Absorption-dominated Electromagnetic Interference Shielding Research Articles

Absorption-dominant electromagnetic interference shielding material using MXene-coated polyvinylidene fluoride foam

MXene (Ti3C2Tx), known for its exceptional electrical conductivity, unique two-dimensional structure, extensive surface functionality, and hydrophilicity, has emerged as a leading candidate for electromagnetic interference (EMI) shielding applications. Despite these excellent characteristics, EMI shielding materials based on MXene mostly utilize the reflection mechanism, which may cause secondary interferences. This study introduces an approach to utilize MXene as absorption-dominant EMI shielding materials. By engineering a porous layer of polyvinylidene fluoride (PVDF) atop MXene nanoflakes, we achieved a synergistic enhancement in EMI shielding effectiveness (SE) and absorptivity. The PVDF foam serves as an effective impedance matching layer, substantially enhancing the absorption of electromagnetic waves into the shielding material. Incorporating electrically conductive MXene nanoflakes to form a thin film creates a robust conductive network, fully leveraging its inherent performance. This network efficiently dissipates EM waves, thereby significantly enhancing the EMI SE. The shielding performance of this composite was thoroughly evaluated across both the X-band (8.2 GHz–12.4 GHz) and the Ka-band (26.5 GHz–40 GHz) frequencies. It demonstrated high EMI SE, attributed to mechanisms predominantly based on absorption. Specifically, it achieved an EMI SE of approximately 63.3 dB with high absorptivity (0.74) in the X-band and approximately 73.3 dB with high absorptivity (0.85) in the Ka-band. These findings underscore its potential as a route to develop absorption-dominant EMI shielding materials.

Aromatic phase change microspheres constructed nanocomposite films for fluorine-free self-cleaning, absorption-dominated EMI shielding, and high-temperature thermal camouflage

The combination of high shielding effectiveness and excellent thermal insulation is highly attractive for electromagnetic interference (EMI) shielding materials, yet remains challenging in the absence of thermal stability and self-cleaning effect. Here, poly(arylene ether nitrile) (PEN), an aromatic super engineering polymer, is synthesized and one-step self-assembled into phase-changeable microspheres in an oil-in-water microemulsion system, synchronously settling thermal lability and leakproof of conventional phase change materials. Pre-functionalized multi-wall carbon nanotubes are subsequently immobilized on PEN-based phase change microspheres for EMI shielding and thermal camouflage compartments. The resultant compartments are integrated into macroscopical nanocomposite films with segregated structures via hot-compressing densification. Due to the 3D interconnected cavities, the shielding effectiveness of the PEN-based nanocomposite film is strikingly up to 43 dB with an excellent absorption coefficient of 0.99. Meanwhile, the nanocomposite film exhibits outstanding thermal camouflage throughout a wide temperature range of 80 to 200 °C at a low thickness of ∼1.5 mm. Interestingly, superb fluorine-free self-cleaning is endowed with its inherent hydrophobic surface (contact angle up to 148.6°) overlaid with micropapillaes. Our work sheds light on such application integration of fluorine-free self-cleaning, absorption-dominated EMI shielding, and high-temperature thermal camouflage.

Capillarity-assisted assembly of composite fibers to enable highly conductive fabrics for electromagnetic interference shielding

Poor adhesion between silver nanomaterials and substrates seriously restricts the development of electronic composite devices. In this work, flexible and conductive silver nanowires/fibroin/degummed silk (AgNWs/fibroin/dSF) composite fibers with high adhesion and conductivity via capillarity-assisted assembly for electromagnetic interference (EMI) shielding are designed and fabricated by a facile and scalable all-solution dip-coating method. The nanocomposite fiber possesses high conductivity with a resistance of 8.8 Ω/cm at a low AgNWs/fibroin loading of 19.3 wt%. The assistance of the capillary force in the fiber highly increases the mass of deposited AgNWs. Furthermore, the AgNWs show high adhesion on the fibers in the tape-peel test. The enhanced deposition factors and mechanisms are detailly investigated. Moreover, the composite fibers are further woven into a soft and flexible fabric. The composite fabric shows an absorption-dominated EMI shielding performance with an efficient shielding effectiveness of 38 dB. The capillarity-assisted assembly is an attractive procedure for constructing high-conductive and uniform coatings for a wide application.

