Electromagnetic Microwave Research Articles

Efficiently enhanced microwave absorption of oriented flaky carbonyl iron&MoS2/polyurethane composite with thin thickness

Herein, we report a novel multi-component electromagnetic microwave absorber with oriented flaky carbonyl iron&MoS2 (FCI&MoS2) as fillers and polyurethane (PU) as matrix. The SEM and VNA were utilized to analyze the morphology, electromagnetic and microwave absorption properties of the prepared oriented FCI&MoS2/PU composites with different multi-component proportions. The reflection loss (RL) and Zin/Z0 values are calculated based on the complex permittivity and permeability. The results demonstrate that the oriented arrangement, synergistic effect and appropriate proportion of FCI&MoS2 fillers are contributed to improve the impedance matching and microwave attenuation of the prepared composites at thin thicknesses of 0.8 mm and 0.9 mm.

Magnetic behavior of Ga doped yttrium iron garnet ferrite thin films deposited by sol-gel technique

Yttrium Iron Garnet (YIG) ferrites thin films having compositional formula Y3GaxFe5-xO12, where (x = 0, 1, 2, 3, 4) are synthesized by sol gel dip coating technique. XRD, SEM and VSM characterizations are employed to explore structural, morphological and magnetic properties, respectively. XRD showed that Ga is completely doped in YIG and not formed any cluster or other phase with YIG. SEM confirmed the formation of agglomeration of YIG particles. Magnetic parameters like coercivity, remnant squareness, saturation magnetization, magnetic moment, anisotropy constant, initial permeability Y–K angles and microwave frequency were calculated of these films. The coercivity and moderate magnetization suggested that fabricated ferrite films are highly applicable in electromagnetic microwave absorption and frequency agile antenna for wireless communication.

Thermal stimulation of shale formations by electromagnetic heating: A clean technique for enhancing oil and gas recovery

Electromagnetic heating has been proposed to environmentally produce shale gas, shale oil, and oil shale. Unlike hydraulic fracturing that cracks shale by tensile and shear stresses through injecting a massive amount of fracturing fluid, electromagnetic heating creates fractures by internal stress caused by the interaction between formation rocks and electromagnetic waves, which eliminates the use of water. In this study, we conducted experiments and simulations to investigate the influential factors, stimulating mechanisms, and fracturing performance of electromagnetic heating for its application in stimulating shales. First, shale samples with different compositions are subjected to electromagnetic (microwave) heating for 3 min. Then, scanning electron microscopy coupled with energy dispersive X-ray, N2-adsorption/desorption, and microscope-imaging are used to characterize pore-structure changes and fracture generation of shale samples. Finally, a finite element theoretical simulation is conducted to investigate the effects of confining pressure, electromagnetic heating power, and time on the stress distributions of the sample. Results show that both macro-fracture and micro-fractures are created after electromagnetic heating; samples either crumble into pieces or fracture into several parts, depending on their clay and pyrite contents. The stimulating mechanisms of electromagnetic heating are shrinkage of clay, and decomposition of organic content, and tensile failure by the heterogeneous expansions of minerals, which significantly enhance the pore space. Moreover, simulations show that the expansion of pyrite induces considerable tension that causes tensile failures to the shale sample, which echoes well with the experimental observations. Confinement can lower the induced tensile stress, which can be overcome by raising the electromagnetic heating power. Our study demonstrates that electromagnetic heating is a promising stimulation technique to eliminate water usage and effectively fracture the shale rock, leading to greener production of hydrocarbon resources from shale.

Fabrication of porous graphene-like carbon nanosheets with rich doped-nitrogen for high-performance electromagnetic microwave absorption

The facile fabrication of lightweight electromagnetic microwave (EM) absorption materials is still in urgent demand due to the increasingly serious electromagnetic pollution and the high requirements of military defense. Herein, nitrogen-rich graphene-like carbon nanosheets (NGs) with porous network structure have been prepared by g-C3N4 template-directed chemical vapor deposition combined with high-temperature treatment process which eliminates the cumbersome template removal, achieving the porosity engineering and high nitrogen doping simultaneously. The conduction loss could be tailored by the configurations of doping N atoms through our method, which plays a dominant role in determining the dielectric behavior in NG materials. The as-prepared NGs with intriguing features possess strong EM attenuation capacity originating from the dielectric loss, the multiple scatterings as well as the balanced impedance match. The optimized NG sample with low loading of only 5 wt% and thin thickness of only 1.8 mm exhibits effective EM absorption performance with the best RLmin of −50.2 dB and the effective absorption bandwidth is about 5.9 GHz at 2 mm. Our work not only provides a promising candidate as effective filler in lightweight EM absorption composites without decoration of other nanomaterials but also valuable insights into the mechanism.

