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A facile and gentle method to fabricate amorphous WO3 coatings with superamphiphobic character study
Accepted Manuscript A facile and gentle method to fabricate amorphous WO3 coatings with superamphiphobic character study Yinan Fan, Hongtao Liu, Bingbing Xia, Wei Zhu, Kaijin Guo, Jiande Li PII: DOI: Reference:
S0167-577X(17)30094-0 http://dx.doi.org/10.1016/j.matlet.2017.01.081 MLBLUE 22034
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
15 December 2016 18 January 2017 19 January 2017
Please cite this article as: Y. Fan, H. Liu, B. Xia, W. Zhu, K. Guo, J. Li, A facile and gentle method to fabricate amorphous WO3 coatings with superamphiphobic character study, Materials Letters (2017), doi: http://dx.doi.org/ 10.1016/j.matlet.2017.01.081
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1 A facile and gentle method to fabricate amorphous WO3 coatings with superamphiphobic character study Yinan Fan, Hongtao Liu*, Bingbing Xia, Wei Zhu, Kaijin Guo, Jiande Li [*] Prof. H. Liu, College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116; China. E-mail: [email protected] Kaijin Guo, Xuzhou medical college affiliated hospital. Jiangde Li, National Center of Quality Supervision & Inspection on Deep Processing Silicon Products. Abstract The amorphous WO3 coatings are prepared by a simple chemical deposition at room temperature. And the coatings modified with FAS-17 could obtain superamphiphobicity. The chemical composition, surface morphology, surface groups were respectively investigated with XRD, XPS, SEM, FT-IR and contact angles measurement. In order to study the particles’ size, the TEM pictures is applied. The wettability of the coatings were characterized by contact angles and surface adhesion abilities. Results show that the coatings were composed of amorphous micro-nano WO3 at 60 ℃ ， and those coatings could be easily fabricated and obtain superamphiphobicity. In meanwhile, the coatings possessed of low adhesion and high contact angles to water and oil. Keywords: Deposition; Superamphiphobicity; Amorphous WO3; XPS; FTIR
1. Introduction Inspired by the superhydrophobic surface of a lotus leaf [1,2], superhydrophobic surfaces with large water contact angle ( ≥150 °) have attracted great attention owing to its potential applications in oil/water separation [3,4], anti-icing [5,6], self-cleaning [7], anti-corrosion [8], smart-response [9,10]. Many researches have showed that superhydrophobic surfaces were fabricated through two approach: one is creating a micro-nanostructures rough surface on low surface energy materials; another is modifying low surface energy materials on micro-nanostructures rough surface [11-13]. So far, various methods have been used to prepare superhydrophobic surface such as sol-gel [14], chemical vapor deposition [15], laser etching [16], electrochemistry method [17], etc. However, many of methods usually have inevitable disadvantages, including difficult process controls and the special equipment, etc. On the basis of previous study, the WO3 coatings usually were prepared by powder spraying, plasma electrolytic oxidation (PEO) process, vacuum-evaporation technique and so on. It is very difficult to fabricate WO3 coating though chemical deposition and few reports about it. At the same time, the superamphiphobic amorphous WO3 coatings have not been reported in recently years. In this paper, we used a simple method to fabricate amorphous WO3 coatings on Q235steel and obtain superamphiphobicity though modified by FAS-17.
