Superhydrophobic Aluminum Research Articles

Robust superhydrophobic aluminum alloy surfaces with anti-icing ability, thermostability, and mechanical durability

In this study, we develop an efficient approach to fabricate superhydrophobic aluminum alloy samples. The superhydrophobic aluminum alloy sample is prepared by combining high-speed wire electrical discharge machining, a short-time chemical etching method, with a modification treatment. The prepared superhydrophobic aluminum sample possesses a contact angle of 158.6 ± 1.3° and a sliding angle of below 1°. The introduction of chemical etching can shorten the preparation time from 20 to 8 h. The prepared superhydrophobic aluminum alloy sample is durable enough to endure the harsh conditions to which some aluminum alloy parts are subjected. Its excellent anti-icing ability is confirmed by the freezing delay test and low-temperature durability test under overcooled conditions. In addition, the prepared superhydrophobic aluminum alloy sample shows superior thermostability and high-temperature durability in the range of 180∼240 °C. Moreover, the prepared superhydrophobic aluminum alloy sample exhibits outstanding mechanical durability that can endure abrasion by 1000-grit sandpaper at 20 kPa for 260 cm. It also can withstand 11 vertical impacts by 200 g weight dropped from 12 cm with the weight falling on the sample at a rate of ∼15.50 cm/s. The introduction of the chemical etching greatly shortens the preparation time and the as-prepared superhydrophobic aluminum alloy sample exhibited excellent durability, which may widen the application range of superhydrophobic aluminum alloys.

Propelling liquids on superhydrophobic surfaces with superhydrophilic diverging grooves

The autonomous locomotion of liquids on free solid surfaces is becoming common in many industrial applications. To propel liquids uphill, superhydrophilic diverging grooves at varying angles of divergence 2, 4, 6, 8, and 10° were fabricated on superhydrophobic aluminum surfaces in this study. Experiments on propelling liquids were performed on specially designed surfaces subject to different angles of inclination, and the correlation between propelling capacity and the angles of divergence is examined. The results show that the propelling capacity can be enhanced by increasing the angle of divergence. To propel more liquids uphill, a superhydrophobic surface with a superhydrophilic diverging groove at an angle of divergence of 10° is recommended. To achieve a greater uphill height, designing a surface with an angle of divergence larger than 6° is sufficient. Superhydrophilic and superhydrophobic properties are discussed, and the mechanism of propelling is described. Furthermore, the key influence factors on the uphill height are theoretically revealed.

Multiscale corrosion analysis of superhydrophobic coating on 2024 aluminum alloy in a 3.5 wt% NaCl solution

Abstract

Wetting and tribological properties of superhydrophobic aluminum surfaces with different water adhesion

In this article, a facile and efficient nanosecond laser processing method was carried out to construct a grid of microgrooves on an aluminum surface. After modification with low surface energy materials, various superhydrophobic surfaces with different water adhesion are obtained. The wetting properties of the obtained samples could be regulated by adjusting the number and line spacing (LS) of laser processing steps. The contact angle of the obtained superhydrophobic samples increased with the decrease in LS, while the sliding angle showed the opposite trend. Increasing the number of laser processing steps is beneficial to increase the contact angle and reduce the sliding angle. The wetting mechanism was analyzed to explain the cause of change in the wetting behaviors. The tribological tests showed that the surface textures of superhydrophobic samples improved their tribological properties. What is more, whether it is under dry friction or water lubrication conditions, the obtained superhydrophobic samples with large LS have good anti-friction and wear-resistant ability. The advantages of the facile preparation and excellent tribological properties will definitely expand the use of laser-machined superhydrophobic surfaces.

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.

Characterization of self-cleaning properties on superhydrophobic aluminum surfaces fabricated by direct laser writing and direct laser interference patterning

Self-cleaning ability on technical surfaces can increase the added value of a product. A common path to achieve this property is making the surface superhydrophobic so that water droplets can roll down, picking up dirt particles. In this contribution, the self-cleaning efficiency of Al surfaces structured with direct laser writing (DLW), direct laser interference patterning (DLIP) and a combination of both technologies was quantitatively determined. This was performed by developing a characterization method, where the treated samples are firstly covered with either MnO2 or polyamide micro-particles, then tilted by 15° and 30° and finally washed applying up to nine water droplets (10 µl) over the contaminated surfaces. Then, an optical analysis by image processing of the remaining contamination particles on the textured surfaces was realized after each droplet rolled over the surface. The DLIP textures showed the best performance, allowing the removal of more than 90% of the particles after just three droplets were released. High-speed videos and scanning electron microscopy characterization allowed a deeper understanding on the cleaning behavior and on the relationship between surface microstructure and particle size and shape.

