Translate this page into:
Improved adhesion of superhydrophobic layer on metal surfaces via one step spraying method
⁎Corresponding author at: Materials Science Department, Institute of Graduate Studies and Research, Alexandria University, 163, Horreya Av., El-Shatby 21526, P.O. Box: 832, Alexandria, Egypt. Tel.: +20 1223829252. Wael200374@yahoo.com (Wael I. El Dessouky),
-
Received: ,
Accepted: ,
This article was originally published by Elsevier and was migrated to Scientific Scholar after the change of Publisher.
Abstract
Superhydrophobic metal substrates have been fabricated by a simple spraying method. The processes of decreasing surface free energy and increasing surface roughness have been accomplished in one step via the addition of functionalized silica (silica nano particles with octyltriethoxysilane) to adhesive polymer. The method is simple, cost-effective and can be applied on the large industrial scale. Scanning electron microscopy (SEM) was used for surface morphology analysis, showing the roughness produced by surface treatment. The wettability of the micro-nano silica film varied from hydrophilicity (water contact angle 88°) to superhydrophobicity (water contact angle 156.9°), while sliding contact angles dramatically decreased (<5°) by adding Functionalized silica and/or adhesive polymer. Roughness increased with silica increment which improves the wettability. The coatings were electrochemically characterized by electrochemical impedance spectroscopy (EIS) and Tafel polarization curves; it was found that both systems had good performance against corrosion in 3.5% sodium chloride solution. Furthermore, the stability of the coated layer on copper substrate was investigated.
Keywords
Superhydrophobicity
Polymer
Corrosion resistance
Adhesion
1 Introduction
Recently the superhydrophobic surfaces with a water contact angle higher than 150° have received much interest, due to their convenience in many fields, Such as self-cleaning, snow inhibition and contamination inhibition (Roach et al., 2008; He et al., 2010; Yao et al., 2011; Sas et al., 2012). These widespread applications have motivated great efforts to improve fabrication techniques of superhydrophobic surface. In recent years, it has been found that, if a surface with a rough or micro textured structure has a low interfacial free energy, the CA can reach almost 180°, and the surface will remain dry as a water droplet easily slides across it. The typical example is the self-cleaning of nature’s lotus leaf, on which the CA is about 161° and the sliding angle (SA) only 2°. So far, many methods have been used for fabricating the superhydrophobic surface (Li et al., 2007; Feng et al., 2003; Lau et al., 2003; Feng and Jiang, 2006). All of these different methods for fabricating the superhydrophobic surfaces are almost based on the two main methods, which are to create the rough structure on the hydrophobic surface and to modify a rough surface by materials with low surface free energy. Therefore, the roughness is crucial for the preparation of the superhydrophobic surface (Miwa et al., 2000). Many methods for obtaining the biomimetic structure, array, irregular pores or particles with micro/nano-size have been applied to fabricate the rough surface (Li et al., 2006; Wang et al., 2006; Ma et al., 2007; Levkin et al., 2009).
It is well known that the wettability of solid surface could be characterized by contact angel (CA) of water droplets. If the CA of a surface is lower than 90°, the surface is described as a hydrophilic surface. In contrast, if that of a surface is higher than 90°, the surface is described as hydrophobic surface for smooth surfaces; CA can be represented by Young’s equation. For rough surfaces, the wetting state can be described by the Wenzel (Wenzel, 1936; Wenzel, 1949) and Cassie–Baxter models (Cassie and Baxter, 1944). The Wenzel model assumes that the liquid is in intimate contact everywhere with the rough surface, and completely fills any surface structures. The roughness factor in the Wenzel equation can enhance the natural state of material, and gives hydrophilic surfaces a lower contact angle and hydrophobic surfaces a larger contact angle. The Cassie–Baxter model introduces another new wetting state, in which the liquid allows very low friction during droplet movement, which introduces a low sliding angle. Both the Cassie–Baxter and Wenzel states can cause high static contact angles, but only the Cassie–Baxter state can lead to very low sliding angle.
