Maximum Contact Angle Research Articles

Superhydrophobic Fe-based amorphous alloy coatings with excellent anti-fouling and anti-corrosion properties by picosecond laser texturing

Producing superhydrophobic surfaces on the amorphous alloy coatings with excellent anti-corrosion and anti-fouling properties offers a promising strategy to broaden the applications of amorphous alloys in marine fields. In this work, the superhydrophobic surfaces on the Fe-based amorphous alloy coatings with micro-nano hierarchical structures were fabricated using picosecond pulsed laser texturing (LT) and surface chemical modification. The fabricated superhydrophobic coating surfaces have achieved a maximum contact angle of 166.5°and a minimum sliding angle of 3.6°. Additionally, these produced coatings also demonstrate outstanding self-cleaning and anti-fouling properties for preventing surface contamination. The superhydrophobicity originated from the formation of micro-nano hierarchical structures and the grafting of organic compounds with low surface free energy on the LT fabricated surfaces. The changes in wettability were attributed to the differences in the solid–liquid interfacial area fractions. The electrochemistry tests revealed that the corrosion resistance of the produced coatings with superhydrophobic surfaces had improved considerably compared with the as-sprayed amorphous alloy coatings, which could broaden the functional applications of the Fe-based amorphous alloy coatings.

Enhanced alumina substrate wear resistance via electroless NiP–TiC nanocomposite coating

In this research, several NiP–TiC nanocomposite coatings on alumina substrate were deposited via electroless nickel-phosphor plating methods under various deposition conditions. Field emission scanning electron microscope (FESEM) images show that different coating morphologies have been produced. The energy-dispersive x-ray spectroscopy (EDX) data demonstrate that the nanoparticles were successfully integrated and nickel and phosphorus are the principal components of the coating. The Nickel peaks have been noticed at an angle around 44⁰ which belongs to Ni (111) using an X-ray diffraction analysis (XRD) pattern for NiP–TiC nanocomposite coating at different immersion times and temperatures. According to the contact angle data, the nanocomposite coating created at (30 min at 95 °C) exhibited the best hydrophobic qualities and had a maximum contact angle value of 118.11°. The corrosion behavior was studied via the electrochemical method in 3.5 wt% NaCl at 25 °C, and the results showed that to get the best polarization resistance for the NiP–TiC coating, (60 min at 85 °C) deposition conditions are more suitable to get compact coating covering the full substrate and is 31 kΩ cm. For the best hardness value coating with multi-small nodules with high incorporation particle level can be obtained at (30 min and 95 °C) and is 7.98 GPa. Finally, the lower wear rate was collected for the coating plating at (90 min at 95 °C) deposition conditions because it has the least coefficient of friction.

Facile fabrication of organic superhydrophobic corn silk-derived cellulose acetate nanofiber for the effective sequestration of oil from oil-water mixture.

Oil spills and subsequent cleanup by oil-water separation remain a global concern. For the first time, corn silk-derived cellulose acetate (CSCA) and polyacrylonitrile (PAN) composite nanofiber are reported to create a superhydrophobic oil-water sequestration membrane. CA : PAN solutions with various PAN concentrations were evaluated for viscosity and conductivity. A CSCA nanofiber membrane was fabricated through electrospinning, which was superhydrophobic and oleophilic in water. Scanning electron microscope, energy-dispersive spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis/differential scanning calorimetry were used to analyze the membrane's morphological features. CSCA nanofibers formed a highly spherical bead with a maximum contact angle of 156° (>120°) in pure water solutions, demonstrating their superhydrophobicity. This study found that membranes can remove oil from oil-water mixtures and emulsions, as gravity is the only force required for propelling the system. Mineral oil had the highest oil sorption capability (908%), while toluene had the lowest (664%). For mineral oil-water mixtures, the CSCA membrane has the greatest separation flux at a maximum of 442 L/m2/h and the best separation efficiency at up to 99.67%. These findings provide strong support for using an as-prepared CSCA nanofiber membrane as a viable reusable oil sorbent in oil spill cleaning.

