Amino-functionalized Ti3C2Tx loading ZIF-8 nanocontainer@benzotriazole as multifunctional composite filler towards self-healing epoxy coating

Research on the Corrosion Resistance of Waterborne Epoxy Resin Coating Enhanced by Sodium Alginate-Modified Ti3C2Tx

The enhancement of dispersion stability and interfacial compatibility of nanomaterials within aqueous epoxy matrices represents a pivotal strategy for augmenting the protective performance and corrosion resistance of coatings. In this study, Ti3C2Tx Mxene functionalized with sodium alginate (TSA) was obtained by introducing sodium alginate (SA) into Ti3C2Tx Mxene (T) to improve the corrosion resistance of aqueous epoxy coatings (EP). The dispersion stability of TSA in aqueous medium was quantitatively assessed via ζ-potential measurements, revealing a significant enhancement in stability compared to the reference material T. The long-term stability of TSA/EP composite coatings was systematically evaluated via electrochemical impedance spectroscopy (EIS). Notably, the charge transfer resistance (Rc) remained at 5 × 107 Ω·cm2 after a 60-day accelerated aging test, exhibiting exceptional electrochemical durability. Compared with pure EP coating, this value is improved by 2 orders of magnitude. The improvement is attributed to the fact that active -COOH and -OH groups on the surface of SA enhance the interactions between T nanosheets and EP matrix. Specifically, these functional groups form hydrogen bonds or chemical bonds at the interface. Such interfacial bonding mechanisms enhance the compatibility and interfacial adhesion between T and the EP matrix. These conclusions are further supported by manual scratching experiments. The accessibility and greenness of SA provide a simple and environmentally friendly way of thinking for modifying T.

Surface-Modification Strategy to Produce Highly Anticorrosive Ti3C2Tx MXene-Based Polymer Composite Coatings: A Mini-Review

MXenes are a group of novel two-dimensional (2D) materials with merits such as large specific surface area, abundant surface-functional groups, high chemical activity, excellent mechanical properties, high hydrophilicity, and good compatibility with various polymers. In recent years, many novel high-performance organic anticorrosion coatings using MXenes as nanofillers have been reported and have attracted widespread attention. As the first successfully prepared MXene material, Ti3C2Tx is the most extensively studied and typical member of the MXene family. Therefore, it is taken as the representative of its family, and the status of Ti3C2Tx MXene/epoxy resin (EP) and MXene/waterborne polyurethane (WPU) polymer anticorrosive composite coatings is reviewed. Firstly, the structure, characteristics, and main synthesis methods of MXenes are briefly introduced. Then, the latest progress of four surface-modification strategies to improve the dispersion, compatibility, stability, and anti-aggregation properties of MXenes, namely functionalization grafting, orientation regulation, heterostructure nanocomposite design, and stabilization and greening treatment, are analyzed and summarized. Finally, the current challenges and future opportunities regarding MXene-based corrosion-resistant organic composite coatings are discussed prospectively.

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.

2D materials for Tribo-corrosion and -oxidation protection: A review

The recent rise of 2D materials has extended the opportunities of tuning a variety of properties. Tribo-corrosion, the complex synergy between mechanical wear and chemical corrosion, poses significant challenges across numerous industries where materials are subjected to both tribological stressing and corrosive environments. This intricate interplay often leads to accelerated material degradation and failure. This review critically assesses the current state of utilizing 2D nanomaterials to enhance tribo-corrosion and -oxidation behavior. The paper summarizes the fundamental knowledge about tribo-corrosion and -oxidation mechanisms before assessing the key contributions of 2D materials, including graphene, transition metal chalcogenides, hexagonal boron nitride, MXenes, and black phosphorous, regarding the resulting friction and wear behavior. The protective roles of these nanomaterials against corrosion and oxidation are investigated, highlighting their potential in mitigating material degradation. Furthermore, we delve into the nuanced interplay between mechanical and corrosive factors in the specific application of 2D materials for tribo-corrosion and -oxidation protection. The synthesis of key findings underscores the advancements achieved through integrating 2D nanomaterials. An outlook for future research directions is provided, identifying unexplored avenues, and proposing strategies to propel the field forward. This analysis aims at guiding future investigations and developments at the dynamic intersection of 2D nanomaterials, tribo-corrosion, and -oxidation protection.

