Co-modification of polydopamine and KH560 on g-C3N4 nanosheets for enhancing the corrosion protection property of waterborne epoxy coating

Tribological Behavior and Mechanism of Silane-Bridged h-BN/MoS2 Hybrid Filling Epoxy Solid Lubricant Coatings

To significantly improve the tribological performance of epoxy resin (EP), a novel h-BN/MoS2 composite was successfully synthesized using spherical MoS2 particles with lamellar self-assembly generated through the calcination method, followed by utilizing the "bridging effect" of a silane coupling agent to achieve a uniform and vertically oriented decoration of hexagonal boron nitride (h-BN) nanosheets on the MoS2 surface. The chemical composition and microstructure of the h-BN/MoS2 composite were systematically investigated. Furthermore, the enhancement effect of composites with various contents on the frictional properties of epoxy coatings was studied, and the mechanism was elucidated. The results demonstrate that the uniform decoration of h-BN enhances the chemical stability of MoS2 in friction tests, and the MoS2 prevents oxidation and maintains its self-lubricating properties. Consequently, due to the protective effect of h-BN and the synergistic interaction between h-BN and MoS2, the 5 wt % h-BN/MoS2 composite exhibited the best friction and wear resistance when incorporated into EP. Compared to pure EP coatings, its average friction coefficient and specific wear rate (0.026 and 1.5 × 10-6 mm3 N-1 m-1, respectively) were significantly reduced. Specifically, the average friction coefficient decreased by 88% and the specific wear rate decreased by 99%, highlighting the superior performance of the h-BN/MoS2-enhanced epoxy composite coating.

Enhancing corrosion resistance and self-healing of water-borne epoxy coatings using Ti3C2Tx-supported tannic acid on UIO-66-NH2

In this study, we developed a composite material comprising UIO-66-NH2 encapsulated tannic acid (TA) loaded on Ti3C2Tx to improve the corrosion resistance of water borne epoxy (WEP) coatings. The successful synthesis of the material was determined by FT-IR, XRD, XPS, EDS, TGA, SEM and TEM characterization. Furthermore, ultraviolet (UV)tests were conducted to evaluate the release rate of TA at varying pH levels, revealing a release rate of approximately 95 % at pH 2. Electrochemical impedance spectroscopy (EIS) results over 60 d indicated that the Rc value of TU-T/WEP remained unchanged at 3.934 × 108, demonstrating a two-order magnitude increase compared to those of pure epoxy coatings, attributed to the synergistic active and passive protection of TU-T materials. The self-healing ability of the TU-T/WEP coating was validated through manual scratch experiments. Additionally, the EIS test showed that the Rc value of TU-T/WEP coating increased to 3.5 × 105 after 72 h, representing a two-order magnitude increase over that of the WEP coating alone. This study introduces a novel approach using green tannic acid as a corrosion inhibitor and amino-functionalized Ti3C2Tx with UIO-66-NH2 to enhance corrosion resistance and self-healing aproperties of coatings.

Advanced materials for smart protective coatings: Unleashing the potential of metal/covalent organic frameworks, 2D nanomaterials and carbonaceous structures

The detrimental impact of corrosion on metallic materials remains a pressing concern across industries. Recently, intelligent anti-corrosive coatings for safeguarding metal infrastructures have garnered significant interest. These coatings are equipped with micro/nano carriers that store corrosion inhibitors and release them when triggered by external stimuli. These advanced coatings have the capability to elevate the electrochemical impedance values of steel by 2-3 orders of magnitude compared to the blank coating. However, achieving intelligent, durable, and reliable anti-corrosive coatings requires careful consideration in the design of these micro/nano carriers. This review paper primarily focuses on investigating the corrosion inhibition mechanism of various nano/micro carriers/barriers and identifying the challenges associated with using them for achieving desired properties in anti-corrosive coatings. Furthermore, the fundamental aspects required for nano/micro carriers, including compatibility with the coating matrix, high specific surface area, stability in different environments, stimuli-responsive behavior, and facile synthesis were investigated. To achieve this aim, we explored the properties of micro/nanocarriers based on oxide nanoparticles, carbonaceous and two-dimensional (2D) nanomaterials. Finally, we reviewed recent literature on the application of state-of the art nanocarriers based on metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs). We believe that the outcomes of this review paper offer valuable insights for researchers in selecting appropriate materials that can effectively enhance the corrosion resistance of coatings.

