As-prepared Superhydrophobic Surface Research Articles

Laser peening without coating fabricated superhydrophobic aluminum alloy with favorable mechanical properties

This study prepared 2024-T351 aluminum alloy surfaces with excellent hydrophobic properties by laser peening without coating(LPwC) and post-treatment process (silane solution immersion modification treatment). The surface morphology, microhardness, roughness and residual stress of the specimens before and after LPwC were characterized. Besides, the surface composition and droplet contact angle of the specimens before and after LPwC were measured to investigate the mechanism of enhancing the hydrophobic properties by LPwC. The results showed that after LPwC treatment, the surface of the specimen was uniformly distributed with a large number of micro-nano porous structures and the surface roughness was significantly increased. After the modification treatment with fluorosilane solution, the F element on the surface of the specimen significantly increased, the surface energy decreased, the droplet contact angle rose to above 150°, and the sliding angle dropped to below 10°, which imparted the superhydrophobicity on the surface. After LPwC treatment, the grain size of the specimen near-surface layer was reduced, and high magnitude residual compressive stress was generated inside the matrix, which increased the microhardness of material. The as-prepared superhydrophobic surface exhibits excellent water flow repellency and favorable mechanical properties, which promoted the application of superhydrophobic preparation process in the aerospace field.

Smart controlling on the bi-stable state of bio-inspired multifunctional coatings for anti-/de-icing applications

Outdoor equipment can suffer from functional failure in winter due to ice accumulation. Although functional materials are widely recognized as promising candidates for anti-icing and de-icing applications, ice inevitably accretes on surfaces at extremely low temperatures and high humidity. If surfaces display reversible superhydrophobic and slippery performance, similar to Lotus leaves and fish skin, it will significantly improve the anti-icing and de-icing performance. This study proposes a novel type of multifunctional coating that could smartly reverse between superhydrophobic and slippery properties on demand. The superhydrophobic coatings with diverse morphologies were obtained by employing different sizes and shapes of nanoparticles. Due to the low adhesion and photothermal properties, the superhydrophobic samples presented good freezing rain prevention and snow-melting performances by outdoor tests in winter. The samples with slippery surfaces were produced by infusing dodecane on the as-prepared superhydrophobic surface. Both the superhydrophobic and slippery surfaces can effectively propel the water droplets, prolong the freezing time and enhance ice removal performance in an extremely cold environment. Therefore, the coated samples with bi-stable states (i.e., superhydrophobic and slippery states) were successfully achieved with the potential to be widely applied under different service environments. This facile strategy will provide the possibility for developing novel materials with smart reversible wettability for anti-icing and de-icing applications.

A robust superhydrophobic coating with multi-dimensional micro-nano structure on 5052 aluminum alloy

This paper presents a new method to constructing a robust superhydrophobic surface with multi-dimensional roughness on 5052 aluminum alloy (SHC-Al). The microstructure and surface properties of the SHC-Al were investigated using various techniques including Field emission scanning electron microscope (FESEM), Energy dispersive X-ray spectroscopy (EDS), Laser confocal scanning microscope (CLSM), Fourier transform infrared spectrometer (FTIR), X-ray diffractometer (XRD), Contact angle measuring instrument and electrochemical techniques. The findings indicated that the surface had a hierarchical flower-like micro-nano rough structure, with a water contact angle (WCA) of 162.4° and a rolling angle (SA) of 3.2°, making it easy to clean. Furthermore, the superhydrophobic property can be restored after 90 wear cycles or 33 tape stripping. Electrochemical results demonstrated that the coating had a low corrosion current of 2.742 × 10−9 A·cm−2. The coating remained effective in preventing corrosive mediums from reaching 5052 aluminum surface after soaking in 3.5 wt% NaCl solutions for 72 h, with a coating protection efficiency of 97.9 %, demonstrating excellent anticorrosion properties. Additionally, the coating showed exceptional stability. The results demonstrate that the as-prepared superhydrophobic surface is robust and corrosion-resistant, which hold great promise for practical applications.

