A self-healing superamphiphobic coating for efficient corrosion protection of magnesium alloy

A Multifunctional Coating with Active Corrosion Protection Through a Synergistic pH- and Thermal-Responsive Mechanism

This article aims to develop CeO2 nanocontainer-constructed coating with a synergistic self-healing and protective nature through a simple mechanical blending technique to manage metal corrosion. The proposed coating exhibits excellent corrosion resistance, which is primarily attributed to the combination of thermal-driven healing and active corrosion inhibition. Paraffin wax and 2-polybenzothiazole-loaded CeO2 nanotubes (CeO2-MBT) are directly doped into epoxy coating to perform such a multifunctional role. CeO2 nanocontainers and encapsulated corrosion inhibitor MBT can be released by pH triggers to achieve instant corrosion inhibition upon the surface of metal substrate. In addition, any physical defects in the coating are responsively repaired by heating incorporated paraffin wax to regain structural integrity and consequent barrier function. Corrosion protection efficiency remains sufficient even after ten cycles of damage and healing. Such a multiple-functional coating strategy provides an alternative pathway toward efficient and sustainable performance to tackle corrosion-related challenges of metal components in both short-term and long-term services.

Superhydrophobic Polyaniline-Siloxane Coatings with Excellent Barrier and Active Corrosion Protection Properties for Mild Steel

Although superhydrophobic surfaces have attracted much attention in research, their high cost, poor durability, and challenging manufacturing processes have prevented their widespread application. Here, we describe a simple method of preparing superhydrophobic polyaniline (PANI) pigments and their application in protective coatings. Doping polyaniline pigments with low surface energy perfluorodecanoic acid (PFDA) allowed them to overcome their intrinsic high surface energy, and the resultant PANI-PFDA pigments showed superhydrophobicity. The superhydrophobic PANI-PFDA pigments with different weight percentages were incorporated into a polydimethylsiloxane (PDMS) coating to prepare the superhydrophobic coating. We endeavored to examine the role that hydrophobicity played in enhancing corrosion resistance and looked into the highest concentration of pigment that the coating could withstand. Additionally, studies were carried out on the coating's adherence to the metal and the stability of hydrophobicity at various pH levels. The results showed that PANI-PFDA pigments improved the hydrophobicity and corrosion resistance in the PDMS coating without compromising its robustness and durability. Electrochemical impedance spectroscopy studies revealed that 40 wt % PANI-PFDA content in the PDMS coating provided the best corrosion protection, and this coating could offer active corrosion protection when an artificial defect was made in the coating.

Large-Area Preparation of a Robust Superamphiphobic Coating for Chemical Mechanical Polishing Application

In the chemical-mechanical polishing (CMP) process, the abrasive particles in the polishing slurry tend to agglomerate easily and crystallize on the equipment surfaces during recycling, which can lead to poor wafer processing quality and additional tedious cleaning work. To overcome this issue, a simple and cost-effective self-cleaning surface preparation method has been developed. In this study, elastic and stretchable hydroxyl polydimethylsiloxane (PDMS-OH) was selected as the functional material, it was chelated with pentaerythritol tetra(3-mercapto propionate), and then 2-(perfluorooctyl)ethyl methacrylate was further grafted in situ to the polymer chains via a photoinduced thiol-ene click reaction. Hydrophobically modified micronanoscale silica particles were used to construct robust hierarchical micronanostructures while imparting stable mechanical wear resistance to the coating. The resulting superamphiphobic film exhibits the "lotus effect" and exceptional self-cleaning ability, repelling liquids such as water, hexadecane, and polishing slurry. Furthermore, the coating demonstrated outstanding chemical resistance and antifouling ability. Thus, it provides a feasible solution for preventing abrasive crystallization at critical locations where the polishing slurry flows in the CMP equipment. This work contributes to the enhanced application of superrepellent coatings in the CMP stage of semiconductor material processing.

