Wide-band Electromagnetic Wave Absorbers Research Articles

Facile construction of wide-band electromagnetic wave absorber based on honeycomb-like PU foam embedded with GO-rGO/SmCo5 nanocomposite for stealth application of drone

The utilization of three-dimensional hierarchical porous foam structures has proven to be a successful approach in creating lightweight and wide bandwidth microwave absorbers with superior performance. In this study, a honeycomb-shaped polyurethane (PU) foam was utilized as the substrate for an absorber. It was combined with a new nanocomposite consisting of GO-rGO as the dielectric parts and SmCo5 as the magnetic component. The concept of utilizing a GO-rGO nanocomposite with varying bandgap within the synthesized composite foam led to the creation of multiple heterogeneous interfaces, enhancing interfacial polarization and ultimately achieving optimal impedance matching. Furthermore, the incorporation of GO-rGO nanocomposites in the synthesis of SmCo5 aimed to facilitate the thorough amalgamation of the components, mitigate the self-agglomeration of the magnetic particles, and establish a two-dimensional matrix of aligned magnetic particles, resulting in an improvement in magnetic loss phenomena. Additionally, the 3D hierarchical structure of the porous foam serves to create an intricate network, thereby enhancing the transmission pathways and enabling the activation of a greater number of attenuation phenomena. The findings suggest that the compound presents remarkable abilities in absorbing microwaves, boasting a reflection loss of −32.5 dB at 10.6 GHz and an effective absorption bandwidth of 4 GHz at a 1.4 mm thickness. The outstanding microwave absorption properties can be credited to the activation of a variety of attenuation mechanisms, including interfacial polarization, multiple reflections and scattering of waves, enhanced impedance matching, and resilient magneto dielectric losses.

Light-weight wideband electromagnetic wave absorber based on aramid paper

A lightweight wideband honeycomb absorber is theoretically and experimentally investigated. The proposed absorber is constructed of aramid paper, which contains carbon fibers to absorb partially the incident electromagnetic wave. Graded silver paste circuits are also printed on aramid paper to improve the impedance matching properties and, thus, achieve wideband absorption performance. An absorber sample was fabricated and measured to verify the design strategies. The designed absorber has a fractional absorption bandwidth of 133% from 3.6–18 GHz, with a thickness of 0.19λL at the lowest frequency. The total weight of the absorber is 18.2 g, with a density of 28.4 kg/m3.

Multi-interface-induced by regulating nanocomposite morphology and absorber design to achieve wideband electromagnetic wave absorber

The current study describes the fabrication of a bilayer microwave absorber made of magnetic Sr2FeReO6 (SRO) powder and a magnetoelectric nanocomposite formed of rod-like magnetic Sr2FeReO6 powder wrapped in polygonal SnS2 powder (SRSS), which was then annealed and analyzed. The analysis of phase constituents, as well as morphological and magnetic measurements, revealed that rod and polygonal particles with soft magnetic properties were successfully synthesized. Additionally, our findings showed that 30:70 wt ratio nanocomposite powders were unable to exhibit broad X-band frequency absorption capabilities. Due to the bi-layer absorber's rational design, the reflection loss was found to be increased and reached -33 dB at 10.3 GHz by covering practically the whole X-band frequency with only 2.5 mm of thickness. The prepared absorber's optimum design included SRSS nanocomposite powder as an absorbing layer with a 1.5 mm thickness and SnS2 powder as a matching layer. The exceptional electromagnetic wave dissipation performance of bi-layer samples compared to single-layer absorber samples may be the result of multiple interfaces being formed as a result of controlling component morphology and composition as well as the absorber's design, which enhanced critical absorbing factors like various polarization phenomena and relaxation losses. The research presented here suggests a simple method for enhancing microwave dissipation performance with a broad absorption band based on the development of heterojunction structures and the integration of various loss processes.

