Fabrication Of Superhydrophobic Coatings Research Articles

Fabrication of Superhydrophobic Coating (SiO<sub>2</sub>/PDMS) by a Simple Method

A simple and economical method for producing a superhydrophobic surface on a glass substrate is investigated. The surface composes of silica particles synthesized via a sol-gel method with an average particle size of 69.33 nm. Organosilan PDMS (FS-1200 silicon sealant) was used to reduce the surface energy of particles, which were then coated onto a glass substrate by dip coating. After coating, the substrate was dried for one hour at 60ºC in an oven to remove excess solvent. XRD, FE-SEM, FTIR, and contact angle (CA) measurement techniques were used to characterize silica particles and coated surfaces. The water contact angle (WCA) of pure SiO2 (NPs) was 86º indicating its hydrophilic qualities, while the contact angle of a superhydrophobic surface was 156º.

Fabrication of Superhydrophobic Coating by Spraying PDMS-SiO2 Suspension for Self-Cleaning Application

Superhydrophobic surfaces that mimic lotus leaf surfaces have been widely studied due to their unique self-cleaning ability. Herein, we have fabricated a self-cleaning superhydrophobic coating on a glass substrate using the facile sol-gel spray coating method. The silica particles were synthesized via the sol-gel method in acidic conditions. A self-cleaning superhydrophobic coating was achieved by spraying a suspension of synthesized SiO2 particles and PDMS on a glass substrate at room temperature. The incorporation of SiO2 particles in the PDMS matrix resulted in the formation of a rough structure on the glass surface. This surface exhibited excellent superhydrophobic properties with a high water contact angle (WCA) of 154° and a low sliding angle (SA) of 4°. In addition, the prepared samples showed strong mechanical resistance against various tests such as multiple adhesive tape peeling, sandpaper abrasion, and pencil hardness. As a result, the developed superhydrophobic coating holds great potential for self-cleaning applications on a larger scale.

Fabrication of Superhydrophobic Coatings by Using Spraying and Analysis of Their Anti-Icing Properties

Ice accumulation on glass insulators is likely to cause faults such as flashover, tripping and power failure, which interfere with the normal operation of the power grid. Accordingly, superhydrophobic coatings with great anti-icing potential have received much attention. In this study, three superhydrophobic coatings (PTFE, Al2O3 and SiO2) were successfully prepared on glass surfaces by using one-step spraying. The microscopic morphology, wettability, anti-icing and anti-glaze icing properties of the superhydrophobic coatings were comparatively analyzed. The results indicated that the PTFE coating had a densely distributed rough structure, showing a contact angle of 165.5° and a sliding angle of 3.1°. The water droplets on the surface could rebound five times. Compared with the Al2O3 and SiO2 coatings, the anti-icing performance of the PTFE coating was significantly improved. The freezing time was far more than 16 times that of glass (4898.7 s), and the ice adhesion strength was 9 times lower than that of glass (27.5 kPa). The glaze icing test in the artificial climate chamber showed that the icing weight of the PTFE coating was 1.38 g, which was about 32% lower than that of the glass. In addition, the icing/melting and abrasion cycles destroyed the low-surface-energy substances and nanostructures on the surface, leading to the degradation of the anti-icing durability of the PTFE coatings. However, the PTFE coating still maintained excellent hydrophobicity and anti-icing properties after UV irradiation for up to 624 h. The superhydrophobic coatings prepared in this work have promising development prospects and offer experimental guidance for the application of anti-icing coatings on glass insulators.

Construction of superhydrophobic GO/Ca coating on AZ31 magnesium alloy for enhanced anti-corrosion performance

The application of magnesium alloys has garnered increasing interests in transportation, electronics and biomedical engineering fields, and the fabrication of superhydrophobic coatings on the surface of magnesium alloys is considered as an effective means to improve the corrosion resistance. However, major technical barriers restricting its application lie in the long-term durability and mechanical properties of superhydrophobic coatings. Herein, a calcium myristate coating with graphene oxide (GO) is fabricated on AZ31 magnesium alloy by electrodeposition. The coating is constructed in a particularly simple and gentle way by the synergy of inorganic nanomaterials and organic acid salts. It was found that the deposition time significantly affected the morphology, thickness and wettability of the GO/Ca coating and further influenced the corrosion resistance and durability. The best corrosion resistance is obtained when the deposition time is 30 min. With 30 min deposition, the corrosion current density of the substrate was reduced by 3 orders to (2.38 ± 1.02)× 10−9 A cm−2, and the impedance modulus at the lowest frequency could reach 108 Ω cm2. And after 21 days of immersion, the impedance modulus at low frequency of GO/Ca-30 is still as high as 105. It could be attributed to the tortuous path and denser structure with introduction of GO. Besides this, the scratch test and adhesion strength describe that the GO/Ca coating presents a good adhesion to the substrate. Considering its satisfying corrosion resistance, long-term durability and high adhesion strength, it is expected that the as-prepared superhydrophobic coating on AZ31 alloy is promising for anti-corrosion application.

