Recent progress in superhydrophobic and superamphiphobic coatings for magnesium and its alloys

Superhydrophobic coatings are projected as a practical approach to tackle the weak aqueous corrosion resistance of Mg/Mg alloys.The present review provides the most recent updates in this area.The various low surface energy treatments reported are presented first,followed by the methods employed for developing hierarchical surface micro/nanostructuring.Reported works in different application areas,including anti-corrosion,biomedical and anti-icing are systematically discussed.Concise descriptions of self-healing characteristics and long-term durability of the superhydrophobic surfaces provided.Reports on superamphiphobic surfaces also deliberated.

Wettability-driven synergistic resistance of scale and oil on robust superamphiphobic coating

Disgusting deposits(e.g.,scale and crude oil)in daily life and industrial production are always serious problems,posing great threats to the safety and economic development.However,most of developed coatings can only conquer one part of these deposits such as superhydrophobic coatings possess antiscaling capacity but would adhere crude oil.To integrate scale resistance with oil repellence,we herein report a robust superamphiphobic(SAB)coating simultaneously reducing pollution of scale and oil for extended period of time(two weeks with over 98%reduction).Compared with single role of superhydrophobic and amphiphilic surfaces,the SAB coating can not only inhibit interfacial nucleation of scale but also reduce the adhesion of formed scale and polluted oil.The durability of the SAB coating is evaluated via mechanical tests(sandpaper abrasion,tape stripping and sand falling)and chemical corrosion(corrosive liquid immersing),revealed by sustainable high contact angles and low contact angle hysteresis of water and oil.The universality of this strategy can be further confirmed by adding different particles like kaolin,Al_(2)O_(3),and SiO_(2),resisting multiple types of scale(i.e.,CaSO_(4),BaSO_(4)and MgCO_(3))and oil(i.e.,glycerol,glycol,and mineral oil).Therefore,this study provides an ideal avenue for resisting scale and oil,which may be used for conquering the complexity of application environments(e.g.,oil production and transportation).

Robust superamphiphobic coatings with gradient and hierarchical architecture and excellent anti-flashover performances

Biomimetic superhydrophobic(SH)coatings have emerged as a promising alternative to traditional room temperature vulcanizing(RTV)silicone rubber coatings for improving the flashover strength of insulators.However,organic contamination occurs in outdoor applications and thus a superamphiphobic(SAP)surface is more desirable but not yet reported for improving flashover performance.Herein,we developed a novel anti-flashover technique by fabricating robust SAP coating with unique gradient and micro-nanoscale hierarchical architecture.The SAP coating was fabricated by sequentially spray-depositing a resin-based primer and a silica-based topcoat on substrates(i.e.,glass slides and insulators).The primer not only functions as an adhesive offering strong adhesion to the substrate but also offers a micromastoid-like structure facilitating the subsequent formation of hierarchical micro-nanostructure.The appropriate spraying pressure leads to a diffusion of the fluorocarbon-modified silica nanoparticles into the primer to form a unique gradient structure,by analogy to inserting bullets into a wood.These features render the SAP coating excellent robustness with strong abrasive resistance,excellent ultraviolet(UV)resistance,and excellent chemical and thermal stability.Pollution flashover property of the SAP coating was explored and compared with that of SH and RTV specimens,from which a novel organic-contamination model to evaluate the flashover performance was proposed.The coated SAP glass insulator demonstrated 42.9%pollution flashover voltage improvement than RTV-coated insulator.These stated unique features reveal the convincing potential of the present SAP coatings to be applied for not only outdoor transmission line insulators for antiflashover but also other fields for self-cleaning,anti-fouling,and anti-icing.

