Electromagnetic Absorption Properties Research Articles

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

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.

Coupling RGO with magnetic components derived from basic ferric cobalt carbonate (BFCC) for efficient microwave absorption

In this work, reduced graphene oxide (RGO)-based composites loaded with magnetic CoFe2O4 (CFO) and CoFe were successfully synthesized via heat treatment of basic ferric cobalt carbonate (BFCC) under different temperatures. The impact of adding CFO and CoFe on the electromagnetic parameters and absorption properties was investigated. When 40 wt% CFO flakes and CoFe particles are added to the RGO matrix and the filler content is 20 wt% in paraffin, there gives a reflection loss of −48 dB with a 5.5 GHz absorption bandwidth at 2.1 mm thickness, and −50 dB with 4.8 GHz at 2.9 mm, respectively. The coupling of a magnetic medium can change the electromagnetic loss mechanism in the material, which ultimately affects the absorption properties of the material. This study provides a good basis for the design of composite materials of RGO as microwave absorbing materials, enabling large-scale production of high-performance absorption materials.

Lightweight, ultra-broadband SiOC-based triply periodic minimal surface meta-structures for electromagnetic absorption

Lightweight, wide-band ceramic-based electromagnetic (EM) absorbers have great application demand in the field of high-temperature EM wave absorption. However, it is difficult for traditional ceramic-based structural EM absorbing materials (EMAMs) to balance the contradiction between broadband absorption and good impedance matching due to resonance effect. Herein, three novel non-resonant SiOC-based triply periodic minimal surface (TPMS) meta-structures named Schoen G (SG), Schwarz D (SD) and Schwarz P (SP) with a density of 0.556 g/cm3 were successfully synthesized by digital light processing (DLP) 3D printing and polymer-derived ceramics (PDCs) method. Through the structural design of multilayer arrays and holes, three metamaterials achieve good impedance matching and broadband EM absorption. The effective absorption bandwidth (EAB) of all three meta-structures reaches 9.80 GHz (8.2–18.0 GHz) in a wide matching thickness range, covering the entire X-Ku band. In addition, the minimum reflection loss (RLmin) of −55.68 dB is obtained at a matching thickness of 3.02 mm for SD meta-structure in X-band. Besides, the SG meta-structure tested by the arch method has an ultra-wide EAB of 11.88 GHz (6.12–18.0 GHz), exhibiting ultra-broadband EM absorption properties. It is significant that the intrinsic relationships between TPMS meta-structures and EM responses are explored by CST simulation. This work provides a new perspective for the design of lightweight, broadband ceramic-based EM metamaterial absorbers under high-temperature, harsh environments.

Effect of Ce doping on electromagnetic characteristics and absorbing properties of M-type barium ferrite

In this study, Ce3+-doped M-type barium ferrite BaCexFe12-xO19 (x = 0 ∼ 1.2) was prepared by sol-gel method. The effects of Ce3+ doping on the crystal structure, microstructure, electromagnetic properties and absorption properties of M-type barium ferrites were investigated. The results indicate that the crystal structure remains unchanged with the increase of Ce3+ doping. The crystal size of Ce3+ doped barium ferrite is in the micro-meter range, and the grain size remains almost constant with increasing doping. The addition of Ce3+ to the BaFe12O19 samples resulted in significant improvements in their electromagnetic and microwave absorption properties. These improvements were mainly due to the synergistic effect of magnetic and dielectric losses. Among the samples doped with different concentrations of Ce3+, BaCe0.2Fe11.8O19 exhibited the best absorption performance, which has a minimum reflection loss of −58 dB and an effective absorption bandwidth of 9.44 GHz at a matched thickness of 2.3 mm. This study proposes an efficient electromagnetic wave absorber with a wider effective absorption bandwidth.

