Electromagnetic Absorption Properties Research Articles

Electromagnetic absorption properties of composite mortar with graphene and manganese-zinc ferrite

Electromagnetic wave absorption of building structures plays a crucial role in safeguarding information and mitigating electromagnetic radiation. This study delves into the absorption capabilities of composite mortar made with graphene (GR) and manganese-zinc ferrite (MFO) across frequencies of 1−18 GHz. The mechanical strength, microstructural examinations, and numerical simulations to elucidate the underlying mechanisms of wave absorption in the composite mortar are investigated. The results indicate that incorporating 30% MFO reduces the strength of mortar due to its low bonding capacity and diluting effects, whereas GR enhances the strength of mortar by facilitating cement hydration. Electromagnetic examinations reveal that MFO boosts the magnetic loss performance, while GR augments dielectric loss properties. In addition, the presence of needle, rod, mesh, and flake hydration products in the pores of composite mortar also contributes to increased wave depletion. According to the simulation of electromagnetic absorption based on the finite difference time domain (FDTD) method, the composite mortar with GR and MFO exhibits a superior performance of electromagnetic wave absorption. With the 25 mm thickness of composite mortar with 30% MFO, an absorption below -10 dB, covering a bandwidth of 1.68−4.34 GHz are obtained, with a peak reflection loss of -22.13 dB at 3.23 GHz. Thus, by combination magnetic loss of MFO, dielectric loss of GR, and the reflective capabilities of porous mortar, a composite mortar with a better electromagnetic wave absorption can be achieved.

Computations of fields induced in biological tissues by electromagnetic (EM) wave in multilayered structure

The assessment of the fields induced in biological tissue by an electromagnetic (EM) wave is a major issue, not only for its relevance in medical research, but also for its implications on the setting of industrial standards. This paper describes the analysis of electromagnetic (EM) absorption properties of biological multilayered structure. The biological structure comprises three different tissues of skin, fat and muscle. A step-by-step approach for the computation of the EM fields within the multilayered structure is presented. The estimated specific absorption rate (SAR) distribution in tissues due to exposure from plane waves of frequencies 433, 900, 1300, 1800, and 2450 MHz, based on an incident power density 4.5 [mW/cm2], are also presented.

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

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

Evolution of high temperature oxidation properties of SiCf/SiCN composites with BN interphase

In this study, SiC/SiCN composites with BN interphase were prepared using chemical vapor infiltration (CVI) and polymer infiltration and pyrolysis (PIP) methods. The evolution and related mechanisms of mechanical and microwave absorption properties of the composites after oxidation at 800 °C, 1000 °C, 1200 °C, and 1400 °C were investigated. The results showed that with the elevating of oxidation temperature, the flexural strength of SiC/SiCN composites gradually decreased, with a retention rate of 56.7 % after oxidation at 1400 °C. The main reasons for the deterioration of mechanical properties were the changes in the crystal structure of SiC fibers under high-temperature conditions and the formation of brittle SiO2 phases on the surface and interior of the SiCN matrix. With the increase in oxidation temperature, the microwave absorption performance of the composites showed an enhancing trend. The main reasons were that after oxidation treatment, the reduction of free carbon content and the formation of SiO2 film layers from the oxidation of SiC and SiCN led to a decrease in the complex permittivity of the composites, resulting in better impedance matching and dielectric loss capabilities. The contributions of BN interphase to stress dispersion, interface polarization, and oxidation protection significantly enhance the mechanical and electromagnetic absorption properties of the composites. Therefore, SiC/SiCN composites are high-temperature structural microwave absorbing materials with great application prospects.

Zirconium-modified hierarchical porous SiC-based nanofibrous aerogel with efficient electromagnetic waves absorption and thermal insulation properties

Supersonic aircraft require materials that can offer both thermal insulation and electromagnetic wave (EMW) absorption capabilities to facilitate flight operation in extremely high-temperature environments. Herein, zirconium modified SiC-based nanofibrous aerogels (ZSNFAs) with hierarchical pore stucture were prepared by electrospinning combined with carbothermal reduction reaction. The introduction of Zr formed a high-conductivity ZrC phase inside the fiber and significantly increased its conductivity loss, while the growth of SiC nanowires constructed a hierarchical porous structure within the aerogel, which not only promoted the interfacial polarization and multiple reflection losses of EMWs, but also impeded heat transfer and improved the compressive strength of the aerogel. The obtained ZSNFA demonstrated high mechanical robustness (∼0.32 MPa), low thermal conductivity (0.023–0.024 W·m−1·K−1), and superior EMW absorption performance (at 2 % Zr content, the minimum reflection is –60.72 dB and effective bandwidth of 4.5 GHz at 2.8 mm thickness), making it suitable for utilization in complex high-temperature environments.

