Electromagnetic Absorption Materials Research Articles

Lightweight and thermally insulating ZnO/SiCnw aerogel: A promising high temperature electromagnetic wave absorbing material with oxidation resistance

Enhancing the microwave attenuation performance under high-temperature and oxidative conditions is a forefront issue for electromagnetic absorption materials. SiC nanowire material exhibits great potential due to its superior thermal stability and oxidation resistance. While, the relatively poor dielectric loss limits its further application as a high effective absorber. In this study, the strategy of laminated porous structure design, as well as the composition of ZnO nanocrystals were applied to promote the microwave attenuation capacity. A simple dual hydrolysis reaction method was employed to grow ZnO nanocrystals on SiC nanowires, followed by the preparation of a 3D layered structure of ZnO/SiCnw aerogel material using directional solidification processes. The ZnO/SiCnw aerogel demonstrated effective broadband attenuation (>90 %) across the entire X-band from room temperature to 873 K. Moreover, the material chemistry remained constant at temperatures as high as 1073 K in air. It exhibited ultralightweight properties and possessed a low thermal conductivity of approximately 0.056 W/m·K, with a density of 0.167 g/cm3. The combination of its lightweight, oxidation resistance, thermal insulation, and attractive X-band absorption efficiency positions ZnO/SiCnw aerogel as a promising EM absorption candidate at both room and high temperatures.

Waxberry-like Mo2C@N doped carbon hierarchical structures for broadband electromagnetic absorptions

Broadband electromagnetic absorption materials showcase advantages for coping the increasingly complicated electromagnetic pollution and interferences. Among them, carbon-based materials, with light weight and high stability, are potential ideal electromagnetic absorption materials. The broadband design strategy for carbon-based electromagnetic absorption materials usually involves with hierarchical structure and interface engineering, which is often costly or complex. In this paper, the phosphomolybdic acid is designed to simultaneously serve as the doping protonic acid, as well as the doping Mo source. Waxberry-like Mo2C@N doped carbon hierarchical structures are synthesized through the carbonization of low-cost polyaniline precursors. The hierarchical structures exhibit significantly enhanced electromagnetic absorptions. The optimal RL reaches −50.4 dB, and the effective bandwidth can reach 5.1 GHz at a thickness of 2.0 mm. The enhanced electromagnetic absorptions are mainly attributed to the microscale waxberry-like hierarchical structure, the Mo2C and N doped carbon polarization structures, as well as the asymmetric Mo–N interfacial hybridizations. This work provides a reference path for the design of broadband carbon-based electromagnetic absorption materials.

Shear‐Rheological‐Assisted MXene Dispersion in Epoxy Resin for Efficient Electromagnetic Absorption

AbstractMXenes, a burgeoning family of 2D materials with high conductivity and large specific surface area, are ideal electromagnetic absorbing materials. However, the ample polar functional groups lead to poor dispersion in the non‐polar matrix, limiting its application in non‐polar‐polymer‐based composites. With the help of the shear rheological properties of SiO2, the conflict is resolved here by directly dispersing MXene aqueous dispersion into the non‐polar resin. Water is locked dynamically through SiO2 nanoparticles among the MXene@SiO2 nanosheets, suppressing MXene's self‐restacking and aggregation in the resin matrix. Therefore, the fabrication of uniform MXene/non‐polar polymer composites is achieved. Meanwhile, this method allows different nanoparticles (Fe3O4, etc.) to be evenly dispersed among the MXene nanosheets to further improve the composites' electromagnetic parameters. The as‐prepared composites achieve remarkable absorbing performance with a low MXene concentration (≤5 wt.‰). The SMEP‐h achieves the maximum reflection loss value of over 60 dB at 12 GHz (at the thickness of 2.15 mm), and the SMEP‐F possesses a broad effective absorbing bandwidth of over 6.18 GHz (at the thickness of 1.75 mm). The shear‐rheological‐assisted MXene dispersion method in the non‐polar matrix paves an avenue for the design of outstanding MXene‐based electromagnetic absorbing composites.

