Silicone/graphene oxide co-cross-linked aerogels with wide-temperature mechanical flexibility,super-hydrophobicity and flame resistance for exceptional thermal insulation and oil/water separation

Development of multifunctional and high-performance silicone aerogel is highly required for various promising applications.However,unstable cross-linking structure and poor thermal stability of silicone network as well as complicated processing restrict the practical use significantly.Herein,we report a facile and versatile ambient drying strategy to fabricate lightweight,wide-temperature flexible,super-hydrophobic and flame retardant silicone composite aerogels modified with low-content functionalized graphene oxide(FGO).After optimizing silane molecules,incorporation ofγ-aminopropyltriethoxysilane functionalization is found to promote the dispersion stability of GO during the hydrolysis-polymerization process and thus produce the formation of unique strip-like co-cross-linked network.Consequently,the aerogels containing∼2.0 wt%FGO not only possess good cyclic compressive stability under strain of 70%for 100 cycles and outstanding mechanical reliability in wide temperature range(from liquid nitrogen to 350℃),but also display excellent flame resistance and super-hydrophobicity.Further,the optimized silicone/FGO aerogels display exceptional thermal insulating performance superior to pure aerogel and hydrocarbon polymer foams,and they also show efficient oil absorption and separation capacity for var-ious solvents and oil from water.Clearly,this work provides a new route for the rational design and development of advanced silicone composite aerogels for multifunctional applications.

A Study of the Truncated Square Pyramid Geometry for Enhancement of Super-hydrophobicity

Super-hydrophobic surfaces are quite common in nature,inspiring people to continually explore its water-repellence property and applications to our lives.It has been generally agreed that the property of super-hydrophobicity is mainly contributed by the microscale or nanoscale(or even smaller)architecture on the surface.Besides,there is an energy barrier between the Cassie-Baxter wetting state and the Wenzel wetting state.An optimized square post micro structure with truncated square pyramid geometry is introduced in this work to increase the energy barrier,enhancing the robustness of super-hydrophobicity.Theoretical analysis is conducted based on the wetting transition energy curves.Numerical simulation based on a phase-field lattice Boltzmann method is carried out to verify the theoretical analysis.The numerical simulation agrees well with the theoretical analysis,showing the positive significance of the proposed micro structure.Furthermore,another novel micro structure of rough surface is presented,which combines the advantages of truncated pyramid geometry and noncommunicating roughness elements.Theoretical analysis shows that the novel micro structure of rough surface can effectively hinder the Cassie-Baxter state to Wenzel state transition,furthefly enhancing the robustness of the surface hydrophobicity.

Developing super-hydrophobic and corrosion-resistant coating on magnesium-lithium alloy via one-step hydrothermal processing

Formation of super-hydrophobic and corrosion-resistant coatings can provide significant corrosion protection to magnesium alloys.However,it remains a grand challenge to produce such coatings for magnesium-lithium alloys due to their high chemical reactivity.Herein,a one-step hydrothermal processing was developed using a stearic-acid-based precursor medium,which enables the hydrothermal conversion and the formation of low surface energy materials concurrently to produce the super-hydrophobic and corrosion-resistant coating.The multiscale microstructures with nanoscale stacks and microscale spheres on the surface,as well as the through-thickness stearates,lead to the super-hydrophobicity and excellent corrosion resistance of the obtained coating.

Super-hydrophobic characteristics of butterfly wing surface

Many biological surface are hydrophobic because of their complicated composition and surface microstructure. Eleven species (four families) of butterflies were selected to study their micro-, nano-structure and super-hydrophobic characteristic by means of Confocal Light Microscopy, Scanning Electron Microscopy and Contact Angle Measurement. The contact an- gles of water droplets on the butterfly wing surface were consistently measured to be about 150 ? and 100 ? with and without the squamas, respectively. The dust on the surface can be easily cleaned by moving spherical droplets when the inclining angle is larger than 3 ?. It can be concluded that the butterfly wing surface possess a super-hydrophobic, water-repellent, self-cleaning, or “Lotus-effect”characteristic. The contact angle measurement of water droplets on the wing surface with and without the squamas showed that the water-repellent characteristic is a consequence of the microstructure of the squamas. Each water droplet (diameter 2 mm) can cover about 700 squamas with a size of 40 m×80 m of each squama. The regular riblets with a width of 1000 nm to 1500 nm are clearly observed on each single squama. Such nanostructure should play a very important role in their super-hydrophobic and self-cleaning characteristic.