2 2. Experimental section 2.1. Preparation of amorphous WO3 coatings 50mm×50mm Q235 steel were polished using 200# and 500# sandpaper successively, then, cleaned with ethanol and quickly dried by a blower, then activated by 10% sulfuric acid for 30min. The amonium sulfate(30g), sodium citrate(40g) and sodium tungstate(40g) were added to amount of distilled water(1L) stirred at room temperature for 2hours(ASSW). Then, the hydrochloric acid (30ml), hydrogen peroxide (5ml) and hydrazine hydrate (8ml) was added into the ASSW(200ml) and stirred for 10 min. Finally, the Q235 steel was immersed into the prepared mixture for 20 min at room temperature(about 20℃), dried with a blower and placed in the drying box maintained at 60 °C for 2 hours. In order to obtain superamphiphobic surface on the Q235 steel, the samples were immersed into a beaker containing 200 mL of 0.02 mol/L FAS-17 at 60℃ for 1 h. 2.2. Measurement of amorphous WO3 coatings The surface morphology was characterized by a ZEISS ΣIGMA scanning electron microscopy, X-ray diffraction pattern was recorded crystal structure, using Germany*/D8 ADVANCE and X-ray photoelectron spectroscopy (XPS, USA*/ESCALAB 250Xi). The surface chemical compositions were investigated using a Fourier-transform infrared spectrophotometer (FT-IR, Nicolette 6700/USA). The average CA and SA values were measured by a contact angle meter (China /OCA20) at five different positions with 5 µL (CA) and 8µL (SA) liquids of water, glycerol, rapeseed oil and engine oil, respectively.
3. Results and discussion 3.1. The characterization and analysis of WO3 coatings Fig.1 shows the XRD patterns and XPS spectra of the WO3 coatings annealed at different temperatures of 60℃, 300℃,600℃. As Fig.1a can be seen, the XRD patterns show broad peaks at 300℃ and 60℃, the coatings’ ingredient is composed of amorphous materials. However, the XRD pattern of 300℃ is wider than the XRD pattern of 60℃. It means that the coatings’ structures begin to change at high temperature, but the coatings maintain non-crystalline structure. Those coatings possessed higher crystal transition temperature than 300℃. When the annealing temperature increased to 600℃, the WO3 coatings transformed amorphous into crystalline structures(as shown in Fig.1a). The strong diffraction peaks near the diffraction angles of 23° correspond to the diffractions of WO3 crystal face (002), (020), (200) and (120) respectively [18], which can be proved that the material is WO3. Additional, almost all the diffraction peaks could be perfectly indexed to the WO3 (JCPDS 43-1003). Considering the lack of the persuasion being characterizated with XRD, especially with the non-crystalline structure, the XPS of accuracy is satisfactory the requirements. Through Gaussian deconvolution W4 f spectra of coatings could be well resolved into W4 f7/2 and W4f5/2 doublet caused by spin-orbit coupling with binding energy of 35.5 and 37.6 eV, which corresponded to a typical +6 state of W [Fig. 1b and 1c]. At the same time, the binding energy of 35.5 and 37.6 eV
3 have been illustrated by Mu Sun [19]. Hence, the films are composited of amorphous WO3 when the temperature was below 300℃. So, those results showed that the coatings (annealed at 60℃) were composed of WO3.
Fig. 1.a: XRD patterns of WO3 films at different temperatures; b: XPS spectra of WO3 coating at 60℃; c: XPS spectra of WO3 coating at 300℃ for 4 hours. d: XPS spectra of WO 3 coating at 600℃ for 4 hours.
