Fabrication and wear protection performance of superhydrophobic surface on zinc

A simple two-step process has been developed to render zinc surface superhydrophobic, resulting in low friction coefficient and long wear resistance performance. The ZnO film with uniform and packed nanorod structure was firstly created by immersing the zinc substrates into 4% N,N-dimethylformamide solution. The as-fabricated surface was then coated a layer of fluoroalkylsilane (FAS) by gas phase deposition. Scanning electron microscopy (SEM) and water contact angle (WCA) measurement have been performed to characterize the morphological feature, chemical composition and superhydrophobicity of the surface. The resulting surfaces have a WCA as high as 156° and provide effective friction-reducing and wear protection for zinc substrate.     

Fabrication of a superhydrophobic surface on a wood substrate

A layer of lamellar superhydrophobic coating was fabricated on a wood surface through a wet chemical process. The superhydrophobic property of the wood surface was measured by contact angle (CA) measurements. The microstructure and chemical composition of the superhydrophobic coating were analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR). An analytical characterization revealed that the microscale roughness of the lamellar particles was uniformly distributed on the wood surface and that a zinc stearate monolayer (with the hydrophobic groups oriented outward) formed on the ZnO surface as the result of the reaction between stearic acid and ZnO. This process transformed the wood surface from hydrophilic to superhydrophobic: the water contact angle of the surface was 151°, and the sliding angle was less than 5°.     

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.     

A novel fabrication of superhydrophobic surfaces for universal applicability

The present work reports a novel and facile approach to fabricate stable superhydrophobic surfaces for universal applicability in practice. Poly(furfuryl alcohol)/copper composite coatings were prepared on substrates via a brush-painting method; after being immersed in a stearic acid solution, the superhydrophobic surfaces were obtained due to the formation of copper stearate on the substrates. These products were characterized by field-emission scanning electron microscopy, Fourier transform infrared spectrometry, X-ray powder diffraction and the X-ray photoelectron spectrum. Results demonstrate that the superhydrophobic surfaces formed originally on copper substrates can also be generated on other substrates without the copper element. Furthermore, this work will provide a simple and universal method to create large-scale superhydrophobic surfaces on various substrates.     

Reversible switching of nanostructured cobalt hydroxide films from superhydrophobic to superhydrophilic state

Superhydrophobic cobalt hydroxide films with flower-like micro-nano structure prepared by chemical-bath deposition undergo a change in wettability from superhydrophobic to superhydrophilic state either by immersion in ethyl acetate or by heat treatment at 200°C and above. The superhydrophobicity of the film can be regained by immersion in an ethanolic solution of stearic acid. The superhydrophobicity is attributed to the combined effect of micro-nano binary surface morphology and the low surface energy of the self-assembled monolayer of stearic acid. It is proposed that switching from superhydrophobicity to superhydrophilicity is caused by removal of the adsorbed layer of stearic acid by solvent or heat treatment.     

Controllable fabrication of lotus-leaf-like superhydrophobic surface on copper foil by self-assembly

A novel approach was developed to fabricate a lotus-leaf-like superhydrophobic surface on a copper foil by simple self-assembly method with the assistance of the porous PDMS template which was used to adjust the oxidized parts of the copper foil surface before self-assembly. The results showed a series of beautiful flower-like microstructures resulting from the self-assembly of cupric stearate that were distributed at regular intervals on the as-prepared copper foil surface similar to the papillae of lotus leaf surface. The water contact angle of the as-prepared copper surface was up to 161° and its sliding angle was only 3°. Its great superhydrophobicity could be kept unchanged after 6 months in air. The formation mechanism of the lotus-leaf-like structure was discussed. This simple and low-cost method is expected to be applied to design and prepare complicated superhydrophobic surfaces with beautiful regular microstructures on different substrates such as stainless steel, zinc, and so on.     

