Design of Ti3C2Tx/TiO2/PANI multi-layer composites for excellent electromagnetic wave absorption performance

Constructing MXene-based mixed-dimensional structure with multiple interfaces to optimize dielectric-magnetic synergistic effect for effective electromagnetic wave absorption

Exploring efficient microwave absorbing materials (MAMs) which could convert electromagnetic (EM) energy into thermal energy represents an approbatory vision to reducing EM radiation and interference. Designing of mixed-dimensional structure with multiple interfaces represents the available target to investigate an ideal MAMs, which maximizes the superiority of mixed-dimensional structure in electromagnetic wave absorption (EMWA). Herein, we take full advantage of multiple interfaces engineering of MXene for optimizing the impedance matching to improve EMWA, MXene-based mixed-dimensional structure was designed by incorporating three-dimensional Fe3C@Carbon layers coated zero-dimensional Fe3O4 nanoparticles (NPs) supported two-dimensional MXene nanosheets (MXene/Fe3O4@Fe3C@Carbon, MFC). The Fe3O4@Fe3C@C with Core@shell structure arrests the essentially self-restacked of MXene and provides various attenuation mechanisms for the incident electromagnetic waves (EMWs). By regulating the carbonization temperature, the MFC exhibits enhanced EMWA property which is attributed to the characteristic structure and optimized dielectric-magnetic synergy effect. The minimum reflection loss (RLmin) value of MFC can reach to -64.3 dB with a matching thickness of 1.73 mm. Otherwise, the maximum effective absorption bandwidth (EAB) (RLmin < -10 dB) reaches 6.42 GHz at only 1.5 mm. Thus, our study refers a novel-fire enlighten to develop excellent mixed-dimensional microwave absorbent based on MXene.

Recent achievements and performance of nanomaterials in microwave absorption and electromagnetic shielding

Due to the swift advancement of the electronic industry and information technology, electromagnetic wave absorption materials are gaining significance in the field of intelligent equipment and weaponry. Nanomaterials were developed to investigate wave absorbing materials that can achieve both impedance matching and attenuation balance. Nanomaterials possess the properties of being thin, lightweight, and capable of absorbing microwave radiation across a wide range of frequencies. This work aims to present a systematic overview of the recent advancements in core-shell materials, specifically carbon, oxide, and sulfide nanomaterials, with regards to their applications in electromagnetic absorption and electromagnetic shielding. This review intends to emphasize the core principles of electromagnetic interference (EMI) shielding and microwave absorption in different systems documented in the literature, along with diverse methods of synthesis and fabrication for creating effective wideband electromagnetic absorbers/shields. Lastly, we also endeavor to offer a comprehensive view and insight into the areas where future research will thrive. This study provides a comprehensive assessment of the current advancements in the field of microwave absorption and electromagnetic shielding of nanomaterials.

High Absorption of Electromagnetic Waves Based on 3D PMMA@Mxene@Co3O4 Composite Microsphere

With the increasing demand for effective electromagnetic wave (EMW) absorbers due to the proliferation of electronic devices and 5G communication systems, traditional wave-absorbing materials can no longer meet the current requirements. Thus, this research introduces a three-dimensional (3D) composite material consisting of PMMA@Mxene@Co₃O₄ microspheres, prepared through in situ self-assembly and hydrothermal growth. The strong electrical conductivity of Mxene, combined with the magnetic loss of Co₃O₄, ensures enhanced dielectric-magnetic synergy, leading to excellent EMW absorption. The study investigates the influence of varying Co₃O₄ content on the electromagnetic properties of the composite. Experimental results show that the optimal sample, with a thickness of 2.5 mm, achieves a minimum reflection loss (RLmin) of -52.88 dB at 6.88 GHz and an effective absorption bandwidth (EAB) of 5.28 GHz. This work highlights the potential of 3D PMMA@Mxene@Co₃O₄ composites as high-performance microwave absorbers, providing a promising solution to EMW pollution. The findings offer valuable insights into material design strategies, demonstrate a promising pathway for developing lightweight, high-performance EMW absorbing materials by optimizing impedance matching and utilizing advanced microstructure design techniques.