2D Nanomaterials Reinforced Organic Coatings for Marine Corrosion Protection: State of the Art, Challenges, and Future Prospectives

2D nanomaterials, with extraordinary physical and chemical characteristics, have long been regarded as promising nanofillers in organic coatings for marine corrosion protection. The past decade has witnessed the high-speed progress of 2D nanomaterial-reinforced organic composite coatings, and plenty of breakthroughs have been achieved as yet. This review covers an in-depth and all-around outline of the up-to-date advances in 2D nanomaterial-modified organic coatings employed for the marine corrosion protection realm. Starting from a brief introduction to 2D nanomaterials, the preparation strategies and properties are illustrated. Subsequently, diverse protection models based on composite coatings for marine corrosion protection are also introduced, including physical barrier, self-healing, as well as cathodic protection, respectively. Furthermore, computational simulations and critical factors on the corrosion protection properties of composite coatings are clarified in detail. Finally, the remaining challenges and prospects for marine corrosion protection based on 2D nanomaterials reinforced organic coatings are highlighted.

Layer-Point Structure of Si3N4-NH2@GO for Improving Corrosion and Wear Resistance of Waterborne Epoxy Coating

The use of graphene-based materials as anticorrosion coatings to protect metals is always a topic of discussion. In this work, silicon nitride (Si3N4) was aminated to improve its water dispersibility. Then it is attached to the graphene oxide (GO) surface to improve compatibility with epoxy (EP) resin as well as conductivity. The results of Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and zeta potentials test analyses indicated that Si3N4-NH2@GO with a layer-point structure has been successfully prepared. The corrosion resistance of the composite coatings was characterized by electrochemical impedance spectroscopy (EIS) and polarization curve analysis, and the wear resistance of the composite coatings was tested by friction and wear tests. The results showed that 1.0% Si3N4-NH2@GO has excellent corrosion and wear resistance. The use of Si3N4-NH2@GO layer point structures in this study broadens the way for GO applications.

In Situ Polymerized Self-Healing Microcapsules as Multifunctional Fillers toward Phosphate Ceramic Coatings

The protective efficacy of chemically bonded phosphate ceramic coatings (CBPC) is notably diminished owing to the presence of micropores and inadequate self-healing capacity in prolonged corrosive environments. Consequently, it is imperative to augment the corrosion and wear resistance of phosphate ceramic coatings while imbuing them with self-healing capabilities. In this work, a novel self-healing phosphate ceramic coating (MC-PTx@CBPC, x = 0.5, 1.0, 1.5) is designed by urea-formaldehyde (UF) in situ polymerization of nanoscale microcapsules encapsulated with 1H,1H,2H,2H-perfluorodecyltriethoxysilane (PFDTES) and evaluated in detail for corrosion and wear resistance. The corrosion inhibition efficiencies of all formulated MC-PTx@CBPC (x = 0.5, 1.0, 1.5) coatings exceed 90%, with the impedance modulus at the lowest frequency (|Z|f=0.01) showing enhancements of 1-2 orders of magnitude compared to pure CBPC. Moreover, the self-healing function becomes active during prolonged immersion. This can be primarily ascribed to the formation of a unique micronanostructure facilitated by nanoscale microcapsules and micrometer-sized alumina ceramics, bonded via the AlPO4 phase. This structure enhances both the hydrophobicity and the bonding strength of the coating. Specifically, following prolonged immersion, the encapsulated PFDTES is liberated from the microcapsules, undergoing hydrolysis and subsequent polymerization upon contact with the electrolyte to form a protective thin film. This film efficiently obstructs the ingress of corrosive agents. Furthermore, the special micronanostructure enhances the hardness of the coating and the releasing PFDTES can form a lubricating film at the interface of abrasion, thus reducing the wear rate and friction coefficient of the MC-PTx@CBPC (x = 0.5, 1.0, 1.5). Therefore, MC-PTx@CBPC (x = 0.5, 1.0, 1.5) possesses excellent corrosion protection, tribological properties, and self-healing capabilities, which provide thought-provoking ideas for phosphate ceramic coatings to protect metals in harsh environments.

