Superhydrophobic coatings show wide applications. Here, a low adhesive superhydrophobic surface was prepared by an in-situ growth of layered double hydroxide (LDH) combined with a surface ...modification process by stearic acid (STA). The LDH sheets provide a rough structure and the STA molecule provides the low surface energy. As results, the STA-LDH coating shows a water contact angle of 151°. The siliding angle of the STA-LDH coating is less than 5°. Besides, the coating shows a low-adhesive surface with good self-cleaning property. Electrochemical tests confirms that the STA-LDH coating shows elevated coating resistance from 5.105 × 104 Ω·cm2 for bare sample to 8.46 × 106 Ω·cm2. Furthermore, the corrosion current density of the STA-LDH coating decreases by ~2 orders of magnitude compared to the bare Al alloy. This work provide a novel strategy for constructing low-adhesive, self-cleaning and anticorrosive coating.
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The adhesion of as‐formed gas bubbles on the electrode surface usually impedes mass‐transfer kinetics and subsequently decreases electrolysis efficiency. Here it is demonstrated that nanostructured ...MoS2 films on conductive substrates show a faster hydrogen evolution reaction (HER), current increase, and a more‐stable working state than their flat counterpart by significantly alleviating the adhesion of as‐formed gas bubbles on the electrode. This study clearly reveals the importance of a nano‐porous structure for HER, which should be general and beneficial for constructing other gas‐evolution electrodes.
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•Well-textured nanopillars with various parameters were fabricated for the anti-icing behavior.•Nanopillars of very low top diameter irrelevant to height lead to reducing adhesion ...force and delaying freezing time.•Low top diameter of nanopillars also ensures the metastable Cassie-Baxter state based on energy barrier calculation.•Results demonstrated the important role of areal fraction and negligible contribution of height in anti-icing efficiency.
In this paper, we report the contributions of actual ice–substrate contact area and nanopillar height to passive anti-icing performance in terms of adhesion force and freezing time. Well-textured nanopillars with various parameters were fabricated via colloidal lithography and a dry etching process. The nanostructured quartz surface was coated with low-energy material to confer water-repellent properties. These superhydrophobic surfaces were investigated to determine the parameters essential for reducing adhesion strength and delaying freezing time. A well-textured surface with nanopillars of very small top diameter, regardless of height, could reduce adhesion force and delay freezing time in a subsequent de-icing process. Small top diameters of nanopillars also ensured the metastable Cassie–Baxter state based on energy barrier calculations. The results demonstrated the important role of areal fraction in anti-icing efficiency, and the negligible contribution of texture height. This insight into icing phenomena should lead to design of improved ice-phobic surfaces in the future.
Work was carried out to generate wheel/rail interface creep force data with the presence of leaf contamination. To enable this. the HAROLD full-scale wheel/rail test rig was upgraded to give friction ...measurement capability and methods for creating leaf layers were also developed.
A unique dataset has been created not previously available for full-scale test conditions and leaf layers. The work has shown the importance of the shear induced in the brake tests for creating the black, well-bonded leaf layer. It was found in the tests that ultra-low adhesion was achieved in all tests with leaves regardless of load applied and speed. The friction was also low for a number of braking events, even when the layer had been partially removed.
The wheel-rail contact is subjected to various environmental contaminations, while one of the most common is water. A numerical model has been used to evaluate friction in water-contaminated contact. ...The Greenwood and Tripp theory is used to calculate the load carried by asperities and liquid film. This model uses Kalker's simplified theory with an implemented third body layer to determine the frictional values of asperity contact and elastohydrodynamic theory for friction generated by liquid. The results are compared with experiments on two types of surface roughness. The results show the difference between elastic and plastic asperity deformation model, where the plastic model predicts more accurate transition in mixed lubrication regime. The plastic deformation model was used to predict traction curves.
•Numerical model for prediction of friction in water-contaminated contact was proposed.•Film thickness of water was measured and compared with prediction.•Model accounting for plastic deformations compared well with experimental data.•Traction curves for different speed were measured and compared with the model.
Top-of-rail products are commonly used for friction modification in wheel-rail contact. However, the effect of environmental conditions and contaminants on their performance remains unclear. In this ...study, three commercial top-of-rail products were contaminated by different amounts of water. The laboratory tribometer in ball-on-disc configuration was used to measure the coefficient of adhesion in contaminated contact. The results show that water influenced tested top-of-rail products significantly. A very low coefficient of adhesion occurred in tests with oil-based top-of-rail products suggesting that water could cause traction problems on the actual railway where friction modification is being used. Water-based top-of-rail products showed more resistance to water contamination.
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•A laboratory tribometer was used for the coefficient of adhesion (CoA) measurements.•Water had strong influence on the performance of tested top-of-rail (TOR) products.•Contamination of TOR products caused a long-lasting drop in CoA (lower than 0.05).•The results should be taken into account for further TOR product development.•Contamination of TOR products could cause traction problems on the actual railway.