Facile constructing Ti3C2Tx/TiO2@C heterostructures for excellent microwave absorption properties

Optimizing and enhancing the performance of electromagnetic wave (EMW) absorption materials relies on the modification of their composition and structure through heterogeneous interface engineering. Ti3C2Tx's high conductivity results in an impedance mismatch, which hinders efficient EMW absorption. Herein, a one-step catalytic chemical vapor deposition (CCVD) method is used to construct the Ti3C2Tx/TiO2@C heterogeneous structure. Upon annealing at 500 °C, amorphous carbon is uniformly deposited on the Ti3C2Tx surface, thereby incorporating the scale-like TiO2 generated during the process. The inclusion of the amorphous carbon layer and TiO2 reduces the substrate's conductivity, achieving optimized impedance matching. Additionally, building heterogeneous interfaces between Ti3C2Tx, TiO2, and C enriches multiple loss mechanisms involving dipole and interfacial polarization, ultimately enabling optimal EMW absorption performance. The minimum reflection loss (RLmin) value of Ti3C2Tx/TiO2@C-500 is -53.12 dB when its thickness and frequency are 1.15 mm and 13.80 GHz, respectively. Moreover, thermal infrared imaging confirms that coatings fabricated using Ti3C2Tx/TiO2@C-500 demonstrate a favorable heat dissipation rate, validating its effectiveness in addressing the challenge of efficient heat dissipation in electronic devices. This study significantly contributes to the progress of two-dimensional (2D) materials, enabling high-performance EMW absorption and expanding their applications in complex scenarios.

Large Microsphere Structure of a Co/C Composite Derived from Co-MOF with Excellent Wideband Electromagnetic Microwave Absorption Performance

In the field of electromagnetic wave (EMW) absorption, carbon matrix materials based on metal-organic frameworks (MOFs) have drawn more interest as a result of their outstanding advantages, such as porous structure, lightweight, controlled morphology, etc. However, how to broaden the effective absorption bandwidth [EAB; reflection loss (RL) ≤ -10 dB] is still a challenge. In this paper, large microsphere structures of a Co/C composite composed of small particle clusters were successfully prepared by the solvothermal method and annealing treatment. At a filling ratio of 40 wt %, the Co/C composite shows attractive microwave absorption (MA) performance after being annealed at 600 °C in an atmosphere of argon. With an EAB of 6.32 GHz (9.92-16.24 GHz) and a thickness of just 2.57 mm, the minimum RL can be attained at -54.55 dB. Most importantly, the EAB can attain 7.12 GHz (10.88-18.0 GHz) when the thickness is 2.38 mm, which is larger than that of the majority of MOF-derived composites. The superior MA performance is strongly related to excellent impedance matching and a higher attenuation constant. This study provides a simple strategy for synthesizing a MOF-derived Co/C composite with a wide EAB.

Preparation of NiS/Ti3C2Tx co-doped with N and P at the covalent interface and its electromagnetic wave absorption properties

The harm of electromagnetic waves on human daily life has gradually received attention, and electromagnetic waves absorption materials have been used to address this issue. MXene, as a new type of 2D material, is a very promising electromagnetic wave absorption material. In this study, NiS nanoparticles were grown on the surface of S terminated Ti3C2Tx, and -S group acted as sulfur sources to construct Ti-S-Ni covalent interface directly in NiS/Ti3C2Tx composites. To further regulate the interface structure and electromagnetic properties, -P and -NH2 groups were also introduced onto the surface of MXene to achieve the N, P co-doping NiS/Ti3C2Tx composites with covalent interface. By investigating the electromagnetic wave absorption performance of the composites, it was found that N and P doping could effectively enhance the electron transfer rate at the interface and optimize the conduction loss, resulting in a significant improvement in performance. The minimum reflection loss was -50.6 dB at a frequency of 15.6 GHz, and the matching thickness was only 1.14 mm with an effective absorption bandwidth of 3.6 GHz. These results provide an important references and guidance for further research and development of high-performance electromagnetic wave absorption materials.