Correlations between the anti-corrosion properties and the photocatalytic behavior of epoxy coatings incorporating modified graphene oxide deposited on a zinc substrate

This research aimed to create a substrate-coating system based on zinc and an epoxy resin incorporating modified graphene oxide, which possesses two key characteristics: effective resistance against corrosion and the ability to harness photocatalytic properties. Furthermore, correlations between the anti-corrosion properties and the photocatalytic behaviour of the coatings were made. Thin epoxy (EP) layers embedding 0.1 wt% graphene oxide (GO), reduced graphene oxide (rGO), and modified graphene oxide with (3-aminopropyl)-triethoxysilane (APTES) or poly(amidoamine) (PAMAM) dendrimer were applied on a zinc (Zn) substrate using the dip-coating method. Anti-corrosion properties of coated Zn samples were investigated through electrochemical impedance spectroscopy (EIS) measurements. They showed that the corrosion protection effect is more prominent for EP containing functionalized GO, the highest in the case of GO-PAMAM. The results of the EIS measurements indicated also that the corrosion protection provided by EP-rGO is smaller than that of EP. The photocatalytic properties of the coatings were studied by exposure of the samples to Methylene Blue (MB) solution followed by monitoring the model dye degradation through UV-Vis measurements. To determine the changes in the anti-corrosion properties due to photocatalysis, the coated Zn samples were put through additional EIS measurements. The same coatings applied to a glass substrate lacked photocatalytic properties, indicating that the Zn substrate is accountable for the degradation of MB. Furthermore, the incorporation of GO or functionalized GO into the coating amplifies this effect. From EIS spectra, it was determined that the protective properties loss observed after 3 days is due to coating delamination during exposure to MB solution, the EP-GO-APTES retaining the best adhesion of the coating, 98% remaining on Zn after a cross-hatch test. The corrosion measurements were complemented by examining the morphology and structure of the coatings and the modified GO particles. All things considered, the Zn/EP-GO-APTES system shows the best ability to break down organic pollutants, keeping a good anti-corrosive property and adhesion.

Size-Regulated Metal-Organic Frameworks with Mercaptobenzothiazole for Ga-Based Liquid Metal Encapsulation: A High Performance Oil-Based Additive

In this study, size-regulated MOFs (MZ) with high MBT loading were successfully synthesized by combining mercaptobenzothiazole (MBT), zinc salt, and 2-methylimidazole (2-MI). Subsequently, the MZ structure was utilized to encapsulate tannic acid-modified gallium-based liquid metal (GLM-TA), thereby acquiring a novel heterogeneous nanocomposite (GLM-TA@MZ). The results revealed that the as-prepared GLM-TA@MZ shows good antiwear and friction-reducing performance as an oil-based lubricant additive, the average friction coefficient was decreased to 0.091, and a wear volume was reduced to 0.95 × 104 μm3, which corresponds to a decrease of 52.3 and 97.2% as compared to base oil PAO. The excellent tribological properties of GLM-TA@MZ can be attributed to physical adsorption on the friction pair, followed by tribochemical reactions. As a result, a thick friction protection film (thickness of about 100 nm) containing Ga, Zn, and S elements was formed, which effectively reduced the contact area between the friction pairs, resulting in improved tribological performance. This study provides insights into the design of MOF-based nanocomposites for lubricating applications.

