Tunable Electromagnetic Wave Research Articles

Hierarchical Assembly of Ternary MOF-Derived Sandwich Composites for High-Efficiency Tunable Electromagnetic Wave Absorption.

The proliferation of electronic devices drives the adoption of electromagnetic wave (EMW) absorbing materials to mitigate electromagnetic pollution. Metal-organic frameworks (MOFs) reveal great potential in EMW absorption field due to their unique pore structure and outstanding physicochemical properties. However, single MOFs are difficult to achieve both efficient absorption and wide frequency coverage owing to the limited electromagnetic properties and structural composition. Herein, a sandwich-like ternary MOF composite is successfully synthesized through a hierarchical assembly strategy. Following high-temperature treatment, the materials are converted into nitrogen-doped porous carbon with magnetic metals, non-magnetic metal oxides, and carbon nanotubes on the surface (labeled as TiO2/C@Co/N/C@CNT). The unique sandwich structure of the resulting derivatives provides a multi-level microstructure and multi-component synergistic effects, significantly enhancing electromagnetic wave absorption capabilities and broadening the effective absorption bandwidth (EAB). At 1.8 mm matching thicknesses, the material achieves a reflection loss of -56.3 dB and a 6.6 GHz EAB. Adjusting the matching thicknesses to 2.3 and 3.1 mm extends the EAB to 6.1-18 GHz, with absorption peaks of -47.6 and -47.1 dB. This work offers a novel guidance for constructing advanced MOF-derived materials with ultra-broadband EAB and strong EMW absorption through meticulous structural design and multiple components combination.

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

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

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.

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

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

Porous-multilayered Ti3C2Tx MXene hybrid carbon foams for tunable and efficient electromagnetic wave absorption

The rapid development of modern wireless communication technology makes electromagnetic wave pollution increasingly serious, necessitating the development of high-performance electromagnetic wave-absorbing materials. This study introduces a Ti3C2Tx MXene hybrid carbon foam (HCF) that exhibits a tunable and efficient electromagnetic wave absorption performance. The HCF features a porous, multilayered structure, which enhances its multi-reflection properties, and a heterogeneous interface between the carbon foam and MXene boosting its dielectric loss. By regulating the content of MXene, the ratio of polarization loss to conduction loss can be regulated to achieve better impedance matching. As a result, the HCF demonstrated superb electromagnetic wave absorption performance with RLmin = −72.25 dB and EABmax = 6.55 GHz. Furthermore, the minimum absorption frequency domain could be tuned within 8–14 GHz by varying the MXene content. The performance in radar wave absorption and electromagnetic-thermal conversion (ramp rate 85.81 °C/s from RT to 200 °C) proves that HCF is an efficient and reliable electromagnetic wave absorber, suitable for radar technology, microwave heating, and communication systems applications.

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.

Ferrite doped sucrose-derived porous carbon composites inspired by Pharaoh's Serpent for broadband electromagnetic wave absorption

This paper presents a straightforward and intriguing approach for designing wide bandwidth, lightweight, and tunable electromagnetic wave (EMW) absorbing materials. Drawing inspiration from the "Pharaoh's Snake", biomass carbon source and sucrose were used to fabricate Fe/Fe3O4@porous carbon (PC) composite materials through combustion experiments. Subsequently, high-temperature calcination was applied to enhance the microwave absorbing properties of the materials. The as-prepared composites demonstrate an impressive 6.62 GHz effective bandwidth and an excellent absorption ability of −51.54 dB at a matched thickness of 2.2 mm. Moreover, by tuning the content of magnetic particles and controlling the thickness of the composite material, comprehensive coverage across C, X, and Ku bands can be achieved. The outstanding performance suggests that the synthesized Fe/Fe3O4@PC porous materials hold significant potential for applications in electromagnetic wave absorption. It opens up a novel, straightforward, and cost-effective approach to acquiring broadband absorbing materials.