Facile fabrication of robust superhydrophobic coating for enhanced corrosion protection on AZ91 magnesium alloy by electroless Ni-B/GO plating

Artificial superhydrophobic surfaces have drawn extensive research interest due to their great applicational potential. However, the specialized materials and equipment, multistep preparation processes, and vulnerable rough structures severely restrict their industrial development. In this research, a robust superhydrophobic Ni-B/GO composite coating was fabricated successfully on AZ91 magnesium alloy based on electroless plating (EP), followed by chemical modification with stearic acid ethanol solution. With a water contact angle of 162.8° and a sliding angle of 1.3°, the superhydrophobic coating displayed strong physical/chemical stability and outstanding self-cleaning. Moreover, the superhydrophobic coating revealed excellent corrosion resistance with higher Ecorr (−0.411 V) and lower icorr (2.14 × 10−6 A·cm−2) in 3.5 wt% NaCl solution. Also, the Rct value was 2.75 × 105 Ω·cm2 and increased three orders of magnitude compared with the AZ91 Mg. Therefore, this study offers an innovative perspective for fabricating the micro/nano rough structures on magnesium alloy, and the fabrication of superhydrophobic coatings by electroless nickel plating as a low-cost and eco-friendly method will have good industrial application prospects.

Rational fabrication of high-durability superhydrophobic coatings based on the excellent compatibility between nanoparticles and polymers

Superhydrophobic coatings arouse much attention for their extensive potential applications from industry to our daily life. The introduction of nanoparticles into polymer matrix is one of the main methods to construct superhydrophobic coatings. However, the fabrication and practical application of super-antiwetting coatings are frequently hindered, owing to the incompatibility between inorganic nanoparticles and organic polymer matrix. Herein, we develop a durable coating that tackles the compatibility problem of inorganic and organic phases, formulating with hyperbranched polysiloxane modified silica nanoparticles and silicon-based acrylic polymers. The as-prepared coatings exhibit excellent superhydrophobicity with CA beyond 158° and SA below 4°. They are capable of retaining superhydrophobicity after exposing to harsh conditions including immersion in acid-base solutions for 12 days, boiling water for 3 h and high temperature of 150 °C for 24 h, as well as experiencing various mechanical damage such as 100 cycles of sandpaper abrasion, 40 cycles of tape peeling and 200 g sand impact. Furthermore, the coating can be further applied to anti-insect blood adhesion under dynamic conditions, self-cleaning of pollutants in life and substrate surfaces with diverse properties. The preparation technology of superhydrophobic coatings has unique advantages in scalable productivity, less equipment requirements and mild process conditions, and also provides insights into the fabrication of superhydrophobic coatings with good compatibility of inorganic and organic materials.

Fabrication of superhydrophobic coatings by low-temperature sintering of Ag nanoparticle paste

Ag nanoparticle paste was used to fabricate mechanically durable superhydrophobic surfaces via sintering. A facile method was first adopted to synthesize the Ag nanoparticle paste. To obtain multi-level hierarchical superhydrophobic surfaces, a stainless steel mesh was introduced to the sintering process of the Ag nanoparticle paste. The morphology of the steel mesh was replicated onto the Ag surface under sintering pressure, forming a first-level surface roughness. Using low-temperature sintering, a bond was created between the Ag nanoparticles, enhancing the mechanical durability of the as-prepared surfaces. The gap between the Ag nanoparticles was retained under low pressure, leading to a high surface roughness, which is beneficial for preparing superhydrophobic surfaces. After modification with stearic acid, the as-fabricated Ag coatings exhibited good superhydrophobicity, long-term durability, and mechanical stability. The superhydrophobic Ag coatings can also be fabricated on different substrates successfully. Thus, this type of superhydrophobic coating has promising prospects in practical applications.

Synthesis of Dimpled Particles by Seeded Emulsion Polymerization and Their Application in Superhydrophobic Coatings.