Functional Tailoring of Multi-Dimensional Pure MXene Nanostructures for Significantly Accelerated Electromagnetic Wave Absorption

Transition metal carbide (Ti3 C2 Tx MXene), with a large specific surface area and abundant surface functional groups, is a promising candidate in the family of electromagnetic wave (EMW) absorption. However, the high conductivity of MXene limits its EMW absorption ability, so it remains a challenge to obtain outstanding EMW attenuation ability in pure MXene. Herein, by integrating HF etching, KOH shearing, and high-temperature molten salt strategies, layered MXene (L-MXene), network-like MXene nanoribbons (N-MXene NRs), porous MXene monolayer (P-MXene ML), and porous MXene layer (P-MXene L) are rationally constructed with favorable microstructures and surface states for EMW absorption. HF, KOH, and KCl/LiCl are used to functionalize MXene to tune its microstructure and surface state (F- , OH- , and Cl- terminals), thereby improving the EMW absorption capacity of MXene-based nanostructures. Impressively, with the unique structure, proper electrical conductivity, large specific surface area, and abundant porous defects, MXene-based nanostructures achieve good impedance matching, dipole polarization, and conduction loss, thus inheriting excellent EMW absorption performance. Consequently, L-MXene, N-MXene NRs, P-MXene ML, and P-MXene L enable a reflection loss (RL ) value of -43.14, -63.01, -60.45, and -56.50 dB with a matching thickness of 0.95, 1.51, 3.83, and 4.65 mm, respectively.

Wide-temperature-range multispectral camouflage enabled by orientation-gradient co-optimized microwave blackbody metastructure coupled with conformal MXene coating

Cloaking against electromagnetic detection is a well-researched topic; yet achieving multispectral camouflage over a wide temperature range remains challenging. Herein, an orientation-gradient co-optimized graded Gyroid-shellular (GGS) SiOC-based metastructure with a conformal MXene coating (M@SiOC) is proposed to achieve wide-temperature-range microwave/infrared/visible-light-compatible camouflage. Firstly, the combination of coordinate transformation and genetic algorithm endows the GGS architecture with optimal orientation and gradient, allowing superior microwave blackbody-like behavior. Secondly, a microwave-transparent, low-infrared-emissivity MXene metasurface is constructed in situ to permit wide-temperature-range infrared camouflage. Finally, the outstanding spectral selectivity of MXene enables camouflage against 1.06 μm-lidar and visible-light detection. As a result, the as-fabricated [110]-oriented GGS M@SiOC metamaterials exhibit outstanding wide-temperature-range multispectral camouflage: (i) ultrabroadband microwave absorption exceeding 80% in the X-Ku band from room temperature (RT) to 500 °C with absorption above 86.0% (91.4% on average) at 500 °C; (ii) excellent long-wavelength infrared camouflage for object temperatures from RT to 450 °C, reaching an infrared signal intensity of 78.5% for objects at 450 °C; and (iii) camouflage against both 1.06 μm-lidar and dark environment. Compared with traditional hierarchical metamaterials necessitating complex micro/nano-fabrication processes, this work provides a novel pathway toward the realization of structurally integrated multispectral stealth components by combining flexible metastructure design and high-fidelity additive manufacturing.

Controlled formation of multiple core-shell structures in metal-organic frame materials for efficient microwave absorption

The design of metal-organic frameworks (MOF) derived composites with multiple loss mechanisms and multi-scale micro/nano structures is an important research direction of microwave absorbing materials. Herein, multi-scale bayberry-like Ni-MOF@N-doped carbon composites (Ni-MOF@NC) are obtained by a MOF assisted strategy. By utilizing the special structure of MOF and regulating its composition, the effective improvement of Ni-MOF@NC's microwave absorption performance has been achieved. The nanostructure on the surface of core-shell Ni-MOF@NC can be regulated and N doping on carbon skeleton by adjusting the annealing temperature. The optimal reflection loss of Ni-MOF@NC is -69.6 dB at 3 mm, and the widest effective absorption bandwidth is 6.8 GHz. This excellent performance can be attributed to the strong interface polarization caused by multiple core-shell structures, the defect and dipole polarization caused by N doping, and the magnetic loss caused by Ni. Meanwhile, the coupling of magnetic and dielectric properties enhances the impedance matching of Ni-MOF@NC. The work proposes a particular idea of designing and synthesizing an applicable microwave absorption material that possesses excellent microwave absorption performance and promising application potential.

