface was relatively flat, the growth rate over the substrate is basically the same, and the crystal cells grew uniformly. At this stage, the coating was composed of crystal grains in similar size. Due to the “tip discharge effect”, the growth rate on bulges is faster than other areas [31]. Therefore, the Ni2þ ions were preferentially reduced at the protrusions, forming many crystal nuclei on it. Therefore, the composite coating is more likely to grow at the bulges. As a result, the larger protrusions formed. Besides, the protrusions were charged in electric field with the same electric charge. Then, the repulsive force was emerged between them to ensure vertical growth. Finally, the clusters were formed [32]. The detailed growing process for the composite coating was proposed in Fig. 12. Firstly, the particles were absorbed with some Ni2þ and Co2þ ions and positively charged in electrolyte. Then, the metal ions and charged particles were transported to and loosely absorbed on the cathode surface. At this “weak adsorption” stage, most of the nanoparticles could be removed under the scouring of the solution. As well known, the size of nanoparticles is larger than Ni2þ and Co2þ ions, and they are hard to adhere to the cathode surface [33]. Soon, the nickel ions both in solution and covered on the nanoparticles had been reduced to metal atoms on the cathode surface, which produces strong adsorption force. In this “strong
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
8
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 10. EDS element mapping of the nanocomposite coating.
Fig. 11. Schematic diagram of (a) the co-deposition mechanism and (b) the formation of protrusion cluster and gap structure.
adsorption” stage, the nanoparticles were strongly adsorbed onto the newly formed coating matrix. This process is in accordance with the co-deposition mechanism reported by Guglielm [34].
3.7. XPS analysis Fig. 13 shows the XPS patterns of the nanocomposites fabricated at 100 Hz, 70% and 4 A dm2. The survey spectrum (Fig. 13a) illustrated the presence of Ni, Co, Zr, Ce, O and C components. Fig. 13b depicts that the Ni 2p3/2 XPS has three peaks. The diffraction peak at 851.84 eV with the area of 9.03 103 is related to zero valence nickel metal (Ni0). The peak at 855.20 eV with area of 1.22 105 is related to Ni2þ species such as NiO, Ni(OH)2. The nickel oxide originated from surface oxidation of the nickel matrix [35]. The presence of nickel hydroxide is related to the hydrogen evolution in cathode during the electrodeposition. The peak at 860.93 eV with area of 4.84 104 is ascribed to satellite nickel in
the form of Ni3þ species, such as NiOOH. Fig. 13c depicts the Co2p3/2 XPS of the coating. The peak at 777.26 eV with the area of 4.96 103 is related to elemental cobalt (Co0). The peak at 780.52 eV with area of 9.32 104 belongs to oxidized cobalt (Co2þ). The peak at 785.22 eV with area of 1.80 104 belongs to satellite cobalt. The Co element comes from the reduction of Co2þ in plating bath. Combined with EDS results, it was found that the Co content was higher at duty cycle of 70% and 2 A dm2. Fig. 13d displays the Zr 3d XPS. The peaks at 181.85 eV, 184.19 eV belong to Zr3d5/2 and Zr3d3/2, respectively. Also, their corresponding peak area is 2.67 104, 1.74 104, respectively. It illustrated the incorporation of ZrO2 in the NieCo matrix. The Zr element comes from the source of ZrO2 added in the electrolyte. Fig. 13e presents the Ce3d XPS spectra. Cerium primarily exists in form of Ce4þ species, which is attributed to the doped CeO2 particles. The peak intensity of cerium is relatively weak because of the low amount doped in the coating. Fig. 13f shows that C 1s XPS has
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
9
Fig. 12. Schematic of the growing process for the nanocomposites.
Fig. 13. XPS survey spectra (a) and the core level spectra of (b) Ni 2p3/2, (c) Co 2p3/2, (d) Zr 3d, (e) Ce 3d and (f) C1s of the composite coating in as-deposited state.
four deconvoluted peaks, corresponding to CeH (284.12 eV), CeC (284.58 eV), CeO (284.81 eV) and COx (288.16 eV), respectively. Their area is 1.75 104, 1.28 104, 2.83 104 and 1.21 104, respectively. The carbon came from organic additives (SDS, saccharine) in bath or external carbon contamination. 3.8. Corrosion and wear resistance The stability is crucial to their applications in industrial field, especially the corrosion and wear behavior. Fig. 14 depicts the
Nyquist plots of the nanocomposites obtained at different current density and duty cycle after immersed 7 days in 3.5 wt% NaCl solution. Fig. 15 shows the equivalent electrical circuits (EEC) for fitting the EIS curves, where the Rs, Rct and CPEdl is solution resistance, charge transfer resistance and double layer capacitance, respectively. All the EIS curves could be well fitted by the one-time constant Rs(RctCPEdl) EEC model. So, the EEC model as shown in Fig. 15 was used to fit the Nyquist curves. As shown in Fig. 14, all Nyquist curves present a depressed capacitive loop in various radius. The corrosion parameters were
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
10
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 14. Effect of (a) current density and (b) duty cycle on Nyquist plots of the composite coatings after immersed for 7 days, other parameters (a) 70%, 100 Hz; (b) 4 A dm2, 100 Hz.