Dimpled particles are synthesized through the seeded polymerization of fluoroacrylate and styrene on swelled polystyrene spheres. The morphologies of the particles can be controlled by the polymerization temperature, the amount of solvent swelling the seeds or the ratio of the fluoroacrylate monomer over styrene. Golf-ball-like particles with many small dimples on their surfaces are obtained at low polymerization temperatures or with a small amount of solvent. Particles with a large single dimple are formed at higher polymerization temperatures, with larger solvent amounts or a higher ratio of fluoroacrylate over styrene. The morphology formation mechanism of these dimpled particles is proposed and the application of these particles in the fabrication of superhydrophobic coatings is demonstrated.

Facile and Eco-Friendly Preparation of Mild Steel Based Superhydrophobic Surfaces without Chemical Modifications

The fabrication of superhydrophobic coatings on mild steel has attracted considerable attention. However, some methods are cumbersome and unsuitable for large-scale preparation, limiting industrial applications. Furthermore, the extensive use of fluorinated compounds to achieve low surface energy is not environmentally friendly. This paper proposed a facile method based on electrodeposition and annealing to prepare mild steel-based superhydrophobic surfaces without chemical modifications. Subsequently, SEM images were analyzed, and it was observed that the plating parameter (current and time) significantly affected surface morphology. At optimum process parameters, a rough surface with a multi-level structure was formed on the plated surface, contributing to superhydrophobic properties. XPS, EDS, and XRD were utilized to analyze surface composition. The results indicated the presence of copper oxides, zinc oxides, and a large number of hydrocarbons on the prepared superhydrophobic surface. These transition metal oxides on the surface adsorbed hydrocarbons in the air during the annealing process, which lowered the surface energy. Combined with the obtained multi-level morphology, a superhydrophobic surface was achieved. Finally, the corrosion behavior was evaluated in 3.5 wt% NaCl solution by AC impedance spectroscopy. Results showed that the obtained superhydrophobic surface, compared with the untreated coating and the steel substrate, showed a substantial improvement in corrosion resistance. A mild steel-based superhydrophobic surface with a contact angle greater than 150 degrees and excellent corrosion resistance was finally obtained. We hope this study will facilitate the industrial preparation of superhydrophobic coatings, especially in marine engineering, since this method does not require complex processes or expensive equipment and does not require fluorinated substances.

Superhydrophobic micro-nano structured PTFE/WO3 coating on low-temperature steel with outstanding anti-pollution, anti-icing, and anti-fouling performance

The fabrication of superhydrophobic coatings on the low-temperature steels has rarely been explored to this day. Herein, we designed and fabricated a superhydrophobic micro-nano structured composite coating on the E40 low-temperature steel, which was composed of an underlying WO3 coating derived from the pulsed electrodeposition process and a top polytetrafluoroethylene (PTFE) layer obtained from the magnetron sputtering. The synergistic effect of the hierarchical micro-/nanostructures of the WO3 coating and the low surface free energy of the fluorine-containing PTFE layer makes the PTFE/WO3 coating superhydrophobic, which demonstrated a water contact angle of 159° and a water roll-off angle of ≤1°. The PTFE/WO3 coating exhibited outstanding anti-pollution properties towards both the solid pollutant such as carbon black particles and the liquid pollutant such as black ink. Importantly, the PTFE/WO3 coating demonstrated excellent anti-icing properties with low icing temperature and small ice-adhesion strength, while simultaneously possessing outstanding anti-fouling performance. The present work provides a new strategy for fabricating coatings with multifunctionality on metallic materials which can work under low-temperature and biofouling conditions.

Corrosion Resistant Superhydrophobic Aluminum Alloy: A Review

Aluminum alloys are widely used in aerospace and space applications due to their high strength to weight ratio. The most prevalent method to prevent corrosion of aluminum alloys is anodic oxidation or anodization treatment. The anodized layer is porous and hence there are chances of penetration of moisture and corrosion of underlying substrate underneath the anodized layer. Surface modification of the aluminum alloy by superhydrophobic coating is a very attractive method to improve the corrosion resistance of aluminum alloys. The inspiration for the fabrication of superhydrophobic coatings is obtained from various examples in nature such as strider’s legs and lotus leaf. The fabrication of superhydrophobic coatings involves two important steps; generation of a rough surface and deposition of low surface energy material. The present paper reviews the various researches undertaken for the production of superhydrophobic surfaces on aluminum and aluminum alloys. Finally, the scope of future research activities in the fabrication of superhydrophobic coatings has been discussed in the paper.