Rational construction of wideband electromagnetic wave absorber using hybrid FeWO4-based nanocomposite structures and tested by the free-space method

In this research, we developed a wideband electromagnetic wave absorber suitable for the X-band frequency by using a unique hybrid nanocomposite structure made of FeWO4 embellished with Ag3PO4 nanopowders. Simple chemical hydrothermal and microwave-aided hydrothermal procedures were used to successfully produce single-phase spherical-like FeWO4 and FeWO4@Ag3PO4 nanocomposite powders. Using XRD, FTIR, VSM, FESEM, and VNA methods, the phase constituents, morphological, magnetic, and electromagnetic properties of the produced nanocomposite materials were assessed. The resin-based nanocomposite absorber sample allows to obtain a maximum reflection loss of −21 dB with a matching thickness of 1.8 mm at the ferromagnetic resonance of 10.4 GHz with a 3.8 GHz effective absorption bandwidth, which is evaluated using the waveguide technique, when the filler loading percentage reaches 40 wt percent (S40). S40 had superior impedance matching capabilities, a wide effective absorption bandwidth, and a high absorption capacity when compared to other produced absorber samples. The best sample is prepared for free-space testing with the dimension of 200 × 200 mm and an optimum thickness of 1.8 mm, and the results demonstrate a good agreement between the waveguide and free-space technique results. This absorber sample's wideband absorption capacity was attained by adjusting the magneto-electric composition and enhancing the interfacial characteristics brought on by the core-shell construction. In this study, a design approach for efficient microwave absorbers based on a magneto-electric hybrid nanocomposite structure is presented, using waveguide and free-space experimental methods in two different ways.

Influence of Spatial Correlation Function on Characteristics of Wideband Electromagnetic Wave Absorbers with Chaotic Surface

Electromagnetic metasurface with chaos patterned surface could bring rich interaction modes contributing to fully disordered random motions in deterministic systems, which preform uncertainty, irreducibility and unpredictability. We investigate the influence of the correlation function (CF) properties of surface random patterns on the wave absorption performance. The complicated correlation function provides a fully developed random state, broadening the absorption bandwidth significantly and is helpful for reaching higher absorption rate. With the increasing number of peaks in the correlation function, the absorption band at –15 dB reflectivity widens significantly, band at –20 dB reflectivity begins to emerge. As the first peak’s distance from the original point in the CF is enlarged, the absorption trough is gradually formed and deepened to –35 dB level. The results give in-depth understanding of the relation between absorption behavior and controlling parameters including correlation, image information and foam spacer layer thickness. This high absorption absorber has great application potential in customizable radio communication compatibility device and anechoic testing chamber.

Biomass-Derived Carbon Heterostructures Enable Environmentally Adaptive Wideband Electromagnetic Wave Absorbers

HighlightsA novel, non-porous carbon structure was obtained through pyrolysis of biomass heterostructures consisting of cellulose and lignin.The novel class of biomass-derived carbon materials exhibit an enhanced electromagnetic (EM) loss capability due to the nano-antenna structure created by in-situ growth of carbon nanofibers on carbon nanosheets.The designed carbon materials exhibit good hydrophobicity and acid/base resistance, suggesting a stable EM absorption performance in diverse environmental conditions, thus making it a good candidate for real world conditions.

MOF-derived NiFe2S4/Porous carbon composites as electromagnetic wave absorber

The preparation of strong absorption, thin thickness and wide band electromagnetic wave absorbers has always been the focus of research. In this paper, NiFe2S4/PC composites, an electromagnetic wave absorbing material with excellent performance, is prepared by introducing Ni-MOF, Fe and S elements into porous carbon framework. The material has a minimum reflection loss (RLmin) of −51.41 dB and the matching thickness is only 1.8 mm. In addition, the effective absorption bandwidth (EAB) is 4.08 GHz when the thickness is 1.9 mm. The rich interface and good impedance matching characteristics are the main reasons for the excellent absorbing performance of the material. The experimental results show that NiFe2S4/PC composites is a reasonable and effective electromagnetic wave absorption material.