The accurate control of surface structure and wettability has important practical significance. In this study, a precise and controllable method was presented to fabricate versatile ...polytetrafluoroethylene (PTFE) superhydrophobic surfaces (SHs) with controllable wettability, low adhesion and anti-icing ability by femtosecond laser micromachining. The fabricated SHs exhibited excellent superhydrophobicity with contact angle (CA) of 166°, rolling angle (RA) of ~2° and low adhesion properties. The Cassie-Baxter model and formula were generalized according to the hydrophobic-superhydrophobic double wettability model we proposed, the numerical simulation results were in good agreement with experimental results. The controllable wettability could be achieved and tunable by designing and micromachining desired surface structure. The fabricated PTFE SHs demonstrated outstanding active anti-icing ability under extremely low-temperature conditions below −20 ℃. Such versatile characteristics of PTFE SHs are promising for applications in precise control of structure and wettability in different fields of anti-icing, anti-adhesion, bio-chips, anti-drag and other innovative fields.
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A pine‐shaped Pt nanostructured electrode with under‐water superaerophobicity for ultrahigh and steady hydrogen evolution reaction (HER) performance is successfully fabricated by a facile and easily ...scalable electrodeposition technique. Due to the lower bubble adhesive force (11.5 ± 1.2 μN), the higher bubble contact angle (161.3° ± 3.4°) in aqueous solution, and the smaller size of bubbles release for pine‐shaped Pt nanostructured electrode, the incomparable under‐water superaerophobicity for final repellence of bubbles from submerged surface with ease, is successfully achieved, compared to that for nanosphere electrode and for Pt flat electrode. With the merits of superior under‐water superaerophobicity and excellent nanoarray morphology, pine‐shaped Pt nanostructured electrode with the ultrahigh electrocatalytic HER performance, excellent durability, no obvious current fluctuation, and dramatically fast current density increase at overpotential range (3.85 mA mV−1, 2.55 and 13.75 times higher than that for nanosphere electrode and for Pt flat electrode, respectively), is obtained, much superior to Pt nanosphere and flat electrodes. The successful introduction of under‐water superaerophobicity to in‐time repel as‐formed H2 bubbles may open up a new pathway for designing more efficient electrocatalysts with potentially practical utilization in the near future.
A Pt nanoarray electrode with under‐water superaerophobicity is fabricated by a facile and easily scalable electrodeposition technique. This electrode with a lower bubble adhesive force, a higher bubble contact angle in aqueous solution, and lower size of bubbles release, exhibits an ultrahigh electrocatalytic hydrogen evolution reaction performance, excellent durability, no obvious current fluctuation, and dramatically fast current density increase.
The phenomenon of surface ice accumulation in low temperature and high humidity environments brings significant challenges to economy, energy, and security. Superhydrophobic surfaces with micro-nano ...structures are considered as effective anti-icing surfaces. However, deicing can damage the micro-nano structures and increase the ice adhesion strength. Herein, a low-adhesion, superhydrophobic photothermal response coating was introduced by combining micro-nano surface and lubricated surface, which exhibits low adhesion self-healing photothermal de-icing performance. The surface temperature rises rapidly to 85 °C under 1 solar irradiation and the frozen droplet can melt within 150 s. The prepared coating has a contact angle of up to 162° and a rolling angle as low as 4.8°. The superhydrophobicity enabled the coating to have excellent anti-icing property with icing delay times up to 596 s. Ice and frost layers on the coating surface can melt and fall off illuminating with light. In addition, beeswax as phase change materials contributes to the coating's efficient self-healing properties. The coating can restore its excellent superhydrophobicity and surface morphology quickly via a simple heat treatment after suffering chemical and mechanical damage. The coating design strategy will provide inspiration for natural solar photothermal anti-icing surfaces and engineering applications.
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•Superhydrophobic, low surface energy and anti-icing surface are fabricated by simple spraying method.•Low adhesion and hierarchical micro-nano structures are obtained on the surface.•The self-healing performance are processed after chemical and mechanical damage.•Water contact angel of 161.7° and ice adhesion of 13.9 kPa are obtained.•Surface ice is efficiently removed by the photothermal conversion of CNTs.
•The structure is grown from the lubricant in the “endogenous SLIPS”.•Caprylyl methicone serves as both the diluent and the lubricant.•The coatings exhibit extremely low water sliding angles and ice ...adhesion.
Slippery lubricant-infused porous surfaces (SLIPSs) hold great promise in fields requiring adhesion resistance such as self-cleaning, anti-fouling, anti-icing, and anti-scaling. However, their road to practical application is still blocked by the complicated fabrication process and the restricted coating area. To address these challenges, we propose a new concept of endogenous SLIPS in which the porous structure grows from the solution coating of polypropylene/caprylyl methicone undergoing a thermally induced phase separation (TIPS) process. Caprylyl methicone serves as the diluent during TIPS as well as the lubricant in the SLIPS so that the coating can be fabricated in one step and unrestrictedly. The dissolution and phase separation mechanisms have been revealed by molecular dynamic simulation and in situ microscopic observation. Such SLIPSs exhibit impressive sliding property even for sticky and viscous liquids and exhibit extremely low ice adhesion in anti-icing tests.