The formation of WO3 micro-nanostructures on Q235 steel substrates was accomplished through chemical reactions (as shown in Fig.3a), which can formation of WO3 micro-nanostructures on Q235 steel. Chemical reaction is followed. In eqs1and 2, acidification of the tungsten acid sodium will generate tungstate acid, and the ligand between hydrogen peroxide and tungsten acid forms tungsten acid peroxide. First, WO3 was reduced instantly and attached on Q235 steel substrates from the reaction solution. Then, WO3 start nucleation and quickly grew, then became graininess and simultaneously extended to the whole surface, finally form islands-like structure. Meanwhile, many small bubbles were produced and formation of the gaps between the islands according to eqs3. At the end, all islands connected together to form uneven and serried WO3 micro-nanostructures (as shown in Fig.2a). Na2 WO4+2HCL →H2 WO4+2NaCL (1) H2O2+ H2WO4→H2 WO5+H2O (2) 2+ + Fe +N2H4+ H2 WO5→N2+ Fe + WO3+ 2H2 O+2H (3) The surface morphologies of superamphiphobic WO3 coatings on Q235 steel were characterized
4 by SEM. Fig. 2a shows the SEM image of WO3 layer is consists of many gathered particles, whose dimension and diameter are about 100-300 nm. There are numerous embossments and holes owing to quantities of particles randomly covered on the surface. The inset from image (Fig. 2b) exhibits that the surface has many smaller structures, those structures maybe is key to obtain superamphiphobicity. In some certain, TEM allows one to detect a particle’s sizes precisely [20-23]. In order to further study, The TEM was presented in Fig.2c and Fig.2d. Fig.2c presents that the particle is about 200nm, the insert picture of Fig.2c is dark, this result shows the particle is amorphous phase. And it accords with the sample at 60℃ and the XRD test. However, the sample at 600℃ present obvious crystal faces, which are alternate permutation(as shown in Fig2d ), those feature could be easily found from the inserted picture of Fig.2d. the TEM pictures also show the interplanar spacing is 0.376nm and 0.342nm, they respectively corresponds to the XRD peaks’ (020) and (120). These results also illustrated the amorphous phase at 60℃ could become crystals at 600℃, further showed that the rough structure of coatings is consisted of smaller particles.
Fig. 2. a, b: SEM images of WO3 coating with different magnifications. c:TEM picture of WO3 films at 60℃; d: TEM picture of WO3 films at 600℃.
3.2. Wettability Analysis of the amorphous WO3 coatings The wetting of superamphiphobic surface could be attributed to three factors: coarse structure [24], air cavities and low energy surface [25]. The surface functional group were determined by FT-IR. In common, the appearance of peaks belonging to -CF2- and -CF3 functional groups arising
5 from C-F stretching vibration are evident between wavenumbers of 1120 and 1350 cm-1 wavenumbers [26]. These results indicate that the prepared superoleophobic or superhydrophobicWO3 surfaces had been covered by the FAS-17 film (as shown in Fig .3b). Superhydrophobicity is usually explained by the Cassie-Baxter model according to the fact that a rough hydrophobic surface (as shown in Fig.3c). As can be seen from the round-likely roundness (as shown in Fig.2), the highly rough surface is mainly composed of small particles. At the same time, a large number of air was stored between small holes due to its micro-nano structure, making the water and oil droplets could stand on the coatings and nearly keep sphere. Therefore, the droplets will not expand and maintain its sphere shape (as shown in Fig 3d). Fig.3e, 3f, 3g and 3h show the different liquids’ contact angles on superamphiphobic WO3 surface, the different liquids’ contact angles are 161°, 158°，154° and 153° , respectively. And the droplets could easily slide from the surface.
Fig. 3. a: The scheme of fabricating WO 3 coatings; b: FT-IR of survey spectrum; c: the model of Cassie-Baxter d: the droplets on the WO3 coating; e，f，g，h: droplets’ contact angle and sliding angle.
For further study of wettability evaluation, Figure 4 shows the process of approach, contact, extrusion deformation, and departure of water (a-e) glycerol (a1-e1) rapeseed oil (a2-e2) and engine oil (a1-e3) droplets respect to the WO3 coatings. It can be seen that the water/glycerol/cooking oil droplets can completely depart from the superamphiphobic surface
6 without any remaining. This indicates that the prepared surface with low adhesion to different liquid.
Fig. 4. Approach, contact, extrusion deformation, and departure of droplet process of water(a-e)/glycerol(a1-e1)/rapeseed oil (a2-e2)/engine oil (a3-e3) on the superamphiphobicWO3 coating. The arrows show the moving direction of the droplet.