Improved lithium ion storage performance of Ti3C2Tx MXene@S composite with carboxymethyl cellulose binder

MXenes are regarded as promising electrode materials for lithium-ion batteries owing to their high electrical conductivity and two-dimensional structure but suffer from low intrinsic specific capacities. In this study, we fabricate sulphur-doped multilayer Ti₃C₂T_x MXenes via calcination and annealing using sublimed sulphur as the sulphur source. After sulphur doping, the interlayer spacing of Ti₃C₂T_x increases, which is favourable for Li-ion insertion. The Ti₃C₂T_x MXene@S composite exhibits excellent electrochemical performance. A high reversible specific capacity of 393.8 mAh g^-1 at a current density of 100 mA g^-1 after 100 cycles is obtained. Additionally, a negative fading phenomenon is observed when the specific capacity increases to 858.9 mAh g^-1 after 2550 cycles at 1 A g^-1 and to 322.2 mA h g^-1 after 3600 cycles at 5 A g^-1 from the initial 267.3 mAh g^-1. We systematically investigate the effects of two different binders (polyvinylidene difluoride and carboxymethyl cellulose, hereinafter abbreviated as PVDF and CMC, respectively) on the electrochemical performance of the Ti₃C₂T_x MXene@S composite and discovered that the electrode using the CMC binder exhibits better lithium-ion storage performance than that using the PVDF binder, which is attributed to the lower charge transfer resistance, higher ion diffusivity, and enhanced adhesion force.

Highly Performant Electromagnetic Absorption at the X Band Based on Co@NCS/Ti3C2Tx Composites

Electromagnetic waves at the X band (8.2-12.4 GHz) play significant roles in military applications such as radar, satellite, and wireless communication. However, within this band range, the developed performance of electromagnetic absorption (EMA) is still unsatisfied, and it is hard to settle the corresponding problems on radar stealth and electromagnetic pollution. Herein, we demonstrate a state-of-the-art EMA property of -82.6 dB at 8.24 GHz with 2.57 mm thickness and 30 wt % paraffin filling ratio. For this purpose, an optimal Co@NCS/Ti₃C₂T_x composite is prepared by an electrostatic self-assembly approach through compelling Co-loading of nitrogen-doped carbon sheets (Co@NCS) derived from the pyrolysis of ZIF-67 (CoZn) with 2D Ti₃C₂T_x MXene nanosheets. Experimental results show that the highly efficient EMA performance of this Co@NCS/Ti₃C₂T_x composite originates from the large surface area for multiple reflection and electromagnetic wave scattering, from abundant defects sites for dipole and interfacial polarization, and from the optimizing impedance matching by the combination of Co magnetic nanoparticles and conductive NCS/Ti₃C₂T_x composite. These results confirm that the as-fabricated composites possess scientific and practical values for EMA applications at the X band, paving the way for developing highly performant electromagnetic absorbers toward specific microwave bands.

Facile preparation of Ti3C2Tx sheets by selectively etching in a H2SO4/H2O2 mixture

MXenes and MXene-based composite materials have potential applications in a wide range of areas due to their unique physical and chemical characteristics. At present, it is still a major challenge to develop a simple, safe, and efficient route to prepare MXenes without using fluorinated etchants. Herein, we design a facile method to prepare Ti₃C₂T_x MXene sheets by selectively etching Ti₃AlC₂ powders in an aqueous diluted H₂SO₄ solution with H₂O₂ as an oxidant. In a system of H₂SO₄ and H₂O₂, an aqueous H₂SO₄ solution with a concentration of 6 mol/L is a strongly acidic medium with no volatility, and 30% H₂O₂ acts as a strong green oxidizer without harmful by-products. The experimental process is safe and convenient to conduct in a beaker under a water bath of 40°C. The etching process can be completed in 1 h under the air atmosphere conditions. The experimental results confirmed that the etched Ti₃AlC₂ powders can be successfully separated into Ti₃C₂T_x nanosheets under ultrasound treatment without using any intercalation agent. The relevant etching mechanism is may be attributed to the synergy effect of H₂SO₄ and H₂O₂, which triggers sequential selective etching of Al layers from the Ti₃AlC₂ phase. It may provide a new green way to prepare MXene-based materials without using toxic HF or HF-containing etchants.

