Fabrication of robust superhydrophobic coatings using PTFE‐MWCNT nanocomposite: Supercritical fluid processing

Fabrication of polymer‐carbon composite nanostructure with good dispersion of each other is critical for the desired application due to the nanostructure flaws, agglomeration, and poor absorption between the 2 materials. Fabrication of superhydrophobic surface coating composites of polytetrafluoroethylene (PTFE) with multiwalled carbon nanotubes (MWCNTs) through supercritical fluid processing was explored in this study. Homogeneity of the composite was characterized by X‐ray diffraction and Raman spectroscopy studies, which reveal that the PTFE and MWCNT are uniform in the composite. Microstructural surface evaluation of field‐emission scanning electron microscope and high‐resolution transmission electron microscope studies display that the coating composite possesses roughness structures and fibrillation of the superhydrophobic surface coating. Superhydrophobic character was evaluated on fiber‐reinforced plastic (FRP) sheets, which showed that the prepared coating composite surface showed self‐cleaning properties with a high water contact angle of 162.7°. The surface wettability was studied by increasing different temperatures (30°C to 300°C) in PTFE‐MWCNT composite, which reveals that the FRP sheets were thermally stable up to 200°C and afterward; they transformed from superhydrophobic to hydrophilic state at 250°C. The superhydrophobic surfaces are thermally stable in extreme environmental conditions, and this technique may be used and extendable for large‐scale applications.     

Fabrication and anti‐corrosion property of superhydrophobic hybrid film on copper surface and its formation mechanism

Compact and uniform superhydrophobic films were prepared on copper substrates using one‐step solution‐immersion process, and the appropriate preparation conditions were selected for mixed solutions. SEM shows that the hybrid film of 1‐dodecanethiol and tetradecanoic acid on copper substrate is more compact with the contact angle of 160°. The electrochemical impedance spectroscopy and polarization test demonstrate that the anti‐corrosion property of surface‐modified copper substrate is greatly improved, especially for the hybrid film. Moreover, the competitive adsorption process and adsorptive geometry of hybrid film were well explained based on the results of quantum chemistry calculations, SEM, and energy dispersive X‐ray analysis. Copyright © 2009 John Wiley & Sons, Ltd.     

Designing superhydrophobic surface based on fluoropolymer–silica nanocomposite via RAFT‐mediated polymerization‐induced self‐assembly

Superhydrophobic surfaces (SHS) find versatile applications as coatings due to their very high water‐repellency, self‐cleaning, and anti‐icing properties. This investigation describes the preparation of a SHS from surfactant‐free hybrid fluoropolymer latex. In this case, reversible addition‐fragmentation chain transfer (RAFT) polymerization was adopted to prepare a copolymer of 4‐vinyl pyridine (4VP) and vinyl triethoxysilane (VTES), where the pyridine units were quaternized to make the copolymer soluble in water. The copolymer was further used as a macro‐RAFT agent to polymerize 2,2,2‐trifluoroethyl methacrylate (TFEMA) in a surfactant‐free emulsion via polymerization‐induced self‐assembly (PISA). The macro‐RAFT agent contained a small amount of VTES as co‐monomer which was utilized to graft silica nanoparticles (SNPs) onto the P(TFEMA) spheres. The film prepared using the nanocomposite latex exhibited a nano‐structured surface as observed by SEM and AFM analyses. Surface modification of the film with fluorinated trichlorosilane produced an SHS with a water contact angle (WCA) of 151.5°. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2018 , 56, 266–275     

Hierarchical structure microspheres of PCL block copolymers via electrospraying as coatings for fabric with mechanical durability and self‐cleaning ability

The various morphology and structure microspheres were fabricated via one‐step single‐solvent electrospraying of hydrophilic and hydrophobic block modified copolymer of polycaprolactone (PCL). A honeycomb‐like hierarchical structure microspheres of PCL‐b‐PTFOA(4h) and abundant nanometer pores of PCL‐b‐PEG400 microspheres were obtained due to the solvent evaporation, thermally and polymer diffusion‐induced phase separation effect. Furthermore, a superhydrophobic coatings and robust superhydrophobic‐coated cotton woven fabric surfaces were prepared by using PCL‐b‐PTFOA(4h) microspheres with hierarchical structure and low surface energy. The contact angle (CA) and sliding angle (SA) of PCL‐b‐PTFOA(4h) microspheres‐coated cotton woven fabric surfaces reached 164.4 ± 5.5° and 6.8 ± 0.5°, respectively, which allows for self‐cleaning. The self‐cleaning test demonstrated that the coated superhydrophobic surface could shed aqueous dyes and dust without any trace. The superhydrophobic‐coated fabric shows good soaping fastness against mechanical abrasion without significant reduction of CA. This electrospraying coating of block copolymers can provide a simple, facile, and promising technique for producing multifunctional textiles.     