Advance in Structural Classification and Stability Study of Superamphiphobic Surfaces

Superamphiphobic surfaces have great potential applications in flame resistance,anti-icing,self-cleaning,anti-adhesion,micro-flow control and so on.However,the surface durability is poor owing to the limitation of design principles.In recent years,a lot of efforts have been carried out on the morphology,structure,and stability of superamphiphobic surfaces,resulting in significant improvement in their surface superwetting properties.In this review,we present a brief classification of the morphological types of superamphiphobic surfaces and summary of the recent progress of researches on the stability of superamphiphobic surfaces.Several testing methods of mechanical and chemical stability are listed in the article,together with the characteristic results,to provide a better and more detailed understanding of the current research status on superamphiphobic surface stability,which will be of considerable importance as a reference guide for our future researches.Of course,there are still some issues that need to be addressed for the application of superamphiphobic surfaces at large scale,and this is where our future researches will be directed.Finally,we discuss the challenges as well as the prospects in the study of superamphiphobic surfaces.

Underwater Oil Wettability on Nanostructured Superamphiphobic Surface Tuned by Trapped Air Layer Continuity

When the superamphiphobic meshes are immersed in water, the rough structures on steel wires are filled with air. The nanostructured superamphiphobic surfaces were prepared on the stainless-steel mesh. By adjusting the mesh size of the surface, the continuity of trapped air layer on the superamphiphobic surface underwater could be controlled. Then the underwater oil-wetting behavior on the prepared superamphiphobic mesh was investigated. The oil droplet spread out on the superamphiphobic surface without mesh and exhibited an oil contact angle of about 0° under water. But the oil contact angle formed on the superamphiphobic mesh surfaces and extended with increasing mesh size. We thought the discontinuity of trapped air layer on the surface and the entry of water into interval between the steel wires should be responsible for these behaviors.

Snakeskin‑Inspired Hierarchical Winkled Surface for Ultradurable Superamphiphobic Fabrics via Short‑Fluorinated Polymer Reactive Infusion

Durable superamphiphobic surfaces are highly desired for real-world applications such as self-cleaning,anti-fouling,personal protection,and functional sportswear.However,challenges still exist in constructing robust superamphiphobic surfaces by using short-fluorinated polymers as one of the promising alternatives for environmentally unfriendly long perfluorinated side-chain polymers.Hierarchical patterns on biological skins endow the creatures with a specific surface for survival.Here,a facile strategy was proposed to generate hierarchical wrinkles for ultradurable superamphiphobic fabrics by simulating the deformation adaptability of snakeskin.Snake-like hierarchical winkling was constructed by the infusion of reactive perfluorooctyltriethoxysilane(FOS)in a wet chemical plus vapor polymerization process.Upon the infusion of FOS,the mismatch of shrinkage caused by gradient crosslinking leads to the formation of a soft wrinkled poly(perfluorooctyl trieth-oxysilane)(poly-FOS)surface.Such a snakeskin-like hierarchical wrinkled surface and high fluorine density of poly-FOS endowed the treated superamphiphobic fabrics with high water resistance(contact angle 169°),castor oil resistance(154°),and extraordinary durability(withstanding 100 standard laundries,15,000 rubbing cycles and strong acid and alkali solu-tions).Moreover,a superamphiphobic surface can be formed on various substrates,including fabric,wood,paper,and glass.This work thus gives new insights into the environmentally friendly manufacture of ultradurable superamphiphobic fabrics.

Fabrication of a superamphiphobic coating by a simple and flexible method

A facile and flexible method to prepare raspberry-like nanoparticles that can be used as a superamphipho- bic coating is reported. Anatase TiO2 nanoparticles were chosen as the core because of their irregular morphology and photocatalytic performance. Anatase TiO2 nanoparticles were surrounded tightly by tiny functional fluoride-silica nanoparticles via the hydrolysis-condensation reaction of tetraethoxysi- lane and IH, 1H, 2H, 2H-perfluorodecyl triethoxysilane. The obtained Si-F@TiO2 nanoparticles can be sprayed or dipped directly onto various substrates. The coated film exhibited quite good liquid resistance, even when subjected to water jetting and sand abrasion. The photocatalytic effect of the coated anatase TiO2 with respect to formaldehyde was also studied and discussed. This method will provide more opportunities and fast access to practical applications in surface, environmental, and energy engineering.

