Electromagnetic Wave Absorption Research Articles

Water-based metamaterial absorber for temperature modulation

In this study, a transmissive all-dielectric metamaterial absorber comprising a photosensitive resin and water layers was proposed. The water layers comprised coin rings, crosses, and fan shapes. The as-obtained absorber achieved >90% absorption of electromagnetic waves within the frequency range of 18.4–41.7 GHz, and the absorption bandwidth covered the Ka-band. Because of the symmetric structure of the designed metamaterial, it was not influenced by polarization. The inherent dispersive properties of water result in a dielectric constant that varies significantly with temperature. This led to fluctuations in the absorption efficiency of the designed metamaterial to different degrees with changes in temperature. The analysis of electric and magnetic fields distributions revealed that the primary absorption physical mechanism of the designed metamaterial originated from magnetic resonances in the water layers. The proposed transmissive metamaterial absorber has potential applications in high-sensitivity thermal and temperature sensors.

3D framework MXene Ti3C2/g-C3N4/Fe3Si magneto-dielectric foam unveiling superior microwave absorption and thermal management performance

In conjunction with the swift advancement of detection technologies, the challenge persists in developing advanced stealth materials. The focus of this work is on the straightforward synthesis of a hybrid magneto-dielectric nanocomposite material composed of MXene Ti3C2/Fe3Si/g-C3N4 within a three-dimensional melamine foam framework, designed to deliver effective stealth capabilities. The high electrical conductivity and considerable permittivity of Ti3C2 have imposed limitations on its effectiveness in electromagnetic wave absorbers. In this context, the utilization of this compound in combination with substances like g-C3N4 and Fe3Si to fine-tune impedance matching and fully exploit the intrinsic properties is suggested. Furthermore, the distinctive 3D porous frameworks of the melamine foam, combined with the accordion-like structure of the MXene compound, extend and elongate paths for wave propagation to enhance energy dissipation. Through the activation of various loss mechanisms, it was possible to achieve a minimum reflection loss of −44.3 dB using a 1.5 mm thickness with an effective absorption bandwidth of 1.9 GHz. The enhancement of stealth performance was achieved through the combination of heterojunction interfaces among hybrid components and a 3D interconnected continuous path within the structure.

Synergistically magnetic and dielectric properties of two dimensional Fe3Al@PPy lamellae exhibiting broadband and strong electromagnetic wave absorption

Addressing the issue of low impedance characteristics is essential to improve the electromagnetic wave absorption performance of magnetic materials. Herein, two dimensional Fe3Al@polypyrrole (PPy) lamellae with synergistic magnetic and dielectric properties are fabricated by a mechanical alloying, ordering transformation and polymerization process, which exhibits excellent electromagnetic wave absorption performance. By carefully controlling the thickness of the PPy shell, the optimized Fe3Al@PPy lamellae show a minimum reflection loss of −45.6 dB and an effective absorption bandwidth of 9.1 GHz at a thickness of only 1.5 mm. The conformal growth of Fe3Al@PPy lamellae can induce strong interfacial polarization, dipole polarization, multiple scattering effect and magnetic loss behaviors for the attenuation of electromagnetic waves. This study demonstrates a facile strategy for the development of efficient Fe3Al@PPy composite absorbents showing great potential for practical applications.

Core–shell nanofibers/polyurethane composites obtained through electrospinning for ultra-broadband electromagnetic wave absorption

Core–shell nanofibers/polyurethane composites obtained through electrospinning for ultra-broadband electromagnetic wave absorption

Multi-dimensional, multi-interface Fe3C/carbon sheets/carbon tubes nanoarchitecture towards high-performance microwave absorption