4. Conclusions In this study, a facile and gentle method to fabricating amorphous WO3 coatings was studied. And the superamphiphobic armorphous WO3 coatings were found through modified by low energy material, the coatings are superamphiphobic with CAs all surpass 150° and low adhesion to water/oil droplets. In meanwhile, compared with other methods for preparing WO3 coatings, this method has the advantages of simple operation, low cost. It is believed that the coatings with excellent superamphiphobicity may open a novel approach to expand the applications of alloys. Acknowledgment This work was supported by the National Nature Science Foundation of China (No.51475457) and Qing Lan Project and the Key Program of Science and Technique Development Foundation in Jiangsu Province（BE2015627).
References [1] Y.B. Zhou, Y. Yang, W.M. Liu, Q. Ye, B. He, Y.S. Zou, P.F. Wang, X.J. Pan, W.J. Zhang, I. Bello, Appl Phys Lett 97 (2010) 133110. [2] K. Liu, Z. Li, W. Wang, L. Jiang, Appl Phys Lett 99 (2011) 261905. [3] J. Gu, P. Xiao, J. Chen, F. Liu, Y. Huang, G. Li, J. Zhang, T. Chen, J.mater.chem.a 2 (2014) 15268. [4] Y. Cao, X. Zhang, T. Lei, L. Kan, Z. Xue, F. Lin, Y. Wei, Acs Appl Mater Inter 5 (2013) 4438. [5] S.A. Kulinich, S. Farhadi, K. Nose, X.W. Du, Langmuir 27 (2011) 25. [6] Y.H. Yeong, A. Steele, E. Loth, I. Bayer, G. De Combarieu, C. Lakeman, Appl Phys Lett 100 (2012) 053112. [7] A. Nakajima, T. Watanabe, K. Takai, G. Yamauchi, A. Fujishima, K. Hashimoto, Langmuir 16 (2000) 7044. [8] T. Liu, Y. Yin, S. Chen, X. Chang, S. Cheng, Electrochimica Acta 52 (2007) 3709.
7 [9] C. Jiang, Q. Wang, T. Wang, New J Chem 37 (2013) 810. [10] W. Sun, S. Zhou, B. You, L. Wu, New J Chem 1 (2013) 3146. [11] Y. Lu, S. Sathasivam, J. Song, F. Chen, W. Xu, C. Carmalt, I. Parkin, J.mater.chem.a 2 (2014). [12] X. Zhou, Z. Zhang, X. Xu, F. Guo, X. Zhu, X. Men, B. Ge, Acs Appl Mater Inter 5 (2013) 7208. [13] Q. An, Y. Zhang, K. Lv, X. Luan, Q. Zhang, F. Shi, Nanoscale 7 (2015) 4553. [14] X. Huang, Y. Sun, S. Soh, Adv Mater 27 (2015). [15] X. Song, J. Zhai, Y. Wang, L. Jiang, J Colloid Intere Sci 298 (2006) 267. [16] L. Li, V. Breedveld, D.W. Hess, Acs Appl Mater Inter 4 (2012) 4549. [17] C.H. Wang, Y.Y. Song, J.W. Zhao, X.H. Xia, Surf Sci 600 (2006) 38. [18] Y. Ren, Y. Gao, G. Zhao, Ceram Int 41 (2015) 403. [19] L. Zhang, Z. Zhou, B. Cheng, J.M. Desimone, E.T. Samulski, Langmuir 22 (2006) 8576. [20] B.B. Straumal, A.A. Mazilkin, S.G. Protasova, S.V. Stakhanova, P.B. Straumal, M.F. Bulatov, G. Schütz, T. Tietze, E. Goering, B. Baretzky, Reviews on Advanced Materials Science 41 (2015) 61. [21] B.B. Straumal, A.A. Mazilkin, Journal of Materials Engineering and Performance 25 (2016) 1. [22] B.B. Straumal, A.A. Mazilkin, S.G. Protasova, P.B. Straumal, A.A. Myatiev, G. Schütz, E.J. Goering, T. Tietze, B. Baretzky, Philosophical Magazine 93 (2013) 1371. [23] B.B. Straumal, S.G. Protasova, A.A. Mazilkin, E. Goering, G. Schütz, P.B. Straumal, B. Baretzky, 7 (2016) 1936. [24] T. Chen, S. Ge, H. Liu, Q. Sun, W. Zhu, W. Yan, J. Qi, Applied Surface Science 356 (2015) 81. [25] Y. Su, B. Ji, Y. Huang, K.C. Hwang, Langmuir 26 (2010) 18926. [26] A. Hozumi, O. Takai, Appl Surf Sci 103 (1996) 431.