Control and Patterning of Various Hydrophobic Surfaces: In-situ Modification Realized by Flexible Atmospheric Plasma Stamp Technique

Wettability plays a vital role in fundamental researches and practical applications. Wettability control and patterning have been widely studied in various fields. Although researches have grown rapidly, the methods are still restricted by limitations including complicated processes, high equipment requirements and shortage of methods to treat complex surfaces. Here we report a simple, low cost, array-based wettability control and patterning method via in-situ modification by flexible plasma stamp. Wettability control and patterning on surfaces of superhydrophobic aluminum, superhydrophobic PDMS and silicon, even plant leaf and fruit are achieved. The relationships between the wettability and the treatment time are investigated. We elucidate that the wetting states can also be reversible. The surface modification mechanism of in-situ plasma treatment is further investigated. Utilizing the step by step treatment, gradient and arbitrary wettability patterning on surfaces have been obtained. Notably, the patterned wettability on the inner surface of a tube has been realized, which has never been reported. Finally, in-situ wettability patterning is applied to achieve microfluidics channels on the inner surface of superhydrophobic tube. This work will bring new insights into the study of wetting field and stimulate more applications on wettability control and patterning.

Superhydrophobic Self-Assembled Silane Monolayers on Hierarchical 6082 Aluminum Alloy for Anti-Corrosion Applications

In this work, a two-stage methodology to design super-hydrophobic surfaces was proposed. The first step consists of creating a rough nano/micro-structure and the second step consists of reducing the surface energy using octadecyltrimethoxysilane. The surface roughening was realized by three different short-term pretreatments: (i) Boiling water, (ii) HNO3/HCl etching, or (iii) HF/HCl etching. Then, the surface energy was reduced by dip-coating in diluted solution of octadecyltrimethoxysilane to allow the formation of self-assembled silane monolayers on a 6082-T6 aluminum alloy surface. Super-hydrophobic aluminum surfaces were investigated by SEM-EDS, FTIR, profilometry, and contact and sliding angles measurements. The resulting surface morphologies by the three approaches were structured by a dual hierarchical nano/micro-roughness. The surface wettability varied with the applied roughening pretreatment. In particular, an extremely high water contact angle (around 180°) and low sliding angle (0°) were evidenced for the HF/HCl-etched silanized surface. The results of electrochemical tests demonstrate a remarkable enhancement of the aluminum alloy corrosion resistance through the proposed superhydrophobic surface modifications. Thus, the obtained results evidenced that the anti-wetting behavior of the aluminum surface can be optimized by coupling an appropriate roughening pretreatment with a self-assembled silane monolayer deposition (to reduce surface energy) for anticorrosion application.

레이저 가공과 열처리로 제작된 초소수성 알루미늄 합금 표면의 부식 저항 연구

레이저 가공과 열처리로 제작된 초소수성 알루미늄 합금 표면의 부식 저항 연구

Easy and Fast Fabrication of Self-Cleaning and Anti-Icing Perfluoroalkyl Silane Film on Aluminium

A combination of the chemical etching process in FeCl3 solution and chemical surface grafting by immersion in ethanol solution containing 1H,1H,2H,2H-perfluorodecyltriethoxysilane is a viable route to achieve a hierarchical surface topography and chemical bonding of silane molecules on an aluminium surface leading to (super)hydrophobic characteristics. Characterisation of untreated and treated aluminium surfaces was carried out using contact profilometry, optical tensiometry, scanning electron microscopy coupled with energy-dispersive spectroscopy and X-ray photoelectron spectroscopy to define the surface topography, wettability, morphology and surface composition. Additionally, the dynamic characteristics were evaluated to define bouncing and the self-cleaning effect. A thermal infrared camera was employed to evaluate anti-icing properties. The micro/nano-structured etched aluminium surface grafted with perfluoroalkyl silane film showed excellent superhydrophobicity and bounce dynamics in water droplet tests. The superhydrophobic aluminium surface exhibited the efficient self-cleaning ability of solid pollutants as well as improved anti-icing performance with melting delay.

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.