Manipulating polarization attenuation in NbS2–NiS2 nanoflowers through homogeneous heterophase interface engineering toward microwave absorption with shifted frequency bands

Homogeneous heterogeneous (heterophase) interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization, which facilitate the transport of electrons across the substrate. Such regulation on the interfaces is effective in modulating electromagnetic wave absorbing materials. Herein, we construct NbS2–NiS2 heterostructures with NiS2 nanoparticles uniformly grown in NbS2 hollow nanospheres, and such particular structure enhances the interfacial polarization. The strong electron transfer at the interface promotes electron transport throughout the material, which results in less scattering, promotes conduct ion loss and dielectric polarization relaxation, improves dielectric loss, and results in a good impedance matching of the material. Consequently, the absorbing band may be successful tuned. By regulating the amount of NiS2, the heterogeneous interface is finely alternated so that the overall wave-absorbing performance is shifted to lower frequencies. With a NiS2 content of 15 ​wt% and an absorber thickness of 1.84 ​mm, the minimum reflection loss at 14.56 ​GHz is −53.1 ​dB, and the effective absorption bandwidth is 5.04 ​GHz; more importantly, the minimum reflection loss in different bands is −20 dB, and the microwave energy absorption rate reaches 99% when the thickness is about 1.5–4.5 ​mm. This work demonstrates the construction of homogeneous heterostructures is effective in improving the electromagnetic absorption properties, providing guideline for the synthesis of highly efficient electromagnetic absorbing materials.

Construction of Fe7S8 anchoring S-doped porous graphene with enhanced multi-band electromagnetic absorptions

At present, research bottleneck on electromagnetic absorption materials lied in achieving strong absorption with broadband and multi-band responses. In this paper, Fe7S8 anchoring S-doped porous graphene was synthesized for multi-band electromagnetic absorptions. Rhodanine played the role of ‘two birds in one stone’, converting Fe3O4 to Fe7S8 and constructing porous S-doped carbon. The hybrids exhibited multi-band electromagnetic absorptions at 10.52, 12.56 and 15.03 GHz, with effective bandwidth achieved up to 12.07 GHz. This paper showcases reference path for the design of multi-band electromagnetic absorption materials.

Electromagnetic waves absorbing performance of cypress cone derived activated carbon decorated by magnetite nanoparticles

Biomass-based porous magnetic nanocomposites were prepared for microwave absorption in the X-band range. Fe3O4 nanoparticles were precipitated on activated carbon (AC) derived from cypress cones, creating composites with carbon contents ranging from 15 to 85 % by weight. Absorption experiments revealed that 15 % wt. nanocomposite exhibited optimal performance, showing a minimum reflection loss (RLmin) of −16.3 dB at a thickness of only 2.5 mm. Notably, this composites efficient absorption bandwidth covered 80 % of the X-band at this thin dimension. This study highlights the potential of this nanocomposite as an effective electromagnetic absorption material. Cole-Cole diagrams confirmed the multiple polarization and conduction losses. The impedance mismatch plot and attenuation constant represent significant impedance matching with free space and high dissipation, which improves the performance of nanocomposites with a ferrite/AC ratio of 85:15.

Intelligent Tunable Wave-Absorbing CNTs/VO2/ANF Composite Aerogels Based on Temperature-Driving.

The development of new electromagnetic absorbing materials is the main strategy to address electromagnetic radiation. Once traditional electromagnetic wave-absorbing materials are prepared, it is difficult to dynamically change their electromagnetic wave-absorbing performance. Facing the complexity of the information age and the rapid development of modern radar, it is significant to develop intelligent modulation of electromagnetic wave-absorbing materials. Here, CNTs/VO2/ANF composite aerogels with dynamic frequency tunability and switchable absorption on/off were synthesized. Based on the phase change behavior of VO2, the degree of polarization and interfacial effects of multiple heterogeneous interfaces between VO2 and CNTs and aramid nanofibers (ANFs) were modulated at different temperatures. With the increase in temperature (from 25 to 200 °C), the maximum absorption frequency of the frequency tunable aerogel is modulated from 12.24 to 8.56 GHz in the X-band, and the absorption intensity remains stable. The maximum effective switching bandwidth (ΔEAB) of the wave-absorbing switchable aerogel is 3.70 GHz. This study provides insights into intelligent electromagnetic wave absorption performance and paves the way for temperature-driven application of intelligent modulation of electromagnetic absorbers.