Fig. 15. Equivalent electrical circuit (EEC) model.
listed in Table 4. When immersed for 7 days, the Rct of the composite coating was 57.12, 30.75, 35.83 and 42.63 kU cm2 corresponding to the coating obtained at 2, 4, 6 and 8 A dm2, respectively. The Rct of the coating obtained at 2, 8 A dm2 are larger than 42 kU cm2, while the coating of 4 and 6 A dm2 is less than 36 kU cm2. This may be due to the dense and compact structure of the coating deposited at 2 A dm2, which exhibits better performance. Due to the large current density, the coating of 8 A dm2 has large thickness, which is helpful to the physical shielding. It shows that the capacitance loop radius of 2 A dm2 was the largest, indicating the highest corrosion resistance [36].
Table 4 The fitted corrosion parameters of the nanocomposites. Time
Rct (kU$cm2)
CPEdl (mF cm2)
2
Samples
1h
2 4 6 8
A A A A
dm dm2 dm2 dm2
48.169 75.777 59.941 54.019
26.64 29.94 24.41 25.59
7 days
2 4 6 8
A A A A
dm2 dm2 dm2 dm2
57.120 30.753 35.828 42.631
60.96 72.18 45.11 40.45
1h
30% 70% 90%
100.98 75.777 93.397
23.13 29.84 29.71
7 days
30% 70% 90%
67.136 30.753 41.295
44.03 72.18 63.91
Compared to other samples, the coating prepared at 2 A dm2 has the maximum Rct value of 57.12 kU cm2 and presents distinct advantages in corrosion resistance during the long-term immersion in 3.5 wt% NaCl corrosive medium. Fig. 14b shows the Nyquist diagrams for the composite obtained at different duty cycle. It indicated that the coating prepared at 30% has the largest Rct value of 67.14 kU cm2 when immersed for 168 h. The anti-corrosion capability of these coating is: 30% > 90%>70%. In general, the Rct of the coating obtained at 30% has the best corrosion resistance and electrochemical stability than other coatings. Fig. 16 shows the Bode diagrams for the samples obtained at different conditions after immersed 1 h and 7 days. In the first 1 h, the bode plot presents a broaden peak, suggesting a corrosion mechanism with one-time constant EEC model. In the initial stage of immersion (1 h), the corrosion resistance of the coating prepared at 2 A dm2 has no advantages compared to other samples. It should be noted that to improve the service life of a coating, the performance in the later stage of immersion is more important than in the initial stage, which determined its stability. Therefore, we pay more importance to the corrosion data immersed 7 days compared to 1 h. When immersed 7 days, the most of Bode plots still displayed one-time constant corrosion mechanism. As shown in Table 4, when immersion time increased to 7 days, the Rct of the sample at 2 A dm2 increases, but the Rct of the other samples decreases. It indicated that the sample at 2 A dm2 has the better electrochemical stability with the immersion time. The Rct of the coating obtained at 30% has the best electrochemical stability. It revealed that as the immersion time increases, the coating prepared at 2 A dm2, 30% has the largest Rct value of 57.12 and 67.14 kU cm2, respectively. It implied that the coating prepared at duty cycle of 30% and 2 A dm2 has excellent corrosion resistance and stability than other coatings. Corrosion was usually initiated from the surface. When the surface has defects (e.g., pores, pits and cracks), the corrosion solution can easily penetrate the inner part of the coating and accelerate its corrosion. The addition of nanoparticles supplied many nucleating sites for crystal growing and refined the grains, leading to uniform and dense structure. Moreover, nanoparticles could be effectively absorbed in the defects, playing a role in filling micropores and microcracks. Then, the compactness of the coating was improved. This prevents the corrosion media from permeating the coating and the corrosion resistance was enhanced. Besides, the
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
11
Fig. 16. Effects of (a, b) current density and (c, d) duty cycle on Bode diagrams of the composite coating after immersed (a, c) 1 h and (b, d) 7 days, other parameters (a, b) 70%, 100 Hz; (c, d) 4 A dm2, 100 Hz.
