Preparation of a Superhydrophobic ZnO Film on ITO Glass via Electrodeposition Followed by Oxidation. Effect of the Deposition Time

This study investigates the fabrication of a stable superhydrophobic surface with low contact angle (CA) hysteresis using ZnO thin films prepared by cathodic electrodeposition and subsequent gaseous oxidation. The deposition time is a crucial factor in nanostructuring and producing surface roughness of the films. Cathodic electrodeposition for 60 s created a number of nanopillars, which exhibited the highest CA value, i.e., 167.9°. The rough ZnO surface displayed not only enhanced water repellency with low CA hysteresis but also excellent superhydrophobic stability. The application of the Cassie–Baxter model demonstrated that the ZnO nanostructure contributed to increasing the area of a water droplet in contact with air, leading to superhydrophobicity. Such a unique textured surface showed a great potential for the engineering of strong superhydrophobic coatings.     

Oleic acid-modified superhydrophobic ZnO nanostructures via double hydrothermal method

Superhydrophobic ZnO nanostructures (ZNs) are synthesized via double hydrothermal method without any surface chemical modification. The water contact angle (CA) was approximately ～150?±?2°. A subsequent chemical treatment with oleic acid (OA) contributed to a superhydrophobic surface with a water CA of 162?±?2°. X-ray diffraction pattern revealed high crystalline quality ZNs with hexagonal wurtzite phase. The crystallite size was approximately ～23?nm. Field-emission scanning electron microscopy images display nanosheet formations assembled in flower-, cauliflower-, and nanorod-like ZNs. The CA of ZNs surfaces increased steadily from 152?±?2° to 162?±?2° when the OA weight percentage increased from 2?mg to 10?mg. Furthermore, UV–Vis spectra of ZNs indicated that the absorption band of all samples is distinguished in the ultraviolet region. All ZnO samples were maintained at room temperature for 1?h to 5 months to examine the stability of the structure surface.     

铝基超疏水表面的制备及其耐蚀性

对铝基进行恒电流阳极氧化后,采用正辛基三乙氧基硅烷化学改性,制得超疏水膜。采用接触角测试仪、扫描电镜、红外光谱仪、电化学工作站等,研究了所得超疏水膜的静态接触角、表面形貌、结构及耐蚀性。结果表明,经阳极氧化后,铝基构建了粗糙的微纳米结构,再硅烷化处理后,铝基表面的疏水性增强,静态接触角大于150°。超疏水膜使铝在质量分数为3.5%的NaCl溶液中的自腐蚀电位正移0.11V,腐蚀电流密度降低4个数量级,有效地提高了铝的耐蚀性。     

Simple method for preparing ZnO superhydrophobic surfaces with micro/nano roughness

In this paper, a facile, inexpensive, and environment-friendly method is developed to construct a superhydrophobic surface with hierarchical micro/nanostructures on the steel substrates. The superhydrophobic surface was fabricated by magnetic agitation of a mixture of micro and nanosized Zinc oxide (ZnO) suspensions on a substrate, after being modified with a low-surface energy monolayer of stearic acid, the as-prepared coating exhibits self-cleaning properties with a water contact angle of 162° and a sliding angle of 6°, and shows the good corrosion resistance. It is believed that the rapid and cheap technique have a promising future application for fabricating superhydrophobic surfaces on steel materials.     

Superhydrophobic surfaces: a review on fundamentals,applications, and challenges

Superhydrophobicity is the tendency of a surface to repel water drops. A surface is qualified as a superhydrophobic surface only if the surface possesses a high apparent contact angle (>150°), low contact angle hysteresis (<10°), low sliding angle (<5°) and high stability of Cassie model state. Efforts have been made to mimic the superhydrophobicity found in nature (for example, lotus leaf), so that artificial superhydrophobic surfaces could be prepared for a variety of applications. Due to their versatile use in many applications, such as water-resistant surfaces, antifogging surfaces, anti-icing surfaces, anticorrosion surfaces etc., many methods have been developed to fabricate them. In this article, the fundamental principles of superhydrophobicity, some of the recent works in the preparation of superhydrophobic surfaces, their potential applications, and the challenges confronted in their new applications are reviewed and discussed.     

Enhanced wettability and photocatalytic activity of seed layer assisted one dimensional ZnO nanorods synthesized by hydrothermal method

The wettability and photocatalytic activity of ZnO nanostructures synthesized by hydrothermal method are reported. XRD, FESEM, XPS, TEM, AFM, Contact angle, UV/Vis and photoluminescence spectroscopy are used to characterize the samples. It is observed that ZnO seeded layer results in the formation of nanorods whereas the absence of seed gives rise to flake like morphology. The XRD indicates that ZnO nanorods have preferred orientation along (002) direction. The formation of ZnO nanorods along (002) direction is due to the existence of nucleation sites resulting from the lattice matching of ZnO seed. Wettability studies show that the ZnO nanorods grown on seeded substrate approaches superhydrophobic state with water contact angle (WCA) of 137.0°. The high contact angle is due to the large surface roughness and low surface energy. The enhanced catalytic performance of ZnO nanorods is attributed to the 1D structure, enhanced roughness, crystallinity and a large number of reactive oxidizing species.     