Ultralong-Term Durable Anticorrosive Coatings by Integration of Double-Layered Transfer Self-Healing Ability, Fe Ion-Responsive Ability, and Active/Passive Functional Partitioning

The application of self-healing polymers in corrosion protection is often limited by their slow and nonautonomous healing ability and poor long-term durability. In this paper, we propose a double-layered transfer self-healing coating constructed by soft and rigid polymer layers. The soft polymer has a fast self-healing rate of 10 min to repair, which was found to accelerate the self-healing of the upper rigid layer. The rigid polymer provided relatively high barrier ability while preserving certain self-healing ability owing to the shear-thinning effect. In this way, the double-layered coating combined rapid self-healing (∼1 h) and high impedance modulus |Z|f-0.01 Hz of 2.58 × 1010 Ω·cm2. Furthermore, the introduction of pyridine groups in B-PEA and polyacrylate-grafted-polydimethylsiloxane (PEA-g-PDMS) induced the Fe ion-responsive ability and shortened the self-healing time to 40 min (100 ppm Fe). Finally, barrier and anode sacrificed layers were introduced to produce multilayered architecture with active/passive anticorrosion performance. In the presence of scratches, the |Z|f-0.01 Hz can be preserved at 1.03 × 1010 Ω·cm2 after 200 days. The created anticorrosive coating technology combines long-term durability with room temperature autonomous rapid self-healing capability, providing a broad prospect for anticorrosive applications.

Impalement-Resistant, Mechanically Stable, and Anti-Static Superamphiphobic Coatings Enabled by Solvent Regulation and Their Application in Anti-Icing

Superamphiphobic coatings have good application prospects in many fields but are limited by their low impalement resistance, weak mechanical stability, and easy adhesion of tiny droplets. Here, impalement-resistant, mechanically stable, and antistatic superamphiphobic coatings were fabricated by spraying a mixture of conductive carbon black (CB), silicone-modified polyester adhesive/fluorinated SiO2 microspheres onto Al alloy. The microspheres were obtained by adhesive phase separation and the binding of fluorinated SiO2 to them. The morphology, superamphiphobicity, impalement resistance, and mechanical stability of the coatings could be regulated by using solvents with different boiling points. As a result, the coatings simultaneously exhibited outstanding mechanical stability, impalement resistance, and superamphiphobicity. The addition of conductive CB endowed the coatings with good antistatic and tiny droplet repellent properties. In addition, the coatings exhibited good anti-icing properties due to the steady air layer at the solid-liquid interface and the very small contact area between them. We suppose that the coatings are very promising for practical application in various fields, including anti-icing, due to their outstanding comprehensive properties and simple preparation process.

Stable food grade wax/attapulgite superhydrophobic coatings for anti-adhesion of liquid foods

Adhesion of liquid foods on their packaging materials has caused significant food wastes and environment pollution, which has attracted great attention. Food grade superhydrophobic coatings are very promising to solve the issue but suffer from low mechanical stability and complex preparation methods. Herein, a food grade superhydrophobic coating for anti-adhesion of liquid foods was prepared by combining edible paraffin wax, polydimethylsiloxane-modified attapulgite natural nanorods and a food grade silicone adhesive. The concentration of polydimethylsiloxane-modified attapulgite, ultrasonication time and the volume ratio of the paraffin wax/attapulgite suspension to the silicone adhesive solution have great influences on wettability and morphology of the coatings. The coatings exhibit good static and dynamic superhydrophobicity due to their hierarchical micro-/nanostructure and low surface energy of the polydimethylsiloxane-modified attapulgite and paraffin wax. Moreover, the coatings exhibit good mechanical and chemical stability. The coatings are also highly repellent towards various liquid foods including the hot ones. Furthermore, the coatings are applicable onto various frequently used flexible and hard food packing materials including polypropylene, polyethylene terephthalate, aluminium alloy and paper, etc. Thus, the superhydrophobic coatings have great application potential in the food packing industry for anti-adhesion of liquid foods.