Biomass-derived mulberry porous carbon for microwave absorption

In modern electronic devices and communication systems, there is an urgent need for economically viable, environmentally friendly, and efficient absorbing materials. In this work, we have successfully synthesized nitrogen-potassium doped mulberry porous carbon (MBPC) using a one-step pyrolysis strategy for the first time utilizing mulberry as a biomass carbon wave-absorbing material. The resulting MBPC exhibited a porous structure with abundant defects, facilitating the formation of a micro-conductive network and multiple reflection and scattering phenomena, thereby enabling strong microwave absorption. Experimental results demonstrated that the MBPC material achieved a remarkable minimum reflection loss of −44.82 dB at a frequency of 14.64 GHz, along with a maximum effective absorption bandwidth exceeding 5.76 GHz, all within a thickness of only 2.2 mm. Furthermore, by adjusting the thickness between 1 ∼ 3 mm, the bandwidth coverage can be extended to 8.48 ∼ 18 GHz. Computer simulation technology (CST) revealed a high simulated RCS value of 20.68 dB·m2, highlighting its significant practical application potential. This research underscores the promising prospects of mulberry-derived porous carbon as a lightweight, cost-effective, and efficient electromagnetic absorption material.

Lightweight, ultra-broadband SiOC-based triply periodic minimal surface meta-structures for electromagnetic absorption

Lightweight, wide-band ceramic-based electromagnetic (EM) absorbers have great application demand in the field of high-temperature EM wave absorption. However, it is difficult for traditional ceramic-based structural EM absorbing materials (EMAMs) to balance the contradiction between broadband absorption and good impedance matching due to resonance effect. Herein, three novel non-resonant SiOC-based triply periodic minimal surface (TPMS) meta-structures named Schoen G (SG), Schwarz D (SD) and Schwarz P (SP) with a density of 0.556 g/cm3 were successfully synthesized by digital light processing (DLP) 3D printing and polymer-derived ceramics (PDCs) method. Through the structural design of multilayer arrays and holes, three metamaterials achieve good impedance matching and broadband EM absorption. The effective absorption bandwidth (EAB) of all three meta-structures reaches 9.80 GHz (8.2–18.0 GHz) in a wide matching thickness range, covering the entire X-Ku band. In addition, the minimum reflection loss (RLmin) of −55.68 dB is obtained at a matching thickness of 3.02 mm for SD meta-structure in X-band. Besides, the SG meta-structure tested by the arch method has an ultra-wide EAB of 11.88 GHz (6.12–18.0 GHz), exhibiting ultra-broadband EM absorption properties. It is significant that the intrinsic relationships between TPMS meta-structures and EM responses are explored by CST simulation. This work provides a new perspective for the design of lightweight, broadband ceramic-based EM metamaterial absorbers under high-temperature, harsh environments.

Heterointerface engineering in porous microspheres for magnetic-dielectric balance to boost electromagnetic wave absorption

Heterointerface engineering originated from structure design is a promising approach to develop high-performance electromagnetic (EM) absorption materials but remains challenges in revealing the EM modulation mechanism. In this work, a diffusion-driven self-assemble strategy was proposed to construct porous NiFe2O4 microspheres with rich confined cavities. Followed by an in-situ vapor phase polymerization, conductive polypyrrole (PPy) layers were tightly coated on NiFe2O4 surface, building numerous ferrite-polymer heterointerfaces. Systematic investigation demonstrated that the controllable coating thickness and porous structure were crucial to regulate the component dependency EM properties and the dielectric-magnetic balance. Accordingly, these activated heterointerfaces and lattice defects inevitably produced polarization response to enhance the dielectric loss, and the confined magnetic coupling among hierarchical cavities strengthened the magnetic loss, jointly contributing to the boosted dissipation of incident EM energy. Owing to the synergy merits, optimum core–shell NiFe2O4@PPy microspheres exhibited an impressive broadband EM absorption performance with a wide effective absorption bandwidth covered 6.8 GHz at 2.62 mm. This study provides methodological guidance to design magnetic-dielectric EM absorption materials, and deciphers the mechanism of structure-interface modulated EM properties.