8 Highlights： 1. The process of fabricating of amorphous WO3 coatings’ methods is very facile and gentle method. 2. The coatings modified by FAS-17 could obtain superamphiphobicity. 3. The modified coatings with low adhesion force to oil and water.
Yinan Fan, Hongtao Liu*, Bingbing Xia, Wei Zhu College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116; China Kaijin Guo - Xuzhou medical college affiliated hospital Xuzhou, Jiangsu 221116; China Jiande Li - National Center of Quality Supervision & Inspection on Deep Processing Silicon Products, Lianyungang, 222300, China
Yinan Fan, Hongtao Liu*, Bingbing Xia, Wei Zhu College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116; China Kaijin Guo - Xuzhou medical college affiliated hospital Xuzhou, Jiangsu 221116; China Jiande Li - National Center of Quality Supervision & Inspection on Deep Processing Silicon Products, Lianyungang, 222300, China
S0167-577X(17)30094-0 http://dx.doi.org/10.1016/j.matlet.2017.01.081 MLBLUE 22034
To appear in:
Materials Letters
Received Date: Revised Date: Accepted Date:
15 December 2016 18 January 2017 19 January 2017
Please cite this article as: Y. Fan, H. Liu, B. Xia, W. Zhu, K. Guo, J. Li, A facile and gentle method to fabricate amorphous WO3 coatings with superamphiphobic character study, Materials Letters (2017), doi: http://dx.doi.org/ 10.1016/j.matlet.2017.01.081
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
1 A facile and gentle method to fabricate amorphous WO3 coatings with superamphiphobic character study Yinan Fan, Hongtao Liu*, Bingbing Xia, Wei Zhu, Kaijin Guo, Jiande Li [*] Prof. H. Liu, College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116; China. E-mail: [email protected] Kaijin Guo, Xuzhou medical college affiliated hospital. Jiangde Li, National Center of Quality Supervision & Inspection on Deep Processing Silicon Products. Abstract The amorphous WO3 coatings are prepared by a simple chemical deposition at room temperature. And the coatings modified with FAS-17 could obtain superamphiphobicity. The chemical composition, surface morphology, surface groups were respectively investigated with XRD, XPS, SEM, FT-IR and contact angles measurement. In order to study the particles’ size, the TEM pictures is applied. The wettability of the coatings were characterized by contact angles and surface adhesion abilities. Results show that the coatings were composed of amorphous micro-nano WO3 at 60 ℃ ， and those coatings could be easily fabricated and obtain superamphiphobicity. In meanwhile, the coatings possessed of low adhesion and high contact angles to water and oil. Keywords: Deposition; Superamphiphobicity; Amorphous WO3; XPS; FTIR
1. Introduction Inspired by the superhydrophobic surface of a lotus leaf [1,2], superhydrophobic surfaces with large water contact angle ( ≥150 °) have attracted great attention owing to its potential applications in oil/water separation [3,4], anti-icing [5,6], self-cleaning [7], anti-corrosion [8], smart-response [9,10]. Many researches have showed that superhydrophobic surfaces were fabricated through two approach: one is creating a micro-nanostructures rough surface on low surface energy materials; another is modifying low surface energy materials on micro-nanostructures rough surface [11-13]. So far, various methods have been used to prepare superhydrophobic surface such as sol-gel [14], chemical vapor deposition [15], laser etching [16], electrochemistry method [17], etc. However, many of methods usually have inevitable disadvantages, including difficult process controls and the special equipment, etc. On the basis of previous study, the WO3 coatings usually were prepared by powder spraying, plasma electrolytic oxidation (PEO) process, vacuum-evaporation technique and so on. It is very difficult to fabricate WO3 coating though chemical deposition and few reports about it. At the same time, the superamphiphobic amorphous WO3 coatings have not been reported in recently years. In this paper, we used a simple method to fabricate amorphous WO3 coatings on Q235steel and obtain superamphiphobicity though modified by FAS-17.