doped ZrO2 and CeO2 particles also enhanced the physical shielding effect due to its stable chemical properties. The nanocomposite coating formed without CeO2 in electrolyte was also investigated to confirm the role of CeO2 in the nanocomposite coating. Fig. 17a presents the XRD pattern of the NieCo/ ZrO2 composite coating. It illustrated that the CeO2 peaks at 28.6 were not appeared, indicating the absence of the CeO2 in the nanocomposites. The 3D topography (Fig. 17b) indicated that the presence of Ce in the coating has not changed the morphology much. They exhibit hill-valley like morphology. Fig. 17c, d present the Nyquist and Bode plots of NieCo/ZrO2 composite coating. When immersion time reaches 7 days, the Rct of the sample without CeO2 content is less than 40 kU cm2. However, the Rct of NieCo/ ZrO2eCeO2 nanocomposite could be more than 50 kU cm2. It revealed that the addition of CeO2 in the NieCo/ZrO2 composite could improve its corrosion resistance. Fig. 18 presents the friction coefficient and wear track profile of the nanocomposites prepared at different current density under dry-sliding condition (10 N, 5 Hz). Fig. 18a shows that the friction coefficient of the composites increases with the increase of the current density. The change of friction coefficient is related to the roughness, structure and phase composition of the composites which is affected by the current density. The wear track profiles are intuitive way to compare the wear rates of different samples. Large depth of the wear track profiles indicates the more wear volume
loss and high wear rate. Fig. 18b indicated that the depth of the wear track profiles for the coating obtained at 2 A dm2 was the smallest. It indicated that under the dry-sliding condition, the nanocomposites prepared at 2 A dm2 has the best wear resistance, which has the least volume loss in the wear tests. As well known, many factors could affect the wear resistance, such as structure, phase composition, nanoparticles, roughness, grain size, etc. Therefore, many influencing factors and mechanism about the wear behavior of the nanocomposites have not been fully clarified yet, and further research is still needed in the future works. Besides, it was known that CeO2 is nobler than nickel. The doped CeO2 in NieCo coating could shift corrosion potential to more positive values. Due to all the above factors, protective performance of the nanocomposite coatings was largely enhanced. However, the process parameters are interactive, and the relationship between them is complex. The interaction and coupling effect between parameters on the electrodeposition and protective performance is still needed to be further studied. 4. Conclusions A novel NieCoeZrO2 nanocomposite doped with ceria particles were synthesized by pulse current electrodeposition process. The influences of current density and duty cycle on structure, electrochemical and anti-wear behaviors were investigated. The
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
12
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Fig. 17. (a) XRD pattern, (b) AFM surface topography, (c, d) Nyquist and Bode plots of NieCo/ZrO2 composite coating.
Fig. 18. Friction coefficient and wear track profiles of the samples with current density under dry-sliding condition (10 N, 5 Hz).
nanocomposite coatings are rough, compact with hill-valley like morphology. The coating surface is rough with the average roughness (Sa) about 73e98 nm. The duty cycle of 70% benefits low roughness and fine-grained structure. The crystallite size of these coating is 17e20 nm. The nanocrystalline coating exhibits the preferred orientation of Ni (111) texture. As current density increases, the growth of Ni (200) and (220) texture is relatively
enhanced. Electrochemical measurements illustrated that the electrodeposition parameters significantly affect the corrosion behavior of the composites. The corrosion resistance varied with immersing time. Duty cycle of 30% and current density of 2 A dm2 was the suitable parameter for the optimal corrosion and wear resistance and desirable electrochemical stability in the long-term service in aggressive media.
