Robust superhydrophobic surface fabrication by fluorine-free method on filter paper for oil/water separation

Robust superhydrophobic surface exhibiting anti-fouling and self-cleaning ability were successfully fabricated by nano TiO2 modified by γ-aminopropyltriethoxysilane (KH550) and polydimethylsiloxane (PDMS) via wire rod coating. Due to the lower surface energy of PDMS and the hierarchical structure caused by the different aggregation sizes of TiO2 nanoparticles, the contact angle of the resulting superhydrophobic coating was 154.5° and the rolling angle was 3.5°. And the coated paper still had good non-wettability under water immersion. In addition, the coated paper was tolerant to mechanical damage and various temperature conditions. Even after 40 sandpaper wear cycles, the coating can still maintain good mechanical stability and superhydrophobicity. The superhydrophobic paper was used for oil-water separation, the separation efficiency was about 98% even after used 10 times. Furthermore, the prepared superhydrophobic paper exhibited excellent self-cleaning and anti-fouling properties, as well as demonstrated superb resistance to various water solutions owing to its high hydrophobicity. Moreover, the prepared superhydrophobic paper has application prospects in the industry of special wetting materials.     

Bi基化合物膜包覆ZnO的制备和电化学性能

为提高锌镍电池ZnO的循环充放电性能,采用Bi(NO3)3水解沉积法对ZnO包覆Bi基化合物膜,系统研究了包覆ZnO的微结构和电化学性能。TEM,XRD和EDS表明由Bi6(NO3)4(OH)2O6·2H2O,BiO和Bi2O3组成的Bi基化合物膜包覆在ZnO表面。表面包覆能提高ZnO的循环性能和放电容量,含5.1wt%Bi的包覆ZnO循环性能稳定,平均放电容量为509mAh·g-1,利用率为78%,性能有较大改善。充放电曲线和循环伏安结果均表明包覆Bi基化合物膜能降低锌镍电池的充电平台,加宽放电平台,提高ZnO的电化学活性。包覆Bi基化合物膜能有效减小活性材料与碱性电解液的接触,抑制ZnO的溶解,提高循环稳定性;而包覆膜的微孔结构又可使活性材料接触到电化学反应必须的H2O和OH-,保证了高的放电容量。     

Sol–gel derived durable antireflective coating for solar glass

In this paper, we present the design and preparation of a type of high-strength SiO₂/TiO₂ AR coatings used in solar glass by dip coating method. The average transmittance of glass coated in this way is increased by more than 6% in the wavelength from 400 to 800 nm, which fits well with the theoretical expectation. The mechanical performance and atmospheric exposure tests prove that the coatings have scratch resistance, erosion resistance and long-time stability. The AFM morphology shows that the surface of the coating is very smooth with the experimental result of RMS roughness 0.306 nm. These phenomena indicate that the SiO₂/TiO₂ AR coatings have high potential commercialization for low-cost solar glass.     

Hexamethyldisiloxane‐modified ZnO‐SiO2‐coated superhydrophobic textiles for antibacterial application

A superhydrophobic cotton textile with high antibacterial properties has been fabricated. The cotton textile was coated through the in situ growth of ZnO‐SiO₂ nanoparticles in presence of chitosan as the template agent via a hydrothermal process at 95 °C. This process was followed by the coating of additional layers of hexadecyltrimethoxysilane (HDTMS). The obtained cotton textile showed antibacterial property against Staphylococcus epidermis and Escherichia coli with inhibition zones up to 18.26 and 8.48 mm, respectively. Scanning electron microscopy (SEM) revealed that the coating had a rough surface, which was attributed to the distribution of ZnO‐SiO₂ nanorods of hexagonal shape. This rough surface creates a superhydrophobic layer that repels the bacteria, as proven by the large water contact angle of approximately 150°. Nevertheless, the HDTMS layers prolong the durability of hydrophobicity for up to 3 h.     

Characterization of anti-reflective and self-cleaning SiO2–TiO2 composite film

Sol–gel dip-coating technique can be used to fabricate SiO₂–TiO₂ composite film with self-cleaning and anti-reflectance properties from low-cost SiO₂ colloid solution and Ti(OC₄H₉)₄. The physical and structural properties have been investigated by UV–visible spectrophotometer, contact angle meter, XRD, FT-IR, FESEM. UV–vis spectra and methyl orange photodegradation experiments showed that the SiO₂–TiO₂ composite film had high light transmittance and photocatalytic activity.     