Simultaneous enhancement of recoverable energy density and efficiency of lead-free relaxor-ferroelectric BNT-based ceramics

Given the remarkable performances of Ruddlesden-Popper (RP) type oxides in electronic devices, the study of their intrinsic dielectric, magnetic and electromagnetic microwave (EMW) absorption properties are still missing. Herein, two kinds of Lead-free relaxor-ferroelectric BNT-based ceramic hierarchical polycrystalline alloys (La3Ni2O7/LaNiO3, La2NiO4/La2O3) were prepared via a facile solvothermal and high-temperature annealing technique as high-performance EMW absorption materials (MAMs). By a means of adjustment of solvothermal time in the precursor systems, Nickel salt layers precipitation declined gradually. The phase and crystal state of the powders were characterized by X-ray diffraction (XRD) with refinement treatment (Rietveld analysis). XPS was utilized on the determination of interstitial O2– quantitatively in La3Ni2O7+δ (δ = 1.95) and La2NiO4+δ (δ = 0.75). Responsible to the synergistic effect of dielectric and magnetic response and well-matched impedance, the as-fabricated MAMs performed excellent wave absorbability, especially in low frequency (S-band). In details, La3Ni2O7/LaNiO3 achieved optimal effective absorption band (fE) 3.36 GHz at 9.52–12.80 GHz and a minimum reflection loss (RLmin) −43.30 dB with a thickness of 2.2 mm. Moreover, La3Ni2O7/LaNiO3 and La2NiO4/La2O3 overcame the challenge of absorbers’ thickness in S-band, of which the RL reached –22.63 and −29.90 dB at 0.7 mm, respectively. Noteworthily, La3Ni2O7/LaNiO3 obtained RL value of −50.06 dB at 10.72 GHz with a device thickness of 2.8 mm. It is emphasized that this report has interpreted the EMW absorption capacity and mechanism exhaustively, which will initiate simultaneous enhancement of recoverable energy density and efficiency application of RPs.

Mass production of two-dimensional materials beyond graphene and their applications

Two-dimensional (2D) materials are promising candidates in wide applications including energy storage and conversion, sensors, flexible devices, etc. The low-cost production of 2D materials with large quantities and demanded quality is the precondition for their commercial uses. For graphene and its derivatives, relatively mature techniques have been established for their scalable preparation and industrial applications. Whereas the mass production of 2D materials beyond graphene is still in its early age and it lacks a summary on this topic. This review systematically describes the state-of-the-art approaches for high-yield preparation of 2D materials beyond graphene, including “top-down” exfoliation and “bottom-up” synthetic approaches. In particular, each method is discussed from the perspectives of its principle, optimization attempts, characteristics of the obtained 2D materials, and its scalability potential. The applications that require massively-produced 2D materials are highlighted, including electrocatalysis, batteries, supercapacitors, mechanical and chemical sensors, as well as electromagnetic interference shielding and microwave absorption devices. Finally, we propose the challenges and opportunities for scalable preparation and commercial applications of 2D materials.

Electromagnetically Induced Acoustic Transparency with a Superconducting Circuit

We report the observation of electromagnetically induced transparency (EIT) of a mechanical field, where a superconducting artificial atom is coupled to a 1D-transmission line for surface acoustic waves. An electromagnetic microwave drive is used as the control field, rendering the superconducting transmon qubit transparent to the acoustic probe beam. The strong frequency dependence of the acoustic coupling enables EIT in a ladder configuration due to the suppressed relaxation of the upper level. Our results show that superconducting circuits can be engineered to interact with acoustic fields in parameter regimes not readily accessible to purely electromagnetic systems.

