Electromagnetic Wave Absorption Materials Research Articles

2D/1D Hierarchical Hollow NiO@PPy Composites with Tunable Dielectric Properties for Enhanced Electromagnetic Wave Absorption.

The development of diverse microstructures has substantially contributed to recent progress in high-performance electromagnetic wave (EMW) absorption materials, providing a versatile platform for the modulation of absorption properties. Exploring multidimensional microstructures and developing tailored and gentle strategies for their precise optimization can substantially address the current challenges posed by relatively unclear underlying mechanisms. Here, a series of 2D/1D heterogeneous NiO@PPy composites featuring hollow hierarchical microstructures are successfully synthesized using a straightforward strategy combining sacrificial templating with chemical oxidative polymerization. This strategy offers a facile and effective approach to fine-tune the microstructure by adjusting the thickness of the polypyrrole (PPy) coating. This enables the continuous optimization of the dielectric properties and specific microstructures to maximize EMW absorption. Remarkably, the optimized 2D/1D hierarchical hollow NiO@PPy composite demonstrates an ultrathin thickness of 2.3 mm, a wide effective absorption band spanning 5.89 GHz, and a strong absorption intensity of -71.65 dB at a minimal loading of only 10 wt.%. The proposed mild and controllable preparation strategy not only provides insights for further tailoring the optimal dielectric properties of specific structures to enhance the absorption capacity, but also enriches the exploration of the underlying absorption mechanisms from the perspective of microstructure regulation.

Bamboo-Inspired Hierarchically Hollow Aerogel MXene Fibers with Ultrafast Ionic Channels and Multiple Electromagnetic Wave Attenuation Routes Toward High-Performance Supercapacitors and Microwave Absorption.

2D materials feature large specific surface areas and abundant active sites, showing great potential in energy storage and conversion. However, the dense, stacked structure severely restricts its practical application. Inspired by the structure of bamboo in nature, hollow interior and porous exterior wall, hollow MXene aerogel fiber (HA-Ti3C2TX fiber) is proposed. Owing to continuous porous microstructure and optimized hollow cavity, this fiber possesses large accessible area to ions and abundant structural defects, leading to a fast charge transfer kinetics and high faradic activity. Consequently, the HA-Ti3C2TX fiber exhibits exceptional gravimetric capacitance of 355 F g-1. Besides, the solid-state asymmetric fiber-shaped supercapacitors (FSCs) display a high capacitance of 276 F g-1 and energy density of 9.58 Wh kg-1. Additionally, the HA-Ti3C2TX fiber delivers outstanding electromagnetic wave (EMW) absorption performance with a minimum reflection loss of -52.39 dB and the effective absorption bandwidth up to 4.6 GHz, which is attributed to multiple reflection paths, strong dielectric loss from this hollow and porous structure. This novel design of hollow fiber provides a new reference for the construction of advanced fibers for energy storage and EMW absorption materials.

Efficient S-band Electromagnetic Wave Absorption in Hierarchically Hollow CoFe2O4/C Nanocomposites Modified by ZIF-67 Derivatives

Designing electromagnetic wave-absorbing materials (EWAM) with high-efficiency absorption in the S-band (2-4 GHz) is crucial for applications like radar systems, satellite communications, and wireless technologies. However, achieving such absorbing materials...

Optimizing electromagnetic wave absorption in electrospun carbon-based fibers through dielectric and magnetic component modulation

Electrospinning technology-driven carbon fiber provides a promising approach for fabricating high-performance electromagnetic wave-absorbing materials.

H-CoFe2O4/Ti3C2Tx/BNC Hybrid Aerogels with Modulation Impedance Matching for Electromagnetic Wave Absorption and Health Monitoring.

