Cu-coated stainless steel surfaces containing micro- and nanoscale binary structures having different surface roughness were successfully fabricated by means of a facile one-step electroless plating technology, and the resulting surfaces were modified by the low free energy material HFTHTMS (HFTHTMS = (heptadecafluoro-1,1,2,2-tetrahydrodecyl) trimethoxysilane). The experimental results of wettability exhibit that such unmodified surfaces have a strong adhesive force to water droplets, and their contact angles increase with increasing surface roughness, whereas the modified surfaces by HFTHTMS show the superhydrophobic characteristic with contact angles higher than 150° and sliding angles lower than 5°. 相似文献
A super-hydrophobic 2024Al surface with micro- and nano-scale hierarchical crater-like structure has been prepared by constructing the surface and modifying the textured surface with low energy material of HFTHTMS (HFTHTMS = (heptadecafluoro-1,1,2,2-tetrahydrodecyl)trime thoxysilane). The textured surface was characterized by scan electron microscope (SEM) and x-ray photoelectron spectrum (XPS). The SEM image shows the crater-like surface with micro- and nano-scale hierarchical microstructures. The textured surface modified with HFTHTMS has super-hydrophobicity with a contact angle of 162° and the sliding angle of 3°. 相似文献
Hydrophilic laser-textured silicon wafers with natural oxide surfaces were rendered hydrophobic by depositing electrostatically charged submicrometer Teflon particles, a process termed as triboelectric Teflon adhesion. Silicon surfaces were micro-textured (~5 μm) by laser ablation using a nanosecond pulsed UV laser. By varying laser fluence, micro-texture morphology of the wafers could be reproduced and well controlled. Wetting properties of the triboelectrically charged Teflon-deposited surfaces were studied by measuring apparent static water contact angles and water contact angle hysteresis as a function of substrate roughness and the amount of Teflon deposited. A similar study was also performed on various micro-textured silicon carbide surfaces (sandpapers). If the average substrate roughness is between 15 and 60 μm, superhydrophobic surfaces can be easily formed by Teflon deposition with water contact angle hysteresis less than 8°. This environmentally benign solvent-free process is a highly efficient, rapid, and inexpensive way to render contact-charged rough surfaces hydrophobic or superhydrophobic. 相似文献
Equilibrium contact angles of melted geranium have been measured at fused quartz surfaces. The surfaces were preliminarily grinded, polished, and, in some cases, etched. Then, the roughness coefficients are determined for the relief profile and the surface itself by optical interferometry using a NanoMap 1000 WLI profilometer. The contact angle has been found to vary in a range of 147°–164° depending on the method of surface pretreatment. The measured values of the contact angles agree with the data of other researchers. At the same time, the analysis of the obtained data has led to the conclusion that Wenzel’s equation, which relates the contact angles at smooth and rough surfaces, is not valid for germanium droplets on quartz surface. 相似文献
In this paper, the icephobic properties of superhydrophobic surfaces are investigated under dynamic flow conditions using a closed-loop low-temperature wind tunnel. Superhydrophobic surfaces were prepared by coating aluminum and steel substrate plates with nano-structured hydrophobic particles. The superhydrophobic plates, along with uncoated controls, were exposed to a wind tunnel air flow of 12 m/s and ?7 °C with deviations of ±1 m/s and ±2.5 °C, respectively, containing micrometer-sized (~50 μm in diameter) water droplets. The ice formation and accretion were observed by CCD cameras. Results show that the superhydrophobic coatings significantly delay ice formation and accretion even under the dynamic flow condition of highly energetic impingement of accelerated supercooled water droplets. It is found that there is a time scale for this phenomenon (delay in ice formation) which has a clear correlation with contact angle hysteresis and the length scale of the surface roughness of the superhydrophobic surface samples, being the highest for the plate with the lowest contact angle hysteresis and finest surface roughness. The results suggest that the key for designing icephobic surfaces under the hydrodynamic pressure of impinging droplets is to retain a non-wetting superhydrophobic state with low contact angle hysteresis, rather than to only have a high apparent contact angle (conventionally referred to as a “static” contact angle). 相似文献
