Surface and mechanical properties of an organic-inorganic super- hydrophobic coating using modified nano-SiO2 and mixing polyurethane emulsion as raw materials

A series of organic-inorganic super-hydrophobic coatings were prepared using nano-SiO₂ particles modified by fluorine and silicone coupling agents, and a mixing polyurethane emulsion as main raw materials. The mixing polyurethane emulsion was consisted of the polyurethane emulsion end-terminated by double bond (WPUD) and polyurethane emulsion modified by silicone (WPUS). The influence of content of modified nano-SiO₂ particles and the weight ratio of WPUS to WPUD on microstructure and hydrophobicity of the coating surface were studied. The morphologies of coating surface were examined using SEM and AFM, hydrophobicity of the coating was researched by examining static water contact angle and so on. It was found that modified nano-SiO₂ particle was an indispensable factor during the preparation of super-hydrophobic coating. The roughness and hydrophobicity of the coating surface were enhanced obviously with an increase of the content of the modified nano-SiO₂ particles. When the content of the modified nano-SiO₂ particles increased up to 1.5%, the surface of coating possessed good super-hydrophobicity, and static water contact angle reached 169.1°. It was also noticed that the weight ratio of WPUS to WPUD in the base layer has also an important influence on the hydrophobicity and mechanical property of coating surface. With an increase of the ratio of WPUS to WPUD the hydrophobicity of the coating was enhanced, the tensile strength and peel strength reduced, but the elongation at break increased. When the weight ratio of WPUS to WPUD reaches up to 9/100, the static water contact angle reaches the maximum value of 169.1°.     

Fabrication of Polypropylene Super-Hydrophobic Surface Using PTFE-Coated-Sieves Template via Templating and Splitting Process

Super-hydrophobic Polypropylene surfaces were prepared employing combination method of replicating an artificial template and subsequent lifting off the master via a splitting way. The super-hydrophobic polypropylene surface, which was prepared using a 500-mesh PTFE-coated sieve, has gradient structures that microbumps with typical height and radius of approximately 20 µm and nano bundles on top of the bump surface. This surface exhibits the same self-cleaning property as the lotus leaf with water contact angle of 152.2 ± 2° and sliding angle less than 5°. The whole preparation process is simple, efficient, large-scale-prepare and environmentally friendly without organic solvents pollution.     

Robust super-hydrophobic inorganic nanoparticles modified layered structure Si2N2O membrane for membrane distillation

Robust super-hydrophobic ceramic membranes consisting of layered structure Si₂N₂O grains and organosilane-derived inorganic nanoparticles were successfully fabricated and employed for membrane distillation. First, phase inversion and sintering method were used to prepare porous Si₂N₂O membranes. The slurry composition and sintering temperature were optimized to obtain a pure phase Si₂N₂O membrane with high bending strength, tailored average pore size, and high permeability. Then, the Si₂N₂O membranes were modified with organosilane-derived inorganic nanoparticles through ammonolysis and pyrolysis reactions. Due to the micro and nano-hierarchical rough structures and the presence of -Si-CH₃ groups, the membranes showed super-hydrophobicity with a water contact angle of 152 ± 1°. Finally, the membranes were applied to desalinate seawater by sweeping gas membrane distillation. A stable water flux of 76 ± 0.9 L/(m² day) with a salt rejection of > 99% was recorded during 30 h distillation test at 75 °C, demonstrating the stability and durability of the membranes.     

A functional and robust super-hydrophobic PCC coating based on the induced assembly of modified zirconium phosphate

Improving the permeability of concrete is one of the important measures to extend the service life of concrete. In addition, for marine engineering, sewerage projects, and so on, mechanical stability and microbial induced corrosion of concrete structures cannot be ignored. We demonstrated a method to prepare high-performance super-hydrophobic (SHP) coating using functional zirconium phosphate (ZrP) and polydopamine (PDA) as the primary materials. The micro-nano rough structures were constructed on the concrete surface by alternating organic–inorganic assembly guided by each other. The coatings' apparent morphology, composition, and structure were analyzed using various surface analysis techniques. Based on the construction of micro-nano rough structures by the induced assembly of functional ZrP, the silane treatment significantly improved the water contact angle of the coating (WCA = 154° ± 3°), and the coating exhibited relatively high wear resistance, reaching 135° WCA even after 30 friction cycles. The water absorption of the specimens treated with the SHP composite coating was reduced by 79% to treated with silane. Meanwhile, the SHP composite coating showed excellent antimicrobial and anti-ice properties, due to the role of the functional ZrP and alternating organic–inorganic assembly. It was expected that the composite coating might potentially promote and accelerate applied superhydrophobic anticorrosive coating development for marine concrete durability.     