Dual Cross‐Linked Magnetic MXene Aerogel with High Strength and Durability Enables Multifunctionality

AbstractThe construction of lightweight yet robust, durable magnetic transition metal carbides and/or nitride (MXene) aerogels is highly desired for assembling high‐performance, multifunctional architectures. However, the fabrication and application of magnetic MXene aerogels is severely restricted by their inferior mechanical strength and poor water/oxygen resistance. Here, sustainable cellulose nanofibrils (CNFs) are employed for assisting in the physical and chemical dual cross‐linking to strongly bind the MXenes and MOF‐derived magnetic nanoparticles. The dual‐crosslinked magnetic MXene aerogels (D‐MMAs) achieve a density as low as 12 mg cm−3, and acquire a significantly improved mechanical strength of up to 1311% over physically crosslinked ones, as well as remarkably improved hydrophobicity, and oxidation stability. Furthermore, the multifunctional integration of efficient and tunable electromagnetic wave (EMW) absorption, remarkable photothermal conversion, thermal insulation, prominent oil‐water separation, thin/thick oil and dye absorption capability, and the remote magnetic controllability is accomplished. Notably, the D‐MMA performs a maximum absorption intensity of −63.9 dB, and accomplishes a specific reflection loss of −1105 dB mm−1, comparable to the best MXene‐based EMW absorbers ever reported. Given its facile, scalable, and sustainable manufacturing approach, the multifunctional D‐MMAs hold great application prospects in various fields of next‐generation electronics, special equipment protection, defense, and aerospace.

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.

Rare earth Ce-doped W-type barium ferrites for tunable electromagnetic waves absorption performance

W-type ferrites possessing low cost and high chemical stability, show high potential in electromagnetic wave (EMW) absorption field. However, due to the low dielectric loss, developing high EMW absorption performance of W-type ferrites remains desired. Here, rare earth (RE) cerium (Ce)-doped W-type barium ferrites (Ba1-yCeyNi2Fe15.4O27, y = 0.1, 0.2, 0.3, 0.4, 0.5, 0.6) are prepared by a sol-gel approach. The influences of Ce doping are detailed analyzed. Ce ions with unpaired 4f electrons and strong spin-orbit coupling of angular momentum enhance the dielectric and magnetic properties of ferrites. Ba0.7Ce0.3Ni2Fe15.4O27 achieves the minimum reflection loss (RLmin) value of -52 dB while Ba0.6Ce0.4Ni2Fe15.4O27 showcases the widest effective absorption bandwidth (EAB) of 1.36 GHz associated with the RLmin reaching -38 dB, significantly outperforming the undoped ferrites. This work thus demonstrates a high-efficiency utilization of Ce for enhancing the EMW absorption performance of widely employed W-type barium ferrites, efficiently advancing the application field of RE elements.

Synthesis of Hierarchical CF@Fe3O4 Fibers Decorated with MoS2 Layers Forming Core-Sheath Microstructure toward Tunable and Efficient Electromagnetic Wave Absorption.

Hierarchical structural design has been verified as a feasible strategy to fabricate effective electromagnetic wave (EMW) absorbers, so we designed hierarchical core-sheath composites with magnetic particles and dielectric layers. In this work, a hierarchical structure of carbon fiber (CF)@Fe3O4@MoS2 (CPDF7-M) was prepared by introducing Fe3O4 and depositing MoS2 layers on the surface of fibers. Due to the synergistic effects from the CF@Fe3O4 increasing the conductive and magnetic loss and the outer MoS2 layers improving the impedance matching, the optimal reflection loss (RL) value was -63.1 dB at 2.7 mm and the effective absorption bandwidth (EAB) was 9.1 GHz covering the X and Ku band. Moreover, the EAB values were adjusted with a specific MoS2 loading at different thicknesses, which provided the necessary reference for the construction of efficient and flexible absorbers in the EMW absorption fields.

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.

Electron irradiation modified point defects of SiC nanoparticles with tunable high electromagnetic wave absorption

Silicon carbide nanoparticles (SiC nps) were modified by changing the injection amount using 1 MeV high-energy electron as radiation source. When the injection volume reaches 5ⅹ1013 cm−2, the irradiated particles produce defect structures sufficient to optimize the electromagnetic wave absorption performance. With the increase of beam amount, the value of g detected by electron paramagnetic resonance (EPR) energy spectrum moves towards the silicon suspension bond, and the macroscopic electromagnetic wave absorption peak gradually moves towards the low frequency, accompanied by the enhancement of absorption intensity and the increase of absorption bandwidth. When the injection volume reaches 3ⅹ1014 cm−2, the loss value of −62.79 dB is achieved at the optimal thickness of 2.56 mm, and the absorption frequency band covers the entire Ku band. SiC presents point defects, and carbon atoms leave the original lattice position due to electron irradiation, forming carbon vacancies, resulting in uneven charge distribution inside the material, resulting in dipoles of orientation polarization, which further affects the electromagnetic wave absorption performance. As the irradiation dosage increases, the defects become denser and purer. This leads to higher electromagnetic wave absorption intensity and a correspondingly lower optimal absorption frequency. Thus, the modification of SiC nps through irradiation achieves tunable absorbers.