Polystyrene‐grafted Al surface with excellent superhydrophobicity and corrosion resistance

A superhydrophobic Al surface was successfully fabricated by a facile and environmentally friendly method as the boiling water treatment and 3‐glycidoxypropyl trimethoxysilane (GPS) as well as carboxyl‐terminated polystyrene (PS‐COOH) modification. The fabrication procedure, morphology, composition, and corrosion resistance of the superhydrophobic Al surface were investigated. Results show that the treatment in the boiling water endows the Al surface with the porous and roughened structure, while the modification with GPS as well as PS‐COOH grafts the long PS chains onto the micro‐scale and nano‐scale hierarchical structure. Consequently, a superhydrophobic Al surface with a contact angle of 153.6° and a rolling angle of 3° is obtained. Additionally, a vast majority of surface area is covered by the air in the solid–liquid contact area for the superhydrophobic Al surface, and which can prevent the corrosive ions entering into the Al surface. As a result, the corrosion resistance is improved greatly. Copyright © 2015 John Wiley & Sons, Ltd.     

Electrochemical Behavior of Dental Ni‐Cr Wirolloy Coated with Eco‐friendly Films in Artificial Saliva

The electrochemical corrosion behavior of the non‐precious Ni‐Cr Wirolloy, being used in dentistry, was investigated before and after applying of two types of eco‐friendly coatings, polyvinyl silsesquioxane (PVS) and nano‐hydroxyapatite (nHAP) separately in artificial saliva solution at 37 °C for 14 d of immersion. The study aimed to investigate the effectiveness of the introduced coating films in enhancing the corrosion resistance of the alloy, and in decreasing the leaching of the toxic Ni ions from the alloy into the environment. The electrochemical corrosion investigation methods used are; open circuit potential (OCP), electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques. The evaluated results revealed that the electrochemically coated alloy with PVS. prepared at cathodic potential showed higher corrosion resistance and more stable film compared to that prepared by conventional dip‐coating method. At the same time, the nHAP electrochemically coated film provided the best anti‐corrosion properties over all examined time intervals. The obtained results were confirmed via surface analysis, which assured the formation of the prepared coatings on the alloy surface. Chemical analysis of the corrosion product/solutions showed that the effect of electrochemically deposited nHAP and PVS. polymer films in suppression of Ni ions leaching is similar and slightly higher than that of the chemically coated PVS. one; however, all of them are efficient in decreasing the leaching of the risky Ni ions into the solution.     

Construction and corrosion behaviors of a bilayer superhydrophobic film on copper substrate

A novel bilayer superhydrophobic film was constructed on Cu substrate by a simple multi‐step process. First, (3‐mercaptopropyl) trimethoxysilane (MPTMS) molecules were self‐assembled onto the pre‐etched Cu surface via covalent bonding followed by hydrolysis and condensation, then 1H, 1H, 2H, 2H‐perfluorodecyltrichlorosilane (PFDTS) were grafted onto the resultant hydroxyl terminated surface via the Si‐O‐Si bonding. The so‐prepared sample was defined as Cu‐MPTMS‐PFDTS. The structure and morphology of the samples were characterized by means of contact angle measurement, X‐ray photoelectron spectroscopy and scanning electron microscopy. The corrosion behaviors of the films were evaluated by Tafel plot and electrochemical impedance spectroscopy on an electrochemical work station. The results indicated that the bilayer superhydrophobic film possessed better corrosion protection as compared with the control samples. The superiority of the corrosion protection was mainly ascribed to the following two aspects: the superhydrophobicity and polysiloxane micro‐structures of the Cu‐MPTMS‐PFDTS. Copyright © 2012 John Wiley & Sons, Ltd.     