2 2. Experimental section 2.1. Preparation of amorphous WO3 coatings 50mm×50mm Q235 steel were polished using 200# and 500# sandpaper successively, then, cleaned with ethanol and quickly dried by a blower, then activated by 10% sulfuric acid for 30min. The amonium sulfate(30g), sodium citrate(40g) and sodium tungstate(40g) were added to amount of distilled water(1L) stirred at room temperature for 2hours(ASSW). Then, the hydrochloric acid (30ml), hydrogen peroxide (5ml) and hydrazine hydrate (8ml) was added into the ASSW(200ml) and stirred for 10 min. Finally, the Q235 steel was immersed into the prepared mixture for 20 min at room temperature(about 20℃), dried with a blower and placed in the drying box maintained at 60 °C for 2 hours. In order to obtain superamphiphobic surface on the Q235 steel, the samples were immersed into a beaker containing 200 mL of 0.02 mol/L FAS-17 at 60℃ for 1 h. 2.2. Measurement of amorphous WO3 coatings The surface morphology was characterized by a ZEISS ΣIGMA scanning electron microscopy, X-ray diffraction pattern was recorded crystal structure, using Germany*/D8 ADVANCE and X-ray photoelectron spectroscopy (XPS, USA*/ESCALAB 250Xi). The surface chemical compositions were investigated using a Fourier-transform infrared spectrophotometer (FT-IR, Nicolette 6700/USA). The average CA and SA values were measured by a contact angle meter (China /OCA20) at five different positions with 5 µL (CA) and 8µL (SA) liquids of water, glycerol, rapeseed oil and engine oil, respectively.
3. Results and discussion 3.1. The characterization and analysis of WO3 coatings Fig.1 shows the XRD patterns and XPS spectra of the WO3 coatings annealed at different temperatures of 60℃, 300℃,600℃. As Fig.1a can be seen, the XRD patterns show broad peaks at 300℃ and 60℃, the coatings’ ingredient is composed of amorphous materials. However, the XRD pattern of 300℃ is wider than the XRD pattern of 60℃. It means that the coatings’ structures begin to change at high temperature, but the coatings maintain non-crystalline structure. Those coatings possessed higher crystal transition temperature than 300℃. When the annealing temperature increased to 600℃, the WO3 coatings transformed amorphous into crystalline structures(as shown in Fig.1a). The strong diffraction peaks near the diffraction angles of 23° correspond to the diffractions of WO3 crystal face (002), (020), (200) and (120) respectively [18], which can be proved that the material is WO3. Additional, almost all the diffraction peaks could be perfectly indexed to the WO3 (JCPDS 43-1003). Considering the lack of the persuasion being characterizated with XRD, especially with the non-crystalline structure, the XPS of accuracy is satisfactory the requirements. Through Gaussian deconvolution W4 f spectra of coatings could be well resolved into W4 f7/2 and W4f5/2 doublet caused by spin-orbit coupling with binding energy of 35.5 and 37.6 eV, which corresponded to a typical +6 state of W [Fig. 1b and 1c]. At the same time, the binding energy of 35.5 and 37.6 eV
3 have been illustrated by Mu Sun [19]. Hence, the films are composited of amorphous WO3 when the temperature was below 300℃. So, those results showed that the coatings (annealed at 60℃) were composed of WO3.