Lightweight electromagnetic wave absorbent composites with Fe3O4 nanocrystals uniformly decorated on the surface of carbon spheres

The application of electromagnetic waves has reached every aspect of human life, but the search for superior electromagnetic wave absorbent materials has been a constant quest of researchers. The application of heterogeneous structures has been favored by researchers of electromagnetic wave absorbent materials and the quest for simple preparation methods and homogeneous distribution of heterogeneous structures is continuing. In this study, we synthesized carbon sphere/Fe₃O₄ nanocrystal (CS/Fe₃O₄) composites by uniformly decorating Fe₃O₄ nanoparticles on the surface of carbon spheres through a simple strategy of expanding the heterogeneous structured interface. The heterogeneous interface formed by graphite and amorphous carbon in the carbon spheres is a boundary-type defect and combined with the magnetic loss capability of the Fe₃O₄ nanocrystals, this composite material has excellent electromagnetic wave absorption properties. The composite material synthesized with 0.05 M solution of iron nitrate has the best electromagnetic wave absorption performance of all samples due to the synergistic effect of interfacial polarization, eddy current loss, defect engineering, and magnetic energy attenuation capability. Reflection losses of -50.932 dB and -49.143 dB were achieved at 4.65 GHz and 10.6 GHz respectively, corresponding to thicknesses of 3.74 mm and 1.74 mm. In addition, the widest effective absorption bandwidth (EAB) at 1.27 mm was 4.5 GHz (13.50-18 GHz). This study enhances the electromagnetic wave absorption performance of carbon spheres by surface-decorating Fe₃O₄ nanoparticles, solves the problem of homogeneity of decorative magnetic oxides on the surface of carbon-based materials, and provides new ideas for the design of controllable, lightweight, ultra-thin composites of carbon-based electromagnetic wave absorbent materials that possess strong electromagnetic wave absorption capability.

Enhanced Electromagnetic-Wave Absorbing Performances and Corrosion Resistance via Tuning Ti Contents in FeCoNiCuTix High-Entropy Alloys

Efficient and stable electromagnetic-wave (EMW) absorption materials have attracted great attention in the field of reducing microwave pollution. Herein, FeCoNiCuTi_x high-entropy alloys (HEAs) as electromagnetic-wave absorbing materials were prepared by a high-energy ball-milling method. The as-milled HEA powders presented a flaky shape with a high aspect ratio. Impedance matching was efficiently optimized by severe lattice distortion, which was caused by Ti incorporation. The introduced plentiful defects in FeCoNiCuTi_x HEAs provided abundant polarization sites for dielectric loss. By tuning Ti contents, FeCoNiCuTi_0.2 HEAs delivered excellent EMW absorption performances. The maximal reflection loss (RL_max) values reached -47.8 dB at 10.86 GHz as thin as 2.16 mm, and the widest bandwidth was 4.76 GHz (5.97-10.73 GHz). Furthermore, the introduction of Ti enhanced corrosion resistance via increasing the charge transfer resistance of a passivated film. Those characteristics of FeCoNiCuTi_x HEAs made these materials a practical gigahertz-range EMW absorber. Additionally, our findings provided a facile and tunable strategy for designing EMW absorbing materials, which was aimed at lightweight, highly efficient absorption, and resistance to harsh environments.

