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The air layer produced by superhydrophobic coating can change the contact mode between the surface and water, which grants it potential application prospects in buoyancy enhancement and drag reduction. However, the buoyancy mechanism of superhydrophobic coating still lacks systematic understanding. Herein, a superhydrophobic glass was prepared by coating a ZnO/epoxy resin (ER) solution onto the glass, which was subsequently reacted with mixed acetic acid, stearic acid, and ethanol solution. The introduction of superhydrophobic coating changes the contact mode between the surface of the glass and water, and the coated position will affect the final floating state of superhydrophobic glass. Edge-coated, top-coated and whole-coated glass can float on the surface of water due to surface tension. In addition, whole-coated glass possesses the highest loading capacity of 7.48 g. Furthermore, the whole-surface coating method was applied to a model boat to investigate the drag reduction effect of superhydrophobic coating on a model boat at terminal velocity. The drag reduction efficiency of superhydrophobic model boat increased from 5 % to 21 % with the increase of pulling force, which demonstrating a good drag reduction effect. Thus, this superhydrophobic coating may offer a relevant strategy for buoyancy enhancement and drag reduction in practical applications. [Display omitted] • Superhydrophobic coating changes the contact mode between the glass and water. • The coated position will affect the final floating state of superhydrophobic glass. • Whole surface-coated glass possesses the highest loading capacity of 7.48 g. • Superhydrophobic coating reduce the adhesion of water molecules and drag resistance. [ABSTRACT FROM AUTHOR]

A simple immersion method to fabricate a superhydrophobic polyurethane sponge with oil-water separation efficiency, reusability and chemical stability. • A simple immersion method to fabricate superhydrophobic polyurethane sponge. • This superhydrophobic PU sponge shows excellent oil-water separation efficiency, reusability. • The prepared superhydrophobic PU sponge was stable from pH 1–11, allowing it to be applied in a wide range of environments. In this study, a superhydrophobic polyurethane sponge was prepared by a simple immersion method. The strategy was based on coating a ZnO/epoxy resin solution onto the skeleton of a porous polyurethane sponge, followed by reacting it with a mixture of stearic acid/acetic acid/ethanol solution. The prepared superhydrophobic polyurethane sponge with a contact angle of 156 ± 3° can selectively separate mixtures of water and various oily solvents. The separation efficiencies of the superhydrophobic polyurethane sponge for a variety of oil/water mixtures were all above 98 %. Moreover, the prepared superhydrophobic polyurethane sponge had superior reusability and maintained a separation efficiency of more than 97 % after ten oil/water separation cycles, and it was chemically stable from pH 1–11. This superhydrophobic polyurethane sponge may offer a new oil/water separation strategy due to its excellent separation efficiency, reusability, and chemical stability. [ABSTRACT FROM AUTHOR]

Superhydrophobic surfaces have significant applications in industrial and chemical fields. However, their current mechanical stability and underwater durability are insufficient, limiting their widespread application. This study successfully developed a durable superhydrophobic coating suitable for various substrates using a simple one-step spraying technique. By thoroughly investigating the effects of SiO 2 concentration and curing temperature on the coating's wettability, underwater durability and mechanical stability, the preparation process was optimized. The prepared superhydrophobic coating achieved a contact angle (CA) of 159.6° and a sliding angle (SA) of less than 1°. In tests of underwater immersion, sandpaper abrasion, repeated water impact, corrosion resistance and ultraviolet (UV) resistance, the coating demonstrated excellent underwater durability, mechanical stability, chemical stability and UV stability. Furthermore, when applied to the steel sphere, the superhydrophobic coating exhibited significant drag reduction effects underwater, reducing the drag coefficient by approximately an order of magnitude and achieving a drag reduction efficiency of 79.1 %. Numerical simulations using STAR-CCM+ showed that the streamlined cavity formed by the superhydrophobic coating effectively suppressed fluid separation, reduced pressure-induced drag, and allowed the superhydrophobic steel sphere to attain a higher terminal velocity. Therefore, the superhydrophobic coating developed in this study has tremendous application potential in underwater drag reduction and is expected to provide effective solutions for energy-saving and drag reduction in fields such as maritime navigation. [Display omitted] • Preparing robust superhydrophobic surfaces by a simple one-step spray-coating method. • Effects of SiO 2 concentration and curing temperature on coating properties. • Application of the optimized superhydrophobic coating for underwater drag reduction. • Analyzed the mechanism of underwater drag reduction through numerical simulation. [ABSTRACT FROM AUTHOR]

Graphical abstract A simple method was used to fabricate the superhydrophobic aluminum with good superhydrophobicity, thermostability, antifouling and anticorrosion abilities. Abstract The development of techniques to fabricate superhydrophobic aluminum surfaces is rapidly maturing, yet the problems of high loss of material and complex preparation still persist. To address this, a simple method that combines droplet etching and chemical modification was used to fabricate a superhydrophobic aluminum surface, with a contact angle of 156° and a sliding angle of 5°. Compared with the traditional immersion method, droplet etching can properly preserve the integrity of the aluminum material and also provide a rough structure on the aluminum surface. The optimal superhydrophobicity of the aluminum surface was obtained by one-step immersion in pentadecafluorooctanoic acid aqueous solution at 80 ℃. Thermostability, anticorrosion, self-cleaning, and antifouling tests were subsequently performed. The results demonstrated that the superhydrophobic aluminum surface was easily prepared and possessed thermostability, anticorrosion, self-cleaning and antifouling abilities. [ABSTRACT FROM AUTHOR]