One-step electrodeposition process to fabricate corrosion-resistant superhydrophobic surface on magnesium alloy

Acetate-assisted in situ electrodeposited β-MnO2 for the fabrication of nano-architectonics for non-enzymatic glucose detection

Highly sensitive and low-cost electrocatalytic materials are of great importance for the commercial application of non-enzymatic glucose sensors. Herein, we fabricated a novel one-pot enzyme- and indicator-free method for the colorimetric sensing of blood glucose levels based on the direct redox reaction of β-MnO2/glucose. Owing to the introduction of ammonium acetate and the enhanced oxygen evolution reaction, the higher conductive β-MnO2 nanosheets with the larger surface area were directly grown in situ on the conductive substrate by a linear sweep voltammetry (LSV) electrodeposition method. Besides, owing to the unique tunnel-type pyrolusite MnO2, the electrolyte diffusion was facilitated and reduced the response time in the glucose detection process. Hence, the acetate-assisted MnO2 electrode exhibited a high sensitivity of 461.87 μA M-1 cm-2 toward glucose, a wide detection range from 1.0 μM to 1 mM, and a low detection limit of 0.47 μM while the electrode also maintained excellent selectivity and stability. These results clearly indicate that the new strategy we developed has great potential for practical applications.

Anti-Environmental Aging Passive Daytime Radiative Cooling

Passive daytime radiative cooling technology presents a sustainable solution for combating global warming and accompanying extreme weather, with great potential for diverse applications. The key characteristics of this cooling technology are the ability to reflect most sunlight and radiate heat through the atmospheric transparency window. However, the required high solar reflectance is easily affected by environmental aging, rendering the cooling ineffective. In recent years, significant advancements have been made in understanding the failure mechanisms, design strategies, and manufacturing technologies of daytime radiative cooling. Herein, a critical review on anti-environmental aging passive daytime radiative cooling with the goal of advancing their commercial applications is presented. It is first introduced the optical mechanisms and optimization principles of radiative cooling, which serve as a basis for further endowing environmental durability. Then the environmental aging conditions of passive daytime radiative cooling, mainly focusing on UV exposure, thermal aging, surface contamination and chemical corrosion are discussed. Furthermore, the developments of anti-environmental aging passive daytime radiative cooling materials, including design strategies, fabrication techniques, structures, and performances, are reviewed and classified for the first time. Last but not the least, the remaining open challenges and the insights are presented for the further promotion of the commercialization progress.

Robust and flexible polyester fiber membrane with under-liquid dual superlyophobicity for efficient on-demand oil-water separation

Functional materials with under-liquid dual superlyophobicity have generated a great deal of concern from researchers due to their switchable separation ability oil-water mixtures and emulsions. Conceptually, under-liquid dual superlyophobicity is a Cassie state achievable under-liquid through the synergy of an under-liquid double lyophobic surface and the construction of a highly rough surface. However, obtaining an under-liquid dual superlyophobic surface remains difficult due to its thermodynamic contradiction and complex surface composition. Herein, we successfully prepared a functional coating by modifying the mixture of cellulose nanocrystals (CNCs) and nano-TiO2 with perfluorooctanoic acid (PFOA) via a simple method, then obtained a polyester fiber membrane with under-liquid dual superlyophobicity by roll coating method. The surface wettability of the polyester (PET) membrane was altered, transforming it from the original under-water oleophobic/under-oil superhydrophilic state to the under-water superoleophobic/under-oil superhydrophobic state after coated. The resulting membrane was applied to separate oil and water on-demand. The coated PET membrane exhibited high separation efficiency (>99 %) and high separation flux, effectively separating immiscible oil-water systems as well as oil-in-water and water-in-oil emulsions. The coated PET membrane also demonstrated the ability to perform alternate separation of oil-water mixtures through wetting, washing, and rewetting cycles, with repeated processes up to 10 times without significant reduction in separation efficiency. Furthermore, compared with the previous works, our approach offers a simpler and more convenient method for constructing under-liquid dual superlyophobic surface, making it more suitable for continuous corporate production. This study may provide inspiration for the production and application in large-scale of under-liquid dual superlyophobic membranes.

Green synthesis of copper oxide nanoparticles from Murraya koenigii and its corrosion resistivity on Ti-6Al-4V dental alloy

The present work describes green-mediated copper oxide nanoparticles as a potential corrosion inhibitor for the dental alloy Ti-6Al-4V. The salt of copper was reduced to metal nanoparticles using Murraya koenigii leaves, which helps with the agglomeration and nanocluster formation through a reduction mechanism. The current synthesis is a single-step process and is cost-effective. The synthesized nanoparticle was characterized using UV, FTIR, XRD, Zeta potential and Particle size analyzer, SEM, and EDX. The particles were then electrodeposited on Ti-6Al-4V alloy, and the corrosion resistivity in the dental medium was analyzed using Electrochemical parameters such as Corrosion current, Corrosion potential, and anodic and cathodic intercepts through the Tafel and Nyquist plots. The synthesized nanoparticles showed characteristic absorbance at 359 nm. FTIR peaks confirm the phytochemical constituents present in the Murraya koenigii that accounts for the formation of nanoparticles. The XRD predicts the crystalline nature, which is further studied using SEM and EDX. The Zeta potential and Particle size analyzer confirms the negative-negative interactive nature of the synthesized CuO NPs. The NPs showed explicit corrosion inhibition properties with an overall inhibition efficiency of 58.15% and 25.6%, respectively. The study confirms the advantage of using Copper Oxide nanoparticles as a potential coating agent in dental implant alloys in increasing its corrosion efficiency.