Thermal stability of the structural features in the superhydrophobic boehmite films on austenitic stainless steels

Boehmite thin film with 50–100 nm surface flake structure has been synthesized on AISI 316 type austenitic stainless steel by immersing boehmite gel film into boiling water. When further coated with hydrolyzed (heptadecafluoro-1,1,2,2-tetrahydrodecyl) trimethoxysilane (FAS), the boehmite film becomes superhydrophobic with a contact angle for water of 152°. The superhydrophobic property results from both the nanoscale surface flake structure and the low surface energy of the FAS top layer. The topography of such film was revealed by atomic force microscope (AFM) and a set of roughness parameters of such film was discussed. The degradation of superhydrophobicity of the surface was studied as a function of the heat-treatment temperatures. Below 600 °C, the surface remained to be superhydrophobic with the FAS top layer. Above 700 °C, the surface was not superhydrophobic anymore due to a gradual loss in surface roughness which was revealed by field emission scanning electron microscope (FESEM). A phase change from boehmite to γ-Al₂O₃ occurred during the heat-treatments from 700 to 900 °C which was studied by the selected area electron diffraction (SAED) patterns from the transmission electron microscope (TEM) measurement.     

Facile fabrication of superhydrophobic surface with micro/nanoscale binary structures on aluminum substrate

The present work reports a simple method to produce the aluminum superhydrophobic surface based on an interface reaction between an aluminum foil and zinc aqueous solution. The products were characterized by field-emission scanning electron microscopy, X-ray powder diffraction and X-ray photoelectron spectrum. The field-emission scanning electron microscopy images show that the coating surface is composed of micro/nanoscale binary structure, which is similar to the structure of lotus leaf. The wettability of the coating surface was also investigated. It was found that after treatment with stearic acid, the wettability of the aluminum foil changed from superhydrophilic to water-repellent superhydrophobic. The complex micro/nanoscale binary structures along with the low surface energy lead to the high surface superhydrophobicity.     

Thermal effect on superhydrophobic performance of stearic acid modified ZnO nanotowers

The thermal desorption of stearic acid on superhydrophobic zinc oxide nanotowers has been investigated. The stearic acid passivated zinc oxide nanotowers provide a very high contact angle of ∼173 ± 1.1° with a very low hysteresis of ∼1.4 ± 0.5° due to the presence of a binary structure composed of several nanosteps on each nanotower of height ∼700 nm that eventually reduces the area of contact between the drop and the nanotowers and trapping more air as revealed by the field emission scanning electron microscopy images. The superhydrophobic performance of these nanotowers, however, declines following annealing at elevated temperatures. Fourier transform infrared spectra show a reduction in the intensity of stearic acid -CH_n peaks at elevated temperatures revealing the cause of the decrease in contact angle and confirming the occurrence of thermal desorption at 184 °C. The corresponding activation energy for desorption determined from our data is 0.34 ± 0.05 eV. It is found that the stearic acid has completely disappeared at 350 °C, making the sample hydrophilic.     

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.     

One-step electrodeposition process to fabricate cathodic superhydrophobic surface

In this work, a rapid one-step process is developed to fabricate superhydrophobic cathodic surface by electrodepositing copper plate in an electrolyte solution containing manganese chloride (MnCl₂·4H₂O), myristic acid (CH₃(CH₂)₁₂COOH) and ethanol. The superhydrophobic surfaces were characterized by means of scanning electron microscopy (SEM), and Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The shortest electrolysis time for fabricating a superhydrophobic surface is about 1 min, the measured maximum contact angle is 163° and rolling angle is less than 3°. Furthermore, this method can be easily extended to other conductive materials. The approach is time-saving and cheap, and it is supposed to have a promising future in industrial fields.     

Superhydrophobic surfaces based on dandelion-like ZnO microspheres

This study presents a simple method to fabricate superhydrophobic surface based on ZnO nanoneedles. ZnO nanoneedles had been constructed on zinc layers by immersing in an aqueous NH₄OH solution at 80 °C. The ZnO films were characterized by X-ray diffraction, scanning electron microscopy and X-ray photoelectron spectroscopy. The ZnO films exhibited excellent superhydrophilicity (contact angle for water was 0°), while they changed wettability to superhydrophobicity with a water contact angle greater than 150° after further chemical modification with n-dodecanoic acid. The procedure reported here only needs readily available reagents and laboratory equipments, which can be applied to various substrates of any size and shape.     

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.     

Low-cost one-step fabrication of superhydrophobic surface on Al alloy

A stable superhydrophobicity on aluminum alloy has been rendered by a low-cost one-step method, simply immersing the substrates in a solution containing hydrochloric acid and fatty acid molecules. The formation mechanism of such a surface was proposed by SEM morphology and EDS results. The resulting surface shows superhydrophobicity and low adhesion. This low cost and facile process provides a real feasible avenue for large-scale production of superhydrophobic surfaces.     