Electromagnetic wave absorbing properties of SrFe12-2xCoxTixO19 hexaferrite–CNT–epoxy composites

A wideband electromagnetic (EM) wave absorber for the X-band (8–12 GHz) is designed using M-type hexaferrite, SrFe12-2xCoxTixO19 (x = 1.1, 1.2, 1.25, and 1.3)–CNT (0–3 wt%)–epoxy (10 wt%) composites. As x increases from 1.1 to 1.3, the ferromagnetic resonance (FMR) of the hexaferrite powder gradually decreases from 15.0 GHz to 6.4 GHz due to the decrease of magnetocrytalline anisotropy. The EM absorption frequency range changes in accordance with changes in the FMR frequency. Among the series of samples, the x = 1.25 sample demonstrates EM absorption properties optimized for the X-band with the lowest reflection loss (RL) of −40 dB and satisfying RL <−10 dB in the 7–13 GHz range. When 1 wt% carbon nanotubes (CNTs) are added to the composite (x = 1.25), permittivities ε′ and ε″ increased significantly owing to the CNT particle’s high conductivity, and the intensive EM absorbing region expanded to a wide frequency–thickness range. A further increase in the CNT content (2–3 wt%) weakened the overall EM absorption due to an increase in reflection. Adding 1–2 wt% of CNT to hexaferrite is very effective because it not only increases the shielding effectiveness, but also yields better EM absorption at lower thicknesses of 1.5 mm or less.

Design of multiple-layer microwave absorbing structure based on rice husk and carbon nanotubes

This paper presents a multiple-layered microwave absorber using rice husk and carbon nanotube composite. The dielectric properties of each layer composite were measured and analysed. The different layer of microwave absorber enables to control the microwave absorption performance. The microwave absorption performances are demonstrated through measurements of reflectivity over the frequency range 2–18 GHz. An improvement of microwave absorption <−20 dB is observed with respect to a high lossy composite placed at bottom layer of multiple layers. Reflectivity evaluations indicate that the composites display a great potential application as wideband electromagnetic wave absorbers.

Metamaterial-based wideband electromagnetic wave absorber.

In this paper, an analytical and numerical study of a new type of electromagnetic absorber, operating in the infrared and optical regime, is proposed. Absorption is obtained by exploiting Epsilon-Near-Zero materials. The structure electromagnetic properties are analytically described by using a new closed-form formula. In this way, it is possible to correlate the electromagnetic absorption properties of the structure with its geometrical characteristics. Good agreement between analytical and numerical results was achieved. Moreover, an absorption in a wide angle range (0°-80°), for different resonant frequencies (multi-band) with a large frequency bandwidth (wideband) for small structure thicknesses (d = λp/4) is obtained.

Investigation of microwave absorption properties of multiwalled nanotube buckypaper filled with cobalt nanoparticles

The paper demonstrates the filling of cobalt nanoparticles into the multiwalled carbon nanotube buckypaper by the dispersion and filtration method to study microwave absorption. Synthesised buckypaper samples were subject to characterisation by using X-ray diffraction, scanning electron microscope, atomic force microscope and four probe techniques to measure the size of the cobalt particles, morphology and low temperature electrical resistivity of the buckypaper, respectively. We used two different sizes of cobalt particles (14·54 and 33·04 nm, respectively) for doping in the buckypaper. Microwave-absorbing properties were examined by measuring the transmission coefficient (S21) in a frequency range of 1–20 GHz with the buckypaper as an absorber. Variations in the resistivity value, with different particle sizes of cobalt were attained by the low temperature resistivity measurements. The observed maximum of S21 indicates that the cobalt–buckypaper displays good microwave absorption (90%) properties for a potential application as wideband electromagnetic wave absorbers.

Structural, Magnetic, and Reflection Loss Characteristics of Ni/Co/Sn-Substituted Strontium Ferrite/Functionalized MWCNT Nanocomposites

