Electromagnetic Wave Absorption Research Articles

NiCoZn/C@melamine sponge-derived carbon composites with high-performance electromagnetic wave absorption

NiCoZn/C@melamine sponge-derived carbon composites with high-performance electromagnetic wave absorption

Kirkendall Effect-Induced Ternary Heterointerfaces Engineering for High Polarization Loss MOF-LDH-MXene Absorbers.

Heterogeneous interfacial engineering has garnered widespread attention for optimizing polarization loss and enhancing the performance of electromagnetic wave absorption. A novel Kirkendall effect-assisted electrostatic self-assembly method is employed to construct a metal-organic framework (MOF, MIL-88A) decorated with Ni-Fe layered double hydroxide (LDH), forming a multilayer nano-cage coated with Ti3C2Tx. By modulating the surface adsorption of Ti3C2Tx on LDH, the heterointerfaces in MOF-LDH-MXene ternary composites exhibit excellent interfacial polarization loss. Additionally, the Ni-Fe LDH@Ti3C2Tx nano-cage exhibits a large specific surface area, abundant defects, and a large number of heterojunction structures, resulting in excellent electromagnetic wave absorption performance. The MIL-88A@Ni-Fe LDH@Ti3C2Tx-1.0 nano-cage achieves a reflection loss value of -46.7 dB at a thickness of 1.4mm and an effective absorption bandwidth of 5.12 GHz at a thickness of 1.8mm. The heterojunction interface composed of Ni-Fe LDH and Ti3C2Tx helps to enhance polarization loss. Additionally, Ti3C2Tx forms a conductive network on the surface, while the cavity between the MIL-88A core and the Ni-Fe LDH shell facilitates multiple attenuations by increasing the transmission path of internal incident waves. This work may reveal a new structural design of multi-component composites by heterointerfaces engineering for electromagnetic wave absorption.

Template-free synthesize of PANI nanostructures: Modulating structure for enhanced dielectric characteristics and superior electromagnetic wave absorption

To provide electromagnetic protection for intelligent equipment, advanced electromagnetic wave absorption (EWA) materials are highly desired. To reveal the interaction mechanism of structure and electromagnetic waves, polyaniline (PANI) with various structures, including nanosheets, clusters, and nanofibers, is synthesized via a template-free approach. The self-assembly process of PANI can be regulated by camphor sulfonic acid due to the formation and guidance of charge transfer complexes. A comprehensive analysis of structure, chemical constitution, and electromagnetic characteristics is conducted. Clusters with three-dimensional micro-nano structure exhibit superior microwave absorption, achieving a minimum reflection loss of −52.22 dB at 9.84 GHz with a 3.2 mm thickness and an absorption bandwidth of 6.12 GHz at 2.3 mm thickness. The outstanding EWA performance is attributed to the unique architecture, strong dielectric loss capabilities, and effective impedance matching. Moreover, the fabrication process is cost-effective and scalable, making it conducive to practical applicability.

Advances in Carbon Microsphere-Based Nanomaterials for Efficient Electromagnetic Wave Absorption.

Carbon microspheres have indeed shown great promise as effective materials for absorbing electromagnetic waves, particularly in microwave applications. Their unique properties, such as high surface area, porosity, and electronic characteristics, make them ideal candidates for addressing the growing concerns around electromagnetic pollution from electronic devices. By leveraging the properties of these materials, we can work toward creating more efficient and sustainable electromagnetic wave absorption technologies. Recent efforts have focused on synthesizing and investigating carbon microsphere-based electromagnetic wave-absorbing nanomaterials with the ambition of achieving the desired attributes of being thin, light, wide, and robust. This Review first delves into the detailed mechanism of electromagnetic wave absorption, followed by an elucidation of the preparation methods for carbon microsphere-based nanomaterials. Furthermore, it systematically outlines the common methods and strategies employed to improve the microwave absorption capabilities of carbon microspheres, including chemical vapor deposition, emulsion polymerization, hydrothermal methods, and template methods. Lastly, it outlines the challenges encountered by carbon microsphere-based electromagnetic wave absorption nanomaterials and outlines their prospects, mainly morphology change, component hybridization, and elemental doping. This Review aims to provide valuable insights into the creation of carbon microsphere nanomaterials with excellent electromagnetic wave absorption properties.