Optimization of process parameters for preparing the hydrophobic surface of aluminum alloy by laser-assisted electrochemical composite etching based on response surface method

To explore the influence of electrolyte concentration, single pulse energy, current density and scan times on the hydrophobic properties of laser-assisted electrochemical composite etching 2024 aluminum alloy surface, the experimental platform of laser-assisted electrochemical composite etching is built. Based on the results of the single-factor experiments, the response surface method (RSM) is chosen to optimize the process parameters. The optimum combination of process parameters is obtained, and the accuracy of the regression equation is verified by experiments. Through residual analysis, the established regression model fits well. By analysis of variance (ANOVA), the sequence of influence of the factors on apparent contact angle (from large to small) is single pulse energy, scan times, electrolyte concentration, and current density. With the maximum apparent contact angle as the goal, the combination of process parameters adjusted after optimization is: electrolyte concentration 2.0 mol/L, single pulse energy 20µJ, current density 18 mA, and scan times 15. Under these conditions, the experimental values of apparent contact angle is 157°, which is close to the predicted value (158°) by the models. The relative errors is 0.6%. It indicates that the regression model is accurate and reliable. This study shows that RSM is an effective method to optimize the process parameters and obtain the ideal experimental results.

Graphene composite self-healing antifog/frost-resist transparent coatings with zwitter-wettability

Self-healing materials achieve both durability and simplified maintenance by restoring their structure and function. However, self-healing materials utilizing surface hydrophilicity are considered incompatible with zwitter-wettability properties. Therefore, further investigation is needed to fabricate antifogging coatings that combine zwitter-wettability and self-healing properties. In this study, we demonstrated that polymer multilayer graphene composite coatings exhibit simultaneous antifogging and self-healing properties. We achieved a uniform dispersion of an aqueous solution of graphene by directly dispersing in a strong acid polymer and a uniform dispersion of graphene in the membrane via layer-by-layer self-assembly without any post-treatment, enabling precise control of hydrophobicity and water absorption of the membrane. The fabricated layer-by-layer coatings exhibited zwitter-wettability and self-healing performances comparable to those of previously reported systems. The maximum water droplet contact angle on the surface was 99° The 20-bilayer coating also exhibited excellent self-healing performance, closing 100 μm scratches within approximately 60 s and flattening the surface within approximately 300 s of exposure to water. In the antifogging tests, the coatings demonstrated high resistance to harsh cooling environments and exhibited excellent antifogging performance. This study provides a new zwitter-wetting strategy that combines self-healing and antifogging properties, providing an exceptional option for the development of next-generation surface coatings.

Splashing of Sn–Bi–Ag solder droplets

In this paper, we study the behavior and spreading dynamics of molten metallic alloy droplets. Five solders, including three rare earth elements and a commercial alloy, were used to assess their splashing behavior in terms of the material and impact conditions. The metallic solders were melted down in a heated chamber (oven) and then dripped onto a smooth copper flat substrate as spherical droplets. The impact of each alloy droplet was recorded and analyzed by high-speed imaging and image analysis to obtain the impact speed, the droplet size, and the dynamic contact angle. Our results show that the impact behavior is well parameterized by the splashing ratio, a dimensionless number encompassing the impact and liquid properties, and the maximum dynamic spreading contact angle. Our results are useful to the industry as they provide a criterion to select the maximum soldering injection speed or the droplet size to avoid splashing during soldering or the jetting of molten metals.

Long-time durability of superhydrophobic surface fabricated by laser texturing and carbon soot

In this work, a novel approach to fabricate highly durable superhydrophobic surfaces (SHSs) with exceptional long-term performance. The demand for real-world applications in various areas such as self-cleaning, anti-bacterial, anti-icing, and water droplet non-wetting behaviour has driven significant attention towards SHSs fabrication. As inspired by the lotus leaf's hierarchical structure, which combines low surface energy and a micro/nanopillar structure to achieve Superhydrophobicity. To achieve this, a fibre laser marking machine has been used to create circular-shaped microstructures on an AISI 420 steel substrate, with a pitch and diameter of 100 µm. To further enhance the surface's water-repellent properties, a unique technique that involves the deposition of carbon soot onto the textured geometry using a candle has been adopted. This resulted in a surface with impressively low surface energy. The most notable aspect of our research is the long-term durability of the fabricated SHSs. Even after two years of exposure to ambient conditions, the surface maintained a maximum contact angle of 158.6°, which is remarkably high, exceeding 150°. This research shows a robust and enduring superhydrophobic surface fabrication method, highlighting its potential for diverse real-world applications.

