Controlled fabrication of transparent and superhydrophobic coating on a glass matrix via a Green method

A facile, green method was explored for the organic-inorganic complex coating with superhydrophobic and transparent property on glass matrix. The glass surface was firstly treated with polyethylene glycol (PEG) and SiO₂ organic-inorganic solution and then modified with a layer of 1,1,1,3,3,3-Hexamethyldisilazane (HMDS). The glass samples were characterized by scanning electron microscopy (SEM), water contact angle (CA) measurement, and UV–Vis spectrophotometry. The results showed that the optical transmission over the visible range up to 89 % (in reference to 100 % transmission defined by bare glass substrate), and the water CA of the film reached 168^°. Superhydrophobic coatings with excellent optical transmittance will have potential applications in our daily life.     

Electrospun polystyrene fibres on TiO<Subscript>2</Subscript> nanostructured film to enhance the hydrophobicity and corrosion resistance of stainless steel substrates

A dual layer of dip-coated TiO₂ film (top layer) and electrospun polystyrene (bottom layer) was coated on stainless steel (SS) substrates. The morphological and structural studies were performed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). Their hydrophobicity and corrosion resistance were also investigated using contact angle (CA) and electrochemical corrosion tests in acidic and salt solutions, respectively. Contact angle results showed that the naturally hydrophilic TiO₂/SS sample (CA ～ 66^°) turned into a superhydrophic surface (CA ～ 148^°) when it was covered by polystyrene fibres (PS /TiO₂ /SS). This observation can be attributed to the intrinsic hydrophobicity of organic polystyrene fibres (due to their low surface energy) and also to the existence of trapped air bubbles between fibres. Electrochemical corrosion tests showed that the corrosion rate was substantially decreased by using a protective bilayer (PS /TiO₂) from 33 to 0.39 mV /y for bare SS sample and from 0.01 to 0.003 mV /y for PS /TiO₂ /SS sample in 1 M salt and acidic solutions, respectively. The superhydrophobic protective layer forms an obstacle against ionic exchange interactions. Therefore, it slows down the breaking of the surface oxidic layer on the metal substrate and prevents the metallic surface underneath from further corrosion.     

Fabrication of nanopatterned sapphire substrates by annealing of patterned Al thin films by Laser Interference Lithography

Nanopatterned sapphire substrates were fabricated by annealing of patterned Al thin films. Square-patterned Al thin films with the diagonal length of 600 nm, period of 1 um and height of ～200 nm were obtained by the Laser Interference Lithography and Reactive Ion Etching. Patterned Al thin films were subsequently subjected to dual stage annealing due to the melting temperature of Al thin films (660 ^°C). The first comprised a low temperature oxidation anneal. The hillocks formation on Al thin films was minimized with an oxidation annealing at 450 ^°C for 24 h. The little change in the morphology of patterned Al thin films was observed at 450 ^°C for 24 h. This was followed by a high temperature annealing to induce growth of the underlying sapphire single crystal to consume the oxide layer. The SEM results show the patterns were retained on sapphire substrates after high temperature annealing at less than 1200 ^°C. The XRD and Raman results reveal that the orientation of island patterns by dual stage annealing of patterned Al thin films for 24 h at 450 ^°C, and 1 h at 1000 ^°C, was the same as that of the sapphire (0001) substrates.     

自清洁功能的超疏水微/纳米结构铜网用于高效的分离油水

本文介绍了一种简便的方法制备n-十二烷基三甲氧基硅烷@三氧化钨包覆的超亲油超疏水的铜网.所制备的铜网显示了较为突出的超亲油和超疏水性能,该铜网的水接触角大约有154.39°,而油接触角接近于0°.实验利用了各种有机溶剂和水的混合物对所制备网膜进行分离性能测试,结果表明所得涂覆铜网的油水分离效率高达99.3V,并且水的通量大约为9962.3 L·h~(-1)·m~(-2).所制备的铜网具有良好的稳定性,经过10次分离循环后分离效率仍然保持在90%以上.由于三氧化钨优异的光催化降解性能,所制备铜网具有自清洁能力.因此,被润滑油污染的网膜可以恢复超疏水性,而这种自清洁性使所制网膜可以反复用于油水分离.     