Fabrication of Superhydrophobic Coatings on Glass based on Poly(dimethylsiloxane) and Fumed Silica

This study reports the preparation of superhydrophobic covalently attached poly(dimethysiloxane)(PDMS)/fumed silica composite coatings on glass via spin-coating and subsequent heating. The effect of PDMS molecular weight and fumed silica type (hydrophilic and three different hydrophobic) on the wettability and morphology were studied in detail and the wettability and morphology of the coatings were characterized by contact angle measurements and scanning electron microscopy (SEM). Superhydrophobic coatings which have advancing contact angles of 172-174° and contact angle hysteresis (CAH) as low as 7-8° were obtained using 4% (w/v) PDMS modified hydrophobic fumed silica and all kinds of PDMS. The surfaces which were prepared by 4% (w/v) hydrophilic and dimethylsiloxy modified fumed silica had high advancing contact angles of 163-168° but the CAH on these surfaces were higher than the ones prepared using PDMS modified fumed silica. This can be ascribed to the incompatibility of the hydrophilic and dimethylsiloxy modified fumed silica with the PDMS matrix which was also confirmed with the SEM results.

Robust Super-Hydrophobic Coating Prepared by Electrochemical Surface Engineering for Corrosion Protection

Corrosion—reactions occuring between engineering materials and their environment—can cause material failure and catastrophic accidents, which have a serious impact on economic development and social stability. Recently, super-hydrophobic coatings have received much attention due to their effectiveness in preventing engineering materials from further corrosion. In this paper, basic principles of wetting properties and corrosion protection mechanism of super-hydrophobic coatings are introduced firstly. Secondly, the fabrication methods by electrochemical surface engineering—including electrochemical anodization, micro-arc oxidation, electrochemical etching, and deposition—are presented. Finally, the stabilities and future directions of super-hydrophobic coatings are discussed in order to promote the movement of such coatings into real-world applications. The objective of this review is to bring a brief overview of the recent progress in the fabrication of super-hydrophobic coatings by electrochemical surface methods for corrosion protection of engineering materials.

Fabrication of superhydrophobic coatings with edible materials for super-repelling non-Newtonian liquid foods

Superhydrophobic coatings were fabricated with edible candelilla wax and rice bran wax via one step spraying a wax-in-ethanol hot solution on polypropylene (PP) substrates for food containers. Beautiful “flower-like” surface microstructures were formed only by self-roughening of the coating without adding any nanomaterials or any lithography step, making the coatings display great superhydrophobicity for a variety of non-Newtonian viscous liquids with contact angles higher than 150° and sliding angles close to 0°. The as-coated PP can keep excellent superhydrophobic properties after impact from hot aqueous solution (about 70 °C) or 1200 repeated bends, exhibiting good heat resistance and superior flexibility. Importantly, the excellent durability could make it super-repel non-Newtonian fluids after various types of damage (including finger touching and multiple abrasion cycles with sandpaper). This approach can be applied to the inner surface of all kinds of food packaging to reduce liquid food residue.

Fast Strategy to Functional Paper Surfaces.

Paper, with advantages of low-cost, easy fabrication and disposal, flexibility and renewability, is a suitable substrate material for various applications. Functionalization and patterning on paper substrates are commonly required in many applications. Although many methods have been developed to achieve this, they typically suffer from some drawbacks such as time-consuming process, specific device dependence, lack of flexibility, low patterning resolution, and so forth. Herein, we present a general and fast method to functionalize paper sheets and create patterns. The whole modification process can be completed in 10 min and can be applied on various types of paper substrates and other natural materials such as natural fabrics. By our method, many commonly used functional groups can be covalently attached and patterned on paper substrates, while the characteristic features of the original paper substrates, for example, color, transparency, and conductivity, can be perfectly retained after modification to allow these properties to be incorporated into the resultant materials. High-resolution patterns can be created on paper by applying a photomask during the modification or controlling the time of modification to precisely control the functionality at any area on the obtained paper substrates. We also show the potential applications of our method in the fabrication of superhydrophobic coatings and biomaterials.