Construction of gradient hierarchical and hetero-interfaces structure for ultra-broad microwave absorption

Currently, carbon materials derived from biomass are widely sought after as electromagnetic absorbing(EMWA) materials owing to the unique structure, as well as the wide range of natural acquisition pathways, economic viability, and simple processing. However, due to the high dielectric properties, mismatched impedance and single attenuation mechanism, they cannot achieve efficient EMWA performance. Herein, the biomass carbon/Co/porous carbon magnetic composites with a layered gradient structure were fabricated by in-situ deposition of ZIF-67 on the lotus leaf base and then pyrolysis at high temperature. By adjusting the pyrolysis temperature, the sample obtained at 650 ​°C achieved a minimum reflection value (RLmin) of −34.2 ​dB at a matching thickness of 2.6 ​mm, and a maximum effective absorption bandwidth (EAB) of 7.12 ​GHz. The results indicate that this magnetic composite with a multi-sized layered gradient porous structure has a good electron transport network, a large number of heterogeneous interfaces, and dipole polarization centers, which are conducive to multiple reflection and scattering of microwaves, conduction loss, interface loss, magnetic loss, and impedance matching of materials. Therefore, this work provided a reference for optimizing the EMWA performance of carbon materials and designing a layered gradient porous magnetic composite with multi-sized structure.

Structural and electrodynamic characteristics of the spinel-based composite system

Two- and tree-component spinel-polymer composites were produced by thermal pressing. The initial components were chosen as CoFe2O4 and Ni0.4Cu0.2Zn0.4Fe2O4 spinels that were produced using the sol-gel method. The ratio between spinel phases varied from 1:3 to 3:1. As a polymer, fluorinated ethylene propylene was used. The concentration of the spinels in the polymer matrix was fixed at 20 mass.%. Using XRD, SEM, and high-frequency spectroscopy, the correlation between the composition, structure, and electrodynamic characteristics of composites was established. It was found that the parameters of the unit cell of ferrite fillers do not change when filling the polymer. The RL values for the initial CoFe2O4/FEP and Ni0.4Cu0.2Zn0.4Fe2O4/FEP were in the range of −14.5 … -24.2 dB and −10.4 … -14.1 dB, respectively, which is lower than for ferrites without a polymer matrix. The maximum values of RL (as a module) were marked for CoFe2O4/FEP. Obtained values of the reflection loss coefficient in the range of 5–10 GHz open broad perspectives for the development of materials for electromagnetic absorption and 5G technology.

Constructing mixed-dimensional lightweight magnetic cobalt-based composites heterostructures: An effective strategy to achieve boosted microwave absorption and self-anticorrosion

Subtle microstructure design and an appropriate multicomponent strategy are essential for advanced electromagnetic absorbing (EMA) materials with a wide effective absorption bandwidth (EAB) and intense absorption. However, sophisticated environments restrict the range of applications for EMA materials. Herein, three hollow spherical bifunctional CoSx/MnS/C nanocomposites with different crystal structures were constructed via cation exchange and subsequent vulcanization. The manganese sulfide and carbon generated during vulcanization exhibit a narrow band gap and enhanced conductivity, thereby facilitating conductive loss. The presence of cobalt sulfide facilitates the improvement of magnetic loss. More importantly, there is a potential difference between different phases at the heterogeneous interface, resulting in a region of space charge, which is conducive to interfacial polarization. The 3D hollow structure and heterogeneous dielectric/magnetic interfaces benefit the predominant EMA performance by forming perfect impedance matching, interface polarization, conduction loss, and magnetic loss effects. Specifically, an optimal reflection loss (RL) of –51.31 dB at 10.72 GHz and an effective EAB of 5.92 GHz at 2.1 mm can be achieved for Co1–xS/MnS/C nanocomposite. Moreover, the nanocomposites maintained promising self-anticorrosion properties in simulated seawater environments. Transition metal sulfides with superior self-anticorrosion properties provide a pathway to efficient wave-absorbing materials in complicated environments.