Multiphase Interfacial Regulation Based on Hierarchical Porous Molybdenum Selenide to Build Anticorrosive and Multiband Tailorable Absorbers

HighlightsThe hierarchical porous structure is regulated by various species of PVP to achieve impedance matching.Interfacial engineering boosts conductivity and constructs a multiband (C, X, Ku) tunable electromagnetic wave absorber.Hierarchical porous molybdenum selenide/epoxy coating exhibits marine anticorrosion capability.

Magneto-Mechanical Metamaterials: A Perspective

AbstractMagneto-mechanical metamaterials possess unique and tunable properties by adjusting their shape configurations in response to an external magnetic field. Their designs and functionalities are diverse and are utilized in a wide variety of applications, such as highly tunable elastic and electromagnetic wave filters and targeted shape morphing. In this perspective, we examine the general background of magneto-mechanical metamaterials and their diverse applications. The possible future directions in the field are also thoroughly discussed.

Thermally tunable electromagnetic surface waves supported by graphene loaded indium antimonide (InSb) interface

The thermal agitation plays a vital role in tunability of optoelectronic, structural and chemical characteristics of the temperature sensitive materials. Graphene enables the THz optics, due to its unprecedent controlling characteristics over the traditional materials. The influence of temperature on the monolayer graphene is very negligible due to its low free charge carrier density, to enhance the thermal sensitivity of graphene, the graphene loaded temperature sensitive material interface has been proposed. A theoretical analysis has been carried out on temperature dependent propagation characteristics of electromagnetic surface waves supported by the graphene loaded semi-infinite indium antimonide (InSb). The InSb has been taken as temperature sensitive material. The Drude model has been used for the modeling of InSb in the THz region while the modeling of the graphene has been done by random phase approximation-based Kubo’s formulism. To realize the graphene loaded indium antimonide interface, the impedance boundary conditions (IBCs) have been employed. The numerical analysis has been conducted to analyze the influence of temperature on the characteristics of electromagnetic surface waves i.e., dispersion curve, effective mode index (Neff), penetration depth (δ), propagation length (Lp), phase speed (Vp) and field profile, propagating along the graphene loaded InSb. In all the numerical results, the temperature variation has been considered from 200 to 350 K. It has been concluded that the graphene–InSb interface provides more temperature assisted tunability to the interfacial surface modes, commonly known as surface waves, as compared to monolayer graphene. Further, the graphene parameters can play a vital role in the dynamical tuning of electromagnetic surface waves in THz to IR frequency range. The numerically computed results have potential applications in designing of thermo-optical waveguides, temperature assisted communication devices, thermo-optical sensors and near field thermal imaging platforms.

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.

Tunable and efficient electromagnetic wave absorption of carbon material modulating magnetic ionic polymer-based composites

Developing the miniaturization and intellectualization of carbon-based chips and electronic devices is extremely desirable but remains hampered by electromagnetic interference. Magnetic ionic polymer (MIP) holds great promise for electromagnetic-absorbing material in the field of electromagnetic reliability of communication equipment due to its dielectric loss and magnetic loss are obviously higher than other commonly polymers. However, it remains a formidable challenge for MIP to achieve satisfactory absorption of electromagnetic wave (EMW). Herein, we achieved the excellent EMW absorbing performance of the poly[1-allyl-3-vinylimidazolium tetrachloroferrate]/carbon nanotube/reduced graphene oxide (P[AVIm][FeCl4]/CNT/rGO) composites when the only carbon materials loading of 10 wt%. Most strikingly, the effective absorption bandwidth (EAB) is as wide as 5.63 GHz, the lowest reflection loss can reach up to −51.05 dB with the absorber thickness of 2.2 mm. The enhancement in microwave absorption efficiency of P[AVIm][FeCl4]/CNT/rGO composites are arisen from the synergistic effects in its unique multicomponent heterostructure interface, which causes multiple reflections and strong conduction loss, further suitable impedance matching ratio and favorable attenuation ability. This work proposes a new perspective approach and fundamental absorption mechanisms to realize excellent performance EMW absorption.