NANO-TRIBOLOGICAL STUDY ON A SUPER-HYDROPHOBIC FILM FORMED ON ROUGH ALUMINUM SUBSTRATES

A novel super-hydrophobic stearic acid(STA)film with a water contact angle of 166° was prepared by chemical adsorption on aluminum wafer coated with polyethyleneimine(PEI)film. The micro-tribological behavior of the super-hydrophobic STA monolayer was compared with that of the polished and PEI-coated Al surfaces.The effect of relative humidity on the adhesion and friction was investigated as well.It was found that the STA monolayer showed decreased friction,while the adhesive force was greatly decreased by increasing the surface roughness of the Al wafer to reduce the contact area between the atomic force microscope(AFM)tip and the sample surface to be tested.Thus the friction and adhesion of the Al wafer was effectively decreased by generating the STA monolayer, which indicated that it could be feasible and rational to prepare a surface with good adhesion resistance and lubricity by properly controlling the surface morphology and the chemical composition.Both the adhesion and friction decreased as the relative humidity was lowered from 65% to 10%,though the decrease extent became insignificant for the STA monolayer.

Antibacterial and Corrosion Inhibition Properties of SA-ZnO@ODA-GO@PU Super-Hydrophobic Coating in Circulating Cooling Water System

In order to solve the corrosion problem of circulating cooling water system,SA-ZnO@ODA-GO@PU super-hydrophobic coating was synthesized for pipeline protection.After hydrophobic modification,the contact angle(CA)of the coating was above 150°.The antibacterial ability of coating was essential for corrosion protection.SA-ZnO@ODA-GO can seriously damage the cell structure,make the cell content outflow,increase the leakage rate of protein,and make the bacteria unable to reach logarithmic growth phase within 24 h.The corrosion inhibition mechanism analysis of SA-ZnO@ODA-GO@PU coating indicated that the hydrophobic coating as a physical barrier can prevent the water molecules from entering the carbon steel and prevent the surface charge transfer.

Influence of Li^(+)/Al^(3+) on the corrosion behavior of Li-Al layered double hydroxides(LDHs) film on LA51 magnesium alloys

A hierarchical superhydrophobic Al-Li layered double hydroxide(LDH)films with different Li^(+)/Al^(3+)molar ratios of 1:1,1:2,2:1,p H value of 11.5 and reaction temperature of 125°C,have been fabricated on the surface of Mg-5Li-1Al(LA51)alloys by hydrothermal method following the characteristics of controllable cation structure and exchangeable anion between layers.The properties of the films were investigated by X-ray diffractometer(XRD),scanning electron microscope(SEM)and energy dispersive spectrometer(EDS).XRD and SEM results indicate that the Al-Li LDH films are successfully prepared on LA51 alloys.The contact angle(CA)was measured to be about100.7°,indicating that the surface wettability of the film converted from hydrophilic to hydrophobic by surface modification.The corrosion resistance of Al-Li LDH films was evaluated by Tafel polarization curve and electrochemical impedance spectroscopy(EIS).Surprisingly,Tafel polarization curve and EIS test reveal that the Al-Li LDH films prepared at the molar ratio of Li^(+)/Al^(3+)1:2,p H 11.5 and temperature125°C have better corrosion resistance in 0.1 M Na Cl neutral solution.In addition,the formation mechanism and corrosion mechanism of the films on the surface of LA51 alloy are also proposed.It provides innovative synthetic materials and novel design ideas for the preparation of high-efficiency anti-corrosion coatings on LA51 alloys,whose application can be extended in industrial fields.

Anisotropism of the Non-Smooth Surface of Butterfly Wing

Twenty-nine species of butterflies were collected for observation and determination of the wing surfaces using a Scanning Electron Microscope(SEM).Butterfly wing surface displays structural anisotropism in micro-,submicro- and nano-scales.The scales on butterfly wing surface arrange like overlapping roof tiles.There are submicrometric vertical gibbosities,horizontal links,and nano-protuberances on the scales.First-incline-then-drip method and first-drip-then-incline method were used to measure the Sliding Angle(SA)of droplet on butterfly wing surface by an optical Contact Angle(CA)measuring system. Relatively smaller sliding angles indicate that the butterfly wing surface has fine self-cleaning property.Significantly different SAs in various directions indicate the anisotropic self-cleaning property of butterfly wing surface.The SAs on the butterfly wing surface without scales are remarkably larger than those with scales,which proves the crucial role of scales in determining the self-cleaning property.Butterfly wing surface is a template for design and fabrication ofbiomimetic materials and self-cleaning substrates.This work may offer insights into how to design directional self-cleaning coatings and anisotropic wetting surface.