TiO2 Nanocontainers Coconstructed Using Polymers and Corrosion Inhibitors for Anticorrosion Reinforcement of Waterborne Epoxy Coatings

Stimulus-responsive coatings can provide active corrosion protection in response to environmental changes, but they have not reached their anticipated application prospects because of the intricate preparation processes of hollow materials and methods for loading corrosion inhibitors. Herein, polyaniline molybdate corrosion inhibitor and polydopamine-wrapped titanium dioxide nanocontainers (named TiO2/PANI-MoO42-/PDA) are synthesized via a simple three-step electrostatic assembly technique. Introducing TiO2/PANI-MoO42-/PDA nanocontainers in smart waterborne epoxy (WEP) coatings affords the latter with high barriers and long-term corrosion protection. The successful deposition of each layer on the TiO2 nanocontainer surface was validated via Fourier transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, and X-ray photoelectron spectroscopy. Release test results show that the molybdate corrosion inhibitor exhibits notable pH-responsive activity under acidic conditions and slow release in neutral environments, which improves the corrosion resistance of coatings. The addition of synthetic nanocontainers greatly improves the impermeability of WEP coatings. The charge transfer resistance of WEP/TiO2/PANI-MoO42-/PDA coatings is 1.79 × 1011 Ω cm2 after 30 day immersion in a 3.5 wt % NaCl solution, which is 3.32 × 105 times higher than that of WEP coatings. WEP/TiO2/PANI-MoO42-/PDA coatings remain uniform and reliable, even after 50 days of salt spray exposure. The excellent corrosion protection of WEP/TiO2/PANI-MoO42-/PDA coatings is attributed to (1) the enhanced dispersion and compatibility of PDA in the coating for nanocontainers, (2) the combination of phenolic hydroxyl groups of PDA and Fe, which inhibit corrosion activity on the exposed metal surface, and (3) the on-demand release of the MoO42- inhibitor, which provides sustained passivation protection. This work proposes a strategy to simplify the preparation of responsive long-term anticorrosion coatings and extend their service lives.

pH-Responsive Fluorescent Metal-Organic Framework as a Functional Nanofiller for Smart Coatings

A zirconium-based UiO-type UiO-66-(OH)₂ metal-organic framework@carbon dot composite (Zr-MOF@CD) is synthesized through a facile solvent-free thermal method. The Zr-MOF@CD exhibits pH-responsive fluorescence behavior, which emits blue fluorescence for pH < 9 at an emission wavelength of 470 nm. At pH > 9, the fluorescence color turns from blue to yellow, with the emission behavior at 535 nm. Zr-MOF@CDs can serve as functional nanofillers in the epoxy coating for the fabrication of a smart coating, which can realize coating damage warning and metal corrosion reporting. The blue fluorescence can be observed in the area of coating damage with just a minor scratch. Once the scratch is severe enough to expose the metal substrate, the cathodic reaction of oxygen reduction in the corrosion galvanic cell causes an increased pH, where the emission of yellow fluorescence can be identified. The stable fluorescence response is free from the influence of concentration, time, temperature, and the interfering substance. Zr-MOF@CDs can also serve as nanocontainers for loading with the corrosion inhibitor and realizing the repairing of metal corrosion. The development of the smart coating with dual functions of autonomous reporting and repairing holds great potential to improve the lifetime of metals in various industrial applications.

Core-Shell Spheroid Structure TiO2/CdS Composites with Enhanced Photocathodic Protection Performance

In order to improve the conversion and transmission efficiency of the photoelectron, core-shell spheroid structure titanium dioxide/cadmium sulfide (TiO₂/CdS) composites were synthesized as epoxy-based coating fillers using a simple hydrothermal method. The electrochemical performance of photocathodic protection for the epoxy-based composite coating was analyzed by coating it on the Q235 carbon steel surface. The results show that the epoxy-based composite coating possesses a significant photoelectrochemical property with a photocurrent density of 0.0421 A/cm² and corrosion potential of -0.724 V. Importantly, the modified composite coating can extend absorption in the visible region and effectively separate photoelectron hole pairs to improve the photoelectrochemical performance synergistically, because CdS can be regarded as a sensitizer to be introduced into TiO₂ to form a heterojunction system. The mechanism of photocathodic protection is attributed to the potential energy difference between Fermi energy and excitation level, which leads to the system obtaining higher electric field strength at the heterostructure interface, thus driving electrons directly into the surface of Q235 carbon steel (Q235 CS). Moreover, the photocathodic protection mechanism of the epoxy-based composite coating for Q235 CS is investigated in this paper.