Spraying is thought to be one effective technique to create artificial superhydrophobic surfaces due to its simplicity, low-cost and low-temperature method. Hui et al. fabricated superhydrophobic copper meshes by spraying an emulsion of n-octadecanethiol and silver nitrate in ethanol onto the copper mesh with nitrogen gas by a spray gun. The alkanethiols contain long-chain alkyl groups that have low surface free energy. The advantage of this method is that in case of mechanical damage of the surface, it can simply be repaired by partial spraying (Xiang et al., 2011). Other organic materials were used via spraying process such as silica and Functionalized silica. Functionalized silica SiO2 particles not only generated a firm dual size rough surface but also facilitated its further hydrophobization. Most of the widely used organosilanes have one organic substituent and three hydrolyzable substituents. In the vast majority of surface treatment applications, the alkoxy groups of trialkoxysilanes are hydrolyzed to form silanol-containing species. Reaction of these silanes involves four steps. Initially, hydrolysis of the three labile groups occurs. Condensation to oligomers follows. The oligomers then hydrogen bond with OH groups of the substrate. Finally, during drying or curing, a covalent linkage is formed with the substrate with concomitant loss of water. Although described sequentially, these reactions can occur simultaneously after initial hydrolysis step (Arkles, 1977). At the interface, there is usually only one bond between silicon of the organosilanes to the substrate surface. The two remaining silanol groups are present either in condensed or in free form. The R group remains available for covalent reaction or physical interaction with other phases. Many researchers improved superhydrophobic layers but very few researchers improved durability (adhesion) of the superhydrophobic layer.
Many researchers aimed to fabricate superhydrophobic coating with little attention in improving the layer stability and suffer from low durability. In this paper, we reported a polymer functionalized silica film with superhydrophobic properties fabricated by one-step spray casting functionalized silica–polymer (i.e., epoxy, polystyrene, polyurethane, or ethylene vinyl acetate) suspensions with excellent adhesion property. Such a film shows not only highly stable superhydrophobic property with water CA of about 155° and a slide angle (SA) of less than 5° but also has an excellent corrosion resistance in 3.5 wt.% NaCl solution.
2 Experimental
2.1 Materials
Copper alloy, Aluminum alloy and Iron alloy substrates with 3 mm thickness were supplied by The Egyptian Company for Copper Works, Alexandria, Egypt. Silicon dioxide nanopowders (99.5%- 15 nm) were purchased from MKNANO, Canada. Octyltriethoxysilane (OCTES) was purchased from Zhejiang Feidian Chemical Company Ltd., China. Tetrahydrofuran (THF) was purchased from Central Drug House Ltd. Ethylene vinyl acetate (EVA) was purchased from Arkoma. Polystyrene (PS) E251D was purchased from Styrenex Company, Egypt. Epoxy Chemapoxy 150 and Polyurethane (PU) were purchased from Chemicals for Modern Building International Company, Egypt. Ethanol 95% was purchased from Elnasr pharmaceutical Chemical Company, Alexandria, Egypt. All reagents were used as received without further purification.
2.2 Preparation of hierarchical superhydrophobic coatings
All substrate specimens (copper, aluminum and steel) were prepared with dimensions of 60 mm × 25 mm × 0.3 mm. The substrates cleaned by ethanol followed by acetone and dried in air. Functionalized silica (FS) nanoparticles are Silicon dioxide nanopowders treated with silane coupling gents. Three grams of OCTES, with long alkyl chain, was added dropwise to the hydrolysis ratio of ethanol to distilled water (ethanol ETOH:distilled water (DW)) 95:5 after vigorously stirred for approximately 15 min at room temperature. Then, the solution was agitated for 3 h (Lihui et al., 2011; Hengzhen et al., 2012). Different concentrations of silica nanoparticles (i.e., 1, 1.5, 2 and 2.5 wt.%) were prepared by adding 1, 1.5, 2 and 2.5 gm of silica to 100 ml ethanol and DW. Silicon dioxide nanopowders with previous percentage were added to the solution and agitated for extra 3 h. After agitation the solution was kept in closed flask for 2 days at room conditions. Different polymers (i.e., Epoxy, PU, PS or EVA) with specific amounts were added with different samples of the functionalized silica (FS) solutions. The spraying distance was 25 cm then the substrate was held in room temperature for 24 h. The coating solution was sprayed with nitrogen gas by a spray gun nozzle at the spray rate of 5 cm3 per minute during the spray deposition.