Properties of alumina coatings prepared on silica-based ceramic substrate by plasma spraying and sol-gel dipping methods

Silica-based ceramic cores are widely used in the manufacturing of hollow, nickel-based, superalloy turbine blades. However, elemental Hf, Ti, Al, and other active metals in the superalloy can react with silica-based ceramic cores during casting, resulting in a reduction in the quality of the turbine blades. In this study, both plasma spraying and sol-gel dipping methods were used to prepare alumina coatings on silica-based ceramic substrates to prevent the interfacial reaction. The performance of the alumina coatings prepared by both methods was evaluated by comparative analysis of the surface roughness, bonding interface morphologies, and the adhesive characteristics of the coating. The plasma-sprayed alumina coating has a roughness greater than 5 μm and peeled away from the substrate due to the difference in thermal expansion between SiO₂ and Al₂O₃ at temperatures above 1500 °C, rendering the silica-based substrate with the plasma-sprayed alumina coating unfit for the application requirements of the casting process. The alumina coating prepared by the sol-gel dipping method improved the roughness of the substrate from Ra 2.39 μm to Ra 1.83 μm, and no peeling was observed when heated to 1550 °C for 30 min due to the pinning characteristics of the coating on the substrate. Furthermore, the interfacial reaction between the DZ125 superalloy melt and the silica-based substrate coated with alumina by sol-gel dipping method were investigated. The alumina coating effectively inhibited the interfacial reaction and no reaction products were detected during the directional solidification with pouring temperature of 1550 °C and withdraw rate of 5 mm/min. While a uniform, 4–5 μm thick HfO₂ reaction layer formed between the uncoated substrate and the DZ125 alloy melt. Two dipping-drying cycles were required to ensure the alumina sol completely covered the surface of the substrate.     

Facile fabrication of water repellent coatings from vinyl functionalized SiO2 spheres

Water repellent SiO₂ particulate coatings were prepared by a one-step introduction of vinyl groups on the coating surface. Rough surface structure and low surface energy could be directly obtained. Vinyl functionalized SiO₂ (vinyl-SiO₂) spheres with average diameter of 500 nm were first synthesized by a sol–gel method in aqueous solution using vinyltriethoxysilane as the precursor. The multilayer SiO₂ coating fabricated by dip-coating method was highly hydrophobic with a water contact angle of 145.7° ± 2.3°. The superhydrophobic SiO₂ coating with a water contact angle up to 158° ± 1.7° was prepared by spraying an alcohol mixture suspension of the vinyl-SiO₂ spheres on the glass substrate. In addition, the superhydrophobic SiO₂ coating demonstrated good stability under the acidic condition. However, it lost its hydrophobicity above 200°C because of the oxidation and degradation of vinyl groups.     

Creation of superhydrophilic surfaces of paper and board

Corona, flame, atmospheric plasma, and liquid flame spray (LFS) techniques were used to create highly hydrophilic surfaces for pigment-coated paper and board and machine-glossed paper. All the surface modification techniques were performed continuously in ambient atmosphere. The physical changes on the surfaces were characterized by field emission gun-scanning electron microscopy (FEG-SEM), atomic force microscopy and Parker Print-Surf surface roughness. The chemical changes were analysed by X-ray photoelectron spectroscopy. The superhydrophilic surfaces, i.e. contact angle of water (CAW) <10°, were created mainly by modifying the surface chemistry of the paper and board by argon plasma or SiO₂ coating. The nano- and microscale roughness existing on paper and board surfaces enabled the creation of the superhydrophilic surfaces. Furthermore, the benefits and limitations of the surface modification techniques are discussed and compared. For example, the SiO₂ coating maintained its extreme hydrophilicity for at least six months, whereas the CAW of argon plasma-treated surface increased to about 20° already in one day.     