A Novel Simple Anti-Ice Aluminum Coating: Synthesis and In-Lab Comparison with a Superhydrophobic Hierarchical Surface

A simple process to obtain a slippery surface with anti-ice and ice-phobic properties has been developed and characterized in laboratory. The coating is realized by growing a nanostructured pseudo-boehmite on an aluminum substrate and applying an environmentally compatible final functionalization consisting of a fluorine-free oligomeric short-chain alkylfunctional silane. The resulting surface is conceptually similar to a slippery liquid infused porous surface (SLIP) material, but the porous infrastructure is inorganic and the process to generate it is very simple, rapid and economic. The coating performance in terms of hydrophobicity at room and low temperatures, ice nucleation temperature and ice adhesion forces were assessed in laboratory. Moreover, hydrophobicity persistence was tested after prolonged immersion in acid, basic and saline solutions while the durability of ice-phobic behavior was assessed by repeated shear stress tests. Results are compared with those of a superhydrophobic hierarchical aluminum surface obtained with a fluorinated siloxane. The novel coating shows very good anti-ice properties and relevant durability, with some differences from the fluorinated surface. The novel slippery coating process is promising for industrial applications, also taking into account its environmental compatibility, simplicity and low cost.

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.

Fabrication of super-hydrophobic surface on aluminium substrate and a study of surface frosting behaviours

Frosting is common found natural phenomenon in late autumn or early spring, which sometimes brings unwanted effects or even disaster to human. With the development of science and technology, frosting may to some extend be mitigated by hydrophobic surfaces. Micro-Nanostructure was gained via chemical etching on aluminium surface. The surface was further modified by low surface energy polymer coating to form a very thin nano-layer on the surface. A kind of fluoroalkylsilane is used as the coating polymer. After fluorination treating, the aluminium surface become super hydrophobic with water contact angles more than150°. The surface was observed to be configured with plateaus and caves of micro-Nanoscale. In subcooled environments, frosting experiment was carried out on the surface of aluminium rods and aluminium sheets using humidifier to supply the water droplets. The comparison of the quantity of frost formed on the super-hydrophobic and untreated aluminium surfaces was conducted in the present work. And the quantity of frost formed on aluminium surfaces of different contact angles was compared. The results show that super-hydrophobic aluminium surfaces have obvious advantages in inhibiting frost. Besides, the contact angle has evident influences on restraining frost. Therefore, super-hydrophobic surfaces may serve as an effective means in decreasing the accumulation of frost on outside solid surfaces.

Robust transferrable superhydrophobic surfaces

ABSTRACTIn this study, we present a simple and inexpensive method for enhancing the robustness of aluminium-based superhydrophobic surfaces and identify a method for reliably evaluating the degradation of such surfaces. A superhydrophobic aluminium surface was prepared by a chemical etching and hydrophobic coating. Hydrophobized aluminium particles on the surface were then transferred to adhesive strips. Scanning electron microscopy and contact angle measurements were conducted before and after water-jet and mechanical abrasion tests to evaluate the robustness of the superhydrophobic surfaces. Following the tests, the advancing contact angle remained unchanged while the receding contact angle depended on the adhesive strength of the surface. The receding contact angle on the superhydrophobic adhesive strip was found to decrease at a reduced rate, as compared to the original superhydrophobic aluminium surface. The receding contact angle was also measured to increase with the adhesive strength of the strips, demonstrating better overall superhydrophobic performance.

Efficient water scavenging by cooling superhydrophobic surfaces to obtain jumping water droplets from air

Dew collection is significant in harvesting water and relieving water shortages in arid regions. However, current methods for collecting dew or steam are mainly focusing on the millimeter-sized droplets condensed on the superhydrophobic surfaces. Here, we present a concept for harvesting micro droplets that can spontaneously bounce on the cooling superhydrophobic aluminum surface with randomly micro-nano composite structures, which were fabricated by using a two-step surface structural process. Moreover, an integrated device has been developed, which consists of a triboelectric nanogenerator and the superhydrophobic aluminum sheet. We experimentally explained that the triboelectric nanogenerator, which provides an external electric field by converting wind energy to electric energy with DC voltage pulse peaks of about 60 V, can be utilized to enhance the collection capacity of the jumping water droplets.