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158
B. Li, W. Zhang / Journal of Alloys and Compounds xxx (xxxx) xxx
Author contributions sections Baosong Li: Investigation, Methodology, Resources, Writing e Original Draft & Editing. Weiwei Zhang: Conceptualization, Resources, Funding acquisition. Author agreement We warrant that the article is the authors’ original work, hasn’t received prior publication and isn’t under consideration for publication elsewhere. We certify that all authors have seen and approved the final version of the manuscript being submitted. Declaration of competing interest I would like to declare on behalf of my co-authors that no conflict of interest exists in the submission of this manuscript. There have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Acknowledgements This work was supported by the National Natural Science Foundation of China (51679076), the Fundamental Research Funds for the Central Universities (2019B15914). Appendix A. Supplementary data Supplementary data to this article can be found online at https://doi.org/10.1016/j.jallcom.2019.153158. References [1] W. Jiang, L. Shen, M. Qiu, X. Wang, M. Fan, Z. Tian, Preparation of Ni-SiC composite coatings by magnetic field-enhanced jet electrodeposition, J. Alloy. Comp. 762 (2018) 115e124. [2] C. Wang, L. Shen, M. Qiu, Z. Tian, W. Jiang, Characterizations of Ni-CeO 2 nanocomposite coating by interlaced jet electrodeposition, J. Alloy. Comp. 727 (2017) 269e277. [3] M. Xu, L. Shen, W. Jiang, F. Zhao, Y. Chen, Z. Tian, Fabrication of Ni-SiC superhydrophilic surface by magnetic field-assisted scanning electrodeposition, J. Alloy. Comp. 799 (2019) 224e230. [4] W. Jiang, L. Shen, M. Xu, Z. Wang, Z. Tian, Mechanical properties and corrosion resistance of Ni-Co-SiC composite coatings by magnetic field-induced jet electrodeposition, J. Alloy. Comp. 791 (2019) 847e855. [5] L. Shen, M. Fan, M. Qiu, W. Jiang, Z. Wang, Superhydrophobic nickel coating fabricated by scanning electrodeposition, Appl. Surf. Sci. 483 (2019) 706e712. [6] S.M. Lari Baghal, A. Amadeh, M. Heydarzadeh Sohi, Investigation of mechanical properties and operative deformation mechanism in nano-crystalline NieCo/SiC electrodeposits, Mater. Sci. Eng. A 542 (2012) 104e112. [7] N. Elkhoshkhany, A. Hafnway, A. Khaled, Electrodeposition and corrosion behavior of nano-structured NieWC and NieCoeWC composite coating, J. Alloy. Comp. 695 (2017) 1505e1514. [8] L. Shi, C. Sun, P. Gao, F. Zhou, W. Liu, Mechanical properties and wear and corrosion resistance of electrodeposited NieCo/SiC nanocomposite coating, Appl. Surf. Sci. 252 (2006) 3591e3599. lez-Buch, I. Herraiz-Cardona, E. Ortega, J. García-Anto n, V. Pe rez[9] C. Gonza Herranz, Synthesis and characterization of macroporous Ni, Co and NieCo electrocatalytic deposits for hydrogen evolution reaction in alkaline media, Int. J. Hydrogen Energy 38 (2013) 10157e10169. [10] L.L. Tian, J.C. Xu, C.W. Qiang, The electrodeposition behaviors and magnetic properties of Ni-Co films, Appl. Surf. Sci. 257 (2011) 4689e4694. [11] A. Rasooli, M.S. Safavi, M. Kasbkar Hokmabad, Cr2O3 nanoparticles: a promising candidate to improve the mechanical properties and corrosion
13
resistance of Ni-Co alloy coatings, Ceram. Int. 44 (2018) 6466e6473. [12] Y. Yang, Y.F. Cheng, Mechanistic aspects of electrodeposition of Ni-Co-SiC composite nano-coating on carbon steel, Electrochim. Acta 109 (2013) 638e644. [13] B. Bakhit, A. Akbari, Synthesis and characterization of NieCo/SiC nanocomposite coatings using sediment co-deposition technique, J. Alloy. Comp. 560 (2013) 92e104. [14] Y. Yang, Y.F. Cheng, Fabrication of NieCoeSiC composite coatings by pulse electrodeposition d effects of duty cycle and pulse frequency, Surf. Coat. Technol. 216 (2013) 282e288. [15] Y. Yang, Y.F. Cheng, Electrolytic deposition of NieCoeSiC nano-coating for erosion-enhanced corrosion of carbon steel pipes in oilsand slurry, Surf. Coat. Technol. 205 (2011) 3198e3204. [16] A. Hefnawy, N. Elkhoshkhany, A. Essam, NieTiN and NieCoeTiN composite coatings for corrosion protection: fabrication and electrochemical characterization, J. Alloy. Comp. 735 (2018) 600e606. [17] G.