Synchronously Formed Hetero- and Hollow Core-Branch Nanostructure Toward Wideband Electromagnetic Wave Absorption.

The intrinsic limitation of low electrical conductivity of MoSe2 resulted in inferior dielectric properties, which restricts its electromagnetic wave absorption (EMWA) performances. Herein, a bimetallic selenide of MoSe2/CoSe2@N-doped carbon (NC) composites with hollow core-branch nanostructures are synthesized via the selenization treatment of MoO3 nanorods coated with ZIF-67. By adjusting the mass ratio of ZIF-67 to MoO3, the electromagnetic parameters and morphologies of composites are finely tuned, further ameliorating the impedance matching and EMWA performances. The involvement of NC improves the electronic conductivity of the composites. The synchronously formed heterostructure not only facilitates charge transfer but also leads to the accumulation and uneven distribution of charges, thus enhancing the conductive loss and polarization loss. The hollow core-branch nanostructure provides abundant conductive networks, heterointerfaces, and voids, significantly enhancing the EMWA property. Density functional theory implies that the heterostructures effectively boost charge transport and change charge distribution, which heightens the conductive loss and polarization loss. As a result, the composites demonstrate a minimum reflection loss value of -53.53 dB at 9.04 GHz, alongside a maximum effective absorption bandwidth of 6.32 GHz. This work offers invaluable insights into novel structural designs for future research and applications.

Air-microwave simultaneously induced carbon fiber surface oxidation and magnetism adjustment by CoOx nanoparticles rapid assembly for interface enhancement and electromagnetic wave absorption of its composites

It is a significant challenge to develop a fast carbon fiber (CF) surface modification method, especially for the high strength electromagnetic wave (EMW) absorption materials. Herein, magnetic CoOx nanoparticles are successfully synthesized and uniformly assembled on CF surface with high oxygen-containing groups by rapid ambient microwave carbon thermal shock (MCTS). The presence of oxygen defect sites on CF surface promotes CoOx nanoparticles nucleation. The number of oxygen defects and the types of magnetic nanoparticles on the CF surface effectively adjust the surface chemical activity and the electromagnetic properties of CF, which is conducive to improving the EMW absorption performance and interface compatibility of the CoOx nanoparticles modified CF reinforced polyamide 6 (CO@CF/PA6) composites. Compared with CO@CF-0 s/PA6, the tensile strength and modulus of CO@CF-3.5 s/PA6 composite are increased by 18.1 % and 18.6 %, respectively. It also displays a minimum reflection loss value (−59.9 dB) at a thinner thickness of 1.9 mm while the maximum effective absorption bandwidth reaches 5.02 GHz with a thickness of 1.8 mm. Its radar cross-section values exhibit less than −10 dBm2 at all tested detection angles. This rapid MCTS shows great potential for large-scale production of CF modification with low-cost, efficient and environmentally friendly process.

Wideband water-based switchable metasurface absorber/reflector

A water-based switchable absorber/reflector (WSAR) based on toner-coated honeycomb is proposed. The structure consists of a metasurface absorbing layer, a toner honeycomb layer, a water layer and a metal plate. The combination of metasurface and coated toner honeycomb can realize the function of broadband absorption, and the water layer is used as a control purpose to obtain a good reflection effect by filling the container with water. When the water container is in the state of without water, it behaves as an electromagnetic wave absorber with good absorption performance in the frequency band of 4.72–17.50 GHz. When the water container is in the state of full water，it behaves as a reflector with good reflection performance (reflection coefficient close to −1 dB in the 4.5–10 GHz band) in the operating frequency band. The characteristics and mechanism of the WSAR are analyzed by using the energy loss and equivalent impedance matching, and the correctness of the design is verified by experiments. The proposed structure has certain application value in radar target stealth, electromagnetic compatibility, adaptive camouflage.

