Composite wave-absorbing structure combining thin plasma and metasurface

Efforts to produce microwave absorber materials that are inexpensive and environmentally friendly have become a means of greening the environment. The breakthrough can be focused on industrial waste and natural materials for functional purposes and how to enhance their performance. We successfully synthesized nickel slag/laterite soil (NS/LS) and nickel slag/iron sand (NS/IS) nanocomposites using a simple mechanical alloying technique, and the electromagnetic (EM) wave absorption capacities of the nanocomposites were measured using a vector network analyzer. The structural properties of the nanocomposites were analyzed by X-ray diffraction spectroscopy, where the results of the analysis showed that NS/IS has the largest crystallite size (15.69 nm) and the highest EM wave absorption performance. The optical properties of the nanocomposites were determined from their Fourier transform infrared spectra using the Kramers-Kronig relation. As determined through a quantitative analysis of the optical properties, the distance between the longitudinal and transversal optical phonon wavenumber positions (Δ(LO - TO) = 65 cm-1) is inversely proportional to the reflection loss. The surface morphologies of the nanocomposites were analyzed by scanning electron microscopy, and the particle diameters were observed by binary image and Gaussian distribution analyses. The nanocomposite surface exhibits a graded-like morphology, which indicates multiple reflections of the EM radiation, consequently reducing the EM interference. The best nanocomposite for an attenuated EM wave achieved a reflection loss of -39.14 dB at 5-8 GHz. A low penetration depth has implications for the electrical charge tuning of the storage and composite magnets. Finally, the EM absorption properties of NS/IS and NS/LS indicate a 2-mm-thick environmentally friendly nanocomposite for EM absorption.

Electromagnetic wave absorption properties of Ni0.5Zn0.5Fe2O4–BaTiO3–epoxy composites

The synthesis of an iron tailings-based geopolymer with synergistic electromagnetic wave consumption property.

Electromagnetic (EM) waves are used in the oil and gas industry to identify the geology of the formation and the type of the fluid saturating the medium. There is also an interest to use the electromagnetic waves as an enhanced oil recovery (EOR) method. However, interpretation of logging data generated through electromagnetic waves or determination of the electromagnetic wave propagation in a medium as an EOR method are not easy tasks. This study aims to identify the role of different geological settings with different types of fluid saturations in the response of electromagnetic wave propagation and absorption. To reach this objective multitude-systematic laboratory scale experiments were conducted on different reservoirs fluid and rock pairs. As reservoir mineralogy, different grain size of quartz, clay, or limestone is used to prepare the reservoir rocks at different porosity. Water is known as a good absorber for EM waves, thus, pore space were saturated at different water saturations and a bitumen sample (10,000 cP, 12° API) from Canada. Prepared samples were packed into in-house-built-Plexiglas core holder which allows measurements with EM waves. The response of EM waves propagation and absorption was measured by using a vector network analyzer at varying frequencies (500 MHz to 4 GHz) through dielectric properties (dielectric constant, loss tangent, and penetration depth). The results were used to obtain correlations between dielectric properties and physical properties (reservoir rock mineralogy, porosity, water saturation, and oil saturation) of the reservoir rock-fluid blends. Water saturation gives a perfect correlation with dielectric constant and loss tangent values of the saturated medium. Because dielectric constant and loss tangent parameters provide an idea on the absorption characteristics of EM wave in the medium, and because water is a strong EM wave absorber, as it was expected, with the increase in water saturation, the dielectric constant and loss tangent parameters of the medium are also increased; on the other hand, penetration depth was decreased. With the increase in quartz content in the medium, it has been observed that EM wave penetration is enhanced. As a result, several correlations were created in this study and they can be used to better interpret the reservoir mineralogy and fluid saturation as a response to EM wave logging. Moreover, these results can be used to estimate the effective area (penetration depth) of EM wave as an EOR method in different mediums.