2.3 Sample characterization
Water contact angle (WCA) and sliding angle are considered the main values in superhydrophobicity classification. CA measurements were performed using Gaosuo USB digital microscope. All the angles were determined by averaging values measured at five points on different locations on each sample surface. Surface morphology of samples was examined using scanning electron microscope (SEM, JSM-6390A). Samples were coated with a thin layer of gold using a sputtering machine prior to examination with SEM. Surface roughness mathematical value (Ra) was examined using Mituoyo SJ-201. Substrate surface was tested in ten different locations where the average value was supplied as surface roughness. Adhesion improvement between superhydrophobic layer and substrate was studied. The adhesion strength is the influence of the durability of the superhydrophobic layer. Adhesion strength of different prepared superhydrophobic substrates was evaluated using the tape test (ASTM D-3395). Thickness of the superhydrophobic layer was also studied using elcometer-465.
2.4 Electrochemical measurements
The corrosion behavior of the blank copper alloy and different superhydrophobic surfaces was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization in NaCl solution (3.5 wt.%) using electrochemical system (GAMRY PCI4G750 instruments) at room temperature and a typical-three electrode was used in electrochemical testing with reference electrode (saturated calomel electrode), a platinum wire as the counter electrode (auxiliary electrode) and the sample with an exposed area of 1.0 cm2 as the working electrode as demonstrated. EIS was performed in the frequency range between 10 MHz and 100 kHz. Polarization curves (Tafel plots) were acquired at a scanning rate of 1 mV/s from −0.25 to 0.25 V. The corrosion current density (icorr) for the specimens was determined by extrapolating the anodic and cathodic Tafel slopes. All EIS spectra were analyzed in Nyquist representation.
3 Results and discussion
3.1 Surface morphology
Fig. 1 shows SEM images under different Functionalized silica (FS) content sprayed on copper alloy substrates. Fig. 1(a) shows the surface morphology of the film prepared with 1 wt.% FS content in solutions. It is clear that the irregular forms of silica nano particles on substrate surface morphology also clarify the coating layer rough surface. A high-magnification SEM image of the copper surface (Fig. 1b) shows that the particles morphology includes hierarchical micro/nano-structures. Fig. 1(c) demonstrates the coating layer with higher functionalized nano silica of 2.5 wt.% in the sprayed solutions and it shows that the particles become more uniform, smaller, more intensive and connected with each other as the silica percentage increased. And from the higher magnification SEM (Fig. 1b), we can find that these small particles completely cover the surface. It is clear that many irregular clusters randomly distribute on the FS/polymer coating surfaces. These clusters provide the micrometer-scale roughness, while the inclusion of nanoparticles provides the nanoscale roughness on top of the micrometer sized clusters. Such particle organization results in a hierarchical microscale-to-nanoscale roughness, which is known to produce superhydrophobicity on natural and artificial surfaces.
SEM images coated copper surface with FS at different silica concentration (a) 1 wt.%; (b) the corresponding high magnification; (c) 2.5 wt.% and (d) the corresponding high magnification.
Fig. 2 shows SEM images of copper sprayed with coating layer of Functionalized silica with epoxy as adhesive polymer. Fig. 2(a) shows the surface morphology of the film prepared with 1 wt.% FS and 1 wt.% epoxy that increases the bond between FS particles causing silica particles to coagulate with each other. A high-magnification SEM image of the copper surface shows the polymer and the FS particles in position (1) and position (2), respectively (Fig. 2(b)). Increasing polymer 2 wt.% and silica particles 2.5 wt.% shows highly assembled and durable pattern Fig. 2 (c and d). Adhesive polymer formed by bridge-like forms creates strong bond increasing durability and bonding between silica Particals. Fig. 2(e and f) shows same bridge like forms bonding silica particals with polymer.