Hierarchically Branched Siloxane Brushes for Efficient Harvesting of Atmospheric Water.

Atmospheric water harvesting is considered a viable source of freshwater to alleviate water scarcity in an arid climate. Water condensation tends to be more efficient on superhydrophobic surfaces as the spontaneous coalescence-induced droplet jumping on superhydrophobic surfaces enables faster condensate removal. However, poor water nucleation on these surfaces leads to meager water harvest. A conventional approach to the problem is to fabricate micro- and nanoscale biphilic structures. Nonetheless, the process is complex, expensive, and difficult to scale. Here, the authors present an inexpensive and scalable method based on manipulating the water-repellent coatings of superhydrophobic surfaces. Flexible siloxane can facilitate water nucleation, while a branched structure promotes efficient droplet jumping. Moreover, ToF-SIMS analysis indicated that branched siloxane provides a better water-repellent coating coverage than linear siloxane and the siloxanes comprise hydrophilic and hydrophobic molecular segments. Thus, the as-prepared superhydrophobic surface, TiO2 nanorods coated with branched siloxanes harvested eight times more water than a typical fluoroalkylsilane (FAS)-coated surface under a low 30% relative humidity and performed better than most reported biphasic materials.

In-situ fabrication of superhydrophobic surface on copper with excellent anti-icing and anti-corrosion properties

The accumulation of ice on electrical construction works not only leads to the reduced efficiency of power supply and heat exchangers, but also increases the energy losses and even brings about serious disasters. Therefore, it is essential to reduce or eliminate the issue of ice accumulation on metal constructions. Nowadays, superhydrophobic surfaces have received lots of attentions for their outstanding hydrophobicity. In this study, Cu(OH)2 nano grass was firstly in-situ constructed on copper surface via simple anodization, then superhydrophobic CuO nano needles were obtained after the dehydration of Cu(OH)2 and modification with fluoro-alkyl silanes. The results showed that when the anodic oxidation temperature was 20 °C and the current density was 2 mA·cm−2, nano-needle-like multistage micro-nano structures can be obtained. The as-prepared superhydrophobic surface showed the water contact angle as large as 162° and sliding angle lower to 4°. Additionally, the as-prepared superhydrophobic surface displayed outstanding anti-icing property, delaying icing substantially even under − 10 °C environment regardless of droplet volume and type. Moreover, it also revealed good anti-corrosion property with a corrosion current density of 2.2 × 10−8 Ω·cm2 and the corrosion resistance of 1.55 × 106 Ω·cm2 which is about three order of magnitudes than that of bare copper. We prospect that this easily prepared surface can provide a solution of anti-icing and anti-corrosion for electrical construction works and large-scale metals.

Achieving hierarchical structure with superhydrophobicity and enhanced anti-corrosion via electrochemical etching and chemical vapor deposition

In this work, superhydrophobic surfaces with hierarchical and multi-scale micro/nanostructures were fabricated by a simple method without damaging the substrate material. Electrochemical etching and chemical vapor deposition were taken to adhere the robust electroplated Ni with the excellent hydrophobic material of polydimethylsiloxane (PDMS) to provide a double-layer protection for the bare Cu substrate. The as-prepared superhydrophobic surface exhibited a high contact angle (CA) of 158.5 ± 0.4° and a low slide angle (SA) of 2.1 ± 0.2°. Electrochemical corrosion test results showed the corrosion current density of superhydrophobic surface was about 4 orders of magnitude lower than that of bare Cu in 3.5 wt% NaCl solution, indicating that the superhydrophobic surface had superior corrosion resistance. We also discussed the corrosion resistance mechanism of superhydrophobic surface with hierarchical and multi-scale micro/nanostructure. In addition, the as-prepared superhydrophobic surface also demonstrated good mechanochemical and self-cleaning properties, which may greatly facilitate the application in practical conditions.