Janus structure design of polyimide composite foam for absorption-dominated EMI shielding and thermal insulation

In the present work, by virtue of the synergistic and independent effects of Janus structure, an asymmetric nickel-chain/multiwall carbon nanotube/polyimide (Ni/MWCNTs/PI) composite foam with absorption-dominated electromagnetic interference (EMI) shielding and thermal insulation performances was successfully fabricated through an ordered casting and directional freeze-drying strategy. Water-soluble polyamic acid (PAA) was chosen to match the oriented freeze-drying method to acquire oriented pores, and the thermal imidization process from PAA to PI exactly eliminated the interface of the multilayered structure. By controlling the electro-magnetic gradient and propagation path of the incident microwaves in the MWCNT/PI and Ni/PI layers, the PI composite foam exhibited an efficient EMI SE of 55.8 dB in the X-band with extremely low reflection characteristics (R = 0.22). The asymmetric conductive network also greatly preserved the thermal insulation properties of PI. The thermal conductivity (TC) of the Ni/MWCNT/PI composite foam was as low as 0.032 W/(m K). In addition, owing to the elimination of MWCNT/PI and Ni/PI interfaces during the thermal imidization process, the composite foam showed satisfactory compressive strength. The fabricated PI composite foam could provide reliable electromagnetic protection in complex applications and withstand high temperatures, which has great potential in cutting-edge applications such as advanced aircraft.

3D graphene decorated with nickel nanoparticles: in situ synthesis, enhanced dispersibility, and absorption-dominated electromagnetic interference shielding

Utilizing the complexation of carboxyl groups with Ni(ii), 3D graphene with highly dispersed Ni NPs was achieved via laser fabrication.

Enhanced polarization via Joule heating in wood-derived carbon materials for absorption-dominated EMI shielding.

To cope with sophisticated application scenarios, carbon materials can provide opportunities for integrating multi-functionalities into superior electromagnetic interference (EMI) shielding properties. Nevertheless, carbon materials usually possess high electrical conductivity, which allows them to counteract electromagnetic waves by reflection. Moreover, the identification of factors that dominate the shielding mechanisms has typically been result-oriented, leading to a reliance on a trial-and-error approach for the development of shielding materials. Thus, it is crucial to identify the dominant factors for EMI shielding and elucidate the mechanism underlying the coordination of the balance between reflection and absorption in carbon materials. In this study, we developed a promising and viable approach to create Co@CNTs embedded in carbonized wood (CW) via chemical vapor deposition, producing Co@CNTs/CW foams. The CNTs, densely grown on the CW surface, tightly encapsulated the Co nanoparticles within them. By manipulating the Co content, the defect density and CNT length varied within the Co@CNTs. Through first-principles calculations, these variations substantially influenced the work function, charge density, and dipole moment of the Co@CNTs. Thus, defect-induced and interfacial polarizations were improved, inducing a transformation of the shielding mechanism from reflection to absorption. Regarding the Co@CNTs/CW foams, while high conductivity was essential for achieving satisfactory shielding performance, the enhanced polarization loss dominated the contribution of absorption to the overall shielding effectiveness. Taking advantage of the enhanced polarizations, the Co@CNTs/CW foams exhibited an impressive shielding effectiveness of 42.0 dB, along with an absorptivity of 0.64, which were instrumental in effectively minimizing secondary reflections. Remarkably, these as-prepared foams possessed outstanding hydrophobicity and Joule heating features with a water contact angle of 138° and a saturation temperature of 85.5 °C (2.5 V). Through the stimulation of voltage-driven Joule heating, the absorptivity of Co@CNTs/CW foams can be significantly enhanced to a range of 0.61 to 0.73, irrespective of the Co content. This research would provide a new avenue for designing carbon materials with an absorption-dominated mechanism integrated into EMI shielding performance.