Carbon fibers coated with floral MoSe2 are applied to high-performance electromagnetic absorbing materials

Studied the microwave absorption performance of carbon fiber, mixed carbon fiber/MoSe2 (CM) bilayer composite materials in the range of 2–18 GHz. The flower-shaped layer and core-shell double-layer interface of MoSe2 work together to improve electromagnetic wave absorption, providing a new approach for designing lightweight, broadband, and strong absorption-absorbing materials. To address the drawbacks of the high conductivity of pure carbon fibers, transition metal sulfides were introduced promptly, and the CM core-shell materials with flower-shaped outer shell structures were prepared. An in-depth analysis of the working mechanism of CM absorbing materials and the influence of the interface between carbon fibers and MoSe2 on the absorbing performance has been conducted, providing a favorable experimental basis for the application of fiber membranes in absorbing materials.

Reduced graphene oxide/nonwoven fabric filled honeycomb composite structure for broadband microwave absorption

The prevalence of electromagnetic pollution in daily life has led to a rapid escalation in the demand for high-performance electromagnetic absorption and protection materials. Herein, a composite material consisting of reduced graphene oxide (RGO)/nonwoven absorbent was prepared and filled into honeycomb structures. The single-layer nonwoven/honeycomb composite, with a thickness of 5 mm, demonstrates an effective absorption bandwidth (reflection loss ≤ −10 dB) reaching 12.1 GHz (5.9 GHz–18 GHz) and a minimum reflection loss of −37 dB. This is attributed to the synergistic absorption effects of conduction loss, interfacial scattering, dielectric relaxation, and multiple scattering losses. Furthermore, the bilayer composite structure demonstrates the capability to achieve full band absorption of 2 GHz–18 GHz with a thickness of only 10 mm, giving carbon materials a thin and lightweight absorption effect. In addition, the composite materials exhibit excellent mechanical properties. This study presents a new idea for the design and manufacture of broadband, lightweight, and high-performance microwave absorbers, which holds significant potential in the field of electromagnetic pollution prevention and absorption.

Layered composites made of polymer derived SiOC/ZrB2 reinforced by ZrO2/SiO2 fibers with simultaneous microwave absorption and thermal insulation

To simultaneously improve the microwave absorption and thermal insulation properties of the ceramic materials for stealth high-speed vehicles, layered composites made of polymer-derived SiOC/ZrB2 reinforced by ZrO2/SiO2 fibers were reported in this work. The composites possess a continuous multilayer structure, which was fabricated via the precursor impregnation assisted by hot press curing and pyrolysis using the transparent ZrO2/SiO2 fibers and polymer-derived SiOC and nano ZrB2. The layered composites show an effective absorption band (EAB) of 4.2 GHz at a thickness of 2.9 mm and a minimum reflection loss of –59.34 dB. The exceptional electromagnetic (EM) wave attenuation capability is ascribed to the impedance matching as well as massive EM wave loss caused by the multilayers in which the nano ZrB2 provides interfacial polarization and electrical conduction loss. With a design of the multi-curvature arch structure, a remarkable reduction of radar cross section can be achieved. Besides, the layered composites exhibit good oxidation resistance and thermal insulation when exposed to the dynamic heating environment, demonstrating the potential application in harsh environments used for multifunctional electromagnetic absorbing materials.