MoS2 /MXene Aerogel with Conformal Heterogeneous Interfaces Tailored by Atomic Layer Deposition for Tunable Microwave Absorption

In the design of electromagnetic (EM) wave absorbing materials, it is still a great challenge to optimize the relationship between the attenuation capability and impedance matching synergistically. Herein, a 3D porous MoS2 /MXene hybrid aerogel architecture with conformal heterogeneous interface has been built by atomic layer deposition (ALD) based on specific porous templates to optimize the microwave absorption (MA) performance comprehensively. The original porous structure of pristine Ti3 C2 Tx aerogel used as templates can be preserved well during ALD fabrication, which prolongs the reflection and scattering path and ameliorates the dielectric loss. Meanwhile, plenty of heterointerfaces between MoS2 and Ti3 C2 Tx have been fabricated based on conformally ALD-deposited MoS2 with controlled thickness on the porous surfaces of the templates, which can effectively optimize the impedance matching and transform its response to EM waves from shielding into absorbing. Moreover, the interaction between the attenuation capability and impedance matching can also be modulated by the number of ALD cycle in MoS2 fabrication. After optimization, MoS2 /MXene hybrid aerogel obtained under 300 ALD cycles shows a minimum reflection loss of -61.65 dB at the thickness of 4.53 mm. In addition, its preferable lightweight, high surface area, mechanical, and hydrophobicity properties will also be conducive to further practical applications.

Interconnected magnetic carbon@NixCo1-xFe2O4 nanospheres with core-shell structure: An efficient and thin electromagnetic wave absorber

The applications of cobalt ferrite and nickel ferrite composite materials on electromagnetic (EM) wave absorption are the research hotspot currently. However, the systematical comparison study between these two ferrites composites have rarely been carried out. Thus, the EM wave absorption performance of interconnected carbon@Ni_xCo_1-xFe₂O₄ composites with core-shell structures were investigated comprehensively in this work. A series of magnetic nanospheres including NiFe₂O₄, cobalt-doped nickel ferrite, nickel-cobalt ferrite, nickel-doped cobalt ferrite and CoFe₂O₄ were synthesized firstly, and then uniformly encapsulation by carbon rendered the corresponding C@Ni_xCo_1-xFe₂O₄ composites nanospheres. Synthesis reactions involved for C@Ni_xCo_1-xFe₂O₄ formation were investigated in detail, and afterwards their magnetic behavior, EM wave absorption performance and absorbing mechanism were thoroughly explored and analyzed. Results show that when nickel is dominant element and cobalt is doping element (Ni_0.75Co_0.25Fe₂O₄), the composite nanosphere exhibits optimum EM wave absorption performance. When the sample thickness is just 1.9 mm, its RL_min value can reach -51 dB, and the corresponding EAB width is 3.3 GHz. The synthesized C@Ni_0.75Co_0.25Fe₂O₄ can be qualified as an efficient and thin electromagnetic wave absorber, which is mainly attributed to its special structure, fair electromagnetic matching and impedance matching.

Construction of one-dimensional MoO2/NC heteronanowires for microwave absorption

A combination of a special micro–nanostructure and multiple components has been proven as an effective strategy to strengthen the microwave attenuation capacity. In this work, one-dimensional MoO₂/N-doped carbon (NC) nanowires with a heterostructure have been successfully prepared by utilizing mild in situ chemical oxidative polymerization and pyrolysis treatment. After compounding them with a thermoplastic polyurethane (TPU) matrix, the flexible composites exhibit tunable wave absorbing performance by modulating the filler loading of MoO₂/NC heteronanowires. Experimental results demonstrate that the minimum reflection loss value of the MoO₂/NC–TPU hybrid is up to −35.0 dB at 8.37 GHz under a thickness of only 2.3 mm with 40 wt% filler amounts. Moreover, the effective absorption bandwidth enables 3.26 GHz to be achieved (8.49–11.75 GHz) when the thickness changes to 2.0 mm, covering almost the whole X-band. Meanwhile, when the filler loading becomes 30 wt%, dual-absorption peaks appear. The relevant absorption mechanism is mainly attributed to the dielectric loss including strong dipolar/interfacial polarizations, Debye relaxation loss and multiple reflection and scattering.

A combination of a special micro–nanostructure and multiple components has been proven as an effective strategy to strengthen the microwave attenuation capacity.

