Electromagnetic Wave Absorption Properties Research Articles

Electromagnetic wave absorption and mechanical properties of 3D-printed PLA composite reinforced with graphene and iron (III) oxide for X-band absorbers

Electromagnetic wave absorption and mechanical properties of 3D-printed PLA composite reinforced with graphene and iron (III) oxide for X-band absorbers

Orbital Hybridization Induced Dipole Polarization and Room Temperature Magnetism of Atomic Co‐N4‐C toward Electromagnetic Energy Attenuation

AbstractManipulating the electronic structure and geometric coordination environment of single metal atoms has been considered as promising approach for enhancing dipole polarization and enriching electromagnetic attenuation mechanisms. However, achieving precise control of the dielectric polarization response at atomic scale remains a huge challenge. Herein, a metal‐acetate coordination complexes‐assisted strategy is proposed to prepare spatially isolated cobalt (Co) atoms embedded in accordion‐like nitrogen‐doped carbon (NC) matrix. The interactions between metal atoms and NC matrix are carefully tailored through the successive evolution of dispersion states of Co species, ranging from individual atoms to atomic clusters to nanoparticles. Density functional theory reveals that the orbital hybridization between the d electrons of embedded Co atoms and p electrons of coordinated N atoms induces the electron redistribution at N sites, enabling enhanced electric dipole polarization and robust room temperature magnetism (a saturation magnetization of 0.108 emu g−1 at 300 K). Consequently, Co‐SAs@NC exhibits optimal electromagnetic wave absorption properties with a minimum reflection loss of ‐54.4 dB and an effective absorption bandwidth of 8.4 GHz. This work demonstrates an efficient strategy for modulating electromagnetic response at atomic level and provides a novel insight into the d/p electrons orbital hybridization between single metal atoms and NC species.

Heterogeneous interfaces in 3D interconnected networks of flower-like 1T/2H Molybdenum disulfide nanosheets and carbon-fibers boosts superior EM wave absorption

With the wide application of electromagnetic waves in national defense, communication, navigation and home appliances, the electromagnetic pollution problem is becoming more and more prominent. Therefore, high-performance, and low-density composite wave-absorbing materials have attracted much attention. In this paper, three-dimensional (3D) network structures of flower-like 1T/2H Molybdenum disulfide nanosheets anchored to carbon fibers (1T/2H MoS2/CNFs) were prepared by electrostatic spinning technique and calcination process. The morphology and electromagnetic wave absorption properties were tuned by changing the content of flower-like MoS2. The optimized 1T/2H MoS2/CNFs composite exhibits superior electromagnetic wave absorption with minimum reflection (RLmin) of −42.26 dB and effective absorption bandwidth (EAB) of 6.48 GHz at 2.5 mm. Multi-facts contribute to the super performance. First, the uniquely designed nanosheet and 3D interconnected networks leads to multiple reflection and scattering of electromagnetic waves, which promotes the attenuation of electromagnetic waves. Second, the propriate content of CNFs and MoS2 with different phase regulates its impedance matching characteristic. Third, Numerous heterogeneous interfaces existed between CNFs and MoS2, 1T and 2H MoS2 phase results in interface polarization. Besides, the 1T/2H MoS2 rich in defects induces defect polarization, improving the dielectric loss. Furthermore, the electromagnetic wave absorption performance was proved via radar reflectance cross section simulation. This work illustrates 1T/2H MoS2/CNFs is a promising material for electromagnetic absorption with wide bandwidth, strong absorption, low density, and high thermal stability.

