Research Progress of MXene Composites In Electromagetic Wave Absorption

The issue of electromagnetic wave pollution is increasingly severe due to the rapid advancement of communication technology. Advanced electromagnetic wave absorbing materials have become an important research field. The excellent microwave absorption capabilities of the MXene composite can be attributed to its unique two-dimensional structure, abundant adjustable surfaces with functional groups, significant specific surface area, and high electrical conductivity. In this paper, the electromagnetic properties, electromagnetic wave absorption advantages and electromagnetic wave absorption principles of MXene compared with other materials are reviewed, and the wave absorption properties of MXene/graphene, MXene/carbon nanotubes, MXene/polymer, MXene/metal particles and MXene/oxide composites are summarized and analyzed. It is being investigated what the future holds for MXene and its mixed absorbent materials.


Introduction
The issue of electromagnetic wave pollution has garnered increasing attention due to advancements in electromagnetic communication technology.The primary source of electromagnetic wave pollution arises from the radiation emitted by electronic devices and the interference caused by industrial and medical equipment.This is a major roadblock to creating materials that effectively absorb electromagnetic waves.The MXene blend is a new wave-absorbing material with many great properties, such as being very flexible, easy to control, and reliable.Real-world applications of this information are very important, and it is expected to have a big effect on areas like national safety, communication, and medical care.
A novel metal oxide known as MXene is produced by removing the A layer of a prephase MAX crystal [1] .The substance is commonly referred to as MXene in order to provide a more accurate description of its origin and its structural resemblance to graphene sheets.Various MXene materials exist, such as Ti 3 C 2 T x[2] , Nb 2 CT x [3]   , Ti 2 CT x [4]   , and Ti 4 N 3 T x [5]   .MXene's two-dimensional layered structure, rich functional groups, better hydrophilicity, strong absorption ability and surface activity have led to the application of this material in many fields, such as adsorption [6] , electromagnetic wave absorption [7] , electromagnetic shielding [8] , supercapacitors [11] , gas-sensitive sensors [12] , and so on.
This research study looks at MXene's electromagnetic properties and explains how it absorbs electromagnetic waves.Then, it gives a full summary and analysis of the wave-absorbing properties shown by different MXene-based composites, such as MXene-based/graphene, MXene-based/carbon nanotubes, MXene-based/polymer, MXene-based/metal particles, and MXene/oxide composites, based on how well they absorb waves.

Electromagnetic properties of MXene 2.1 Magnetic property
MXene has certain magnetic properties, which can be manifested as paramagnetism and ferromagnetism, and its application performance in the electromagnetic wave reception area can be effectively improved by regulating these factors.As an illustration, Zhang and colleagues [13] conducted a study whereby they fabricated a monolayer of MXene Ti 3 C 2 T x through the process of LiF/HCl etching, followed by annealing in a hydrogen (H 2 ) environment.The investigation focused on examining the magnetic characteristics of the Ti 3 C 2 T x samples that were both produced and annealed.The experimental findings indicate that the Ti 3 C 2 T x sample exhibits a notably low level of paramagnetic characteristics.Following the process of H 2 annealing, there is a notable increase in the intensity of saturation magnetisation, accompanied by the emergence of ferromagnetism subsequent to annealing at a temperature of 500°C.The principal magnetic sources observed during the process of stripping and H 2 annealing are the Ti-C vacancy pairs, as demonstrated by density-functional theory simulations.

Conductivity
It has been shown that the electrical conductivity of MXene is related to its number of layers, chemical composition, structure, surface modification, etc. MXene with high electrical conductivity is usually composed of transition metals and carbon.The research team led by LiuJi and Valeria Nicolosi [14] has successfully created an ink that incorporates MXene for extrusion printing.This ink enables the fabrication of 3D structures with diverse geometries.Additionally, the team has introduced a freeze-thawing process that converts the printed object into a hydrogel with exceptional conductivity and durability.This hydrogel exhibits excellent shape retention at both macro and micro scales.Additionally, these hydrogels possess favourable mechanical characteristics, including flexibility, elongation, and resistance to fatigue.