Performance of Electromagnetic Properties of Carbon Fiber Reinforced and AuNPs Functionalized MWCNTs Doped Hybride Composites

The purpose of this article is to compare the electromagnetic absorption properties of carbon fiber layer composite materials produced separately using Au particles doped MWCNT added epoxy with pure MWCNT added epoxy resin. This new material, produced using MWCNT doped with Au particles, increases its radar absorption capability. And therefore the as-prepared electromagnetic absorber demonstrates enormous potential in future military and aviation applications. Multilayer composite materials, consisting of Au/MWCNT doped epoxy, MWCNT doped epoxy and pure epoxy, were produced by vacuum infusion method. Electromagnetic absorbing properties of the produced materials were determined with the Agilent brand 2-Port PNA-L Network Analyzer device by conducting transmission/reflection measurements in the frequency range of 3–18 GHz. The electromagnetic absorbing properties of the produced composite materials were taken in two different measurements, both with and without metal plate. Measurements were made using two horn antennas. Show that the produced MWCNT doped and Au/MWCNT doped carbon fiber laminated composite material has good absorption behavior when used with metallic sheets and is good for RADOM applications at many points at 3–18 GHz.

Tailoring permittivity and permeability of M-type hexagonal ferrite and 2D Ti3C2Tx MXene composites for broadband microwave stealth performance

In this study, owing to the significant advantages of heterogeneous interface engineering for customizing the electromagnetic parameters and microwave absorption properties, high magnetic lossy cobalt/zinc-doped hexagonal ferrite flakes were successfully anchored on two dimensional Ti3C2Tx with varying mass ratios. Inorganic Ti3C2Tx MXene was synthesized through the hydrofluoric acid etching process, and doped hexagonal ferrite was prepared by a solid-state sintering route leading to electrostatic bonding with Ti3C2Tx particles. Scanning electron microscopy revealed that the MXene surface strongly adhered to the ferrite particles. By adjusting the ratio of ferrite to Ti3C2Tx, it is feasible to optimize electromagnetic parameters, as required. Specifically, doped ferrite@4% Ti3C2Tx MXene composite exhibited remarkable absorption performance; the maximum reflection loss (RL) was −49 dB at 15.2 GHz with a thickness of 1.9 mm. The effective bandwidth corresponding to the RL values below −10 dB is 8.3 GHz (from 9.7 GHz to 18 GHz) at a single thickness of 2 mm, and below −15 dB is 6.4 GHz (from 10.7 GHz to 17 GHz), outlining the prospect for application as an electromagnetic wave absorber. Radar cross-section (RCS) simulation was performed with microwave incident angles ranging from 0 to 360°. The results demonstrate a reduction in RCS of up to −47.8 dBsm at a 60° incident angle. This study develops a new approach for constructing multi-component heterostructure composites with tailored electromagnetic parameters as a superior and modulated radar stealth material.

Electromagnetic Characteristics and Microwave Absorbing Properties of a Novel Stainless Steel Powder

In order to solve the problem of insufficient oxidation resistance and corrosion resistance of magnetic metal absorbent represented by carbonyl iron powder, a wave absorbing composite material which consists of different filling mass proportions of the atomized electrolytic stainless steel powder and paraffin wax is investigated. The electromagnetic (EM) characteristics and absorbing performance of the proposed composite material were tested with Agilent N5234A vector network analyzer in a frequency range of 2–18GHz. The experimental results show that the real and imaginary parts of the dielectric permittivity of stainless steel powder/paraffin composites will increase with the filling mass fraction in the test frequency band, while the real part of the permeability [Formula: see text] decreases with the increase of the mass fraction, and the imaginary part [Formula: see text] increases with the increase of the mass fraction. At a thickness of 3 mm, with the filling mass fraction increasing from 20 wt.% to 60 wt.%, the peak frequency of reflection loss (RL) moves to low frequency from 17.92 GHz to 16 GHz. Meanwhile, the minimum reflection loss (RL[Formula: see text]) also shows a downward trend, and the RL[Formula: see text] value with a filling mass fraction of 60 wt.% is −8.93[Formula: see text]dB. It can be seen that stainless steel powder shows good microwave absorbing performance, and it has excellent anti-oxidation, and anti-corrosion properties. Based on the excellent performance of stainless steel powder, its absorption performance is expected to be further improved through multi-layer optimization design, so as to meet the needs of electromagnetic protection in harsh environments.