Bio-inspired and metal-derived superwetting surfaces: Function, stability and applications

Due to their exceptional anti-icing, anti-corrosion, and anti-drag qualities, biomimetic metal-derived superwetting surfaces, which are widely employed in the aerospace, automotive, electronic, and biomedical industries, have raised significant concern. However, further applications in other domains have been hampered by the poor mechanical and chemical durability of superwetting metallic surfaces, which can result in metal fatigue and corrosion. The potential for anti-corrosion, anti-contamination, anti-icing, oil/water separation, and oil transportation on surfaces with superwettability has increased in recent years due to the advancement of research in biomimetic superwetting interface theory and practice. Recent developments in functionalized biomimetic metal-derived superwetting surfaces were summarized in this paper. Firstly, a detailed presentation of biomimetic metal-derived superwetting surfaces with unique capabilities was made. The problems with the long-term mechanical and chemical stability of biomimetic metal-derived superwetting surfaces were then examined, along with potential solutions. Finally, in an effort to generate fresh concepts for the study of biomimetic metal-derived superwetting surfaces, the applications of superwetting metallic surfaces in various domains were discussed in depth. The future direction of biomimetic metal-derived superwetting surfaces was also addressed.

Recent research advances on corrosion mechanism and protection, and novel coating materials of magnesium alloys: a review

Magnesium alloys have achieved a good balance between biocompatibility and mechanical properties, and have great potential for clinical application, and their performance as implant materials has been continuously improved in recent years. However, a high degradation rate of Mg alloys in a physiological environment remains a major limitation before clinical application. In this review, according to the human body's intake of elements, the current mainstream implanted magnesium alloy system is classified and discussed, and the corrosion mechanism of magnesium alloy in vivo and in vitro is described, including general corrosion, localized corrosion, pitting corrosion, and degradation of body fluid environment impact etc. The introduction of methods to improve the mechanical properties and biocorrosion resistance of magnesium alloys is divided into two parts: the alloying part mainly discusses the strengthening mechanisms of alloying elements, including grain refinement strengthening, solid solution strengthening, dislocation strengthening and precipitation strengthening etc.; the surface modification part introduces the ideas and applications of novel materials with excellent properties such as graphene and biomimetic materials in the development of functional coatings. Finally, the existing problems are summarized, and the future development direction is prospected.

Electrodeposition of Silver Nanoparticles on Indium-Doped Tin Oxide Using Hydrogel Electrolyte for Hydrogen Peroxide Sensing

Nanoparticles are used in various fields, including fuel cells, energy conversion devices, and sensors, because of their large surface area and excellent catalytic properties. Although various methods of synthesizing nanoparticles are available, the most popular is the solution-phase reduction of metal ions. Electrodeposition is a method of reducing metal ions in solution and is widely used because of its various advantages. In this study, Ag nanoparticles with a narrow size distribution were evenly dispersed on the surface of an electrode by applying electrodeposition in an agarose hydrogel medium instead of in solution, confirming the feasibility of Ag deposition in agarose hydrogel, even at a lower reduction potential than that in solution. These results are attributed to the electrolyte effect owing to the hydrophilic backbone of the agarose hydrogel and the gel effect, which reduces unexpected convection. H₂O₂ was detected by using the Ag nanoparticles synthesized in agarose hydrogel, and the limit of detection for H₂O₂ was found to be 4.82 µM, with a dynamic range of 1-500 µM. The nanoparticle synthesis platform proposed in this study is expected to be actively used for the synthesis of other metal/nonmetal nanoparticles.

A hydrophobic layer prepared by cyclic grafting of polydimethylsiloxane on magnesium: improved corrosion resistance and biocompatibility

Magnesium and its alloys have been widely studied as absorbable coronary stent materials. However, the rapid corrosion rate in the intravascular environment inhibits the application of magnesium-based stents. In order to endow magnesium-based stent with appropriate degradation rate and biocompatibility, a hydrophobic layer was constructed by in situ cyclic grafting 4,4'-diphenylmethane diisocyanate and aminopropyl-terminated polydimethylsiloxane on pure magnesium. SEM-EDS, X-ray photoelectron spectroscopy and water contact angle were detected to analyze the chemical composition of the layer. The amino groups were confirmed to be introduced on the surface which provide a platform for subsequent modification. The contact angle value of the modified surface is 132.1°, indicating a hydrophilic surface. The electrochemical measurements and immersion tests demonstrated that the hydrophobic layer significantly improved the anti-corrosion ability of the substrate. Besides, the biocompatibility of the hydrophobic surface was examined by platelet adhesion, cytocompatibility in vitro and subcutaneous implantation in vivo. Immunological and histological results indicated that the hydrophobic layer had excellent biocompatibility. Therefore, the presented study might be a promising method for the surface modification of biomedical magnesium-based stent.