A Fast Modeling Algorithm for Quasi-Periodic Array

With the development of electromagnetic theory and microwave engineering, researchers have proposed many novel quasiperiodic arrays to realize various functions in controlling electromagnetic wave propagation. They have similar elements located on the periodic lattices. Full-wave simulation of the quasi-periodic arrays is necessary and challenging, because the whole array is usually electrically large and multiscale. In this communication, we study a fast algorithm for the full-wave modeling of the quasi-periodic arrays. It constructs a reduced basis set based on the geometric similarities among the array elements. Then, we use linear projection to “recover” periodicity numerically so that the fast Fourier transform can be used to accelerate the computation of the whole array. The computational complexity of this algorithm is O(NlogN), where N is the number of elements in the array. Numerical examples verify its potential in solving large-scale quasi-periodic arrays.

A facile fabrication and high-performance electromagnetic microwave absorption of ZnO nanoparticles

Abstract Electromagnetic microwave absorption materials are highly desired in electronics application in recent years. Herein, ZnO nanoparticles were successfully fabricated via sonochemical process using zinc acetate dihydrate (Zn(CH3COO)2·2H2O) and ammonia water as raw materials. The as-prepared ZnO nanoparticles annealed at 120 °C for 8 h had significantly enhanced electromagnetic microwave absorption properties. This could be attributed to dielectric loss originating from interface polarization, and dipole polarization due to oxygen vacancy defects. The minimum reflection coefficient reached −37.7 dB at 8.96 GHz with a small thickness of 2.1 mm. This work provides a new idea of preparing electromagnetic microwave absorption materials (MAMs) with strong absorbing properties.

Fabrication of ferroferric oxide–carbon/reduced graphene oxide nanocomposites derived from Fe-based metal–organic frameworks for microwave absorption

Microwave absorbers with strong absorption, broad bandwidth, thin thickness and low filler loading are highly desirable in electromagnetic absorption field. In this work, ferroferric oxide–carbon/reduced graphene oxide (Fe3O4–C/RGO) nanocomposites were fabricated by a facile solvothermal and high-temperature pyrolysis two-step strategy. Results of morphology observations demonstrated that numerous carbon frameworks with unique octahedral morphology were uniformly loaded on the crumpled surfaces of thinly flake-like RGO, and that well-designed entanglement structure consisting of octahedral carbon frameworks and crumpled RGO was observed in the as-prepared nanocomposites. Moreover, the effects of additive amounts of graphene oxide and filler loadings on the electromagnetic parameters and microwave absorption properties of as-synthesized nanocomposites were elaborately investigated. Remarkably, the obtained nanocomposites with an additive amount of graphene oxide of 2.43 wt% displayed the minimum reflection loss of −60.5 dB at 4.8 GHz with a matching thickness of 3.6 mm and effective absorption bandwidth (reflection loss less than −10 dB) of 5.5 GHz (from 11.2 to 16.7 GHz) with an ultrathin thickness of merely 1.5 mm. Besides, the possible microwave absorption mechanisms were proposed. This work could shed light on designing and fabricating carbon-based magnetic nanocomposites as lightweight and high-performance microwave absorbers.

Novel high-performance electromagnetic absorber based on Nitrogen/Boron co-doped reduced graphene oxide

In this work, N/B co-doped reduced graphene oxide were successfully synthesized with two-step hydrothermal self-assembled process, and exhibited excellent electromagnetic microwave absorption under a loading content of only 5 wt%. Its absorption bandwidth below −10 dB was 6 GHz at a thickness of 2.8 mm, and the minimum reflection loss was −52 dB. The nitrogen/boron co-doping mechanism and influences of multiple atomic bonding configurations on the absorbing properties were investigated in detail. The results suggested that various atomic bonding configurations, including C–N bonds (essentially for pyridinic N and pyrrolic N) with electron donor properties and C–N–B bonds with electron acceptor properties, played synergistic role in improving the electromagnetic absorption performance. The equivalent electric diploe composed of various atomic bonding configurations with electronic resonances, consumed the electromagnetic energy in the manner of “molecular” thermal vibration, and endowed the absorber with impedance matching and good electromagnetic attenuation ability.