SEM images coated copper surface by FS with epoxy at different concentration (a) 1 wt.% silica with 1% epoxy, (b) the corresponding high magnification; (c) 2.5 wt.% silica with 2% epoxy; (d) the corresponding high magnification; (e) and (f) high magnification with different positions.
3.2 The wetting behavior of the prepared surface
The surface wettability of the obtained superhydrophobic surface was studied by CA measurements. Fig. 3 displays the profiles of CA of the obtained superhydrophobic surface as function of silica content on FS/polymer. It can be seen from Fig. 3, without any polymer addition at 1 wt.% FS the CA is 155° and increased to 162° at 2.5 wt.%. This result demonstrates that silica achieves high roughness. As is reported, the superhydrophobic property can be achieved by an especial surface chemistry or surface geometrical microstructure (Fürstner et al., 2005). This wettability can be well explained by Wenzel’s equation (Erbil and Elif Cansoy, 2009):
The contact angle as a function of silica percentage (wt.%) with different polymers percentage (wt.%).
The contact angles at optimum silica percentage (2.5 wt.%) with optimum polymer percentage (2 wt.%) using different polymers types at various metals.
3.3 Surface roughness
Surface roughness (Ra) is very important criteria in superhydrophobicity evaluation, where, the hydrophobicity phenomena depend on surface tension and surface roughness. It is obvious that the surface roughness increases the hydrophobicity which directly proportional to the roughness of the coated layer. Fig. 5 depicts the variation of surface roughness of coated copper surfaces with FS. The surface roughness 240 nm on as-received bare copper surface was found to increase to 600 nm, and 1600 nm at low content (1 wt.%) and high content (2.5 wt.%) of FS, respectively. This phenomenon is due to the unique effect of the hierarchical structure of sprayed rough silica on copper surface which is revealed by the SEM images. By introducing the adhesive polymer, the roughness reduces as a result of polymer layer bonding with FS where the polymer layer bond between FS particles fills the vacant gabs between silica particles. The Ra reduces from 600 nm to 400 nm by adding 3 wt.% polymer with 1 wt.% FS, and from 1600 nm to 1076 nm by adding 3 wt.% polymer with 2.5 wt.% FS. The same results were obtained by using other polymers (PS, PU and EVA) on different metal substrates. The optimum silica and polymer content are 2 wt.%. The optimum performance of polymers on the surface roughness of different metals is summarized in Fig. 6.
Variation of surface roughness with silica percentage (wt.%) at different polymer percentages.
Variation of surface roughness at optimum silica percentage (2.5 wt.%) with optimum polymer percentage (2 wt.%) using different polymers types at various metals.
3.4 Layer thickness
Coating thickness was studied using elcometer-465 apparatus, and the average of five different measurements used to determine the change in coating layer thickness with different parameters. According to the data obtained, the layer thicknesses described in Fig. 7 clearly show insignificant difference in thickness between the coatings applied to 1 wt.% and 2 wt.% as 3.91 μm and 4.1 μm, respectively. By adding adhesive polymer increases layer thickness to average of 8 μm for 3 wt.% epoxy with 1 wt.% FS and at high FS/epoxy 3 wt.% and 2.5 wt.% average thickness was 12 μm. It can thus be seen that in fact the concentration of polymer applied was the only factor having a significant effect on final coating thickness, regardless of the type of polymer. Obviously in SEM images the polymer layer formed a thick bottom layer between FS and metal substrates. The different polymers were applied in the same way, using the same proceeding; their chemical composition had comparable specific densities and resin viscosities.
Variation of coating layer thickness with silica percentage at different polymer percentages.