Thermoplastic polyurethane foams derived from cellulose nanofibril/carbon nanotube/(Fe/C) aerogels for efficient electromagnetic interference shielding

The electromagnetic interference (EMI) shielding performance of a material can be enhanced by combining carbon and magnetic components to make the material simultaneously conductive and magnetic. In this work, a series of cellulose nanofibril (CNF)/carbon nanotube (CNT)/(Fe/C)/thermoplastic polyurethane (TPU) foams are fabricated by preforming CNF/CNT/(Fe/C) aerogels followed by combing TPU to improve the mechanical property, where Fe/C is derived from Prussian blue (PB, Fe4[Fe(CN)6]3) after pyrolysis. Consequently, the obtained aerogels and foams display electrical conductivity and magnetism. The CNF/CNT/(Fe/C)/TPU foam reaches a high EMI shielding effectiveness value of 42.2 dB at a thickness of 2 mm when the mass ratio of PB and CNT is 5:1 and the pyrolysis temperature is 650 ℃. Furthermore, the CNF/CNT/(Fe/C)/TPU foam exhibits compression resilience and hydrophobicity. This study is expected to provide a feasible strategy to acquire absorption-dominated EMI shielding materials by imparting conductivity, magnetism and porous structures to the material.

Dual cross-linked and vertically oriented MXene/polyvinyl alcohol aerogel for ultrabroadband electromagnetic interference shielding and thermal camouflage

Lightweight and porous conductive aerogels have demonstrated great potential in electromagnetic interference (EMI) shielding and thermal camouflage, while the poor mechanical properties and structural stability usually limit their applications. Herein, vertically oriented and physically/chemically dual cross-linked Ti3C2TX MXene/polyvinyl alcohol (PVA) composite aerogel is prepared by ice-templated unidirectional freezing process and subsequent glutaraldehyde (GA) treatment. GA induced covalent crosslinking leads to the significantly enhanced structural stability and mechanical strength of the resultant MXene/PVA composite aerogels, which also endows them with desirable flame retardancy. The honeycomb-like structure of the composite aerogel contributes to its good anisotropic absorption-dominated EMI shielding performance over an ultrabroadband frequency range (8.2–40 GHz) with a low MXene content of 3.81 vol%. Furthermore, the excellent thermal insulation properties and low infrared emissivity of the highly oriented arranged MXene sheets bring the composite aerogel promising applications in thermal camouflage. Therefore, the lightweight and robust MXene/PVA composite aerogel demonstrates great potential in multi-scenario applications as a high-performance multifunctional EMI shielding material.

Poly(arylene ether nitrile) composite foams with magnetically and electrically separated structures for frequency-selective electromagnetic interference shielding

With the rapid development of communication technology and modern intelligent electronic systems, the demand for frequency-selective electromagnetic interference (EMI) shielding materials has grown. In this work, poly(arylene ether nitrile) (PEN) composite foams with separated magnetic and conductive layers were prepared via delayed non-solvent induced phase separation, where the distribution of magnetic and conductive layers was designed to construct double-layer asymmetric structures and sandwich structures. Benefiting from destructive interference between electromagnetic waves (EMWs) in the magnetically and electrically separated porous structures, the double-layer asymmetric composites (M−C) exhibited outstanding absorption-dominated EMI shielding performance with favorable frequency selectivity, which did not occur in conventional double-layer composites. Specifically, M−C achieved a maximum shielding efficiency (SE) of 49.3 dB and a maximum average absorption ratio (Ar) of 93.9 %. Meanwhile, increasing the thickness of the magnetic layer of M−C can lower the characteristic frequency (fc) of the shielding peak and enhance average SE and average Ar. Moreover, M−C could show higher fc, average Ar, and average adsorption coefficient in the X-band when the incident EMWs first met with the magnetic layer, which was unavailable in frequency-selective PEN-based sandwich-structured composites. This effort offers a novel, flexible design to fabricate absorption-dominated EMI shielding materials with frequency selectivity.