Ni/Co/Sn-substituted strontium ferrite [SrFe12−x(Ni0.5Co0.5Sn)x/2O19]/multiwalled carbon nanotube (MWCNT) nanocomposites were produced by assembling ferrite particles on the external surfaces of MWCNTs. Various techniques including x-ray diffraction (XRD) analysis, transmission electron microscopy, field-emission scanning electron microscopy (FE-SEM), and Fourier-transform infrared (FTIR) spectroscopy were used to demonstrate the successful attachment of ferrite particles onto the external surfaces of the MWCNTs. XRD analysis and FTIR spectroscopy confirmed the presence of strontium ferrite and carbon nanotube phases in ferrite and nanocomposite samples, respectively. FE-SEM micrographs indicated the formation of ferrite particles on the outer surfaces of MWCNTs in nanocomposite samples. Furthermore, vibrating-sample magnetometer (VSM) and reflection loss (RL) measurements were performed to assess the magnetic and microwave characteristics of the synthesized samples. VSM loops confirmed a relatively strong dependence of the saturation magnetization and coercivity on the volume percentage of MWCNTs. With the introduction of MWCNTs or an increase in the substitution, the saturation magnetization and coercivity were decreased. The RL properties of the nanocomposites were investigated in the 8 GHz to 12 GHz frequency range. The sample with 80 wt.% nanocomposite content showed a maximum RL of −35 dB at 8.3 GHz with a 4 GHz absorption bandwidth over the extended frequency range of 8 GHz to 12 GHz for absorber thickness of 1.8 mm. The RL evaluations indicated that these nanocomposites have high potential for application as wide-band electromagnetic wave absorbers at GHz frequencies.

Electromagnetic wave absorption characteristics of multiwalled carbon nanocoils

We have studied the electromagnetic wave absorption properties of a multiwalled carbon nanocoil (MWCNC), a promising lightweight and wide-band electromagnetic wave absorber. Experiments were conducted using several types of paste with various weight concentrations of MWCNC compounded into an organic binder. The results revealed the significant electromagnetic wave absorption potential of the MWCNC. They also verified that its electromagnetic wave absorption effect is strongly dependent on MWCNC concentration, so that there is an optimal MWCNC composition. The increased sample thickness enhances electric conduction loss and encourages electromagnetic wave absorption, even in a high-frequency range. Consequently, the MWCNC has been demonstrated as a new outstanding electromagnetic wave absorber.

Evaluation of microwave and magnetic properties of substituted SrFe12O19 and substituted SrFe12O19/multi-walled carbon nanotubes nanocomposites

SrFe12−xCrx/2Alx/2O19 (x = 0–2.5) nanoparticles and ferrite/multi-walled carbon nanotubes (MWCNTs) nanocomposites were synthesized by a sol–gel method. The XRD patterns show a relatively weak peak around 26° which is corresponding to the graphite (002) lattice plane of the MWCNTs. The peak of Fourier transform infrared spectroscopy (FTIR) at 1729 cm−1 can be assigned to CO bond of carboxylic groups, indicating the presence of poly(acrylic acid) (PAA) chains in PAA–carbon nanotubes. Field emission scanning electron microscopy (FE-SEM) micrographs demonstrate that strontium ferrite nanoparticles are strung along the MWCNTs. Transmission electron microscopy (TEM) was employed to study the structure of MWCNTs. Vibrating sample magnetometer (VSM) measurements show that with an increase in x content, the values of saturation of magnetization of SrFe12−xCrx/2Alx/2O19 nanoparticles reduce, while coercivity increases. Results of reflection loss indicate that with adding Cr–Al cations and MWCNTs to strontium ferrite; it is possible to cover a wideband of electromagnetic waves in the frequency range of 50–74 and 12–18 GHz. In addition, it can be seen that the strontium ferrite nanoparticles and nanocomposites display a great potential application as wideband electromagnetic wave absorbers.

자성재료를 이용한 광대역 전자파 흡수체 설계 연구

The absorption performance of a metal-backed single layered electromagnetic wave absorber is optimized at matching conditions of thickness and frequency indicating the maximum returns loss of incidence electromagnetic wave in the contour map. These matching conditions are obtained by applying the electromagnetic impedance to the transmission line theory, which depend on the complex permeability and complex permittivity of absorber material. The magnetic materials with high permeability can enhance the matching thickness condition to the wide frequency range based on the decrease of permeability with frequency and it can be used as a wideband electromagnetic wave absorber material. Therefore, the magnetic materials with higher saturation magnetization and lower permittivity than NiZn ferrite can be applied to the wideband electromagnetic wave absorber in order to satisfy the newly enforcing the electromagnetic compatibility regulation in the future.