The serious problem of electromagnetic (EM) interference brings growing demand for developing high-performance electromagnetic shielding materials. In this study, three-dimensional (3D) Fe3C/carbon/carbon tubes (Fe3C/C/CT) absorber with multi-heterointerface was prepared by a facile self-propagating followed by chemical vapor deposition (CVD) strategy. Initially, Fe3O4 nanoparticles were anchored onto carbon nanosheets through the self-propagating process. After different etching times with diluted acid, CTs with diverse dimensions and quantities were catalyzed by the modified Fe3O4 catalysts during the CVD approach and grown from the carbon sheets. Such a special nanoarchitecture, which consists of carbon sheets and carbon tubes, acts as the source of dielectric loss. Meanwhile, Fe3C nanoparticles provide magnetic loss, and the abundant interfaces facilitate synergistic electromagnetic loss. Moreover, large numbers of heterointerfaces from the unique multidimensional nanoarchitecture significantly enhance the impedance matching and produce abundant dipole polarization. Ultimately, with etching time of 30 min, the Fe3C/C/CT-30 achieves excellent electromagnetic wave (EMW) absorption property with a minimum reflection loss of −46.4 dB at 10.56 GHz with a thickness of 3.0 mm. When the thickness is 3.57 mm, the effective absorption bandwidth (EAB) can extend up to 4.48 GHz. Moreover, the practical application of the absorbers was evaluated using radar cross-section (RCS) simulation, indicating that Fe3C/C/CT-30 achieves a maximum RCS reduction value of 58 dBm2. The multi-dimensional and multi-heterointerface absorber presented in this work might offer valuable insights for optimizing electromagnetic absorbers.

Dual-type heterogeneous interface design enables customized tuning of dielectric parameters of multifunctional, lightweight, flexible absorbers for broadband electromagnetic wave absorption

With the boom in 5 G technology comes widespread concern about electromagnetic (EM) interference and the safe use of electronics. Conventional electromagnetic wave (EMW) absorbing materials in the form of coatings are often inflexible and poorly adapted to different EM environments. Diversified application scenarios require EMW absorbing materials with a wide absorption band and multifunctional properties. Herein, the frequency dispersion (FD) requirements of the EM parameters of the broadband absorber in different frequency bands are determined by EM simulation. Based on the dominant role of interface polarization on FD, we designed different types of heterogeneous interfaces to meet the needs of strong FD in the low-frequency band and weak FD in the high-frequency band. Through the optimized design of heterogeneous interfaces, CC@ZnO/ZnS composites exhibit excellent EMW absorption performance, achieving flexible, ultrathin (2.1 mm), ultralight (10 wt%), and broadband (7.02 GHz), which is superior to EMW absorbing materials of similar compositions. In addition, the composites have good piezoelectric/inverse piezoelectric properties, which can convert EM energy into mechanical energy while absorbing EMW, thus realizing applications in multifunctional fields such as sensors, controllers and energy converters. More noteworthy is the sample's highly efficient thermal insulation, flame retardant and anti-frosting properties, demonstrating important advantages for service in harsh environments. Therefore, CC@ZnO/ZnS composites not only have good practical application characteristics while realizing broadband absorption, but also are expected to achieve multifunctional applications in different fields.

Apple Tree Root‐Derived Biochar/Iron Oxide Triphasic Nanocomposite for Wastewater Treatment and Microwave Absorption

AbstractIn this work, two major sources of pollution: (1) Water pollution due to heavy metals, and (2) Electromagnetic wave (EMW) pollution, often regarded as the fourth category of pollution (after air, water, and soil pollution) are addressed. A unique bio‐based triphasic nanocomposite (Fe3O4/α‐Fe2O3/carbon) is synthesized and its superior properties are demonstrated to address both types of environmental pollution. The nanocomposite, derived from lightweight apple tree roots, is used for Pb (II) ion removal from aqueous solutions via adsorption and magnetic separation. The biomass‐derived highly porous biochar decorated with iron‐oxide showed adsorption efficiency of nearly 100% and corresponding capacity of 149 mg.g−1 under optimal conditions for initial Pb (II) concentration of 50 mg.L−1. Furthermore, a remarkable adsorption capacity of 731 mg.g−1 is achieved using lower amount of the adsorbent for a slightly lower efficiency (97%). In addition, the mesoporous composite showed excellent EMW absorption efficiency with effective absorption bandwidth of 7.8 GHz and reflection loss of −61.7 dB, arising from very good impedance matching, and high dielectric and magnetic losses. This work establishes the multifunctional properties of the synthesized composite, and addresses the UN Sustainable Development Goal (SDG) 6 (Clean water and sanitation) and SDG 13 (Climate action, including pollution management).

Improved Electromagnetic Interference Shielding Efficiency of PVDF/rGO/AgNW Composites via Low-Pressure Compression Molding and AgNW-Backfilling Strategy.

