Electromagnetic Waves Research Articles

Application of N-doped NiCo2O4 / NiO / Co3O4 composites rich in oxygen vacancies in electromagnetic wave absorption.

In this work, N-doped and oxygen vacancy-rich NiCo2O4/NiO/Co3O4 composites are synthesized by the direct calcination method. Noticeably, by changing the additive concentrations of urea dissolved in DMF (N-N dimethylformamide), the electromagnetic (EM) wave absorption abilities of NiCo2O4/NiO/Co3O4 composite effectively. A maximum reflection loss (RLmax) value at 12.94 GHz for a 2.8 mm thick sheet is -29.76 dB, while its effective absorption bandwidth (EAB) (RL<-10 dB) reaches 4.21 GHz. In-depth research of possible mechanisms of EM wave absorption enhancement. Owing to its simple preparation method and superb EM wave absorption properties, the NiCo2O4/NiO/Co3O4 composites have a chance to be suitable candidates for high-property EM wave absorbers.

Activating Excellent Electromagnetic Wave Absorption of Micromorphology-Optimized Cu/C Nanocomposite Fibers via a Metal-Organic Framework Template-Assisted Strategy.

Morphological engineering is crucial for conceiving high-efficiency electromagnetic wave (EMW) absorption materials. However, for carbon fiber-based composites, the management of micromorphology is significantly astricted by complex fabrication. It remains highly challenging to clarify the micromorphological influences on the EMW loss mechanism of carbon fiber-based absorption materials. In this work, micromorphology-optimized Cu/C nanocomposite fibers are prepared by virtue of a metal-organic framework (MOF) template-assisted strategy. Through skillfully grafting the morphology-regulation capacity of MOFs onto composite fibers, the Oswald maturation and particle distribution issues of Cu nanoparticles are settled, and the efficient electron transport pathways are established by the bead-like structure of the fiber matrix. Compared to prepared conventional Cu/C nanocomposite fibers, the MOF template-assisted strategy stimulates a remarkable leap in EMW absorption performance. The minimum reflection loss value of Cu/C-40 can reach -64.5 dB, 15.96 times lower than that of a conventional sample (Cu/C-2). The maximum effective absorption bandwidth extends to 6.08 GHz, contrasting the ineffective performance of Cu/C-2. Systematic research demonstrates that the enabled graphite-catalytic function of Cu nanoparticles collaborated with an optimized conductive network structure plays a pivotal role in creating field-induced leakage currents, facilitating conductive loss, the primary contributor to EMW dissipation. This work establishes a correlation mechanism between micromorphology and EMW loss, presenting a compelling example of customizable carbon fiber-based absorbers.

Novel fire-resistant SiBCN fiber paper with efficient electromagnetic interference shielding and Joule-heating performance

Since electromagnetic interference (EMI), icing, and fire incidents greatly threaten aviation safety, multifunctional EMI shielding materials are urgently required in the aviation industry. However, developing highly efficient EMI shielding materials that combine fire resistance and thermal management remains a significant challenge. Here, a novel fire-resistant SiBCN ceramic fiber paper with excellent EMI shielding and Joule heating performance was fabricated via electrospinning followed by cross-linking, pyrolysis, and annealing. Compared with the SiBCN fiber paper prepared at 800 °C with poor EMI shielding performance, the total shielding effectiveness (SET) of the SiBCN fiber paper annealed at 1400 °C significantly increased to 21 dB, with specific shielding effectiveness (SSE/t) as high as 3317 dB•cm2•g−1, due to the precipitation of “island-like” conductive turbostratic C, facilitating the synergistic effects of conduction loss, dipole polarization, and interfacial polarization, resulting in high efficiently attenuation of the electromagnetic waves (EMW). Furthermore, the fiber paper demonstrated excellent fire-resistant and Joule-heating performance, with a rapid electrothermal conversion response and a high saturation temperature of 300 °C at 12 V. Therefore, this work proposes a novel strategy for designing multifunctional ceramic fiber paper with integrated EMI shielding, fire resistance, and Joule heating performance for aircraft safety.