Anti/de-icing performance of the one-step electrodeposited superhydrophobic surfaces: Role of surface polarity regulated by hydrocarbon radical length

• Superhydrophobic surface is prepared by one-step electrodeposition method. • Polarity of superhydrophobic surface is regulated by hydrocarbon radical length. • [CH 3 (CH 2 ) 16 COO] 3 Ce possesses better non-wettability and anti/de-icing features. • Cerium and –CH 2 group together contribute to the excellent low-polarity. • lower-polarity surface with ultra-low ice adhesion can be sustained by oxide layer. The superhydrophobic surfaces with different polarity regulated by hydrocarbon radical length were fabricated by a facile one-step electrodeposition method in order to survey the effect of surface polarity on anti/de-icing performance. The as-prepared superhydrophobic surface, electrodeposited in the solution composed of Ce(NO 3 ) 3 6H 2 O and stearic acid, displayed higher superhydrophobicity with a contact angle reaching 173.02 ± 1.02° and a rolling angle being only 1.5°. The ideal non-wettability was mainly attributed to the formed micro-nanostructures during the one-step electrodeposition process and the lower-polarity of [CH 3 (CH 2 ) 16 COO] 3 Ce with the extension of –CH 2 length. Furthermore, lower-polarity surface could induce smaller water-adhesion dissipation energy, resulting in the obvious reduction in the contact time (11.8 ms) of an impact droplet. In terms of the anti-icing performance, the icing delay time could reach 612.68 s at −15 ℃, and still had a higher value of 39.12 s even at −40 ℃, which could be also reflected by the statistical data of freezing temperature (-20.27 ℃). An ultra-low ice adhesion of 5.72 kPa was achieved on lower-polarity surface, meanwhile, the surface anti/de-icing cycle durability could be improved by 32% owing to the addition of an oxide layer. Understanding the influencing mechanism of surface polarity on anti/de-icing performance could provide theoretical guidance for the development of passive anti/de-icing technologies in aviation industry field.

An Abrasion Resistant TPU/SH-SiO2 Superhydrophobic Coating for Anti-Icing and Anti-Corrosion Applications

As a passive anti-icing strategy, properly designed superhydrophobic coatings can demonstrate outstanding performances. However, common preparation strategies for superhydrophobic coatings often lead to environmental pollution, high energy-consumption, high-cost and other undesirable issues. Besides, the durability of superhydrophobic coating also plagues its commercial application. In this paper, we introduced a facile and environment-friendly technique for fabricating abrasion-resistant superhydrophobic surfaces using thermoplastic polyurethane (TPU) and modified SiO2 particles (SH-SiO2). Both materials are non-toxicity, low-cost, and commercial available. Our methodology has the following advantages: use of minimal amounts of formulation, take the most streamlined technical route, and no waste material. These advantages make it attractive for industrial applications, and its usage sustainability can be promised. In this study, the mechanical stability of the superhydrophobic surface was evaluated by linear wear test. It is found that the excellent wear resistance of the superhydrophobic coating benefits from the characteristics of raw materials, the preparation strategy, and the special structure. In anti-icing properties test, the TPU/SH-SiO2 coating exhibits the repellency to the cold droplets and the ability to extend the freezing time. The electrochemical corrosion measurement shows that the as-prepared superhydrophobic surface has excellent corrosion resistance that can provide effective protection for the bare Q235 substrates. These results indicate that the TPU/SH-SiO2 coating possesses good abrasion resistance and has great potential in anti-corrosion and anti-icing applications.

Wetting and anti-fouling properties of groove-like microstructured surfaces for architectural ceramics

Contaminants on architectural ceramics have become a major problem in people's lives. Interestingly, superhydrophobic surfaces offer a new avenue for anti-fouling applications. In this work, a UV-laser process for constructing groove-like microstructures on architectural ceramics and subsequent fluoridation treatment were used to create superhydrophobic surfaces. After laser processing, nanoporous structures were generated inside the grooves, while the cracked layer was deposited on the non-irradiated area, building up a micro/nanoscale morphology on the ceramic surface. Moreover, the effects of groove pitch and laser scanning cycle on surface morphology and wettability were investigated. Results indicate that the fluoridated groove-like microstructured surface showed good superhydrophobicity based on the Cassie-Baxter model. Dynamic behavior of water droplets impacting on the as-prepared superhydrophobic surface was studied to verify its low adhesion. Additionally, the superhydrophobic surface exhibited remarkable repellency to various stain liquids and outstanding self-cleaning properties. These findings may contribute to developing anti-fouling applications for the architectural ceramics industry.

