Tunable Electromagnetic Wave Absorption Research Articles

Synthesis of SiOC@C ceramic nanospheres with tunable electromagnetic wave absorption performance

Synthesis of SiOC@C ceramic nanospheres with tunable electromagnetic wave absorption performance

Dual-Step Redox Engineering of 2D CoNi-Alloy Embedded B, N-Doped Carbon Layers Toward Tunable Electromagnetic Wave Absorption and Light-Weight Infrared Stealth Heat Insulation Devices.

2D layered metallic graphite composites are promising electromagnetic wave absorption materials (EWAMs) for their combined properties of abundant interlayer free spaces, rich metallic polarized sites, and high conductivity, but the controllable synthesis remains rather challenging. Herein, a dual-step redox engineering strategy is developed by employing cobalt boron imidazolate framework (Co-BIF) to construct 2D CoNi-alloy embedded B, N-doped carbon layers (2D-CNC) as a promising EWAM. In the first step, a chemical etching oxidation process on Co-BIF is used to obtain an optimized 2D-CoNi-layered double hydroxide (2D-CoNi-LDH) intermediate and in the second, high-temperature calcination reduction is implemented to modify graphitization of the degree of the 2D-CNC. The obtained sample delivers superior reflection loss (RLmin) of -60.1dB and wide effective absorption bandwidth (EAB) of 6.24GHz. The synergy mechanisms of interfacial/dipole polarization and magnetic coupling are in-depth evidenced by the hologram and Lorentz electron microscopy, revealing its significant contribution on multireflection and impedance matching. Further theoretical evaluation by COMSOL simulation in different fields based on the dynamic loss process toward the test ring reveals the in situ EW attenuation process. This work presents a strategy to develop multifunctional light-weight infrared stealthy aerogel with superior pressure-resistant, anti-corrosion, and heat-insulating properties for future applications.

Highly electrically conductive MOF/conducting polymer nanocomposites toward tunable electromagnetic wave absorption

Metal-organic frameworks (MOFs) have attracted significant interest as self-templates and precursors for the synthesis of carbon-based composites aimed at electromagnetic wave (EMW) absorption. However, the utilization of high-temperature treatments has introduced uncertainties regarding the compositions and microstructures of resulting derivatives. Additionally, complete carbonization has led to diminished yields of the produced carbon composites, significantly limiting their practical applications. Consequently, the exploration of pristine MOF-based EMW absorbers presents an intriguing yet challenging endeavor, primarily due to inherently low electrical conductivity. In this study, we showcase the utilization of structurally robust Zr-MOFs as scaffolds to build highly conductive Zr-MOF/PPy composites via an inner-outer dual-modification approach, which involves the production of conducting polypyrrole (PPy) both within the confined nanoporous channels and the external surface of Zr-MOFs via post-synthetic modification. The interconnection of confined PPy and surface-lined PPy together leads to a consecutive and extensive conducting network to the maximum extent. This therefore entails outstanding conductivity up to ∼14.3 S cm−1 in Zr-MOF/PPy composites, which is approximately 1–2 orders of magnitude higher than that for conductive MOF nanocomposites constructed from either inner or outer modification. Benefiting from the strong and tunable conduction loss, as well as the induced dielectric polarization originated from the porous structures and MOF-polymer interfaces, Zr-MOF/PPy exhibits excellent microwave attenuation capabilities and a tunable absorption frequency range. Specifically, with only 15 wt.% loading, the minimum reflection loss (RLmin) can reach up to –67.4 dB, accompanied by an effective absorption bandwidth (EAB) extending to 6.74 GHz. Furthermore, the microwave absorption characteristics can be tailored from the C-band to the Ku-band by adjusting the loading of PPy. This work provides valuable insights into the fabrication of conductive MOF composites by presenting a straightforward pathway to enhance and regulate electrical conduction in MOF-based nanocomposites, thus paving a way to facilely fabricate pristine MOF-based microwave absorbers.