Facile creation of superhydrophobic surface with fluorine–silicon polymer under ambient atmosphere

A fluorine?Csilicon polymer of poly(styrene-co-1H,1H,2H,2H-perfluorooctyl methacrylate-co-vinyltriethoxysilane) (PSFV) was synthesized by bulk polymerization, and superhydrophobic surfaces were subsequently fabricated utilizing phase separation technique in one step by casting PSFV copolymer solution under ambient atmosphere. The PSFV copolymer was dissolved in tetrahydrofuran (THF), and then ethanol was added into the solution to induce phase separation. The surface morphologies of the copolymer films were controlled by the degree of phase separation, which could be tuned easily by the ethanol/THF volume ratio and the solution??s initial concentration. Scanning electron microscopy observations indicated that the superhydrophobic copolymer film had a rough surface with a binary hierarchical structure. A brief explanation of the formation of the special microstructure was put forward. The water contact angle and sliding angle of the superhydrophobic PSFV surface were measured as 162° and 4°, respectively. The simplicity of the operation??s process might make the superhydrophobic surface potentially useful in a variety of applications.     

Tunability of the Adhesion of Water Drops on a Superhydrophobic Paper Surface via Selective Plasma Etching

We report the fabrication of a sticky superhydrophobic paper surface with extremely high contact angle hysteresis: advancing contact angle ～150° (superhydrophobic) and receding contact angle ～10° (superhydrophilic). In addition, we report the controlled tunability of the contact angle hysteresis from 149.8 ± 5.8° to 3.5 ± 1.1°, while maintaining superhydrophobicity, as defined through an advancing contact angle above 150°. The hysteresis was tuned through the controlled fabrication of nano-scale features on the paper fibers via selective plasma etching. The variations in contact angle hysteresis are attributed to a transition of the liquid–surface interaction from a Wenzel state to a Cassie state on the nano-scale, while maintaining a Cassie state on the micro-scale. Superhydrophobic cellulosic surfaces with tunable stickiness or adhesion have potential applications in the control of aqueous drop mobility and the transfer of drops on inexpensive, renewable substrates.     

Water condensation behavior on the surface of a network of superhydrophobic carbon fibers with high-aspect-ratio nanostructures

We have explored the condensation behavior of water on a superhydrophobic carbon fiber (CF) network with high-aspect-ratio hair-like nanostructures. Nanostructures ranging from nanopillars to hairy shapes were grown on CFs by preferential oxygen plasma etching. Superhydrophobic CF surfaces were achieved by application of a hydrophobic siloxane-based hydrocarbon coating, which increased the water contact angle from 147° to 163° and decreased the contact angle hysteresis from 71° to below 5°, sufficient to cause droplet roll-off from the surface. Water droplet nucleation and growth on the superhydrophobic CF were significantly retarded due to the high-aspect-ratio nanostructures under super-saturated vapor conditions. CFs are observed to wet with condensation between fibers of the pristine surface under super-saturated vapor conditions, which eventually leads to flooding. However, dropwise condensation became dominant in the superhydrophobic CF network, allowing for easy removal of the condensed droplets, which largely allowed the interstitial spaces of the fiber network to remain dry. It is implied that superhydrophobic CF can provide a passage for vapor or gas flow in wet environments such as a gas diffusion layer requiring the effective water removal in the operation of proton exchange membrane fuel cell.     

Superhydrophobic antireflective coating with high transmittance

The aim of this study is to fabricate a superhydrophobic antireflective (AR) coating that can be deposited on the covering of a solar cell system. First, AR coatings were synthesized on glass substrates with an average transmittance over 96% by layer-by-layer deposition of polyelectrolyte. Superhydrophobic sol gel was prepared by hydrolyzing tetraethoxysilane and then reacting it with hexamethyldisilazane. The sol gel, aged at 20°C for 96 h, was used to spin-coat a superhydrophobic film with a water contact angle of 163° and a transmittance of ~91%. The superhydrophobic sol gel was spin-coated on the top of an AR coating to form a superhydrophobic AR coating on a glass substrate. The average transmittance, advancing contact angle, and contact angle hysteresis of the superhydrophobic AR coating, which was spin-coated from sol gel aged for 96 h or 168 h, were 94.5 ± 0.7%, 154.0° ± 1.5°, and 15.4° ± 0.3° or 96.4 ± 0.2%, 158.4° ± 4.4°, and 1.8° ± 0.3°, respectively. Strategies for obtaining a superhydrophobic AR coating are discussed herein.     