3.5 Corrosion resistance performance
3.5.1 Electrochemical impedance spectroscopy (EIS)
Fig. 8 depicts the Nyquist plots and Bode plots recorded for the bare substrate and resulting superhydrophobic surface in neutral 3.5 wt.% NaCl solutions. Fig. 8a shows the EIS results in the form of Nyquist plots, in which the imaginary impedance (Zim) is plotted against the real impedance (Zre). The results show quite different capacitive loops that can be attributed to the charge transfer resistance of the corrosion process (Rct). Compared with the untreated copper alloy substrate, the capacitive loops of the prepared superhydrophobic surface have a widespread trend attributed to a protective surface film of Si coating. It is well known that the diameter of the capacitive loop related to Rct in the Nyquist plots represents the impedance of the samples. The value of Rct for the superhydrophobic surface (5.05 kΩ) is much larger than that of the untreated substrate surface (0.091 kΩ), which indicates the superhydrophobic film has largely improved the corrosion properties. The same previous data displayed using Bode plot show the relation between the frequency (log f) and the equivalent impedance (log z) shown in Fig. 8b. For better understanding of the mechanisms of the corrosive processes, which occur at the surface of the samples studied, we have applied the fitting of the experimental impedance spectra using the appropriate equivalent electric circuits. The equivalent circuits are shown in Fig. 9 and the fitted parameters are summarized in Table 1. The equivalent circuit representing the electrochemical behavior of the untreated surface shows only one time constant (Fig. 9a). In this circuit, Rct is the charge transfer resistance, Cdl the double layer capacitance, and Rs the solution resistance. In the case of the silica modified superhydrophobic surface, the equivalent circuit model should have two time constants in the corresponding impedance spectra. The Rct||Cdl elements in Fig. 9b showed the impedance with the interface reaction between the silica modified superhydrophobic film and the copper substrate. Cc would normally be assigned to the capacitance of the intact coating (a function of factors such as film thickness and defect structure). Its value is much smaller than a typical double layer capacitance. The resistance Rpo (pore resistance) could be attributed to the resistance of ion conducting paths that develop in the coating (governed mainly by pore dimensions). Additionally, the inhibition efficiency (IE) of the coated modified silica was used to evaluate the corrosion protection performance of superhydrophobic surface, which can be calculated by the following equation (Ma et al., 2003):
where Rct, Rcto are charge transfer resistances of copper alloy covered with and without superhydrophobic coatings, respectively. Inhibition efficiency of superhydrophobic coatings increases up to 99% and showing excellent inhibition effect with increasing silica content closely related to their wettability and larger contact angle (see Fig. 10).
(a) The Nyquist plots obtained from the blank copper alloy substrate and the superhydrophobic surfaces after treating, using different silica wt.% in neutral 3.5 wt.% NaCl solution and (b) Bode diagrams of measured EIS.
Equivalent circuits of the studied system (a) uncoated and (b) superhydrophobic specimens.
| Specimen | Rct (kΩ cm) | Cdl (μf) | n1 | Rpo (kΩ cm) | Cc (μf) | n2 | Ru (Ω) | IE % |
|---|---|---|---|---|---|---|---|---|
| Cu substrate | 0.091 | 124 | 0.656 | – | – | – | 2.5 | – |
| 1% Silica | 4.09 | 2.91 | 0.276 | 0.186 | 0.113 | 0.721 | 0.198 | 97.7 |
| 1.5% Silica | 4.13 | 0.981 | 0.686 | 0.210 | 0.317 | 0.102 | 2.18 | 97.49 |
| 2% Silica | 5.05 | 3.84 | 0.429 | 0.375 | 0.27 | 0.624 | 9.25 | 99.19 |
- Potentiodynamic polarization curves of the copper alloy and different silica wt.% in 3.5 wt.% NaCl solution.