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°.     

Controlled growth of superhydrophobic films by sol-gel method on aluminum substrate

Superhydrophobic surface was prepared by sol-gel method on aluminum substrate via immersing the clean pure aluminum substrate into the solution of zinc nitrate hexahydrate (Zn(NO₃)₂·6H₂O) and hexamethylenetetraamine (C₆H₁₂N₄) at different molar ratios and unchanged 0.04 mol/L total concentration, then heated at 95 °C in water bath for 1.5 h, subsequently modified with 18 alkanethiols or stearic acid. When the molar ratios of Zn(NO₃)₂·6H₂O and C₆H₁₂N₄ were changed from 10:1 to 1:1 the contact angle was higher than 150°. The best prepared surface had a high water contact angle of about 154.8°, as well as low angle hysteresis of about 3°. The surface of prepared films using Zn(NO₃)₂·6H₂O and C₆H₁₂N₄ composed of ZnO and Zn-Al LDH, and Al. SEM images of the film showed that the resulting surface exhibits different flower-shaped wurtzite zinc oxide microstructure and porous Zn-Al LDH. The special flowerlike and porous architecture, along with the low surface energy leads to the surface superhydrophobicity.     

SiO2薄膜的液相沉积及特性

将基片浸入到低温SiO₂过饱和的六氟硅酸(H₂SiF₆)溶液中,在其表面上沉积SiO₂薄膜。这种新的生长工艺称之为液相沉积(LPD)。本文着重介绍LPD工艺及LPD SiO₂薄膜的特性。     

Preparation of superhydrophobic films on titanium as effective corrosion barriers

Stable superhydrophobic films were prepared on the electrochemical oxidized titania/titanium substrate by a simple immersion technique into a methanol solution of hydrolyzed 1H,1H,2H,2H-perfluorooctyltriethoxysilane [CF₃(CF₂)₅(CH₂)₂Si(OCH₂CH₃)₃, PTES] for 1 h at room temperature followed by a short annealing at 140 °C in air for 1 h. The surface morphologies and chemical composition of the film were characterized by means of water contact angle (CA), field emission scanning electron microscopy (FESEM), atomic force microscope (AFM) and X-ray photoelectron spectroscopy (XPS). The water contact angle on the surface of this film was measured to be as high as 160°. SEM images showed that the resulting surfaces exhibited special hierarchical structure. The special hierarchical structure along with the low surface energy leads to the high surface superhydrophobicity. The corrosion resistance ability and durance property of the superhydrophobic film in 3.5 wt.% NaCl solution was evaluated by the electrochemical impedance spectroscopy (EIS). The anticorrosion properties of the superhydrophobic film are compared to those of unmodified pure titanium and titania/titanium substrates. The results showed that the superhydrophobic film provides an effective corrosion resistant coating for the titanium metal even with immersion periods up to 90 d in the 3.5 wt.% NaCl solution, pointing to promising future applications.     

A simple way to fabricate an aluminum sheet with superhydrophobic and self-cleaning properties

<正>A superhydrophobic aluminum sheet is fabricated via a hot water immersing process and subsequently surface modification with heptadecafluorodecyltrimethoxy-silane(HTMS).As revealed by the scan electron microscopy(SEM), X-ray diffraction(XRD),and Fourier-transform infrared spectrophotometer(FTIR) results,a rough pseudoboehmite film is formed on the aluminum sheet,and HTMS molecules are grafted on the film surface successfully.These two factors make the treated aluminum sheet present superhydrophobicity with a water contact angle larger than 160°and sliding angle less than 5°,and possess a self-cleaning property.Furthermore,the flexible superhydrophobic aluminum sheet could be pasted to a cylinder surface without destroying its superhydrophobicity.At the end,the effect of hot water treatment time on superhydrophobicity is investigated.     

SiO2薄膜的液相沉积及特性

将基片浸入到低温SiO2过饱和的六氟硅酸（H2SiF6)溶液中,在其表面上沉积SiO2薄膜,这种新的生长工艺称之为液相沉积（LPD）。本文着重介绍LPD工艺及LPDSiO2薄膜的特性。