Multifunctional CoFe2O4@MXene-AgNWs/Cellulose Nanofiber Composite Films with Asymmetric Layered Architecture for High-Efficiency Electromagnetic Interference Shielding and Remarkable Thermal Management Capability

Cellulose-Based Electromagnetic Functional Aerogels: Mechanism, Fabrication, Structural Design, and Application

Electromagnetic functional materials offer a promising solution to reduce impacts from electromagnetic pollution and interference, such as digital communications, national defenses, and military fields. Cellulose-based aerogels, featured with their hierarchical porous structure, high specific surface area, and surface activity, can be engineered to possess electromagnetic wave shielding and absorption capabilities through structural regulation, composition optimization, and material functionalization. Moreover, these cellulose-based aerogels exhibit remarkable renewability and biocompatibility, highlighting their significant potential in the field of electromagnetic functional materials. In this review, we stigmatically overview the state-of-the-art of cellulosic electromagnetic functional aerogels, which begins with elucidating the mechanisms behind electromagnetic interference shielding and microwave absorption. The material design based on the physical and chemical characteristics of cellulose aerogels is discussed. Furthermore, the hierarchical design strategies of the cellulosic electromagnetic functional aerogels are reviewed including macro-structures, micro/nanostructures, and supramolecular structures. Multifunctional applications of cellulose electromagnetic functional aerogels are presented, such as infrared and radar stealth materials, intelligent responsive electromagnetic devices, and radiation protection equipment. Finally, an up-to-date summary and an outlook on developing the cellulose-based electromagnetic functional aerogels are provided in the fields of electromagnetic interference shielding and microwave absorption, as well as outlining future research perspectives.

Modification of carbonized lignocellulose framework with FeNi-SnOx heterojunctions for enhanced electromagnetic interference shielding

Natural wood, a porous lignocellulosic resource, is an ideal precursor for carbon frameworks owing to its renewability. However, achieving a high electromagnetic shielding effectiveness poses a tremendous challenge for lignocellulose-based carbon framework. Herein, we developed a new material (FeNi-SnOx/CW) by embedding FeNi alloy and SnOx nanoparticles in carbonized lignocellulose framework (CW) from delignified wood using interface engineering modification. The CW acted as a conductive scaffold, while FeNi-SnOx enhanced polarization and magnetoelectric properties. Due to the synergistic effect of multiple mechanisms, the FeNi-SnOx/CW achieved excellent conductivity (437.3 S/m) and high saturation magnetization (13.33 emu/g). It also demonstrated a high EMI SE of 91.2 dB and a high ratio of SEA/SET up to 85 % across the X-band at 2 mm thickness. Significantly, the interface engineering modification has resulted in a 59.2 dB enhancement in the EMI SE properties of the composite material compared to the pure CW (32.0 dB). Surface hydrophobicity modification with PDMS of the FeNi-SnOx/CW composite had a negligible impact on its EMI SE, thereby highlighting its practical potential. This research shows the benefits of FeNi-SnOx in boosting EMI shielding and offers a way to use renewable wood-based lignocellulose for high-performance EMI shielding materials.

Filler-free cellulose nanofiber composite papers with excellent mechanical properties for efficient electromagnetic interference shielding

The vast majority of conductive polymer composites (CPCs) currently available for electromagnetic interference (EMI) shielding rely on inorganic conductive fillers to construct conductive networks. However, the strategy inevitably causes some compromises in the biocompatibility, biodegradability, and mechanical properties of CPCs. In this work, the filler-free and high conductive cellulose nanofiber (CNF) composite papers containing poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) doped by lithium bis(trifloromethanesulfonyl) imide (Li-TFSI) are reported. The resultant Li-TFSI@PEDOT:PSS/CNF (LPPC) composite papers exhibit an exceptional absolute EMI shielding effectiveness of 14,525.5 dB∙cm-1, surpassing the reported values of many CPCs-based EMI shielding materials containing inorganic fillers. Li-TFSI can induce the structural reorganization of PEDOT chains. The conductivity of Li-TFSI@PEDOT:PSS was boosted with the enhancement of the crystalline order and oxidation level of PEDOT chains. Furthermore, the obtained LPPC composite papers demonstrate outstanding mechanical properties with a tensile strength of 44.42 MPa and EMI shielding stability with a retention ratio of up to 97 %, which are desirable for EMI shielding in wearable devices. Therefore, this work provides a feasible strategy to construct filler-free CPCs-based EMI shielding materials, which are expected to provide electromagnetic protection for the next flexible devices.