Given the limitations of single-function electromagnetic wave-absorbing materials (EWAMs) in meeting the evolving demands of complex usage scenarios, there is a growing need for structure-function integrated composites that offer a combination of microwave absorption, human monitoring, and thermal insulation. This study successfully synthesized two-dimensional (2D) Ti3C2Tx MXene via selective etching of Al from the Ti3AlC2 MAX phase. By introducing MXene into a composite of hydroxylated CoFe2O4 nanoparticles (h-CFO NPs) and bacterial nanocellulose (BNC) to modulate the electromagnetic performance of the EWAMs. The optimized electromagnetic parameters and three-dimensional (3D) porous structure achieve enhanced impedance matching of the wave absorber. The h-CFO/BNC/MXene (h-CFO@CM73) hybrid aerogel demonstrates superior electromagnetic wave absorption (EMWA) performance due to the synergistic effects of conductive loss, magnetic loss, interfacial polarization, and dipole polarization, where a minimum reflection loss (RLmin) of -32.66 dB at a thickness of 4.5 mm, an effective absorption bandwidth (EAB) of 10.70 GHz within the test range, and an EMWA efficiency reaching up to 99.92% were realized. Moreover, the hybrid aerogel presents sensitive sensing capabilities, detecting human joint movements, breathing, and vocalizations. Additionally, the developed hybrid aerogels exhibit commendable thermal insulation and infrared camouflage properties. Consequently, the fabricated multifunctional hybrid aerogel has excellent potential for monitoring care of infants, children, and pregnant women.

Effective Multi-Layered Structure Design with Carbon-Based Hybrid Polymer Nanocomposites Using Evolutionary Algorithms

Electromagnetic wave-absorbing materials (EMAMs) and structures are crucial in aerospace and electronic communications due to their ability to absorb electromagnetic waves. The development of materials that are lightweight, sustainable, and cost-effective, exhibiting high-performance absorption across a broad frequency spectrum, is therefore important. However, homogeneous electromagnetic absorbing materials require assistance to meet all these criteria. Therefore, developing multi-layer absorbing coatings is essential for enhancing performance. The present study uses 21 different composites of varying weight fractions of polypropylene, graphene nanoplatelets, and multiwall carbon nanotubes nanocomposites to develop multi-layer absorbing materials and optimize their performance. These multi-layer carbon polymer nanocomposites were meticulously constructed using evolutionary algorithms like Non-sorted Genetic Algorithm-II and Particle Swarm Optimization to achieve ultra-broadband electromagnetic wave absorption capabilities. Among the designed electromagnetic absorbing materials, a two-layer model, i.e., 1.5 wt% MWCNT/PP/epoxy with a thickness of 1.052 mm and 2.7% GNP/PP/epoxy with a thickness of 4.456 mm totaling 5.506 mm, was identified as optimal using NSGA-II. The structure has exhibited exceptional absorption performance with a minimum reflection loss of −21 dB and a qualified bandwidth extending to 4.2 GHz. PSO validated and optimized this structure, confirming NSGA-II’s efficiency and effectiveness in quickly obtaining optimal solutions. This broadband absorber design combines the structure design and material functioning through additive manufacturing, allowing it to absorb well over a wide frequency range.

1D Magnetic Nickel‐Carbon Matrix Nanotube Composites Derived from Hydrogen‐Bonded Organic Frameworks and Metal–Organic Frameworks for Electromagnetic Wave Absorption

AbstractHydrogen‐bonded organic frameworks (HOFs) and metal–organic frameworks (MOFs) emerge as promising materials for electromagnetic wave (EMW) absorption, due to their high specific surface area and readily modifiable characteristics. In this study, 1D magnetic nickel‐carbon matrix nanotube composites (Ni‐HMCNTs) from a mixture of HOFs and MOFs (Ni‐HMNTs) for EMW absorption are synthesized. The Ni‐HMNTs are achieved via a one‐step method involving a single‐pot solvothermal reaction among melamine, trimeric acid, and nickel nitrate. This process involves a HOF‐to‐MOF transformation, characterized by the penetration of Ni ions into the HOF structure via a competitive coordination reaction, resulting in the hollow structure of Ni‐HMNTs. Subsequent calcination of Ni‐HMNTs yields Ni‐HMCNTs optimized for EMW absorption. Remarkably, with a filling degree of only 10 wt%, 1.2 Ni‐HMCNTs‐700 (heat‐treated at 700 °C) exhibits exceptional EMW absorption properties, with a minimum reflection loss (RLmin) value of −50.4 dB and a maximum effective absorption bandwidth (EAB) of 7.32 GHz (10.64–17.96 GHz). These findings pave the way for further exploration of magnetically modified HOFs/MOFs for EMW applications.

