Excellent Electromagnetic Wave Research Articles

The hollow cubic octahedral structure of Fe3O4 with excellent electromagnetic wave absorption capacity

The unique nanostructure combined with high dielectric and magnetic losses is essential for electromagnetic wave (EMW) attenuation in microwave-absorbing materials (MAM). In this paper, using cubic octahedral Cu2O as a template, we synthesized hollow cubic octahedral Fe(OH)3 at first. After annealing at 450 °C, the hollow cubic octahedral structure Fe3O4 could be obtained. When the filling ratio was 40 %, the minimum reflection loss (RLmin) reached -66.08 dB, and the maximum effective absorption bandwidth (EAB) was 5.38 GHz at a thickness of 1.84 mm, exhibiting improved EMW properties compared with previous works. The hollow cubic octahedral structure of Fe3O4 enhances EMW absorption characteristics, which is attributed to abundant dipole polarization, interface polarization, and good conduction loss. These results indicate that Fe3O4 with the hollow cubic octahedral structure can be used as potential candidates for efficient and broadband EMW absorbers.

Screw dislocation growth defects enhancing electromagnetic wave absorption performance of GdB6

In this study, a purity of up to 98.36 wt. % GdB6 with screw dislocation growth morphology were successfully fabricated using an in-situ reaction approach. The terraced-like structure of the GdB6 enhanced the interfacial polarization and multiple interface scattering of the electromagnetic waves. As a result, the as-obtained high purity GdB6 powder presented superior electromagnetic wave absorption performance. The minimum reflection loss value can be −49.24 dB at the frequency of 13.12 GHz with a thin matching thickness of 1.44 mm. In addition, the widest effective absorption bandwidth can be up to ∼4 GHz (14–18 GHz) with a thin matching thickness of 1.25 mm. The remarkable electromagnetic wave absorption performance of GdB6 ceramics could be attributed to conductance loss and polarization loss enhanced by the screw dislocation growth defects, as well as synergistic effects with magnetic loss. The as-obtained GdB6 with synergistic dielectric loss and magnetic loss is to be a novel single-phase with excellent electromagnetic wave absorbing material, which will pave the way on the investigation of rare earth hexaborides for the ultra-high temperature environment applications.

Rice straw-inspired tunable multi-hollow channel parallel carbon fibers for enhanced electromagnetic wave absorption

The pure carbon materials are constrained in practical applications due to their inability to meet the requirements of broadband and strong absorption. To address this challenge, inspired by the parallel connection structure of hollow straw, this study successfully fabricated a multi-hollow channel parallel carbon fibers (MHCFs) structure by electrospinning and carbonization template methods. Compared with the traditional non-porous carbon fibers (CFs) structure (MHCFs-0), MHCFs-0.2 exhibit more excellent electromagnetic wave (EMW) absorption performance. It exhibits an impressive 5.59 GHz effective absorption bandwidth (EAB) at 1.8 mm. The reflection loss (RL) of MHCFs-1 reaches −52.64 dB. This remarkable enhancement in performance can be attributed to the channel structure, which can effectively introduce air, optimize impedance matching, and greatly promote polarization effects (including interface polarization and dipole polarization). It is worth noting that the integration of computer simulation technology (CST) with material structure design in this study opens up new ideas for the preparation of absorbing materials and the design of micro-nano structures, holding significant practical implications.

Excellent dielectric response and microwave absorption in magnetic field-induced magnetic ordered structures

Weak interactions prevent the magnetic particles from achieving excellent electromagnetic wave absorption (EMA) at a low filler loading (FL). The construction of one-dimensional magnetic metal fibers (1D-MMFs) contributes to the formation of an electromagnetic (EM) coupling network, enhancing EM properties at a low FL. However, precisely controlling the length of 1D-MMFs to regulate permittivity at low FL poses a challenge. Herein, a novel magnetic field-assisted growth strategy was used to fabricate Co-based fibers with adjustable permittivity and aspect ratios. With a variety of FL changes, centimeter-level Co long fibers (Co-lf) consistently exhibited higher permittivity than Co particles and Co short fibers due to the enhancement of the effective EM coupling. The Co-lf exhibits excellent EMA performance (–54.85 dB, 5.8 GHz) at 10 wt.% FL. Meanwhile, heterogeneous interfaces were introduced to increase the interfacial polarization through a fine phosphorylation design, resulting in elevated EMA performances (–51.50 dB, 6.6 GHz) at 10 wt.% FL for Co2P/Co long fibers. This study improves the orderliness of the particle arrangement by regulating the length of 1D-MMFs, which affects the behavior of electrons inside the fibers, providing a new perspective for improving the EMA properties of magnetic materials at a low FL.