Designed MoSe2 modified multi-layer hollow carbon fiber composite material achieves tunable electromagnetic wave absorption in the X and Ku bands

As a substitute for graphene-based carbon materials, carbon fiber (CF) based absorbing materials have enormous application prospects. Effective improvements have been made in solving the problems of heavy quality and complex preparation processes of ordinary absorbing materials. In order to obtain a flexible thin fiber membrane absorbing material with good stability and excellent performance, we prepared a multi-layer hollow carbon sphere/CF@MoSe2 with carbon fiber as the matrix, and controlled the microstructure through hollow carbon shell and MoSe2, and introduced transition metal chalcogenides to coordinate electromagnetic parameters. As a result, the hollow carbon sphere/CF@MoSe2 flexible composite film achieved a minimum reflection loss (RLmin) of −47.98 dB at a thickness of 2.5 mm, and an effective bandwidth (EAB) of 8.1 GHz at a thickness of 2.7 mm. The RLmin of the hollow carbon ball/CF composite film reached −45 dB at a thickness of 2.6 mm, and the EAB reached 3.2 GHz. The theoretical characterization results jointly prove the reason for the improved performance, and this study provides an experimental basis for a more in-depth exploration of the birth of new absorbing materials.

Phytic acid-assisted hybrid engineering of MOF-derived composites for tunable electromagnetic wave absorption

Hybrid engineering is gradually deemed as a powerful approach to solving the bottleneck problem of metal-organic framework (MOF) derived absorbers for practical application. Herein, a new type of semiconductor/carbon-based hybrid material was successfully prepared by phytic acid (PA) modification and carbonization of MOF/bacterial cellulose (BC) precursors, which remedied the drawbacks of structural instability, lethal byproducts and complicated steps reported previously. Specifically, the obtained Fe(PO3)2@C/phosphorus-doped carbon foam (Fe(PO3)2@C/PCF) had a 3D hybrid micro-nanostructure that integrated spatial microcurrent network, multi-level pores, heterogeneous interfaces and lattice defects, showing its unique advantages of low filler content (15 wt.%), moderate surface reflectivity, multi-band microwave absorption and radar stealth. The experimental analysis and CST simulation further revealed that PA dosage can precisely adjust the hybrid phase content, pore texture and electromagnetic parameters of the final product to achieve synergistic enhancement of multiple dielectric response, impedance matching and attenuation capacity. As a result, an effective bandwidth (EAB) of 6 GHz and a minimum reflection loss (RLmin) of −57.0 dB were obtained in the Ku- and C-bands, respectively. These encouraging results may advance the development of novel MOF-derived absorbents based on the hybridization principle.

Ni1−xZnxFe2O4/coal-based carbon composites with tunable electromagnetic wave absorption properties prepared with microwave irradiation and hydrothermal reaction

A simple hydrothermal method combined with microwave irradiation was used to synthesize nickel-zinc ferrite/coal-based carbon (Ni1−xZnxFe2O4/CBC) composites. The influences of Zn2+ concentration on the magnetism and microwave absorption characteristics of Ni1−xZnxFe2O4/coal-based carbon composites were examined. The Ni1−xZnxFe2O4 particles were equally anchored on the coal-based carbon within the Ni1−xZnxFe2O4/CBC composites. The dielectric and magnetism characteristics of Ni1−xZnxFe2O4/CBC composites can be improved simultaneously by adjusting the Zn2+ concentration. The minimum reflection loss (RLmin) for the sample at x = 0.4 is −65.5 dB for a thickness of 4.0 mm. The samples also have typical soft magnetic properties. Furthermore, some possible mechanisms of microwave absorption are investigated. Our Ni1−xZnxFe2O4/CBC composites show great potential for microwave absorption applications.