Dielectric properties
The dielectric constant of MXene materials typically exhibits a high value, while the dielectric loss angle tangent tends to be low.This characteristic facilitates improved performance in absorbing electromagnetic waves.Several factors influence this behaviour, including the number of MXene layers, the spacing between these layers, the solvent used, and the method employed for preparation.Wu et al. [15] a hydrothermal technique was employed to synthesise a multilayered accordion-like structure of Ti 3 C 2 T x MXene.The paraffin waxes were subjected to testing throughout the frequency range of 2-18 GHz.These waxes consisted of three different compositions: 50% Ti 3 C 2 T x , Ti 3 C 2 T x @MoS 2 , and Ti 3 C 2 T x @Fe 2 O 3 .The dielectric characteristics of paraffins were examined.The impedance matching of Ti 3 C 2 T x @MoS 2 and Ti 3 C 2 T x @Fe 2 O 3 has been shown to be superior to that of pure Ti 3 C 2 T x .
In addition to these properties, MXene materials have excellent mechanical properties [16] with high yield strength and modulus of elasticity, which can be used to prepare high performance composites.The performance of supercapacitors, as indicated by previous research [17] , is greatly enhanced by the layered structure and high MXene surface-to-volume ratio.Consequently, MXene is considered an optimal material for the fabrication of supercapacitors.The material has a significant level of capacitance and demonstrates exceptional stability across repeated cycles.Catalytic qualities are employed in a diverse range of catalytic reactions, both the oxygen reduction process and the hydrogen evolution reaction are two examples of electrocatalytic and chemocatalytic reactions [18] .There are also optical properties, MXene materials have excellent optical properties [19] , such as broadband absorption, optical nonlinearity, etc., which can be used in various fields such as the field of optoelectronics and electromagnetic wave shielding.

Application of Ti 3 C 2 T x in microwave absorption field
Interference of electromagnetic waves by reflecting and dissipating electromagnetic waves when they hit shielding materials, they block electromagnetic waves from entering the shielding area.This is done to block electromagnetic waves but not completely get rid of them, as the reflected electromagnetic waves will cause secondary pollution.Wave-absorbing materials are those that can take in electromagnetic waves.They do this by turning the electromagnetic waves that hit them into heat and other forms of energy.This is why wave-absorbing materials are so important and valued.
The impressive wave-absorption characteristics of wave-absorbing materials are typically attained by the amalgamation of substantial dielectric loss and magnetic loss [20] .Ti 2 CT x can be combined with magnetic nanomaterials to achieve the coexistence of dielectric loss and magnetic loss, which significantly enhances the microwave absorption performance of Ti 2 CT x materials.Li et al. [21] investigated how efficiently composite hybrids of MXene and ferrite absorb microwaves.Magnet grief, losses in dielectric, ohms sadness, multiple reflections, and scattering are the primary mechanisms by which MXene and ferrite composite hybrids absorb microwaves, according to their hypothesis.Main mechanisms.Table 1 lists some materials that are widely used in microwave absorption and shows how their properties compare to those of MXene materials.As can be seen from Table 1, the designability of the structure and properties as well as MXene materials have a distinct advantage in electromagnetic shielding due to their exceptional electromagnetic characteristics.

Basic Principles of MXene Electromagnetic Wave Absorption
When electromagnetic waves propagate, some of the incident electromagnetic waves will propagate towards the interior of the substance when they come into contact with the substance, and some will be refracted by the substance.Inside the wave-absorbing material to achieve multiple refraction, absorption and interference to make the electromagnetic wave generated by the harmful energy into another form of energy, such as heat to be dispersed, in order to achieve the goal of effective attenuation or complete absorption of harmful electromagnetic waves, the other part of the electromagnetic waves can not enter the wave-absorbing material as well as into the wave-absorbing material can not be completely absorbed by the electromagnetic wave, which will be formed at the beginning of the reflective wave or the last through the wave-absorbing material to form a transmissive wave to return to the free space as shown in Figure 1.

Figure 1.MXene electromagnetic wave absorption schematic
So that we can learn more about how waves are absorbed , the concepts of dielectric constant ε and magnetic permeability μ of dielectric materials, both of which are in complex form, are introduced: (2) The equation's real component (ε', μ') signifies the capacity to retain electrical and magnetic energy of electromagnetic waves, whereas the imaginary component (ε", μ") signifies the capacity to disperse physical and magnetic energy of electromagnetic waves.Losses, in their authentic manifestation, are commonly represented by a combination of the tangent of the dielectric damage angle (tanδ ε) and the parallel of the magnet loss slope (tanδ μ) [30] .' / ' ' tan Since tan δ ε > tan δ μ, the electromagnetic wave loses energy mostly through dielectric loss.On the other hand, when tan δ ε < tan δ μ, the wave loses energy mostly through magnetic loss.tanδ ε + tan δ μ describes the complete capacity of electromagnetic wave dissipation.The dissipation can also be obtained from the attenuation constant α .
c is the velocity of light, while f is the frequency of the wave.In the transmission line theory, reflection loss, or R L (in dB) can be used to show how many electromagnetic waves are drawn in [31] .
The material used to absorb waves has a critical value of R L <-10 dB.This means that at least 90% of the electromagnetic field has to be absorbed for it to be considered.