Electrochemical machining of super-hydrophobic Al surfaces and effect of processing parameters on wettability

Super-hydrophobic aluminum (Al) surfaces were successfully fabricated via electrochemical machining in neutral NaClO₃ electrolyte and subsequent fluoroalkylsilane (FAS) modification. The effects of the processing time, processing current density, and electrolyte concentration on the wettability, morphology, and roughness were studied. The surface morphology, chemical composition, and wettability of the Al surfaces were investigated using scanning electron microscopy (SEM) equipped with energy-dispersive spectroscopy (EDS), white-light interferometry, roughness measurements, X-ray diffraction (XRD), Fourier-transform infrared spectrometry (FTIR), and optical contact angle measurements. The results show that hierarchical rough structures and low surface energy films were present on the Al surfaces after electrochemical machining and FAS modification. The combination of the rough structures and the low surface energy materials plays a crucial role in achieving super-hydrophobicity. Compared with the anodic oxidation and chemical etching method, the method proposed in our work does not require strong acid or alkali, and causes less harm to the environment and operators but with high processing efficiency. The rough structures required by the super-hydrophobic surfaces were obtained at 30-s processing time and the best super-hydrophobicity with 164.6^° water contact angle and 2^° tilting angle was obtained at 360 s. The resulting super-hydrophobic Al surfaces have a long-time stability in air and an excellent resistance to corrosive liquids.     

A novel and expeditious method to fabricate superhydrophobic metal carboxylate surface

This article has presented a novel method to fabricate superhydrophobic metal carboxylate surface on substrates like copper, ferrum, etc. This method markedly shortened the fabrication time to less than one second. The superhydrophobic effect is even better that the contact angle (CA) is 170±1° and the sliding angle (SA) <2°. Scanning electron microscopy (SEM) images showed micro-nano flower-like structures. Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS) confirmed that the flower-like structures are composed of Cu[CH₃(CH₂)₁₂COO]₂. The ethanol solution containing fatty acid and metal salt plays a key role in this method. This method has tremendous potentials in industrial production of superhydrophobic materials.     

A simple fabrication method for mechanically robust superhydrophobic surface by hierarchical aluminum hydroxide structures

Superhydrophobic surfaces with uniformly superhydrophobic surface where nano-scale structures were fabricated by alkali surface modification method and self-assembled monolayer coating. To enhance mechanical durability of the superhydrophobicity, we propose the fabrication process for dual-scale hierarchical structures combining both microstructure via sandblasting techniques and the nanostructured aluminum hydroxide layer. The superhydrophobic surfaces fabricated by both methods exhibited a high water contact angle and very low contact angle hysteresis. By forming the hierarchical structure, the mechanical durability of superhydrophobic aluminum hydroxide surface was improved. The resulting hierarchical structures are suitable for diverse applications of aluminum in various industrial areas, including self-cleaning, anti-frosting, and microfluidic devices for rigorous environments.     

A novel method to fabricate superhydrophobic surfaces based on well-defined mulberry-like particles and self-assembly of polydimethylsiloxane

A superhydrophobic surface was obtained by combining application of CaCO₃/SiO₂ mulberry-like composite particles, which originated from violent stirring and surface modification, and self-assembly of polydimethylsiloxane. Water contact angle and sliding angle of the superhydrophobic surface were measured to be about 164 ± 2.5° and 5°, respectively. The excellent hydrophobicity is attributed to the synergistic effect of micro-submicro-nano-meter scale roughness (fabricated by composite particles) and the low surface energy (provided by polydimethylsiloxane). This procedure makes it possible for widespread applications of superhydrophobic film due to its simplicity and practicability.     