Self-etching template method to synthesize hollow dodecahedral carbon capsules embedded with Ni–Co alloy for high-performance electromagnetic microwave absorption

We employ self-etching template method to prepare an ideal electromagnetic wave (EMW) absorber, which is hollow dodecahedral carbon capsules embedded with Ni–Co alloy particles. The hollow dodecahedral polydopamine (PDA) capsules are constructed by the Ni(OH)2/ZIF-67 template automatically etched off during in situ polymerization of Dopamine·HCl. N-doped carbon capsules (NCs) embedded with Ni–Co alloy particles (named as Air@NCs€Ni–Co) are obtained after the thermal treatment of Ni(OH)2/ZIF-67@PDA. The EMW absorption performance of Air@NCs€Ni–Co has been tuned by different contents of Ni(OH)2 at 700 oC. The minimum reflection loss (RLmin) value is −36.5 dB at 14.77 GHz with a thickness of 2.2 mm. The effective bandwidth (RL < −10 dB) can reach up to 6.55 GHz (from 11.45 to 18 GHz) with a thickness of 2.3 mm, which covers the whole Ku band. Potentially, our study provides a new platform for subtly building hollow dodecahedral carbon capsules embedded with alloy particles using ZIF as self-etching template.

Facile synthesis of hierarchical A-site cation deficiency perovskite LaxFeO3-y/RGO for high efficiency microwave absorption

Wafer biscuit structure like hierarchical A-site cation deficiency perovskite at carbon and RGO hybrid composites-LaxFeO3-y/RGO are fabricated by a simple one-pot route. The quantitative ratios of A-site cation deficiency are designed, and was represented by x = 1.0, 0.8, 0.6, 0.4 and 0.2, respectively. Besides the morphology and phase structure, but the chemical composition, especially the O vacancy induced by the deficiency, was also studied by X-ray photoelectron spectroscopy (XPS) data. The electromagnetic microwave absorption capabilities of these composites were further studied. Accompanying with the appearance of A-site cation deficiency, the reflection loss (RL) was optimized instinctively. The minimum RL of La0.8FeO3-y/RGO reaches −36.23 dB with an effective band (RL ≤ −10dB) width of 3.92 GHz from 11.68 to 15.60 GHz at the matching thickness 2.00 mm, which was demonstrated the domain role of dielectric loss ascribed to the polarization of dipoles between O vacancy and Fe4+. When the deficiency increased, the band widths reached 4.72 GHz with the synergistic effect of magnetic and dielectric phase.

Raman and XPS depth profiling technique to investigate the corrosion behavior of FeSiAl alloy in salt spray environment

Abstract As a promising material for electromagnetic microwave absorption, FeSiAl (FSA) alloy always suffers from inadequate corrosion resistance in the marine environment. Herein, the Raman and X-ray photoelectron spectroscopy (XPS) depth profiling techniques are adopted to investigate the basic corrosion behavior of FSA in salt spray environment. The Raman analysis contributes to the understanding of the composition change at various corrosive periods while the XPS depth profiling reveals the corrosion process of Fe0→Fe2+→Fe3+ in a sequence. The observed corrosion rates (CRs) of FSA immersed in 5 wt% NaCl solution for 1, 24 and 48 h are 2.99 × 10−12, 4.90 × 10−12 and 5.85 × 10−12 m/s, respectively. The increasing value of CRs as a function of time demonstrates the accelerated corrosion tendency. Moreover, to suppress the corrosive behavior of FSA alloy, carbon is decorated on its surface by catalytic chemical vapor deposition method using acetylene as the carbon source. The carbon coating restrains the corrosion process by impermeability and hydrophobicity of carbon materials in corrosive mediums. This study will help in the designing of microwave absorbers which can resist corrosion in harsh reaction conditions as well as available at commercial level to save the economy.