Simple preparation of high-temperature resistant BN-coated BCN fiber with a porous surface to enhance microwave absorption

Addressing this issue has become a significant concern in current research to enhance the performance and thermal stability of carbon electromagnetic wave (EMW) absorption materials. This study synthesizes BN-coated BCN fibers through wet spinning and precursor pyrolysis routes. A porous structure is incorporated between the BN and BCN fiber substrates to enhance EMW absorption performance. The results show that the BN-coated BCN fibers with a porous surface exhibit superior EMW absorption performance with the minimum reflection loss (RLmin) of -46.79 dB and the effective absorption bandwidth (EAB) of 5.5 GHz at 2mm, almost covering the Ku band. This straightforward co-doping and cost-effective synthesis strategy offers a novel design approach for preparing EMW absorption materials.

Phenolic multiple kinetics-dynamics and discrete crystallization thermodynamics in amorphous carbon nanostructures for electromagnetic wave absorption

The lack of a chemical platform with high spatial dimensional diversity, coupled with the elusive multi-scale amorphous physics, significantly hinder advancements in amorphous electromagnetic wave absorption (EWA) materials. Herein, we present a synergistic engineering of phenolic multiple kinetic dynamics and discrete crystallization thermodynamics, to elucidate the origin of the dielectric properties in amorphous carbon and the cascade effect during EWA. Leveraging the scalability of phenolic synthesis, we design dozens of morphologies from the bottom up and combine with in-situ pyrolysis to establish a nanomaterial ecosystem of hundreds of amorphous carbon materials. Based on controlled discrete crystallization, nano-curvature regulation of spatial inversion symmetry-breaking structures, and surface electric field enhancement from multi-shell structures, the multi-scale charge imbalance triggers intense polarization. Both experiments and theories show that each scale is essential, which collectively drives broadband absorption (8.46 GHz) and efficient dissipation (−54.77 dB) of EWA performance. Our work on the amorphous nanostructure platform and the cascade effect can contribute to uncovering the missing pieces in amorphous physics and EWA research.

Multifunctional Anisotropic Aerogels for Intelligent Electromagnetic Wave Absorption

AbstractThe rapidly developing modern society has higher requirements for intelligent electromagnetic wave absorbing (EMA) materials than ever before. Herein, lightweight, multifunctional metal‐free carbon‐based aerogels (RCPs) with a longitudinal honeycomb porous framework and a transverse neatly layered structure are obtained by heat‐treating graphene oxide/oxidized carbon nanotubes/hexachlorocyclotriphosphazene complex to simultaneously achieve the tunable EMA, flame retardancy, and thermal insulation. The anisotropic structure ensures the tunable properties of the carbon aerogels along with tilt angles according to environmental needs. The honeycomb porous structure effectively promotes multiple reflections and scatterings of electromagnetic waves compared with the layered structure, maximizing the penetration inside the material and thus a high EMA performance. The optimized R10C2P‐4 exhibits a minimum reflection loss in the longitudinal direction of−61.5 dB, while the value is as low as −22.4 dB in the transverse direction. Furthermore, the porous structure adequately inhibits the spread of heat, accompanied by the phosphorus species induced by hexachlorocyclotriphosphazene pyrolysis, endowing a good flame retardancy and thermal insulation with a low thermal conductivity of 20.6 mW m−1 K−1 in the longitudinal direction, rather than the transverse direction. This work provides an ingenious insight into the design of multifunctional EMA materials, adapting flexibly to various application requirements.

Hierarchically structured composite with 3D interlocking architecture for multi-band defense