Cationic pre-insertion interlayer engineering of manganese dioxide for highly efficient electromagnetic wave absorption

Interlayer engineering of two-dimensional structural materials provides unique advantages for tuning the electromagnetic properties of metal oxides, injecting unlimited energy into the design of advanced two-dimensional metal oxide electromagnetic wave absorbers. In this study, Manganese dioxide intercalated with alkali metal ions was prepared by a simple molten salt method. The pre-intercalation of ions not only enhances the polarization loss at the heterogeneous interface between cations (point sites) and manganese dioxide (face sites) but also alters the energy band structure of manganese oxide and enhances its electrical conductivity, which in turn enhances the conductive loss of the manganese dioxide. Due to the synergistic effect of multiple polarizations and conductive losses, NaMO exhibits superb electromagnetic wave absorption properties and an effective absorption bandwidth of 5.36 GHz at thinner matched thicknesses. In addition, the RCS simulation result further verifies the excellent electromagnetic wave absorption capability of NaMO. Under the positive incidence of electromagnetic waves, the electromagnetic wave reflection intensity of the metal plate coated with NaMO is effectively reduced. Finally, this work establishes a new way to modulate the electromagnetic properties.

Heterogeneous interface engineering of SiBCN/Ni fibers extends enhanced electromagnetic wave absorption properties

Faced with severe electromagnetic wave (EMW) pollution, the development of high-performance EMW absorbers remains a formidable challenge. In this study, SiBCN/Ni fibers containing uniformly dispersed Ni2Si nanoparticles were synthesized by electrospinning method with polymer-derived ceramics method, and their electromagnetic properties were evaluated. The low permeability threshold of the fibers ensures sufficient conduction loss effect. The in situ grown Ni2Si nanoparticles provide a magnetically coupled network, which is more conducive to obtaining excellent impedance matching. Furthermore, the presence of β-SiC, SiO2, and Si2N2O generates numerous heterogeneous interfaces (e.g., C-SiC and C-Ni2Si), leading to enhanced interfacial polarization through the accumulation of charges. As a result, the prepared SiBCN/Ni fibers exhibit impressive EMW absorption properties. At a Ni content of 1 wt%, the effective absorption band (EAB) is 4.32 GHz (13.68–18 GHz). At a Ni content of 1.5 wt%, the minimum reflection loss (RLmin) is −52.98 dB, and the sample has excellent radar scattering capabilities, which is verified by CST Microwave Studio simulations. Therefore, SiBCN/Ni fibers are promising as excellent EMW absorbing materials in practical applications.

Molecular Intercalation‐Induced Two‐Phase Evolution Engineering of 1T and 2H‐MS2 (M = Mo, V, W) for Interface‐Polarization‐Enhanced Electromagnetic Absorbers

AbstractPolarization at interfaces is an important loss mechanism for electromagnetic wave (EMW) attenuation, though the motion behavior of carriers in interfaces composed of different types of conductors has yet to be investigated. Tuning the phase structure of transition metal dichalcogenides (TMDs) MS2 (M = Mo, V, W) by organics small molecule intercalation to achieve the modulation of interfacial types is an effective strategy, where 1T‐MS2 exhibits metallic properties and 2H‐MS2 has semiconducting properties. To exclude the contribution of the intrinsic properties of TMDs materials, three TMDs (MoS2, VS2, and WS2), which also possess phase transitions, are investigated. Among them, the 1T‐MS2 composite exhibits excellent EMW absorption performance under the synergistic effect of interfacial polarization and conduction loss. 1T‐MoS2/MOF‐A exhibits the best EMW absorption performance with an RLmin of −61.07 dB at a thickness of 3.0 mm and an EAB of 7.2 GHz at 2.3 mm. The effectiveness of the modulation of the interfacial polarization using 1T‐phase and 2H‐phase MS2 is demonstrated, which is important for the analysis of the carrier motion behavior during the interfacial loss.

(Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98/biocarbon composite: A broad band and highly efficient electromagnetic wave absorber

The combination of carbon and magnetic materials have drawn extensive attention for microwave absorption. In this study, high-performance microwave absorbing materials are prepared by direct mechanical mixing (Zn0.6Ni0.3Cr0.1)1.02(Fe2O4)0.98 (ZnNiCrFeO) with leaf biocarbon. After mixing with biocarbon, the magnetic materials present decent micro-wave reflection loss. Especially, the minimum reflection loss value of −41.08 dB is achieved. The excellent conductivity of biocarbon, magnetic loss of ZnNiCrFeO, and interface polarization loss (between ZnNiCrFeO and biocarbon) jointly determined the electromagnetic absorbing performance. The appropriate impedance matching as well as the synergetic effect between the biocarbon and ZnNiCrFeO magnetic material are also considered. These achievements light the way to prepare low-cost microwave absorbents with excellent electromagnetic wave absorbing performances, utilizing the leaf as precursors.

Enhanced electromagnetic wave absorption of magnetite-spinach derived carbon composite

The high density, high cost, and environmental pollution hinder the application of iron-based electromagnetic wave-absorbing materials. Although bio-carbon is a green and lightweight dielectric wave-absorbing material, the wave-absorbing performance of bio-carbon is still limited. This work successfully combined magnetite Fe3O4 with porous carbon derived from spinach stem using hydrothermal and calcination methods. This process optimizes the matching of the dielectric constant and magnetoconductivity of the as prepared composite material, resulting in a significant improvement in electromagnetic microwave absorption capacity. XRD, SEM, TEM, XPS, VSM and EMW absorption network analyzer are used to detect and characterize the samples. The composite material shows a excellent minimum reflection loss value of −48.81 dB and an efficacious absorption bandwidth of 4.73 GHz at the optimal raw material ratio. The tests also show the porous structure of the sample with the coercivity and saturation magnetization of 29.36 Oe and 10.75 emu/g, respectively. The test results indicate that the excellent electromagnetic wave absorption is due to the synergistic effect of multiple reflection, Debye relaxation, and interfacial polarization. This Fe3O4-bio-carbon composite is cheap and simple to prepare, and it also has excellent wave absorption performance. Therefore, it shows great application potential in civilian and military electromagnetic wave absorption fields.

Silica coated MOFs-derived composites with excellent electromagnetic wave absorption and corrosion resistance

The microwave absorber with excellent corrosion resistance is an ideal layer for stealth applications in marine environments. Silica coated MOF-derived anti-corrosion absorbers were successfully fabricated by the Stöber method. The resulting powder demonstrated excellent performance not only in microwave absorption but also in corrosion resistance. The effective absorption bandwidth (EAB) of coated-12 reached 4.1 GHz and the minimum reflection loss (RLmin) came to −59.8 dB at 15.18 GHz in a 1.3 thickness with an 80 wt% filling ratio. The outstanding absorption performance is put down to the matched impedance and the various loss mechanism synergy. Besides, the electrochemical corrosion test revealed that the compact silica coating protected the inner corrodible magnetic metal nanoparticles from the outer corrosive environment. This work provides a reasonable and feasible method for synthesizing an excellent microwave absorber suitable for harsh environments.

Optimization of three dimensional rGO@MWCNTs/Fe3O4-PVA composite film through regulated structure for convenient and replaceable electromagnetic wave absorption material

Optimizing the composition and structure of polymers and carbon nanomaterials to obtain composite films with excellent mechanical and electromagnetic wave (EMW) properties is an excellent solution for exploring EMW absorbing materials. In this work, a flexible composite film with a regular three-dimensional network structure was designed and prepared. The modified rGO@MWCNTs/Fe3O4-PVA composite nanofilm with optimized composition and structure has a multi-component heterogeneous interface, three-dimensional network structure. The composite film has high EMW absorption performance, excellent flexibility, mechanical strength and stability, and can be used in a wide range of application scenarios. At a thickness of 2.8 mm, the effective absorption bandwidth (fE) reaches 3.72 GHz, the minimum reflection loss (RLmin) is -48.99 dB, and the tensile stress reaches 32 MPa. This work realizes the regulation of the mechanical properties and EMW absorbing properties of the composite film, and provides an efficient and stable flexible composite EMW absorbing material.