MXene-based composite wave-absorbing materials
So far, MXene has been widely used in carbon nanotubes, polymers, graphene, metals and metal oxides.These materials possess the ability to align with various methods of electromagnetic wave loss, so effectively controlling their impedance matching and augmenting their electromagnetic wave absorption.MXene-based composites have promising applications, such as in wireless communications, radar stealth, electromagnetic wave shielding and electromagnetic wave therapy.The utilisation of MXene composites in the realm of wireless communication has promise for mitigating the adverse effects of electromagnetic wave radiation on human well-being and enhancing communication efficacy.Hence, the investigation of MXene composites in the domain of electromagnetic wave absorption holds significant potential for many applications.

MXene-based/graphene composite wave-absorbing materials
Simultaneously achieving great mirror damage, broad absorb bandwidth, and minimal density is a significant challenge for electromagnetic wave-absorbing devices.Researchers have successfully made carbon-based materials that can absorb a lot of waves.Graphene-based porous materials, on the other hand, are getting more and more attention because of the lower frequent the costs between the interior surfaces of the three-dimensional skeleton, these materials are more effective in absorbing waves.Absorption of electromagnetic waves is another popular application of graphene, a two-dimensional in nature carbon element.
Li et al. [32] made a new kind of ultralight magnetic composite foam material by electrostatically attaching MXene to the surface of a reduced graphene oxide skeleton and then hydrothermally anchoring flower-like FeS clusters.This can speed up the attempt of electromagnetic beams by building a high-impedance structure and, at the same time, changing the amount of MXene loaded and the low-temperature heat treatment to improve the overall impedance d.The results show that the lowest R L value is -47.17 dB in the reduced graphene oxide/MXene/FeS foam that has a very thinly spread out 12.1 mg/cm 3 and a thickness of 4.78 mm.This means that it can effectively absorb frequencies up to 6.15 GHz.More importantly, changing the amount of MXene loaded and treating it with low-temperature heat can be a good way to improve the general impedance distribution and make the composite foam good at absorbing.To get the best general impedance distribution out of the composite foam while keeping its bandwidth and ability to absorb sound well.On this basis Yang et al. [33] MXene reduced graphene oxide composites were made by adding amino-functionalized MXene to reduced graphene oxide in a covalent way.The optimum reflection loss R L at 6.4 GHz is -47.98 dB when the thickness is 2.7 mm. Cai et al. [34] the hydrothermal reaction and freezing and drying approach produced MXene/graphene oxide/Co 3 O 4 nanorods aerogels with excellent wave absorption properties and three-dimensional architectures that prevented impedance mismatch, boosted interfacial polarisation, and minimised multiple scattering.At 9 mg cm -3 , the density achieved an R L of -71.87 dB over a frequency range of 6.88 GHz and a wall thickness of 2.07 mm.. Similarly, magnetic Ti 3 C 2 T x MXene/graphene aerogels [35] .

MXene-based/carbon nanotube composite wave-absorbing materials
Because of their exceptional physical and thermal conductivity, carbon nanotubes have found widespread use in the realm of electromagnetic wave reception.MXene and carbon nanotubes work together to produce a hybrid structure with increased surface area and more channels for conducting electricity.This improves the composite material's ability to soak up electromagnetic radiation.
Cheng et al. [36] the MXene-CoNi@NCNT composites have a lot of different surfaces, a moderate magnetism, and good thermo-oxidative stability.They also have a lot of different defects and nitrogen dopants, as well as a lot of interfaces.With a reflection gain of -55.3 dB and an effective absorption range of 4.3 GHz, they also exhibit excellent equalisation and dampening performance.Hu et al [37] the Lewis acidic molten salt etching method was used to make a green and easy dielectric magnetic MXene-Fe nanocomposite.A bilayer MXene-Fe/CNT/SR composite was then made by casting and curing.With a reflected cost that's -65.9 dB at twelve GHz and a powerful intake range of 8.24 GHz at a thickness of 2.86 mm, it possesses excellent wave-absorbing characteristics.Yue et al. [38] using a vacuum freeze-drying process, they made graphite ring-stacked carbon nanotube composites.To prevent MXene from separating from overheating, they were produced in-situ at extremely low temperatures.They exhibited the lowest reflect loss at -47.28 dB and the broadest efficient absorbing band of 4.16 at 1.36 and 1.16 mm specimen thicknesses.The actual taking in the bandwidth is 4.16 GHz, which has a double-peak characteristic and effectively broadens its absorption bandwidth.