Approach to excellent superhydrophobicity and corrosion resistance of carbon-based films by graphene and cobalt synergism

A new series of carbon-based films doped with graphene oxide and cobalt (G-Co/a-C:H films) were successfully prepared on Si substrate via one-step electrochemical deposition of methanol as the carbon source and graphene oxide/cobalt as the dopant. G-Co/a-C:H films were fabricated at various graphene oxide concentration for comparative experiments. It can be found that the graphene oxide and cobalt were well embedded in amorphous carbon matrix to form superhydrophobic G-Co/a-C:H film at the doping GO concentration of 0.007 mg/mL, which was confirmed by transmission electron microscopy (TEM). It was noted that the superhydrophobicity of the resulting surface derives from its rough surface with hierarchical micro-nanostructures and the presence of the low-surface-energy GO components on it. The hierarchical micro-nanostructures are attributed to the corporate joint of GO and cobalt to form the multilevel nanoscale composite interface. Specially, the as-fabricated superhydrophobic G-Co/a-C:H film could exhibit excellent self-cleaning ability and corrosion resistance, revealed by the self-cleaning and corrosion tests.     

Literature review on superhydrophobic self‐cleaning surfaces produced by electrospinning

Self‐cleaning surface is potentially a very useful addition for many commercial products due to economic, aesthetic, and environmental reasons. Super‐hydrophobic self‐cleaning, also called Lotus effect, utilizes right combination of surface chemistry and roughness to force water droplets to form high contact angle on a surface, easily roll off a surface and pick up dirt particles on its way. Electrospinning is a promising technique for creation of superhydrophobic self‐cleaning surfaces owing to a wide set of parameters that allow effectively controlling roughness of resulted webs. This article gives a brief introduction to the theory of super‐hydrophobic self‐cleaning and basic principles of the electrospinning process and reviews the scientific literature where electrospinning was used to create superhydrophobic surfaces. The article reviewed are categorized into several groups and their results are compared in terms of superhydrophobic properties. Several issues with current state of the art and highlights of important areas for future research are discussed in the conclusion. © 2012 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys, 2012     

A facile method for fabrication of superhydrophobic coating on aluminum alloy

A superhydrophobic coating applied in corrosion protection was successfully fabricated on the surface of aluminum alloy by chemical etching and surface modification. The water contact angle on the surface was measured to be 161.2° ± 1.7° with sliding angle smaller than 8°, and the superhydrophobic coating showed a long service life. The surface structure and composition were then characterized by means of SEM and XPS. The electrochemical measurements showed that the superhydrophobic coating significantly improved the corrosion resistance of aluminum alloy. The superhydrophobic phenomenon of the prepared surface was analyzed with Cassie theory, and it was found that only about 6% of the water surface is in contact with the metal substrate and 94% is in contact with the air cushion. Copyright © 2011 John Wiley & Sons, Ltd.     

Superhydrophobic surface fabricated by modifying silica coated multiwalled carbon nanotubes composites

A superhydrophobic surface with maximum static water contact angle of 156° and sliding angle of 3.5° was fabricated by modifying the silica coated multiwalled carbon nanotube composites (SiO₂/MWCNTs) using a silane coupling agent vinyltriethoxysilane. The structures of SiO₂/MWCNTs and superhydrophobic surface were investigated by infrared spectrometer and transmission electron microscopy. The results indicated that silica had been successfully grafted onto MWCNTs and the SiO₂/MWCNTs had been chemical modified by vinyl triethoxy successfully. The morphology of our prepared superhydrophobic surface, investigated by scanning electron microscopy, showed a characteristic rough structure. The effects of pH value and exposure time on the stability of the superhydrophobic surface were also investigated. The superhydrophobic film shows reliable acid and alkali resistance and aging resistance, indicating that it will have a wide range of applications.     