Anti-icing, wettability and structural characterization of Zirconia thin films

Radio frequency magnetron sputtering was used to produce the zirconium oxide thin films on corning glass substrates using oxygen as reactive gas andargon as inert gas, respectively. Working pressures were changedbetween 1 and 3.5 Pa, and their effects on the anti-icing, wettability, and structuralattributes of the deposited films were studied. The coating structure was determined with the help of X-ray diffraction, and it was found that the (111) peak becomes more prominent with decreasing working pressure. Results obtained with an atomic force microscope revealed that surface roughness values climbed in accordance with the working pressure. The films are hydrophobic, as determined by observations performed with a contact angle goniometer. It was found that the developedthin films had a maximum contact angle of 105.3°. Zirconium oxide thin film-coated samples were found to delay the ice formation when compared to the untreated samples in an anti-icing investigation.

Achieving superhydrophobicity of the FeCoCrMnNi surface via synergistic laser texturing and low temperature annealing

Superhydrophobic surfaces are highly desirable due to their remarkable water-repellent behavior. Laser texturing with subsequent low surface energy modification is a versatile strategy for creating such surfaces. In this study, via synergistic laser texturing and low temperature annealing, superhydrophobicity was first attempted to be achieved on the FeCoCrMnNi surface. By optimizing the laser parameters, the arrays with large depth-to-width ratios were constructed. Subsequently, by annealing at a low temperature, the transition process from superhydrophilicity to superhydrophobicity was successfully achieved on the FeCoCrMnNi surface. The effects of the hatching interval on the wettability were investigated, and the mechanism of wettability transition for FeCoCrMnNi was discussed. According to the experimental results and analysis, the textured surfaces exhibited excellent superhydrophobicity at different hatching intervals and a maximum contact angle of 165° was obtained. Furthermore, the created superhydrophobic surfaces possessed good liquid capture and self-cleaning capabilities and enabled magnification for optical imaging. The wettability transition after low temperature annealing was attributed to the absorption of airborne organic compounds. This study provides an efficient, clean, and versatile strategy to achieve superhydrophobicity of the FeCoCrMnNi surface by laser processing.

An Experimental Study on the Influence of the Fractal Characteristics of X80 Steel Surface Morphology on Water Ring Stability

The surface morphology of X80 steel with hydrophilic underwater oleophobic characteristic is described greater comprehensively and quantitatively in this work by combining fractal dimension and multifractal. X80 steel with hydrophilic underwater oleophobic surface characteristics was constructed using a chemical etching method. Then, with the aid of three wettability parameters—contact angle, rolling angle, and adhesion work—this study investigated the relationship between the surface fractal dimension of X80 and the stability of the water ring in the core annular flow. The results showed that: (1) the fractal dimension of X80 steel specimens increased first and then decreased with the increase of reaction time. Besides that, the value of it was greater than 2, indicating that the surface had obvious fractal characteristics. The spectral difference, Δf(α), and the spectral width, Δα, supplemented the description of the X80 steel surface morphology, which was consistent with the scanning electron microscope results. (2) When the maximum fractal dimension was 2.0808, the minimum contact angle of distilled water on its surface was 50.2°, and the maximum contact angle of underwater oil droplets was 166.4°. The larger the fractal dimension of X80 steel with hydrophilic underwater oleophobic properties, the more hydrophilic and underwater oleophobic it is. This illustrated that there was a strong binding force between the water and the X80 steel pipe wall, and hence the quality and efficiency of the core annular flow was improved, which was more conducive to the promotion of this technology in the field of heavy oil transportation.