类水黾脚部“凹凸沟壑”结构仿生超疏水涂层的制备与性能

以坡缕石粉为功能颜料,环氧树脂E-44和杜仲胶混合物为成膜物质,在涂有环氧/杜仲胶清漆的表面制备了一层具有类水黾脚部“凹凸沟壑”结构的仿生超疏水涂层。对涂层形貌和结构进行SEM、FTIR、XRD表征,对C3涂层（坡缕石粉质量分数为25%）进行水接触角、水滚动角、自清洁性能、抗润湿性能、耐磨性能、耐水性能等测试。结果表明,C3涂层表面具有明显的“凹凸沟壑”结构,其平均静态、动态水接触角为153.1°、152.6°,水滚动角为8.8°,具有优异的自清洁性能;C3涂层对泥土浆液、甲基橙溶液和亚甲基蓝溶液具有优良的抗润湿性,接触角均大于150°;C3涂层具有良好的基材适用性,涂覆于混凝土、织物棉布、纸张及塑料等表面均具有超疏水性能;经过载重为100 g的A4纸循环打磨50次,C3涂层水接触角依然高达151.9°,具有较好的耐磨性能;C3涂层在经过18和24 h浸泡后,其水接触角分别为152.2°和144.5°。     

粉煤灰超疏水不锈钢网的制备及油水分离

采用树脂粘接法,将硬脂酸修饰后的粉煤灰用环氧树脂粘接在不锈钢网骨架表面,制备了超疏水不锈钢网,并对其进行了TEM、SEM、FTIR和接触角等表征。结果显示：在高倍显微镜下改性后的超疏水不锈钢网表面呈一定粗糙度的微纳米分级结构,静态水接触角高达153°。此外,该超疏水不锈钢网具有良好的机械稳定性和超疏水耐久性,其表面经机械磨损试验100次后水静态接触角仍高达141°。该材料用于多种油/有机溶剂与水的混合液的分离中,分离效率均高于94%。     

Fabrication of superhydrophobic surfaces based on PDMS coated hydrothermal grown ZnO on PET fabrics

Abstract

Wetting behavior of Zinc Oxide (ZnO) based nanomaterials has been the subject of intense investigations and is an active research field for various engineering applications and modifying the surface wettability of ZnO is of great interest. In this study, one-dimensional (1?D) semiconducting ZnO nanorods are grown on a superhydrophobic polyethylene terephthalate (PET) fabric using a hydrothermal method. A facile polydimethylsiloxane (PDMS) coating is applied onto the ZnO grown PET fabrics to improve the hydrophobicity. A wide range of characterization techniques such as field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), UV-vis spectroscopy and contact angle measurement are used to explore the morphology and wetting behavior of the as-prepared samples. The measured water contact angle (WCA) is >150° indicating its superhydrophobicity. This study reports an efficient way to obtain highly hydrophobic semiconducting ZnO grown on PET fabric, which can be of great interest for many future applications.     

Controllable fabrication of superhydrophobic alloys surface on 304 stainless steel substrate for anti-icing performance

In this paper, 304 stainless steel-based ZnO (304SS-based ZnO) seed layer was prepared by using sol-gel method or electrochemical deposition. Superhydrophobic nano-ZnO (CSS–ZnO) surface were prepared on its surface by hydrothermal method. The results show that different structural morphologies of 304SS-based ZnO surface were prepared by varying different seed layer preparation methods. In the static icing test, compared with hydrophilic nano-ZnO (SS–ZnO) surface, hydrophobic nano-ZnO (QS-ZnO) surface and 304SS surface at −5 °C, −10 °C and −15 °C. The icing time of CSS-ZnO surface was prolonged by about 2.7 h at −5 °C, delayed by about 40 min at −10 °C and delayed by about 9 min at −15 °C. The CSS-ZnO surface is the most effective surface in static anti-icing. It is because that there has a residual air layer at the solid-liquid interface and the coating can still effectively retard ice formation in a partially wetted state. In the dynamic icing test, compared with QS-ZnO surface, SS-ZnO surface and 304SS surface at −16 °C, SS-ZnO surface and QS-ZnO surface have no anti-icing effect, and CSS-ZnO surface has a significant anti-icing effect. The mechanism for inhibiting condensation of water droplets by superhydrophobic surfaces was illustrated, which can be identified that the contact angle of the ice embryo will increase with the increase of the water contact angle. This work provides a practical application for promoting anti-icing ability of 304SS surfaces in industry.     