A Review on MXene/Nanocellulose Composites: Toward Wearable Multifunctional Electromagnetic Interference Shielding Application

With the rapid development of mobile communication technology and wearable electronic devices, the electromagnetic radiation generated by high-frequency information exchange inevitably threatens human health, so high-performance wearable electromagnetic interference (EMI) shielding materials are urgently needed. The 2D nanomaterial MXene exhibits superior EMI shielding performance owing to its high conductivity, however, its mechanical properties are limited due to the high porosity between MXene nanosheets. In recent years, it has been reported that by introducing natural nanocellulose as an organic framework, the EMI shielding and mechanical properties of MXene/nanocellulose composites can be synergically improved, which are expected to be widely used in wearable multifunctional shielding devices. In this review, the electromagnetic wave (EMW) attenuation mechanism of EMI shielding materials is briefly introduced, and the latest progress of MXene/nanocellulose composites in wearable multifunctional EMI shielding applications is comprehensively reviewed, wherein the advantages and disadvantages of different preparation methods and various types of composites are summarized. Finally, the challenges and perspectives are discussed, regarding the performance improvement, the performance control mechanism, and the large-scale production of MXene/nanocellulose composites. This review can provide guidance on the design of flexible MXene/nanocellulose composites for multifunctional electromagnetic protection applications in the future intelligent wearable field.

Nanocellulose-based conductive composites: A review of systems for electromagnetic interference shielding applications

Electronic systems and telecommunications have grown in popularity, leading to increasing electromagnetic (EM) radiation pollution. Environmental protection from EM radiation demands the use of environmentally friendly products. The design of EM interference (EMI) shielding materials using resources like nanocellulose (NC) is gaining traction. Cellulose, owing to its biocompatibility, biodegradability, and excellent mechanical and thermal properties, has attracted significant interest for developing EMI shielding materials. Recent advancements in cellulose-based EMI shielding materials, particularly modified cellulosic composites, are highlighted in this study. By incorporating metallic coatings compounded with conductive fillers and modified with inherently conductive elements, conductivity and effectiveness of EMI shielding can be significantly improved. This review discusses the introduction of EMI shields, cellulose, and NC, assessing environmentally friendly EMI shield options and diverse NC-based composite EMI shields considering their low reflectivity. The study offers new insights into designing advanced NC-based conductive composites for EMI shielding applications.

Nacre-like Anisotropic Multifunctional Aramid Nanofiber Composites for Electromagnetic Interference Shielding, Thermal Management, and Strain Sensing

Developing multifunctional flexible composites with high-performance electromagnetic interference (EMI) shielding, thermal management, and sensing capacity is urgently required but challenging for next-generation smart electronic devices. Herein, novel nacre-like aramid nanofibers (ANFs)-based composite films with an anisotropic layered microstructure were prepared via vacuum-assisted filtration and hot-pressing. The formed 3D conductive skeleton enabled fast electron and phonon transport pathways in the composite films. As a result, the composite films showed a high electrical conductivity of 71.53 S/cm and an outstanding thermal conductivity of 6.4 W/m·K when the mass ratio of ANFs to MXene/AgNWs was 10:8. The excellent electrical properties and multi-layered structure endowed the composite films with superior EMI shielding performance and remarkable Joule heating performance, with a surface temperature of 78.3 °C at a voltage of 2.5 V. Additionally, it was found that the composite films also exhibited excellent mechanical properties and outstanding flame resistance. Moreover, the composite films could be further designed as strain sensors, which show great promise in monitoring real-time signals for human motion. These satisfactory results may open up a new opportunity for EMI shielding, thermal management, and sensing applications in wearable electronic devices.