The development of high-performance electromagnetic wave absorbing (EMWA) materials for radar stealth applications poses a persistent challenge, particularly when addressing the demanding requirements of diverse frequency bands in increasingly complex and dynamic environments. Precisely tailoring the microstructure of these materials presents a powerful strategy for achieving multifunctional integration and unlocking new possibilities for practical applications. In this work, we present a novel hierarchically structured composite foam with 3D interlocking architecture, fabricated through a straightforward foaming and calcination process. It features a unique dual three-dimensional continuous phase structure that facilitates the formation of an efficient conductive network, promoting free electron mobility and enhancing polarization loss. The composite demonstrates exceptional EMWA performance, exhibiting a wide effective absorption bandwidth (EAB) of 6.1 GHz and a remarkable absorption intensity of -63.2 dB along with RCS reduction value up to 28.7 dB m2. Furthermore, the composite illustrated strong infrared stealth properties and efficient photothermal conversion abilities. When heated to 56°C, its surface temperature only increased by 4°C in 10 minutes. Under direct sunlight, its surface temperature rose from 21°C to 71°C in just 6 minutes. Lightweight, flexible, and adaptable to diverse environmental conditions, the HCC composite holds significant promise as a multi-spectrum defense material. Its versatility makes it an ideal candidate for integration into a wide range of equipment, clothing, and wearable technologies, offering advanced capabilities for radar, infrared, and visible light signature reduction.

In-situ Construction of Petal-liked porous Co coating layers for electromagnetic wave absorption materials with rich interface-polarization

With the rapid advancements in 5G and communication technology, electromagnetic wave (EMW) absorption materials play a crucial role in reducing interference, enhancing the efficiency and stability of communication equipment, and minimizing maintenance requirements. However, the challenge remains in effectively utilizing cost-effective raw materials with simple synthesis conditions to achieve highly consistent product quality and superior EWM absorption performance. This study employs carbon nanofibers (CNFs) derived from polyacrylonitrile (PAN) as substrates and utilizes electrodeposition technology to create a composite material that exhibits both magnetic and dielectric properties. The results show that the petal-like porous Co composite CNFs (Co/CNFs) demonstrates excellent impedance matching and significant EMW absorption capabilities, which can be attributed to synergistic microstructural effects and multiple loss mechanisms. At a filling ratio of 20 wt% and a thickness of 1.8 mm, the Co/CNFs achieves a minimum reflection loss of −45 dB, extending the effective absorption bandwidth to 4.6 GHz. Performance assessment through power loss density (PLD) and radar cross-section (RCS) simulations evaluates the material’s capabilities, confirming the enhanced performance of Co/CNFs compared to the perfect electrical conductor (PEC). This efficient preparation method holds substantial potential for practical applications and serves as a comprehensive guide for achieving a balance between high performance, efficiency, and cost-advantages.

Core Double-Shell FeCo@SiO2@PPy Nanocomposites for Tunable and Broadband Electromagnetic Wave Absorption

Electromagnetic wave absorption materials are essential for dealing with military stealth and electromagnetic pollution. However, challenges remain in regards to material stability and achieving broadband absorption. Constructing magnetic-dielectric core-shell structural composites with good morphology is one of the effective strategies to realize high-performance electromagnetic wave absorption. Herein, FeCo@SiO2@polypyrrole (PPy) core double-shell nanocomposite with uniform shell thicknesses is synthesized by environmentally friendly polyol method, sol-gel method and in-situ oxidative polymerization method. FeCo@SiO2@PPy nanocomposites with different PPy shell thicknesses were synthesized, and tunable electromagnetic wave absorption had been achieved. The reasonable combination of magnetic and dielectric components and the design of core double-shell structure optimized impedance matching and attenuation characteristics, resulting in strong and broadband electromagnetic wave absorption (minimum reflection loss: -62.7 dB, effective absorption bandwidth: 7.0 GHz). This work could initiate a new insight into the design and modulation of advanced electromagnetic wave absorption materials with strong and broadband absorption properties.

Dual-gradient Mo2C-decorated rGO aerogels for enhanced electromagnetic wave absorption

The lightweight, strong absorption, non-resin, and high chemical and thermal stability of electromagnetic wave absorption materials used in space vehicles are required in the harsh space environments. Herein, a light weight and effective microwave-absorbing material is constructed by synthesizing carbide-modified reduced graphene oxide (rGO) aerogels, gradient design and carbonization. The as-prepared aerogel material consists of molybdenum carbide (MC) and rGO, and displays hollow structures with multi-wall rGO layers. The MC structure in the MC/rGO aerogel is regulated by controlling the amount of Mo source, and the dual gradient structure composed of MC/rGO material is designed and optimized by CST Microwave Studio. Compared with MC/rGO aerogel, the dual-gradient MC/rGO (DG-MC/rGO) aerogel exhibits superior impedance matching and significantly enhanced microwave absorption performance. The minimum reflection loss (-62.4 dB) is reduced by 64.6 %, and the effective absorption bandwidth (5.7 GHz) is increased by over 35.7 % at a thickness of 2.2 mm. The remarkable improvement of microwave absorption is attributed to the synergy effect of well-dispersed molybdenum carbide nanoparticles and the components/structures gradients of DG-MC/rGO material. This novel lightweight material has promising applications in electromagnetic wave absorption fields.