Metal organic frameworks (MOFs) as multifunctional nanoplatform for anticorrosion surfaces and coatings

Corrosion of metallic materials is a long-standing problem in many engineering fields. Various organic coatings have been widely applied in anticorrosion of metallic materials over the past decades. However, the protective performance of many organic coatings is limited due to the undesirable local failure of the coatings caused by micro-pores and cracks in the coating matrix. Recently, metal organic frameworks (MOFs)-based surfaces and coatings (MOFBSCs) have exhibited great potential in constructing protective materials on metallic substrates with efficient and durable anticorrosion performance. The tailorable porous structure, flexible composition, numerous active sites, and controllable release properties of MOFs make them an ideal platform for developing various protective functionalities, such as self-healing property, superhydrophobicity, and physical barrier against corrosion media. MOFs-based anticorrosion surfaces and coatings can be divided into two categories: the composite surfaces/coatings using MOFs-based passive/active nanofillers and the surfaces/coatings using MOFs as functional substrate support. In this work, the state-of-the-art fabrication strategies of the MOFBSCs are systematically reviewed. The anticorrosion mechanisms of MOFBSCs and functions of the MOFs in the coating matrix are discussed accordingly. Additionally, we highlight both traditional and emerging electrochemical techniques for probing protective performances and mechanisms of MOFBSCs. The remaining challenging issues and perspectives are also discussed.

Improving the Processability of a One-Step Hydrophobic Coating for Hot-Dipped Galvanised Steel for Industrial Applications

Hydrophobicity on steel-based metallic surfaces provides an advantage in limiting corrosion and debris buildup on the surface, thereby, improving the substrate performance. An experimental investigation was conducted on the development of zinc stearate and silicon dioxide coatings on the surface of hot-dipped galvanised zinc-coated steel substrates, which could be used to induce superhydrophobicity. Under optimal formulation and processing conditions, a contact angle of 146° could be produced within a 120-min processing window. This represents a reduction in processing time of 67% over previous literature using similar chemistry. In addition, we proved that costly nano silicon dioxide can be replaced by lower cost micro silicon dioxide without decreasing the performance of the coating contact angle. Under standard accelerated exposure tests, the coating was shown to reduce oxide build up by a factor of 3 compared to uncoated galvanized steel.

A Critical Review of Additive Manufacturing Techniques and Associated Biomaterials Used in Bone Tissue Engineering

With the ability to fabricate complex structures while meeting individual needs, additive manufacturing (AM) offers unprecedented opportunities for bone tissue engineering in the biomedical field. However, traditional metal implants have many adverse effects due to their poor integration with host tissues, and therefore new material implants with porous structures are gradually being developed that are suitable for clinical medical applications. From the perspectives of additive manufacturing technology and materials, this article discusses a suitable manufacturing process for ideal materials for biological bone tissue engineering. It begins with a review of the methods and applicable materials in existing additive manufacturing technologies and their applications in biomedicine, introducing the advantages and disadvantages of various AM technologies. The properties of materials including metals and polymers, commonly used AM technologies, recent developments, and their applications in bone tissue engineering are discussed in detail and summarized. In addition, the main challenges for different metallic and polymer materials, such as biodegradability, anisotropy, growth factors to promote the osteogenic capacity, and enhancement of mechanical properties are also introduced. Finally, the development prospects for AM technologies and biomaterials in bone tissue engineering are considered.

Fabrication of Robust Superhydrophobic Nickel Films on Steel Surface With High Corrosion Resistance, Mechanical and Chemical Stability

Superhydrophobic films were successfully grafted on a steel substrate using potentiostatic electrodeposition of nickel followed by treatment with myristic acid (MA) as a low surface energy material. A scanning electron microscope (SEM) was used to investigate the surface topography of the prepared superhydrophobic films. The results revealed that the prepared Ni films modified by myristic acid have micro-nano structures. Fourier transform infrared spectrophotometer (FTIR) and X-ray diffraction (XRD) measurements showed that the steel substrate was coated with nickel film modified with myristic acid. Three different nickel films were prepared: the Ni-MA (I) deposited from pure nickel sulfate bath (1.0 M NiSO4), Ni-MA (II) deposited from pure nickel chloride bath (1.0 M NiCl2. 6H2O), and the third Ni-MA (III) film deposited from Watts bath (0.2 M NiCl2. 6H2O and 0.8M NiSO4). The superhydrophobic Ni-MA (I) film has the highest corrosion resistance, chemical stability, and mechanical abrasion resistance, while Ni-MA (II) film has the lowest properties.