-f. Wang, S.-s. Jiang, Z. Lu, K.-f. Zhang, Preparation and tensile properties of Al2O3/Ni-Co nanocomposites, Trans. Nonferrous Metals Soc. China 21 (2011) s374es379. [18] B. Ranjith, G. Paruthimal Kalaignan, NieCoeTiO2 nanocomposite coating prepared by pulse and pulse reversal methods using acetate bath, Appl. Surf. Sci. 257 (2010) 42e47. [19] Y. Wang, Z. Xu, Nanostructured NieWCeCo composite coatings fabricated by electrophoretic deposition, Surf. Coat. Technol. 200 (2006) 3896e3902. [20] B. Bakhit, The influence of electrolyte composition on the properties of NieCo alloy coatings reinforced by SiC nano-particles, Surf. Coat. Technol. 275 (2015) 324e331. [21] L.M. Chang, M.Z. An, H.F. Guo, S.Y. Shi, Microstructure and properties of Ni-Co/ nano-Al2O3 composite coatings by pulse reversal current electrodeposition, Appl. Surf. Sci. 253 (2006) 2132e2137. [22] L.M. Chang, H.F. Guo, M.Z. An, Electrodeposition of Ni-Co/Al2O3 composite coating by pulse reverse method under ultrasonic condition, Mater. Lett. 62 (2008) 3313e3315. [23] Y. Wang, S.L. Tay, S. Wei, C. Xiong, W. Gao, R.A. Shakoor, R. Kahraman, Microstructure and properties of sol-enhanced Ni-Co-TiO2 nano-composite coatings on mild steel, J. Alloy. Comp. 649 (2015) 222e228. [24] H. Luo, X. Wang, S. Gao, C. Dong, X. Li, Synthesis of a duplex NiePeYSZ/NieP nanocomposite coating and investigation of its performance, Surf. Coat. Technol. 311 (2017) 70e79. [25] B. Ma, Y. Li, J. Zhao, X. Li, W. Xin, Novel structural functional films based on self-assembly template and electrodeposition: synthesis and characterization of porous Ni/YSZ films, Thin Solid Films 517 (2009) 5172e5175. [26] M. Zarabian, A.Y. Yar, S. Vafaeenezhad, M.A.F. Sani, A. Simchi, Electrophoretic deposition of functionally-graded NiOeYSZ composite films, J. Eur. Ceram. Soc. 33 (2013) 1815e1823. [27] J.K. Pancrecious, J.P. Deepa, V. Jayan, U.S. Bill, T.P.D. Rajan, B.C. Pai, Nanoceria induced grain refinement in electroless Ni-B-CeO2 composite coating for enhanced wear and corrosion resistance of Aluminium alloy, Surf. Coat. Technol. 356 (2018) 29e37. [28] Z. Qu, X. Cheng, J. Wu, R. He, Y. Pei, D. Fang, An investigation on erosion behavior of nanostructured 7YSZ coatings at elevated temperature, Surf. Coat. Technol. 299 (2016) 129e134. [29] E. Beltowska-Lehman, P. Indyka, A. Bigos, M.J. Szczerba, M. Kot, NieW/ZrO2 nanocomposites obtained by ultrasonic DC electrodeposition, Mater. Des. 80 (2015) 1e11. [30] E.A. Pavlatou, M. Stroumbouli, P. Gyftou, N. Spyrellis, Hardening effect induced by incorporation of SiC particles in nickel electrodeposits, J. Appl. Electrochem. 36 (2005) 385e394. [31] I. Tudela, Y. Zhang, M. Pal, I. Kerr, A.J. Cobley, Ultrasound-assisted electrodeposition of thin nickel-based composite coatings with lubricant particles, Surf. Coat. Technol. 276 (2015) 89e105. [32] Z. Wang, L. Shen, W. Jiang, M. Fan, D. Liu, J. Zhao, Superhydrophobic nickel coatings fabricated by scanning electrodeposition on stainless steel formed by selective laser melting, Surf. Coat. Technol. 377 (2019) 124886. [33] A. Mukhopadhyay, T.K. Barman, P. Sahoo, Friction and wear performance of electroless Ni-B coatings at different operating temperatures, Silicon 11 (2018) 721e731. [34] N. Guglielmi, Kinetics of the deposition of inert particles from electrolytic baths, J. Electrochem. Soc. 119 (1972). [35] J. Winiarski, B. Cieslikowska, W. Tylus, P. Kunicki, B. Szczygieł, Corrosion of nanocrystalline nickel coatings electrodeposited from choline chloride: ethylene glycol deep eutectic solvent exposed in 0.05 M NaCl solution, Appl. Surf. Sci. 470 (2019) 331e339. [36] T. He, Y. He, H. Li, Z. Su, Y. Fan, Z. He, Fabrication of Ni-W-B4C composite coatings and evaluation of its micro-hardness and corrosion resistance properties, Ceram. Int. 44 (2018) 9188e9193.
Please cite this article as: B. Li, W. Zhang, Synthesis of NieCoeZrO2 nanocomposites doped with ceria particles via electrodeposition as highly protective coating, Journal of Alloys and Compounds, https://doi.org/10.1016/j.jallcom.2019.153158