MXene Composite Electromagnetic Shielding Materials: The Latest Research Status

MXene emerges as a premier candidate for electromagnetic shielding owing to its unique properties as a novel two-dimensional material. Its exceptional electrical conductivity, chemical reactivity, surface tunability, and facile processing render it highly suitable for diverse electromagnetic shielding applications. The research status of MXene and MXene-based electromagnetic shielding materials is systematically discussed in this paper. First, the research status of MXene as a single-component electromagnetic shielding material is briefly introduced. Subsequently, the research status of composite structures constructed by MXene with polymers, carbon derivatives, and ferrites is introduced in detail. Furthermore, the research progress of MXene-based ternary and quaternary composite electromagnetic shielding materials is further focused. Finally, the application of MXene-based composite electromagnetic shielding materials is prospected. A deeper understanding of MXene's electromagnetic shielding properties is facilitated by this paper, providing the direction for the future development of two-dimensional materials in the design and processing of electromagnetic shielding materials.

Flexible Sandwich-Shaped Cellulose Nanocrystals/Silver Nanowires/MXene Films Exhibit Efficient Electromagnetic-Shielding Interference Performance

The electromagnetic pollution problem is becoming increasingly serious due to the speedy advance of electronic communication devices. There are broad application prospects for the development of flexible, wearable composite films with high electromagnetic interference (EMI)-shielding performance. The MX@AC composite films were prepared from MXene, silver nanowires (AgNWs) and cellulose nanocrystals (CNCs) with a sandwich structure. Benefiting from the upper and lower frame structure formed by winding 1D AgNWs and CNC, the tensile strength of the MX@AC was improved to 35 MPa (12.5 wt% CNC content) from 4 MPa (0 wt% CNC content). The high conductivity of MXene and AgNWs resulted in the MX@AC composite film conductivity up to 90,670 S/m, EMI SE for 90 dB, as well as SSE/t up to 7797 dB cm2 g-1. And the MX@AC composite film was tested for practical application, showing that it can effectively isolate electromagnetic waves in practical application.

Fabrication of highly conductive, flexible, and hydrophobic Kevlar®@Ni-P-B@Cu@CS fabric with excellent self-cleaning performance for electromagnetic interference shielding

In this work, a simple and cost-effective method was proposed and developed to prepare a novel multilayer-structured Kevlar®@nickel-phosphorus-boron@copper@copper stearate (Kevlar®@Ni-P-B@Cu@CS) composite fabric with high conductivity, high flexibility, high hydrophobicity, and high durability to effectively shield electromagnetic interference (EMI). In this method, an amorphous Ni-P-B alloy nanolayer was initially deposited onto a Kevlar® fabric via electroless plating. Afterward, a crystalline Cu nanolayer was deposited as the second layer via electroplating. Finally, a monolayer of copper stearate was innovatively self-assembled as the outermost protective layer. The Cu deposition was effectively adjusted and designed by controlling the plating current and plating time. The electrical resistance and contact angle of the optimized Kevlar®@Ni-P-B@Cu@CS composite fabric were as low as 3.2 mΩ sq-1 and as high as 115.39°, respectively, indicating that the fabric could withstand bending, tape-off, corrosion, and accelerated environmental tests. The average EMI-shielding efficiency of the durable composite fabric was 93.9 dB in the frequency range of 8.2-12.4 GHz, which was mainly attributed to the absorption loss. Thus, the proposed material configuration has promise for applications in aviation, aerospace, telecommunication, wearable devices, and military industries.

Succulent-Inspired Implicit Structural Change for Smart "ON/OFF" Switchable and Flexible EMI Shielding Coating

Modern miniaturized intelligent electronics call for smart switchable and flexible electromagnetic interference (EMI) shielding material for highly precise applications. However, most switchable EMI shielding materials are based on an explicit structural change. Herein, we report a succulent-inspired smart switchable MXene (WR-MXene) coating film realized by inner implicit structural change, which benefits from the insertion of our reversible large-cavity yolk-shell biomicrospheres. The novel switchable yolk-shell biomicrospheres contain a soft N-isopropylacrylamide (PNIPAM) hydrogel core, an "ON/OFF" switchable cavity (over 30% volume fraction), and a porous polydopamine (p-PDA) shell. The yolk-shell biomicrospheres can be obtained by a facile two-step polymerization and a simple drying-dehydration treatment. Because of the "ON/OFF" switchable void space brought by the smart biomicrospheres and conductive framework of MXene, an optimized ultralight and flexible WR-MXene coating film (vWR-coating film) showed both large switchable change (over 60 dB) and extraordinary EMI shielding effectiveness, reaching 95 and over 50 dB in the whole X band (8.2-12.4 GHz). These novel reversible yolk-shell biomicrospheres and the succulent-inspired switchable coating films are promising for smart flexible wearable devices and many advanced multifunctional systems needing dynamic real-time response.