Study on the electromagnetic properties and microwave absorption properties of Co2Si by non-magnetic metal Cu and Mn single doping

In this study, Co2Si and Co2Si-doped powder materials with different Cu,Mn proportions were prepared by mechanical alloying and thermal sintering. The effects of Cu,Mn doping on the crystal structure, magnetic properties, and microwave absorption properties of Co2Si were investigated. The results showed that all the sample peaks obtained by XRD measurement were consistent with the standard card (ICDD: 98–005–2281) of Co2Si.The Ms values corresponding to 2 at%, 4 at%, and 8 at% Cu doping were 25.79 emu/g, 23.79 emu/g, and 21.75 emu/g, respectively. The saturation magnetization of Co2Si samples doped with 2 at%, 4 at% and 8 at% Mn was 8.26 emu/g, 20.33 emu/g and 14.65 emu/g, respectively.The doping of Cu significantly improved the comprehensive absorption performance of Co2Si alloy, and the lowest reflection loss was obtained when Cu was doped with Co2Si alloy, with an RLmin value of -67.61 dB and an EAB of 2.40 GHz. The comprehensive absorption performance of Mn doped Co2Si was also improved, and the RLmin value of Mn doped with 4 at% was -67.04 dB, and the EAB was 2.39 GHz.This is because that the small Co2-xMxSi (M=Cu,Mn) alloy can produce multiple reflection and scattering effects, which increase the propagation path of the electromagnetic wave and optimize the impedance matching characteristics of the material.

Laser irradiation induced CoNi@carbon composites as high-performance microwave absorbers

Metal-organic-frameworks (MOFs) derivatives, known for their lightweight and high-performance properties, are highly sought after as microwave absorbers. However, most reported MOFs derived absorbers are pyrolyzed in tube furnaces, which is time-consuming and difficult to finely tune the microstructure due to the low heating-quenching process. In this study, laser irradiation was used as a heat source to pyrolyze CoNi ZIF. By controlling the irradiation power (30 mW, 50 mW), Co/C composites were obtained in just a few seconds, with Co nanocrystals ranging from 10 to 50 nm. The presence of Ni could modulate the microstructure and electric-magnetic parameters of Co/C composites. The effects of Ni content and irradiation power on the electromagnetic absorption properties of Co/C were analyzed. Considering the enhanced dipolar/interfacial polarization, matched impedance, and strong magnetic coupling network, a minimum reflection loss of −45 dB with the effective absorption bandwidth of 6 GHz can be achieved by Co/C at the thickness of 2 mm. Additionally, the laser irradiation was performed in air atmosphere, providing an effective way for industrial production of high-efficiency and broadband wave-absorbing materials.

Preparation of cellulose derived carbon/reduced graphene oxide composite aerogels for broadband and efficient microwave dissipation

The development of cellulose derived carbon-based composite aerogels with light weight, broad bandwidth and strong absorption remains a challenging task. In this work, the cellulose derived carbon/reduced graphene oxide composite aerogels were prepared by a two-stage process of chemical crosslinking and high-temperature carbonization. The results revealed that the as-fabricated binary composite aerogels had a unique lightweight characteristic and three-dimensional porous network structure, which was chemically crosslinked by epichlorohydrin. Furthermore, the weight concentration of graphene oxide (GO) had a notable influence on the electromagnetic parameters and microwave absorption properties of the composite aerogels. The obtained binary composite aerogel possessed the optimal microwave dissipation capability when the concentration of GO was 1.5 mg/mL. Remarkably, the minimum reflection loss reached −50.42 dB at a thickness of 2.47 mm and a filling ratio of 17.5 wt%. Concurrently, the composite aerogel with a comparable thickness of 2.73 mm showed a wide effective absorption bandwidth of 7.28 GHz, spanning the total Ku-band and extending into a portion of the X-band. The radar cross section contribution of binary composite aerogels in the far-field was also simulated by computer simulation technique. In addition, the potential microwave attenuation mechanism was proposed. It was believed that the results of this paper would offer a reference for the preparation of cellulose derived carbon-based composite aerogels as efficient and broadband microwave absorbers.