Preparation and corrosion resistance of superhydrophobic film by one-step electrodeposition

Superhydrophobic film with cauliflower-like structure was prepared on copper sheet by one-step electrodeposition method. The surface morphology and chemical composition of the superhydrophobic film were characterized by SEM, FTIR, XPS and contact angle measurements. Due to the cauliflower-like hierarchical structure and low surface energy, the as-prepared surface can reach up to a maximum contact angle of 158.3°, and the rolling angle is not more than 7°. Polarization curve was investigated using electrochemical workstation, and the as-prepared superhydrophobic surface showed improved corrosion resistance compared with bare copper.

Fabrication of superhydrophobic micro-nanostructured aluminum alloy surface via a cost-effective processing using an ultra-low concentration of fluoroalkylsilane

Herein, superhydrophobic 4037 aluminum alloy surface with self-cleaning and anti-icing properties has been fabricated by a low-cost processing consisting of HCl/H2O2 treatment and modification of an ultra-low concentration of fluoroalkylsilane. Via a chemical etching, a coral-like hierarchical micro-nano structure has been formed on 4037 aluminum alloy substrate. Then, the wettability of etched surface treated with different levels of fluoroalkylsilane has been investigated. The results show that the etched surface after been modified with petroleum ether containing 20 mg fluoroalkylsilane can result in superhydrophobicity with a water contact angle of 160.8° and a sliding angle of 2.4°. Especially, effects of solvents on the wettability of fabricated surface have also been studied. It is found that alkane such as petroleum ether is suitably used as a solvent for fluoroalkylsilane due to a reduction on fluoroalkylsilane. In addition, obvious self-cleaning and anti-icing behaviors of the as-prepared superhydrophobic surface have been proved, which will extend the further application of aluminum alloy.

Experimental and molecular dynamics simulation study of chemically stable superhydrophobic surfaces

Abstract Experimental and molecular dynamics simulation study was used to clarify the hydrophilicity of substrate surfaces and hydrophobicity of as-prepared surfaces at molecular level. First, an easy one-step approach was utilized to construct superhydrophobic surfaces on different substrates such as steel, aluminum, glass, and silicon wafer. The superhydrophobicity of as-prepared surfaces were contributed to the fluorinated compositions and microstructures. A fluorinated surface was constructed as a model of the as-prepared superhydrophobic surface. Molecular dynamics simulations were utilized to elucidate the anti-wetting mechanism of as-prepared fluorinated surfaces on aluminum substrates. Compared with the compact hydrated layer on the aluminum substrate, the hydrated layer on the fluorinated surface were broader with a lower intensity, confirming the lower attractive force between surface and water molecules. The decreased van der Waals interaction with water molecules contributed to the hydrophobicity of the fluorinated surface. While, in an alkaline solution, the electrostatic interaction had a negative impact on hydrophobicity of a fluorinated surface.

A fluorine-free superhydrophobic silicone rubber surface has excellent self-cleaning and bouncing properties

Superhydrophobic materials have been widely applied in self-cleaning, anti-fouling, anti-corrosion, anti-freezing. However, simple, efficient, environmentally friendly and large-area preparation is still a great challenge in the field of fabrication of superhydrophobic surfaces. In this paper, a simple physical deposition method is adopted to deposit a layer of alumina oxide (Al2O3) particles on the surface of the room temperature vulcanized (RTV) silicone rubber, and remove the excess Al2O3 particles on the surface to obtain the superhydrophobic surface of Al2O3/RTV silicone rubber. The contact angle and rolling angle of the superhydrophobic surface are 156.6° ± 1.1° and 5.1° ± 0.7°, respectively. It is found that the surface roughness of RTV silicone rubber is significantly increased via Al2O3 particles. The analysis of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) demonstrate that the superhydrophobic surface is obtained via constructing rough structure of Al2O3 particles on the RTV silicone rubber surface. In addition, the self-cleaning and droplet bounce tests under different conditions show that the as-prepared superhydrophobic surface has remarkable self-cleaning and droplet bounce properties. Therefore, this method can be employed to simply and effectively fabricate superhydrophobic surfaces in large scale.