An Integrated Approach for Piezo-Electrochemical Nanoenergy Generation, Storage, and Real-Time Electromagnetic Interference Shielding Control

The extensive utilization of high-end wireless electronic equipment in medical, robotics, satellite, and military communications has created a pressing challenge for real-time electromagnetic interference (EMI) control. Herein, a piezo-powered self-chargeable supercapacitor (PPSC) architecture based on an iron-doped graphitic nitride (Fe-g-C3N4: FGN) electrode with a solid piezoelectrolyte is devised, which can provide real-time controlled EMI shielding through piezo-powered self-charging voltage (SCV). This PPSC device along with real-time SCV-controlled EMI shielding also integrates additional features like nanoenergy generation and storing capability. The results demonstrate that the PPSC device is capable of exhibiting a piezo-tuned self-charging ability of up to 669.2 mV under 9.47 N of dynamic pressing for 180 s. The SCV electrostatically modifies the PPSC device that causes destructive interference and governs the absorption of electromagnetic radiation (EMR) and controls the absorption-dominated EMI shielding up to 59.2 dB at 500 mV. Additionally, the SCV-led electrification of the PPSC device also controls a unique functional transition from the EMR reflector to the EMR absorber at ∼90 mV. Hence, this strategy of tailored absorption and reflection adjustments of EMR could also potentially contribute toward the advancement of stealth technology for military armaments with externally controlled stealth capabilities.

Recent advances in the development of MXenes/cellulose based composites: A review

Over the past few years, transition metal carbides, nitrides, and carbonitrides, commonly referred to as MXenes have been discovered and utilized quickly in a range of technical fields due to their distinctive and controlled characteristics. MXenes are a new class of two-dimensional (2D) materials that have found extensive use in a variety of fields, including energy storage, catalysis, sensing, biology, and other scientific disciplines. This is because of their exceptional mechanical and structural characteristics, metal electrical conductivity, and other outstanding physical and chemical properties. In this contribution, we review recent cellulose research advances and show that MXene hybrids are effective composites that benefit from cellulose superior water dispersibility and the electrostatic attraction between cellulose and MXene to prevent MXene accumulation and improve the composite's mechanical properties. Electrical, materials, chemical, mechanical, environmental, and biomedical engineering are all fields in which cellulose/MXene composites are used. These properties and applications-based reviews on MXene/cellulose composite, critically analyze the results and accomplishments in these fields and provide context for potential future research initiatives. It examines newly reported applications for cellulose nanocomposites assisted by MXene. To support their development and future applications, perspectives and difficulties are suggested in the conclusion.

MOF-Derived Co/C and MXene co-Decorated Cellulose-Derived Hybrid Carbon Aerogel with a Multi-Interface Architecture toward Absorption-Dominated Ultra-Efficient Electromagnetic Interference Shielding

Exploring electromagnetic interference (EMI) shielding materials with ultra-efficient EMI shielding effectiveness (SE) and an absorption-dominated mechanism is urgently required for fundamentally tackling EMI radiation pollution. Herein, zeolitic imidazolate framework-67 (ZIF-67)/MXene/cellulose aerogels were first prepared via a simple solution mixing-regeneration and freeze-drying process. Subsequently, they are converted into electric/magnetic hybrid carbon aerogels (Co/C/MXene/cellulose-derived carbon aerogels) through a facile pyrolysis strategy. ZIF-67-derived porous Co/C could provide the additional magnetic loss capacity. The resultant electric/magnetic hybrid carbon aerogels exhibit a hierarchically porous structure, complementary electromagnetic waves (EMWs) loss mechanisms, and abundant heterointerfaces. The construction of a porous architecture and the synergy of electric/magnetic loss could greatly alleviate the impedance mismatching at the air-specimen interface, which enables more EMWs to enter into the materials for consumption. Moreover, numerous heterointerfaces among Co/C, Ti₃C₂T_x MXene, and cellulose-derived carbon skeleton induce the generation of multiple polarization losses containing interfacial and dipole polarization, which further dissipate the EMWs. The resultant electric/magnetic hybrid carbon aerogel with a low density (85.6 mg/cm³) achieves an ultrahigh EMI SE of 86.7 dB and a superior absorption coefficient of 0.72 simultaneously. This work not only offers a novel approach to design high-performance EMI shielding materials entailing low reflection characteristic but also broadens the applicability of electric/magnetic hybrid carbon aerogels in aerospace, precision electronic devices, and military stealth instruments.