Two-Dimensional CNPs Superstructures Derived from Metal-Organic Frameworks for Electromagnetic Wave Absorption.

Carbon nanoparticles (CNPs) derived from metal-organic frameworks (ZIF-8) are synthesized, which are further self-assembled into mono- or bilayer superstructures for electromagnetic (EM) wave absorption. Furthermore, the effect of ZIF-8 morphology (cubic or rhombic dodecahedral) on the superstructure and EM absorption performance of CNPs is investigated. The as-prepared cubic bilayer superstructure exhibits a higher BET surface area of 526.1 m2/g and a higher pore volume of 0.232 cm3/g than the rhombic dodecahedral monolayer superstructure (30.0 m2/g and 0.051 cm3/g, respectively). As a result, the two-dimensional CNPs with a bilayer structure are able to deliver the highest EM absorption performance with an effective absorption bandwidth of 6.2 GHz at a thickness of merely 2.4 mm. This work provides a new approach to designing and preparing high-performance EM wave absorption materials.

Shell engineering afforded dielectric polarization prevails and impedance amelioration toward electromagnetic wave absorption enhancement in nested‐network carbon architecture

3D reduced graphene oxide (rGO) aerogel has exhibited immense potential as electromagnetic (EM) wave absorbing materials (EWAMs) due to its unique structural advantages, but there still remains a challenge to balance the relationship between impedance matching and EM attenuation capability. Herein, a novel shell engineering strategy is proposed to fabricate 3D rGO-based aerogel with nested-network architecture by coating a dense and continuous heterogeneous layer composed of numerous N-doped porous carbon nanocubes (NPCNs). The formation of heterogeneous layer more or less increases the stability of aerogel structure and suppresses the re-stacking of rGO nanosheets. More importantly, NPCNs on the pore walls of rGO aerogel are amorphous, and thus they not only optimize impedance matching of rGO aerogel, but also induce powerful interfacial polarization thanks to the dielectric difference with rGO aerogel. As a result, the final rGO@NPCNs aerogel produces good EM absorption performance, especially for an effective absorption bandwidth (EAB) of 5.1 GHz with a thickness of merely 1.3 mm. The value of EAB can be further extended up to 12.1 GHz by gradient multilayer architecture design. Numerical simulation technique vividly demonstrates that this shell engineering strategy contributes to the penetration of incident EM wave into rGO@NPCNs aerogel as compared with individual rGO aerogels, and facilitates the generation of adequate heterogeneous interfaces to reinforce interfacial polarization loss. Moreover, rGO@NPCNs aerogel also displays good thermal insulation, waterproof functionality, and radar stealth properties, which fully addresses its bright prospects as an excellent candidate for high-performance EWAMs in the future.

Plasma-Driven Conversion of 2D Graphene into 3D Pouch for Improved Electromagnetic Absorption Performance.

Graphene-based materials are ideal for electromagnetic wave-absorbing materials (EAMs) due to their strong electrical and dielectric losses with reduced thickness and weight. To enhance the electromagnetic wave absorption performance of these materials, additional components are often incorporated. However, this approach not only increases the complexity of the synthesis process but also complicates and destabilizes the control of the material properties. In this study, we successfully employed a one-step method to reduce graphene oxide and transform 2D graphene into a 3D pocket-like structure through plasma treatment. This unique 3D structure is induced by the formation of uneven defects on the surface due to plasma treatment. The distinctive pouch-like structure of the reduced graphene oxide achieved remarkable electromagnetic wave absorption properties. Specifically, the material demonstrated a minimum reflection loss of -38.65 dB at 7.14 GHz, with an effective absorption bandwidth of 5.13 GHz and a thickness of just 1.9 mm. These results highlight the potential of plasma processing as a rapid, efficient, and environmentally friendly approach for the continuous production of advanced EAMs, paving the way for greener manufacturing practices in the industry.