Magnetic properties and microstructural of ion-implanted Gadolia doped Ceria-Barium monoferrite thin film deposited on Kapton for electromagnetic wave absorber application

Gadolia-doped Ceria-Barium Monoferrite (GDC-BaFe2O4) thin films have been deposited on Kapton sheets using the DC sputtering method as electromagnetic (EM) wave-absorbing materials. The present study has examined the structural, magnetic, and microwave absorption properties of GDC-BaFe2O4. The primary approaches used in this investigation included changing the surface form and applying EM wave-absorbing materials as surface coatings. X-ray diffraction research showed that the GDC-BaFe2O4 thin films have an orthorhombic crystal structure. The bonding investigation revealed the existence of Fe-O, Ce-O, and Ba-O-Ba functional groups at 426.87, 517.42 and 1014.84 cm−1, respectively. Vibrating-sample magnetometry confirmed that saturation magnetization decreased with increasing sputtering time and revealed the ferromagnetic behavior of the GDC-BaFe2O4 thin film. Ce, Gd, Ba, Fe, and O were evenly and similarly distributed over the Kapton surface of the GDC-BaFe2O4 thin films, according to energy-dispersive X-ray spectroscopy and scanning electron microscopy. Based on the atomic force microscopy test, the root-mean-square roughness (Rq) increased during the ion implantation procedure. With a 7.5-minute sputtering period, the microwave absorption ability reached a maximum reflection loss value of −39.6 dB (99.98 %) at 10 GHz. As a result of these findings, GDC-BaFe2O4 appears to be a promising candidate for EM wave absorption.

Investigation of the Effect of Alloying Element Equilibrium Relationship on the Electromagnetic Microwave Absorption Properties of Nano FeNi Magnetic Particles

AbstractIn order to effectively comprehend the impact of alloying element equilibrium relationship of binary nano‐magnetic particles on their electromagnetic wave absorption performance, four sets of binary nano FeNi magnetic particles with Fe:Ni alloy ratios of 2:8, 4:6, 6:4, and 8:2 were prepared with liquid‐phase reduction and the microstructure, static magnetic properties, and electromagnetic wave absorption performance of the particles were studied. The results show that the nano FeNi magnetic particles exhibit a spherical geometric structure, with a decrease in crystallinity as the Fe:Ni alloy ratio increases. The remanence and coercivity initially increase and then decrease with the increased Fe:Ni alloy ratio, with a 270 % decrease in saturation magnetization intensity as the alloy ratio changes from 2:8 to 8:2. With the increase in the Fe:Ni alloy ratio, the real and imaginary parts of the complex permittivity exhibit a decreasing trend, while the real part of the magnetic permeability decreases with increasing frequency. Aside from the 8:2 Fe:Ni alloy ratio, significant polarization relaxation losses were observed in the prepared magnetic particles, with eddy current losses was not the main mechanism of magnetic losses. The attenuation constant shows a peak at high frequencies, and the impedance matching performance increases with the increase in the Fe:Ni alloy ratio. When the Fe:Ni alloy ratio changes from 2:8 to 8:2, the minimum reflection loss decreased by 3340 %, and at a thickness of 2.1 mm and a frequency of 12 GHz, the FeNi alloy particles with a ratio of 2:8 exhibited a minimum reflection loss of −17.2 dB with an effective absorption bandwidth of 1.92 GHz.