Hydrophilic paper was rendered with hydrophobic and superhydrophobic property after the treatment with solutions and nanoparticles of cellulose stearoyl ester (CSE), respectively. Cellulose stearoyl ester with a degree of substitution of 2.99 was synthesized from cellulose using stearoyl chloride. By dip-coating paper in CSE solution of at least 3 mg/ml in toluene, paper became hydrophobic with stable water contact angles of more than 120°. After further spray-coating using CSE nanoparticles that were prepared from CSE solution via nanoprecipitation, paper surface became superhydrophobic with water contact angles of larger than 150°. These superhydrophobic surfaces also exhibited self-cleaning character. Furthermore, the superhydrophobic paper surfaces showed a temperature-responsive character and could be turned hydrophobic after a heat-treatment at 70 °C for 5 min. 相似文献
The organic–inorganic nanocomposite films were fabricated by grafting polystyrene (PS) onto the vinyltriethoxysilane (VTEOS)
modified titanium dioxide nanopowders using free radical polymerization. The composition of the surfaces and the structure
for the PS grafted titania (PS-g-TiO2) were examined by infrared spectroscopy, X-ray photoelectron spectroscopy and thermogravimetric analysis, and the rough surface
was confirmed by the evaluation of the morphological characteristics of the coating using hybrid particles. The wetting properties
of the VTEOS modified titania and PS-g-TiO2 films were investigated, which show the maximum static water contact angles of 160° and 154°, and minimum sliding angles
of 3° and 4°, respectively. 相似文献
The article reports on the wetting properties of silicon-based materials as a function of their roughness and chemical composition. The investigated surfaces consist of hydrogen-terminated and chemically modified atomically flat crystalline silicon, porous silicon and silicon nanowires. The hydrogenated surfaces are functionalized with 1-octadecene or undecylenic acid under thermal conditions. The changes occurring upon surface functionalization are characterized using Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS) spectroscopy and water contact angle measurements. By increasing the surface roughness, the static water contact angle increases. The combination of high surface roughness with chemical functionalization with water repellent coating (1-octadecene) enables reaching superhydrophobicity (water contact angle greater than 150°) for silicon nanowires. 相似文献
Micro- and nanospheres with superamphiphobic surfaces were prepared by a simple method that employed the conventional dispersion
polymerization of perfluoroalkyl methacrylates in methanol. The polymerizations of 2,2,2-trifluoroethyl methacrylate (TFMA)
produced microspheres with an average 4.12-μm diameter, while that of 2-(perfluorooctyl)ethyl methacrylate (POMA) provided
nanospheres with a 679-nm diameter. An X-ray photoelectron spectroscopy analysis revealed that the fluorine atoms were highly
concentrated on the top of the sphere surfaces. It was found that the surface coated with the spheres had a superamphiphobicity.
The water contact angles were 150° for the PTFMA microspheres and 173° for the PPOMA nanospheres, while the diiodomethane
contact angles were 159° for the microspheres and 160° for the nanospheres. The synergistic effect of the spherical structure
and the high concentration of fluorine on the top of the surface produced the superamphiphobicity. 相似文献
The present work investigates the enhancement of water repellency on engineering materials surfaces using nanoscale roughness inherent in multi-walled carbon nanotubes (MWCNTs) together with a hydrophobic polystyrene coating via a simple spraying-based technique. The coatings show both a high contact angle and a small sliding angle for water droplets. The different surfaces obtained exhibit contact angles from 125° up to 153° depending on the preparation conditions. The observations of the topology by scanning electron microscopy reveal that the nanostructure created by the MWCNTs and the microstructure induced by the deposition of polystyrene particles forming a two-level structure that conceptually mimics the lotus leaf surface are necessary to create stable superhydrophobic surfaces. 相似文献
Superhydrophobic silica nanotrees were obtained by sol–gel method with hybrid silica sol and jelly-like resorcinol formaldehyde
resin. Rough surfaces were obtained by removing the organic polymer at high temperature. After the films with rough surface
were modified by trimethylchlorosilane (TMCS), the wettability of the film changed from superhydrophilic to superhydrophobic.