Silver nanowires (AgNWs) have excellent electrical conductivity and nano-sized effects and have been widely used as a high-performance electromagnetic shielding material. However, silver nanowires have poor mechanical properties and are prone to fracture during the preparation of composite materials. In this study, PVDF/rGO/AgNW composites with a segregated structure were prepared using low-pressure compression molding and the AgNW-backfilling process. The low-pressure compression of the composite significantly improves its electromagnetic shielding performance because the low-pressure process can maintain the AgNWs' integrity. The backfilled AgNWs played a vital role in increasing the path of electromagnetic wave propagation and the absorption of electromagnetic waves. The backfilled amount of AgNWs was only 1 wt%, which increased the composite material's conductivity by one order of magnitude. The total electromagnetic interference shielding (SET) of the composite materials increased by 23.3% from 24.88 dB to 30.67 dB. The absorption contribution (SEA/SET) increased from 84.2% to 92.8%, significantly improving the electromagnetic interference shielding and the absorption contribution of the AgNWs in the composites. This was attributed to the backfilling of the porous structure by the AgNWs, which promoted multiple reflections and enhanced the absorption contribution.

Multifunctional SiC nanowire aerogels with efficient electromagnetic wave absorption for applications in complex environments

In the digital age, with rapid advancements in electromagnetic (EM) technology, electromagnetic pollution has emerged as a significant concern. Traditional electromagnetic wave (EMW) absorption materials, however, are constrained by their limited application range, inadequate physicochemical stability, and inferior mechanical strength, hindering their further development and application. Consequently, there exists a demand for an EMW absorber that not only incorporates multiple functionalities but also retains essential physicochemical characteristics. In this context, this study introduces an ultralight (∼12 mg cm⁻³) and multifunctional SiC nanowire aerogel (SNWA), synthesized through a direct chemical vapor deposition (CVD) technique. The resulting SNWA demonstrates exceptional elasticity, outstanding mechanical durability, and high thermal stability at increased temperatures. Additionally, the enhanced SNWA shows improved hydrophobic properties, facilitating its use in highly humid conditions. The SNWA material also presents remarkable EMW absorption efficiency, with a minimum reflection loss of −50.6 dB and an effective absorption bandwidth of up to 7.7 GHz. The straightforward CVD synthesis and surface modification technique ensure the SNWA's durable and efficient performance in demanding environments.

Construction of rGO/MOF-derived CNTs aerogel with multiple losses for multi-functional efficient electromagnetic wave absorber

Graphene aerogels have attracted increasing attention in electromagnetic wave (EMW) absorption due to their ultra-low density and excellent dielectric performance. However, pure graphene aerogels have limited loss mechanisms, and it remains a challenge to introduce multiple loss mechanisms while maintaining lightweight. Here, reduced graphene oxide/metal organic framework (MOF)-derived carbon nanotubes (rGO/MD@CNTs) aerogels are successfully constructed by uniformly compositing GO and MOF particles by hydrothermal treatment and further in-situ growing CNTs by chemical vapour deposition method. GO and MOF particles form strong bonding sites due to their interaction to construct the aerogel with excellent mechanical property, while magnetic loss is also introduced. The MOF-catalyzed CNTs not only contribute to the formation of interface and dipole polarizations, but also effectively regulate the conductivity to improve impedance matching. rGO/MD@CNTs aerogel integrates multiple losses and optimal impedance matching. With a filling ratio of 6 wt%, the aerogel exhibits an excellent reflection loss of −51.6 dB and a wide effective absorption bandwidth of 5.9 GHz. In addition, the aerogel shows good thermal stability and antifreeze properties. Therefore, this work provides an effective strategy for obtaining the aerogel with multiple losses for efficient EMW absorption, demonstrating the potential applications of rGO/MD@CNTs aerogel in complex environments.