P-doped in the shell of Ni@WO3-δ nanocomposites induced electronic structure change for improving microwave absorption performance

In this work, we reported P-doped WO3-δ coated Ni (Ni@P-WO3-δ) nanocomposites prepared by the arc discharge method with a subsequent phosphorylation treatment, where the Ni@P-WO3-δ nanocomposites exhibited a tunable electromagnetic wave absorption (EMA) performances by the doping P into the surface shell WO3-δ compared with the Ni@WO3-δ. The experimental evidence combined with the theory calculation results based on First-principles revealed that the doping P into the WO3-δ endowed improvable electrical conductivity, resulting in higher conduction loss for the Ni@P-WO3-δ nanocomposites. Meanwhile, P doping causes more defects and distorted lattice for the WO3-δ shell, which enhances defect-induced polarization loss. As a result, enhanced conduction loss and polarization relaxation loss of the Ni@P-WO3-δ nanocomposites are dominant for improving EMA performance. Further, the study found that the EMA properties of the Ni@P-WO3-δ nanocomposites are related to P doping content and can be tailored efficiently by controlling the amount of P dopant source. Thus, the Ni@P-WO3-δ nanocomposites with appropriate P doping can optimize their balance between impedance matching and dielectric loss, achieving excellent microwave absorption performance. The minimum reflection loss (RL) value of the Ni@P-WO3-δ nanocomposites was − 55.62 dB, and the efficient absorption bandwidth achieved in 12.58 GHz, with a thickness rang of 1.61–5.00 mm. Therefore, this work confirms that doping engineering has a significant application for the design and synthesis of dielectric-typed microwave absorbers.

In Situ Synthesis of Heterostructured Fe–Ni Nanowires with Tunable Electromagnetic Wave Absorption Capabilities

In Situ Synthesis of Heterostructured Fe–Ni Nanowires with Tunable Electromagnetic Wave Absorption Capabilities

Carbon cloth based flexible electromagnetic wave absorbing materials loaded with Co3O4 array and tunable electromagnetic wave absorption performance

The demand for flexible electromagnetic wave (EMW) absorbing materials has increased, highlighting the importance of designing efficient and adaptable EMW absorbing materials. In this study, flexible Co3O4/carbon cloth (Co3O4/CC) composites with high EMW absorption properties were prepared via a static growth method and annealing process. The composites exhibited remarkable properties, with the minimum reflection loss (RLmin) and maximum effective absorption bandwidth (EAB, RL ≤ –10 dB) of –54.43 dB and 4.54 GHz, respectively. The flexible carbon cloth (CC) substrates exhibited outstanding dielectric loss due to their conductive networks. Moreover, the uniformly and tightly organized Co3O4 arrays on the flexible CC substrate played a crucial role in fine-tuning the impedance matching and facilitating abundant multiple scattering and interface polarization. This study proposes a promising approach to preparing flexible Co3O4/CC composites with a significant reference value for the field of flexible EMW.

Heterogeneous and hierarchical ni/C/SiO2 composite with tunable electromagnetic wave absorption

Structure design, conductivity regulation and electromagnetic matching are important to optimize the electromagnetic wave (EMW) absorbing properties. Therefore, exploring a strategy which kill these three birds with one stone is extraordinary. In this work, the heterogeneous and hierarchical Ni/C/SiO2 composite with tunable EMW absorption properties was synthesized through a simple calcination process. The introduction of SiO2 and Ni prompted a relatively large hole generated in the center of carbon fiber and formed hierarchical porous structure with the circumambient small holes which extended the propagation path of EMW, realized multiple reflection and scattering and endowed sufficient interfacial polarization. Meanwhile, the SiO2 and Ni nanoparticles played an important role in conductivity regulation and electromagnetic matching. Owing to the ingenious hierarchical porous structure and synergistic effect of multiple loss mechanisms, the Ni/C/SiO2-0.5 exhibited the optimal absorption properties with the maximum reflection loss (RL) of −47.65 dB at 3.1 mm with the filler content of 10 wt%. This research would provide a novel strategy for the exploitation route of the EMW absorbing materials.