Fabrication of a Tool Electrode with Hydrophobic Features and Its Stray-Corrosion Suppression Performance for Micro-electrochemical Machining

Micro-electrochemical machining (micro-ECM) can machine microstructures with excellent surface integrity on difficult-to-cut alloys. During micro-ECM, stray corrosion results in tapered sidewalls of machined structures. To suppress the stray corrosion, a novel tool electrode with the sidewall insulation of a gas film is proposed by fabricating the metal tool sidewall into a hydrophobic surface. The sidewall surface is designed to be characterized with spherical array cavities (radius of 500 nm) acting as the hydrophobic features, enhancing the gas-shielding effect of the gas film under electrolysis. The fabrication process of the hydrophobic sidewall is described in detail, including the self-assembly procedure of a monolayer template of Φ_1 μm polystyrene microspheres, the copper-electroforming procedure for filling the microspheres' gaps, and the removal procedure for forming spherical array cavities. The fabricated tool electrode (Φ_500 μm) obtains the hydrophobic features of a contact angle of up to 138°. As a result, bubbles generated on the tool surface can form an air-electrolyte interface instead of a dispersed bubble cluster. Micro-ECM experiments of microstructures verify that the novel tool electrode can improve machining accuracy by suppressing sidewall stray corrosion.

A superhydrophobic surface with a synergistic abrasion–corrosion resistance effect prepared by femtosecond laser treatment on an FeMnSiCrNiNb shape memory alloy coating

Superhydrophobic coatings prepared by femtosecond laser treatment have favorable mechanical and chemical stability.

A Durable PVDF/PFOTES-SiO2 Superhydrophobic Coating on AZ31B Mg Alloy with Enhanced Abrasion Resistance Performance and Anti-Corrosion Properties

A simple and practical spray method is employed to prepare a PVDF/PFOTES-SiO2 superhydrophobic composite coating on the AZ31B Mg alloy substrate. The morphology, composition, and water contact angle (CA) were measured by Fourier transform infrared spectroscopy (FTIR), field emission scanning electron microscope (FESEM) and contact angle measuring instrument. Hydrophilic nano-SiO2 is modified by PFOTES to obtain hydrophobicity. The influence of the mass of PFOTES-SiO2 to PVDF on the hydrophobic properties was studied. The wear resistance and stability of the composite coating have been investigated by immersion test, cross-cut adhesion test and friction test. Additionally, the corrosion resistance was measured by electrochemical workstation and salt spray corrosion test. The CA of PVDF/PFOTES-SiO2 coating is 161.3° and the sliding angle (SAs) is less than 2°. After 10× the sandpaper friction test, the superhydrophobic contact angle of the coating remained above 155°, and the sliding angle was less than 5°, which indicated that the prepared coating is a strong superhydrophobic coating with good wear resistance. The results of the electrochemical tests show that the superhydrophobic coating improved the anti-corrosion performance of Mg alloy, and the water contact angle is greater than 150° after 168 h salt spray corrosion test. Due to its excellent superhydrophobicity, wear resistance and anti-corrosion properties, the robust PVDF/PFOTES-SiO2 coating is considered to have great potential for future applications in the automotive and marine industries.

Active Corrosion Protection of Mg–Al Layered Double Hydroxide for Magnesium Alloys: A Short Review

Layered double hydroxides (LDHs) have been successfully applied in surface protection and functionalization of metal materials owing to their special structure, composition, controllability, anion exchange, and other excellent properties. Herein, this review focused on the most common LDH preparation methods on magnesium alloys in the past 10 years by summarizing about 70 research papers. At the same time, based on the corrosion protection mechanism of LDH materials, the performance of LDH films and LDH as filler on metal substrates was briefly introduced. The surface of LDH materials were chemically modified to enhance their compatibility with solvents, and their corrosion resistance function was developed as an additive. Finally, LDH-based composite coatings on Mg alloys by surface pretreatment and chemical modification were discussed.

A Lactoglobulin-Composite Self-Healing Coating for Mg Alloys

Corrosion issue is one of the most crucial bottlenecks for extensive employment of Mg alloys, in particular under harsh engineering conditions. Differing from traditional approaches, a self-healing protective coating composed of lactoglobulin is proposed herein to offer sustainable protection to the underlying Mg parts. Corrosion resistance, evaluated by electrochemical measurements and hydrogen evolution tests, indicates that the lactoglobulin composite film exhibits nobler corrosion potential (-1.28 V_SCE), smaller corrosion current density (8.4 × 10^-6 A/cm²), and lower average corrosion rate (∼0.03 mm/y) than those of its bare counterparts. Moreover, the pre-made cracks in the film were evidently self-healed within 24 h of exposure to corrosive media. The proposed self-healing lactoglobulin composite film provides opportunities to tackle the corrosion challenges of Mg alloys.

Colloidal Lithography for Photovoltaics: An Attractive Route for Light Management

The pursuit of ever-more efficient, reliable, and affordable solar cells has pushed the development of nano/micro-technological solutions capable of boosting photovoltaic (PV) performance without significantly increasing costs. One of the most relevant solutions is based on light management via photonic wavelength-sized structures, as these enable pronounced efficiency improvements by reducing reflection and by trapping the light inside the devices. Furthermore, optimized microstructured coatings allow self-cleaning functionality via effective water repulsion, which reduces the accumulation of dust and particles that cause shading. Nevertheless, when it comes to market deployment, nano/micro-patterning strategies can only find application in the PV industry if their integration does not require high additional costs or delays in high-throughput solar cell manufacturing. As such, colloidal lithography (CL) is considered the preferential structuring method for PV, as it is an inexpensive and highly scalable soft-patterning technique allowing nanoscopic precision over indefinitely large areas. Tuning specific parameters, such as the size of colloids, shape, monodispersity, and final arrangement, CL enables the production of various templates/masks for different purposes and applications. This review intends to compile several recent high-profile works on this subject and how they can influence the future of solar electricity.