Lotus bioinspired superhydrophobic,self‐cleaning surfaces from hierarchically assembled templates

The super hydrophobic, self‐cleaning properties of natural species derive from the fine hierarchical topography evolved on their surfaces. Hierarchical architectures which are function‐mimetic of the lotus leaf are here described and created from multi‐scale hierarchical assembled templates. The first level of hierarchy was a micromachined dome structure template and the second level of hierarchy was added by layering a thin nanoporous membrane such as porous anodized alumina or an ion track etch membrane. The assembled templates were nanoimprinted by a single step process on thermoplastic films. The wetting angle of the surfaces reached a value of 160° and the self‐cleaning behavior was observed. The superhydrophobic behavior remained over 1 year after fabrication, which demonstrates the stability of these polymeric self‐cleaning topographies. © 2014 Wiley Periodicals, Inc. J. Polym. Sci. Part B. Polym. Phys. 2014 , 52, 603–609     

A novel superhydrophobic surface based on low‐density polyethylene/ethylene‐propylene‐diene terpolymer thermoplastic vulcanizate

A novel superhydrophobic surface based on low‐density polyethylene (LDPE)/ethylene‐propylene‐diene terpolymer (EPDM) thermoplastic vulcanizate (TPV) was successfully fabricated where the etched aluminum foil was used as template. The etched aluminum template, consisted of countless micropores and step‐like textures, was obtained by metallographic sandpaper sanding and the subsequent acid etching. The surface morphology and the hydrophobic properties of the molded TPV surface were researched by using field emission scanning electron microscope and contact angle meter, respectively. From the microstructure observation of the superhydrophobic LDPE/EPDM TPV surface, the step‐like textures obtained via molding with etched aluminum foil template and a large number of fiber‐like structures resulted from the plastic deformation of LDPE matrix could be found obviously. The obtained TPV surface exhibited remarkable superhydrophobicity, with a contact angle of 152.0° ± 0.7° and a sliding angle of 3.1° ± 0.8°.     

Durable ultra‐hydrophobic surfaces for self‐cleaning applications

Self‐cleaning surfaces have received a great deal of attention, both in research studies and commercial applications. Both transparent and non‐transparent self‐cleaning surfaces are highly desirable as they offer many advantages, and their potential applications are endless. The self‐cleaning mechanism can be seen in nature. The Lotus flower, a symbol of purity in Asian cultures, grows in muddy waters, but it stays clean and untouched by dirt, organisms, and pollutants. The Lotus leaf self‐cleaning surface is hydrophobic and rough, showing a multi‐layer morphology of nanoscaled roughness. While hydrophobicity produces a high contact angle, the surface morphology reduces the adhesion of water drops to the surface, which slides easily across the leaf surface carrying the dirt particles with them. Different ultra‐hydrophobic, non‐transparent, and transparent coatings, for potential self‐cleaning applications, were produced on polycarbonate (PC) substrates, using hydrophobic chemistry and different configurations of roughening micro‐ and nano‐particles. However, in most cases, these coatings present low adhesion and durability. The stability and durability of the ultra‐hydrophobic surfaces is of key importance for potential, commercially viable, self‐cleaning applications thus durability and stability enhancement of such coatings was attempted by different methods, evaluated, and eventually improved using a solvent‐bonding technique. Copyright © 2008 John Wiley & Sons, Ltd.     

One‐step immersion method for fabricating superhydrophobic aluminum alloy with excellent corrosion resistance

This work develops a facile one‐step immersion method for preparing the superhydrophobic aluminum alloy, i.e. the aluminum alloy is treated with stearic acid (STA)–ethanol–H₂O solution at 60 °C for 35 h. Results show that the aluminum alloy achieves flower‐like structure with both a great deal of pillars and pores, while the long hydrophobic alkyl chains are chemically grafted onto the hierarchical surface. Meanwhile, the water contact angle at the aluminum alloy surface gradually enhances with the decrease of the ethanol–H₂O volume ratio, and the water contact angle and rolling angle of 156.2° and 5°, respectively, are obtained when the ethanol–H₂O volume ratio is 1:3. Moreover, results show that the higher water contact angle at the aluminum alloy, the better corrosion resistance of the aluminum alloy. Consequently, the aluminum alloy with the superhydrophobic property has the best corrosion resistance, durability, and stability in corrosive environments. Copyright © 2016 John Wiley & Sons, Ltd.     

Fabrication of durable superhydrophobic nanofibrous filters for oil‐water separation using three novel modified nanoparticles (ZnO‐NSPO,AlOO‐NSPO,and TiO2‐NSPO)

Three reusable and durable superhydrophobic nanofibrous filters were prepared by dip coating the nanofibrous fabric in the three different dispersed solutions of the newly modified nanoparticles (ZnO‐NSPO, AlOO‐NSPO, and titanium dioxide [TiO₂]‐NSPO). The contact angle results proved that the TiO₂‐NSPO coated nanofibrous polyacrylonitrile (PAN) filter was hydrophobic with the water contact angle (WCA) of 141° while the ZnO‐NSPO and AlOO‐NSPO coated nanofibrous PAN filters were superhydrophobic with the WCA of 168° and 152°, respectively. The as‐prepared filters can be utilized as an effective martial for oil‐water separation with separation efficiency of over 98%.     