Effect of Contact Angle on Friction Properties of Superhydrophobic Nickel Surface

Due to their excellent performance, superhydrophobic materials have received a lot of attention and research in friction reduction and wear resistance. However, the effect of different contact angles of superhydrophobicity on friction and wear properties has not been thoroughly studied. In this paper, a nanosecond pulsed laser was used to realize the preparation of a superhydrophobic nickel surface, which indeed reduced the coefficient of friction but also increased the wear volume when compared to the unprocessed surface. As the contact angle of the superhydrophobic nickel surface increased, the coefficient of friction gradually increased, and the wear volume decreased gradually in superhydrophobic nickel surfaces. When the laser energy density was 1 J/cm2, the contact angle was 150.3° and the minimum friction coefficient was 0.4. However, when the laser energy density was 50 J/cm2, the maximum contact angle was 156.4° and the minimum wear volume was 4.23 × 107 μm3. The friction direction also influenced the tribological properties of the superhydrophobic-textured surface. This method makes it possible to process superhydrophobic surfaces with more suitable friction and wear properties.

Hydrophobic modified PET ion track-etched membrane for oil/water separation

Due to the increase in oil spills and the high organic contamination of the marine environment, it is necessary to develop an oil/water separation technology with low cost and high efficiency. Membrane separation technology has been proven to be an important technology used in the oil/water separation area. Herein, PET ion track-etched membranes with channel sizes of 310 nm, 650 nm, 1050 nm, and 1950 nm were hydrophobically modified by chemical grafting using propyltrichlorosilane and o-xylene as modifier and solvent, respectively. The modified PET ion track-etched membranes were found to exhibit a maximum water contact angle of 140.81° and possessed excellent hydrophobic property with modifying conditions of 80 mM modifier and 24 h modification time. It demonstrated the grafted propyl groups on the PET ion track-etched membrane played a key role in the increase of hydrophobic property. After modification, the PET ion track etched membrane had a high oil/water separation ratio of 99.87% and a flux of 12,158.24 L/m2·h with good running stability. This work provided a cost-effective and facile approach to distinctly improve the ion track-etched membrane performance on durable oil/water separation.

The fluorinated SiO2 self‐assembly surface of epoxy resin with excellent insulating and superhydrophobic properties

AbstractThe flashover and dampness on the surface of epoxy resin (ER) composites are two critical factors leading to the failure of high voltage direct current (HVDC) insulating devices. Designing and constructing a surface structure with high insulating and hydrophobic performance is an effective way to solve these problems. In this paper, we prepared fluorinated silica nanoparticles (F‐SiO2) using a combination of dielectric barrier discharge (DBD) plasma and 1H,1H,2H,2H‐Perfluorodecyltrimethoxysilane (FAS‐17). The resulting low‐surface‐energy F‐SiO2 self‐assembled on the surface of ER to form a thin layer structure. Our results demonstrate a significant improvement in both the surface flashover voltage and hydrophobicity of ER composites with the self‐assembly structure. The maximum surface flashover voltage is increased by 35.73% to 12.08 kV, and the maximum water contact angle reaches superhydrophobicity at 155.5 ± 3°. The improvements in flashover voltage are attributed to changes in trap energy level and surface roughness. At the same time, the superhydrophobicity is due to the low‐surface‐energy characteristics and micro‐nano structure of the self‐assembly structure. This study provides a promising approach for synergistically improving flashover voltage and hydrophobicity of insulating materials.

Superhydrophobic Sponge for Highly Efficient Separation of Both Stratified and Emulsified Oil–Water Mixtures

Efficient separation of oil–water mixtures, particularly homogeneous and stable emulsions, has always been an industrial challenge. Herein, we report a facile, cost-effective procedure for fabricating superhydrophobic melamine sponges using a single solution–immersion process. The modified sponge has stable superhydrophobicity owing to the synergy of triple hydrophobic mechanisms with a maximum water contact angle of 158°. As an absorbent, the modified sponge block exhibits high porosity, outstanding absorption capacity, excellent mechanical properties, and superior physical and chemical stability, enabling its use for the separation of stratified oil–water mixtures via repeated absorption–extrusion processes with a separation efficiency of nearly 100%. Furthermore, as a filter, the crushed, modified sponge powders exhibit a demulsification efficiency ranging from 97.65 to 99.33% for the separation of ideal water-in-oil emulsions under gravity. Finally, the feasibility of these sponges for oilfield applications is established through the demonstration of the continuous separation of an emulsion of brine in crude oil using the modified sponge powders in conjunction with an in-house built apparatus. This work may open a viable pathway for the efficient separation of both stratified and emulsified oil–water mixtures via wettability, and provide a novel strategy for the reuse of waste sponges.