In Vivo Blood-Repellent Performance of a Controllable Facile-Generated Superhydrophobic Surface

Fabrication of a blood-repellent surface is essential for implantable or interventional medical devices to avoid thrombosis which can induce several serious complications. In this research, a novel micropatterned surface was fabricated via a facile and cost-effective method, and then, the in vitro and in vivo blood-repellent performances of the controllable superhydrophobic surface were systematically evaluated. First, a facile and cost-effective strategy was proposed to fabricate a controllable superhydrophobic surface on a medically pure titanium substrate using an ultraviolet laser process, ultrasonic acid treatment, and chemical modification. Second, the superhydrophobicity, durability, stability, and corrosion resistance of the superhydrophobic surface were confirmed with advanced testing techniques, which display a high contact angle, low adhesion to water and blood, and excellent resistant element precipitation. Third, the platelet-rich plasma and whole blood were applied to evaluate the hemocompatibility of the superhydrophobic surface by means of an in vitro experiment, and no blood cell activation or aggregation was observed on the superhydrophobic surface. Finally, hollow tubes with an inner superhydrophobic surface were implanted into the left carotid artery of rabbits for 2 weeks to verify the biocompatibility in vivo. The superhydrophobic surface could effectively eliminate blood cell adhesion and thrombosis. No obvious inflammation or inordinate proliferation was found by histological analysis. This research provides a facile and cost-effective strategy to prepare a blood-repellent surface, which may have promising applications in implanted biomedical devices.

Design of a Waste Paper-Derived Chemically 'Reactive' and Durable Functional Material with Tailorable Mechanical Property Following an Ambient and Sustainable Chemical Approach

Controlled tailoring of mechanical property and wettability is important for designing various functional materials. The integration of these characteristics with waste materials is immensely challenging to achieve, however, it can provide sustainable solutions to combat relevant environmental pollutions and other relevant challenges. Here, the strategic conversion of discarded and valueless waste paper into functional products has been introduced following a catalyst-free chemical approach to tailor both the mechanical property and water wettability at ambient conditions for sustainable waste management and controlling the relevant environmental pollution. In the current design, the controlled and appropriate silanization of waste paper allowed to modulate both the a) porosity and b) compressive modulus of the paper-derived sponges. Further, the association of 1,4-conjugate addition reaction between amine and acrylate groups allowed to obtain an unconventional waste paper-derived chemically 'reactive' sponge. The appropriate covalent modification of the residual reactive acrylate groups with selected alkylamines at ambient conditions provided a facile basis to tailor the water wettability from moderate hydrophobicity, adhesive superhydrophobicity to non-adhesive superhydrophobicity. The embedded superhydrophobicity in the waste paper-derived sponge was capable of sustaining large physical deformations, severe physical abrasions, prolonged exposure to harsh aqueous conditions, etc. Further, the waste paper-derived, extremely water-repellent sponges and membranes were successfully extended for proof-of-concept demonstration of a practically relevant outdoor application, where the repetitive remediation of oil spillages has been demonstrated following both selective absorption (25 times) of oils and gravity-driven filtration-based (50 times) separation of oils from oil/water mixtures at different harsh aqueous scenarios.

Surface engineering of cellulose film with myristic acid for high strength, self-cleaning and biodegradable packaging materials

Developing sustainable, renewable, hydrophobic, and biodegradable packaging material to replace petroleum-based plastic products remains a challenge. Herein, original cellulose/myristic acid composite films were fabricated by solvent-vaporized controllable crystallization of natural myristic acid on anisotropic cellulose films. The myristic acid crystals that evenly distributed on the surface of cellulose film generated micronano binary structure and the interstitial space between microplates, resulting in high hydrophobicity (water contact angle = 132°) and excellent self-cleaning property of the composite film. The resultant film exhibited good tensile strength and toughness under both dry (188.7 MPa, 34.4 MJ m^-3) and humid conditions (119.9 MPa, 28.7 MJ m^-3). Moreover, these composite films could be degraded completely after approximately 102 days in soil with an average environment temperature of 32 °C. This work provided a low-cost and sustainable pathway for the fabrication of high-strength, self-cleaning, and waterproof packaging materials instead of plastics.