3.5.2 Potentiodynamic polarization
To investigate the instantaneous corrosion rate, the potentiodynamic polarization curves (Tafel) are employed. Fig. 11 shows the potentiodynamic polarization curves of untreated copper alloy and prepared superhydrophobic surface in 3.5 wt.% NaCl solution using the Tafel extrapolation method. The results of potentiodynamic polarization test are summarized in Table 2. The result clearly shows that the corrosion potential (Ecorr) positively increases from −0.76 V of the untreated copper alloy to −0.665 V of the sample of prepared superhydrophobic surface. This suggests that the film of silica/silane mainly retards the dissolution of copper between the interface of the copper surface and seawater. According to the potentiodynamic polarization curves (Tafel) linear extrapolation method, the corrosion current density (icorr) and the corrosion rate (mpy) of the different sample can be got from Tafel curve (Table 2). The corrosion current density (icorr) of the prepared superhydrophobic surface (2 wt.% Si) is 0.124 μA/cm2, while untreated copper alloy is 15.8 μA/cm2 and the corrosion rate of the sample after silica coating (0.238 mpy) significantly decreases compared with the untreated copper (5.83 mpy). From results obtained by potentiodynamic polarization and electrochemical impedance spectroscopy, it can be concluded that copper alloy substrate is easily penetrated by the Cl− in the seawater. So it cannot improve the corrosion resistance obviously. However, once the surface was chemical modified by silica/silane, the specimen can show excellent anticorrosion properties because of the superhydrophobicity phenomena (see Table 3).
The optical images of the superhydrophobic surface after the tape test (a) sample without adhesive polymer; (b) sample with 1 wt.% adhesive polymer, (c) sample with 2 wt.% adhesive polymer and (d) samples with 3 wt.% adhesive polymer.
| Specimen | icorr (μA cm−2) | Ecorr (V) | Corrosion rate (mpy) |
|---|---|---|---|
| Cu substrate | 15.8 | −0.75 | 5.83 |
| 1 % SiO2 | 1.94 | −0.760 | 0.592 |
| 1.5 % SiO2 | 1.13 | −0.713 | 0.445 |
| 2 % SiO2 | 0.124 | −0.665 | 0.238 |
| FS % | CA (°) before test | CA (°) after test | Adhesion evaluation |
|---|---|---|---|
| Without adhesive polymer (0%) | |||
| 1% | 155 | 118.44 | 0B |
| 1.5% | 158.3 | 123.65 | 0B |
| 2% | 160 | 134.1 | 0B |
| 2.5% | 163.5 | 141.35 | 0B |
| Polymer (1%) | |||
| 1% | 146.2 | 141.12 | 2B |
| 1.5% | 153.94 | 149.33 | 2B-3B |
| 2% | 154.81 | 152.07 | 2B-3B |
| 2.5% | 156.98 | 154.87 | 2B-3B |
| Polymer (2%) | |||
| 1% | 128.65 | 127.22 | 4B |
| 1.5% | 140 | 137.14 | 4B |
| 2% | 152.17 | 150.92 | 4B-5B |
| 2.5% | 154.39 | 153.75 | 4B-5B |
| Polymer (3%) | |||
| 1% | 119.82 | 119.0 | 5B |
| 1.5% | 138.34 | 138.0 | 5B |
| 2% | 154.33 | 154.1 | 5B |
| 2.5% | 155.05 | 154.61 | 5B |
3.6 Durability
It is well-known that the adhesion is a highly important parameter for the practical application of coatings. In this study, the adhesion of sprayed superhydrophobic surface was performed by using Tape Test (ASTM D 3359: Standard Test Methods for Measuring Adhesion by Tape Test). Fig. 11 shows the optical images of the superhydrophobic surface after the tape test. Examination results are summarized in Table 2 where it was illuminated from test results that samples without adhesive polymer show good contact angles and stable layer on substrate but as soon as tape introduced, all the superhydrophobic layers were removed from substrate and contact angles dropped from 155° to 118.4° with FS 1 wt.%, and from 163.5° to 141.35° with samples containing 2.5 wt.% FS, these samples show according to the ASTM standard evaluation of (0B) as shown in Fig. 11(a). Introducing adhesive polymers shows very noticed improvement in durability, where samples with 1 wt.% adhesive polymer demonstrations drop in contact angles by 5° for low FS percentages to about 2° FS with 2.5 wt.% and at the same time the adhesion test showed very good improvement from (0B) to (2B) and (3B), as shown in Fig. 11(b). Samples with polymer percentages 2 wt.% showed average of 1° or 2° drop in contact angles after adhesion test while results of adhesion improved from (4B) to (5B) depend on polymer concentration and substrates. The 3 wt.% polymer improved test results and was classified as (5B) as shown in Fig. 11(d). No delamination or detachment of the film at the edges and within the square lattice was observed. Undoubtedly, this indicates excellent adhesion property with less than 1° drop in contact angles (Wang et al., 2013).