Preparation of Mechanically Stable Superamphiphobic Coatings via Combining Phase Separation of Adhesive and Fluorinated SiO2 for Anti-Icing

Superamphiphobic coatings have widespread application potential in various fields, e.g., anti-icing, anti-corrosion and self-cleaning, but are seriously limited by poor mechanical stability. Here, mechanically stable superamphiphobic coatings were fabricated by spraying the suspension composed of phase-separated silicone-modified polyester (SPET) adhesive microspheres with fluorinated silica (FD-POS@SiO₂) on them. The effects of non-solvent and SPET adhesive contents on the superamphiphobicity and mechanical stability of the coatings were studied. Due to the phase separation of SPET and the FD-POS@SiO₂ nanoparticles, the coatings present a multi-scale micro-/nanostructure. Combined with the FD-POS@SiO₂ nanoparticles of low surface energy, the coatings present outstanding static and dynamic superamphiphobicity. Meanwhile, the coatings present outstanding mechanical stability due to the adhesion effect of SPET. In addition, the coatings present outstanding chemical and thermal stability. Moreover, the coatings can obviously delay the water freezing time and decrease the icing adhesion strength. We trust that the superamphiphobic coatings have widespread application potential in the anti-icing field.

Durable superhydrophobic coatings for prevention of rain attenuation of 5G/weather radomes

Superhydrophobic coatings are expected to solve the rain attenuation issue of 5G radomes. However, it is very challenging to design and construct such superhydrophobic coatings with good impalement resistance, mechanical robustness, and weather resistance, which remains as one of the main bottlenecks hindering their practical applications. Here, we report the design of superhydrophobic coatings with all these merits mentioned above by spray-coating a suspension of adhesive/fluorinated silica core/shell microspheres onto substrates. The core/shell microspheres are formed by phase separation of the adhesive and adhesion between the adhesive and fluorinated silica nanoparticles. The coatings have an approximately isotropic three-tier hierarchical micro-/micro-/nanostructure, a dense but rough surface at the nanoscale, and chemically inert composition with low surface energy. Consequently, the coatings show excellent impalement resistance, mechanical robustness and weather resistance compared with previous studies, and the mechanisms are revealed. Furthermore, we realize large-scale preparation, extension, and practical application of the coatings for efficiently preventing rain attenuation of 5G/weather radomes. By taking these advantages, we believe that the superhydrophobic coatings have great application potential and market prospect. The findings here will boost preparation and real-world applications of superhydrophobic coatings.

A Review of Smart Superwetting Surfaces Based on Shape-Memory Micro/Nanostructures

Bioinspired smart superwetting surfaces with special wettability have aroused great attention from fundamental research to technological applications including self-cleaning, oil-water separation, anti-icing/corrosion/fogging, drag reduction, cell engineering, liquid manipulation, and so on. However, most of the reported smart superwetting surfaces switch their wettability by reversibly changing surface chemistry rather than surface microstructure. Compared with surface chemistry, the regulation of surface microstructure is more difficult and can bring novel functions to the surfaces. As a kind of stimulus-responsive material, shape-memory polymer (SMP) has become an excellent candidate for preparing smart superwetting surfaces owing to its unique shape transformation property. This review systematically summarizes the recent progress of smart superwetting SMP surfaces including fabrication methods, smart superwetting phenomena, and related application fields. The smart superwettabilities, such as superhydrophobicity/superomniphobicity with tunable adhesion, reversible switching between superhydrophobicity and superhydrophilicity, switchable isotropic/anisotropic wetting, slippery surface with tunable wettability, and underwater superaerophobicity/superoleophobicity with tunable adhesion, can be obtained on SMP micro/nanostructures by regulating the surface morphology. Finally, the challenges and future prospects of smart superwetting SMP surfaces are discussed.