Construction of 1D Heterogeneous Co/C@Ag Nws With Tunable Electromagnetic Wave Absorption And Shielding Performance.

In this study, silver nanowires (Ag NWs) are synthesized at first, and then the 1D heterogeneous Co/C@Ag NWs with a kebab- and popsicle-like microstructures are constructed by in situ growth ZIF-67 on Ag NWs combined with calcination. Results show that the EM wave prevention performance of composites depends on the loading of Co/C particles threaded on the Ag NWs. The popsicle-like structure with high Co/C loading gives Co/C@Ag NWs excellent EM wave absorption performance, which achieved a minimum reflection loss (RLmin ) of -44.5dB with a low filling of 30wt.% in paraffin; while the kebab-like structure with low Co/C loading shows good electromagnetic interference (EMI) shielding effectiveness (SET ) of 30.2dB at the same filler ratio. The enhanced EM wave absorption performance is attributed to the synergy of multiple energy dissipation mechanisms including dielectric loss, magnetic loss, polarization loss, eddy-current loss, multiple reflection loss, as well as proper impedance matching; the good EMI shielding performance is mainly due to the conduction loss brought by the Ag NWs with ultrahigh conductivity. This work provides a reference for the design of electromagnetic wave prevention material with tuned absorption and shielding performance.

Manipulation of Impedance Matching toward 3D-Printed Lightweight and Stiff MXene-Based Aerogels for Consecutive Multiband Tunable Electromagnetic Wave Absorption

Highly conductive MXene material exhibits outstanding dissipation capability of electromagnetic (EM) waves. However, the interfacial impedance mismatch due to high reflectivity restricts the application of MXene-based EM wave absorbing materials. Herein, a direct ink writing (DIW) 3D printing strategy to construct lightweight and stiff MXene/graphene oxide aerogels (SMGAs) with controllable fret architecture is demonstrated, exhibiting tunable EM wave absorption properties by manipulating impedance matching. Noteworthy, the maximum reflection loss variation value (ΔRL) of SMGAs is -61.2 dB by accurately modulating the width of the fret architecture. The effective absorption region (fE) of SMGAs exhibits consecutive multiband tunability, and the broadest tunable fE (Δf) is 14.05 GHz, which could be continuously tuned in the whole C- (4-8 GHz), X- (8-12 GHz), and Ku-bands (12-18 GHz). Importantly, the hierarchical structures and the orderly stacking of filaments endow lightweight SMGAs (0.024 g cm-3) with a surprising compression resistance, which can withstand 36 000 times its own weight without obvious deformation. Finite element analysis (FEA) further indicates that the hierarchical structure facilitates stress dispersion. The strategy developed here provides a method for fabricating tunable MXene-based EM wave absorbers that are lightweight and stiff.

Preparation of microcrystalline graphite/zinc ferrite composites with enhanced and tunable electromagnetic wave absorption using a high-temperature ball milling method

Microcrystalline graphite (MG)/zinc ferrite (ZFO) composites were prepared by a high-temperature ball milling method. The magnetic and microwave absorption properties of MG/ZFO composites were analyzed in the frequency range of 2.0–18.0 GHz. The results showed that MG has a favorable impact on the microwave absorption capacity of ZFO. The composites containing 10 wt% MG had a minimum reflection loss of −62.90 dB, which is almost a factor of 12 higher than for pure ZFO, and their effective absorption bandwidth (EAB, RL<−10 dB) covers frequency range of 5.84–7.92 GHz for a matching thickness of 3.9 mm, and for a matching thickness of 1.8 mm, the EAB covers frequency range of 12.87–17.70 GHz. A probable mechanism of microwave absorption for MG/ZFO composites is based on a synergistic combination of dielectric and magnetic losses. The attractive properties of prepared composites indicate that they are promising and competitive materials for use in microwave absorption.