MXene-based/polymer composite wave-absorbing materials
An important group of electromagnetic wave-absorbing materials is made up of polymers mixed with MXene.These materials are used a lot in the military, in communication, in electronics, and in other fields.The polymer can be used as a matrix material and MXene composite, thus forming a composite material with better electrical conductivity, thermal conductivity and mechanical properties, and can be adjusted by adjusting the ratio of the polymer and process parameters to adjust the composite material's parameters such as dielectric constant and magnetic permeability, to achieve a better electromagnetic wave absorption performance.
Lei et al. [39] layered Ti 3 C 2 T x MXene surface with poly pyrrole particles coated hence using in-situ polymerization to increase the composites' electrical conductivity and wave-absorbing capabilities.The MXene/PPy wave-absorbing material has a maximum reflect distortion of -68 dB at 2.68 mm and 10 wt% filler.Additionally, it demonstrates an effective absorption bandwidth of 6.56 GHz.The MXene/PPy composite material exhibits remarkable wave-absorbing capabilities, effectively absorbing waves across the whole Ku-band spectrum.Consequently, it can serve as an effective stealth material, enabling evasion of satellite surveillance and tracking systems.Zhou et al. [40] used crystalline polymer PEO to bridge single Ti 3 C 2 T x MXene nanosheets to construct three-dimensional aerogels, and it was discovered that adding PEO changed the microstructure of it.The combination of MXene and PEO materials had great wave-absorbing and absorptive properties, with an effective absorptive bandwidth of up to 5.20 GHz and a reflection loss value of at least -50.8 dB.These properties make them suitable for future electromagnetic wave adsorbents that need to be strong at absorbing waves and light in weight.

MXene-based/metal particle composite wave-absorbing materials
One more common material that absorbs electromagnetic waves is metal particles.These particles have good electromagnetic wave absorbing qualities, but they are heavy, prone to corrosion, and expensive to prepare.The composite of metal particles with MXene can make up for these shortcomings and improve the comprehensive performance of the composite material.
Wu et al. [41] employed a self-assembly technique to effectively combine magnetic nanoparticles with a dielectric matrix, resulting in a synergistic coupling.MXene/MnO 2 /Ni ternary composites are assembled with MnO 2 nanorods using MXene as a backbone for Ni nanoparticles support, which can generate sufficient interfaces for operational distortion of magnetic wave power, and have at 11.6 GHz.54.4 dB strong reflection loss at 11.6 GHz and an successful absorbing speed of 6.08 GHz, and by modifying the Ni content, the 12 GHz band width of effective absorption can be tuned to the lower frequency range.Liu et al. [42] made Ti 3 C 2 T x /CNFs/TiO 2 /CoNi nanocomposites that are very good at absorbing electromagnetic waves by using an electrostatic self-assembly method and a heat treatment process.MXene gives the nanocomposites a lot of specific surface area and defects, and adding CoNi alloy boosts the synergistic effect of ferromagnetic resonance and eddy current loss, strong dielectric loss, and strong magnetic loss.This can effectively improve the electromagnetic wave absorption performance.Meanwhile, Jin et al. [43] also changed CoNi's mass-to-charge ratio to Ti 3 C 2 T x to use magnetic metal ions.We created CoNi/Ti 3 C 2 T x composites using a solvent-thermal method and gave them a two-dimensional laminar structure.Interfacial polarisation, dipole polarisation, energy sadness, as well as exchange resonance are all factors that contribute to the enhanced radiation absorption made possible by the particle-anchored multilayered structure.M-CN has more than one way of losing energy and is better at absorbing microwaves in the low frequency range.This material is better at absorbing microwaves in the low frequency range than similar materials.