The development of advanced electromagnetic wave absorbing materials capable of simultaneous dual/multiple frequency bands has received widespread attention due to their potential to mitigate electromagnetic interference and enhance communication technologies. Herein, we report efficient dual frequency band electromagnetic wave (EMW) absorption from a hybrid of high-purity Cu2NiSnS4 (CNTS) nanoparticles and reduced graphene oxide (rGO) (CNTS/rGO). The surface morphology and physicochemical properties of prepared materials (pure CNTS and CNTS/rGO with different rGO filling ratios) were characterized using powder X-ray diffraction (PXRD), Raman spectroscopy, transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and scanning TEM (STEM) analysis. The electromagnetic-wave-absorption performances were conducted using a vector network analyzer with the frequency ranging between 2 and 18 GHz. The complex permittivity, magnetic permeability, dielectric loss tangent, magnetic loss tangent, dielectric relaxation phenomena (Cole–Cole plot), eddy current loss parameter, and attenuation constant values related to the electromagnetic wave absorption of the materials have been studied. The experimental results confirmed that CNTS and CNTS/rGO composite materials can absorb different electromagnetic wave frequency bands. Significantly, CNTS/rGO (50%) exhibits exceptional electromagnetic-wave-absorption properties across dual frequency bands with the optimal absorption loss of −38.2 dB at 17.1 GHz and a broad absorption peak of −10.4 dB at 5.6 GHz, offering significant potential for use in various technological applications, including stealth technology, wireless communication, and radar systems. The enhanced microwave-absorption properties of the material can be attributed to the successful design of a well-dispersed heterostructure of CNTS/rGO containing different phases, including a hybrid of dielectric and magnetic material along with the efficient dielectric loss, magnetic loss, and their synergistic contribution in the electromagnetic wave absorption. The outcomes of this research can lead to technological advancements, improved functionality, and future direction to pressing challenges in today’s interconnected world.

Applications for an antenna structure produced with additive manufacturing technology are numerous and promising. This study focuses explicitly on utilizing micro‐laser sintering (MLS) three‐dimensional (3D) printing technology to fabricate two rectangular horn antennas identical to a standard Pasternack® horn antenna, making the fabrication straightforward. The objective is to investigate how surface roughness affects antenna performance in a frequency range of 18 to 26.5 GHz. One antenna is polished and the other is left untouched, resulting in surface roughness of 4 and 6 µm, respectively, measured using a profilometer. Then, a vector network analyzer was used to assess their reflection coefficient, transmission characteristics, and radiation pattern and determine gains of 8.83 and 9.14 dBi for the polished and unpolished antennas, respectively. The study finds that both polished and unpolished antennas perform similarly, and their characteristics closely resembling simulated and standard antennas. Finally, the performance of the MLS‐printed metallic antennas is compared with horn antennas created using other 3D printing techniques. It reveals that the MLS‐printed metallic structures exhibit better performance, indicating that the MLS technology has great potential to print 3D metallic electromagnetic designs.

This paper analyzes the measurement of ultra wideband (UWB) noise channels in different indoor environments. All measurements are done using a vector network analyzer (VNA) which allows us to measure the noise channel transfer functions. We find that the noise power of the system is decreased by increasing the intermediate frequency (IF) bandwidth which leads to an increase in time taken to perform measurements of the channels. The environmental noise power been measured and find that it decreased when enclosed in a Faraday cage (steel shed), within an intense multipath measurement environment. Also, the Environmental noise decreases slightly by using the LPDA antenna compared to using the Teardrop and Horn antennas. Our results show that the Horn antenna is less suitable for UWB channel measurements compared to the LPDA directional antennas because of lower S11 (Return Loss) values. While for omnidirectional antennas, the Teardrop antenna is much more suitable than the monocone antennas for UWB measurements (due to lower S11 values) and decreases the Environmental noise power. As secondary application, we show how a frequency detection device can be used to re-adjust a maladjusted frequency selection on a remote controller for a garage door, in presence of environmental noise power.

Absorber materials are developed to reduce electromagnetic radiation and ensure the compatibility of the operation of electronic equipment in environments subject to interference. This work presents the development of a low-cost textile electromagnetic absorber for 4G and 5G technologies, operating at frequencies of 2.5 GHz and 3.5 GHz. The proposed electromagnetic absorber utilizes a 1 mm-thick Denim substrate, with a graphite composite used in the agricultural and commercial polyvinyl acetate glue industry, with the relationship of 25 wt%. The measurements were carried out in a Vector Network Analyzer, model E5071C Agilent Technologies, with the characterization of the Denim substrate, the glue, and the identification of the best parameters for the construction of the absorber. In the project, three low-cost textile absorbers prototypes were fabricated, with G1 = 0.25 mm, G2 = 0.35 mm, and G3 = 0.5 mm of thickness layers of the composite deposited on a Denim fabric. The results indicate that the absorber prototypes G2 presents great results in the frequency range of 4G and 5G band, with a maximum absorption of 26.6 dB in 3.94 GHz, with a structure 98.83% thinner than the commercial absorber LF-75. The variation in absorption performance may be attributed to the different mechanisms by which the absorbers operate: the commercial absorber LF-75 primarily interacts with the magnetic field, whereas the textile prototype predominantly affects the electric field.