Design and study of slow wave structure of the THz folded waveguide TWT over 60W

In this paper, the equivalent circuit method is used to analyze the dispersion characteristics of the folded waveguide and calculate the coupling impedance. The influence of the surface roughness and conductivity of the waveguide on the loss of the high frequency circuit is considered. In order to improve the efficiency of the beam wave interaction, the two kinds of slow wave structures of the folded waveguide TWT are designed by using the variable period technology. The three-dimensional electromagnetic software Microwave Tube Simulation Software (MTSS) is used to simulate the beam wave interaction of TWT. After optimization, the output power of both structures is over 60W, the electronic efficiency is more than 5.5%and the gain is greater than 32dB in the 211GHz-221GHz frequency range.

Preparation and properties of functional particle Fe3O4-rGO and its modified fiber/epoxy composite for high-performance microwave absorption structure

Microwave absorbing materials have been becoming a countermeasure and security media for radio environment, and also been becoming the main military force attached by the world. In this study, experimental data, theoretical researches and FEKO—a 3D structure and electromagnetic field analysis simulation tool, namely, FEldberechnung bei Korpern mit beliebiger Oberflache, are effectively combined. Through systematic studies on electromagnetic parameters and microwave absorbing properties of high-performance absorbing functional particle Fe3O4-rGO (i.e. reduced graphene oxide), single-layer composite Fe3O4-rGO@EP/GF (epoxy/glass fiber) and multi-layer structure composite Fe3O4-rGO@EP/fiber, combined with the simulation calculations of material structures, design on the microwave absorption performances of fiber/resin structural composites is achieved. In particular, under the guidance of FEKO simulations, a multi-layer structure composite with two layers of Fe3O4-rGO@EP/GF with different Fe3O4-rGO added amounts as the absorbing layer and carbon fiber (CF) reinforced EP as the reflecting layer is prepared, which has an effective absorption bandwidth of 8.43–12.40 GHz, almost covering the whole X-band, and RLmin (minimum reflection loss) up to −34.60 dB at 10.37 GHz. The relevant experimental results are basically consistent with the FEKO simulation results. This study is helpful to improve the developing efficiencies and properties of microwave absorbing structure composites with both excellent mechanical properties and outstanding microwave absorbing performances, especially conducive to industrial productions.

Microwave heating as an alternative lifting method for the heavy oil deposits

In providing solution for lifting the viscous oil which is immensely concerned in mature field, thermal recovery is commonly applied to recover the oil with API gravities approximately 20 0API by using steam injection and in situ combustion. It had been the way out to lower enough the viscosity so that the oil would flow toward more effortless than the viscous one for the recent times. Applying electromagnetic microwave to heat up the reservoir can overcome the depth limitation which is often found in conventional thermal recovery methods. This method uses the Nano-ferro fluid as a stimulant that conveniently radiate heat in a reservoir. It is important to analyse the brine formation in affecting the optimization of thermal period while the Nano-ferro fluid being directly introduced to formation fluid. Therefore, NaCl solution becomes variable which was used to represent brine formation in investigating the heating time of saturated artificial cores. Meanwhile optimal concentration of Nano-ferro had been recognized. The microwave was also varied in sequence of power, 378-Watt, 468-Watt, 657-Watt, 792 Watt, and 900 Watt. For example, applying 50,000 ppm, 100,000 ppm, and 350,000 ppm in performing investigation that would give significant performance while thermal process. When 657 Watt was set to heat up the compartment contained artificial core, the temperature could reach up to 90 °C in 110 seconds, 82 seconds, and 54 seconds consecutively from low to high NaCl solution. In that way, the sensitivity of this variable was proved that NaCl solution greatly affect the temperature increment in times. Furthermore, this research can be considerable study in finding out the behaviour of formation fluid which contribute in optimizing for Nano-ferro fluid thermal recovery.