Tailoring of multifunctional cellulose fibres with “lotus effect” and flame retardant properties

This research aimed to create multifunctional cellulose fibres with water- and oil-repellent, self-cleaning, and flame retardant properties. A sol mixture of fluoroalkyl-functional siloxane, organophosphonate and methylol melamine resin was applied to cotton fabric by the pad-dry-cure method. Successful coating was verified by atomic force microscopy and Fourier transform infrared spectroscopy. The functional properties of the coated fibres were investigated using the static contact angles of water and n-hexadecane, the water sliding angles, the vertical test of flammability, the limiting oxygen index, and simultaneous thermal analysis. The results reveal that a homogeneous composite inorganic–organic polymer film formed on the cotton fabric surface exhibited the following properties: static contact angle of water of 150° and of n-hexadecane of 128°, water sliding angle of 10°, limiting oxygen index of 34 %, and high thermal stability. These results demonstrate the synergistic activity of the compounds in the coating, which resulted in the creation of a “lotus effect” on the fabric surface as well as excellent flame retardancy and thermal stability.     

Hydrophobic and Oleophobic Epoxy Surfaces Prepared by a Facile Process with Fluorosilicone Copolymer and SiO2 Nano-Particle

Hydrophobic and oleophobic surfaces with multi-scale structures were prepared on epoxy coating surfaces by using a facile process with fluorosilicone copolymer and SiO₂ nano-particles. The fluorosilicone copolymers were synthesized using perfluoroalkyl acrylate (FA), vinyltriethoxysilane (VTES) and styrene (St) as comonomers via radical emulsion polymerization. In this paper, the surface properties of epoxy coating modified by fluorosilicone copolymer and SiO₂ nano-particles were analyzed by using the contact angle measurement. The results showed that the modified epoxy coating surface exhibited not only excellent hydrophobicity but also oleophobicity, the water contact angle reached as high as 149° and the oil (atoleine) contact angle 101°, respectively.     

Preparation of superhydrophobic paper mulch and study on its anti-UV performance

In order to improve the shortcomings of paper mulch, such as the low water resistance and weather fastness in practical application, the paper mulch with a superhydrophobic structure was prepared by depositing zinc oxide layer and silicon dioxide layer on the surface of paper mulch by the solution impregnation method, the paper mulch surface treatment method is simple and environmentally friendly. The surface chemical composition and surface morphology of paper mulch before and after UV aging were characterized, respectively. The wetting property, bouncing property, and mechanical stability of paper-based film were studied. The results showed that the static contact angle of the superhydrophobic paper mulch was as high as 161.77°, and the average sliding angle was only 3.5°, which also showed excellent droplet bounce performance and mechanical stability. After UV aging experiment, the static contact angle of super-hydrophobic paper mulch was increased to 163.64°, and the sliding angle was reduced to 2.5°. Its excellent performance could still be maintained, showing excellent UV resistance, which improved the weather fastness and water resistance of paper mulch to a certain extent, and laid a foundation for the next large-scale field test.     

Development of multifunctional polydimethylsiloxane (PDMS)‐epoxy‐zinc oxide nanocomposite coatings for marine applications

Multifunctional epoxy‐polydimethylsiloxane nanocomposite coatings with antifouling and anticorrosion characteristics have been developed via in situ polymerization method at different loading (1, 3, and 6.5 wt.%) of ZnO nanoparticles to cater marine applications. A detailed comparative analysis has been carried out between epoxy‐polydimethylsiloxane control (EPC) and ZnO‐reinforced coatings to determine the influence of ZnO loading on various properties. The incorporation of ZnO in EPC led to increase in root mean square (RMS) roughness to 126.75 nm and improved hydrophobicity showing maximum contact angle of 123.5° with low surface energy of 19.75 mN/m of nanocomposite coating as compared with control coating. The differential scanning calorimetry (DSC) result indicated improved glass transition temperature of nanocomposite coatings with highest T_g obtained at 83.69°C in case of 1 wt.% loading of ZnO. The increase in hydrophobicity of the system was accompanied by upgraded anticorrosion performance exhibiting 98.8% corrosion inhibition efficiency (CIE) as compared with control coating and lower corrosion rate of 0.12 × 10^?3 mm/year. The Taber abrasion resistance and pull‐off adhesion strength results indicated an increment of 34.7% and 150.7%, respectively, in case of nanocomposite coating as compared with the control coating. The hardness of nanocomposite coatings was also improved, and maximum hardness was found to be 65.75 MPa for nanocomposite coating with 1 wt.% of ZnO. Our study showed that the nanocomposite coating was efficient in inhibiting accumulation of marine bacteria and preventing biofouling for more than 8 months. The developed environment‐friendly and efficient nanocomposite material has a promising future as a high‐performance anticorrosive and antifouling coating for marine applications.     