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.

Facile Preparation of Robust Superamphiphobic Coatings on Complex Substrates via Nonsolvent-Induced Phase Separation

Superamphiphobic surfaces have great potential in many fields but often suffer from complicated, expensive, and time-consuming preparation methods, difficulty in applying them on complex substrates, and low stability. Herein, we show a facile fabrication of robust superamphiphobic coatings on complex substrates. A stock suspension was prepared by nonsolvent-induced phase separation of a silicone-modified polyurethane (Si-PU) adhesive containing fluorinated silica (FD-silica) nanoparticles. Then, superamphiphobic surfaces could be easily fabricated via dip coating in the suspension. The influences of phase separation and Si-PU/FD-silica ratio on the wettability and morphology of the coatings were studied. The coatings feature a microscale dense and nanoscale rough texture due to phase separation and rapid solvent evaporation, which enhances the stability by forming strong linkages among the nanoparticles while achieving high superamphiphobicity by trapping air stably in the nanopores. Consequently, the coatings show excellent static/dynamic superamphiphobicity, superior impalement resistance, and good mechanical, chemical, thermal, and UV aging stability. Additionally, the coatings have good anti-icing performance as demonstrated by the greatly extended water freezing time and weakened ice adhesion force in both simulated and real conditions.

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.

Waterborne superamphiphobic coatings with network structure for enhancing mechanical durability

Superamphiphobic coatings may significantly change the wettability of a substrate, and so are attractive for applications in aero/marine engineering, biotechnology, and heat transfer. However, the coatings are caught in a double bind when their durability is considered, as they are vulnerable to mechanical abrasion. Meanwhile, the wide use of organic solvents for preparing the coatings generates environmental pollution. Here, we present a waterborne superamphiphobic coating through one-step spraying that repels a wide range of liquids. By tailoring the repellence of the nano-silica to waterborne resin, a network structure is constructed to protect the embedded nano-silica from damage. Thus, the coatings are durable against 725 cycles of friction tester abrasion under a load of 250 g, showing a significant improvement in the mechanical durability by 3-25 times. Moreover, our coating also shows excellent comprehensive durability, including resistance to oil-flow erosion, falling sand impact, chemical attack, thermal treatment, etc. This strategy can be introduced to various waterborne resins, demonstrating its universality, and may offer a new insight to design sustainable superamphiphobic coatings for long-term practical applications.

A wear-resistant, self-healing and recyclable multifunctional waterborne polyurethane coating with mechanical tunability based on hydrogen bonding and an aromatic disulfide structure

Considering a sustainable society, it is highly desirable to develop coatings that combine excellent wear-resistance, healing and recovery capabilities with tunable mechanical properties.

Preparation and electrochemical inhibition properties of Ce3+-photomodified zinc phosphate materials

Exploration of the strong luminescent properties of cerium-modified zinc phosphate for corrosion protection applications.

In situ growth of corrosion resistant Mg-Fe layered double hydroxide film on Q235 steel

HYPOTHESIS

In situ grown layered double hydroxide (LDH) is commonly used one of the anticorrosion ways for metal materials; Due to the dense growth of LDH on the metal surface, its special layered structure can effectively delay the corrosion rate of metal.

METHODS

In this study, we use a hydrothermal method to successfully grow Mg-Fe LDH film on steel substrates based on self-supplied Fe³⁺ ions. The films were characterized by X-ray diffraction, scanning electron microscopy, and X-ray energy dispersive spectrometry. The potential corrosion resistance of the obtained Mg-Fe LDH film was confirmed using electrochemical impedance spectroscopy and polarization curves.

FINDINGS

After systematic adjustment and parameter optimization, it was found that Mg-Fe LDH film exhibited the best growth morphology and comprehensive performance with an initial pH value of 10, Mg²⁺/urea ratio of 1:4 and reaction time of 12 h. The SEM and electrochemical results further demonstrated that Mg-Fe LDH film play a good protection effect on carbon steel surface. This study provides an important reference for the processing of anticorrosion LDHs film.