Flexible and stretchable polyester@reduced graphene oxide composite fabric for tunable electromagnetic absorption

The widespread application of 5 G wireless communication and flexible electronic devices has put forward new demands for electromagnetic (EM) absorbing materials. In this work, a flexible composite fabric was successfully prepared by using polyester (PET) knitted fabric as an elastic scaffold and subsequently anchoring reduced graphene oxide (rGO) through a simple impregnation-drying coating method. Regulating the concentration of graphene oxide (GO) impregnation solution can effectively control the rGO loading content for adjusting the EM parameters of PET@rGO composite fabric. When the concentration is 2.0 mg/mL, the as-prepared PET@rGO exhibits the optimum reflection loss (RL) value of −24.53 dB at 12.4 GHz and a corresponding effective absorption bandwidth (EAB, RL≤−10 dB) of 3.20 GHz (9.20–12.40 GHz). The impressive absorption property attributed to the synergistic effect of impedance matching and dielectric loss originated from the three-dimensional (3D) conductive network on fabric interlaced structures. More importantly, stretching PET@rGO composite fabrics to different deformations can dynamically adjust the EM absorption properties while maintaining the knitted structure. This work demonstrates an efficient avenue for the rational design of next-generation EM absorbing fabric, showing latent applications in flexible functional electronics.

Synthesis of nano/micro ternary magnetic particles with different Co content and their electromagnetic absorbing properties

To comprehend the influence of Co element content on the microwave absorption properties of FeCoNi alloy particles, five sets of nano/micro FeCoNi alloy particles with varying Co element contents were fabricated with chemical liquid deposition. The microstructure, static magnetic characteristics, and microwave absorption performance were studied. The results shown that the synthesized FeCoNi alloy particles exhibited spherical morphology and face-centered cubic crystal structure, with the average particle size increasing from 150 nanometers to 500 nanometers as the Co element content rose. All five sets of samples presented soft magnetic properties, with the saturation magnetization fluctuating between 97.1–129.5 emu/g and coercivity ranging from 40.4–280.3 Oe. As the frequency of electromagnetic waves increased, the real part of the complex permittivity of the alloy particles demonstrated minimal variation, while the imaginary part exhibited dielectric loss absorption peaks in the frequency ranges of 10–16 GHz, 10–14 GHz, and 8–10 GHz/13–16 GHz. The imaginary part of the complex permeability initially increased and then decreased with the frequency rose. All the samples exhibited distinct Debye semicircles and polarization relaxation losses within the samples. The sample with Co content of x = 0.8 Fe1Co0.8Ni1 achieved the maximum effective absorption bandwidth 5.36 GHz at thickness of 1.5 mm and the maximum reflection loss |RLmax| 32.5 dB at thickness of 2.2 mm for relatively good impedance matching and excellent combination of magnetic loss and dielectric loss.

Electromagnetic and microwave absorption properties of flexible fabric coatings containing Ag decorated spherical graphene powders with FSS incorporation