Metal Single‐Atoms Toward Electromagnetic Wave‐Absorbing Materials: Insights and Perspective

AbstractMetal single‐atoms implanted on nitrogen‐doped carbon matrices (M‐NxCs) can effectively adjust local surface electrons and polarization relaxation through coordination structures to significantly enhance the electromagnetic wave (EMW) absorption properties of the materials. However, the precise construction of the geometric and electronic structures of metal single atoms and the discovery of the structure‐absorption relationship at the atomic level confront a huge challenge. Herein, this work summarizes the latest progress in metal single‐atom engineering of EMW absorbing materials via a comprehensive analysis of M‐NxCs in terms of design principles, modulation strategies, and structure‐performance correlations. Subsequently, it highlights the recent progress of several typical M‐NxCs as the EMW absorbing materials, aiming to achieve a complete understanding of the physical effects and atomic‐level absorption mechanisms. Finally, current key challenge and future directions of M‐NxCs are presented by focusing on the electromagnetic functional materials. This work provides new insights for the development of atomically dispersed absorbing materials for efficient electromagnetic response functionalities.

Laser‐induced self‐propagating synthesis and electromagnetic wave absorption properties of MoAlB powders

AbstractMoAlB powders with a purity of 96 wt.% were successfully fabricated by a laser‐induced self‐propagating method using molybdenum boride (MoB) and aluminum powders as starting materials under the conditions of an n(MoB): n(Al) ratio of 1.0:1.4 and the laser linear energy density (El) of 0.9 J/mm, and the effect of raw material composition and El on the phase composition and microstructure of the resultant MoAlB powders were investigated. The minimum reflection loss (RLmin) value and effective absorption bandwidth (EAB) of the as‐prepared MoAlB absorber with a thickness of 5.0 mm were only determined as −12.5 dB (at 16.9 GHz) and 0.9 GHz (16.4–17.3 GHz) in the frequency of 1–18 GHz, respectively. Nevertheless, the RLmin and EAB of as‐prepared MoAlB powders oxidized after 3 h at 773 K increased to −18.59 dB (at 15.82 GHz) and 2.13 GHz (15.22–17.35 GHz), respectively, demonstrating that the as‐prepared MoAlB powders are potential candidates for high‐temperature microwave absorption applications. This study proposes a new efficient strategy for the preparation of boron‐based ternary compounds for high‐temperature electromagnetic wave absorption application.

Research on electromagnetic wave absorption properties of Portland cement

In order to evaluate the electromagnetic wave absorption properties of Portland Cement, the chemical composition, mineralogical phase of Portland cement were studied by XPS, XRD and Mössbauer, respectively, and electromagnetic parameters were measured. Afterwards, the reflectivity of the hydrated cement were tested.The results showed that Portland cement exhibits some dielectric loss and weak magnetic loss at 1∼18 GHz, due to the unburned carbon and iron oxide. There are three notable theoretical electromagnetic wave absorption peaks, and the greatest absorption reaches 4.38 dB. The minimum reflectivity of hydrated Portland cement reach -17.9 dB, -17.89 dB and -12.67 dB and the bandwidth of -6 dB reach 6.28 GHz,10.74 GHz and 1.85 GHz at the thickness of 5 mm,10 mm, 15 mm, respectively. There are 3,5,7 reflectivity peaks at the thickness of 5 mm,10 mm, and 15 mm, respectively, which matched very well with the calculated interference peaks.

Electromagnetic wave-absorbing of polymer derived rod-like ZrB2 ultrahigh-temperature ceramic composites

Ultra-high temperature ceramics (UHTCs) are candidates that can be used in extremely high temperature environments relative to the Si-based ceramic due to their excellent high-temperature performance. However, there are few researches on the electromagnetic wave absorption of the UHTCs themselves. In this work, rod-like ZrB2 and its composites were prepared by polymer derived method at a lower temperature. The phase composition and electromagnetic wave absorption properties of the ceramics at different pyrolyzed temperatures were analyzed. The rod-like ZrB2 pyrolyzed at 1500 °C shows a RLmin of −54.77 dB at a thickness of 4.7 mm. The rod-like ZrB2/SiC has an absorption bandwidth of 5.68 GHz (RL <-10 dB, 7.6–13.28 GHz) at a thickness of 4.25 mm, exceeding the X-band. An absorption bandwidth of 2.24 GHz for RL <-20 dB (99% absorbed) was obtained by the fabricated composites. The strong absorption of rod-like ZrB2/SiC composites is due to the strong conductive loss and multiple scattering of electromagnetic wave by the rod-like network structure. The formation of core-shell ZrB2/SiC increases the polarization and enhance the electromagnetic wave absorbing properties of the ceramics. The results of this study show that the polymer derived UHTCs have the strong ability to absorb electromagnetic wave.