Fabrication and surface characterization of biomimic superhydrophobic copper surface by solution-immersion and self-assembly

Biomimic superhydrophobic surfaces with contact angle greater than 150° and low sliding angle on copper substrate were fabricated by means of a facile solution immersion and surface self-assembly method. The scanning electron microscopy showed a nanoneedle structure copper surface with sporadic flower-like aggregates after treatment with sodium hydroxide and potassium persulfate solution. X-ray photoelectron spectroscopy and X-ray diffraction results confirmed that the formed nanoneedles were crystallized Cu(OH)₂. And the hydrophilic Cu(OH)₂ surface can be further modified into superhydrophobic through surface self-assembly with dodecanoic acid.     

Superhydrophobic alumina surface based on stearic acid modification

A novel superhydrophobic alumina surface is fabricated by grafting stearic acid layer onto the porous and roughened aluminum film. The chemical and phase structure, morphology, and the chemical state of the atoms at the superhydrophobic surface were investigated by techniques as FTIR, XRD, FE-SEM, and XPS, respectively. Results show that a super water-repellent surface with a contact angle of 154.2° is generated. The superhydrophobic alumina surface takes on an uneven flowerlike structure with many nanometer-scale hollows distribute in the nipple-shaped protrusions, and which is composed of boehmite crystal and γ-Al₂O₃. Furthermore, the roughened and porous alumina surface is coated with a layer of hydrophobic alkyl chains which come from stearic acid molecules. Therefore, both the roughened structure and the hydrophobic layer endue the alumina surface with the superhydrophobic behavior.     

Investigation the effect of lattice angle on the band structure in 3D phononic crystals with rhombohedral(II) lattice

In this paper, the propagation of acoustic waves in the phononic crystals (PC) of 3D with rhombohedral(II) lattice is studied theoretically. The PC are constituted of nickel spheres embedded in epoxy. The calculations of the band structure and density of states are performed with the plane wave expansion method in the irreducible part of the Brillouin zone (BZ). In this study, we analyze the dependence of the band structures inside (the complete band gap width) and outside the complete band gap (negative refraction of acoustic wave) on the lattice angle in the irreducible part of the first BZ. Also the effect of lattice angle has been analyzed on the band structure of the ( \( \bar{1}10 \) ) and (122) planes. Then, the equifrequency surface is calculated for the high symmetry point in the [111] and [100] directions. The results show that the maximum width of AEBG (0.022) in the irreducible part of the BZ of RHL2 is formed for (105^°) and no AEBG is found for γ > 150^°. Also, the maximum of the first and second AEBG width are 0.1076 and 0.0523 for γ = 133^° in the ( \( \bar{1}10 \) ) plane and the maximum of the first and second AEBG width are 0.1446 and 0.0998 for γ = 113^° in the (122) plane. In addition, we have found that frequencies in which negative refraction occurs is constant for all lattice angles.     

超疏水聚合物表面的水滴蒸发模拟

基于质量守恒和Fick第一定律，模拟了水滴在超疏水聚合物表面的蒸发全过程．研究从以往的接触角<90±扩展到>150±，液滴形貌扩展为椭球球帽模型进行疏水表面蒸发模拟．水滴在超疏水PC和FPU/PMMA表面蒸发的实验结果显示，计算的椭球球帽模型可以更好的反映出液滴接触角和高度的变化情况，并且不同聚合物表面接触角的相同变化趋势也揭示出微-纳二级结构表面结构不仅影响液滴接触角，也影响液滴蒸发模式．     

The Abrasion Behavior and Mechanisms of a Superhydrophobic Surface Comprising Styrene Butadiene Rubber

The microprotuberances of superhydrophobic surfaces are easily destroyed during a friction cycle, resulting in invalidation of superhydrophobicity, because they are then loaded with pressure and shearing stress. Thus, the abrasion-resistance of superhydrophobic surfaces is the main barrier preventing their wide application. Elastic microprotuberances will be compressed and collapsed by elastic deformation to avoid being broken during a friction cycle, and the deformation will rebound to renew the original surface structure when the load is withdrawn. A superhydrophobic surface comprising styrene butadiene rubber (SBR) was fabricated via template replication in the research described here, with a water contact angle up to 160°. Friction testing was then used to characterize the abrasion resistance of the surface; the contact angle remained more than 139° even after being loaded with 4.4 KPa or 6.87 KPa and rubbed by a smooth metal surface at 18 cm/s for 10,000 times. Scanning electron microscopy was used to characterize the change of morphology before and after the friction testing and to explain the abrasion mechanism.     