High-entropy TiVNbMoC3Tx MXene hybrid with balanced dielectric-magnetic loss for high-efficient electromagnetic wave absorption with environmental stability

With the advent of the 5G era, there is a growing demand for electromagnetic wave (EMW) absorbers that offer both efficient absorption and improved environmental stability. Transition metal carbides/carbonitrides (MXene), with their atomic-layered structures and high electrical conductivity, offer substantial potential for crafting efficient electromagnetic functional materials. Yet, enhancing the antioxidant capabilities and addressing the poor loss mechanisms of traditional MXene absorbers remain challenging tasks. In this context, a TiVNbMoC3Tx high-entropy MXene (HE-MXene) and its magnetic hybrids were synthesized for the first time. The unique multicomponent structure of high-entropy MXene reduces grain boundary formation, thereby slowing the progression of oxidation reactions. The incorporation of magnetic nanoparticles induces interface polarization loss or strong magnetic coupling, thereby enhancing EMW attenuation. These magnetic HE-MXene hybrids demonstrated a minimum reflection loss of −57.59 dB at a matching thickness of 1.46 mm and an effective absorption bandwidth (EAB) of 4.72 GHz at a thickness of 1.53 mm. Furthermore, the magnetic hybrids also exhibited outstanding oxidation and electrochemical corrosion resistance. This research provides valuable theoretical insights for the development of electromagnetic composites within high entropy (HE) systems, showcasing significant potential for long-term applications.

Microstructure Design and Dimensional Engineering of Nanomaterials for Electromagnetic Wave Absorption and Thermal Insulation.

Multifunctional materials integrated with electromagnetic wave absorption (EWA), thermal insulation, and lightweight properties are urgently indispensable for the flourishing advancement of space technology, which can simultaneously prevent electromagnetic detection and resist aerodynamic heating. To achieve excellent synergistic EWA and thermal insulation performance, the elaborate regulate the microstructure and dimension of nanomaterials has emerged as a captivating research direction. However, comprehending the structure-property relationships between microstructure, electromagnetic response, and thermal insulation mechanisms remains a significant challenge. Herein, a comprehensive perspective focuses on the microstructure design encompassing various dimensions of nanomaterials, providing a comprehensive understanding of correlations among structure, EWA, and thermal insulation. First, the cutting-edge mechanisms of EWA and thermal insulation are elaborated, followed by the relationship between the dimensions of nanomaterials. Moreover, the synergistic design methods of EWA and thermal insulation are explored. Lastly, this review summarizes the corresponding shortcomings and issues of current EWA-integrated thermal insulation materials and proposes breakthrough directions for the creation of materials with superior performance.

Phase Engineering in a Twin‐Phase β/γ‐MoCx Lightweight Nanoflower with Matched Fermi Level for Enhancing Electron Transport Across the Polarized Interfaces in Electromagnetic Wave Attenuation

AbstractThe phase engineering of the polarization interface is of great significance in modifying dielectric loss in electromagnetic wave (EMW) attenuation process, but hard to conduct in a complex hybrid system. Herein, a twin‐phase of β/γ‐MoCx@CN with matched Fermi level and closed work function properties in lightweight MoCx nanoflower is constructed, facilitating electron transport withdraw enhanced conductivity and polarization. Moreover, the EMW multiple dissipations among the β/γ‐MoCx@CN polarization interface is promoted, displaying better matched impedance. It delivered a remarkable minimum reflection loss (RLmin) of −74.2 dB at the thickness of 1.5 mm, which far beyond the single phased β‐MoCx@CN, γ‐MoCx@CN and reported MoCx‐based EMW absorbers. The radar cross‐section (RCS) map of β/γ‐MoCx@CN is simulated, showing a brilliant maximum reduction value of 13.6 dB m2 at the theta angle of 30°. This work presented an excellent sample of atomic‐level manipulation of interfacial polarization in dielectric MoCx EMW absorption materials.

Metal-organic framework-derived hierarchical Ag/Ti3C2Tx/Co/C nanocomposite for enhanced electromagnetic wave absorption

The microwave absorption (MA) performance of 2D Ti3C2Tx is significantly restricted due to its lack of magnetic loss capacity and mismatched electromagnetic impedance. The Ag/Ti3C2Tx/Co/C (ATCC) structure, based on a unique 2D layered Ti3C2Tx, has shown exceptional electromagnetic wave absorption (EWA) properties. The addition of a silver nanoparticles enhances the polarization effect and conductance loss of Ti3C2Tx. By incorporating ZIF-67 with varying Co content, nanocomposite heterostructures and interfaces are formed in Ag/Ti3C2Tx. Moreover, the carbon source of organic ligand and the 3D network structure of Ti3C2Tx provide additional electronic transition channels and improve conductive loss. This modification results in non-uniform interfaces between Ti3C2Tx and metal nanoparticles, leading to electron accumulation and the formation of a micro-capacitance structure that generates interface polarization. Eddy current loss and magnetic loss from metal nanoparticles further enhance EWA properties. This study envisions a novel strategy for developing efficient Ti3C2Tx-based microwave absorbers modified with metal nanoparticles.