Fig. 1.a: XRD patterns of WO3 films at different temperatures; b: XPS spectra of WO3 coating at 60℃; c: XPS spectra of WO3 coating at 300℃ for 4 hours. d: XPS spectra of WO 3 coating at 600℃ for 4 hours.
The formation of WO3 micro-nanostructures on Q235 steel substrates was accomplished through chemical reactions (as shown in Fig.3a), which can formation of WO3 micro-nanostructures on Q235 steel. Chemical reaction is followed. In eqs1and 2, acidification of the tungsten acid sodium will generate tungstate acid, and the ligand between hydrogen peroxide and tungsten acid forms tungsten acid peroxide. First, WO3 was reduced instantly and attached on Q235 steel substrates from the reaction solution. Then, WO3 start nucleation and quickly grew, then became graininess and simultaneously extended to the whole surface, finally form islands-like structure. Meanwhile, many small bubbles were produced and formation of the gaps between the islands according to eqs3. At the end, all islands connected together to form uneven and serried WO3 micro-nanostructures (as shown in Fig.2a). Na2 WO4+2HCL →H2 WO4+2NaCL (1) H2O2+ H2WO4→H2 WO5+H2O (2) 2+ + Fe +N2H4+ H2 WO5→N2+ Fe + WO3+ 2H2 O+2H (3) The surface morphologies of superamphiphobic WO3 coatings on Q235 steel were characterized
4 by SEM. Fig. 2a shows the SEM image of WO3 layer is consists of many gathered particles, whose dimension and diameter are about 100-300 nm. There are numerous embossments and holes owing to quantities of particles randomly covered on the surface. The inset from image (Fig. 2b) exhibits that the surface has many smaller structures, those structures maybe is key to obtain superamphiphobicity. In some certain, TEM allows one to detect a particle’s sizes precisely [20-23]. In order to further study, The TEM was presented in Fig.2c and Fig.2d. Fig.2c presents that the particle is about 200nm, the insert picture of Fig.2c is dark, this result shows the particle is amorphous phase. And it accords with the sample at 60℃ and the XRD test. However, the sample at 600℃ present obvious crystal faces, which are alternate permutation(as shown in Fig2d ), those feature could be easily found from the inserted picture of Fig.2d. the TEM pictures also show the interplanar spacing is 0.376nm and 0.342nm, they respectively corresponds to the XRD peaks’ (020) and (120). These results also illustrated the amorphous phase at 60℃ could become crystals at 600℃, further showed that the rough structure of coatings is consisted of smaller particles.
Fig. 2. a, b: SEM images of WO3 coating with different magnifications. c:TEM picture of WO3 films at 60℃; d: TEM picture of WO3 films at 600℃.
3.2. Wettability Analysis of the amorphous WO3 coatings The wetting of superamphiphobic surface could be attributed to three factors: coarse structure [24], air cavities and low energy surface [25]. The surface functional group were determined by FT-IR. In common, the appearance of peaks belonging to -CF2- and -CF3 functional groups arising
5 from C-F stretching vibration are evident between wavenumbers of 1120 and 1350 cm-1 wavenumbers [26]. These results indicate that the prepared superoleophobic or superhydrophobicWO3 surfaces had been covered by the FAS-17 film (as shown in Fig .3b). Superhydrophobicity is usually explained by the Cassie-Baxter model according to the fact that a rough hydrophobic surface (as shown in Fig.3c). As can be seen from the round-likely roundness (as shown in Fig.2), the highly rough surface is mainly composed of small particles. At the same time, a large number of air was stored between small holes due to its micro-nano structure, making the water and oil droplets could stand on the coatings and nearly keep sphere. Therefore, the droplets will not expand and maintain its sphere shape (as shown in Fig 3d). Fig.3e, 3f, 3g and 3h show the different liquids’ contact angles on superamphiphobic WO3 surface, the different liquids’ contact angles are 161°, 158°，154° and 153° , respectively. And the droplets could easily slide from the surface.