Flexible textile microwave absorbing materials own the advantages of flexibility, foldability and cuttability, have become a research hotspot in electromagnetic stealth technology. In this study, a microwave absorbing coating was prepared on a fabric substrate using Ag decorated spherical graphene (SG) as the absorbent. XRD results demonstrated the metallic Ag ion was successfully reduced. TEM photographs showed the silver nanoparticles were stuck to the spherical graphene. The complex permittivity was enhanced after compositing with Ag particles. Along with the increase of silver content from 0 to 20 wt%, the complex permittivity rises from 3.29–0.42j to 6.93–2.22j owing to its higher electric conductivity and stronger relaxation effect. Meanwhile, the flexible coating containing Ag decorated spherical graphene (Ag@SG) also exhibited better microwave absorption performance. The minimum reflection loss (RLmin) for the coating with a thickness of 3.0 mm was −15 dB. And the effectively absorbing broadband (EAB) is located at 9.08–11.52 GHz. In addition, the microwave absorbing performance was greatly enhanced after being combined with periodic frequency selective surface (FSS). The EAB was obtained over the entire X-band frequency range, and the RLmin value achieved −41.72 dB at 10.25 GHz. What's more, the coating owned an EAB in a wide range incident angle of 60°–90°. This work was help to developing high performance flexible fabric coating containing Ag decorated spherical graphene with FSS incorporation.

Tuning dielectric and electromagnetic absorption properties of SiC fiber by in-situ grown polycrystalline carbon nanowires

Silicon carbide fiber (SiCf) has a promising potential to develop structural electromagnetic wave (EMW) absorption materials. Tuning dielectric properties of SiCf is necessary to obtain excellent EMW absorption performances, which is always realized by the introduction of extra dielectric loss phases. Herein, in-situ grown polycrystalline carbon nanowires (CNW) as novel dielectric fillers, possessing moderate conductivity as well as efficient loss ability, were used to improve the EMW absorption performance of SiCf. When the content of CNW is suited, CNW can interconnect with each other and form a multiporous network on the surface of SiCf. Such a unique network makes a great contribution to good impedance matching as well as strong conductivity loss and polarization loss, which endows SiCf with an effective absorption broadband (EAB) of 4.14 GHz at a thickness of 3.0 mm, demonstrating superior EMW absorption performance than most previously reported SiCf/carbon hybrids.

Excellent microwave absorption of Y2Fe15.5Co0.5Si/paraffin composites by tuning powder particle size

The electromagnetic and microwave absorption properties of Y2Fe15.5Co0.5Si and its paraffin composites have been investigated. It is found that the ball milling time is directly related to the particle size of the powder, which influences the microwave absorption performance and the degree of orientation of the composites. When the particle size of the Y2Fe15.5Co0.5Si powder approaches the grain size, the difference between the in-plane and the out-of-plane anisotropy field of the oriented composite increases. The reflection loss (RL) peak of the oriented composites moves to the low frequency band due to higher complex permeability and complex permittivity values at 0.5–8 GHz. A minimum RL of –52.80 dB, for a thickness of 2.28 mm, at 6.28 GHz is obtained for the Y2Fe15.5Co0.5Si/paraffin composite. The effective absorption bandwidth (EAB: RL ≤ –10 dB) is 5.43 GHz (12.31–17.74 GHz) at 1.12 mm, exceeding many reported microwave absorbing materials. Thus Y2Fe15.5Co0.5Si composites exhibit huge potential for microwave absorption in the Ku band.

Organosilane waste-derived SiCnws/SiOC composites with enhanced electromagnetic wave absorption performance

SiCnws/SiOC nanowires composites with a 3D network structure, exhibiting enhanced electromagnetic microwave absorption properties, were synthesized using carbothermal reduction. The solid precursor, organosilane waste, was employed, enabling cost-effective and environmentally friendly production. The structure and morphology of SiCnws/SiOC nanowires composites were extensively investigated by XRD, SEM, TEM, XPS spectra, and Raman spectra. Moreover, the composite demonstrated superior electromagnetic wave absorbing properties, including wide effective absorption bandwidth (EAB) of 2.73 GHz, strong minimum reflection loss (RLmin) of −52.66 dB, and thin thickness of 2.40 mm. These excellent electromagnetic wave attenuation properties stem from the synergistic strategy of dielectric and conductive losses, resulting from the unique 3D network heterostructural architecture. This work not only offers improved EMW absorption solutions but also contributes to waste recycling and resource recovery.