Phase structure-induced amplification of interfacial polarization loss for excellent electromagnetic wave absorption

The development of multicomponent dielectric composites has emerged as a predominant approach to achieving exceptional electromagnetic (EM) wave absorbers. However, elucidating the intrinsic characteristics and absorption mechanism for EM wave absorbers poses significant challenges due to the intertwined discussion of electromagnetic loss with dipole polarization loss, defects/interfacial polarization, and conductive loss, among others. To address this issue, manganese selenide (MnSe) nanocrystals with different phase structures are synthesized successfully by the thermal injection decomposition method, including star-shaped α-MnSe nanocrystals and tetrapod-shaped γ-MnSe nanocrystals, which were combined with rGO layers to form α-MnSe/rGO composites and γ-MnSe/rGO composites. Through controllable phase structure, tune the interfacial charge transfer and establish the link between interfacial polarization and EM wave absorption. Owing to the boosted interfacial polarization loss provided by the star-shaped α-MnSe nanocrystals and rGO layers, α-MnSe/rGO composites harvest an RLmin of −62.4 dB (2.7 mm) and a broad bandwidth of 7.52 GHz at 2.9 mm. This study successfully breaks through the limitations of conventional component design, establishing a robust correlation between phase structure/interfacial polarization and electromagnetic wave dissipation capability. These findings provide valuable insights for developing advanced materials with enhanced electromagnetic wave absorption properties.

Microstructure and EMW absorption properties of PDCs-SiCN(Ti) ceramics with adjustable SiC nanowires and TiC nanocrystallines

Herein, a novel type of ceramic material exhibiting tunable electromagnetic properties was synthesized using the polymer-derived ceramics (PDCs) method. The precursor employed in this process was a tetrabutyl titanate-modified polysilazane, which ultimately led to the formation of PDCs-SiCN(Ti) ceramics. High-temperature annealing (1400 °C-1500 °C) was used to prepare PDCs-SiCN(Ti) ceramics, which exhibited a unique dual nanostructure comprising SiC nanowires and TiC nanocrystals and served as effective nanoabsorbents. The SiC and TiC contents are closely related to the annealing temperature and induced Ti content. After annealing at 1500 °C, the PDCs-SiCN(Ti) ceramics with the typical A + B + C electromagnetic absorbing structure exhibited excellent electromagnetic wave (EMW) absorption properties. The PDCs-SiCN(Ti) ceramics, with a Ti content of 5 wt%, demonstrated an effective absorption bandwidth (EAB) of 3.8 GHz, which encompassed 90.5 % of the X band, despite having a relatively thin impedance matching thickness of only 2.1 mm. The outstanding EMW attenuation capability of the PDC-SiCN(Ti) ceramics can be ascribed to their large specific surface area and defects combined with the high permittivity of dispersed TiC nanocrystals, which facilitates multiple reflections of EMW within the SiCN matrix. Therefore, this work provides a controllable preparation method for PDCs-SiCN(Ti) ceramics with various microwave absorbing phases.

High-performance electromagnetic wave absorption by two-dimensional mesoporous monolayer Ti3C2Tx MXene

Transition metal carbide MXene, with its unique chemical composition, structure and sizeable particular surface area, is widely applied in wave absorption. However, the high conductivity of MXene resulted in an impedance mismatch that prevented electromagnetic waves from entering the material to achieve dissipation, and thus, tuning the intrinsic properties of pure MXene to obtain excellent electromagnetic wave absorption is still a challenge. Here, we strengthen the absorption of electromagnetic waves by generating titanium vacancies through hydrogen peroxide etching and thus forming micro-sized wrinkles with porous MXene. Porous MXene possesses an excellent microstructure and surface state, abundant porous defects, and moderate electrical conductivity, allowing it to achieve well-matched impedance, dipole polarization, and conduction loss, thus inheriting excellent electromagnetic wave absorption (EWA) properties. Therefore, the porous MXene achieves a strong absorption of − 63.31 dB and an adequate absorption bandwidth (EAB) of 6.88 GHz at a matched thickness of 2.39 mm with a fill ratio of 6 wt%.