Facile fabrication of water repellent coatings from vinyl functionalized SiO2 spheres

Water repellent SiO₂ particulate coatings were prepared by a one-step introduction of vinyl groups on the coating surface. Rough surface structure and low surface energy could be directly obtained. Vinyl functionalized SiO₂ (vinyl-SiO₂) spheres with average diameter of 500 nm were first synthesized by a sol–gel method in aqueous solution using vinyltriethoxysilane as the precursor. The multilayer SiO₂ coating fabricated by dip-coating method was highly hydrophobic with a water contact angle of 145.7° ± 2.3°. The superhydrophobic SiO₂ coating with a water contact angle up to 158° ± 1.7° was prepared by spraying an alcohol mixture suspension of the vinyl-SiO₂ spheres on the glass substrate. In addition, the superhydrophobic SiO₂ coating demonstrated good stability under the acidic condition. However, it lost its hydrophobicity above 200°C because of the oxidation and degradation of vinyl groups.     

耐腐蚀超疏水超亲油不锈钢网的制备及其在油水分离过程中的应用

以不锈钢网为基底,通过化学刻蚀法制备微米级粗糙表面,通过一步浸泡法将st9ber法制得的疏水亲油纳米Si O2颗粒沉积到粗糙的不锈钢网表面,制备了具有微纳二级粗糙结构的超疏水超亲油不锈钢网。利用扫描电子显微镜(SEM)、傅里叶变换红外光谱仪(FT-IR)和接触角测量仪(CA)表征了超疏水超亲油不锈钢网的表面形貌、化学组成和润湿性能,并将其用于油水分离过程中。结果表明,疏水亲油纳米Si O2颗粒成功的沉积到不锈钢网表面;水滴在超疏水超亲油不锈钢网上的接触角最大为151°,煤油的接触角为0°;制备的超疏水超亲油不锈钢网不仅能高效的分离不同种类油和水的混合物,还能高效的分离油和腐蚀性液体(强酸或强碱水溶液)的混合物,其耐腐蚀特性可满足复杂环境下的油水分离要求。     

Facile synthesis of superhydrophobic surface of ZnO nanoflakes: chemical coating and UV-induced wettability conversion

This work reports an oriented growth process of two-dimensional (2D) ZnO nanoflakes on aluminum substrate through a low temperature hydrothermal technique and proposes the preliminary growth mechanism. A bionic superhydrophobic surface with excellent corrosion protection over a wide pH range in both acidic and alkaline solutions was constructed by a chemical coating treatment with stearic acid (SA) molecules on ZnO nanoflakes. It is found that the superhydrophobic surface of ZnO nanoflake arrays shows a maximum water contact angle (CA) of 157° and a low sliding angle of 8°, and it can be reversibly switched to its initial superhydrophilic state under ultraviolet (UV) irradiation, which is due to the UV-induced decomposition of the coated SA molecules. This study is significant for simple and inexpensive building of large-scale 2D ZnO nanoflake arrays with special wettability which can extend the applications of ZnO films to many other important fields.     

Facile fabrication of superhydrophobic polyaniline structures and their anticorrosive properties

We report a simple approach for the preparation of superhydrophobic polyaniline (PANI) and its application for the corrosion protection coatings. First, PANI was synthesized conventionally by oxidative polymerization with APS. Subsequently, PANI with different wettability was obtained by modification with different surfactants. The surface modification of PANI with three different surfactants (sodium dodecylbenzenesulfonate, polyethylene glycol, and cetyltrimethylammonium bromide) provided excellent surface superhydrophobicity (water contact angle >150°). The structure and morphology of as‐prepared PANI were characterized with Fourier transform infrared, Energy dispersive X‐ray spectroscopy, and Scanning electron microscopy. Corrosion protection performance of PANI with different wettability was evaluated in 3.5% NaCl electrolyte using Tafel polarization curves and electrochemical impedance spectroscopy. The results indicated that various superhydrophobic PANI coatings have better anticorrosion performance as compared to the hydrophilic PANI. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 44248.     

Preparation, characterization and wettability of porous superhydrophobic poly (vinyl chloride) surface

A porous superhydrophobic poly (vinyl chloride) surface was obtained by a simple approach. The water contact angle and the sliding angle of the superhydrophobic poly(vinyl chloride) surface were 154 ± 2.3o and 7o, respectively. The porous superhydrophobic PVC surface remained superhydrophobic property in the pH range from 1 to 13. When the superhydrophobic PVC surface was immersed in water with the temperatures ranging from 5 °C to 50 °C for 1 h to 30 days, the water contact angle remained higher than 150°. After outdoor exposure for 30 days, the contact angle still remained 150o.