Doped Porous Carbon Spheres with Controllable Vesicle Structure: Preparation and the Effects of Pore Size on Electromagnetic Wave Absorption Properties.

This work reports on the preparation of uniform vesicle-structural carbon spheres doped with heteroatoms of N, P, and S, with the pore sizes strictly controlled by the hard templates of monodisperse submicron SiO2 spheres. The uniformly doped vesicular carbon microspheres are obtained in three steps: Stöber hydrolysis for the SiO2; in situ polymerization for the immobilization; and alkaline etching after carbonization. The size of the vesicles can be easily adjusted by regulating the particle size of the submicron SiO2 spheres, which has a significant effect on its electromagnetic wave (EMW) absorption performance. Compared with microspheres with pore sizes of 180 and 480nm, when the vesicle aperture is 327nm, with only 5.5wt.% filling load and 1.9mm thickness, the material shows the best EMW absorption behavior with the effective absorption bandwidth (EAB) covers the entire Ku band (6.32GHz) and the minimum reflection loss (RLmin) of -36.10dB, suggesting the optimized pore size of the microspheres can significantly improve the overall impedance matching of the material and achieve broadband wave absorption. This work paves the way for the enhancement of EMW absorption properties of porous material by optimizing the pore size of uniform apertures while maintaining their composition.

Well-Dispersed CoNiO2 Nanosheet/CoNi Nanocrystal Arrays Anchored onto Monolayer MXene for Superior Electromagnetic Absorption at Low Frequencies

Developing microwave absorbers with superior low-frequency electromagnetic wave absorption properties is one of the foremost important factors driving the boom in 5G technology development. In this study, via a simple hydrothermal and pyrolysis strategy, randomly interleaved CoNiO2 nanosheets and uniformly ultrafine CoNi nanocrystals are anchored onto both sides of a single-layered MXene. The absorption mechanism demonstrated that the hierarchical heterostructure prevents the aggregation of MXene nanoflakes and magnetic crystallites. In addition, the introduction of the double-magnetic phase of CoNiO2/CoNi arrays can not only enhance the magnetic loss capacity but also generate larger void spaces and abundant heterogeneous interfaces, collectively promoting impedance-matching and furthering microwave attenuation capabilities at a low frequency. Hence, the reflection loss of the optimal absorber (M–MCNO) is −45.33 dB at 3.24 GHz, which corresponds to a matching thickness of 5.0 mm. Moreover, its EAB can entirely cover the S-band and C-band by tailoring the matching thickness from 2 to 7 mm. Satellite radar cross-section (RCS) simulations demonstrated that the M–MCNO can reduce the RCS value to below −10 dB m2 over a multi-angle range. Thus, the proposed hybrid absorber is of great significance for the development of magnetized MXene composites with superior low-frequency microwave absorption properties.