Multifunctional Electromagnetic Responsive Porous Materials Synthesized by Freeze Casting: Principles, Progress, and Prospects

AbstractFreeze casting is a solidification technique utilized in the fabrication of porous materials. However, the freeze casting process is quite complex, and significant challenges remain in precisely controlling the pore size and shape of porous structures. This study aims to investigate the customization of multifunctional electromagnetic wave (EMW) absorbers with 3D porous structures via freeze casting. This review initially presents the fundamental principles underlying the freeze casting technique and examines the correlation between internal and external factors during the preparation process and porosity. The emerging trends in constructing novel and intricate macroscopic structures through freeze casting are subsequently outlined. Furthermore, this review focuses on the fabrication of composites with various porous microstructures through freeze casting of low‐dimensional building blocks, and their EMW response and multifunctional properties. By regulating the internal and external influencing mechanisms of freeze casting, porous EMW absorption materials exhibit outstanding advantages such as electromagnetic property manipulation, controllable structure, high porosity, high specific surface area, lightweight, and flexibility. These features broaden their applications in electromagnetic shielding, mechanical property, radar stealth, thermal insulation and fire prevention, flexible sensors, antifreeze ability, etc. In addition, we discuss the challenges and prospects of high‐performance EMW absorbers using freeze casting techniques.

Multifunctional molecular precursor with tunable nano-microarchitecture enables exceptional electromagnetic waves absorption

Multi-component carbon is a promising candidate for electromagnetic wave (EMW) absorption materials. However, complex and non-green preparation process with low atomic utilization efficiency compromises the merits of carbon materials. Additionally, enhancing the electromagnetic wave absorption (EMWA) is highly desirable. To face the challenge, a multifunctional molecular precursor (DQSDCI) has been developed, characterized by high atom utilization efficiency (high char yield), abundant in-situ nitrogen doping, multi-sites for composite of nano-materials (e.g. CNT) or metal ion (e.g. iron) and green preparation (water solubility). The multi-component carbons derived from DQSDCI, featuring adjustable nanostructures (nanoribbons or nanosheets) and modifiable porosity, demonstrate outstanding EMWA. The multicomponent carbon of DQSDCI, iron and CNT (DQSDCI-Fe-CNT-700) demonstrated a minimum reflection loss (RLmin) of −69.57 dB and a maximum effective absorption bandwidth (EABmax) of 5.7 GHz at about 2 mm thickness, covering a wide frequency range (4–18 GHz) by controlling the thickness between 1 and 5 mm. Moreover, simulation results indicated that the derived nanosheet is very promising application for aircraft stealth in a monostatic radar system. Abundant in-situ N doping, uniform distribution of MWCNT and ferromagnetic nanoparticles, hierarchical pore structures and various heterogeneous interfaces can synergistically improve the EMW attenuation ability by forming optimal impedance matching and multi-polarization loss.

Rare earth doped magnetoelectric composites for enhanced electromagnetic wave absorption

Magnetoelectric electromagnetic wave absorption materials (EWAMs) with multiple loss mechanisms have shown remarkable results in solving electromagnetic (EM) interference and radar stealth. However, due to the Snoek limit, the magnetic properties are affected to some extent. Hence, based on low-cost two-dimensional graphite nanosheets and magnetic ferrite, a rare-earth doping strategy is innovatively proposed, aiming to develop a high-efficiency EWAM. Specifically, taking advantage of the significant differences in magnetic moments and dimensions between Gd and Fe ion, the modified ferrite owns unusual magnetic properties and dielectric capacity. Further, direct control of the EM parameters is achieved by finely tuning the component ratio, which in turn optimizes the response characteristics of EM wave absorption. Experimental results show a maximum reflection loss of −64.04 dB and a wide effective absorption bandwidth covering 4.88 GHz, corresponding to the absorption efficiency of −42.7 dB/mm and 3.25 GHz/mm, respectively. The outstanding performance is related to the synergistic effect of multiple loss management and impedance matching, and further confirmed by the radar cross section (RCS) reduction of 29.15 dBsm. Thus, the novel way opens a new horizon for the next magnetic-based EWAMs.