Shifting d‐band Center: An Overlooked Factor in Broadening Electromagnetic Wave Absorption Bandwidth

AbstractAbsorption bandwidth is one of the key performance metrics for electromagnetic wave (EMW) absorbers. Traditional oxide absorbers, despite their merits such as abundance, long‐term stability, and low cost, have long been plagued by their inferior absorption bandwidth (typically less than 4 GHz). Herein, a novel concept is proposed: the introduction of cation vacancies and heterostructures into oxides can remarkably broaden their absorption bandwidth. A broadening value of 7.75 GHz is observed through this route, surpassing the broadening achieved by other existing engineering methods, by ≈100%. Crucially, this study discovers that a negative shift in the d‐band center, a previously overlooked factor, is responsible for this broadening phenomenon. By inducing cation vacancies and heterostructures, a negative shift in the d‐band center gives rise to an increase in carrier concentration and promotion of charge separation, resulting in higher conductive and polarization losses, ultimately leading to a broader absorption bandwidth. The applicability of this concept is validated in another distinctly different system, where the absorption bandwidth also experiences a remarkable increase (from 0 to 6.86 GHz). This study offers significant implications for designing wide bandwidth EMW absorbers and expands their applications in various scenarios such as wearable electronics and artificial intelligent devices.

Polarization regulation in core-shell HNTs@Metal/C for high-performance of electromagnetic wave absorption

Enhancing polarization loss is an effective method to improve electromagnetic wave absorption (EMA) performance. However, constructing more interfaces and inducing defects is a significant challenge in polarization regulation. This paper reports synthesizing a core-shell structure HNTs@M/C (M=Cu, Co, Zn) by pyrolysis of metal-organic frameworks (MOFs). The enhancement of conduction loss is attributed to the electronic conduction network formed by the carbon layer and the metal particles. Co nanoparticles (NPs) create more interfaces with the carbon layer, significantly boosting polarization performance. Additionally, Zn sublimation induces numerous defects in the carbon layer, leading to cumulative amplification of polarization and stronger dielectric resonances in HNTs@Zn/C. With a thickness of 2.4 mm, the HNTs@Zn/C achieve an effective absorption bandwidth (EAB) of 6.9 GHz, covering the entire Ku-band with a minimum reflection loss of −61 dB. This work provides design strategies for interfacial and point interaction of polarization regulation.

Electric-magnetic dual-gradient structure design of thin MXene/Fe3O4 films for absorption-dominated electromagnetic interference shielding

The challenge of achieving high-performance electromagnetic interference (EMI) shielding films, which focuses on electromagnetic waves absorption while maintaining thin thickness, is a crucial endeavor in contemporary electronic device advancement. In this study, we have successfully engineered hybrid films based on MXene nanosheets and Fe3O4 nanoparticles, featuring intricate electric–magnetic dual-gradient structures. Through the collaborative influence of a unique dual-gradient structure equipped with transition and reflection layers, these hybrid films demonstrate favorable impedance matching, abundant loss mechanisms (Ohmic loss, interfacial polarization and magnetic loss), and an “absorb-reflect-reabsorb” process to achieve absorption-dominated EMI shielding capability. Compared with the single conductive gradient structure, the dual-gradient structure effectively enhances the absorption intensity per unit thickness, and thus reduces the thickness of the film. The optimized film demonstrates a remarkable EMI shielding effectiveness (SE) of 49.98 dB alongside an enhanced absorption coefficient (A) of 0.51 with a thickness of only 180 μm. The thin films with a dual-gradient structure hold promise for crafting absorption-dominated electromagnetic shielding materials, highlighting the potential for advanced electromagnetic protection solutions.

Customized Pore Creation Strategies for Hyperelastic, Robust, Insulating Multifunctional MXene Aerogels for Microwave Absorption.