Preparation and electromagnetic absorption properties of silver-decorated polystyrene with frequency-selective surfaces

Preparation and electromagnetic absorption properties of silver-decorated polystyrene with frequency-selective surfaces

Enhancing mechanical properties of cementitious composites by boron nitride nanosheets modified carbon fiber

Carbon fiber (CF) is commonly employed to enhance the mechanical properties, electrical conductivity, and electromagnetic absorption properties of cementitious composites. However, its weak interfacial bonding with the matrix limits its application in such composites. In this study, boron nitride (BN) nanosheets were synthesized via the solid-state reaction and used to modify CF surface. The flexural and compressive strengths of cementitious composites incorporating BN nanosheets coated CF (BN@CF) increased by 18.45 % and 29.38 %, respectively, with CF doping at only 0.2 wt%. Isothermal calorimetry and TGA results revealed that BN nanosheets on CF surface would provide nucleation sites for the formation of C–S–H and CH. The microstructure and bonding properties of BN@CF were characterized using SEM/EDS, FTIR, XPS, finite element analysis, and single fiber pullout test. The results showed that the significant improvement of interfacial properties between the fiber and the matrix contributed to the increase of mechanical properties of cementitious composites. These findings provide an effective strategy for the strength development of CF-reinforced cementitious composites.

Manipulating polarization attenuation in NbS2–NiS2 nanoflowers through homogeneous heterophase interface engineering toward microwave absorption with shifted frequency bands

Homogeneous heterogeneous (heterophase) interfaces regulated with low energy barriers have a fast response to applied electric fields and could provide a unique interfacial polarization, which facilitate the transport of electrons across the substrate. Such regulation on the interfaces is effective in modulating electromagnetic wave absorbing materials. Herein, we construct NbS2–NiS2 heterostructures with NiS2 nanoparticles uniformly grown in NbS2 hollow nanospheres, and such particular structure enhances the interfacial polarization. The strong electron transfer at the interface promotes electron transport throughout the material, which results in less scattering, promotes conduct ion loss and dielectric polarization relaxation, improves dielectric loss, and results in a good impedance matching of the material. Consequently, the absorbing band may be successful tuned. By regulating the amount of NiS2, the heterogeneous interface is finely alternated so that the overall wave-absorbing performance is shifted to lower frequencies. With a NiS2 content of 15 ​wt% and an absorber thickness of 1.84 ​mm, the minimum reflection loss at 14.56 ​GHz is −53.1 ​dB, and the effective absorption bandwidth is 5.04 ​GHz; more importantly, the minimum reflection loss in different bands is −20 dB, and the microwave energy absorption rate reaches 99% when the thickness is about 1.5–4.5 ​mm. This work demonstrates the construction of homogeneous heterostructures is effective in improving the electromagnetic absorption properties, providing guideline for the synthesis of highly efficient electromagnetic absorbing materials.

Microwave-Assisted Hydrothermal Synthesis of Nanosheet Layered Hexagonal Spinel Ferrites for Efficient Electromagnetic Wave Absorbing.

A microwave-induced combustion method has been utilized to prepare nanosized powders of hexagonal spinel ferrites using urea and glycine as fuel. The structural and electromagnetic absorption of these products was investigated using X-ray diffraction (XRD). From the (3,1,1) and (1013) peaks in XRD measurements, it was seen that the samples we synthesized were nanosized spinel and y-phase hexagonal ferrite. In addition, Fourier-transform infrared measurements showed that the synthesized samples had high absorption values showing Fe-O, which is between 878 to 4000 cm-1, and metal-oxygen transitions, which are between the 700 and 2500-3000 cm-1 in the spinel and hexagonal phases. From the scanning electron microscope image of the particles, it is seen that they are homogeneous, filled structures with ∼35-40 nm. It appears from vector network analyzer measurements that the synthesized 1.5 mm thick composite materials have very high electromagnetic absorption properties and that these composites can also be used in electromagnetic interference, Wi-Fi applications, and health.