Fabrication of Superamphiphilic Carbon Using Lignosulfonate for Enhancing Selective Hydrogenation Reactions in Pickering Emulsions

Superamphiphilic materials have great potential to enhance the mass transfer between phases in liquid-liquid catalysis due to their special affinities. Constructing superamphiphilic surfaces that possess superhydrophilic and superhydrophobic properties simultaneously has been a tough assignment. So, exploration of simple methods to prepare such materials using renewable and abundant feedstocks is highly desired. Here, we reported an effective strategy to construct superamphiphilic carbon directly from sodium lignosulfonate, which is a renewable resource from paper industry wastes. From the characterization of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) for superamphiphilic carbon, we found that element C was responsible for the hydrophobic nature and the existence of O and S endowed the carbon with hydrophilic characteristics. Further, micro/nanohierarchical pores were found beneficial for the superamphiphilicity of carbon. Meantime, in the selective hydrogenation of styrene, phenylacetylene, and cis-stilbene in liquid-liquid systems, conversion became double using superamphiphilic carbon compared with blank results, and the yields were three times more than those in blank experiments. The reasons were that superamphiphilic carbon induced the formation of Pickering emulsions and enriched the reactants around catalysts, as concluded by the characterization of confocal laser scanning microscopy and relating contrastive experiments. This work revealed a different route to obtain superamphiphilic carbon and provided a diverse perspective to promote Pickering emulsion catalysis by the superamphiphilicity of carbon.

Adhesion behaviors on four special wettable surfaces: natural sources, mechanisms, fabrications and applications

The study of adhesion behaviors on solid-liquid surfaces plays an important role in scientific research and development in various fields, such as medicine, biology and agriculture. The contact angle and sliding angle of the liquid on the solid surface are commonly used to characterize and measure the wettability of a particular surface. They have a wide range of values, which results in different wettability. It boils down to the adhesion of solid surfaces to liquids. This feature article is aimed at revealing the essence of the adhesion behavior from the aspects of controlling the chemical composition or changing the geometrical microstructure of the surface, and reviewing the natural sources, wetting models, preparation methods and applications of four kinds of typical solid-liquid surfaces (low-adhesion superhydrophobic surfaces, high-adhesion superhydrophobic surfaces, slippery liquid-infused porous surfaces (SLIPS) and hydrophilic/superhydrophilic surfaces). Last, a summary and outlook on this field are given to point out the current challenges and the potential research directions of surface adhesion in the coming future.

Biologically Inspired Scalable-Manufactured Dual-layer Coating with a Hierarchical Micropattern for Highly Efficient Passive Radiative Cooling and Robust Superhydrophobicity

Bioinspired materials for temperature regulation have proven to be promising for passive radiation cooling, and super water repellency is also a main feature of biological evolution. However, the scalable production of artificial passive radiative cooling materials with self-adjusting structures, high-efficiency, strong applicability, and low cost, along with achieving superhydrophobicity simultaneously remains a challenge. Here, a biologically inspired passive radiative cooling dual-layer coating (Bio-PRC) is synthesized by a facile but efficient strategy, after the discovery of long-horned beetles' thermoregulatory behavior with multiscale fluffs, where an adjustable polymer-like layer with a hierarchical micropattern is constructed in various ceramic bottom skeletons, integrating multifunctional components with interlaced "ridge-like" architectures. The Bio-PRC coating reflects above 88% of solar irradiance and demonstrates an infrared emissivity >0.92, which makes the temperature drop by up to 3.6 °C under direct sunlight. Moreover, the hierarchical micro-/nanostructures also endow it with a superhydrophobic surface that has enticing damage resistance, thermal stability, and weatherability. Notably, we demonstrate that the Bio-PRC coatings can be potentially applied in the insulated gate bipolar transistor radiator, for effective temperature conditioning. Meanwhile, the coverage of the dense, super water-repellent top polymer-like layer can prevent the transport of corrosive liquids, ions, and electron transition, illustrating the excellent interdisciplinary applicability of our coatings. This work paves a new way to design next-generation thermal regulation coatings with great potential for applications.

Long-term corrosion protection for magnesium alloy by two-layer self-healing superamphiphobic coatings based on shape memory polymers and attapulgite

Magnesium (Mg) alloy has wide potential applications due to its unique properties, but is apt to corrosion. Recently, superhydrophobic coatings are receiving great interest for corrosion protection of metals but suffer from short lifespan. Here, we report a strategy for long-term corrosion protection of Mg alloy by designing two-layer self-healing superamphiphobic coatings based on shape memory polymers (SMP) and attapulgite. The superamphiphobic coatings are composed of a bottom SMP coating containing a corrosion inhibitor (1, 2, 3-benzotriazole, BTA) and ceresine wax microparticles and a top superamphiphobic attapulgite coating. The two-layer self-healing coatings have excellent superamphiphobicity and initial anti-corrosion performance. The Mg alloy with the coatings can withstand immersion in 3.5 wt% NaCl solution for 80 days and neutral salt spray with 5 wt% NaCl for 54 days. Furthermore, the coatings show excellent self-healing capability towards various physical damages, such as 10 scratching/self-healing cycles at the same position, hexagonal star scratching and grid scratching. Moreover, the physically damaged coatings exhibit self-healing behavior of the microstructure and superhydrophobicity, driven by the shape memory effect of the bottom SMP layer. Thus, the self-healed coatings can still withstand 60 days of 3.5 wt% NaCl solution immersion and 30 days of 5 wt% NaCl salt spray. This study paves the way for applying super anti-wetting coatings for long-term corrosion protection of metals.