Ultra-wideband electromagnetic wave absorption property with bimetallic Co6W6C/carbon

Binary dielectric materials, particularly carbide/carbon composites, have garnered considerable attention for their promising electromagnetic wave (EMW) absorption property. In this work, bimetallic carbide and carbon composite (Co6W6C/C) was successfully prepared through hydrothermal method and pyrolysis process. Characterization results reveal the growth of Co6W6C nanoparticles on two-dimensional carbon nanosheets. The mass ratio of glucose (C6H12O6) to Co6W6C was found to significantly impact the EMW absorption performance. When 150 mg C6H12O6 and 100 mg CoWO4 were added, the CWCC-2 composite exhibited an ultra-high effective absorption bandwidth of 7.49 GHz (10.51–18 GHz). In the far-domain circumstance, the highest radar cross-section acreage reached 21.24 dB m2. The exceptional EMW absorption performance can be attributed to the synergistic effects of impedance matching, electrical losses, and magnetic losses. The Co6W6C/carbon composite, synthesized through a facile approach, showcases a broad electromagnetic wave absorption bandwidth, paving the way for a breakthrough in materials science with wide-band and high-efficiency absorption capabilities.

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.

Optimizing the electromagnetic wave absorption properties of core-shell Fe/FeN/Fe3C@GN nanoparticles by low-temperature NH3 plasma

Surface modification via low-temperature plasma has an extensive application prospect in different engineering fields due to its comprehensive merits in facilitating the introduction of functional groups and creating more heterogeneous interfaces. Herein, a simple high-temperature plasma method is developed to get novel multiple-phase nanocomposites of core-shell Fe/FeN/Fe3C@GN nanoparticles with bifunctional characteristics of microwave absorption (MA) and anti-corrosion. And then, we further investigate the MA properties of Fe/FeN/Fe3C@GN nanoparticles after low-temperature NH3 plasma etching. It is found that surface modification of Fe/FeN/Fe3C@GN nanoparticles can generate remarkable changes in specific surface areas, Raman features and MA properties of these nanocomposites. The Fe/FeN/Fe3C@GN nanoparticles after NH3 plasma etching possess excellent MA properties with an optimal reflection loss (RL) of −51.0 dB at an ultra-thin thickness of 1.9 mm with a low filling content of 30 wt% and the corresponding effective absorption bandwidth (EAB < −10 dB) up to 4.7 GHz (13.3–18.0 GHz). The fascinating MA properties of etched Fe/FeN/Fe3C@GN nanoparticles may be attributed to the cooperative effect of several points: (i) The NH3 plasma etch introduces a large number of polar functional groups, which can be regarded as the polarization center to produce more polarization loss; (ii) The appropriate dielectric loss and impedance matching achieve a good balance, and the abundant heterogeneous interface significantly enhances the polarization relaxation loss; (iii) The existence of hetero-nanostructure further improves the multiple reflections and scattering of the propagating microwaves. In addition, this work provides a new strategy for the design and fabrication of core-shell MA materials.

Effect of nano-carbon black content and dispersibility on the properties of cement paste

In this study, we analyzed the microstructure, pore structure, and changes in electromagnetic parameters of cement paste with nano-carbon black (CB) added. The following conclusions were drawn: The addition of CB significantly influenced the pore structure of the cement paste, increasing the content of pores less than 100 nm and improving the overall pore structure. The use of the dispersant further enhanced the dispersion of CB and increased its filling effect. Additionally, adding CB had a significant impact on the compressive strength of the cement paste; the presence of certain CB aggregates reduced the compressive strength. However, when the CB content was 0.5wt%, the use of the dispersant decreased the size of CB aggregates and effectively increased the compressive strength. SEM images displayed the dispersion state of CB aggregates within the cement paste, demonstrating that the size and quantity of aggregates could be reduced through the use of the dispersant. The change in the CB dispersion state also slightly affected the electromagnetic parameters and wave absorption properties of the cement paste. The research results presented in this paper offer valuable insights for the design and application of CB cement paste.

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.