Carbon Nitride Grafting Modification of Poly(lactic acid) to Maximize UV Protection and Mechanical Properties for Packaging Applications

Due to their biobased nature and biodegradability, poly(lactic acid) (PLA) rich blends are promising for processing in the packaging industry. However, pure PLA is brittle and UV transparent, which limits its application, so the exploration of nanocomposites with improved interfacial interactions and UV absorbing properties is worthwhile. We therefore developed and optimized synthesis routes for well-designed nanocomposites based on a PLA matrix and graphitic carbon nitride (g-C3N4; CN) nanofillers. To enhance the interfacial interaction with the PLA matrix, a silane-coupling agent (γ-methacryloxypropyl trimethoxysilane, KH570) is chemically grafted onto the CN surface after controlled oxidation with nitric acid and hydrogen peroxide. Interestingly, only 1 wt % of CNO-KH570, as synthesized under mild conditions, is needed to significantly improve the UV absorption, blocking even a large part of both UV-C, UV-B, and UV-A outperforming the UV absorption performance of PLA and, for instance, polyethylene terephthalate (PET). The low nanofiller loading of 1 wt % also results in a higher ductility with an increase in elongation at break (+73%), maintaining the tensile modulus. The results on a joint optimization of UV protection and mechanical properties are supported by a broad range of experimental characterizations, including FTIR, XRD, DSC, DSEM, FETEM, XPS, FTIR, TGA, and BET N2 adsorption-desorption analysis.

Vacancy-Modified Porous g-C3N4 Nanosheets Controlled by Physical Activation for Highly Efficient Visible-Light-Driven Hydrogen Evolution and Organics Degradation

As a promising photocatalyst material, g-C3N4 has great application potential in energy production and environmental improvement. In this work, surface-modified g-C3N4 nanosheets with excellent stability and high photocatalytic activity were successfully synthesized by physical steam activation. The charge transfer rate of carbon nitride was improved due to the synergistic effect of nitrogen defect and oxygen doping caused by steam activation. Meanwhile, the specific surface area and pore volume of the optimized sample reached 124.3 m2 g-1 and 0.42 cm3 g-1, respectively, which increased the exposed reaction sites of reactants, enhancing the photocatalytic activity of g-C3N4. In addition, this novel g-C3N4 displayed a great H2 evolution rate of 5889.39 μmol h-1 g-1 with a methylene blue degradation rate up to 6.52 × 10-3 min-1, which was 3.7 and 2.1 times of original g-C3N4, respectively. This study provided a simple and economical method to develop a highly efficient g-C3N4 photocatalyst for solar energy conversion.

HD-SiO2/SiO2 Sol@PDMS Superhydrophobic Coating with Good Durability and Anti-Corrosion for Protection of Al Sheets

Superhydrophobic coatings with excellent water-repellent properties imply a wide range of application areas. However, improvements are needed in terms of stability and complex processing procedures. In the present study, a superhydrophobic coating on Al sheets was prepared by mixing hexadecyltrimethoxysilane (HDTMS)-modified SiO₂ nanoparticles and acid-catalyzed silica sols (HD-SiO₂/SiO₂ Sol) with polydimethylsiloxane (PDMS) binder. The HD-SiO₂ nanoparticles and acid-catalyzed silica sol (SiO₂ sol) form a binary graded micro-nanostructure, providing excellent superhydrophobicity (Water Contact Angle = 158.5°, Sliding angle = 0°). Superhydrophobic coatings with excellent water-repellent properties have potential for corrosion prevention. However the commonly used organic resins have poor chemical and mechanical properties. In the present study, the results of outdoor exposure for 30 days, immersion in acid and alkaline solutions for 24 h, grit abrasion, and water impact experiments, respectively, showed that the prepared superhydrophobic coating has good wear resistance. The integrated superhydrophobic coating on the Al sheets exhibited good corrosion inhibition with an efficiency (η) of 98.9%, which is much higher than that of the uncoated sheets. The present study provides a promising approach for producing stable superhydrophobic coatings at a low cost, with the potential to supplant conventional organic resin anti-corrosion coatings.

Emerging Layered Materials and Their Applications in the Corrosion Protection of Metals and Alloys

Metals and alloys are essential in modern society, and are used in our daily activities. However, they are prone to corrosion, with the conversion of the metal/alloy to its more thermodynamically-favored oxide/hydroxide phase. These undesirable corrosion reactions can lead to the failure of metallic components. Consequently, corrosion-protective technologies are now more important than ever, as it is essential to reduce the waste of valuable resources. In this review, we consider the role of emerging 2D materials and layered materials in the development of a corrosion protection strategy. In particular, we focus on the materials beyond graphene, and consider the role of transition metal dichalcogenides, such as MoS2, MXenes, layered double hydroxides, hexagonal boron nitride and graphitic carbon nitride in the formulation of effective and protective films and coatings. Following a short introduction to the synthesis and exfoliation of the layered materials, their role in corrosion protection is described and discussed. Finally, we discuss the future applications of these 2D materials in corrosion protection.