Fabrication of robust and durable slippery anti-icing coating on textured superhydrophobic aluminum surfaces with infused silicone oil

A facile and durable biomimetic slippery anti-icing coating was prepared by infusing nontoxic and inexpensive lubricating silicone oil into superhydrophobic dual-scale micro/nano-structured (MNS) aluminum surfaces. Superhydrophobic surfaces were fabricated via the combination of simple chemical etching and anodization, followed by surface modification with poly(dimethylsiloxane) (PDMS). Compared to superhydrophobic coatings, silicone oil-infused polydimethylsiloxane (SOIP) coating displays a low ice-adhesion strength of 22 ± 5 kPa on the structured surface. Moreover, the SOIP coating sustained low ice-adhesion strength (35 ± 15 kPa) even when the temperature was lowered to −25 °C. The MNS-surface exhibits excellent durability, showing a low ice-adhesion (108 kPa) after 20 icing/de-icing cycles and long-term icephobicity (55 ± 13 kPa) after four months' exposure in ambient environment. We also examined the influence of surface morphology on ice-adhesion strength, the SOIP modified MNS-surface displays better anti-icing properties compared to a nano-structured (NS) surface under harsh conditions; icing/deicing and abrasion cycles. The MNS-surface act as reservoir to hold the excess amount of oil, thus reducing the loss of lubricant during icing/deicing cycles. The proposed technique is very simple and cost-effective, and most importantly it can be applied for production of durable and scalable anti-icing coatings for various practical applications.

Oil-Repellent and Corrosion Resistance Properties of Superhydrophobic and Superoleophobic Aluminum Alloy Surfaces Based on Nanosecond Laser-Textured Treatment

As two typical special wettability materials, superhydrophobic and superoleophobic surfaces are the most widely studied interfaces because of their excellent water-or oil-repellent ability. However, how to use a simple strategy to obtain those surfaces is still a huge challenge. On the other hand, corrosion tend to occur while using metallic materials, resulting in poor performance of metallic equipment and even serious safety hazards. In this work, a one-step strategy of nanosecond laser ablation was presented to construct the microstructures acquired by superhydrophobic and superoleophobic aluminum alloy surfaces. The superhydrophobic and superoleophobic properties of microstructured surfaces were obtained via high temperature and fluorosilane treatments on laser-processed surfaces, respectively, and the oil-repellent and corrosion resistance properties of both substrates were studied. The potentiodynamic polarization test shows that the superoleophobic surface had a better corrosion resistance than the superhydrophobic surface, which will provide an effective protection for the bare aluminum alloy. Meanwhile, the superoleophobic surface had good chemical stability. It is believed that the nanosecond laser technology can offer an effective strategy for constructing the microstructures acquired by large-area superhydrophobic and superoleophobic surfaces on aluminum alloy materials.

An environmentally-friendly method to fabricate extreme wettability patterns on metal substrates with good time stability

Wettability patterns have significant application potential in liquid transportation and water collection. Plasma hydrophilization is high-efficient and less-destructive, and has been widely used for preparing wettability patterns. However, the plasma-treated surfaces tend to recover to its original wettability, causing invalidation of the patterns. As a green treatment method, boiled water treatment could construct nanostructures, which is favorable for hydrophilicity-retaining; while the hydrophilization effect of plasma treatment would promote the reaction. Therefore, it should be possible to combine plasma and boiled water treatments to prepare long-lasting wettability patterns. In this paper, superhydrophobic aluminum surfaces were modified by plasma jet followed by boiled water treatment. The time stability, microstructures and chemical compositions of the treated surfaces were investigated by testing contact angles, scanning electron microscope, X-ray diffractometer, and X-ray photoelectron spectroscopy. The surfaces treated by plasma jet and boiled water could retain superhydrophilicity for a long time under various storage conditions, including normal ambient, high temperature or high humidity. On the basis of this technique, long-lasting patterns could be prepared on different metal substrates. The green method proposed is expected to have promising application potential in fabricating wettability patterns and lab-on-chip devices, especially for those used in severe conditions.

Temperature-based adhesion tuning and superwettability switching on superhydrophobic aluminum surface for droplet manipulations

Superhydrophobic surfaces with tunable water adhesion and adjustable wettability have the capacity to manipulate water droplets under complicated conditions and, therefore, have great prospects in various domains. Hence, developing a facile method to prepare highly stable superhydrophobic surfaces with tunable water adhesion and adjustable wettability is of great importance. Herein, we prepare the superhydrophobic aluminum surface by combining laser etching and stearic acid modification. The variations of water contact angle, water sliding angle and water adhesive force with temperature of the prepared surface are characterized during the adhesion tuning process to investigate its temperature-responsive characteristics. A low/high adhesion switching of water on the prepared surface is subsequently achieved under alternating temperature. In addition, a facile approach is designed to achieve the superwettability switching process (from superhydrophobic state to superhydrophilic state) on the prepared surface. The prepared superhydrophobic surface displays excellent recoverability, stability and repeatability in the adhesion switching process and the superwettability switching process, even after being cycled for 10 times.