Robust superhydrophobicity: mechanisms and strategies

Superhydrophobic surfaces hold great prospects for extremely diverse applications owing to their water repellence property. The essential feature of superhydrophobicity is micro-/nano-scopic roughness to reserve a large portion of air under a liquid drop. However, the vulnerability of the delicate surface textures significantly impedes the practical applications of superhydrophobic surfaces. Robust superhydrophobicity is a must to meet the rigorous industrial requirements and standards for commercial products. In recent years, major advancements have been made in elucidating the mechanisms of wetting transitions, design strategies and fabrication techniques of superhydrophobicity. This review will first introduce the mechanisms of wetting transitions, including the thermodynamic stability of the Cassie state and its breakdown conditions. Then we highlight the development, current status and future prospects of robust superhydrophobicity, including characterization, design strategies and fabrication techniques. In particular, design strategies, which are classified into passive resistance and active regeneration for the first time, are proposed and discussed extensively.

Electrochemical Nucleation and Growth Mechanism of Aluminum on AZ31 Magnesium Alloys

In this study, the nucleation and growth kinetics behavior of aluminum (Al) were investigated in the Choline-chloride (ChCl)-urea deep eutectic solvent (DES) ionic liquids. The studies of cyclic voltammetric and chronoamperometry demonstrated that the electrodeposition process of Al was controlled by three-dimensional progressive nucleation and instantaneous nucleation. And the growth of nuclei is a diffusion-controlled process. The diffusion coefficient of Al ions was calculated at 343 K, that is, 1.773 × 10−10 cm2/s. The Al coating was obtained on the surface of the AZ31 magnesium alloy electrode under appropriate conditions. According to the surface morphology of the Al film, it could be inferred that the theoretical deposit thickness is similar to the actual thickness, and the apparent diffusion rate of Al ions is slower than the diffusion coefficient in the electrolytes. So, in the later deposition, lamellar Al along the diffusion direction were formed, and lamellar depleted Al zones existed around the big grain Al-rich region.

Corrosion resistance of a superhydrophobic dodecyltrimethoxysilane coating on magnesium alloy AZ31 fabricated by one-step electrodeposition

A superhydrophobic and corrosion-resistant coating with a hierarchical macro/nanostructure was constructed by one-step electrodeposition of dodecyltrimethoxysilane (e-DTMS) on Mg alloy AZ31.

Superhydrophobic graphene-based materials with self-cleaning and anticorrosion performance: An appraisal of neoteric advancement and future perspectives

Lotus like materials having superhydrophobicity is attaining greater demand due to the possibility of molding them into different high end applications. The major issue related to self-cleaning superhydrophobic surfaces is their restricted mechanical properties. The development of nanotechnology has brought many advantages in the fabrication and properties of superhydrophobic surfaces and thus it enhanced the demand of superhydrophobic surfaces. Many scientific groups have studied and reported about the superhydrophobicity exhibited by graphene and its analogous derivatives. The fabrication of the devices having properties ranging from anti-sticking and self-cleaning to anti-corrosion and low friction is made possible by the incorporation of this wonderful two-dimensional material. This review focuses on the preparation and properties of graphene based superhydrophobic coating materials with special mention to the wide range of applications rendered by them.

Preparation of Flexible Carbon Fiber Fabrics with Adjustable Surface Wettability for High-Efficiency Electromagnetic Interference Shielding

In the 5G era, for portable electronics to operate at high performance and low power levels, the incorporation of superior electromagnetic interference (EMI) shielding materials within the packages is of critical importance. A desirable wearable EMI shielding material is one that is lightweight, structurally flexible, air-permeable, and able to self-clean. To this end, a bioinspired electroless silver plating strategy and a one-step electrodeposition method are utilized to prepare an EMI shielding fabric (CEF-NF/PDA/Ag/50-30) that possesses these desirable properties. Porous CEF-NF mats with a spatially distributed silver coating create efficient pathways for electron movement and enable a remarkable conductivity of 370 S mm^-1. When tested within a frequency range of 8.2-12.4 GHz, this highly conductive fabric not only achieves an EMI shielding effectiveness (EMI SE of 101.27 dB at 5028 dB cm² g^-1) comparable to a very thin and light metal but also retains the unique properties of fabrics-being light, structurally flexible, and breathable. In addition, it exhibits a high contact angle (CA) of 156.4° with reversible surface wettability. After having been subjected to 1000 cycles of bending, the performance of the fabric only decreases minimally. This strategy potentially provides a novel way to design and manufacture an easily integrated EMI shielding fabric for flexible wearable devices.

Fabrication and Corrosion Resistance of a Superhydrophobic Ni-P/Ni3(NO3)2(OH)4 Multilayer Protective Coating on Magnesium Alloy

A superhydrophobic multilayer coating with excellent corrosion resistance has been fabricated on an AZ61 magnesium alloy through electroless plating and hydrothermal treatment. The surface morphologies, chemical characteristics, wettabilities, and corrosion resistance of the multilayer coating were characterized and discussed. The results show that the electroless Ni-P coating on the magnesium alloy exhibits a nodular structure with micropores and lower corrosion resistance. However, a dense Ni3(NO3)2(OH)4 layer, a porous Ni3(NO3)2(OH)4 nanostructure layer, and a stearic absorbing layer are grown on the surface of the Ni-P coating with superhydrophobic characters and higher corrosion resistance after hydrothermal treatment. Furthermore, the water contact angle and corrosion resistance of the multilayer coating showed a trend of first increasing and then decreasing as the hydrothermal reaction time increases. The optimum hydrothermal reaction time is 15 h, and the multilayer coating prepared under this condition has the highest corrosion resistance and the highest contact angle. In addition, the protection mechanism of the multilayer coating is discussed, and the formation of the dense Ni3(NO3)2(OH)4 layer and the stearic absorbing layer effectively improved the corrosion resistance of the multilayer coating.