Superhydrophobic Coatings with Photothermal Self-Healing Chemical Composition and Microstructure for Efficient Corrosion Protection of Magnesium Alloy

Self-healing superhydrophobic coatings have a wide potential for practical applications by prolonging their lifespan, but still suffer from some shortcomings, for example, difficulty in repairing microstructure damage, limited self-healing cycles, and more importantly the inability to self-heal while in service. Herein, we present the fabrication of superhydrophobic coatings having photothermal self-healing chemical composition and microstructure for the high performance anticorrosion of Mg alloy. The coatings contain a shape-memory polymer (SMP) primer and an upper superhydrophobic coating composed of fluorinated polysiloxane-modified multiwalled carbon nanotubes (PF-POS@MWCNTs). The coatings have good superhydrophobicity, photothermal effect, and anticorrosion performance. The coatings show excellent self-healing performance in response to chemical and microstructure damage, such as rapid self-healing under 1 sun irradiation in 10 min, complete self-healing after serious damage (e.g., 10 damage and self-healing cycles and complex microstructure damage), and even self-healing under natural sunlight in 4 h. Moreover, the self-healed coatings show good corrosion protection for magnesium alloy in the neutral salt spray test. These are because of the combination of the SMP primer with good shape-memory effect and the PF-POS@MWCNTs coating with good superhydrophobicity, photothermal effect, and embedded PF-POS. The coatings are self-healable under natural sunlight while in service and thus may find applications in diverse fields.

Laser machined micropatterns as corrosion protection of both hydrophobic and hydrophilic magnesium

Magnesium and its alloys are promising candidate materials for medical implants because they possess excellent biocompatibility and mechanical properties comparable to bone. Furthermore, secondary surgical operations for removal could be eliminated due to magnesium's biodegradability. However, magnesium's degradation rate in aqueous environments is too high for most applications. It has been reported that hydrophobic textured surfaces can trap a surface gas layer which acts as a protective barrier against corrosion. However, prior studies have not investigated separately the role of the texture and hydrophobic treatments on magnesium corrosion rates. In this study, pillar-shaped microstructure patterns were fabricated on polished high purity magnesium surfaces by ablation with a picosecond laser. Some micropatterned samples were further processed by stearic acid modification (SAM). Micropatterned surfaces with SAM had hydrophobic properties with water droplet contact angles greater than 130°, while the micropatterned surfaces without SAM remained hydrophilic. The corrosion properties of textured and smooth magnesium surfaces in saline solution were investigated using electrochemical impedance spectroscopy (EIS) and optical microscopy. Corrosion rates on both hydrophobic and hydrophilic laser machined surfaces were reduced ∼90% relative to polished surfaces. Surprisingly, corrosion rates were similar for both hydrophobic and hydrophilic surfaces. Indirect evidence of local alkalization near microstructures was found and was hypothesized to stabilize the Mg(OH)₂ layer, thereby inhibiting corrosion on hydrophilic surfaces. This is different than the corrosion resistance mechanism for superhydrophobic surfaces which makes use of gas adhesion at the liquid solid interface. These results suggest additional processing to render the magnesium hydrophobic is not necessary since it does not significantly enhance the corrosion resistance beyond what is conferred by micropatterned textures.