Integrating electromagnetic cancer stress with immunotherapy: a therapeutic paradigm

An array of published cell-based and small animal studies have demonstrated a variety of exposures of cancer cells or experimental carcinomas to electromagnetic (EM) wave platforms that are non-ionizing and non-thermal. Overall effects appear to be inhibitory, inducing cancer cell stress or death as well as inhibition in tumor growth in experimental models. A variety of physical input variables, including discrete frequencies, amplitudes, and exposure times, have been tested, but drawing methodologic rationale and mechanistic conclusions across studies is challenging. Nevertheless, outputs such as tumor cytotoxicity, apoptosis, tumor membrane electroporation and leak, and reactive oxygen species generation are intriguing. Early EM platforms in humans employ pulsed electric fields applied either externally or using interventional tumor contact to induce tumor cell electroporation with stromal, vascular, and immunologic sparing. It is also possible that direct or external exposures to non-thermal EM waves or pulsed magnetic fields may generate electromotive forces to engage with unique tumor cell properties, including tumor glycocalyx to induce carcinoma membrane disruption and stress, providing novel avenues to augment tumor antigen release, cross-presentation by tumor-resident immune cells, and anti-tumor immunity. Integration with existing checkpoint inhibitor strategies to boost immunotherapeutic effects in carcinomas may also emerge as a broadly effective strategy, but little has been considered or tested in this area. Unlike the use of chemo/radiation and/or targeted therapies in cancer, EM platforms may allow for the survival of tumor-associated immunologic cells, including naïve and sensitized anti-tumor T cells. Moreover, EM-induced cancer cell stress and apoptosis may potentiate endogenous tumor antigen-specific anti-tumor immunity. Clinical studies examining a few of these combined EM-platform approaches are in their infancy, and a greater thrust in research (including basic, clinical, and translational work) in understanding how EM platforms may integrate with immunotherapy will be critical in driving advances in cancer outcomes under this promising combination.

RGO aerogel embedded with organic–inorganic hybrid perovskite for lightweight broadband electromagnetic wave absorption

rGO aerogel embedded with organic–inorganic hybrid perovskite for lightweight broadband electromagnetic wave absorption

Resonant switching current detector based on underdamped Josephson junctions

Current-biased Josephson junctions can act as detectors of electromagnetic radiation. At optimal conditions, their sensitivity is limited by fluctuations causing stochastic switching from the superconducting to the resistive state. This work provides a quantitative description of a stochastic switching current detector, based on an underdamped Josephson junction. It is shown that activation of a Josephson plasma resonance can greatly enhance the detector responsivity in proportion to the quality factor of the junction. The ways of tuning the detector for achieving optimal operation are discussed. For realistic parameters of Nb/AlOx/Nb tunnel junctions, the sensitivity and noise-equivalent power (NEP) can reach values of S≃5×1012 (V/W) and NEP≃2×10−23 (WHz−1/2), respectively. These outstanding characteristics facilitate both bolometric and single-photon detection in microwave and terahertz ranges. Published by the American Physical Society 2024

Photosensitized Oxidation of Free and Peptide Tryptophan to N-Formylkynurenine.

The oxidation of proteins and, in particular, of tryptophan (Trp) residues leads to chemical modifications that can affect the structure and function. The oxidative damage to proteins in photochemical processes is relevant in the skin and eyes and is related to a series of pathologies triggered by exposure to electromagnetic radiation. In this work, we studied the photosensitized formation of N-formylkynurenine (NFKyn) from Trp in different reaction systems. We used two substrates: free Trp and a peptide of nine amino acid residues, with Trp being the only oxidizable residue. Two different photosensitizers were employed: Rose Bengal (RB) and pterin (Ptr). The former is a typical type II photosensitizer [acts by producing singlet oxygen (1O2)]. Ptr is the parent compound of oxidized or aromatic pterins, natural photosensitizers that accumulate in human skin under certain pathological conditions and act mainly through type I mechanisms (generation of radicals). Experimental data were collected in steady photolysis, and the irradiated solutions were analyzed by chromatography (HPLC). Results indicate that the reaction of Trp with 1O2 initiates the process leading to NFKyn, but different competitive pathways take place depending on the photosensitizer and the substrate. In Ptr-photosensitization, a type I mechanism is involved in secondary reactions accelerating the formation of NFKyn when free Trp is the substrate.