The surface roughness of the silica nanotrees film is about 20 nm, and it is transparent and superhydrophobic with a water
contact angle higher than 150°. 相似文献
The creation of low hysteresis superhydrophobic paper is reported using a combination of oxygen plasma etching and plasma deposition of an 80 nm non-fluorinated, hydrophilic diamond-like carbon (DLC) coating. The DLC has an equilibrium (flat surface) contact angle (θe) of 68.2° ± 1.5°, which is well below the 90° contact angle that is typically believed to be a prerequisite for superhydrophobicity. Coating of paper substrates with the DLC film yields an advancing contact angle of 124.3° ± 4.1°, but the surface remains highly adhesive, with a receding contact angle <10°. After 60 min of plasma etching and DLC coating, a low hysteresis, superhydrophobic surface is formed with an advancing contact angle of 162.0° ± 6.3° and hysteresis of 8.7° ± 1.9°. To understand the increase in contact angle and decrease in hysteresis, atomic force microscopy and optical profilometry studies were performed. The data demonstrates that while little additional nanoscale roughness is imparted beyond the first 5 min of etching, the roughness at the microscale continually increases. The hierarchical structure provides the appropriate roughness to create low hysteresis superhydrophobic paper from a hydrophilic coating. 相似文献
The paper reports on the wetting characterization of two surfaces presenting reentrant shapes at micro- and nanoscale using low surface tension liquids (down to 28 mN/m). On the one hand, mushroom-like microstructures are fabricated by molding poly(dimethylsiloxane) (PDMS) onto a patterned sacrificial photoresist bilayer. On the other hand, zinc oxide nanostructures (ZnO NS) are synthesized by easy and fast chemical bath deposition technique. The PDMS and ZnO NS surfaces are then chemically modified with 1H,1H,2H,2H-perfluorodecyltrichlorosilane in vapor phase. Both PDMS and ZnO NS surfaces exhibit a large apparent contact angle (>150°) and contact angle hysteresis varying from 50° to a quasi-null value. This large discrepancy can be ascribed to the length scale and topography of the structures, promoting either a vertical imbibition or a lateral spreading within the roughness. 相似文献
Summary: With the proper selection of shear and thermal conditions, super‐hydrophobic polymeric surfaces (contact angle > 150°) with tunable sliding angles (from less than 1° to higher than 90°) can be prepared from pure isotactic poly(propylene) (iPP) without any further modification with low‐surface‐energy components under ambient atmosphere. The formed surfaces have naturally good thermal properties, chemical and moisture resistance, low density, and potentially low manufacturing cost.
SEM images of formed super‐hydrophobic surfaces and related two extreme sliding angles (contact angles of these surfaces are higher than 150°). 相似文献
Rough and patterned copper surfaces were produced using etching and, separately, using electrodeposition. In both of these approaches the roughness can be varied in a controlled manner and, when hydrophobized, these surfaces show contact angles that increase with increasing roughness to above 160 degrees . We show transitions from a Wenzel mode, whereby the liquid follows the contours of the copper surface, to a Cassie-Baxter mode, whereby the liquid bridges between features on the surface. Measured contact angles on etched samples could be modeled quantitatively to within a few degrees by the Wenzel and Cassie-Baxter equations. The contact angle hysteresis on these surfaces initially increased and then decreased as the contact angle increased. The maximum occurred at a surface area where the equilibrium contact angle would suggest that a substantial proportion of the surface area was bridged. 相似文献
Highly hydrophobic epoxy coatings with the surface energy as low as 14.5 mJ m–2 and contact angles with water of 120°–150° were prepared from powdered compounds modified with less than 2 wt % finely dispersed polytetrafluoroethylene particles by dry mixing. As shown by scanning electron microscopy, EDX microanalysis, and atomic-force microscopy, the film formation at 180°С and formation of a polymer network matrix are accompanied by predominant migration of polytetrafluoroethylene particles to the air/coating interface, leading to gradient distribution of fluorine across the film and significant enrichment of the coating surface with fluorine. By varying the polytetrafluoroethylene content, it is possible to obtain hydrophobic coatings with satisfactory physicomechanical properties, smooth or rough surface, including micrometric and nanometric roughness, and different surface energy. 相似文献