Water-Responsive Self-Repairing Superomniphobic Surfaces via Regeneration of Hierarchical Topography

Superomniphobic surfaces that can self-repair physical damage are desirable for sustainable performance over time in many practical applications that include self-cleaning, corrosion resistance, and protective gears. However, fabricating such self-repairing superomniphobic surfaces has thus far been a challenge because it necessitates the regeneration of both low-surface-energy materials and hierarchical topography. Herein, a water-responsive self-repairing superomniphobic film is reported by utilizing cross-linked hydroxypropyl cellulose (HPC) composited with silica (SiO₂) nanoparticles (HPC-SiO₂) that is treated with a low-surface-energy perfluorosilane. The film can repair physical damage (e.g., a scratch) in approximately 10 s by regenerating its hierarchical topography and low-surface-energy material upon the application of water vapor. The repaired region shows an almost complete recovery of its inherent superomniphobic wettability and mechanical hardness. The repairing process is driven by the reversible hydrogen bond between the hydroxyl (-OH) groups which can be dissociated upon exposure to water vapor. This results in a viscous flow of the HPC-SiO₂ film into the damaged region. A mathematical model composed of viscosity and surface tension of the HPC-SiO₂ film can describe the experimentally measured viscous flow with reasonable accuracy. Finally, we demonstrate that the superomniphobic HPC-SiO₂ film can repair physical damage by a water droplet pinned on a damaged area or by sequential rolling water droplets.

Benzimidazole loaded β-cyclodextrin as a novel anti-corrosion system; coupled experimental/computational assessments

HYPOTHESIS

Silane (sol-gel)-based coatings have been introduced as an eco-friendly system for reducing the metals' corrosion in NaCl solutions. However, due to the lack of active protection property for this type of coatings, their modification is totally recommended for achieving durable protection properties. The present study introduces Beta-cyclodextrin (β-CD) as a novel/effective organic nano-container for Benzimidazole (BM) encapsulation to obtain reliable active protection property via a controlled-release property.

EXPERIMENTS

The chemical structure of the β-CD-BM macromolecule was explored by Fourier-transform infrared spectroscopy (FT-IR), X-Ray diffraction (XRD), and Ultraviolet-visible spectroscopy (UV-Vis). Besides, the Electrochemical Impedance Spectroscopy (EIS) and polarization (potentiodynamic) tests were carried out for investigating the inhibition impacts of the constructed containers. The exposed and unexposed samples' surfaces were analyzed by Field Emission Scanning Electron Microscope (FE-SEM), Energy Dispersive Spectroscopy (EDS)/mapping, and Grazing incidence X-ray diffraction (GIXRD) experiments. Also, the EIS test was conducted over the Silane-based composite film (SCF) for analyzing the anti-corrosion performance of the constructed composites.

FINDINGS

The EIS achievements demonstrated that by the addition of β-CD-BM complexes to the saline solution, the mild steel corrosion was mitigated by about 84%. The EIS results also displayed that the total resistance of the modified composite was enhanced from 5540 Ω.cm² to 10967 Ω.cm² and the intact coating provided a total resistance of 80254 Ω.cm². The dispersion-corrected Density Functional Theory (DFT)-D explorations ascertained the inclusion capacity of benzimidazole inside the β-CD. The Monte Carlo/Molecular Dynamics (MC/MD) calculations strongly affirmed the adsorption of BM and β-CD-BM over the substrate.

A Review of Fabrication Methods, Properties and Applications of Superhydrophobic Metals

Hydrophobicity and superhydrophobicity with self-cleaning properties are well-known characteristics of several natural surfaces, such as the leaves of the sacred lotus plant (Nelumbo nucifera). To achieve a superhydrophobic state, micro- and nanometer scale topography should be realized on a low surface energy material, or a low surface energy coating should be deposited on top of the micro-nano topography if the material is inherently hydrophilic. Tailoring the surface chemistry and topography to control the wetting properties between extreme wetting states enables a palette of functionalities, such as self-cleaning, antifogging, anti-biofouling etc. A variety of surface topographies have been realized in polymers, ceramics, and metals. Metallic surfaces are particularly important in several engineering applications (e.g., naval, aircrafts, buildings, automobile) and their transformation to superhydrophobic can provide additional functionalities, such as corrosion protection, drag reduction, and anti-icing properties. This review paper focuses on the recent advances on superhydrophobic metals and alloys which can be applicable in real life applications and aims to provide an overview of the most promising methods to achieve sustainable superhydrophobicity.