MOF-derived NiFe2S4/Porous carbon composites as electromagnetic wave absorber

The preparation of strong absorption, thin thickness and wide band electromagnetic wave absorbers has always been the focus of research. In this paper, NiFe₂S₄/PC composites, an electromagnetic wave absorbing material with excellent performance, is prepared by introducing Ni-MOF, Fe and S elements into porous carbon framework. The material has a minimum reflection loss (RL_min) of -51.41 dB and the matching thickness is only 1.8 mm. In addition, the effective absorption bandwidth (EAB) is 4.08 GHz when the thickness is 1.9 mm. The rich interface and good impedance matching characteristics are the main reasons for the excellent absorbing performance of the material. The experimental results show that NiFe₂S₄/PC composites is a reasonable and effective electromagnetic wave absorption material.

Recent Advances in MXene/Polyaniline-Based Composites for Electrochemical Devices and Electromagnetic Interference Shielding Applications

Due to serious global warming and environmental issues, the demand for clean and sustainable energy storage devices is significantly increased. Often accompanied by rapid growth of portable electronic vehicles and devices, massive electromagnetic wave pollution becomes unavoidable. To mitigate the above two issues, this mini-review summaries preparation methods and recent developments of MXene/polyaniline-based composites for their applications in electrochemical devices and electromagnetic interference shielding. Based on excellent synergistic effects between single compounds and designed hierarchical structures, MXene/polyaniline-based composites usually exhibit enhanced physical and chemical properties, showing great potentials in sustainable electrochemical properties and electromagnetic wave protections for human health as well as normal operation of precise electronic devices.

Flexible and Waterproof 2D/1D/0D Construction of MXene-Based Nanocomposites for Electromagnetic Wave Absorption, EMI Shielding, and Photothermal Conversion

ABSTRACT

High-performance electromagnetic wave absorption and electromagnetic interference (EMI) shielding materials with multifunctional characters have attracted extensive scientific and technological interest, but they remain a huge challenge. Here, we reported an electrostatic assembly approach for fabricating 2D/1D/0D construction of Ti₃C₂T_x/carbon nanotubes/Co nanoparticles (Ti₃C₂T_x/CNTs/Co) nanocomposites with an excellent electromagnetic wave absorption, EMI shielding efficiency, flexibility, hydrophobicity, and photothermal conversion performance. As expected, a strong reflection loss of -85.8 dB and an ultrathin thickness of 1.4 mm were achieved. Meanwhile, the high EMI shielding efficiency reached 110.1 dB. The excellent electromagnetic wave absorption and shielding performances were originated from the charge carriers, electric/magnetic dipole polarization, interfacial polarization, natural resonance, and multiple internal reflections. Moreover, a thin layer of polydimethylsiloxane rendered the hydrophilic hierarchical Ti₃C₂T_x/CNTs/Co hydrophobic, which can prevent the degradation/oxidation of the MXene in high humidity condition. Interestingly, the Ti₃C₂T_x/CNTs/Co film exhibited a remarkable photothermal conversion performance with high thermal cycle stability and tenability. Thus, the multifunctional Ti₃C₂T_x/CNTs/Co nanocomposites possessing a unique blend of outstanding electromagnetic wave absorption and EMI shielding, light-driven heating performance, and flexible water-resistant features were highly promising for the next-generation intelligent electromagnetic attenuation system. [Image: see text]

HIGHLIGHTS

The 2D/1D/0D Ti₃C₂T_x/carbon nanotubes/Co nanocomposite is successfully synthesized via an electrostatic assembly. Nanocomposites exhibit an excellent electromagnetic wave absorption and a remarkable electromagnetic interference shielding efficiency. The flexible, waterproof, and photothermal conversion performances are achieved.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s40820-021-00673-9.