水热法制备铝合金超疏水表面及电化学性能研究

在金属表面构建超疏水膜层是一种有效的防腐技术,本文采用水热处理和自组装技术在铝合金表面构建了超疏水膜层来提升铝合金的耐蚀性能. 通过对不同水热时间下制备的铝合金超疏水表面的电化学性能以及表面形貌进行测试分析,发现当水热反应时间为6 h时,制备的超疏水铝合金超疏水性和电化学性能达到最佳,接触角能达到155.5^o,在模拟海水溶液中保护效率能达到99.6%.     

Super‐Hydrophobic PDMS Surface with Ultra‐Low Adhesive Force

Summary: Rough polydimethylsiloxane (PDMS) surface containing micro‐, submicro‐ and nano‐composite structures was fabricated using a facile one‐step laser etching method. Such surface shows a super‐hydrophobic character with contact angle higher than 160° and sliding angle lower than 5°, i.e. self‐cleaning effect like lotus leaf. The wettabilities of the rough PDMS surfaces can be tunable by simply controlling the size of etched microstructures. The adhesive force between etched PDMS surface and water droplet is evaluated, and the structure effect is deduced by comparing it with those own a single nano‐ or micro‐scale structures. This super‐hydrophobic PDMS surface can be widely applied to many areas such as liquid transportation without loss, and micro‐pump (creating pushing‐force) needless micro‐fluidic devices.

Etched PDMS surface containing micro‐, submicro‐, and nano‐composite structures shows a self‐cleaning effect with water CA as high as 162° and SA lower than 5°.     

Surface characteristics of Ti‐10Ta‐10Nb alloy modified by hydrogen peroxide treatment for dental implants

The use of titanium‐based alloys as biomaterials is becoming more common because they have a reduced elastic modulus, superior biocompatibility, specific strength, good corrosion resistance, superior strain control, and fatigue resistance compared to conventional stainless steel and Co? Cr alloys. However, when implanted into the human body these metals are problematic because they do not directly bond with living bone. Surface treatments play an important role in nucleating calcium phosphate deposition on a surgical titanium alloy implant. The purpose of this study is to examine whether the precipitation of apatite on Ti? 10Ta? 10Nb alloy is affected by surface modification in H₂O₂ solution. Specimens were chemically treated with a solution containing 30 wt% H₂O₂ at 80 °C for 1 h, and subsequently heat treated at 400 °C for 1 h. All specimens were immersed in SBF (Simulated Body Fluid) with a pH of 7.4 at 36.5 °C for seven days, and the surfaces were examined with XRD, SEM, EDX and in vitro testing. The microstructure analysis of the Ti? 10Ta? 10Nb alloy after etching with Keller's etchant showed a Widmanstatten pattern. The micro‐Vickers hardness number was 236.44 ± 4.99, and surface roughness was increased by the surface treatment. The wettability after surface treatment was better than on the nontreated surface. Resistance to cytotoxicity was decreased by the chemical surface treatment (P < 0.05). Copyright © 2011 John Wiley & Sons, Ltd.     

Dynamic (de)wetting properties of superhydrophobic plasma‐treated polyethylene surfaces

Superhydrophobic surfaces present properties of self‐cleaning and unwetting that could be applied in the optics field. The wetting and dewetting of these superhydrophobic surfaces are compared to that of only hydrophobic polyethylene. The contact angle of such a surface varies from 170° to 130–140°. The dewetting is studied using two techniques of dynamic dewetting measurements. The behaviors of surfaces, dried or prewetted with water vapor, are different. The dewetting of the dried surface previously prewetted is discontinuous, and slower than that of the dry one. This specific behavior is interpreted as a roughness effect on trapped water. However, its dewetting is still faster than a corresponding hydrophobic surface like polytetrafluoroethylene (PTFE). Copyright © 2006 John Wiley & Sons, Ltd.