Objective: To prepare zinc ferrites materials and study the sintering effect on the structural and microwaves absorption in the X-band rang. Methods/Statistical Analysis: Zinc Ferrite nanoparticles have been prepared by using the sol-gel methods. The samples were sintered at three temperatures (400°C, 600 °C, 800 °C) for two hours. The spinal phase of zinc ferrite structure and crystallite size was examined by XRD spectrum, pattern show that nanoparticles structure exhibit mixed phase of ZnO and ZnFe2O4.Atomic force microscopy (AFM) was used to study the surface topography. AFM images reveal a uniform distribution of semispherical shaped nanostructure with average grain sizes ranging between (70.71 nm -92.03 nm). The microwave absorption in X-band rang was examined with a vector network analyzer (VNA). Findings/ Application: The maximum microwave absorbance at 9 GHz for sample sintering at 800 °C with narrow bandwidth (8.5- 9.5 GHz). The minimum the attenuation coefficient is less than -15 dB with absorber thickness (1.2 cm) for all samples.

Owing to their high permeability, metallic soft magnetic materials exhibit high potential as microwave absorbers. The great challenge in designing desirable absorption properties from these materials is their large electrical permittivity at microwave frequencies. So, decreasing their permittivity within acceptable limits while keeping permeability at sufficiently high or improved levels is considered an important requirement for matching impedance and obtaining excellent electromagnetic (EM) absorption properties. In the present research, FeCo alloy particles produced employing by a simple wet chemical reduction process with the intention of investigating dependence of their EM properties on synthesis parameters. The characterizations were done with the help of x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). The intrinsic EM properties (εr, μr) in a frequency range of 2–18 GHz were measured by a vector network analyzer (VNA) for the paraffin composites containing obtained products. The results indicated that the concentration of NaOH and metallic salts as the synthesis precursors can tune the permittivity and permeability. Under optimum conditions, bandwidths of 7.3 and 5.5 GHz with thicknesses of only 1.2 and 1.5 mm were obtained respectively. Also, Reflection loss (RL) of −45 dB was attained. The excellent EM absorption properties demonstrated that the synthesized FeCo alloy may be an ideal absorber having both a wide absorption bandwidth and a low thickness.

Constructing multiple heterogeneous interfaces in porous bimetallic FeNi3/C and CoNi/C flowers towards brilliant electromagnetic wave absorption performance

Although microstructure optimization is an effective strategy to improve and regulate electromagnetic wave (EMW) absorption properties, preparing microwave absorbents with enhanced EMW absorbing performance and tuned absorption band by a simple method remains challenging. Herein, ZnIn2S4/reduced graphene oxide (rGO) composites with flower-like and cloud-like morphologies were fabricated by a convenient hydrothermal method. The ZnIn2S4/rGO composites with different morphologies realize efficient EMW absorption and tunable absorption bands, covering a wide frequency range. The flower-like structure has an optimal reflection loss (RL) of up to -49.2 dB with a maximum effective absorption bandwidth (EAB) of 5.7 GHz, and its main absorption peaks are concentrated in the C and Ku bands. The minimal RL of the cloud-like structure can reach -36.3 dB, and the absorption peak shifts to the junction of X and Ku bands. The distinguished EMW absorption capacity originates from the uniquely optimized microstructure, complementary effect of ZnIn2S4 and rGO in dielectric constant, and synergy of various loss mechanisms, such as interfacial polarization, dipole polarization, conductive loss, and multiple reflections. This study proposes a guide for the structural optimization of an ideal EMW absorber to achieve efficient and tunable EMW absorption performance.

Synthesis of ZnS quantum dots and CoFe2O4 nanoparticles co-loaded with graphene nanosheets as an efficient broad band EM wave absorber

Enhanced electromagnetic wave absorption properties of PDCs-SiCN(Ni) fibers by in-situ formed CNTs and Ni2Si

Multifunctional BiFeO3 composites: Absorption attenuation dominated effective electromagnetic interference shielding and electromagnetic absorption induced by multiple dielectric and magnetic relaxations