Alternate-Layered MXene Composite Film-Based Triboelectric Nanogenerator with Enhanced Electrical Performance

The output power of the triboelectric nanogenerator (TENG) strongly depends on the performance of triboelectric materials, especially microstructures and functional groups of them. In this work, aiming at the excellent triboelectric ability, alternate-layered MXene composite films-based TENG with abundant fluorine groups(-F) through layer-by-layer stacking are designed and fabricated. Benefitting from the uniform intrinsic microstructure and increased dielectric constant, when the amount of the Nb₂CT_x nanosheets increases to 15 wt%, the TENG based on Nb₂CT_x/Ti₃C₂T_x composite nanosheets films achieves the maximum output. The short-circuit current density of 8.06 μA/cm² and voltage of 34.63 V are 8.4 times and 3.5 times over that of pure Ti₃C₂T_x films, and 3.3 times and 4.3 times over that of commercial poly(tetrafluoroethylene) (PTFE) films, respectively. Furthermore, the fabricated TENG could be attached to human body to harvest energy from human motions, such as typing, texting, and hand clapping. The results demonstrate that the alternate-layered MXene composite nanosheet films through layer-by-layer stacking possess remarkably triboelectric performance, which broaden the choice of negative triboelectric materials and supply a new choice for high output TENG.

MoS2-Decorated/Integrated Carbon Fiber: Phase Engineering Well-Regulated Microwave Absorber

Phase engineering is an important strategy to modulate the electronic structure of molybdenum disulfide (MoS2). MoS2-based composites are usually used for the electromagnetic wave (EMW) absorber, but the effect of different phases on the EMW absorbing performance, such as 1T and 2H phase, is still not studied. In this work, micro-1T/2H MoS2 is achieved via a facile one-step hydrothermal route, in which the 1T phase is induced by the intercalation of guest molecules and ions. The EMW absorption mechanism of single MoS2 is revealed by presenting a comparative study between 1T/2H MoS2 and 2H MoS2. As a result, 1T/2H MoS2 with the matrix loading of 15% exhibits excellent microwave absorption property than 2H MoS2. Furthermore, taking the advantage of 1T/2H MoS2, a flexible EMW absorbers that ultrathin 1T/2H MoS2 grown on the carbon fiber also performs outstanding performance only with the matrix loading of 5%. This work offers necessary reference to improve microwave absorption performance by phase engineering and design a new type of flexible electromagnetic wave absorption material to apply for the portable microwave absorption electronic devices.

MXene derivatives: synthesis and applications in energy convention and storage

Transition metal carbides or nitrides (MXene) have shown promising applications in energy convention and storage (ECS), owing to their high conductivity and adjustable surface functional groups. In the past several years, many MXene derivatives with different structures have been successfully prepared and their impressive performance demonstrated in ECS. This review summarizes the progress in the synthesis of MXene and typical Ti3C2T x MXene derivatives with different morphologies, including 0D quantum dots, 1D nanoribbons, 2D nanosheets and 3D nanoflowers. The mechanisms involved and their performance in photocatalysis, electrocatalysis and rechargeable batteries are also discussed. Furthermore, the challenges of MXene derivatives in ECS are also proposed.

Synthesis of 3D flower-like ZnO/ZnCo2O4 composites with the heterogeneous interface for excellent electromagnetic wave absorption properties

Reasonable structure and composition are essential for electromagnetic wave absorption (EMW). Herein, ZnO hollow spheres were prepared with carbon spheres as templates and then synthesized ZnO/ZnCo₂O₄ composites by the solvothermal method and annealing treatment. The flower-like ZnCo₂O₄ material was produced by self-assembly of ZnCo₂O₄ nanosheets. The absorbing material with the complex structure has multiple scattering and reflection, conduction loss, resonance, and eddy current loss characteristics. Furthermore, the addition of ZnO hollow spheres has a significant impact on electromagnetic parameters and absorption properties. As a result, the addition of ZnO hollow spheres can greatly enhance the complex permittivity of the ZnO/ZnCo₂O₄ composites and obtain excellent EMW absorbing properties. It is worth noting that ZnO/ZnCo₂O₄ composites show the best EMW absorption properties when the ZnO hollow spheres were added up to 5 mg. The minimum reflection loss is -55.42 dB and a matching thickness of 1.99 mm while the maximum effective absorption bandwidth can also reach 7.44 GHz with a matching thickness of 2.4 mm. Our research can prove that the structure and composition have a significant influence on the properties of the absorbing material, which provides ideas for the development of absorbing materials with high-performance.