Preparation of PDMS/EEC/SiO2 composite super-hydrophobic coatings with excellent anti-guano adhesion performance

A low-cost and no-toxicity approach was presented to fabricate super-hydrophobic coatings via depositing hydroxy-terminated poly-dimethylsioxane and 3,4-epoxycyclohexylmethyl-3′, 4′-epoxycyclohexane carboxylate grafted nano-silica particles on substrates. The surface morphology, wettability, and anti-guano adhesion performance of as-prepared coatings were investigated. Results show the micro-nano hierarchical structures were formed on the surface of as-prepared coatings. The coatings exhibit super-hydrophobicity with a water static contact angle of 156° and sliding angle of 3°. Excellent anti-guano adhesion performances are also exhibited by the coatings, and the residue amount of guano captured by the coating only accounts for 0.3% of that captured by glass surface, making the as-prepared coating a promising candidate as an anti-guano strategy for both industry and everyday life (e.g. insulators for overhead power lines, buildings, statues and cars).     

Enhanced Anticorrosion and Antifouling Properties of Lubricant-Infused Pyramidal Polydimethylsiloxane Coating

Although slippery liquid-infused porous surfaces (SLIPSs) have been extensively studied for anticorrosion and antifouling applications, their durability and stability restrict their practicality. Herein, a technique is presented for fabricating SLIPS with dual-protection. First, a polydimethylsiloxane (PDMS) coating with a pyramidal morphology is fabricated through mold-based lithographic techniques. The mold is prepared by applying a texturing process to a monocrystalline silicon wafer of the type used to produce solar cells. Once infused with lubricant, the SLIPS is prepared and has a water-contact angle of 112°, on an inclined surface, water droplets slide easily off its surface. Due to the excellent chemical stability and low superficiality of the lubricant layer, the SLIPS offers excellent antifouling and anticorrosion properties. In a static marine environment, the SLIPS has an extremely low coverage fraction of algae. After being immersed in a 3.5% NaCl solution for 400 days, |Z|_0.01 Hz ≈ 10¹¹ Ω, and the phase angle at high frequency is approximately −90°. SLIPSs based on the PDMS coating provide dual protection (anticorrosion and antifouling), showing that this design approach produces SLIPSs with excellent potential for applications in marine environments.     

Facile preparation of bimodal polyethylene with tunable molecular weight distribution from ethylene polymerization catalyzed by binary catalytic system in the presence of diethyl zinc

A series of novel honeycomb films of tri- and octa-arm polystyrene-b-poly(tert-butyl acrylate) star polymers prepared by atom transfer radical polymerization and nitroxide mediated radical polymerization, respectively, have been fabricated. The type of solvents, specifically their miscibility in water is one of essential parameters to construct ordered pore structures. The tri- and octa-arm star polymers yield well-ordered microporous film specifically in 10 to 30 g/L CHCl₃ solution. The contact angle of glass slide substrate (54.57°) is adjusted to 41.06° by plasma treatment and to 12.21° by coating the glass slide with highly hydrophilic hyperbranched polyglycidol. The ordered honeycomb films are created on the hydrophobic substrates, but the ordered films are not formed on the hydrophilic substrates. Microspheres with the diameters ranging from hundreds of nanometers to several micrometers are also obtained by a slight modification of breath figure method.     

Surface modification of textured silicon and its wetting behaviour

Textured silicon (Si) substrate were prepared using various texturing methods both chemical and physical and their water contact angle, surface topography and Raman spectra were studied and investigated. The effect of plasma and chemical treatment on micro/nanostructure and roughness of the surface with and without deposition of Octadecyltrichlorosilane (ODTS, Cl₃Si (CH₃)₁₇), self-assembled monolayer (SAM) is investigated for achieving higher water contact angle (θ_c). The importance of synergism of texturing with deposition of ODTS SAM in preparing superhydrophobic silicon surfaces has been discussed. It is shown that superhydrophobic silicon surfaces can be achieved on silicon surfaces by coating with ODTS, irrespective of whether it is textured or not, polished or unpolished, provided a chemical treatment is given to the surface prior to the ODTS coating.     