4 Conclusions
A simple and cost effective one step spraying process was applied to prepare highly stable superhydrophobic metal surface based on silane and polymer. This method is time-saving and does not need special equipment or severe conditions. The efficient spray coating method was adopted effectively to get uniform superhydrophobic coatings and it can be used for almost in any kind of substrates such as glass, plastics, metals, fabrics and so on. This Treatment showed CA of 155° and SA less than 5°. The FS micro-nano particles from hierarchical micro-nano structure allowed air to be trapped within the coating layer which increases the surface water repellency and roughness but with poor adhesion. Unlike addition of polymers to the FS, the coating shows excellent stability and can be fabricated on different metal surfaces to prevent metal from corrosion. Therefore, these FS/polymer composite coatings exhibit the strong potential for industrial applications.
References
- Tarns. Faraday Soc.. 1944;40:546-551.
- Range of applicability of the wenzel and Cassie–Baxter equations for superhydrophobic surfaces. Langmuir: ACS J. Surf. Colloids. 2009;25(24):14135-14145.
- [CrossRef] [Google Scholar]
- Design and creation of superwetting/a Antiwetting surfaces. Adv. Mater.. 2006;18:3063-3078.
- [Google Scholar]
- A new. Superhydrophobicity of nanostructured carbon films in a wide range of pH values. Chem., Int. Ed.. 2003;42:4217-4221.
- [Google Scholar]
- Wetting and self-cleaning properties of artificial superhydrophobic surfaces. Langmuir. 2005;21:956-961.
- [Google Scholar]
- Facile approach in fabricating superhydrophobic SiO2/polymer nanocomposite coating. Appl. Surf. Sci.. 2012;261:628-632.
- [Google Scholar]
- Porous polymer coatings: a versatile approach to superhydrophobic surfaces. Adv. Funct. Mater.. 2009;19:1626-1632.
- [Google Scholar]
- Preparation of a super-hydrophobic poly (vinyl chloride) surface via solvent–nonsolvent coating. Polymer. 2006;47:506-509.
- [Google Scholar]
- What do we need for a superhydrophobic surface? A review on the recent progress in the preparation of superhydrophobic surfaces. Chem. Soc. Rev.. 2007;36:1350-1368.
- [Google Scholar]
- Fabrication of superhydrophobic cotton fabrics by silica hydrosol and hydrophobization. Appl. Surf. Sci.. 2011;257:5491-5498.
- [Google Scholar]
- Electrochemical investigation of dynamic interfacial processes at 1-octadecanethiol-modified copper electrodes in halide-containing solutions. Electrochim. Acta. 2003;48:4277-4289.
- [Google Scholar]
- Fabrication of super-hydrophobic film from PMMA with intrinsic water contact angle below 90. Polymer. 2007;48:7455-7460.
- [Google Scholar]
- Effects of the surface roughness on sliding angles of water droplets on superhydrophobic surfaces. Langmuir. 2000;16:5754-5760.
- [Google Scholar]
- Literature review on superhydrophobic self-cleaning surfaces produced by electrospinning. J. Polym. Sci., Part B: Polym. Phys.. 2012;50:824-845.
- [Google Scholar]
- One-step solution-immersion process for the fabrication of stable bionic superhydrophobic surfaces. Adv. Mater.. 2006;18:767-770.
- [Google Scholar]
- Facile and fast fabrication of superhydrophobic surface on magnesium alloy. Appl. Surf. Sci.. 2013;271:182-192.
- [Google Scholar]
- Resistance of solid surfaces to wetting by water. Ind. Eng. Chem.. 1936;28:988-994.
- [Google Scholar]
- Colloids Surf. A: Phys. Eng. Aspects. 2011;377:70-75.
- Applications of bio-inspired special wettable surfaces. Adv. Matter. 2011;23:719-734.
- [Google Scholar]