Facile fabrication of superhydrophobic steel surfaces with self-cleaning ability using nickel myristate/PDMS bilayer coating

Superhydrophobic (SHP) surface on 304 L SS was fabricated by a facile method using nickel myristate and polydimethylsiloxane (PDMS) bilayer coating. Surface preparation, electrodeposition and dip coating parameters were optimized to obtain uniform and adherent superhydrophobic coating with maximum water contact angle (WCA). Electrodeposited nickel myristate coating with siloxane overlayer on 304 L SS was characterized using field emission scanning electron microscopy (FESEM), atomic force microscopy (AFM), attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) and energy dispersive X-ray spectroscopy (EDS). FESEM images revealed hierarchical micro-nano structures of nickel myristate in the electrodeposited sample and a thin overlayer of PDMS. These samples showed a WCA of 170.7° ± 3.6° and a sliding angle (SA) of 4° ± 1°. The as-prepared sample retained its superhydophobic property in a wide pH range of 0 to 9, 1–5 M NaCl solution and 16 days immersion in mild alkali solution. Removal of contaminants on SHP surface with rolling water drops demonstrated its excellent self-cleaning ability. The chemical stability and self-cleaning ability of the electrodeposited sample coated with PDMS were found to be superior as compared to the only electrodeposited sample without PDMS coating. The chemical and mechanical durability of electrodeposited nickel myristate coating is improved by overlaying a PDMS layer, without compromising the hierarchical structures formed on the steel surface. This study provides an economical and straightforward method to fabricate chemically inert and self-cleaning superhydrophobic coating on 304 L SS substrate.

Preparation of multi band photothermal responsive bio-based superhydrophobic self-healing poly(siloxane-urethane) coating

In order to improve the poor hydrophobicity and single repair conditions of traditional self-healing polyurethane coatings, prepolymers were synthesized with bio-based polyol castor oil (CO), self-made alkyl aryl modified silicone polyols (Si-OH) and isophorone diisocyanate (IPDI), and 4,4'-dithiodianiline (ODD) was used as chain extender containing dynamic disulfide bond, 4-methylumbelliferone (4-MU), as a bio-based end capping agent with reversible ring structure, was polymerized step by step to prepare a photothermal responsive bio-based superhydrophobic self-healing poly(siloxane-urethane) coating (PUSi). In this paper, the effect of the amount of alkyl aryl modified silicone polyol (Si-OH) on the properties of PUSi was studied. The results showed that PUSi with different alkyl aryl modified silicone polyol additions could achieve self-healing under heating, UV irradiation and infrared light irradiation, and the maximum repair efficiency could reach 91% through optical microscope (OM), 3D profilometer and universal testing machine; The contact angle meter proved that the introduction of alkyl aryl modified silicone polyol greatly improved the hydrophobicity of PUSi, and the maximum water contact angle was 162°. The coating has broad application prospects in the fields of self-cleaning fabrics, super hydrophobic surfaces, special protective clothing and so on.

Synthesis of superhydrophobic FAS-EP/PTFE coating with excellent drag reduction performance and mechanical robustness

Superhydrophobic (SHP) materials have great potential for applications in self-cleaning, anti-fouling, anti-corrosion and drag reduction, but their poor mechanical robustness is a fundamental problem that hinders their practical application. In this work, we successfully and rapidly prepared SHP coating with good durability and drag reduction properties by a simple drop-coating technique after chemical modification and physical mixing. We investigated the effects of modification with 1H,1H,2H,2H-Perfluorodecyltriethoxysilane (FAS-17), a low surface free energy material, and the filling content of Poly tetra fluoroethylene (PTFE) on the hydrophobic property of the as-prepared coating. The maximum water contact angle (WCA) and the minimum sliding angle (SA) of the coating were 160.2 ± 0.4° and 5°, respectively. The coating maintained superhydrophobicity after 4.4 m of abrasion with 400 grit sandpaper and 3 h of water impact, indicating its excellent mechanical durability. In addition, it has outstanding self-cleaning and self-repairing properties. Moreover, the coating was innovatively applied to the surface of the chute, because it remarkably reduced the adhesion between the wet foam block and the chute. These findings here provide a novel insight into the design of a robust SHP coating and suggest a new potential application in express sorting industry for drag reduction.