Incorporating Loss Factor Modular Design for Full Ku-Band Microwave Attenuation in Double-Layered Graphene Aerogels.

The fabrication of absorption-dominant electromagnetic interference (EMI) shielding materials is a pressing priority to prevent secondary electromagnetic pollution in miniaturized electronic devices and communication systems. Meeting this goal has remained a tough challenge to keep pace with the rapid evolution of electronics due to the complex compositional and structural design and narrow operating bands. This work articulates a sound and simple strategy to precisely modulate the electrical conductivity of reduced graphene oxide (rGO), as the building block in lightweight double-layered rGO-film/rGO-aerogel/polyvinyl-alcohol (PVA) composites, for efficient microwave absorption over the entire Ku-band frequency range. These constructs reasonably comprised a porous absorption structure built from parallel rGO sheets aligned and prepared via freeze casting followed by freeze drying. The electrical conductivity and impedance of this layer were tuned by varying the annealing temperature from 400 to 800 °C, thereby adjusting the degree of reduction and the absorption characteristic. This layer was backed by a highly conductive rGO film reduced at a high temperature of 1000 °C, with a reflectivity of 97.5%. The incorporation of this film ensured high EMI shielding effectiveness of the double-layered structure through the absorption-reflection-reabsorption mechanism, consistent with the predicted values based on calculated loss factors and the input impedance of the structure. Accordingly, at an average EMI shielding effectiveness of 57.59 dB, the reflection shielding effectiveness (SER) and reflectivity (R) of the assembled composites were optimized to be as low as 0.22 dB and 0.049, respectively. This equates to approximately 99.999% shielding (SET) and ∼95% absorptivity (A) of the incident wave. This study opens new avenues for the development of lightweight (with a density as low as 15 mg/cm3) absorption-dominant EMI shielding composite materials with promising EMI shielding efficiency and potential applications in modern electronics.

Construction of alternating multilayer films with stable absorption-dominated electromagnetic shielding performance and reinforced mechanical properties via interface engineering

As an ideal material to lessen electromagnetic pollution, absorption-dominated electromagnetic interference (EMI) shielding composites still face the problems of complicated structure design and insufficient performance stability. Herein, an alternating multilayer film with stable absorption-dominated EMI shielding effectiveness (SE) and reinforced mechanical properties is fabricated by constructing hydrogen bonding between multilayers interface. When the layers increase to 4, benefiting from the construction of multilayer structure and the stronger interaction, the reflective shielding effectiveness decrease to 2.9 dB, the absorption coefficient of multilayer film increases from 0.13 to 0.52, the retention rate of EMI SE increases from 1.0 % to 97.6 % after bending 1000 cycles, and the tensile strength is enhanced from 5.7 MPa to 27.3 MPa. The calculated binding energies and the experimental results show that the interaction between Pluronic F127 anchored on the porous film and cellulose nanofibers entangled on the carbon nanotubes layer increases the interlayer interaction force and durability of EMI SE.