Mesoporous silica@polypyrrole and its epoxy composites with ultra-broadband electromagnetic wave absorption properties

Composite of powders with exceptional electromagnetic wave absorption (EMA) properties with resins is an important tactic for preparing electromagnetic wave (EMW) stealth composites. However, high expenditure, low yield and the complex synthesis of these powders constrain their utilization in composite materials. Moreover, composite materials need greater thickness to fulfill EMA requirements. This work reported a facilely producible absorber, mesoporous Silica@Polypyrrole (MSU-J@PPy), which exhibits enhanced EMA performance. The polymerization of PPy in the connected three-dimensional pores as well as on the surface of MSU-J led to the creation of conductive network thereby enhancing the conductive loss. MSU-J contributes to the lightweighting and impedance matching and promotes the formation of a non-homogeneous interface. By varying the ratio of PPy to MSU-J, precise control of EMA was realized. When the proportion of PPy to MSU-J by weight is 1.5:1, the reflection loss (RL) of MSU-J@PPy reaches an impressive −46.44 dB at 1.9 mm. The effective absorption bandwidth (EAB) is 6.08 GHz (11.92–18 GHz) at 2.1 mm thickness of the sample. Further, MSU-J@PPy and carboxylated multi-walled carbon nanotubes (cMWCNTs) was composited with epoxy resin (EP) to develop a wave-absorbing composites MSU-J@PPy/cMWCNTs/EP with ultra-broadband absorption properties and outstanding mechanical characteristics. At a thickness of 1.7 mm, the composite can effectively absorb EMW in the entire Ku band, and effective absorption across the 5.4–18 GHz range can be attained through changing the matching thickness. This work offers a novel approach for developing cost-effective, easily synthesized, and high-yield EMW absorbers, as well as their application in absorber composite materials.

Multi-Interface Electromagnetic Wave Absorbing Material Based on Liquid Marble Microstructures Anchored to SEBS.

The direct application of liquid marbles in electromagnetic wave (EMW) absorption is challenging due to their poor stability, susceptibility to gravitational collapse, and shaping difficulties. To address this issue, a novel strategy is proposed to incorporate liquid marble microstructures (NaCl/nano-SiO2) encapsulated in organic phases (Octadecane) into the rubber-matrix (SEBS) using the ultrasound-assisted emulsion blending method. The resulting NaCl/SiO2/Octadecane microstructures anchored to SEBS offer a substantial solid-liquid interface consisting of NaCl solution and SiO2. When subjected to an alternating electromagnetic (EM) field, the water molecules and polysorbate within SiO2 exhibit heightened responsiveness to the EM field, and the movement of Na+ and Cl- within these microstructures leads to their accumulation at the solid-liquid interface, creating an asymmetric ion distribution. This phenomenon facilitates enhanced interfacial polarization, thereby contributing to the material's EMW absorption properties. Notably, the latex with 16wt% SEBS (E-3), exhibiting a surface morphology similar to human cell tissues, achieves complete absorption of X-band (fE=4.20GHz, RLmin=-33.87dB). Moreover, the latex demonstrates light density (0.78gcm-3) and environmental stability. This study not only highlights the predominant loss mechanism in rubber-based wave-absorbing materials but also provides valuable insights into the design of multifunctional wave-absorbing materials.

Interfacial modulation of SiC/TiC hybrid nanofibers for fabricating flexible ceramic electromagnetic wave absorbers

Titanium Carbide (TiC), characterized by its hardness, conductivity and thermal stability, can serve as a suitable additive phase for SiC nanofibers. TiC phase can improve the flexibility and electromagnetic wave absorption property of SiC nanofibers without sacrificing its high-temperature thermal stability. Herein, flexible SiC/TiC hybrid nanofibers with different Ti contents were fabricated by electrospinning and precursor infiltration pyrolysis. The introduction of Ti can not only generate conductive TiC phase, but also act as a catalyst to regulate the growth of SiC grains, so as to adjust the flexibility and electromagnetic properties of the hybrid nanofibers. At the optimal Ti precursor content of 4 wt%, the SiC/TiC-4 hybrid nanofibers exhibit a broad effective absorption bandwidth of 4.5 GHz with the thickness of 1.6 mm. The flexible SiC/TiC hybrid nanofibers This work can provide a reference for the design of flexible ceramic nanofiber absorbers and is expected to enable practical application in high temperature conditions.