Simultaneously spray-assisted assembling reversible superwetting coatings for oil–water separation

Here, superhydrophobic cuprous oxide (Cu 2 O) with hierarchical micro/nanosized structures was synthesized via spray-assisted layer by layer assembling. The as-prepared superhydrophobic meshes with high contact angle (159.6°) and low sliding angle (1°) are covered with Cu 2 O “coral reef” -like micro/nanosized structures. Interestingly, the superhydrophobic mesh surfaces became superhydrophilic again due to the oxidization of Cu 2 O to CuO by annealing at a higher temperature (300 °C). And the superhydrophobic properties would be recovered by heating at 120 °C. Furthermore, the superwetting meshes were applied to design a miniature device to separate light or heavy oil from the water–oil mixtures with excellent separation efficiency. These superwetting surfaces by simultaneously spray-assisted layer by layer assembling technique show the potential application in universal oil–water separation. • The as-prepared superhydrophobic surface is with Cu 2 O coral reef-like micro/nanostructures. • No low surface energy materials have been involved in the method. • The spray deposition process is convenient and suitable for mass production. • The reversible wetting transition is responsive to the temperature. • The mesh can be used to separate different kinds of oils with excellent separation efficiency.

Corrosion inhibition by a superhydrophobic surface on aluminum that was prepared with a facile electrochemical route

A superhydrophobic surface featuring high roughness and low surface energy is designed for effective corrosion protection on aluminum via a facile and cost-effective electrochemical route. The effects of the electrolyte composition and electrodeposition time on the surface wettability were investigated. Moreover, the corrosion resistance performance of the as-prepared superhydrophobic aluminum surface was studied using electrochemical impedance spectroscopy and electrochemical noise techniques. The results show that the superhydrophobic aluminum surface obtained at 2 V for 20 min has a high static water contact angle of 155.8°. Both the average corrosion rate and pitting intensity are remarkably inhibited by the as-prepared superhydrophobic surface on aluminum. Moreover, the static water contact angle for the obtained superhydrophobic surface remains above 150° after exposure to 3.5 wt% NaCl solution for 30 days. This facile and economical superhydrophobic surface, with its excellent anti-corrosion property and stability, shows significant potential for use in industrial applications.

Fabrication of Self-Cleaning Superhydrophobic Surfaces with Improved Corrosion Resistance on 6061 Aluminum Alloys.

Aluminum alloys are widely used, but they are prone to contamination or damage under harsh working environments. In this paper, a self-cleaning superhydrophobic aluminum alloy surface with good corrosion resistance was successfully fabricated via the combination of sand peening and electrochemical oxidation, and it was subsequently covered with a fluoroalkylsilane (FAS) film. The surface morphology, surface wettability, and corrosion resistance were investigated using a scanning electron microscope (SEM), an optical contact angle measurement, and an electrochemical workstation. The results show that binary rough structures and an FAS film with a low surface energy on the Al alloy surfaces confer good superhydrophobicity with a water contact angle of 167.5 ± 1.1° and a sliding angle of 2.5 ± 0.7°. Meanwhile, the potentiodynamic polarization curve shows that the corrosion potential has a positively shifted trend, and the corrosion current density decreases by three orders of magnitude compared with that of the original aluminum alloy sample. In addition, the chemical stability of the as-prepared superhydrophobic surface was evaluated by dripping test using solutions with different pH values for different immersion time. It indicates that the superhydrophobic surface could provide long-term corrosion protection for aluminum alloys. Consequently, the as-prepared superhydrophobic surface has excellent contamination resistance and self-cleaning efficacy, which are important for practical applications.