Porous CoZn@NC skeletons supported NiCo2S4 nanorods for efficient electromagnetic wave absorption

Bimetallic sulfides are promising in electromagnetic wave (EMW) absorption due to their moderate permittivity and high dielectric loss. However, the impedance mismatching and insufficient loss mechanism of bimetallic sulfides result in limited EMW absorption performance. Herein, bimetallic sulfide (NiCo2S4) nanorods were loaded onto nitrogen-doped carbon embedded with CoZn nanoparticles (CoZn@NC) derived from CoZn-based metal organic framework (CoZn-MOF) through simple hydrothermal and vulcanization processes. Importantly, during the vulcanization process, CoZn@NC undergoes structural reorganization and evolves into defect-rich porous nanosheets, which promotes dipole polarization and enhance EMW absorption ability. Additionally, the formed NiCo2S4 nanorods are tightly anchored on the porous CoZn@NC skeletons, forming a large number of heterostructures, and promoting interfacial polarization. In addition, the carbon nanotubes (CNTs) formed during the pyrolysis process of CoZn-MOF contribute to the conduction loss of the heterostructure and motivate dielectric loss. Therefore, CoZn@NC/NiCo2S4 heterostructures inherit excellent EMW absorption performance and obtain a reflection loss (RL) value of −32.53 dB at a matching thickness of 2.1 mm, while exhibiting an effective absorption bandwidth (EAB) of 4.1 GHz. Radar cross-sectional area (RCS) simulation shows that the potential of CoZn@NC/NiCo2S4 heterostructure in practical anti radar detection. This work puts up great potential for the development of advanced bimetallic sulfides-based EMW absorbers.

Reduced Graphene Oxide Modified Nitrogen-Doped Chitosan Carbon Fiber with Excellent Electromagnetic Wave Absorbing Performance.

Lightweight and low-cost one-dimensional carbon materials, especially biomass carbon fibers with multiple porous structures, have received wide attention in the field of electromagnetic wave absorption. In this paper, graphene-coated N-doped porous carbon nanofibers (PCNF) with excellent wave absorption properties were successfully synthesized via electrostatic spinning, electrostatic self-assembly, and high-temperature carbonization. The obtained results showed that the minimum reflection loss of the absorbing carbon fiber obtained under the carbonization condition of 800 °C is -51.047 dB, and the absorption bandwidth of reflection loss below -20 dB is 10.16 GHz. This work shows that carbonization temperature and filler content have a certain effect on the wave-absorbing properties of fiber, graphene with nanofiber, and the design and preparation of high-performance absorbing materials by combining the characteristics of graphene and nanofibers and multi-component coupling to provide new ideas for the research of absorbing materials.

Hollow core–shell Co@SiO2@PPy composites with efficient electromagnetic wave absorption

In this study, hollow Co@SiO2@PPy composites with excellent electromagnetic wave (EMW) absorption performance were successfully synthesized. The monodisperse hollow Co microspheres were prepared using a solvent-thermal method. The microspheres were then coated with an SiO2 layer by a modified Stöber method. Finally, the SiO2 layer was surface-coated by polypyrrole (PPy) through in-situ polymerization to obtain Co@SiO2@PPy composite materials with hollow core–shell structures. The prepared CSP2 composite achieved a minimum reflection loss (RLmin) of −65.83 dB at 1.86 mm, demonstrating an effective absorption bandwidth (EAB) of 4.84 GHz. The CSP3 composite achieved a widest EAB (EABmax) of 5.4 GHz at a thickness of 1.83 mm, while simultaneously maintaining the RL level at −50.70 dB. Additionally, it demonstrated an RLmin value of −61.66 dB with a thickness as thin as 1.66 mm. The observed shift of FTIR absorption peaks by 20 cm−1 in the PPy ring provides compelling evidence for the involvement of multilayered structures in polarization loss. The SiO2 layer not only enhances the interface polarization but also prevents corrosion of the Co core by acidic solutions. The exceptional EMW absorption characteristics can be attributed to the effective impedance matching and the combined effect of magnetic and dielectric losses.