Theory of Refraction, Ray–Wave Tilt, Hidden Momentum, and Apparent Topological Phases in Isotropy-Broken Materials Based on Electromagnetism of Moving Media

The mysterious nature of electromagnetic momentum in materials is considered one of the most significant challenges in physics, surpassing even Hilbert’s mathematical problems. In this paper, we demonstrate that the difference between the Minkowski and Abraham momenta, which consists of Roentgen and Shockley hidden momenta, is directly related to the phenomenon of refraction and the tilt of rays from the wavefront propagation direction. We show that individual electromagnetic waves with non-unit indices of refraction (n) appear as quasistatic high-k waves to an observer in the proper frames of the waves. When Lorentz transformed into the material rest frames, these high-k waves are Fresnel–Fizeau dragged from rest to their phase velocities, acquiring longitudinal hidden momentum and related refractive properties. On a material level, all electromagnetic waves belong to Fresnel wave surfaces, which are topologically classified according to hyperbolic phases by Durach and determined by the electromagnetic material parameters. For moving observers, material parameters appear modified, leading to alterations in Fresnel wave surfaces and even the topological classes of the materials may appear differently in moving frames. We discuss the phenomenon of electromagnetic momentum tilt, defined as the non-zero angle between Abraham and Minkowski momenta or, equivalently, between the rays and the wavefront propagation direction. This momentum tilt is only possible in isotropy-broken media, where the E and H fields can be longitudinally polarized in the presence of electric and magnetic bound charge waves. The momentum tilt can be understood as a differential aberration of rays and waves when observed in the material rest frame.

Preparation of coal gangue foam concrete modified by nanomaterials: Physical properties, pore structure, and electromagnetic properties

In this study, coal gangue foam concrete (CGFC) was modified with nanomaterials to optimize its electromagnetic wave (EWV) absorption performance. Single-factor test was carried out to explore the effects of nano-silica (NS) and nano-calcium carbonate (NC) on the physical characteristics, hydration products and microstructure of CGFC. The results showed that the compressive strength of CGFC was the optimal when NS and NC were mixed with 1.5 wt% each, in which case the volume water absorption also decreased to the lowest value of 20.61 %. Additionally, compared with the control group, the incorporation of NS significantly accelerated the cement hydration rate. Moreover, the synergistic effect after the addition of NC promoted the cement hydration to generate more ettringite and C-S-H gel, and partly reduced the average pore size of CGFC, thereby improving the pore structure. Finally, the attenuation constant of the composite material can reach 187.92, and the reflection loss can reach −35.6 dB, demonstrating its excellent electromagnetic wave absorption ability.

Synergizing Electron and Ion Transports of Ti3C2TX MXene Fiber via Dot‐Sheet Heterostructure and Covalent Ti─C─Ti Cross‐Linking for Efficient Charge Storage and Thermal Management

AbstractTi3C2TX MXene with the merits of metallic conductivity, superhigh volumetric capacitance, and efficient absorption of the electromagnetic wave is considered a promising building block for fiber fabrication; nevertheless, the simultaneous improvement in electrochemical charge storage and electrical conductivity/thermal management is seldom achieved for MXene‐based fibers due to the contradictory in material design. Typically, aligned and densified packing of MXene fibers is highly desired for an enhanced intra‐/inter‐flake electron transport; however, the narrowed inter‐layer spacing restricts the kinetics of ion diffusion (the intercalation/de‐intercalation of electrolyte ions) and diminishes the accessible active sites for charge storage. Herein, the electron and ion transports of Ti3C2TX MXene fiber are synergized via a unique dot‐sheet heterostructure covalently bonded by Ti─C─Ti which provides the optimal inter‐layer spacing for rapid ion diffusion and enhances the intra‐/inter‐flake cross‐linking for fast electron transport. As a result, the obtained fiber offers an improved conductivity of 2405 S cm−1, a desirable capacitance of 1597 F cm−3, an impressive energy density of 19.8 mWh cm−3 for the assembled supercapacitor, superior Joule heating performance, and a photo‐thermal temperature. These remarkable attributes enable their practical applications in energy‐supply scenarios, such as powering LEDs and wearable thermal management.