Bioinspired one step hydrothermal fabricated superhydrophobic aluminum alloy with favorable corrosion resistance

Despite the considerable demand for unique non-wetting superhydrophobic surfaces, simple and scalable one step fabrication approach has rarely been established. Herein, we report a convenient one step hydrothermal strategy for fabrication of superhydrophobic 5083 aluminum alloy (AA5083) surface. The spontaneously formed rough micro-structures and water repellent property can be achieved after pentadecafluorooctanoic acid (PFOA) aqueous solution treatment. The surface topography and chemical compositions were studied by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). The co-existence of flower-like micro-structures and abundant -CF3 and -CF2 groups after one step PFOA hydrothermal treatment contributes to the improved air-liquid interfacial contact area and the eventual anti-wetting behaviors. The as-prepared superhydrophobic AA5083 surface exhibits excellent water flow repellency, stable self-cleaning ability and favorable corrosion resistance. We believe the convenient and effective one step strategy will inspire the large-scale preparation of multifunctional surfaces for widely application scope.

Facile fabrication of robust fluorine-free superhydrophobic cellulosic fabric for self-cleaning, photocatalysis and UV shielding

Self-cleaning, photocatalysis and UV shielding cotton fabric was fabricated through a mild, facile and efficient method via ZnO/polydimethylsiloxane coatings. No fluorinated materials were employed during the preparation process. The modified cotton presented a high superhydrophobicity, with a water contact angle of 160.4° and water shedding angle of 6.0°. The SEM, EDS and XPS tests were used to investigate the differences of microstructures and chemical compositions of fabrics before and after coating. The robustness of the coated fabric was demonstrated in many aspects, such as immersing in acid and basic solutions, different organic solvents and abrasion test. In addition, the as-prepared superhydrophobic surface displayed excellent self-cleaning due to the synthesis function of superhydrophobicity and photocatalysis. The UV durability and UV shielding characteristics were also investigated. These properties promote the multifunctional cotton fabric as a satisfied candidate in various promising fields.

Preparation of Superhydrophobic Steel Surfaces with Chemical Stability and Corrosion

Corrosion seriously limits the long-term application of Q235 carbon steel. Herein, a simple fabrication method was used to fabricate superhydrophobic surfaces on Q235 carbon steel for anticorrosion application. The combination of structure and the grafted low-surface-energy material contributed to the formation of superhydrophobic steel surfaces, which exhibited a water contact angle of 161.6° and a contact angle hysteresis of 0.8°. Meanwhile, the as-prepared superhydrophobic surface showed repellent toward different solutions with pH ranging from 1 to 14, presenting excellent chemical stability. Moreover, the acid corrosive liquid (HCl solution with pH of 1) maintained sphere-like shape on the as-prepared superhydrophobic surface at room temperature, indicating superior corrosion resistance. This work provides a simple method to fabricate superhydrophobic steel surfaces with chemical stability and corrosion resistance.

Preparation of mechanically durable superhydrophobic aluminum surface by sandblasting and chemical modification

A facile method for the fabrication of a robust superhydrophobic aluminum surface with a water contact angle of 156 ± 2° and a sliding angle of 3° is described in this research. The prepared aluminum surface obtained a hierarchical structure and low surface energy by combination of sandblasting and chemical modification. The as-prepared superhydrophobic aluminum surface exhibited excellent mechanical durability, withstanding abrasion by 1000-grit sandpaper at an applied pressure of 5 kPa and a travel distance of 800 cm. In addition, the superhydrophobic aluminum surface showed superior thermal stability when heated to 240 °C. Moreover, the superhydrophobic aluminum surface possessed a good self-cleaning effect. The low-cost and facile method provides a suitable strategy to fabricate a robust superhydrophobic metallic surface with mechanical durability, thermal stability, self-cleaning effect, and anti-fouling ability appropriate for extensive industrial applications.