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.

Porosity-induced mechanically robust superhydrophobicity by the sintering and silanization of hydrophilic porous diatomaceous earth

HYPOTHESIS

Because they have self-similar low-surface-energy microstructures throughout the whole material block, fabricating superhydrophobic monoliths has been currently a promising remedy for the mechanical robustness of non-wetting properties. Noticeably, porous materials have microstructured interfaces throughout the complete volume, and silanization can make surfaces low-surface-energy. Therefore, the porous structure and surface silane-treatment can be combined to render hydrophilic inorganics into mechanically durable superhydrophobic monoliths.

EXPERIMENTS

Superhydrophobic diatomaceous earth pellets were produced by thermal-sintering, followed by a silanization process with octyltriethoxysilane. The durability of superhydrophobicity was evaluated by changes in wetting properties, surface morphology, and chemistry after a systematic abrasion sliding test.

FINDINGS

The intrinsic porosity of diatomite facilitated surface silanization throughout the whole sintered pellet, thus producing the water-repelling monolith. The abrasion sliding converted multimodal porosity of the volume to hierarchical roughness of the surface comprised of silanized particles, thereby attaining superhydrophobic properties of high contact angles over 150° and sliding angles below 20°. The tribological properties revealed useful information about the superhydrophobicity duration of the non-wetting monolith against friction. The result enables the application of porous structures in the fabrication of the anti-abrasion superhydrophobic materials even though they are originally hydrophilic.

Self-Healing Abilities of Shape-Memory Epoxy-Contained Polycaprolactone Microspheres Filled with Cerium(III) Nitrate Coated on Aluminum 2024-T3

The shape-memory epoxy (SME) mixed with 10 wt % polycaprolactone (PCL) microspheres containing 5% cerium(III) nitrate (Ce(NO₃)₃) (PCL5Ce) was coated on an aluminum plate 2024-T3 to investigate the self-healing property. The coating was scratched and heated at 80 °C for 30 min to activate the self-healing mechanism and compare with a nonscratched coating. Surface morphology was investigated by scanning electron microscopy. The scratch was completely healed by the PCL5Ce via a thermally assisted self-healing process. Based on electrochemical impedance spectroscopy, the postheated scratched coating had shown impedance values close to the nonscratched coating, which indicated that corrosion resistivity was restored. Ce(NO₃)₃ content at the scratched area was analyzed by focused ion beam-scanning electron microscopy. The scratch width was healed and filled with Ce(NO₃)₃. Therefore, PCL5Ce is capable of being used as an enhancing additive for the self-healing performance in SME coating.

Bionic smart recycled paper endowed with amphiphobic, photochromic, and UV rewritable properties

The single-use of large volumes of paper has become a serious issue which is depleting our resources and damaging the environment. It is of great significance and challenging to adopt simple, reasonable and practical methods to prepare functional recyclable paper. In this article, inspired by pleochromatic creatures and plant leaves' special wettability, a series of photochromic amphiphobic recycled paper (PAR _i ) products was successfully prepared by adding gourd-like modified tungsten trioxide (MTT) to waste paper pulp. The results show that PAR_2-7 has excellent lyophobic performance and amazing photochromic properties. It is worth noting that PAR₇ has an impressive amphiphobic behavior, and its surface water contact angle (WCA) and oil contact angle (OCA) are 146 ± 1° and 137 ± 1°, respectively. It can withstand continuous ultraviolet light irradiation for 60 h, indicating excellent resistance to ultraviolet radiation. Most importantly, the reversible photochromic properties of PAR₇ make it possible to write repeatedly on the surface by using ultraviolet light. In short, the performance of the prepared PAR is stable and superior, which can not only alleviate paper waste, but also means it has great potential in the fields of decoration, packaging, and banknote anti-counterfeiting technology.