Magnetic and Reflection Loss Characteristics of Terbium Substituted Cobalt Ferrite Nanoparticles/Functionalized Multi-Walled Carbon Nanotube

Terbium substituted cobalt ferrite dot array was formed onto surface of multi-walled carbon nanotube by hetero-coagulation. X-ray diffraction (XRD), and scanning electron microscope (SEM) were used to demonstrate the successful attachment of ferrite nanoparticles to M WCNTs. Mossbauer spectroscopy results confirm the preference of terbium for tetrahedral sites. Vibrating sample magnetometer (VSM) confirms the relatively strong dependence of saturation of magnetization and coercivity with the volume percentage of MWCNTs. The complex permittivity, permeability, and reflection loss properties of the ferrite and nanocomposites were studied separately. Reflection loss of nanocomposites is abruptly enhanced in compare to that of ferrite and carbon nanotubes. Reflection loss evaluations indicated that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.

A comparison between magnetic and reflection loss characteristics of substituted strontium ferrite and nanocomposites of ferrite/carbon nanotubes

Large-scale carbon nanotubes (CNTs)/substituted strontium ferrite nanocomposites have been fabricated by hetero-coagulation. The structure and morphology of nanoparticles and nanocomposites were evaluated by high-resolution transmission electron microscopy (HRTEM). HRTEM confirmed that strontium ferrite was successfully attached to carbon nanotubes. The vibrating sample magnetometer (VSM) confirmed the relatively strong dependence of saturation magnetization with the volume percentage of multi-walled carbon nanotubes (MWCNTs). Reflection loss of nanocomposites at 12–18 GHz was evidently enhanced, as compared to that of strontium ferrite nanoparticles. The maximum reflection loss increased significantly with an increase in volume percentage of MWCNTs. It was proved that the microwave absorbing bandwidth was modulated simply by manipulating the thickness of nanocomposites. Reflection loss evaluations indicate that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.

EXPERIMENTAL STUDY OF WIDE BAND ELECTROMAGNETIC WAVE ABSORBER PANEL AS BUILDING OUTER WALL FOR PRACTICAL USE

Two types of wide-band electromagnetic wave absorber panel were developed for multipath interference reduction in urban communication systems. The characteristics were measured using mock-ups of the absorber panel with the time domain method. In this paper, an application of the developed absorber panel to digital television broadcasting and the influence of the difference between an actual absorber panel and mock-up on its performance are discussed. It is estimated that the area of communication disturbance is eliminated by applying the developed absorber panel. By experiments, it became clear that the several factors reduce the frequency range in which the reflection is suppressed below -14dB.

Enhanced reflection loss and permittivity of self assembled Mg–Co–Zr substituted barium ferrite dot array on carbon nanotube

In this research work, magnetic multi-walled carbon nanotube (MWCNTs) nanocomposites have been created by the assembly of Mg–Co–Zr substituted barium ferrite film onto the surface of MWCNTs. Microwave absorption of the MWCNTs/doped barium ferrite nanocomposites is evidently enhanced compared to that of pure MWCNTs and substituted ferrites. The maximum reflection loss increased significantly with an increase in volume percentage of MWCNTs. Reflection loss evaluations indicated that nanocomposites display a great potential application as thinner and lighter wide-band electromagnetic wave absorbers.

Magnetic and Reflection Loss Characteristics of Substituted Barium Ferrite/Functionalized Multiwalled Carbon Nanotube

Magnetic multiwalled carbon nanotube (MWCNTs) nanocomposites have been created by the assembly of Mg-Ni-Ti substituted barium ferrite nanoparticles onto surface of MWCNTs. X-ray diffraction (XRD) and transmission electron microscope (TEM) were used to demonstrate the successful attachment of ferrite nanoparticles to MWCNTs. Vibrating sample magnetometer (VSM) confirms the relatively strong dependence of saturation of magnetization and coercivity with the volume percentage of MWCNTs. Reflection loss evaluations indicated that the nanocomposites display a great potential application as wide-band electromagnetic wave absorbers.