表面沉积化镁合金基底上超疏水聚偏氟乙烯微孔膜的制备与性能

用一步浸泡法制得表面沉积化镁合金板，再以此镁合金板为制膜基底，以聚偏氟乙烯（PVDF）/N,N-二甲基乙酰胺（DMAc）/辛醇/水为制膜体系，采用干-湿相转化法制备了超疏水PVDF膜，该膜的水接触角可达160°。用粗糙度仪、扫描电镜、能谱仪、红外光谱仪等对镁合金表面和PVDF膜底面的微观结构、化学组成进行表征和分析。研究表明，一步浸泡处理过的镁合金表面生成了均匀的十四酸铁沉积物，该沉积物可在膜制备中部分嵌入膜底面，增加了膜底面的粗糙度，从而使PVDF膜的疏水性大幅提高。对PVDF膜的磨损试验表明，所制备的超疏水膜表面具备良好的机械稳定性。真空膜蒸馏实验表明，所制备的PVDF膜具有较高的通量和截留率，在运行中保持了更好的操作稳定性。     

Laser-Patterned Super-Hydrophobic Pure Metallic Substrates: Cassie to Wenzel Wetting Transitions

A femtosecond laser was used to create microstructures on very pure metal surfaces. The irradiated samples initially showed super-hydrophilic behavior. With time and exposure to ambient air the contact angle increased to about 160° with very low hysteresis. The surfaces supported the Cassie and Wenzel wetting states, depending on the technique used to deposit the water droplets. The created surface morphologies were idealized with a geometric model that is an assembly of densely packed cylindrical pillars with semispherical caps. Using this geometric model for calculation of the surface roughness, a theoretical Young contact angle of about 99° was calculated for all samples from the Wenzel and Cassie–Baxter equations. While the value of 99° significantly differs from the measured hydrophilic contact angles on the polished pure metallic samples, it indicates that a laser-induced surface reaction must be responsible for the evolution of contact angles to super-hydrophobic ones and that this phenomenon is independent of the type of metal.     

Preparation of superhydrophilic nanosilica/polyacrylate hard coatings on plastic substrate for antifogging and frost-resistant applications

A series of photosensitive hydrophilic agents (T20) comprising Tween-20, isophorone diisocyanate, and 2-hydroxyethyl methacrylate moieties were synthesized and used in the preparation of antifog/frost resistant (AFF) hard coatings on plastic substrates. By means of a hydrophilic/hydrophobic bilayer design, the prepared coatings demonstrated not only AFF property but also water resistibility. The bottom layer is an organic–inorganic composite consisting of SiO₂ nanoparticles embedded in a polymeric network of crosslinked dipentaethritol hexaacrylate. The AFF layer incorporates T20 in the formulations and links covalently with the bottom layer through a UV-curing polymerization process. Various methods, for example, FTIR, SEM, contact angle, and steam/defrosting tests, were employed to characterize the prepared coatings. Optimally, the coatings were found to be transparent, strong (4H, pencil hardness), adhering perfectly (level 5B) to the poly(methyl methacrylate) substrate, and could be soaked in water for 24 h at 25 °C without losing hydrophilicity (contact angle ~0°) or antifogging capability. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 48144.     

A novel composite coating mesh film for oil-water separation

Polytetrafluoroethylene-polyphenylene sulfide composite coating mesh film was successfully prepared by a simple layered transitional spray-plasticizing method on a stainless steel mesh. It shows super-hydrophobic and super-oleophilic properties. The contact angle of this mesh film is 156.3° for water, and close to 0° for diesel oil and kerosene. The contact angle hysteresis of water on the mesh film is 4.3°. The adhesive force between the film and substrate is grade 0, the flexibility is 1 mm and the pencil hardness is 4H. An oil-water separation test was carried out for oil-contaminated water in a six-stage superhydrophobic film separator. The oil removal rate can reach about 99%.     

Simple method for preparing ZnO superhydrophobic surfaces with micro/nano roughness

In this paper, a facile, inexpensive, and environment-friendly method is developed to construct a superhydrophobic surface with hierarchical micro/nanostructures on the steel substrates. The superhydrophobic surface was fabricated by magnetic agitation of a mixture of micro and nanosized Zinc oxide (ZnO) suspensions on a substrate, after being modified with a low-surface energy monolayer of stearic acid, the as-prepared coating exhibits self-cleaning properties with a water contact angle of 162° and a sliding angle of 6°, and shows the good corrosion resistance. It is believed that the rapid and cheap technique have a promising future application for fabricating superhydrophobic surfaces on steel materials.     