Microstructure optimization strategy of ZnIn2S4/rGO composites toward enhanced and tunable electromagnetic wave absorption properties.

Although microstructure optimization is an effective strategy to improve and regulate electromagnetic wave (EMW) absorption properties, preparing microwave absorbents with enhanced EMW absorbing performance and tuned absorption band by a simple method remains challenging. Herein, ZnIn2S4/reduced graphene oxide (rGO) composites with flower-like and cloud-like morphologies were fabricated by a convenient hydrothermal method. The ZnIn2S4/rGO composites with different morphologies realize efficient EMW absorption and tunable absorption bands, covering a wide frequency range. The flower-like structure has an optimal reflection loss (RL) of up to -49.2 dB with a maximum effective absorption bandwidth (EAB) of 5.7 GHz, and its main absorption peaks are concentrated in the C and Ku bands. The minimal RL of the cloud-like structure can reach -36.3 dB, and the absorption peak shifts to the junction of X and Ku bands. The distinguished EMW absorption capacity originates from the uniquely optimized microstructure, complementary effect of ZnIn2S4 and rGO in dielectric constant, and synergy of various loss mechanisms, such as interfacial polarization, dipole polarization, conductive loss, and multiple reflections. This study proposes a guide for the structural optimization of an ideal EMW absorber to achieve efficient and tunable EMW absorption performance.

Investigation into wideband electromagnetic stealth device based on plasma array and radar-absorbing materials

Manipulation of electromagnetic waves is essential to various microwave applications, and absorbing devices composed of low-pressure gas discharge tubes and radar-absorbing materials (RAM) can bring new solutions to broadband electromagnetic stealth. The microwave transmission method is used to measure the physical parameters of the plasma unit. The designed structure exhibits superior absorption performance and radar cross-section (RCS) reduction capability in the 2–18 GHz band, with unique absorption advantage in the S and C frequency bands. It is found that the combination of the plasma and the RAM can significantly broaden the absorption frequency band and improve the absorption performance with excellent synergistic stealth capability. Experimental and simulation results present that broadband, wide-angle, tunable electromagnetic wave absorption and RCS reduction can be achieved by adjusting the spatial layout of the combined plasma layer and the type of RAMs, which creates opportunities for microwave transmission and selective stealth of equipment. Therefore, the wave manipulation by combined plasma array and RAM provides a valuable reference for developing numerous applications, including radar antenna stealth, spatial filter, and high power microwave shielding.

Controllable thermal treatment of reduced graphene oxide for tunable electromagnetic wave absorption performance

The complex process of reduced graphene oxide (RGO) preparation hindered its merits of lightweight, high surface area, and notable dielectric loss in electromagnetic (EM) wave absorption performance. This work introduced a controllable ethanol-assisted hydrothermal and annealing treatment to simplify the preparation of RGO with improved agglomeration and achieved tunable EM wave absorption performance. Among series of RGO materials fabricated with different annealing temperatures, the optimized RGO achieves a strong reflection loss of −49.9 dB with a thickness of 3.9 mm, and a broad effective absorption bandwidth of 7.65 GHz with a thickness of 3.1 mm based on a 2 wt% filler content in the matrix. The vacancy defect density and C/O ratio of RGO were demonstrated to be correlated to the behavior of conductive loss and polarization relaxation for RGO and the interface reflection of EM wave. This controllable thermal treatment successfully enabled the simple preparation of RGO with reduced agglomeration and tunable EM wave absorption and effectively contributed to fabricating other carbon-based dielectric/magnetic materials as high-efficiency electromagnetic absorbers in future.