Facile Single-Step Synthesis of SiO<Subscript>2</Subscript>-Coated ZnO Nanorod as Hydrophobic Layer by Hydrothermal Method

In the present work, superhydrophobic SiO₂-coated ZnO nanorods have been successfully synthesized on glass surfaces via single-step hydrothermal route involving silicon hydroxide as silicon source, sodium dodecyl sulfate as surfactant and Zinc(II) acetate powder as Zinc source. The morphology and structure of obtained products were characterized by XRD, scanning electron microscopy, TEM, energy dispersive X-ray analysis, Pl and FTIR. The effect of calcination time on morphology and structure of as-synthesized products was evaluated. The obtained results exhibited that the synthesized nanorod-like product by calcining for 4 h showed excellent uniformity and quality. Furthermore, the water contact angel measurements were performed on as-synthesized products. The results showed due to introducing roughness by growth of SiO₂ on ZnO nanorod-like structure, all the samples show excellent degree of hydrophobicity and introducing these products on glass surfaces makes the glass superhydrophobic.     

Modification of nano-hybrid silicon acrylic resin with anticorrosion and hydrophobic properties

Silicone-acrylic resin (SAR) was prepared from acrylic monomers and silicone prepolymer by the free radical solution polymerization, and then mixed TiO₂ and SiO₂ nanoparticles modified by KH570 were added to prepare nanocomposite coating. Thermogravimetric analysis and contact angle measurements showed that the acrylic resin modified by silicone prepolymer exhibited an improved thermostability and a better hydrophobicity compared with the unmodified sample. The adding of nanoparticles further increased the hydrophobicity. The contact angle of modified silicone-acrylic resin with mixed TiO₂ and SiO₂ nanoparticles of 3 wt% is the highest, 108.4°. The UV resistance and weather resistance of the modified silicone-acrylic resin are significantly improved. It was also found through electrochemical impedance spectroscopy that the corrosion resistance was significantly improved by the addition of mixed TiO₂ and SiO₂ nanoparticles. Modified silicone-acrylic resin with mixed TiO₂ and SiO₂ nanoparticles of 3 wt% and 5 wt% coating system maintains an excellent anticorrosion performance (coating resistance R_c of more than 10⁹ Ω cm²) even at 3.5% NaCl electrolyte medium till to 1800 h.     

Structural and nanomechanical properties of sol–gel prepared (K,Na)NbO3 thin films

Perovskite (K, Na)NbO₃ (KNN) thin films (~100 nm) were prepared by sol–gel/spin coating process on Pt/SiO₂/Si substrates and annealed at 650 °C. The structural properties of KNN films were confirmed by X‐ray diffraction analysis (XRD), Raman spectroscopy and scanning electron, transmission electron and atomic force microscopy (SEM, TEM and AFM) analysis. Pure perovskite phase of K_0.65Na_0.35NbO₃ in nonstoichiometric composition with monoclinic symmetry in film was revealed. Uniform homogeneous microstructure of KNN film with the roughness (~6.9 nm) contained spherical particles (~50–90 nm). Nanoindentation technique was used to characterize the mechanical properties of KNN films. Elastic modulus and hardness of Pt, SiO₂ and KNN thin films were calculated from their composite values of KNN/Pt/SiO₂/Si film/substrate system. The modulus and hardness of KNN film (71 and 4.5 GPa) were lower in comparison with SiO₂ (100 and 7.5 GPa). Pt film (~30 nm) did not influence the composite modulus, but had effect on hardness of KNN film. Copyright © 2015 John Wiley & Sons, Ltd.     

Fabrication and characterization of SiO2/PVDF composite nanofiber‐coated PP nonwoven separators for lithium‐ion batteries