Multilayer Ultrathin MXene@AgNW@MoS2 Composite Film for High-Efficiency Electromagnetic Shielding

Structure and material composition is crucial in realizing high electromagnetic interference (EMI) shielding effectiveness (SE). Herein, an ultrathin MXene@AgNW@MoS₂ (MAM) composite film that resembles the structure of a pork belly and exhibits superior EMI shielding performance was fabricated via the vacuum-assisted suction filtration process and atomic layer deposition (ALD). The staggered AgNWs form skeletons and intersperse in MXene sheets to build a doped layer with three-dimensional network structures, which improves the electrical conductivity of the film. Based on the optimal dispersion concentration of Ag in doped and single layers, the MXene/AgNW doped layer and AgNW single layer are alternately vacuum-assisted-filtered to obtain laminated structures with multiple heterogeneous interfaces. These interfaces generate interface polarization and increase multiple reflection and scattering, resulting in the increased electromagnetic (EM) wave losses. On the other hand, MoS₂ outer nanolayers fabricated precisely by ALD effectively increases the absorption proportion of electromagnetic waves, reduces the secondary reflection, and improves the stability of EMI shielding properties. Ultimately, an ultrathin MAM film (a thickness of 0.03 mm) with five alternating internal layers and MoS₂ outer layers exhibits an excellent EMI SE of 86.3 dB in the X-band.

Design and Fabrication of Layered Electromagnetic Interference Shielding Materials: A Cost-Effective Strategy for Performance Prediction and Efficiency Tuning

The electromagnetic interference (EMI) shielding market is one of the fast-growing sectors owing to the increasingly complicated electromagnetic environment. Recently, priority has been given to improvise the techniques to fine-tune and predict the shielding properties of structures without exhausting raw materials and reduce the expense as well as the time required for optimization. In this article, we demonstrate an effective and precise method to predict the EMI shielding effectiveness (SE) of materials via simulating the performance of composites having alternate layers of conducting and magnetic materials in a virtual waveguide measurement environment based on the finite element method (FEM). The EMI SE of multilayered heterogeneous arrangements (MHAs) is simulated in the K-band region using ANSYS High Frequency Structure Simulator (HFSS) software, which can be extended to all other bands as well. Various simulations carried out by changing the order of the conducting and magnetic layers and the number of layers revealed that the strategic arrangement of electromagnetic (EM) energy-trapping layers inside the impedance-matching layers in the MHAs significantly contributes toward the enhancement of absorption-dominated EMI shielding. Among the MHAs, the conducting-magnetic-conducting (CMC) systems exhibited the highest shielding effectiveness of above 50 dB. The MHAs are realized for testing using poly(vinylidene fluoride)-based composites of low-cost carbon black and barium hexaferrite, an easily accessible ferrite. Through this study, we propose the idea that materials with high production cost and cumbersome fabrication procedures are not necessary to realize highly efficient shielding materials.

MXene/Ferrite Magnetic Nanocomposites for Electrochemical Supercapacitor Applications

MXene has been identified as a new emerging material for various applications including energy storage, electronics, and bio-related due to its wider physicochemical characteristics. Further the formation of hybrid composites of MXene with other materials makes them interesting to utilize in multifunctional applications. The selection of magnetic nanomaterials for the formation of nanocomposite with MXene would be interesting for the utilization of magnetic characteristics along with MXene. However, the selection of the magnetic nanomaterials is important, as the magnetic characteristics of the ferrites vary with the stoichiometric composition of metal ions, particle shape and size. The selection of the electrolyte is also important for electrochemical energy storage applications, as the electrolyte could influence the electrochemical performance. Further, the external magnetic field also could influence the electrochemical performance. This review briefly discusses the synthesis method of MXene, and ferrite magnetic nanoparticles and their composite formation. We also discussed the recent progress made on the MXene/ferrite nanocomposite for potential applications in electrochemical supercapacitor applications. The possibility of magnetic field-assisted supercapacitor applications with electrolyte and electrode materials are discussed.