Controlled growth of standing Ag nanorod arrays on bare Si substrate using glancing angle deposition for self-cleaning applications

A facile approach to manipulate the hydrophobicity of surface by controlled growth of standing Ag nanorod arrays is presented. Instead of following the complicated conventional method of the template-assisted growth, the morphology or particularly average diameter and number density (nanorods cm^?2) of nanorods were controlled on bare Si substrate by simply varying the deposition rate during glancing angle deposition. The contact angle measurements showed that the evolution of Ag nanorods reduces the surface energy and makes an increment in the apparent water contact angle compared to the plain Ag thin film. The contact angle was found to increase for the Ag nanorod samples grown at lower deposition rates. Interestingly, the morphology of the nanorod arrays grown at very low deposition rate (1.2 Å?sec^?1) results in a self-cleaning superhydrophobic surface of contact angle about 157° and a small roll-off angle about 5°. The observed improvement in hydrophobicity with change in the morphology of nanorod arrays is explained as the effect of reduction in solid fraction within the framework of Cassie–Baxter model. These self-cleaning Ag nanorod arrays could have a significant impact in wide range of applications such as anti-icing coatings, sensors and solar panels.     

Defect-dominated optical emission and enhanced ultraviolet photoconductivity properties of ZnO nanorods synthesized by simple and catalyst-free approach

We report on the defect-dominated light emission and ultraviolet (UV) photoconductivity characteristics of ZnO nanorods (NRs) fabricated using a facile, cost-effective, and catalyst-free thermal decomposition route under varying reaction temperatures. The morphological and structural studies reveal the formation of homogeneous quality nanorods in large scale at the highest reaction temperature of 600 ^°C. The luminescence feature of the nanorods is dominated by the defect related emission over the typical band edge emission. The variation of band-edge and native defect-related emission response of the samples has been correlated to the morphology and microstructure. In photoconductivity studies, the I–V characteristics of the ZnO NRs prepared at different reaction temperatures in dark and under UV illumination (λ=365 nm) follow the power law, i.e., IαV ^r . An enhanced ultraviolet photodetection has been observed in the nanorods fabricated at the highest reaction temperature of 600 ^°C. The sample prepared at highest reaction temperature of 600 ^°C exhibits UV photosensitivity value (photo-to-dark current ratio) of around 1.18×10³, which is much higher in magnitude compared to that of the samples prepared at lower reaction temperatures. The enhanced photoconductivity may be assigned to the development of uniformity and homogeneity of the nanorods. Further development of such ZnO nanostructures can form the basis of promising prototype luminescent and UV photodetecting devices.     

The conversion of wettability in transparent conducting Al-doped ZnO thin film

We report on the systematic changes of surface wettability in one of the most promising transparent conducting oxide materials, Al-doped ZnO (AZO) thin films. It was revealed that the characteristic surface wettability, which would make a key role in adhesion with other layers of optoelectronic device, can be largely changed by Al concentrations and film growth temperature. Keeping the electrical conductivity constant, the water contact angle (WCA) of a 2 mol% AZO film was changed by about 50 ^°C depending on the surface roughness. In the samples grown at 300 ^°C, the roughness enhancement was large and a hydrophobic surface formed, whereas in the samples grown at 500 ^°C a hydrophilic surface formed. We attributed the variation in surface wettability with growth temperature to changes in surface morphology. This result suggests that 2 mol% Al doping concentration can be considered as a critical concentration in changing of surface morphology of AZO as well as in electrical properties.     