Insights into Civilian Electromagnetic Absorption Materials: Challenges and Innovative Solutions

AbstractThe emergence and widespread adoption of fifth‐generation wireless technology in civilian sectors have advanced the information revolution, while simultaneously leading to a variety of negative impacts. Foremost issues in the civilian domain include electromagnetic (EM) pollution, interference, and the inefficient use of EM energy. Despite growing global awareness, progress in devising effective solutions is sluggish, underlining the complexity of these issues. The delay in addressing EM concerns arises from several factors, including a considerable gap in comprehensive understanding and the absence of a unified stance on these critical issues. Moreover, the emergence of new challenges like EM interference and energy inefficiency indicates a clear need for innovative ideas and approaches. Addressing these civilian issues extends beyond the inherent properties of EM absorbers, requiring combination of tailored macro‐structural designs and external energy field management for a comprehensive solution. This situation emphasizes the urgent need for diverse strategies and creative thinking to navigate the challenges posed by the civilian EM issues. This perspective underscores these identified challenges and systematically proposes practical approaches to each, aiming to foster both conversation and action in this crucial area. The insights provided are expected to substantially aid in confronting and alleviating these pressing EM concerns.

Structural, Magnetic, and Electrical Investigations of PVA/Ni Ferrite/(MoS2)x Nanocomposites.

Transition metal sulfides (TMDs) possess exceptional dielectric properties and a narrow band gap, rendering them highly efficient as electromagnetic absorbing materials. Among these TMDs, the two-dimensional MoS2 nanosheet has received significant attention in research. However, the quest for new absorbers no longer finds satisfaction in solitary absorption mechanisms. This article introduces a successful method for creating PVA/NiFe2O4/(MoS2)x nanocomposites via a straightforward sol-gel technique, wherein porous amorphous NiFe2O4 microspheres are integrated into MoS2 nanosheets. The investigation uncovers that the incorporation of MoS2 results in an enhanced complex permittivity, facilitating the attainment of a desirable permittivity level. The PVA/NiFe2O4/(MoS2)x nanocomposite absorber exhibits an incredibly low reflection loss (RL) of -16.75 dB at a mere thickness of 1 mm, achieved through the cooperative interaction of dielectric and magnetic loss, along with the advantages of the structure and composition. Consequently, the PVA/NiFe2O4/(MoS2)x nanocomposites effectively absorb electromagnetic waves. Therefore, it is posited that MoS2-based composites hold great promise as highly effective microwave absorbers, boasting strong absorption intensity and a wide absorption frequency range, given the exceptional performance of the as-fabricated PVA/NiFe2O4/(MoS2)x nanocomposites.

Efficient electromagnetic wave absorption of polypyrrole/low-reduction graphene oxide composites through dielectric properties modulation

Graphene oxide (GO) is widely used in electromagnetic microwave absorption (EMA) materials due to its abundant oxygen-containing functional groups and defects. Its conductivity, surface functional groups and defect density can be modified by controlling reduction degree to modulate its electromagnetic properties. However, the thermal reduction temperature needed is often too high, exceeding the Curie temperature of magnetic materials, which makes further compounding difficult. Polypyrrole (PPy), as a conductive polymer with high electrical conductivity, is widely used in EMA field and can help regulate the dielectric properties of materials. In this paper, a series of PPy/GO composites with different ratios and reduction degrees were prepared by in situ polymerization and thermal reduction, and their EMA properties were investigated. At a loading amount of 7.5 wt%, the maximum reflection loss of PPy/rGO composites can reach −66.64 dB, and the effective absorption bandwidth can reach 6.74 GHz with a reduction temperature of only 400 °C. Furthermore, the unreduced sample also has excellent absorption performance, which has a wide range of applications for future one-step compositing with magnetic materials in low reduction temperature.

Electromagnetic Absorbing Materials Design by Optimization Using a Machine Learning Approach

One of the state-of-the-art strategies to decrease the isolation between sections of personal digital assistance devices, taking into account the unavoidable thermal, mechanical, weight, and manufacturability constraints is the proper introduction of electromagnetic (EM) absorbing materials. The global target of this study is the optimized synthesis of the EM properties of a material using a machine learning approach. The sought material must improve the shielding effectiveness between two regions of a device. The first part of this paper is dedicated to the assessment of the performances of an artificial neural network used as function approximation to compute the values of the shielding without resorting to complex and time-consuming full-wave numerical simulations. The network is assessed with respect to either the variations of the training set and algorithm or of its architecture. Significant figures of merit are introduced. The second part is devoted to the description and definition of nature-inspired algorithms demanded to manage the optimization problem.