Magnetic polystyrene–palygorskite nanocomposite obtained by heterogeneous phase polymerization to apply in the treatment of oily waters

Water contaminated by oil poses challenges to the management of water resources. Magnetic nanoparticles has been issue of different potential applications including remotion oil from water. Magnetic polystyrene–palygorskite nanocomposites were prepared by a heterogeneous phase polymerization for the removal of organic contaminants from water. The organo‐Fe₃O₄‐palygorskite nanoparticles were coated with polystyrene, forming water repellent and oil absorbing surfaces to promote the removal of oil from the surfaces of nanocomposites by applying an external magnetic field. X‐ray fluorescence, X‐ray diffraction, scanning electron microscopy, zeta potential and size distribution measurement, surface area determination by BET, density measurement by He pycnometry, carbon grade determination, thermogravimetric analysis, Fourier‐transform infrared spectroscopy, Raman spectroscopy, and evaluation of hydrophobicity by contact angle were used to characterize the nanoparticles. The magnetic nanocomposite obtained showed excellent hydrophobicity, around 78° contact angle. In addition, oil removal capability tests were also performed, according to which the preliminary results indicated removal of approximately 98% of oil in synthetic oily water samples. The oil–water separation using this magnetic nanocomposite provides a promising alternative strategy for water treatment. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018 , 135, 46162.     

Structure characterisation and mechanical properties of crystalline alumina coatings on stainless steel fabricated via sol–gel technology and fibre laser processing

The surface modification of stainless steel by coating with alumina (Al₂O₃) was carried out using sol–gel coating technology in combination with laser processing. Alumina coatings have been synthesised via a sol–gel route and deposited on stainless steel substrates by dip coating. The coated substrates were then treated with pulsed ytterbium fibre laser radiation (λ = 1064 nm) in continuous wave mode with different specific energies. The composition and structure of the coated surfaces after laser processing were characterised by ATR-FTIR, XRD, SEM and contact angle measurements, whilst the mechanical properties of modified surfaces were determined using nano-indentation. The results showed that the alumina xerogel films coated on the substrates are successfully converted into crystalline alumina ceramic coatings by the laser irradiation, the structure of resulting coatings being dependent on the irradiation conditions, with increase of laser specific energy leading to the formation of initially γ-Al₂O₃ with increasing amounts of α-Al₂O₃ at higher energy. Nano-indentation results reveal that the laser processing results in significant improvement in hardness and Young's modulus of the alumina-coated surface and, at optimum, can achieve the mechanical properties at the same level as pure α-alumina ceramic, much higher than those of the as-dried xerogel coating.     

Influence of GaAs Substrate Orientation on InAs Quantum Dots: Surface Morphology, Critical Thickness, and Optical Properties

InAs/GaAs heterostructures have been simultaneously grown by molecular beam epitaxy on GaAs (100), GaAs (100) with a 2° misorientation angle towards [01−1], and GaAs (n11)B (n = 9, 7, 5) substrates. While the substrate misorientation angle increased from 0° to 15.8°, a clear evolution from quantum dots to quantum well was evident by the surface morphology, the photoluminescence, and the time-resolved photoluminescence, respectively. This evolution revealed an increased critical thickness and a delayed formation of InAs quantum dots as the surface orientation departed from GaAs (100), which was explained by the thermal-equilibrium model due to the less efficient of strain relaxation on misoriented substrate surfaces.     

Facile preparation of superhydrophobic polyester surfaces with fluoropolymer/SiO2 nanocomposites based on vinyl nanosilica hydrosols

A facile method to prepare superhydrophobic fluoropolymer/SiO₂ nanocomposites coating on polyester (PET) fabrics was presented. The vinyl nanosilica (V? SiO₂) hydrosols were prepared via one‐step water‐based sol‐gel reaction with vinyl trimethoxy silane as the precursors in the presence of the base catalyst and composite surfactant. Based on the V? SiO₂ hydrosol, a fluorinated acrylic polymer/silica (FAP/SiO₂) nanocomposite was prepared by emulsion polymerization. The FAP/SiO₂ nanocomposites were coated onto the polyester fabrics by one‐step process to achieve superhydrophobic surfaces. The results showed that silica nanoparticles were successfully incorporated into the FAP/SiO₂ nanocomposites, and a specific surface topography and a low surface free energy were simultaneously introduced onto PET fibers. The prepared PET fabric showed excellent superhydrophobicity with a water contact angle of 151.5° for a 5 μL water droplet and a water shedding angle of 12° for a 15 μL. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40340.