Enhanced remediation of heavy metals contaminated soils with EK-PRB using β-CD/hydrothermal biochar by waste cotton as reactive barrier

Heavy metals in the soil are major global environmental problems. Waste cotton was used to synthesize a novel β-CD/hydrothermal biochar (KCB), which is a low-cost and environment-friendly adsorbent for heavy metal soil remediation. KCB were used as reactive materials of electrokinetic-permeable reactive barrier (EK-PRB) to explore the removal characteristics of heavy metals. FTIR and XPS analysis revealed that KCB contained large numbers of surface functional groups. Adsorption of KCB for Pb²⁺ and Cd²⁺ reached 50.44 mg g^-1 and 33.77 mg g^-1, respectively. Metal ions in contaminated soil were removed by reactive barrier through electromigration, electrodialysis and electrophoresis, the removal efficiency of Pb²⁺ and Cd²⁺ in soil reached 92.87% and 86.19%. This finding proves that KCB/EK-PRB can be used as a cheap and green process to effectively remediate soils contaminated with heavy metals.

APTES Modification of Molybdenum Disulfide to Improve the Corrosion Resistance of Waterborne Epoxy Coating

MoS2 has been regarded as a promising addition for the preparation of epoxy-based coatings with high anticorrosion ability. However, its dispersion and compatibility remain significant challenges. In the present work, an organic thin layer was well coated on lamellar molybdenum disulfide (MoS2) via a simple modification of 3-aminopropyltriethoxysilane (APTES). The modification of hydrolyzing APTES on lamellar MoS2 effectively improved the dispersity of MoS2 in water-borne epoxy (WEP) and successfully enhanced the compatibility and crosslinking density of MoS2 with WEP. The influence of introducing MoS2-APTES into WEP coating on anticorrosion property for N80 steel was tested by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization and salt spray test. The results exhibited that the |Z|0.01Hz value of MoS2-APTES/WEP still reached 3.647 × 107 Ω·cm2 even after the immersion time of 50 days in 3.5 wt.% NaCl solution, showing an extraordinary performance of corrosion resistance. The enhanced anticorrosion performance of composite coating could be resulted from the apparently increased dispersibility and compatibility of MoS2 in WEP.

Polymer Nanocomposite-based Coatings for Corrosion Protection

Corrosion of metals induces enormous loss of material performance and increase of cost, which has been a common and intractable issue that needs to be addressed urgently. Coating technology has been acknowledged to be the most economic and efficient approach to retard the metal corrosion. For several decades, polymers have been recognized as an effective anticorrosion coating material in both industries and scientific communities, as they demonstrate good barrier properties, ease of altering properties and massive production. Nanomaterials show distinctively different physical and chemical properties compared with their bulk counterparts, which have been considered as highly promising functional materials in various applications, impacting virtually all the fields of science and technologies. Recently, the introduction of nanomaterials with various properties into polymer matrix to form a polymer nanocomposite has been devoted to improve anticorrosive ability of polymer coatings. In this review article, we highlight the recent advances and synopsis of these high-performance polymer nanocomposites as anticorrosive coating materials. We expect that this work could be helpful for the researchers who are interested in the development of functional nanomaterials and advanced corrosion protection technology.

Preparation and Performance of a Waterborne UV/Al Low Infrared Emissivity Coating

An Al powder filler, nano silica slurry and KH560 were mixed with a prepared waterborne UV-curable coating, and the coating was optimized by an orthogonal experiment. Influences of the Al powder concentration on the gloss, infrared emissivity, brightness, mechanical properties, corrosion resistance and other related properties of the coating were further discussed. The results show that the influence of the Al powder concentration on the gloss was more significant, followed by the UV curing time and nano silica slurry concentration. After studying the key role of the concentration of the Al powder, we found that as the concentration of the Al powder is augmented from 10.0% to 25.0%, the gloss lessened from 19.1% to 8.5%. As the concentration of the Al powder was augmented from 10.0% to 40.0%, the infrared emissivity lessened from 0.649 to 0.083 and the brightness L’ value of the coating was step-by-step augmented and inclined to be stable; in addition, the coating’s mechanical properties reached an excellent level. The coating containing 25.0% Al powder had the best corrosion resistance, surface morphology and comprehensive properties, which can potentially be used for infrared stealth technology.

Recent Advances and Trends of Nanofilled/Nanostructured Epoxies

This paper aims at reviewing the works published in the last five years (2016–2020) on polymer nanocomposites based on epoxy resins. The different nanofillers successfully added to epoxies to enhance some of their characteristics, in relation to the nature and the feature of each nanofiller, are illustrated. The organic–inorganic hybrid nanostructured epoxies are also introduced and their strong potential in many applications has been highlighted. The different methods and routes employed for the production of nanofilled/nanostructured epoxies are described. A discussion of the main properties and final performance, which comprise durability, of epoxy nanocomposites, depending on chemical nature, shape, and size of nanoparticles and on their distribution, is presented. It is also shown why an efficient uniform dispersion of the nanofillers in the epoxy matrix, along with strong interfacial interactions with the polymeric network, will guarantee the success of the application for which the nanocomposite is proposed. The mechanisms yielding to the improved properties in comparison to the neat polymer are illustrated. The most important applications in which these new materials can better exploit their uniqueness are finally presented, also evidencing the aspects that limit a wider diffusion.