Superhydrophobic Pd@CeO2/Al2O3 catalyst coating for hydrogen mitigation systems in nuclear power plants

Passive autocatalytic recombination (PAR) was employed as an effective hydrogen mitigation system for nuclear power plants. Despite the great progress achieved in catalysts for PAR, few reports could be found on PAR catalysts, which exhibit strong resistance to poisoning by iodine compounds and the detrimental effect of water, as well as good anti-sintering properties. In this study, a superhydrophobic Pd@CeO₂/Al₂O₃ catalyst coating was prepared through a self-assembly method and the grafting of 1H,1H,2H,2H-perfluorooctyltriethoxysilane. The superhydrophobicity of the catalyst coating effectively alleviated water poisoning. The ceria shell of Pd@CeO₂/Al₂O₃ served as a protective layer against poisoning by iodine compounds because it was difficult for iodine vapor to access the catalyst core of the Pd nanoparticles when the shell pore diameter was below 1.2 nm. Given the interface effect between palladium and ceria, the CeO₂ shells also served as an effective barrier to prevent the Pd nanoparticles from aggregating at high temperatures. The superhydrophobic Pd@CeO₂/Al₂O₃ coating showed excellent potential for the mitigation of hydrogen containing various poisons during a nuclear accident.     

Superhydrophobic concrete surfaces with integrated microtexture

Ultra-High Performance Concrete (UHPC) is characterized by a densely packed mix-design, which can offer attractive surface properties for architectural building facades. A technical challenge for aesthetic applications is the protection against fouling. This work demonstrates that water-repellent concrete can be obtained just after demoulding by replicating the features of micro-pillared moulds made of polydimethylsiloxane (PDMS). Moreover, the negative replica of the microtextured UHPC surface can be used as a master to template for other UHPC samples, constituting a cost-effective route to fabricate large-scale microtextured concrete pieces. The chemical functionalization of UHPC with a low surface energy material is obtained by transferring residues from the PDMS mould or by spraying siloxane-based compounds to form a homogenous surface film. The latter preparation method showed superhydrophobic properties with static contact angles reaching up to 164° and contact angle hysteresis reaching as low as 2.5°. This process enables the manufacture of water-repelling, self-cleaning concrete. Raindrops slide off the concrete surface, carrying debris away.     

Electrochemical and mechanical properties of superhydrophobic aluminum substrates modified with nano-silica and fluorosilane

Nano-silica particles were deposited on acid-etched hydrophilic aluminum (Al) substrates by immersion in well-dispersed nano-silica aqueous suspension and tetramethylamonium hydroxide, followed by a heat treatment. The surface was then further treated by a reaction with fluorosilane. The hydrophobicity, surface morphology, and mechanical properties of the coated Al substrates were investigated, along with their electrochemical properties over time of exposure to two NaCl solutions (0.3% and 3% by weight). All the coated Al surfaces exhibited a water contact angle of 155–158°, i.e., superhydrophobicity. The use of nano-silica suspension significantly enhanced the hydrophobicity of the coated Al. Artificial neural networks were used to provide quantitative understanding in how the microstructure of the treated Al surface contributed to its superhydrophobicity and electrochemical properties. When R_{a, total} (nano-roughness + micro-roughness) exceeds 450 nm, WCA is greater than 154°, independent of the nano/micro-roughness ratio (RR_NM). FESEM and AFM images of these surfaces suggest that a rough two-length-scale hierarchical structure coupled with the low surface energy of fluorosilane topcoat led to the superhydrophobicity of the formed coatings. The coating prepared with the 0.2% nano-silica suspension (vs. other concentrations) featured the highest Young's modulus and the best corrosion protection to the Al substrate in both NaCl solutions.     

Fabrication of superhydrophobic surfaces with double-scale roughness

A surface with micro- and nano-scale ZnO (zinc oxide) structure was fabricated by alkaline hydrothermal method. The CA (contact angle) on this double-roughness surface was low (down to ∼ 0°), but after spin-coating Teflon, the CA was increased to ∼ 168°. By observing with SEM, a “rose” like ZnO crystal surface structure was found, which was responsible for both superhydrophilicity and superhydrophobicity. The prepared surface also showed high chemical stability even after immersing the sample in water for 15 days. The method is simply controllable, cost-effective, and has a wide range of potential applications such as self-cleaning superhydrophobic coating on large areas of different substrates.     