Green Fabrication of a Multifunctional Sponge as an Absorbent for Highly Efficient and Ultrafast Oil-Water Separation

Oil leakage results in serious environmental pollution and severe waste of resources, which makes the development of low-cost, environmentally friendly, high-capacity, and durable oil absorbents an urgent task. In this paper, superhydrophobic coatings of activated carbon (AC)-TiO₂-PDMS@PDMS were developed without using any fluorine-containing reagents. The TiO₂ particles were grown on the AC surface to form AC-TiO₂ powders. The hydrophilic AC-TiO₂ powders were further grafted with polydimethylsiloxane (PDMS) molecules (AC-TiO₂-PDMS) to achieve superhydrophobicity through covalent reaction between PDMS and TiO₂ under UV light. The AC-TiO₂-PDMS powder was mixed with a PDMS polymer to form a superhydrophobic coating solution, which made the commercial sponge obtain durable superhydrophobicity. It showed high liquid repellency and antifouling ability toward various liquids and drinks. Taking advantage of the large surface area and high absorption capacity of AC, the coated sponge showed superior high absorption capacity (up to 100-158 g/g) toward various oils and organic solvents with a high absorption speed. Besides, the sponge showed high reusability that could be repeatedly used to absorb various oils and organic solvents. Moreover, the sponge also presented photocatalytic capability, which could repeatedly photodegrade the oil contaminants without influencing the superhydrophobicity, therefore largely increasing the recyclability and lifetime of the sponge. It also could separate immiscible oil-water mixtures with high efficiency and continuously remove oils from water. It was chemically stable and mechanically durable and could resist various harsh conditions without losing its superhydrophobicity. This study developed a facile, cost-effective, and environmentally friendly method to fabricate very promising absorbents for large-scale oil and solvent cleanups and recovery.

Preparation of a Highly Oleophobic Magnesium Alloy AZ31 Surface with Hierarchical Structure and Fluorination

Wettability is an important surface property owing to its useful characteristics such as self-cleaning, antifrosting, and anticorrosion. In particular, an oleophobic surface, which can overcome the limitation of the antifouling performance of a hydrophobic surface, is a considerably valuable research subject. Magnesium alloys are widely used in various industrial fields owing to their superior mechanical performance; however, a technology that is applicable for surface modification has been limited due to their chemical properties. In this study, a new method to prepare a highly oleophobic magnesium alloy AZ31 surface is introduced; this method involves applying a hierarchical structure and fluorination. The hierarchical structure was formed via two-step anodization and magnesium hydroxide formation, and a self-assembled monolayer (SAM) coating method was applied to fluorinate the surface. This hierarchical structure with low surface energy can reduce the contact area between the surface and droplets, thereby decreasing the adhesive force. Contact angles were measured using various test liquids to evaluate the oleophobic surface, and all test liquids, including rapeseed oil (35.0 mN/m), were repelled by the surface.

Effect of Hydrothermal (Sr)-Hydroxyapatite Coatings on the Corrosion Resistance and Mg2+ Ion Release to Enhance Osteoblastic Cell Responses of AZ91D Alloy

The biomedical applications of Mg-based alloys are limited by their rapid corrosion rate in the body fluid. In this study, the hydrothermal synthesis is employed to produce protective bioactive hydroxyapatite coating (HAC) and strontium-substituted hydroxyapatite coating (Sr-HAC) to further enhance the corrosion resistance and in vitro biocompatibility of biodegradable AZ91D Mg alloy in physiological environments. For comparison, the brucite Mg(OH)₂ prepared by the alkaline pre-treatment is designated as a control group. Experimental evidences of XRD and XPS analysis confirm that Sr²⁺ ions can be incorporated into HA crystal structure. It is noted that the hydrothermally synthesized Sr-HAC conversion coating composed of a specific surface topography with the nanoscaled flake-like fine crystallites is constructed on the AZ91D Mg alloy. The hydrophilicity of Mg substrate is effectively enhanced with the decrease in static contact angles after performing alkaline and hydrothermal treatments. Potentiodynamic polarization measurements reveal that the nanostructured Sr-HAC-coated specimens exhibit superior corrosion resistance than HAC and alkaline pre-treated Mg(OH)₂. Moreover, immersion tests demonstrate that Sr-HAC provides favorable long-term stability for the Mg alloy with decreasing concentration of released Mg²⁺ ions in the SBF and the reduced corrosion rate during the immersion length of 30 days. The cells cultured on Sr-HAC specimens exhibit higher viability than those on the alkaline-pre-treated Mg(OH)₂ and HAC specimens. The Sr-substituted HA coating with a nanostructured surface topography can help to stimulate the cell viability of osteoblastic cells.