SiO₂/polyvinylidene fluoride (PVDF) composite nanofiber‐coated polypropylene (PP) nonwoven membranes were prepared by electrospinning of SiO₂/PVDF dispersions onto both sides of PP nonwovens. The goal of this study was to combine the good mechanical strength of PP nonwoven with the excellent electrochemical properties of SiO₂/PVDF composite nanofibers to obtain a new high‐performance separator. It was found that the addition of SiO₂ nanoparticles played an important role in improving the overall performance of these nanofiber‐coated nonwoven membranes. Among the membranes with various SiO₂ contents, 15% SiO₂/PVDF composite nanofiber‐coated PP nonwoven membranes provided the highest ionic conductivity of 2.6 × 10^?3 S cm^?1 after being immersed in a liquid electrolyte, 1 mol L^?1 lithium hexafluorophosphate in ethylene carbonate, dimethyl carbonate and diethyl carbonate. Compared with pure PVDF nanofiber‐coated PP nonwoven membranes, SiO₂/PVDF composite fiber‐coated PP nonwoven membranes had greater liquid electrolyte uptake, higher electrochemical oxidation limit, and lower interfacial resistance with lithium. SiO₂/PVDF composite fiber‐coated PP nonwoven membrane separators were assembled into lithium/lithium iron phosphate cells and demonstrated high cell capacities and good cycling performance at room temperature. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2013 , 51, 1719–1726     

Wettability characterization of transparent MgF<Subscript>2</Subscript> nanoparticle coatings with SiO<Subscript>2</Subscript> binder covered with fluoroalkylsilane self-assembled monolayers

SiO₂-added MgF₂ nanoparticle coatings with various surface roughness properties were formed on silica-glass substrates from autoclaved sols prepared at 100–180 °C. The samples were exposed to fluoro-alkyl silane (FAS) vapor to give hydrophobicity. All nanoparticle samples before FAS treatment had transmittances higher than 93% and such values were preserved even after FAS treatment. We examined root mean square roughnesses of the nanoparticle coatings with a Scanning Probe Microscope. We also examined their static and dynamic wettabilities with a contact angle meter and calculated their adhesive energies and surface free energies (SFEs). The surface roughness of the nanoparticle coating increased with the increase of the autoclave temperature. In addition, higher autoclave temperature caused increases in the sliding angle and decreases in the SFE. Interestingly, the higher the contact angle was, the larger the sliding angle was, although smaller sliding angle was expected with a larger contact angle.     

Functionalization of cotton fabrics with rutile TiO<Subscript>2</Subscript> nanoparticles: Applications for superhydrophobic,UV-shielding and self-cleaning properties

The superhydrophobic cotton fabrics were prepared by combining the coating of titanium dioxide (TiO₂) with the subsequent dodecafluoroheptyl-propyl-trimethoxysilane (DFTMS) modification. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) measurements revealed that the nanosized TiO₂ sphere consisted of granular rutile. The TiO₂ layer coated on the cotton altered both the surface roughness for enhancing the hydrophobicity and UV-shielding property. The cotton fabric samples showed excellent water repellency with a water contact angle as high as 162°. The UV-shielding was characterized by UV-vis spectrophotometry, and the results indicated that the fabrics could dramatically reduce the UV radiation. The photocatalytic progress showed that organic stains were successfully degraded by exposure of the stained fabric to UV radiation. Such multifunctional cotton fabrics may have potentials for commercial applications.     

PTFE/EP Reinforced MOF/SiO2 Composite as a Superior Mechanically Robust Superhydrophobic Agent towards Corrosion Protection,Self-Cleaning and Anti-Icing

Organic resin cross-linking ZIF-67/SiO₂ superhydrophobic (SHPB) multilayer coating was successfully fabricated on metal substrate. The perfluoro-octyl-triethoxy silane (POTS) modified ZIF-67 and SiO₂ coating was applied on primary coated polytetrafluoroethylene (PTFE) and epoxy resin (EP) via spray coating method. Here, we present that the robust superhydrophobicity can be realized by structuring surfaces at two different length scales, with a nanostructure design to provide water repellence and a microstructure design to provide durability. The as-fabricated multilayer coating displayed superior water-repellence (CA=167.4°), chemical robustness (pH=1–14) and mechanical durability undergoing 120th linear abrasion or 35th rotatory abrasion cycle. By applying different acidic and basic corrosive media and various weathering conditions, it can still maintain superior-hydrophobicity. To get a better insight of interaction between inhibitor molecules and metal surface, density functional theory (DFT) calculations were performed, showing lower energy gap and increased binding energy of ZPS/SiO₂/PTFE/EP (ZPS=ZIF-67+POTS) multilayer coating compared to the ZIF-67/SiO₂/PTFE/EP, thereby supporting the experimental findings. Additionally, such coatings may be useful for applications such as anti-corrosion, self-cleaning, and anti-icing multi-functionalities.     