Multi-component attached carbon matrix composites with superior electromagnetic wave absorption performance and multifunctional applications

The preparation of highly absorbing and high-performance electromagnetic wave-absorbing materials remains a significant challenge. In this paper, carbon matrix composites modified with sodium inorganic salts (CMS) have been successfully prepared by using the solvent evaporation method in combination with the hydrothermal treatment and high temperature carbonization processes. The composition of the product can be manipulated by varying the material ratios, which in turn affects the interface and dielectric properties of the material. Sodium carbonate (Na2CO3) was produced as a transition phase between sodium silicate and carbon matrix due to high temperature. According to differential charge density a significant charge accumulation found between the interfacial of Na2CO3 and carbon layer is helpful to polarization. The synergistic effect of polarization and conduction loss due to the formation of multiple heterogeneous interfaces and carbon matrix results in excellent electromagnetic wave absorption performance. The minimum reflection loss (RLmin) is −55.49 dB when the thickness is 3.1 mm. Furthermore, CMS composites exhibit notable flame retardancy and thermal insulation properties, rendering them suitable for a diverse range of applications. These remarkable achievements provide new ideas for the design and development of efficient electromagnetic wave absorption materials.

Enhancement of Electromagnetic Wave Attenuation through Polarization Loss Induced by Hybridization of Rare‐Earth 4f and Mo‐4d Orbitals in Liquid Plasma

AbstractThe incorporation of large‐sized rare earth (RE) elements with high coordination characteristics into transition metal dichalcogenide (TMD) absorbers while preserving a high 1T phase content during post‐processing poses a significant challenge. To address this, a novel strategy involving the confinement of RE elements within the 1T‐MoS2 lattice via liquid plasma assistance, is proposed. This approach effectively mitigates the environmental impact on the 1T phase of MoS2, yielding a remarkable 1T phase content of 82.69% for Ce20‐D7 (20 wt.% Cerium trinitrate and 7 kV applied voltage). Combining experimental and theoretical investigations reveals that the multi‐orbital characteristics of RE elements facilitate hybridization between the RE‐4f and Mo‐4d orbitals on the MoS2 surface, leading to the occupation of weakly bound electrons in bonding orbitals with short‐distance motion, enhanced inter‐orbital electron‐electron interactions, and induced polarization loss. Notably, the results demonstrate that the Pr15‐D7 sample (15 wt.% praseodymium nitrate and 7 kV applied voltage) exhibits an effective absorption bandwidth (EAB) of 7.12 GHz at 2.6 mm, with a minimum reflection loss of ‐52.02 dB while the Ce20‐D7 sample achieves an EAB of 6.96 GHz at 2.7 mm. These findings provide valuable insights for the rational design and development of high‐performance TMD absorbers leveraging RE‐modified materials.

Long‐Infrared Broadband Polarization‐Sensitive Absorber with Metasurface Based on Ladder Network

AbstractPlasmonic resonant and metamaterial structures allow for manipulating the polarization properties of electromagnetic waves to achieve polarization beam splitting. Broadband polarization‐sensitive metamaterial absorbers based on surface plasmon polaritons have the advantages of high‐energy utilization and excellent stability, which may replace traditional polarizing devices. Here, an absorber based on a ladder network construction is designed theoretically and investigated experimentally. The absorber can possess almost 92% average absorptivity for TM polarization light in 8–12 µm range (experimental result: 83% from 7 to 11 µm). It is especially sensitive to the polarization angle of incident light, and with the increase of polarization angle, the broadband absorption response can present analogously monotonous reduction. The theoretical and experimental results for TE polarization light are 12% and 25%, respectively. The broadband absorption response performs angle insensitive property under oblique incidence. The proposed metamaterial absorber opens a path to realize broadband polarization‐sensitive absorption based on simple nanostructure. It will possess great potential applications in high‐performance polarimetric photodetectors and imaging fields.

