Recent Advances in MXene/Epoxy Composites: Trends and Prospects

Abstract

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.

Keywords: MXene; MXene/epoxy resin composites; epoxy nanocomposites; epoxy resin; polymer-hybrid composites.

Figure 1

(a) Scheme of the obtention of different MXenes from their MAX phases. Reprinted with permission from Ref. [14]. Copyright 2014 Wiley; (b) Delamination procedure includes HF/HCl treatment to etch Al atoms, intercalation, and delamination by shear and/or sonication. Reprinted with permission from Ref. [15]. Copyright 2012 American Chemical Society; (c) Ti₃AlC₂ after acid treatment (accordion-like); (d) Ti₃C₂T_x MXene sheets thoroughly exfoliated (images from the review authors).

Figure 2

(a) Summary of publications of MXenes and MXenes and epoxy from 2017 to 2021; (b) Summary of MXene/epoxy publications (%) related to hBN/epoxy (grey) and graphene/epoxy (green) publications from 2017 to 2021. Data from 2022 are from January. Results from Web of Science (February 2022).

Figure 3

Overview of the applications of MXenes in epoxy resins.

Figure 4

Diagram of processing methods of MXene/epoxy nanocomposites and related properties of nanocomposites fabricated by the corresponding method.

Figure 5

(a) Scheme of the preparation of Attapulgite (ATP)-MXene hybrids. Reprinted with permission from Ref. [38]. Copyright 2021 MDPI; (b) Tensile strength and elastic modulus for ATP-MXene/ER composites. Reprinted with permission from Ref. [38]. Copyright 2021 MDPI; (c) Scheme of the preparation of SiO₂-decorated, MXene-modified carbon fibers. Reprinted with permission from Ref. [43]. Copyright 2022 Society of Plastic Engineers; (d) Surface morphologies of CF (d1), CF/MXene (d2), and CF/MXene/SiO₂ (d3). Reprinted with permission from Ref. [43]. Copyright 2022 Society of Plastic Engineers; (e) IFSS of the composites and SEM image of fracture surface of CF/MXene/SiO₂ after debonding test. Reprinted with permission from Ref. [43]. Copyright 2022 Society of Plastic Engineers.

Figure 6

(a) Schematic illustrating of fabrication for MXene@PTFE hybrid, preparation process, and friction test of epoxy composite coating. Reproduced with permission from Ref. [67]. Copyright 2021 Elsevier; (b) COF curves and (c) volume wear rates (W) of pure epoxy, PTFE/epoxy, MXene/epoxy, and MXene@PTFE/epoxy composite coatings under humid conditions (RH: ~80%). Reproduced with permission from Ref. [67]. Copyright 2021 Elsevier; (d) Friction coefficient (A) and wear rate (B) of TiO₂/Ti₃C₂/epoxy nanocomposites with different mass frictions under a normal load of 8 N. Reproduced with permission from Ref. [61]. Copyright 2021 MDPI. (e) Model of the interaction between TiO₂/Ti₃C₂ and epoxy matrix in TiO₂/Ti₃C₂/ER nanocomposites. Reproduced with permission from Ref. [61]. Copyright 2021 MDPI.

Figure 7

(a) Schematic diagram of the potential electromagnetic wave absorption mechanisms for the MS/CF/ER composites and SEM image of MX/CF foam at concentration of 5.0 mg/mL of Ti₃C₂Tx MXene. Reprinted with permission from Ref. [71]. Copyright 2021 Elsevier; (b) Schematic illustration of Ti₃C₂Tx MXene/RGO hybrid aerogel structure and EMI-shielding mechanism. Reprinted with permission from Ref. [73]. Copyright 2018 American Chemical Society; (c) STEM images of the TCTA/epoxy resin nanocomposites with 1.38 vol % of T₃C₂Tx. Reprinted with permission from Ref. [75]. Copyright 2020 AAAS; (d) Schematic illustration of possible mechanism of EMI shielding and heat conduction in MXene/AgNWs/ER nanocomposite and SEM image of aerogel with 3 mm thickness. Reprinted with permission from Ref. [56]. Copyright 2022 Elsevier; (e) SEM images and schematic illustration of rGH, rGMH, and rGMH/epoxy nanocomposites. Reprinted with permission from Ref. [76]. Copyright 2020 Elsevier.

Figure 8

(a) Nyquist plots with different immersion times (3 and 30 days) and impedance moduli of neat ER and (GPS)-Ti₃C₂T_X coatings. Common equivalent circuits to fit EIS data. Model A [R_s(Q_cR_c)] is the equivalent electrical circuit appropriate for describing the initial stage of immersion, and as the immersion time increased, the equivalent circuit is described by Model B [R_s(Q_cR_c(Q_dlR^ct), where corrosion gradually penetrates into the epoxy coating, reaching the coating/metal interface. In Model C, the Warburg resistance (R_w) was included because of the tangential diffusion effect due to lamellar nanofiller addition. Reprinted with permission from Ref. [83]. Copyright 2022 Elsevier; (b) Schematic representation of corrosion process of neat epoxy, 0.2 wt % MXene, and 0.2 wt % functionalized MXene coating. Reprinted with permission from Ref. [92]. Copyright 2022 Springer Nature Switzerland; (c) TEM images of ultrathin section (A–E) showing neat ER, unmodified-Ti₃C₂Tx-0.5, and epoxy functionalized-Ti₃C₂T_x, epoxy coatings. Reprinted with permission from Ref. [83]. Copyright 2022 Elsevier.