A tri-band left-handed meta-atom enabled designed with high effective medium ratio for microwave based applications

This paper represents a tri-band left-handed meta-atom with high effective medium ratio, which is applicable for tri-band microwave based communication applications. The proposed meta-atom consists of modified complementary split ring resonator (CSRR) with two pi shaped metal strip loaded in the inner side. It shows the behavior of negative permeability and permittivity at 2.85 GHz, 4.83 GHz, 8.39 GHz, and 11.42 GHz resonance frequencies and extracted the double negative (DNG) metamaterial properties. The designed meta-atom dimension is 0.076λ×0.076λ at lower resonance frequency. To develop and analyze the offered meta-atom, the electromagnetic (EM) simulator CST Microwave Studio and MATLAB software were used. The equivalent circuit with RLC components of the proposed metamaterial unit cell is also investigated through ADS simulator and comparing S parameter (transmission coefficients) results with CST results. Analysis and comparison have been carried out with different configurations, such as various design structures, distinct substrate, changing the gap of the splits, and various array measures. All the array configurations proved that the frequency of operation is in the S-, C-, and X-bands. The designed meta-atom has double negative regions of 2.89–2.96 GHz, 4.84–4.99 GHz, 8.42–8.49 GHz, and 11.43–12.32 GHz, with the regions of effective negative refractive index 2.85–3.09 GHz, 4.83–5.36 GHz, 8.40–8.57 GHz, and 11.40–12.55 GHz, respectively. The effective medium ratio is 13.16; this implies that the proposed miniaturized meta-atom design is efficient and compact. The scattering parameter dimension of the meta-atom promising for the microwave based applications at S-, C-, and X-bands.

Design and X-Band electromagnetic response of single negative metacomposite containing periodic curved Co-based ferromagnetic microwires

Metamaterials possess attractive electromagnetically left-handed properties yet their nature as an artificial structure rather than a material restricts their further applications. In this article we propose to use Co-based ferromagnetic microwires as periodical metamaterial units interweaved into a fabric to realize a “metacomposite” for steering wave propagation. By introducing ferromagnetic microwires in quartz fabric at three curvatures and periodic lengths, the electromagnetic response and microwave behaviors on both horizontally- and vertically-arranged directions were presented and investigated. Tensile behaviors of metacomposites with different ferromagnetic microwire morphologies were monitored by non-contact full field strain measurement system. At X band (8.2–12.4 GHz), metacomposites containing vertically-arranged ferromagnetic microwires show negative permittivity due to the dielectric resonance of microwire arrays. The dielectric response of metacomposites conformed to Lorentz-oscillator mode, behaving similarly to diluted plasma. When ferromagnetic microwires reached the lowest periodic curved length 2.5 mm with the highest curvature was obtained, the metacomposites presented the maximum microwave absorption of 34% and tensile stress of 273 MPa. The incorporation of ferromagnetic microwires exerts trivial influence on the mechanical properties yet homogenizes the strain and reduces the stress concentration on metacomposites. The metacomposite with a periodic curved length of 7.5 mm has less interweaving points and the highest surface float length, therefore achieving the maximum tensile strength of 458 MPa. The single negative metacomposites containing ferromagnetic microwires are featured with excellent structural properties and amenable microwave left-handed properties in controlling wave-propagating behavior, which is of practical engineering significance in structural health monitoring, sensing and stealth applications.

Three-dimensional (Fe3O4/ZnO)@C Double-core@shell porous nanocomposites with enhanced broadband microwave absorption

The synergistic effect of magnetic and dielectric materials makes this kind of composite as an ideal microwave absorber. So far, composite absorbing materials of Fe3O4 and carbon have been extensively studied and achieved excellent absorption properties. However, this type of absorber always has the problem of narrow effective absorption band (RL ≤ −10 dB). In this article, we have prepared 3D (Fe3O4/ZnO)@C double-core@shell nanocomposites by a clever method. Especially, the electromagnetic parameters and microwave absorption performances of the nanocomposites can be tuned by changing the zinc content. When the molar ratio of Zn to Fe is 1:2, the effective absorption bandwidth of the double-core@shell nanocomposite is 6.4 GHz with 2 mm thickness and 7.11 GHz with 1.9 mm thickness. Besides, when Zn:Fe = 1:1, the double-core@shell nanocomposite achieves a minimum RL value of −40 dB at 15.31 GHz with 2 mm thickness and has a wideband effective absorption of 6.5 GHz and an efficient absorption bandwidth (RL ≤ −20 dB) of 3.4 GHz. The special 3D double-core@shell structure and ingenious introduction of tunable ZnO could improve the microwave absorption performances of the (Fe3O4/ZnO)@C nanocomposites, which can be considered as promising absorbing materials.