The Fabrication of Microstructure Surface of Superhydrophobic Coating by Surface Gelation Technology

The microstructured surface of materials were fabricated by a two-step acid-base catalyzed sol-gel process. In fluorinated polymer with PTFE doping, the well-proportioned composite sols were prepared using sol-gel processing under the hydrochloric acid and deficiency of water conditions. After the substrate was coated by composite sols, and the gelation treatment on the surface of composite coating, the micrometer-scale and nanometer-scale hierarchical structures were formed in surface layer of material. XPS and TEM technologies were employed to identify that the gelation occurs just on the surface of composite coating. The morphology of coating surface was observed by SEM and AFM technologies. The microstructured surface of material can be fabricated using this inexpensive and easily controlled method on low surface energy resin materials, the super-hydrophobic coatings materials can be prepared.

Microstructure Characterization and Oil Absorption Performance of Superhydrophobic Cotton Cellulose Aerogel

Superhydrophobic cotton cellulose (CC) aerogel was prepared from budget cotton with huge output.CC aerogels were synthesized by using commercial cotton extract as a precursor through the nano-self-assembly process,CO2 supercritical drying process,and vapor deposition.Typical,uniform hydrophobic CC aerogel structure can be confirmed by several characterization techniques.Maximum specific surface areas before and after modification are 213.80 m^(2)·g^(-1) and 184.33 m^(2)·g^(-1)with average pore sizes at 14.01 nm and 32.56 nm.The water contact angle is up to 153°,showing its superhydrophobic property.The maximum adsorption efficiency can be up to 16.0 g·g^(-1),which exhibits excellent cycling property after 5 adsorption tests.The oil absorption mechanism of the superhydrophobic CC aerogels is investigated in detail as well.This superhydrophobic CC aerogel has excellent adsorption performance and simple,rapid,effective oil contamination treatment which has promising applications in the field of oil adsorption and water remediation in oil adsorption.

A Low Cost and Facile Preparation of Hydrophobic Silica Films and Powders by a Solution-based Process

Super-hydrophobic surfaces with water contact angle （WCA） higher than 150~ generated a lot of interests both in academic and in industry because of their self-cleaning functionality. Emphasis was given to the effect of pH value on the hydrophobic behavior of the obtained films or powders. At first, SiC）2 sols were prepared by diluted ammonia. We found that following the increase of pH value of sol from 8 to 9, WCAs of the obtained films increased from 121.8~ to 131.8~. Following the continued increase of the pH value of sol, precipitates began to appear and smooth film could not be obtained. The WCAs of the obtained powders could reach 121.7~, and through modifying by TMCS could further increase to as high as 165~ and the water sliding angle （WSA） was 2~. The results of SEM indicate that the hydrophobic properties of the powders without modifying by TMCS should be originated from the formation of nano/micron binary structure, i e, a micron- scale diameter and a nano-scale surface roughness. In this work we provide a better solution to fabricate super- hydrophobic silica coating surface with a simple method at low cost.

Preparation and Characterization of PVC/PAN Membrane Used as Medical Exhaust Membranes

The wet phase inversion process was used to prepare a kind of medical exhaust membranes with super-hydrophobicity and good gas permeability capacity by using non-woven fabric as the support base.The influences of solution temperature,the evaporation time,the content of the non-solvent additive and the ratio of polyvinyl chloride(PVC)/polyacrylonitrile(PAN) on the gas permeability capacity and hydrostatic pressure of the resultant membranes were investigated.A kind of composite membrane with gas permeability about 2 800 mL/min and hydrostatic pressure of 36 kPa was obtained.In addition,the relationship between the properties and structure of the membrane was analyzed.

Synthesis and Characterization of Superhydrophobic-Superoleophobic and Anti-Corrosion Coatings via Sol-Gel Process

Superoleophobic nanocomposite coatings with improved hydrophobic properties were obtained by incorporation of a perfluoroalkyl polymer in hybrid sol-gel matrix containing silica and titania nanoparticles. SiO2 and TiO2 nanoparticles were synthesized based on sol-gel precursors utilizing tetraethyl orthosilicate, 3-glycidoxypropyl trimethoxysilane, and tetra (n-butyl orthotitanate). SEM and EDX images of the coating demonstrated that a Silica nanosphere had been aggregated in superporous structure. The analysis results show that nano-sized inorganic particles (10 - 20 nm) have a uniform distribution and dispersion. By increasing the PFOTES, the oleophobicity of coatings increased due to lowering of surface energy in the presence of fluoropolymer. Results of EIS measurement show that PFOTES and TiO2 nanoparticles increased anti-corrosion property of hybrid coatings. This method introduces a simple way to produce water- and oil-repellent self-cleaning coatings on large areas of different substrates like glass, ceramic, metal and composites.

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.