Absorption‐Dominant Electromagnetic Interference Shielding through Electrical Polarization and Triboelectrification in Surface‐Patterned Ferroelectric Poly[(vinylidenefluoride‐co‐trifluoroethylene)‐MXene] Composite

AbstractExtensive utilization of electronic devices and wireless equipment require human to take affirmative measures to weaken unwanted electromagnetic wave radiations. Herein, a ferroelectric poly[(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)‐MXene]‐poly(3,4‐ethylenedioxythiophene) (PEDOT) multilayered film is developed that can increase electromagnetic interference (EMI) shielding performance through electrical polarization. The MXene is encapsulated by a P(VDF‐TrFE) matrix, which inhibits oxidation, and a highly conductive MXene is created conductive network resulting in enhancement EMI shielding effectiveness (EMI SE). Furthermore, the surface pattern inducing multiple scattering and PEDOT layer contributes to the increasing absorption due to the electrically conductive PEDOT. Thanks to the electrically polarized and negatively charged P(VDF‐TrFE)‐MXene, the composite film demonstrates superior EMI SE and absolute EMI SE (SSEt) are exhibited remarkable ≈61 dB and 15230 dB cm2g−1 with high absorptivity (0.87) at thickness of 120 µm in X‐band. Additionally, P(VDF‐TrFE)‐MXene composite film is applicable to motion and thermo‐resistive sensor due to the negatively charged P(VDF‐TrFE) and thermo‐resistive property of PEDOT, respectively, for multifunctionality. This work provides a feasible avenue for flexible absorption dominant EMI shielding materials via electrical polarization with remarkable EMI shielding performance.

Fabrication of flexible polyimide/rGO composite foams and their derived carbon foams for thermal insulation and EMI shielding applications

In this work, a facile microwave-assisted foaming and thermal imidization treatment method was proposed to fabricate flexible polyimide (PI)/rGO composite foams with anisotropic pore structures. The PI/rGO composite foams (PIF/rGO) were used as the starting derivatives to prepare carbon foams that demonstrated excellent anisotropic thermal insulation and electromagnetic interference (EMI) shielding applications. The directional growth of pore structures during the foaming period resulted in the formation of aligned ellipsoidal strip-like pore structure in the horizontal direction (i.e., perpendicular to the pore growth direction), which was attributed to the escape of foaming gases such as tetrahydrofuran, methanol and H2O. The homogeneous dispersion of rGO in the PI-derived carbon skeleton endowed corresponding carbon foams with excellent mechanical and thermal stability, high thermal insulation and electrical conductivity (σ) as well as absorption dominated EMI shielding performance. The σ and EMI shielding effectiveness (SE) of carbon foams showed an increasing trend with increasing rGO content. The σ, EMI SE and specific EMI SE of the carbon foams reached up to 33.0 S/m, 49.0 dB and 8792.8 dB/(g/cm2) in the horizontal direction, respectively. Therefore, this work provided a facile strategy to fabricate lightweight and anisotropic pore structure rGO-containing PIFs and carbonized derivatives, which demonstrated promising applications in high-end industrial fields.

Thermally insulating carbon nanotubes and copper ferrite based porous polydimethylsiloxane foams for absorption-dominant electromagnetic interference shielding performance

The exponential growth of the electronic and communication industry in the last 50 years raised serious concerns about electromagnetic (EM) pollution. Consequently, suitable composite materials for electromagnetic interference (EMI) shielding have been developed to reduce EM pollution. In the present work, carbon nanotubes (CNT) and copper ferrite (CuFe2O4) nanoparticle-based porous polydimethylsiloxane (PDMS) composite foams were prepared using the baking soda template method. The PDMS foam acts as the 3-dimensional (3D) porous network, CNT gives the required conductive path and magnetic CuFe2O4 provides the necessary magnetic loss, so that the resultant foams achieved high EMI shielding through the absorption mechanism. Without the inclusion of CuFe2O4, the total EMI SE of the PDMS foam is lower than 20 dB, while various contents of the added CuFe2O4 improve the EMI SE up to 32 dB at a thickness of 3 mm. In addition, the thermal insulation properties are also reported and the resultant material shows a moderately low thermal conductivity of 0.046 W m−1 K−1. These characteristics of the composite foam highlight the strong absorption-dominated EMI shielding and thermal insulation performance, allowing it to successfully meet a wide range of applications.