Safety evaluation of electromagnetic exposure for compact wireless charging stations of electric vehicles

ABSTRACT The spatial electromagnetic field of electric vehicle (EV) wireless charging stations may experience a superposition effect, which will increase the electromagnetic radiation. To assess the safety of electromagnetic exposure from wireless charging stations, this study employs a finite element simulation software to construct an electromagnetic environment model for a compact wireless charging station. The model is utilized to compute the superposition effect of spatial electromagnetic fields resulting from the simultaneous charging of multiple wireless chargers. Furthermore, the model assesses the levels of electromagnetic exposure on human models at eight observation points situated within the charging station. Results indicate that the volume average values of spatial magnetic induction strength ( B ) and electric field strength ( E ) are higher when multiple EVs are charged simultaneously than when a single EV is charged, and the electromagnetic radiation received by a human standing between two vehicles is greater than that near one vehicle. At the 22 kW charging power level, the maximum values of B , E and current density at the eight observation points of the charging station are all below the International Commission on Non-Ionizing Radiation Protection limit, demonstrating that the human body is safe in compact wireless charging stations at this power level.

A real-time working memory evaluation system for macaques in microwave fields.

With the development and widespread application of electromagnetic technology, the health hazards of electromagnetic radiation have attracted much attention and concern. The effect of electromagnetic radiation on the nervous system, especially on learning, memory, and cognitive functions, is an important research topic in the field of electromagnetic biological effects. Most previous studies were conducted with rodents, which are relatively mature. As research has progressed, studies using non-human primates as experimental subjects have been carried out. Compared to rodents, non-human primates such as macaques not only have brain structures more similar to those of humans but also exhibit learning and memory processes that are similar. In this paper, we present a behavioral test system for the real-time evaluation of the working memory (WM) of macaques in a microwave environment. The system consists of two parts: hardware and software. The hardware consists of four modules: the operation terminal, the control terminal, the optical signal transmission, and detection module and the reward feedback module. The software program can implement the feeding learning task, the button-pressing learning task, and the delayed match-to-sample task. The device is useful for the real-time evaluation of the WM of macaques in microwave environments, showing good electromagnetic compatibility, a simple and reliable structure, and easy operation.

Synthesis of Mo2C/C nanoclusters attached on rGO nanosheets for high-Efficiency electromagnetic wave absorption

It is an effective strategy that constructing composites with a multi-dimensional structure synergistically enhance their electromagnetic (EM) wave absorbing performance. Herein, a high-efficiency EM wave absorber of Mo2C/C nanoclusters uniformly encapsulated in rGO nanosheets (Mo2C/C-rGO) was prepared by a combination of the directing freeze-dry and subsequently carbothermal reaction method. Mo2C/C was in-situ induced from spherical phosphomolybdic acid/polypyrrole (PMo12/PPy) to result in a unique cluster-like microstructure. Abundant heterogeneous interfaces endowed the Mo2C/C-rGO composites with excellent EM wave absorption performance at a low filling ratio of 5 wt%. The minimum reflection loss (RL) value was −49.3 dB at 1.38 mm and the maximum effective absorption bandwidth (EAB, RL<-10 dB) was 5.12 GHz at 1.60 mm. The excellent performance was owing to the lamellar structure and abundant heterogeneous interfaces in Mo2C/C-rGO, lengthening the transmission path of the incident wave, as well as resulting in high conduction loss and interfacial polarization loss. This universal strategy would be extended to other absorbers with multi-interface structures for lightweight and broadband EM wave absorption.

Thin thickness electromagnetic wave absorbent: Fe3O4 decorated carbon nanofibers composite with designable 3D hierarchical architecture

Designable 3D hierarchical architecture with multi-component heterostructure has been built to form a connected network by fully utilizing the advantages of one-dimensional carbon nanofibers. Fe3O4 decorated carbon nanofibers, which exhibited core-shell microstructures, were successfully prepared by solvothermal and electrospinning technology. Their electromagnetic wave absorption (EWA) performances were explored. The morphology which determined the electromagnetic (EM) parameters can be controlled by adjusting the mass ratio of the raw material. The Fe3O4 decorated carbon nanofibers composite showed an excellent absorbing capability. At a thickness of 2.5 mm, the minimum reflection loss (RLmin) value was −28.28 dB. In particular, the widest effective absorption bandwidth (EAB) can reach up to 2.96 GHz at 1.5 mm. It was more surprising that the effective absorption (RL ≤ −10 dB) occurred when the thickness was only 1.0 mm. The absorption mechanism study revealed that the connected structure facilitated the formation of conductive networks, leading to conductive loss, multiple reflection and scatterings, and interfacial polarization loss. The defects that created during carbonization process enhanced the dipole polarization. The generated magnetic loss which mainly consisted of natural resonance and exchanged resonance loss enhanced the attenuation of EW. Moreover, good impedance matching resulting from the synergistic effect of composition and unique porous network also played an important role. The little filler loading and the thin thickness make the composite have a high EWA performance, which is promising for EWA applications.