Development and characterization of poly ethyl metha acrylate–iron oxide(III) based hydrophobic liquid nanocomposite films

Select applications of hydrophobic nanocomposites include preparation of robust self-cleaning surfaces, water-repellent glass surfaces, and waterproofing textiles. Various nanocomposites have been reported in the literature; however, the relationship between the nanocomposite surface morphology and its hydrophobicity needs to be understood better. In the present work Fe₂O₃ nanoparticles and poly ethyl metha acrylate (PEMA) were used in varying proportions to obtain a series of model hydrophobic surfaces (spin-coated on glass substrate). The hydrophobicity of these surfaces was measured by static contact angle; a maximum of 103° was obtained at highest loading of iron oxide nanoparticles. These surfaces were also characterized using AFM. The contact angle and characterization data were used to test some of the models which have been proposed in the recent literature on prediction of contact angle for composite surfaces. It is proposed that the hydrophobicity of the iron oxide–PEMA surface is due to the physical roughness causing air entrapment as well as the chemical heterogeneity. Based on the experimental studies and the simulations using the recent models on contact angle, some general features of relationship between a composite surface morphology and its hydrophobicity is proposed.     

SiO2/ZnO复合纳米粒子的制备及表征

采用双注控制沉积法(Controlled Double-Jet Precipitation,CDJP)将反应物添加到含有SiO₂的溶液中,通过直接的表面反应来制备单分散的SiO₂/ZnO复合纳米粒子,并对其进行了表征。透射电镜(TEM)观察表明,SiO₂表面有一层ZnO纳米颗粒或薄层。对复合纳米粒子SiO₂/ZnO进行X射线衍射(XRD)分析,复合颗粒的衍射峰与单独的氧化锌的衍射峰完全一致。能量弥散X射线法(EDX)分析表明,复合颗粒中含有Zn、Si、O元素。荧光光谱表明有ZnO的吸收峰。     

Sol–gel synthesis of ZnO–SiO2 thin films: impact of ZnO contents on its photonic efficiency

Highly crystalline ZnO–SiO₂ films obtained by a sol–gel method at different ZnO contents were deposited on silicon substrate (P(100)) using spin coating process. The XRD results revealed that the strong ZnO(100) peak is grown with highly c-axis oriented film and the crystallinity is progressively improved with increasing ZnO contents. SEM micrographs of the films deposited on silicon substrate show a homogeneous and uniformity structure at different ZnO content. The prepared ZnO–SiO₂ films are compared with either a film prepared from a commercial photocatalysts Hombikat UV-100 or Pilkington Glass Activ? by the determination of their photonic efficiencies for degradation of methylene blue. The photocatalytic efficiency of the 10 wt% ZnO–SiO₂ film was found to be about four times higher than film prepared from UV-100 or Pilkington Glass Activ?. The photocatalytic efficiencies of ZnO–SiO₂ films are increased with increasing ZnO content from 1 wt% to 10 wt% ZnO and then decreased at 15 wt% ZnO. The order of photocatalytic efficiencies of ZnO–SiO₂ films at different ZnO content and commercial photocatalysts after 6 h illumination were as following: 10 wt% ZnO > 15 wt% ZnO > 1 wt% ZnO > as-prepared 10 wt% ZnO–SiO₂ film > UV-100 > Pilkington Glass Activ?, which suggested that the ZnO–SiO₂ films are photoactive than commercial photocatalysts. The improved efficiency and potentially the low-cost synthesis suggest that this material might be practically useful as a photocatalyst film.     

Transparent hydrophobic and superhydrophobic coatings fabricated using polyamide 12–SiO2 nanocomposite

Optically transparent hydrophobic and superhydrophobic coatings have been prepared using polyamide 12–SiO₂ nanocomposite (NC) on glass substrates by the spin‐coating method. The coatings have been optimized for their hydrophobicity and transparency. The transformation from hydrophobic to superhydrophobic is achieved with increase in roughness (R_a) which increases with SiO₂ content. These coatings are highly transparent in the entire visible region (400–800 nm). The influence of layer thickness on water contact angle (WCA) and optical transmittance of the coatings has been studied. Field emission scanning electron micrograph (FESEM) shows the presence of SiO₂ nanoparticles covered with polyamide homogenously on the surface and the particles are aggregated to form a rough structure. X‐ray diffraction (XRD) patterns show that the polyamide losses its crystalline structure in the composite. The preparation procedure reported here is simple and eco‐friendly. The dual nature of the coatings, that is, high transparency and superhydrophobicity in the entire visible region suggests for its potential usage in self‐cleanings, wind screen and optoelectronic applications. Copyright © 2016 John Wiley & Sons, Ltd.