Core-shell Ag@C spheres derived from Ag-MOFs with tunable ligand exchanging phase inversion for electromagnetic wave absorption

It has become greatly significant to achieve structurally tunable electromagnetic wave absorption materials (EMAs) derived from metal-organic frameworks (MOFs) via controllably continuous phase inversion. Herein, a series of core–shell Ag@C EMAs were successfully fabricated from Ag-MOFs via adjustable phase inversion. Replacing terephthalic acid (H2BDC) with 2-methylimidazole (Hmim) continuously led to the gradual transformation of Ag-MOF-5 structure into ZIF-L, which determined the crystal and morphological structure of Ag@C EMAs. In addition, due to the optimization of relaxation loss, the minimum reflection loss (RLmin) of S2 reached −50.14 dB with a thickness of 3.0 mm. The EMA derived from the original Ag-MOF had the widest absorption bandwidth (fE) of 5.44 GHz and RLmin of −47.36 dB at only 2.2 mm, respectively. This work can shed new light on the core–shell EMAs derived from phase inversion MOFs, and provide guidance to design novel high-performance EMAs.

A design of core-shell structure for γ-MnO2 microspheres with tunable electromagnetic wave absorption performance

Manganese dioxide (MnO2) has been widely utilized in the electromagnetic wave (EMW) absorption field because it exhibits numerous crystal types including α-MnO2, β-MnO2, γ-MnO2, and δ-MnO2, and is environmentally friendly. To enhance the EMW absorption performance of this material, we combined the precipitation method and calcination process to obtain γ-MnO2 microspheres, and developed a core-shell structure of γ-MnO2@SiO2 and γ-MnO2@SiO2@TiO2 microspheres via the sol-gel process. Based on the synergistic effects between the core-shell structure and dielectric loss, γ-MnO2@SiO2 with a thickness of 2.85 mm achieved the minimum reflection loss of −60.2 dB, demonstrating that these microspheres are excellent candidates for EMW absorbers.

Vertically aligned MnO2 nanostructures on carbon fibers with tunable electromagnetic wave absorption performance

Recently, electromagnetic wave (EMW) absorption materials with enhanced and tunable EMW absorption performance are required in practical applications, and attaining such performance by a simple method remains a vital challenge. In this study, manganese dioxide (MnO2) with controllable structures were vertically grown on carbon fibers (CF) through a hydrothermal method. The sheet-like (CF@MnO2-NS) and wire-like (CF@MnO2-NW) structures were obtained by merely adjusting the solution chemistries ([K+] and [H+]) and reaction time. The wire-like structure exhibited high attenuation capability due to a larger specific surface area and dielectric resonance, but exhibited a relatively poor impedance matching ratio resulting in inferior EMW absorption performance at low frequencies. However, the sheet-like structure exhibited better EMW absorption performance overall. The minimum reflection loss (RLmin) value of CF@MnO2-NS and CF@MnO2-NW reached −56.6 dB and −52.9 dB, respectively. Additionally, the EMW absorption performance varies with frequency. CF@MnO2-NW performed better in the X-band, while CF@MnO2-NS achieved an excellent performance in the C-band. This study provides a simple approach for designing EMW absorption materials with controllable morphologies and for realizing tunable EMW performances.

Morphology‐controlled preparation and tunable electromagnetic wave absorption performance of manganese dioxide nanostructures

AbstractThe development of electromagnetic wave (EMW) absorption materials with lightweight, wide absorption bandwidth, thin thickness, and strong EMW absorption performance has become a hotspot. Herein, the morphology‐controlled preparation of α‐manganese dioxide (α‐MnO2) was successfully obtained via a facile hydrothermal method, and the EMW absorption performance of α‐MnO2 was investigated in detail. The results indicated the as‐obtained Mn‐1.0‐120 possessed the best EMW absorption performance with minimum reflection loss of −53.43 dB at about 5.2 GHz with a thickness of 4.1 mm originated from the synergistic effects of multiply scattering, dielectric loss, and magnetic loss. This contribution demonstrates that the MnO2 has promising candidates with a tunable EMW absorption performance for applications in the electromagnetic field in the future.