Dual-modified catalytic core-shell structure biomass carbon cotton fiber extends broadband electromagnetic waves absorption applications

Using vacuum impregnation method, the biomass carbon cotton fiber material was modified with polymer-derived SiCN ceramics and different Ni sources to successfully prepare the composite material. The electromagnetic microwave absorption properties of the material in the range of 2–18 GHz and the catalytic effect of different nickel sources were studied. The material modified by nickel nitrate hexahydrate forms a carbon fiber coated structure, improves impedance matching, enriches heterostructures, and increases electromagnetic synergistic loss, effectively enhancing the effective absorption bandwidth (EAB) reaches 4.72 GHz, the minimum reflection loss (RLmin) is −47.79 dB, and the thickness is only 1.32 mm. The results of CST show that the radar cross section of CFPN-2 material is −36.86 dB m2, and it has obvious effect of optimizing impedance matching.

Customized heterostructure of transition metal carbides as high-efficiency and anti-corrosion electromagnetic absorbers

The ever-increasing presence of electronic devices and communication equipment imposes a critical demand for the development of highly efficient microwave absorption materials, as a means to combat the detrimental effects of electromagnetic (EM) wave pollution. The extraordinary advantages offered by heterointerface and defect engineering, coupled with their distinctive electromagnetic traits, infuse boundless energy into the development of MXene-based absorbers for EM attenuation. However, there is still a lack of understanding regarding the consequences of irreversible oxidation on the surface chemistry and dielectric properties of MXenes. Through the employment of heterointerface engineering strategy to promote interfacial charge accumulation and polarization, remarkable EM absorption properties coupled with corrosion resistance have been realized. The partially oxidized MXenes, particularly Ti3C2Tx and V2CTx, displayed remarkable reflection loss (RL) values of −56.83 dB and −52.13 dB, respectively. Additionally, the Nb2CTx composites showcased exceptional performance, offering a significantly broader bandwidth of 9.84 GHz. By conducting an extensive examination of the structural changes in MXenes, this work aims to elucidate the oxidation mechanisms and proposes a feasible method for producing MXenes with excellent absorption properties.

Synthesis of mulberry-like Fe nanoparticles assembly by nano-spheres and its excellent electromagnetic absorption properties

Synthesis of mulberry-like Fe nanoparticles assembly by nano-spheres and its excellent electromagnetic absorption properties

Fabrication of multifunctional Co,N co-doped UIO-rGO aerogel with properties of hydrophobic, anti-corrosion, heat insulation, infrared stealth and electromagnetic wave absorption

In addition to having a superior electromagnetic wave (EMW) absorption profile, materials of this type that are applied in complex and extreme environments must be hydrophobic, anti-corrosive, heat insulating and infrared stealth. In the described investigation, a multifunctional UIO-la-CoN-rGO aerogel that possesses all of these properties was fabricated by using a hydrothermal and freeze drying process. Lauric acid (la) is incorporated into this aerogel to enlarge pore sizes and enhance hydrophobicity of the Zr-based metal organic framework (UIO-66) component. The large interfacial and dipole polarization caused by anchoring UIO-66 nanospheres to the Co,N co-doped graphene nanosheets results in a high EMW absorbing performance, reflected in a minimum reflection loss (RLmin) of −44.8 dB and a wide effective absorbing bandwidth (EAB) of 7.28 GHz. In addition, the aerogel displays high levels of hydrophobicity, anti-corrosiveness, heat insulation and infrared stealth. For example, UIO-la-CoN-rGO has a water contact angle of 142.5°and a surface temperature that remains nearly unchanged after more than 1 h at 100 ℃. Moreover, the UIO-la-CoN-rGO coating gives the aerogelanimpedance valueof1.5 × 105 Ω·cm2 after being soaked in 3.5 % aqueous NaCl for 30 d, and an anti-corrosion efficiency of 99.149 %. The results of this study provide guidance for the design of multifunctional EMW absorbing materials that function in complex environments.

Enhanced stretchability of porous PDMS/CIP composites via weak interfacial bonding and their electromagnetic noise suppression properties

The development of wearable devices operated through massive data communication necessitates the use of lightweight, highly efficient stretchable composites to suppress electromagnetic (EM) noise. In this study, highly stretchable porous polydimethylsiloxane (PDMS)/carbonyl iron powder (CIP) composite-based EM noise suppressors were explored. The porous structure reduced the volume fraction of PDMS in the composites, leading to a reduction in the total weight of the composites. The introduction of CIP to porous PDMS initially degraded stretchability owing to stress concentration at the strongly bonded interfaces between the CIP surface and PDMS. However, reducing the interfacial bonding strength by removing the SiO2 layer on the CIP surface significantly enhanced stretchability, causing the resulting composite to display 1.2–1.6 times higher rupture strain values at the same CIP loading contents than those with high interfacial bonding strength. The EM absorption properties of the porous and nonporous PDMS/CIP composites were characterized, and the porous PDMS/CIP composites exhibited ∼1.5 times higher EM noise suppression performance than the nonporous composites. This improvement is attributed to the vacant space within the porous framework filled with air, which enhances impedance matching and extends the transmission route of EM waves.