The construction of heterogeneous microstructure and the selection of multicomponents have turned into a research hotspot in developing ultralight, multifunctional, high-efficiency electromagnetic wave absorbing (EMA) materials. Although aerogels are promising materials to fulfill the above requirements, the increase in functional fillers inevitably leads to the deterioration of intrinsic properties. Tuning the electromagnetic properties from the structural design point of view remains a difficult challenge. Herein, we design customized pore creation strategies via introducing sacrificial templates to optimize the conductive path and construct the discontinuous dielectric medium, increasing dielectric loss and achieving efficient microwave absorption properties. A 3D porous composite (MEM) was crafted, which encapsulated an EVA/FeCoNi (EVA/MNPs) framework with Ti3C2Tx MXene coating by employing a direct heated cross-linking and immersion method. Controllable adjustment of the conductive network inside the porous structure and regulation of the dielectric character are achieved by porosity variation. Eventually, the MEM-5 with a porosity of 66.67% realizes RLmin of -39.2 dB (2.2 mm) and can cover the entire X band. Moreover, through off-axis electronic holography and the calculation of conduction loss and polarization loss, the dielectric property is deeply investigated, and the inner mechanism of optimization is pointed out. Thanks to the inherent characteristic of EVA and the porous structure, MEM-5 showed excellent thermal insulating and superior compressibility, which can maintain 60 °C on a 90-100 °C continuous heating stage and reached a maximum compressive strength of 60.12 kPa at 50% strain. Conceivably, this work provides a facile method for the fabrication of highly efficient microwave absorbers applied under complex conditions.

Innovative design to achieve a multi-band electromagnetic wave stealth.

Metamaterials have opened up a new field of electromagnetic wave stealth that can achieve cross-band electromagnetic wave stealth through high electromagnetic wave absorption and low infrared emission. However, traditional cross-band stealth metamaterials make covering the terahertz band challenging and have certain design flaws. This Letter introduces an innovative cross-band electromagnetic wave stealth metasurface design that can achieve cross-band stealth in the infrared, microwave, and THz bands. We use phase change materials and the gradient principle to achieve GHz and THz cross-band absorption. We also design surface height-covered low infrared emitting materials, which give them lower infrared emissivity. These functions give it enormous potential in military applications, and using phase change materials for cross-band absorption also provides new, to our knowledge, ideas for multifunctional stealth materials.

Enhanced microwave absorption in GaFeO3 coated CoFe2O4 nano-hollowsphere

As a multiferroic material with substantial magnetoelectric coupling, gallium ferrite (GaFeO3, GFO) has been intensively studied in recent years. Cobalt ferrite (CoFe2O4, CFO) nano-hollowsphere (NHS), on the other hand, is found to be an efficient material for electromagnetic (EM) wave absorption. In this work, a composite consisting of magnetostrictive CFO NHS coated with GFO nanoparticles [(1−x)CoFe2O4 – xGaFeO3, for x = 0.0, 0.9, 0.7, 0.5, 0.3, and 1.0] is prepared as an effective strategy to develop highly efficient microwave material. The EM wave absorption properties of the samples are thoroughly investigated across a widely used frequency range of 1–20 GHz. Remarkable performance of the x = 0.7 composite is evident by its effective bandwidth of approximately 3 GHz and a minimum reflection loss of approximately −63.26 dB. Moreover, the excellent impedance matching, with |Zin/Z0| ≅ 1.00, observed in the aforementioned composite, satisfies well with the required characteristics for a superior microwave absorber. Therefore, a core–shell nanostructure consisting of CFO NHS as core and GFO with optimized shell thickness can be used successfully in microwave devices.