Facile preparation of ZIF-8/ZIF-67-derived biomass carbon composites for highly efficient electromagnetic wave absorption

Biomass absorbing materials have received increasing attention for electromagnetic wave (EMW) absorption field absorbing materials due to its low density and high dielectric loss. However, the biomass EMW absorbing materials often suffer from the insufficient magnetic loss and impedance matching. In this work, a facile ZIF-8/ZIF-67-derived biomass composites (CoZnO@BPC) was prepared for high-performance EMW absorption based on multi-component micro, nano structures metal particles and xanthoce sorbifolia bunge shells-derived biomass porous carbon (BPC). The dielectric loss and/or magnetic loss abilities of CoZnO@BPC composites were adjusted by changing the mass ratio of Zn2+ to Co2+ ions. Under the filled amount of 20 wt%, CoZnO@BPC exhibited excellent EMW absorption with the minimum reflection loss (RL) at 15.84 GHz is -50.2 dB, and the matching thickness is only 1.7 mm. By adjusting the ZIFs mass ratio, the effective absorption bandwidth (EAB) can be up to 5.92 GHz (from 12.08 GHz to 18 GHz), and the matching thickness is only 1.9 mm. The results provide a new insight for the economical and efficient preparation of lightweight and advanced microwave absorbing materials.

In situ construction of efficient electromagnetic function Graphene/PES composites based on liquid phase exfoliation strategy

Although graphene nanosheets (GNs) with huge specific surface area and exceptional electrical properties exhibit attractive practical prospect in the realm of electromagnetic function materials, how to optimize the distribution states of GNs in matrix is still a challenge. In this work, the suspension of GNs was prepared directly via an efficient liquid-phase exfoliation (LPE) process in N-octyl-2-pyrrolidone (NOP). Thanks to the dissolution of polyether sulfone (PES) in NMP and NOP solvent, the GNs/PES composites were in-situ prepared via a facile solution blending in combination with evaporation process. The “function units” of the mesoscopic micro-cluster structure assembled by GNs during the solvent evaporation process contribute to optimized impedance matching characteristics and loss capabilities as well as excellent electromagnetic wave (EMW) absorbing performance of the as-constructed GNs/PES electromagnetic composites. Particularly, the as-prepared sample G-P-9 with a graphene content of as low as 9.0 wt% exhibits outstanding EMW absorbing performance in the whole ranges of tested frequency (8.2–12.4 GHz) and temperature (293–453 K) with a minimum reflection loss (RL) of −52.7 dB. Besides, the in-situ self-assemble GNs/single-walled carbon nanotubes (GNs/SWCNT) film with pre-constructed three-dimensional interpenetrating conductive network exhibits excellent electromagnetic interference (EMI) shielding effectiveness (SE) of about 5.1 × 104 dB cm2 g−1. The present approach would be applicable to construct high-performance electromagnetic functional materials and broaden the application prospect of high-integrity graphene nanosheets.

The Ag based composites derived from Ag-MOFs with tunable forms for electromagnetic wave absorption

The wireless communication and network technology make our lives more and more convenient. However, the inevitable electromagnetic pollution and interference deriving from these technologies have hazardous influences on the electronic equipment and human health. Therefore, continuous explorations have been strived to fabricate excellent electromagnetic wave (EMW) absorbers to diminish the impact of these negative effects. MOF, as an emerging hybrid material is widely investigated as the EMW absorber due to its multiple attenuation mechanisms. However, attentions are always focused on the influence of different inorganic ions and organic linkers on the electromagnetic wave absorption (EMWA) performance of MOF. Significantly, tremendous facts have proved that the control of morphologies and forms of hybrid materials is vital for further enhancement of many applications. Hence, the investigation of effect of MOF forms on EMWA performance will be the important foundation for further explorations. Here, three different forms of Ag based MOFs, named Ag-MOF, Ag-MOF-Microcrystal and Ag-MOG were successfully fabricated. Further investigations of XPS, XRD as well as FT-IR manifested that these three materials had the same coordination behaviors. The different forms could be obtained by the controlling of crystallization. Ag-MOG was proved to be the best EMW absorber among the fabricated materials. The minimum RL of −41.8 dB and a wider EAB of 6.3 GHz could be obtained by Ag-MOG derived composite.