Polypyrrole/Fe3O4 nanocomposites anchored on graphene toward efficient electromagnetic wave absorption performance

The ternary nanocomposites of polypyrrole/Fe3O4/graphene (PPy/Fe3O4/RGO) have been prepared via a two-step method. PPy/Fe3O4 composites have been initially anchored on GO surface by chemical one-step method following by reducing GO. The electromagnetic wave absorption (EMWA) performance of composites can be tuned by adjusting the amount of pyrrole monomers. The maximum reflection loss of the PPy/Fe3O4/RGO-0.5 (pyrrole:0.5 mL) composite is up to −66.0 dB at 14.88 GHz and the absorption bandwidths exceeding −10 dB were 5.76 GHz with absorber thickness of 2.5 mm. The investigation of the electromagnetic absorb-ability reveals that PPy/Fe3O4/RGO exhibits enhanced electromagnetic absorption properties compared to Fe3O4/RGO, which is mainly ascribed to the improved impedance matching, the enhanced interfacial effects and geometric effect. Furthermore, this strategy expands the scope of the electromagnetic wave absorption materials. It confirms that modification of graphene with PPy and Fe3O4 makes the ternary nanocomposites have a promising future in electromagnetic wave absorption materials.

Superior microwave absorption properties of anisotropic Y2Fe16‒xCoxSi/paraffin composites by orientation tuning

Y2Fe16-xCoxSi/paraffin composites were prepared by three different orientation methods. The effect of these orientation methods and the magnetocrystalline anisotropy of Y2Fe16‒xCoxSi alloys on the electromagnetic parameters and the microwave absorption properties were investigated. The results demonstrated that orientation tuning improved the electromagnetic parameters and microwave absorption properties. Anisotropy in dielectric properties and magnetic properties of Y2Fe16-xCoxSi/paraffin composites were achieved by tuning the orientation of Y2Fe16-xCoxSi powders. The planar and conical anisotropic materials had superior microwave absorption properties than uniaxial anisotropic materials for the same orientation method. The Y2Fe16‒xCoxSi/paraffin composite had an effective absorption bandwidth of 8.4 GHz (9.6–18 GHz) and a reflection loss of ‒59.6 dB which can almost cover the X–Ku bands and exceed the performance of many reported absorbing materials, showing its great prospects for microwave absorption in the X–Ku bands.

Mechanical and radar absorption properties of sheep wool/epoxy composites

PurposeThe aim of this study is to determine the fracture behavior of wool felt and fabric based epoxy composites and their responses to electromagnetic waves.Design/methodology/approachNotched and unnotched tensile tests of composites made of wool only and hybridized with a glass fiber layer were carried out, and fracture behavior and toughness at macro scale were determined. They were exposed to electromagnetic waves between 8 and 18 GHz frequencies using two horn antennas.FindingsThe keratin and lignin layer on the surface of the wool felt caused lower values to be obtained compared to the mechanical values given by pure epoxy. However, the use of wool felt in the symmetry layer of the laminated composite material provided higher mechanical values than the composite with glass fiber in the symmetry layer due to the mechanical interlocking it created. The use of wool in fabric form resulted in an increase in the modulus of elasticity, but no change in fracture toughness was observed. As a result of the electromagnetic analysis, it was also seen in the electromagnetic analysis that the transmittance of the materials was high, and the reflectance was low throughout the applied frequency range. Hence, it was concluded that all of the manufactured materials could be used as radome material over a wide band.Practical implicationsSheep wool is an easy-to-supply and low-cost material. In this paper, it is presented that sheep wool can be evaluated as a biocomposite material and used for radome applications.Originality/valueThe combined evaluation of felt and fabric forms of a natural and inexpensive reinforcing element such as sheep wool and the combined evaluation of fracture mechanics and electromagnetic absorption properties will contribute to the evaluation of biocomposites in aviation.