Fig. 3. a: The scheme of fabricating WO 3 coatings; b: FT-IR of survey spectrum; c: the model of Cassie-Baxter d: the droplets on the WO3 coating; e，f，g，h: droplets’ contact angle and sliding angle.
For further study of wettability evaluation, Figure 4 shows the process of approach, contact, extrusion deformation, and departure of water (a-e) glycerol (a1-e1) rapeseed oil (a2-e2) and engine oil (a1-e3) droplets respect to the WO3 coatings. It can be seen that the water/glycerol/cooking oil droplets can completely depart from the superamphiphobic surface
6 without any remaining. This indicates that the prepared surface with low adhesion to different liquid.
Fig. 4. Approach, contact, extrusion deformation, and departure of droplet process of water(a-e)/glycerol(a1-e1)/rapeseed oil (a2-e2)/engine oil (a3-e3) on the superamphiphobicWO3 coating. The arrows show the moving direction of the droplet.
4. Conclusions In this study, a facile and gentle method to fabricating amorphous WO3 coatings was studied. And the superamphiphobic armorphous WO3 coatings were found through modified by low energy material, the coatings are superamphiphobic with CAs all surpass 150° and low adhesion to water/oil droplets. In meanwhile, compared with other methods for preparing WO3 coatings, this method has the advantages of simple operation, low cost. It is believed that the coatings with excellent superamphiphobicity may open a novel approach to expand the applications of alloys. Acknowledgment This work was supported by the National Nature Science Foundation of China (No.51475457) and Qing Lan Project and the Key Program of Science and Technique Development Foundation in Jiangsu Province（BE2015627).
References [1] Y.B. Zhou, Y. Yang, W.M. Liu, Q. Ye, B. He, Y.S. Zou, P.F. Wang, X.J. Pan, W.J. Zhang, I. Bello, Appl Phys Lett 97 (2010) 133110. [2] K. Liu, Z. Li, W. Wang, L. Jiang, Appl Phys Lett 99 (2011) 261905. [3] J. Gu, P. Xiao, J. Chen, F. Liu, Y. Huang, G. Li, J. Zhang, T. Chen, J.mater.chem.a 2 (2014) 15268. [4] Y. Cao, X. Zhang, T. Lei, L. Kan, Z. Xue, F. Lin, Y. Wei, Acs Appl Mater Inter 5 (2013) 4438. [5] S.A. Kulinich, S. Farhadi, K. Nose, X.W. Du, Langmuir 27 (2011) 25. [6] Y.H. Yeong, A. Steele, E. Loth, I. Bayer, G. De Combarieu, C. Lakeman, Appl Phys Lett 100 (2012) 053112. [7] A. Nakajima, T. Watanabe, K. Takai, G. Yamauchi, A. Fujishima, K. Hashimoto, Langmuir 16 (2000) 7044. [8] T. Liu, Y. Yin, S. Chen, X. Chang, S. Cheng, Electrochimica Acta 52 (2007) 3709.
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8 Highlights： 1. The process of fabricating of amorphous WO3 coatings’ methods is very facile and gentle method. 2. The coatings modified by FAS-17 could obtain superamphiphobicity. 3. The modified coatings with low adhesion force to oil and water.
Yinan Fan, Hongtao Liu*, Bingbing Xia, Wei Zhu College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116; China Kaijin Guo - Xuzhou medical college affiliated hospital Xuzhou, Jiangsu 221116; China Jiande Li - National Center of Quality Supervision & Inspection on Deep Processing Silicon Products, Lianyungang, 222300, China
Yinan Fan, Hongtao Liu*, Bingbing Xia, Wei Zhu College of Materials Science and Engineering, China University of Mining and Technology, Xuzhou, Jiangsu 221116; China Kaijin Guo - Xuzhou medical college affiliated hospital Xuzhou, Jiangsu 221116; China Jiande Li - National Center of Quality Supervision & Inspection on Deep Processing Silicon Products, Lianyungang, 222300, China