Engineering Active-Site-Induced Homogeneous Growth of Polydopamine Nanocontainers on Loading-Enhanced Ultrathin Graphene for Smart Self-Healing Anticorrosion Coatings

Engineering nanocontainers with encapsulated inhibitors onto graphene has been an emerging technology for developing self-healing anticorrosion coatings. However, the loading contents of inhibitors are commonly limited by inhomogeneous nanostructures of graphene platforms. Here, we propose an activation-induced ultrathin graphene platform (UG-BP) with the homogeneous growth of polydopamine (PDA) nanocontainers encapsulated with benzotriazole (BTA). Ultrathin graphene prepared by catalytic exfoliation and etching activation provides an ideal platform with an ultrahigh specific surface area (1646.8 m²/g) and homogeneous active sites for the growth of PDA nanocontainers, which achieves a high loading content of inhibitors (40 wt %). The obtained UG-BP platform exhibits pH-sensitive corrosion inhibition effects due to its charged groups. The epoxy/UG-BP coating possesses integrated properties of enhanced mechanical properties (>94%), efficient pH-sensitive self-healing behaviors (98.5% healing efficiency over 7 days), and excellent anticorrosion performance (4.21 × 10⁹ Ω·cm² over 60 days), which stands out from previous related works. Moreover, the interfacial anticorrosion mechanism of UG-BP is revealed in detail, which can inhibit the oxidation of Fe²⁺ and promote the passivation of corrosion products by a dehydration process. This work provides a universal activation-induced strategy for developing loading-enhanced and tailor-made graphene platforms in extended smart systems and demonstrates a promising smart self-healing coating for advanced anticorrosion applications.

Self-Healing Coating with a Controllable Release of Corrosion Inhibitors by Using Multifunctional Zinc Oxide Quantum Dots as Valves

As an intelligent response system, self-healing anticorrosion materials containing nanocontainers have aroused increasing demands. It is highly expected that the nanocontainers can rapidly respond on corrosion signals to efficiently release corrosion inhibitors, meanwhile to avoid an undesirable leakage before the local corrosion happening. Herein, zinc oxide quantum dot (ZnO-QD)-sealed hollow mesoporous TiO₂ nanocontainers loading with 14.2% benzotriazole (BTA) inhibitor have been successfully prepared [hollow mesoporous titanium dioxide nanospheres (HMTNs)-BTA@ZnO-QDs]. ZnO-QDs play the multifunctional roles on anticorrosion of the self-healing coating. The corrosion tests of coatings on the carbon steel well demonstrate that ZnO-QDs can not only act as a valve to seal and release BTA on the time but also act as a precursor to produce the protective film of Zn(OH)₂ by the reaction of Zn²⁺ ions with OH^- around the cathode region to inhibit the corrosion of carbon steel. After being soaked in 3.5% NaCl solution for 30 days, the |Z|_0.01 Hz value of the coating with HMTNs-BTA@ZnO-QDs still maintains at 2.87 × 10⁷ Ω cm². Once the defects are formed in the coating, the acid-responsive ZnO-QD valves are rapidly decomposed to release BTA inhibitor; meanwhile, the resulted Zn(OH)₂ layer prevent the carbon steel substrate from corrosion in the cathode area. Therefore, it could be promising that the present design of the nanocontainers matching with the multifunctional ZnO-QDs can offer a valuable strategy to construct the self-healing and anticorrosion coatings with a multiresponse to the corrosion environment.