MXene/Oxide Composite Wave Absorbing Materials
A lot of work is also being done on the study of metal oxide and MXene materials in the ingestion of electromagnetic energies.The ways that metal oxide and MXene composites absorb electromagnetic waves are mostly through multiple reflections and scattering, conductive loss, dielectric loss, magnetic loss, and interface polarisation.
Wang et al. [44] synthesised cobalt-based multiphase nanoflowers with varying metal compositions using a hydrothermal method.These nanoflowers were then combined with MXene through the formation of CMOT composites via electrostatic assembly.We conducted an investigation on the dielectric constants of these composites and observed a gradual decrease in values for Fe 2+ , Cu 2+ , and Zn 2+ .Additionally, we found that the composites' wave-suppressing qualities could be finely adjusted, resulting in CFOT-12, CCOT-15, and CZOT-15 exhibiting excellent microwave absorption capabilities.These composites achieved minimum reflection losses of -41.06, -52.67, and -52.52 dB at wavelengths of 2.10, 1.90, and 1.80 mm, respectively.Furthermore, the corresponding effective absorption bandwidths were measured to be 3.6, 4.4, and 3.92 GHz, respectively.Based on the engineering of flaws and heterojunctions, this study opens up new ways to change electromagnetic properties.Offers fresh ideas and suggestions for creating microwave filters that work well and are easy to carry.Wang et al. [45] created MXene composites using Fe 3 O 4 nanoparticles that had been surface-modified in a single step.The surface-modified Fe 3 O 4 nanoparticles in the MXene/Fe 3 O 4 magnetic dampening performance in the 2-40 GHz radio and millimeter-wave ranges was improved using composites.It is also possible to change the MXene and Fe 3 O 4 molar ratio in an accordion-shaped MXene matrix.Changing the absorber thickness and adding magnetic metal oxides yields the smallest reflect gain of -66.25 dB and the largest maximum absorption width of 8.49 GHz.It's an excellent option for future electromagnetic wave-absorbing materials.

Conclusions and outlook
This paper introduces MXene electromagnetic properties, reviews the research progress of microwave absorption in MXene composites in recent years, and then introduces MXene-based wave absorbing materials from several aspects respectively.When comparing with conventional wave-absorbing materials, Similar to graphene, MXene is a recently found multifaceted material having a surface that may be modified with functional groups to provide tunable properties.However, a single MXene often needs to be compounded with other MXene with high conductivity due to good conductivity and poor impedance matching.Currently, MXene wave-absorbing materials are still in the research stage, and MXene composites have broad application prospects, and in order to further improve their performance, future research directions may be carried out in the following aspects: a) Structural design and modulation.By modulating the structure and morphology of MXene composites, their electromagnetic wave absorption properties can be effectively controlled.Future studies can explore how to optimise the dispersion and specific surface area of MXene in composites to improve the wave absorption properties.In addition, the electromagnetic properties of the composites can be further regulated by assembling and constructing composite structures, such as nanowires, nanosheets, and multilayer films.
b)Exploration of new composites.mXene is composited with a variety of materials to form a variety of different composites.Future research could explore new composites and evaluate their electromagnetic wave absorption properties.For example, compositing MXene with organic and inorganic hybrid materials, compositing MXene with biological matrices, and compositing metal-organic framework materials can further improve the wave-absorbing properties of composites.c)Nanoscale and quantisation.Nanosizing and quantisation is an important direction for future research.Preparing MXene into nanoscale composites can improve its specific surface area and dispersion, which can further enhance its electromagnetic wave absorption properties.In addition, MXene nanocomposites have a quantum effect, which allows for finer tuning of electromagnetic wave absorption and reflection.d)Machine learning based material design.The optimisation and design of MXene composites is a complex process that requires consideration of the interaction of multiple parameters and material properties.Artificial intelligence techniques, specifically machine learning, hold promise for the future use of predicting and optimising the wave-absorbing characteristics of MXene composites.By building high-precision models, MXene composites with excellent wave-absorbing properties can be developed more quickly and efficiently.
The optimisation and design of MXene composites is a complex process that requires consideration of the interplay of multiple parameters and material properties.In forthcoming times, the utilisation of artificial intelligence techniques, specifically machine learning, holds promise for the prediction and optimisation of the wave-absorbing characteristics of MXene composites.By building

Table 1 .
Comparison of absorbing performance of MXene and commonly used EMI shielding materials