Stability Mechanism of Laser-induced Fluorinated Super-hydrophobic Coating in Alkaline Solution

Great attention has been focused on super-hydrophobic surfaces due to their fantastic applications.Fluoride chemicals are widely used to fabricate super-hydrophobic surfaces due to their convenience,simplicity,and high efficiency.Previous research has made extensively efforts on corrosion resistance of fluorinated super-hydrophobic surfaces in corrosive media.Nevertheless,rare papers focused on the underlying reasons of anticorrosion property and stability mechanism on the fluorinated super-hydrophobic coatings in alkaline solution.Therefore,this work aims to reveal these mechanisms of fluorinated super-hydrophobic copper samples in strong alkaline solution(pH 13).Through the characterization of surface wettability and surface morphology,the laser-induced super-hydrophobic surface retained excellent stability after soaking in alkaline solution for 4 h.Through measurement of chemical compositions,the anticorrosion mechanism and stability mechanism of the fluorinated super-hydrophobic surface were proposed.Importantly,the hydroxyl ion(OH−)can further promote the hydrolysis reaction to improve the density and bonding strength of the fluoride molecules.Finally,the electrochemical experiments(PDP and EIS tests)were conducted to validate the rationality of our proposed conclusions.

Hybrid Laser Ablation and Chemical Modification for Fast Fabrication of Bio-inspired Super-hydrophobic Surface with Excellent Self-cleaning,Stability and Corrosion Resistance

Although laser ablation is considered as a facile technique to fabricate bio-inspired super-hydrophobic surfaces,the issue is that the initial laser treated metallic surfaces show super-hydrophilic property.It will take a long period to reach super-hydrophobic state under ambient air.It is reported that these super-hydrophobic surfaces could be easily damaged by thermal heating effect or interaction with other liquids,causing uncontrolled loss of super-hydrophobicity.In this study,a stable super-hydrophobic aluminum surface was rapidly fab-ricated via the hybrid laser ablation and surface chemical modification of(heptadecafluoro-1,1,2,2-tetradecyl)triethoxysilane(AC-FAS).Surface morphology and chemistry were systematically investigated to explore the generation mechanism of super-hydrophobicity.The water contact angle of the treated surfaces can reach up to 160.6°±1.5°with rolling angle of 3.0°±1.0°,exhibiting perfect self-cleaning capability,long-term stability,and excellent chemical stability in acidic as well as alkaline solutions.The potentiodynamic polarization tests implied that the super-hydrophobic surfaces showed better anti-corrosion performance.This hybrid laser ablation and surface chemical modification are very time-saving and low-cost,which offers a rapid way for quantity production of super-hydrophobic surface on aluminum material.

Fabrication of a Bionic Needle with both Super-Hydrophobic and Antibacterial Properties

Many biological surfaces possess unusual micro-nano hierarchical structures that could influence their wettability, which provide new methods for the construction of novel materials. In this work, silver nanoparticles were successfully coated on the surface of stainless steel needle by a simple electroless replacement reaction process between the AgNO3 solution and the activated stainless steel needle. After the replacement reaction, porous micro/nanostructures were formed on the surface of the stainless steel needle. By modifying long chains ofthiol molecules, the stainless steel needle exhibited good super-hydrophobic property with a contact angle greater than 150°. Moreover, the silver coated stainless steel needle （bionic needle） showed strong antibacterial activity against the gram-negative bacterium Escherichia coli （E. colO. By calculating the area of the inhibition zone against E. coil formed on agar medium, the antibacterial activity of the bionic needle with the contact angle of 152° is much better than that with the contact angle of 138°. The as-prepared bionic needle with both super-hydrophobie and antibacterial properties has the potential to be applied in modem medical devices.

Self-cleaning and Oil/Water Separation of 3D Network Super-hydrophobic Bead-like Fluorinated Silica Pellets/Poly(aryl ether ketone)Composite Membrane Fabricated via a Facile One-step Electrospinning

Novel super-hydrophobic fluorinated silica pellets/poly(aryl ether ketone)composite membranes with controllable structure have been prepared through incorporating poly(aryl ether ketonc)s with(3-triluoromethyl)-phenyl side groups and fluorinated silica pellets(F-SiO2)by a facile one-step electrospinning.Under the condition of adding 50%(mass fraction)F-SiO2 in the composite membrane,the water contact angle(WCA)reached its maximum(157°±4.3°).The controllable micro/nano-structures grown on the electrospun fibers could be regulated by the F-SiO2 loading,which was illustrated by scanning clectron microscopy(SEM).Moreover,these super-hydrophobic mem-branes also demonstrated excellent durability,anti-fouling property and oil-water separation ability after 200 h of water flushing.These promising PAEK composite membranes with controllable structure have the potential values in large-scale application of filtration,oil-water separation and antifouling.