Superhydrophobic optically transparent silica films formed with a eutectic liquid

A eutectic liquid (choline chloride and urea) that served as a templating agent in sol-gel processing was used to prepare thin silica films on glass microscope slides. Subsequent extraction of the eutectic liquid yielded a film with a rough surface. After treating the film surface with a fluoroalkyl silane, the surface became superhydrophobic with a contact angle ∼ 170° and a contact angle hysteresis < 10°. The optical transmittance of the film coated on the glass slide was comparable to that of the microscope glass slide. Atomic Force Microscopy (AFM) was used to characterize the surface structures; a tipless probe allowed measurement of the force of interaction with superhydrophobic surfaces. The interaction force between the AFM probe and the superhydrophobic surface was reduced greatly compared to that between the probe and the flat surface treated with fluoroalkyl silane.     

Stable,Superhydrophobic, and Conductive Polyaniline/Polystyrene Films for Corrosive Environments

A polyaniline/polystyrene composite film with a lotus‐leaf‐like structure is prepared via a simple electrospinning method. The film shows stable superhydrophobicity and conductivity, even in many corrosive solutions, such as acidic or basic solutions over a wide pH range, and also in oxidizing solutions. The special surface composition and morphology are the two important aspects that induce such unusual properties. The polystyrene content can strongly influence the morphology of the composite films, which thus display different superhydrophobicities and conductivities.     

Design and Creation of Superwetting/Antiwetting Surfaces

Recent achievements in the construction of surfaces with special wettabilities, such as superhydrophobicity, superhydrophilicity, superoleophobicity, superoleophilicity, superamphiphilicity, superamphiphobicity, superhydrophobicity/superoleophilicity, and reversible switching between superhydrophobicity and superhydrophilicity, are presented. Particular attention is paid to superhydrophobic surfaces created via various methods and surfaces with reversible superhydrophobicity and superhydrophilicity that are driven by various kinds of external stimuli. The control of the surface micro‐/nanostructure and the chemical composition is critical for these special properties. These surfaces with controllable wettability are of great importance for both fundamental research and practical applications.     

Hydrophobic over-recovery during aging of polyethylene modified by oxygen capacitively coupled radio frequency plasma: A new approach for stable superhydrophobic surface with high water adhesion

In this work, a new approach for the stable superhydrophobic surface with a high water adhesion has been found from an aging process at a high aging temperature of 90 °C during an aging time up to 24 h for the low density polyethylene (LDPE) modified by the oxygen capacitively coupled radio frequency plasma (CCP) under a radio frequency (RF) power of 200 W for an exposure time of 5 min. The plasma nanotexturing produced the nanofibrils array on the LDPE surface showing the contact angle of approximately 0°. During the aging process, the as-modified superhydrophilic LDPE surface underwent a hydrophobic over-recovery into the superhydrophobicity with a pinned water droplet showing the contact angle higher than 150°. A time-dependent contact angle model on the nanotextured surface was developed from the Cassie's equation for the heterogeneous surface containing different wetting patches, to describe the hydrophobic over-recovery due to the surface restructuring on the nanofibrils array. The stable superhydrophobicity with the high water adhesion was attributed to the CCP modified LDPE surface with the nanofibrils composed of the heterogeneous chemical compositions of polar and nonpolar chains/groups after the aging process.     

Fabrication of superhydrophobic TiO2 quadrangular nanorod film with self-cleaning,anti-icing properties

Superhydrophobic TiO₂ quadrangular nanorod film was fabricated by hydrothermal reaction and stearic acid modification. X-ray diffractometer and Fourier transform infrared spectrometer were employed to characterize the surface crystal structures and chemical compositions of the superhydrophobic TiO₂ film, respectively. The effects of the titanium source (titanium tetraisopropoxide (TTIP)) amount and reaction time on the morphology and wettability of the TiO₂ film were studied by scanning electron microscope and contact angle meter. The results show that the diameter of the TiO₂ quadrangular nanorods increases and then the water contact angle on modified TiO₂ film decreases with the increase of the reaction time and TTIP amount. Moreover, when the TTIP amount is 0.3?mL and solvent is 30?mL, the wetted state of the superhydrophobic TiO₂ film surface conforms to an improved Cassie model. Besides, the superhydrophobic TiO₂ film shows good low adhesion, self-cleaning and anti-icing properties. Particularly, the anti-icing property decreases with the increase of the reaction time and TTIP amount.