Outstanding EMI shielding properties of Al2O3 reinforced with sandwiched graphene/CNTs

In this study, a novel ceramic composite with a graphene-CNTs-graphene sandwich structure is successfully synthesized. The parallel arranged graphene layers and carbon nanotubes (CNTs) possess a beneficial reflect-attenuate-reflect synergistic effect. This results in outstanding electromagnetic interference (EMI) shielding performance. The ε′ and tanδ of the sample with 5 vol% graphene and 0.5 vol% CNTs increase significantly, from 9.1 to 44 and 10−4 to 2.7, respectively. In addition to the reflection effect of graphene layers, multi-reflected electromagnetic waves are constantly attenuated by CNTs during propagation. The absorption loss (SEA) increases from nearly zero to 25 dB leading to an absorption-dominated EMI shielding effect and the highest total shielding effectiveness (SET) is 39 dB. The composites are thermal stable below 550 ℃ and the oxidation rate increases rapidly until the temperature exceeds 700 ℃. These results indicate G/CNT-Al2O3 with a sandwich structure is a promising EMI shielding material.

Heterogeneous Waterborne Polyurethane Composite with Alternating Electromagnetic Layers for Absorption-Dominated Electromagnetic Interference Shielding.

Flexible waterborne polyurethane (WPU) electromagnetic interference (EMI) composites of heterogeneous alternating multilayer structure with conductive gradient were fabricated through the layer-by-layer stacking and hot-pressing methods. Combining the synergetic electromagnetic loss and interface polarization loss formed by the selective distribution of metallized chopped polyimide fiber (PI@Ni/Cu/Ni), reduced graphene oxide (rGO), and magnetic Fe3O4 fillers, as well as multilevel electromagnetic wave propagation paths, the penetrating microwaves would undergo a particular "absorption-reflection-reabsorption" process in the composite. The asymmetric multilayer WPU composite with an absorption-dominated shielding feature exhibits a high EMI shielding effectiveness (SE) of 53.90 dB and an A value of 0.56. Moreover, the multilayer WPU composite maintains excellent integrity through repeating bending, long-time soaking, and burning tests. This work provides a viable strategy for the design of absorption-dominated EMI shielding material with controllable and stable performance that is befitting for next-generation advanced electronic products.

Absorption-dominant EMI shielding performance of multiple folded Bi2Se3/PVDF nanocomposite films

Absorption-dominant electromagnetic interference (EMI) shielding materials are promising in reducing electromagnetic radiation pollution, but their preparation processes are usually difficult and unsuitable for large-scale preparation. In this work, multiple folded Bi2Se3/PVDF nanocomposite films were fabricated by using a convenient tape-casting method and multiple folding, which can be easily extended in industrial applications. The EMI shielding effectiveness (SE) of the composite materials was investigated, which shows typical absorption-dominant behavior and can substantially reduce secondary reflections. Specifically, for the 35%(in volume) Bi2Se3/PVDF nanocomposite film, the SEA of single-layered film with a thickness of 60 μm reaches 20 dB while SER is lower than 5 dB. After folding the film into eight layers, the SEA increased to 50 dB while SER remains below 5 dB. This method provides an effective way to the fabrication of absorption-dominant electromagnetic absorption (EMA) and EMI shielding material.

Progressive conductivity modular assembled fiber reinforced polymer composites for absorption dominated ultraefficient electromagnetic interference shielding