Engineering of N doped carbon@FeCo alloy hollow spheres: Remarkable mid-frequency electromagnetic wave absorption performance exhibited by unique porous and wrinkled surface structure

The modulation of the shape and design of microstructures plays a crucial role in enhancing the efficient absorption of electromagnetic waves in absorbers. The electromagnetic parameters and scattering effects of these materials are directly influenced by their morphological characteristics. In this study, polystyrene microspheres were used as templates for a two-step in-situ growth process: Initially, Fe₃O₄ was coated onto the surfaces of these microspheres, followed by the in-situ growth of Fe-Co Prussian blue analogs. The rational design of electrical parameters during the conversion process was calculated and analyzed using Density Functional Theory. The precursor was calcined at various temperatures to generate a unique porous wrinkled surface hollow nanostructure. This nanostructure not only facilitates multiple reflections and scattering of incident electromagnetic waves but also promotes the occurrence of multiple interface polarizations. Doping with nitrogen and oxygen elements introduced abundant dipole polarization, thereby enhancing the electromagnetic wave attenuation capability of the composite material. The Fe3O4@PBA composite material synthesized at 600°C achieved a minimum reflection loss of −57.01 dB and a maximum effective absorption bandwidth of 4.58 GHz (7.52–12.1 GHz) at a thickness of 4 mm, covering nearly the entire X-band. This method provides a means to enhance magnetic loss by temperature adjustment to control the magnetic components in composite materials, providing a systematic approach to designing the microstructure of materials used for absorbing electromagnetic waves.

Magnetic carbon composites derived from biomass with excellent microwave absorption capacity

It is well known that magnetic iron oxide (Fe3O4) and carbon-based materials are good microwave absorbing materials. However, the frequency bands in which Fe3O4 absorbs electromagnetic waves are usually concentrated in the low-frequency region, whereas carbon materials are in the high-frequency region. Therefore, this study aims to deal with the limitation of the absorption bands of these two substances. In this work, this Fe3O4/C composite with high performance microwave absorption was successfully adoption of hydrothermal-calcination process using mangosteen shells as a biomass carbon material, and with a thickness of 1.97 mm, the optimal reflection loss of the sample can reach −67.49 dB, and the frequency band that can be absorbed is 4.32 GHz. The interface polarization, dipolar polarization and eddy current loss in Fe3O4 and carbon materials produce synergistic effects, and the porous conductive network increases the electromagnetic wave transmission path and generates conductive losses, which results in composites with excellent electromagnetic wave absorption properties. The findings indicated that a composite compound of Fe3O4 and carbon-based material was successfully synthesized by hydrothermal method and obtained a materials with outstanding electromagnetic wave absorption properties and high absorption bandwidth.

Heterogeneous interface engineering of spindle shaped Fe/C through optimizing impedance response for enhanced microwave absorption and thermal conductivity

Heterogeneous interface design is pivotal in creating lightweight, broadband, and high-efficiency electromagnetic wave (EMW) absorption materials. These materials enhance wave absorption by adaptively matching impedance. In this study, spindle-shaped Fe/C nanocomposites with heterogeneous interfaces and diverse surface microtopographies were synthesized by calcining iron-supported metal-organic frameworks (MOFs). During controlled pyrolysis, Fe3+ was reduced by carbon and conversely induced the graphitization of carbon, which is essential for the distribution and appearance of Fe and graphitized carbon as well as for modulating impedance matching. The porous structure of the Fe/C composites and the polarization loss and ferromagnetic resonance from the defective carbon and Fe magnetic particles synergistically enhance the wave absorption performance. The Fe/C-700 nanocomposite achieves a reflection loss (RL) of −55.9 dB at 12.48 GHz with an effective absorption bandwidth (EAB, RL ≤ −10 dB) of 3.9 GHz at 1.8 mm. The Fe/C-900 nanocomposite demonstrates a significant RL of −63.5 dB at 15.8 GHz with an EAB of 4.4 GHz between 13.6 GHz and 18 GHz at 1.5 mm, and an EAB of 5.5 GHz at 1.63 mm. These improvements are attributed to the impedance matching facilitated by the introduction of Fe magnetic particles and graphitized carbon. Additionally, the thermal conduction pathway formed among the Fe/C nanocomposites significantly enhances the thermal conductivity to 0.502 W m−1 K−1. Thus, this work offers a novel approach to the design of advanced wave-absorbing and thermal conductive materials by optimizing impedance through heterogeneous interfaces.