Automatic Detection of Quasi-Periodic Emissions from Satellite Observations by Using DETR Method

The ionospheric quasi-periodic wave is a type of typical and common electromagnetic wave phenomenon occurring in extremely low-frequency (ELF) and very low-frequency ranges (VLF). These emissions propagate in a distinct whistler-wave mode, with varying periodic modulations of the wave intensity over time scales from several seconds to a few minutes. We developed an automatic detection model for the QP waves in the ELF band recorded by the China Seismo-Electromagnetic Satellite. Based on the 827 QP wave events, which were collected through visual screening from the electromagnetic field observations, an automatic detection model based on the Transformer architecture was built. This model, comprising 34.27 million parameters, was trained and evaluated. It achieved mean average precision of 92.3% on the validation dataset, operating at a frame rate of 39.3 frames per second. Notably, after incorporating the proton cyclotron frequency constraint, the model displayed promising performance. Its lightweight design facilitates easy deployment on satellite equipment, significantly enhancing the feasibility of on-board detection.

Artificial Intelligence Applied to Microwave Heating Systems: Prediction of Temperature Profile through Convolutional Neural Networks

Microwave heating, which is caused by the interaction of electromagnetic radiation and materials, has become an important component in industrial operations across numerous industries. Despite their importance, conventional numerical simulations of microwave heating are computationally intensive. Concurrently, advances in artificial intelligence (AI), particularly machine learning algorithms, have transformed data processing by increasing accuracy while decreasing computational time. This study tackles the difficulty of efficient and accurate modelling in microwave heating by combining convolutional neural networks (CNNs) with traditional simulation techniques. The major goal of this research is to use CNNs to forecast temperature profiles in a variety of industrial materials, including susceptors, semi-transparent, and microwave-transparent materials, under varying power settings and heating periods. This unique strategy greatly reduces prediction times, with up to 60-fold speed increases over standard methods. Our research is based on examining the electromagnetic and thermal responses of these materials under microwave heating. This study’s findings emphasise the need for extensive datasets and show the transformational potential of CNNs in optimising material processing. It uses artificial intelligence to pave the way for more effective and exact simulations, supporting breakthroughs in industrial microwave heating applications.

Electrical and dielectric properties of PVA-doped NiGdxFe2-xO4 nanoferrite particles

NiGdxFe2-xO4 nanoferrites combined with polyvinyl alcohol (PVA) and having a distinct spinel phase composition (x = 0.01, 0.03, 0.05, 0.07, and 0.09) were effectively created. Several characterization approaches were used to study the structural, dielectric, and magnetic properties of the PVA-blended nanoferrites. The acquired X-ray diffraction pattern showed the spinel cubic structure. Crystallite sizes of 50, 44, 40, 35, and 31 nm were found in PVA-blended nanoparticles for x = 0.01, 0.03, 0.05, 0.07, and 0.09, respectively. When compared to the PVA-unblended nanoferrites, the PVA-blended nanoferrites showed insulating properties with an enlarged energy bandgap. Real and complex dielectric constants, as well as the measured dielectric loss, were all in the microwave range (frequency ∼ 1.88–5.93 GHz). At higher frequencies, the dielectric constant became constant after declining with frequency. From the PVA-blended nanoferrites impedance study, pseudocapacitance (x = 0.01, 0.03, and 0.05) and resistive behavior (x = 0.07 and 0.09) were investigated. The magnetization hysteresis plot of PVA-blended NiGdxFe2-xO4 nanoferrites revealed a mild ferromagnetic character. The PVA doping of the produced nanoferrites increased their saturation magnetization and had a considerable microwave absorption capacity. For the broadest range of electromagnetic radiation absorption, ferrite might be the perfect material. The addition of rare-earth ions to these basic ferrites results in a considerable modification of the ferrites’ electromagnetic characteristics.