Broadband electromagnetic wave absorption properties of RGO cement-based composite

In this study, a cement-based composite was prepared using reduced graphene oxide (RGO) as a raw material via an ethanol liquid-phase mixing pre-dispersion process. The microstructure of cement-based composites with varying RGO contents was discussed, and a systematic investigation was conducted into the electromagnetic wave absorption (EWA) performance of RGO-cement composites within the frequency range of 2–18 GHz. The results indicate that the RGO content significantly impacts its wave absorption performance. Notably, at an RGO content of 3.0 wt%, the wave absorption performance experiences substantial enhancement. For instance, the minimum reflection loss (RLmin) of −48.33 dB at 8.9 GHz with a coating thickness of 2.6 mm is achieved, while an effective absorption bandwidth (EAB) of 5.02 GHz is attained with a thickness of only 1.6 mm, covering nearly the entire Ku-band. The incorporation of high specific surface area RGO into cement materials results in abundant interface polarization losses and additional electromagnetic wave transmission paths, effectively boosting the EWA performance. Consequently, these materials exhibit significant potential for applications in the field of electromagnetic wave shielding.

Intercalation of AlCl3 in microcrystalline graphite via high-temperature mechanochemical method for electromagnetic wave absorption

Given their distinct microstructure, Graphite intercalation compounds (GICs) provide significant application potential in the field of electromagnetic wave absorption (EMWA). Herein, microcrystalline graphite (MG) and AlCl3 were employed to fabricate xAlCl3-yMGIC powders via a novelty high-temperature mechanochemical method (HTMC). The impact of AlCl3 addition on the microstructure and EMWA properties, the possible EMWA mechanisms of the xAlCl3-yMGIC powder, were thoroughly evaluated additionally. The results demonstrate that the intercalation of AlCl3 can significantly improve the EMWA properties of the raw MG. Furthermore, the EMWA properties of the xAlCl3-yMGIC powders can be tuned by adapting the AlCl3 contents and the matching thickness. Among them, when the mass ratio of MG to AlCl3 is 1:1 and a sample filling ratio of only 15 wt%, the minimum reflection loss (RLmin) of the AlCl3-MGIC powders attains −37.6 dB at 9.52 GHz and a matching thickness of 1.6 mm, covering an effective absorption bandwidth (EAB, RL < -10 dB) of 8.56 − 10.62 GHz. This work presents an innovative concept for the high-value application of MG in the domains of EMWA and the short-process preparation of GICs.

Thermal insulated C/SiC nanofiber aerogel with high thermal stability and superior electromagnetic wave absorption performance

Integration of thermal insulation and electromagnetic wave absorption was crucial in stealth technology and hypersonic vehicles but challenging. Herein, silicon carbide nanofibers were synthesized by in situ chemical vapor deposition within a carbon foam skeleton to form a wave absorbing and heat insulating integrated composite aerogel with a hierarchical porous structure. The unique hierarchical porous structure provided an excellent platform for the absorption of electromagnetic waves, achieving a minimum reflection loss (RLmin) of −51.46 dB at 17.20 GHz. Meanwhile, the C/SiC nanofiber aerogel maintained a low density of 0.013 g/cm3, an ultra-low thermal conductivity of 0.030 W/(m⋅K) and a high thermal stability up to 1000 °C. Furthermore, to enhance the electromagnetic wave (EMW) absorption property of the aerogel, polypyrrole (PPy) was coated on the surface of C/SiC nanofiber aerogel by facile impregnation and chemical polymerization. The multiple conductor-semiconductor-conductor structure of C/SiC-PPy composite aerogel leads to various EMW loss mechanisms and excellent impedance match, resulting in an outstanding EMW absorption performance, with a RLmin of −60.31 dB at 2.96 GHz.