Fabrication of superhydrophobic wood surface by a sol-gel process

The superhydrophobic wood surface was fabricated via a sol-gel process followed by a fluorination treatment of 1H, 1H, 2H, 2H- perfluoroalkyltriethoxysilanes (POTS) reagent. The crystallization type of silica nanoparticles on wood surface was characterized using X-ray diffraction (XRD), the microstructure and chemical composition of the superhydrophobic wood surface were described by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS), the bonding force between the silica nanoparticles and POTS reagent was analyzed by Fourier transform infrared spectroscopy (FT-IR) and the superhydrophobic property of the treated sample was measured by contact angle (CA) measurements. An analytical characterization revealed that nanoscale silica spheres stacked uniformly over the wood surface, and with the combination of the high surface roughness of silica nanoparticles and the low surface free energy film of POTS on wood surface, the wood surface has turned its wetting property from hydrophilic into superhydrophobic with a water contact angle of 164° and sliding angle less than 3°.     

Fabrication of superhydrophobic coating via a facile and versatile method based on nanoparticle aggregates

Herein, we report a facile and low cost method for the fabrication of superhydrophobic surface via spin coating the mixture of polydimethylsiloxane precursor (PDMS) and silicon dioxide (SiO₂) nanoparticles. The surface hydrophobicity can be well tuned by adjusting the weight percent of PDMS and SiO₂. The water contact angle (WCA) can increase from 106.8 ± 1.2° on PDMS film to 165.2 ± 2.3° on PDMS/SiO₂ coating, companying with a change from adhering to rolling which was observed from tilting angle (TA) characterization. Multi-scale physical structures with SiO₂ nanoparticle aggregates and networks of SiO₂ nanoparticle aggregates are characterized by scanning electron microscopy (SEM) and atomic force microscope (AFM), and they can be observed more clearly from the AFM images treated with software (WSxM). Then the relationship between surface hydrophobicity and structures is further discussed based on Wenzel and Cassie models, indicating that the appearance of networks of nanoparticle aggregates is important in the Cassie state. The superhydrophobic coating can keep the superhydrophobicity at least for one month under environment conditions and readily regenerate after mechanical damage. Additionally, the superhydrophobic coating can be fabricated using other methods including dip coating, spray coating and casting. Thus, a large area of superhydrophobic coatings can be easily fabricated. Therefore the range of possible applications for these facile and versatile methods can be expanded to various actual conditions.     

Facile method to prepare stable superhydrophobic Co3O4 surface

A facile and novel method was developed to fabricate rough Co₃O₄ surface with hierarchical micro- and nanostructures by the combination of simple solid state reactions and coating process. After modification with stearic acid, a superhydrophobic surface with water contact angle of 155 ± 1.8° and sliding angle of 2° was obtained. The superhydrophobic Co₃O₄ surface remained superhydrophobic property in a wide pH range from 3 to 14. The superhydrophobic Co₃O₄ surface also showed excellent self-cleaning property and high stability in ambient environments.     

Superhydrophobic surfaces fabricated by microstructuring of stainless steel using a femtosecond laser

Fabrication of superhydrophobic surfaces induced by femtosecond laser is a research hotspot of superhydrophobic surface studies nowadays. We present a simple and easily-controlled method for fabricating stainless steel-based superhydrophobic surfaces. The method consists of microstructuring stainless steel surfaces by irradiating samples with femtosecond laser pulses and silanizing the surfaces. By low laser fluence, we fabricated typical laser-induced periodic surface structures (LIPSS) on the submicron level. The apparent contact angle (CA) on the surface is 150.3°. With laser fluence increasing, we fabricated periodic ripples and periodic cone-shaped spikes on the micron scale, both covered with LIPSS. The stainless steel-based surfaces with micro- and submicron double-scale structure have higher apparent CAs. On the surface of double-scale structure, the maximal apparent CA is 166.3° and at the same time, the sliding angle (SA) is 4.2°.