Mechanical strong and durable fiber reinforced polymer composites (FRPC) with adjustable electromagnetic interference (EMI) shielding performance are urgently needed due to the rapid growing of electronics in civil and military fields. However, regulating the electromagnetic feature of fiber reinforced resin composites for tunable and absorption-dominated EMI shielding performance is still a great challenge due to the fixed electromagnetic properties of the continuous fabrics. Herein, an ultraefficient fiber reinforced epoxy resin EMI shielding composite with extremely low reflection, adjustable electromagnetic shielding feature and strong mechanical properties is fabricated through a facile progressively conductive fabric modular assembly. By decorating electromagnetic particles to obtain customized electromagnetic functional fiber cloths and progressively conductive modular design, this multi-layered fiber reinforced epoxy resin composites enable the arbitrary regulation of the electromagnetic wave reflection and absorption capabilities, leading to an excellent average EMI shielding effectiveness of 78.6 dB and extremely low reflectivity (R) of 0.05 in X-band frequency range. In addition, benefitting from the reasonable fabric arrangement and asymmetric layered structure, the composite also exhibits excellent mechanical properties. The tensile strength is 283.1 MPa, and the energy absorption reached 15.9 J under the impact of 20 J. Our work demonstrated that this progressive conductivity modular assembly is a reliable and efficient strategy to develop highly efficient EMI shielding FRPC composites with adjustable and absorption-dominated shielding feature, and is highly promising for applications in next-generation electronic devices.

Preparation and optimization of conductive PDMS composite foams with absorption-dominated electromagnetic interference shielding performance via silvered aramid microfibers

Electromagnetic interference (EMI) shielding materials with absorption-dominated EMI shielding mechanism can effectively annihilate electromagnetic waves (EMW) and avoid their repeated EMW pollution. However, it is difficult to achieve this goal for conductive polymer-based composites (CPC), because the interface impedance mismatch between air and CPC leads to massive reflection of EMW at the interface. Pores are beneficial to EMW penetrating into the interior of CPC and causing their multiple reflection, scattering and absorption in pores, thus endowing CPC with absorption-dominated EMI shielding characteristic. Herein, highly conductive silvered aramid microfibers (CAMF) were first synthesized via dopamine-assisted electroless deposition of silver coating on aramid microfibers (AMF), and then the conductive porous PDMS composite foams (PDMSF) with absorption-dominated EMI shielding characteristic were prepared and optimized via salt template method. As a result, PDMSF with 1.7 vol% silver content, the conductivity of PDMSF can reach 10-1 S/m, the EMI shielding efficiency (EMI SE) can reach 36.7 dB in X-band, and the average absorption ratio in EMI SE is 87%, while the density of PDMSF is only 0.28 g/cm3. The combination of lightweight, high EMI SE and absorption-dominated EMI shielding characteristic makes the porous PDMSF the latent EMI shielding materials in special constructions (e.g. military, confidential and nuclear facilities, etc.), aerospace, military equipments and transportation, etc.

Bilayer metal-organic frameworks/MXene/nanocellulose paper with electromagnetic double loss for absorption-dominated electromagnetic interference shielding

MXene has been considered an advanced electromagnetic interference (EMI) material nowadays. However, the dense MXene films result in reflection-dominated electromagnetic shielding properties. The conjugation of magnetic metal–organic frameworks (MOFs) and conductive MXene is an attractive strategy for constructing absorption-dominated EMI shielding materials. Herein, we demonstrate the carbonized zeolitic imidazolate frameworks/MXene/nanocellulose (CZMN) paper prepared by a two-step vacuum-assisted filtration (TVAF) method, which leads to the formation of bilayer structure (Lower layer as highly magnetic adsorption layer and upper layer as highly conductive reflection layer). The CZMN paper shows excellent conductivity (∼29800 S·m−1), good magnetism (13 emu·g−1), and high EMI shielding effectiveness (SE) up to 62.4 dB at 8.2 GHz with absorption-dominated EMI shielding (SEA/SET up to 75%). More importantly, the effect of bilayer structure on the absorption and reflection of the electromagnetic waves are proved by experimental results. In addition, the total electromagnetic shielding performance of the prepared bilayer CZMN paper can be improved with the increase of the conductive layer content. At the same time, the absorption ratio can remain relatively stable. These features make the prepared bilayer CZMN paper a promising candidate for advanced equipment electromagnetic protection, military technology, and stealth materials.