Effect of entropy evolution on electromagnetic response mechanism of carbon-coated medium- and high-entropy oxides

Metal oxides have attracted much attention due to their potential in electromagnetic wave absorption. However, the inherent energy dissipation capabilities of low-entropy metal oxides pose challenges in designing materials with optimal entropy levels. The regulation of entropy structure is anticipated to facilitate the development of novel electromagnetic functional materials featuring abundant active sites, adjustable specific surface area, stable crystal structure, unique geometric compatibility, and distinctive electronic structure. This study compared the electromagnetic loss performance of low, medium, and high entropy metal oxides in carbon matrices. As entropy increases, the number of phases expands, leading to enhanced interface polarization losses and improved impedance matching. However, further increases in entropy result in performance decline due to lattice distortions and mismatches in dielectric constant and magnetic permeability. Experimental data and theoretical analysis reveal that performance enhancement in medium-to high-entropy metal oxides is attributed to their unique morphology and the synergistic effects of multiple metal components, which enhance interfacial and defect polarization mechanisms. Heterogeneous interfaces and lattice defects provide additional polarization sites, aiding in the conversion of electromagnetic energy into heat. The presence of intermediate phases effectively absorbs and dissipates electromagnetic waves, thereby enhancing the overall absorption capability.

High electromagnetic wave absorption and thermal conductivity of vertically oriented boron nitride/carbonyl iron/silicone rubber composites

The vertically oriented boron nitride/carbonyl iron/silicone rubber composites with tunable excellent electromagnetic wave absorption and thermal conductivity have been successfully prepared by a high-temperature molding method. Results show that the composites exhibit a maximum effective absorption band (EABmax) of 7.55 GHz with a thickness of 1.7 mm and a minimum reflection loss (RLmin) of −56.82 dB at 15.6 GHz (1.5 mm). Moreover, the composites have an excellent thermal conductivity with a maximum thermal conductivity of 4.023 W/(m·K), which is 8 times higher than that of the wave absorption material (80 wt% carbonyl iron/silicone rubber composites in this work). This work provides an inexpensive and simple effective strategy for designing advanced multifunctional composites with potential future applications in modern electronics.

Defect-rich carbon nanosheets derived from p(C3O2)x for electromagnetic wave absorption applications

Defect modulation strategies have been shown to be an effective way to design efficient EMW absorbing materials, but the coexistence of multiple loss mechanisms due to the complexity of the existing models makes it difficult to elucidate the mechanism by which defect-induced dielectric losses dominate. In this work, p(C3O2)x is applied for the first time in the field of EMW absorption and the concentration of defects in the sample is controlled by changing the pyrolysis temperature. In addition, the unique molecular structure of p(C3O2)x enables the prepared samples to completely eliminate the interference of interfacial polarization and magnetic loss on EMW dissipation. The results show that the dielectric loss induced by defects significantly enhances the EMW absorption performance as the concentration of defects increases, but excessive defects lead to a sudden drop in the conductivity of the sample and reduce the EMW absorption performance. In which, the RLmin of OC-800 can reach −51.0 dB, and the EAB of OC-900 can go up to 5.6 GHz at only 1.6 mm. Finally, CST simulation verified the potential application of the prepared absorber in real scenarios. This work has improved the theoretical basis of the effect of defect-induced dielectric loss on EMW absorbing properties, and the simple synthetic raw materials and routes have made the industrialized production of highly efficient EMW absorbing materials possible.