Enhanced electromagnetic wave absorption of bacterial cellulose/ reduced graphene oxide aerogel by eco-friendly in-situ construction

Electromagnetic wave absorption materials (EWAMs) have become an effective means to address electromagnetic (EM) radiation and enhance stealth technology, among which aerogels are valued for their lightweight nature and excellent designability. This study utilized environmentally friendly preparation and in-situ reduction techniques to fabricate bacterial cellulose (BC) / reduced graphene oxide (RGO) aerogels, achieving tailored EM wave loss capabilities by controlling the reduction time of ascorbic acid. Benefitting from the effects of freeze-casting, BC winding, hydrogen bond, and RGO layers coupling, the aerogel maintains their original structure after reduction and exhibits satisfactory EM wave absorption. The minimum reflection loss (RLmin) is −38.52 dB, with an effective absorption bandwidth (EAB) of 6.68 GHz and a maximum radar cross section (RCS) reduction of 44.69 dBsm. Additionally, the aerogel’s lightweight (a low density of 9.03 mg/cm3) and outstanding thermal insulation properties enable it to adapt to complex conditions. Thus, the study provides a novel approach for the construction of industrialized and sustainable RGO-based EWAMs.

Controllable Preparation of Helical Carbon Nanofibers for Electromagnetic Wave Absorption

Controllable Preparation of Helical Carbon Nanofibers for Electromagnetic Wave Absorption

Multiple tuned carbon nanotubes by rare earth oxides for high-efficiency electromagnetic wave absorption

Multiple tuned carbon nanotubes by rare earth oxides for high-efficiency electromagnetic wave absorption

Constructing multi-polarization in metal–organic framework gels for electromagnetic wave absorption via ethanolamine hetero-coordination

Metal–organic framework (MOF) gels offer the potential for tunable electromagnetic wave (EMW) absorption owing to their customizable MOF cross-linked networks and strongly polar liquids. This overcomes the drawbacks of traditional MOF-derived absorbers; however, the corresponding EMW loss mechanism is absent. Here, a zeolite imidazole framework (ZIF) was used as a functional unit in conjunction with ethanolamine (EtA) hetero-coordination and methanol to fabricate ZIF organogels with the desired EMW absorption. The pore size of ZIF maintains the permeability for EtA and the methanol-barrier properties, which results in the formation of free –NH2 and associated –NH2 for EtA. The two corresponding species of dipole polarization losses provide additional EMW attenuation. Furthermore, the intensity inversion of the dual relaxation modes caused by the change in the size of the ZIF colloidal particles was used to improve the EMW absorption for the first time. ZIF organogels exhibited a strong correlation between dielectric properties and metal node species/EtA coordination density/hydrogen bonds, indicating that the absorption properties can be accurately regulated. Me-ZnCo-1 sample demonstrates the optimal effective absorption bandwidth of 6.59 GHz at 2.19 mm. This study not only elucidates the EMW loss mechanism of ZIF organogel networks but also proposes a creative design strategy for EMW-absorbing MOF gels.

A novel high-entropy perovskite Ba(Zn0.2Yb0.2Ta0.2Nb0.2V0.2)O3 ceramic with excellent Electromagnetic wave absorption properties

In order to solve the increasingly serious electromagnetic wave pollution, the preparation of high-performance electromagnetic wave absorbing (EWA) materials has been very urgent. High-entropy ceramics have a good prospect in the field of EWA materials due to the unique effect brought by its multi-component elements. Therefore, in this study, the composition of high-entropy ceramics was designed by utilizing the Goldschmid tolerance factor. Then the high-entropy perovskite Ba(Zn0.2Yb0.2Ta0.2Nb0.2V0.2)O3 ceramic (BZO) with high EWA performance was prepared by high-temperature solid-phase method. The EWA mechanism of the material was explored based on the phase composition, microstructure and electromagnetic parameters of the samples. Good impedance matching and better attenuation ability were obtained for BZO-1100 due to the crystallographic transition and interface increase. As a result, BZO-1100 achieves excellent EWA performance at a thickness of 2.12 mm, with a minimum reflection loss (RLmin) of −54.09 dB and an effective absorption bandwidth (EAB) of 2.81 GHz in the X-band. In addition, the possibility of the practical application of the BZO high-entropy ceramics is verified by electric field distribution simulations and RCS simulations. This study provides a valuable reference for the design of high-performance high-entropy perovskite ceramic absorber materials.