Fabrication of superhydrophobic coatings on cotton fabric using ultrasound-assisted in-situ growth method

A highly durable superhydrophobic cotton fabric was fabricated via an ultrasound-assisted in situ growth method. The morphology and the component of the superhydrophobic coating on cotton fabric were characterized by SEM and FT-IR, respectively. The as-prepared superhydrophobic cotton fabric shows liquid repellency for common household liquids, outstanding stability in deionized water, various solvents, strong acidic/alkali solution, and boiling water, and good mechanical robustness after sandpaper abrasion test. Furthermore, the fabric coating shows both superhydrophobic and superoleophilic properties simultaneously with a high water contact angle of 154 ± 0.5°. Thus, the as-prepared superhydrophobic cotton fabric can be used to separate the oil/water mixtures (e.g., n-hexane, n-heptane, dodecane, and kerosene) and the separation efficiency was more than 96%. In addition, the obtained fabric maintains good reusability after 50 separation cycles with above 97% of the separation efficiency for the both dodecane/water and n-heptane/water mixture. The as-prepared fabric coating shows high separation efficiency, stable recyclability, and better durability, which can be used in oil spill accidents for oil/water separation.

Micrometer-sized spherulites as building blocks for lotus leaf-like superhydrophobic coatings

Micropapillae covered by nanometer-sized wax crystals are essential building blocks of lotus leaf surface for repelling water and self-cleaning. It is generally time-consuming and complex to construct similar artificial micropapillae covered by nanometer-sized protuberances in the fabrication of superhydrophobic coatings without the aid of nanomaterials or special materials. We develop a cost-efficient strategy to simplify the fabrication process of lotus leaf-like superhydrophobic coatings by using micrometer-sized spherulites as building blocks. Well-controlled lotus leaf-like superhydrophobic coatings were prepared from hydrogenated castor oil spherulites through a one-step solution-immersion process. The result coatings have water contact angles over 150° and water shedding angles below 10°. It was demonstrated that micrometer-sized spherulites originated from common material could easily form lotus leaf-like superhydrophobic coatings on different materials through simple crystallization process.

Facile fabrication of uniform hierarchical structured (UHS) nanocomposite surface with high water repellency and self-cleaning properties

In the present study, two-stage process for the fabrication of superhydrophobic Ni-Cu-TiO2 nanocomposite coatings on the copper substrate has been introduced. Surface modification was performed on the electrodeposited coatings by myristic acid-ethanol solution to achieve superhydrophobicity. Additionally, in order to further study the roughness effect, instead of addition of copper ions in electrodeposition bath, three substrates were roughened by electrochemical etching method. Water repellency properties were studied through measurement of static and dynamic contact angles, and performing bouncing test, self-cleaning and water-jet evaluation. The samples were electrodeposited in various current densities, and the highest corrosion resistance and water repellency properties were obtained for the sample which was electrodeposited in two consecutive steps and modified by a fatty acid called myristic acid (which significantly reduces surface energy of the coating). The highest water contact angle (161°) and the lowest contact angle hysteresis (3°) were obtained for the sample which was coated by 10 mA/cm2 (144 min) and 20 mA/cm2 (18 min), respectively. Since this approach does not require any sophisticated equipment and materials, it shows promising future in the fabrication of superhydrophobic coatings.

Rapid synthesis of inherently robust and stable superhydrophobic carbon soot coatings

The fabrication of superhydrophobic coatings using a candle flame or rapeseed oil has become very attractive as a novel approach for synthesis of water repellent surfaces. Here, we report an improved, simplified and time-efficient method for the preparation of robust superhydrophobic carbon soot that does not require any additional stabilizers or chemical treatment. The soot's inherent stabilization is achieved using a specially-designed cone-shaped aluminum chimney, mounted over an ignited paper-based wick immersed in a rapeseed oil. Such configuration decreases the level of oxygen during the process of combustion; altering the ratio of chemical bonds in the soot. As a result, the fractal-like network of the carbon nanoparticles is converted into dense and fused carbon chains, rigidly coupled to the substrate surface. The modified carbon coating shows thermal sustainability and retains superhydrophobicity up to ∼300°C. Furthermore, it demonstrates a low contact angle hysteresis of 0.7–1.2° accompanied by enhanced surface adhesion and mechanical durability under random water flows. In addition, the soot's deposition rate of ∼1.5μm/s reduces the exposure time of the substrate to heat and consequently minimizes the thermal effects, allowing the creation of superhydrophobic coatings on materials with low thermal stability (e.g. wood or polyethylene).

Fabrication of Superhydrophobic Coating on Stainless Steel Surface by Femtosecond Laser Texturing and Chemisorption of an Hydrophobic Agent

We determine the optimal regime of femtosecond IR laser nano- and micro-texturing of a stainless steel surface for subsequent multimodal surface relief texturing and chemical hydrophobization. We characterize the topological parameters of the modi_ed surface and its wetting parameters after hydrophobization.