Durable ultra-high hydrophobic oil absorbing materials based on biomass prepared via a simple low-cost strategy

Wood is renewable and biodegradable natural resource which has been widely used in construction industry and home furnishing; however, it absorbs moisture easily limiting its application. Herein, an ultra-hydrophobic wood was developed with acetylated β-cyclodextrin (Ac-β-CD). Due to the unique hydrophobic cavity structure of Ac-β-CD, a special micro/nanostructure was constructed on the wood cell wall achieving a maximum water contact angle of 150.5°. Also, it was stable at 137°, with a contact angle change rate of 1.16% during 10–100 s. The tensile strength of Ac-β-CD-wood increased by 58.76% due to the hydrogen bond network across the wood, and it also showed good performance in oil absorption capacity. Moreover, Ac-β-CD-wood can withstand more than 100 wipes while retaining its hydrophobic property. Therefore, this study provides a new eco-friendly strategy for producing biodegradable hydrophobic oil-absorbing wood with outstanding tensile strength and dimensional stability.

Cooperative synergistic effects of multiple functional groups in amide‐containing polyimides with pyridine ring and pendent tert‐butyl

AbstractIn this work, pyridine ring and pendent tert‐butyl were introduced into the diamine NTPA in view of improving the processability and transparency of the PIs via inhibiting charge‐transfer complexes (CTCs). Meanwhile, the amide linkage was simultaneously introduced in order to boost the thermal and mechanical properties of the PIs by reasonably increasing the polymer stiffness via noncovalent amide H‐bonding. The dianhydride BPADA was employed in the copolymerization with the diamine comonomers of NTPA with ODA in different ratios. Due to the presence of tert‐butyl and pyridine ring, the synthesized co‐PIs showed good optical properties with T500 higher than 75% for all co‐PIs, reaching 83% for homopolymer BPADA‐NTPA, higher solubility in organic solvents, and better hydrophobicity with maximum hydrostatic contact angle as high as 91.9°. Meanwhile, the amide H‐bonding increased the mechanical properties of co‐PIs with the maximum tensile strength reaching 127 MPa. Furthermore, amide H‐bonding exceedingly offset the reducing effects of pendent bulky butyl groups on the thermal properties of PIs, and the Tg of the co‐PIs containing NTPA moiety ranged in 244–298°C, remarkably higher than 218°C for homopolymer BPADA‐ODA. This work proved cooperative synergistic effects of multiple functional groups in balancing the general properties of co‐PIs.

Sol-Gel preparation and wetting behaviour analysis of hydrophobic Zirconium based nano-coating: Implications for solar panel coating

Hydrophobic coatings basically decrease the wettability of surface due to the presence of nanostructures on it. In this research work, nanozirconia sol was prepared by the sol-gel method and further hydrophobically modified using the hexamethyldisilazane (HMDS). Prepared sol was coated on the glass substrate and then analysed for its wetting behaviour. Three samples with different HMDS ratios mixed to Zirconia sol were coated, and analysed for surface morphological parameters through the atomic force microscopy and field emission scanning electron microscopy techniques. The wetting behaviour was analysed by studying the water contact angle and surface free energy of the samples. Here the transmittance was measured by transmittance metre at regular intervals for 30 days. Functional group determination was done by Fourier transform infrared spectrometer that confirmed the formation of Zirconium nanoparticles. Maximum contact angle of 101.2° was observed that showcased the hydrophobic properties. Hydrophobic coating was then successfully prepared, and sample with 2:1 ratio of Zirconium nanoparticles and HMDS showed the best hydrophobic nature amongst all the coatings prepared in this investigation.