Robust,flame-retardant and colorful superamphiphobic aramid fabrics for extreme conditions

High-performance superamphiphobic fabrics are very useful in special fields,such as firefighting,rescue,and polar sports.The complicated preparation process,easily damaged surface structure,and high cost drastically limit their commercial application.In this work,we utilized a simple,low-cost superamphiphobic coating to prepare a superamphiphobic aramid fabric(SAF).The excellent repellency to acid/alkali solutions and low boiling point organic solvents has been demonstrated with the contact angle of>150°and>130°,respectively.Additionally,the original color of the fabric can also be maintained,accompanied by superior flame retardancy,strength and comfort with thermal degradation of 361℃.More importantly,SAF displayed excellent durability via 50 standard machine washes,100-min of ultrasonic washing,10-min of UV irradiation,120-min of high-temperature heating,5000 cycles of abrasion,and destructive abrasion by sharp metal.All the results showed the superior performance of our SAF in protective fabrics under extreme environmental conditions.

Construction of mechanically robust superamphiphobic surfaces on fiber using large particles

Superamphiphobic surfaces have attracted the attention of researchers because of their broad application prospects.Currently,superamphiphobicity is primarily achieved by minimizing the solid-liquid contact area.Over the past few decades,researchers have primarily focused on using physical deposition methods to construct superamphiphobic surfaces using fine-sized nanoparticles(<100 nm).However,porous hollow SiO_(2)particles(PH-SiO_(2)),which aretypically large spheres,have a highly hierarchical structure and can provide lower solid-liquid contact fractions than those provided byfine-sized particles.In this study,we used PH-SiO_(2)as building blocks and combined them with poly(dimethylsiloxane)to construct a mechanically robust coating on fiber by spray-coating.After chemical vapordeposition treatment,the coating exhibited excellent superamphiphobicity and could repel various liquids,covering a wide rangeof surfacetensions(27.4-72.0mN-m^(-1)).

A Review on Self-Cleaning Coatings for Tunnels

Self-cleaning coatings for tunnels can effectively remove dust and stains accumulated over the surface of tunnel linings and their appurtenances due to the closed environment and poor ventilation.This paper systematically introduces the current research status of self-cleaning coatings for tunnels,focusing on the development of super-hydrophobic self-cleaning coatings,superamphiphobic self-cleaning coatings,exhaust gas degradation coatings,fire retardant coatings,and tunnel de-icing coatings.The advantages and disadvantages of the five functional coatings are then briefly described,and the problems of self-cleaning coatings for tunnels at the present stage are pointed out.Finally,the development direction of self-cleaning coatings for tunnels is proposed to provide a reference for the research and application of self-cleaning coatings for tunnels.

Bio-inspired special wetting surfaces via self-assembly

Self-assembly is the fundamental principle, which can occur spontaneously in nature. Through billions of years of evolution, nature has learned what is optimal. The optimized biological solution provides some inspiration for scientists and engineers. In the past decade, tinder the multi-disciplinary collaboration, bio-inspired special wetting surfaces have attracted much attention for both fundamental research and practical applications. In this review, we focus on recent research progress in bio-inspired special wetting surfaces via self-assembly, such as low adhesive superhydrophobic surfaces, high adhesive superhydrophobic surfaces, superamphiphobic surfaces, and stimuli-responsive surfaces. The challenges and perspectives of this research field in the future are also briefly addressed.

Top-down Approach for Fabrication of Polymer Microspheres by Interfacial Engineering

Polymer microspheres with uniform size,composition,and surface property have gained extensive researches in past decades.Conventional bottom-up approaches are using monomers or oligomers to build up desired polymer microspheres.However,directly shaping high-molecular-weight polymers into well-ordered polymer microspheres remains a great challenge.Herein,we reported a facile and efficient top-down approach tofabricate microspheres with high-molecular-weight polymer microfibers.By harnessing interfacial engineering-control during the polymer microspheres formation,uniformly sized microspheres could be produced with widely ranged diameters(from 10μm to the capillary length of each polymer melt).The size limitation of this approach could be further extended by a controllable Plateau-Rayleigh instability phenomenon.Principally,the top-down approach allows fabrication of microspheres by various polymer melts with surface energy higher than 25 mN/m.Our work paves a way for green,cost-effective,and customizable production of a variety of functional polymer microspheres without any chemical reaction assistant.