Rising of MXenes: Novel 2D-functionalized nanomaterials as a new milestone in corrosion science - a critical review

Corrosion is a natural process between a metal and its environment that can gradually cause catastrophic damage to the metal equipment, which would have economic implications. Consequently, several protective methods have been utilized to prevent metals from severe degradation. Organic polymeric coatings have been widely used as the most convenient and cost-effective method to boost metals' anti-corrosion properties. Nonetheless, these coatings have a significant amount of solvent, resulting in shrinkage and micro defects in the films during the curing process. Many studies have verified that transition metal carbides/nitrides (MXenes) can form a "labyrinth effect" in the polymeric coatings due to their "nano-barrier effect". Furthermore, based on their sheet-like structures, they can considerably cover the surface defects of the polymeric films. Therefore, the penetration of corrosive elements can be substantially curbed. It is the first review that specifically focused on the new family of 2D nanomaterials, i.e., MXenes, and discussed their applications in corrosion protection systems. The MXenes' pros and cons in the polymeric matrixes as nanofillers will be clarified. Moreover, the synthesis and functionalization methods of the MXenes, their applications, and corrosion protection mechanism will be explored. Subsequently, the MXenes' superiority over other 2D nanomaterials will be highlighted while their future perspectives and industrial applications will be predicted.

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.

Multilayer Coatings for Tribology: A Mini Review

Friction and wear usually lead to huge energy loss and failure of machine pairs, which usually causes great economic losses. Researchers have made great efforts to reduce energy dissipation and enhance durability through advanced lubrication technologies. Single-layer coatings have been applied in many sectors of engineering, but the performance of single-layer coatings still has many limitations. One solution to overcome these limitations is to use a multilayer coating that combines different components with varied physical and chemical properties. In addition, multilayer coating with alternating layers only containing two components can lead to improved performance compared to a coating with only two different layers. This paper systematically reviews the design concept and properties of different types of multilayer coatings, including transition-metal nitride coatings, diamond-like carbon-based coatings, and other multilayer coatings. The inherent functional mechanisms of the multilayer structures are also detailed and discussed.

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.

Recent Advances in MXene/Epoxy Composites: Trends and Prospects

Epoxy resins are thermosets with interesting physicochemical properties for numerous engineering applications, and considerable efforts have been made to improve their performance by adding nanofillers to their formulations. MXenes are one of the most promising functional materials to use as nanofillers. They have attracted great interest due to their high electrical and thermal conductivity, hydrophilicity, high specific surface area and aspect ratio, and chemically active surface, compatible with a wide range of polymers. The use of MXenes as nanofillers in epoxy resins is incipient; nevertheless, the literature indicates a growing interest due to their good chemical compatibility and outstanding properties as composites, which widen the potential applications of epoxy resins. In this review, we report an overview of the recent progress in the development of MXene/epoxy nanocomposites and the contribution of nanofillers to the enhancement of properties. Particularly, their application for protective coatings (i.e., anticorrosive and friction and wear), electromagnetic-interference shielding, and composites is discussed. Finally, a discussion of the challenges in this topic is presented.

Amino-Functionalized MXene Nanosheets Doped with Ce(III) as Potent Nanocontainers toward Self-Healing Epoxy Nanocomposite Coating for Corrosion Protection of Mild Steel

MXene sheets, as new 2D nanomaterials, have been used in many advanced applications due to their superior thin-layered architecture, as well as their capability to be employed as novel nanocontainers for advanced applications. In this research, intercalated Ti₃C₂ MXene sheets were synthesized through an etching method, and then they were modified with 3-aminopropyltriethoxysilane (APTES). Cerium cations (Ce³⁺) as an eco-friendly corrosion inhibitor were encapsulated within Ti₃C₂ MXene sheets to fabricate novel self-healing epoxy nanocomposite coatings. The corrosion protection performance (CPP) of Ce³⁺-doped Ti₃C₂ MXene nanosheets (Ti₃C₂ MXene-Ce³⁺) in a 3.5 wt % sodium chloride (NaCl) solution was studied on bare mild steel substrates using electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. The self-healing CPP of epoxy coatings loaded with 1 wt % undoped and doped Ti₃C₂ MXene was evaluated using EIS, salt spray, and field emission scanning electron microscopy (FE-SEM) techniques. The introduction of Ti₃C₂ MXene-Ce³⁺ into the corrosive solution and artificially scribed epoxy coating enhanced the total impedance from 717 to 6596 Ω cm² and 8876 to 32092 Ω cm², respectively, after 24 h of immersion compared to the control samples.