Dissipation Of Electromagnetic Energy Research Articles

Enhanced dielectric properties and electromagnetic interference shielding effectiveness of 3D hierarchical nanohybrid of Au-Ag@MoS2-rGO

Addressing the growing need for electromagnetic interference (EMI) shielding in GHz devices, this study presents a novel bimetallic Au-Ag@MoS2-rGO nanohybrid developed via hydrothermal and chemical processes. This work marks the first exploration of their dielectric properties and EMI shielding effectiveness. The composite, featuring uniformly dispersed Au-Ag alloy nanoparticles on MoS2-rGO nanosheets, significantly outperforms MoS2 and MoS2-rGO in EMI shielding, achieving over 38.1 dB in the X-band frequency range and blocking nearly 99.99% of electromagnetic power. This improvement is credited to the enhanced interfacial interactions, increased microwave absorption sites, and the formation of three-dimensional conductive bridges, boosting electrical conductivity and charge mobility. This efficient electromagnetic energy dissipation through a synergistic blend of conduction loss, polarization, and internal reflections suggests the potential for these advanced conductive metal-based materials in microwave absorbers and shielding applications.

Multilevel Heterogeneous Interfaces Enhanced Polarization Loss of 3D-Printed Graphene/NiCoO2/Selenides Aerogels for Boosting Electromagnetic Energy Dissipation.

Heterointerface engineering is an attractive approach to modulating electromagnetic (EM) parameters and EM wave absorption performance. However, the weak interfacial interactions and poor impedance matching would lead to unsatisfactory EM absorption performance due to the limitation of the construction materials and design strategies. Herein, multilevel heterointerface engineering is proposed by in situ growing nanosheet-like NiCoO2 and selenides with abundant interface structures on 3D-printed graphene aerogel (GA) skeletons, which strengthens the interfacial effect and improves the dielectric polarization loss. Benefiting from the features of substantially enhanced polarization loss and optimized impedance matching, the graphene/S-NiCoO2/selenides (G/S-NCO/Se) have achieved brilliant EM wave absorption performance with a strong reflection loss (RL) value of -60.7 dB and a broad effective absorption bandwidth (EAB) of 8 GHz, which is about six times greater than that of the graphene aerogel (-9.8 dB). Moreover, it is further confirmed by charge density differences and off-axis electron holography that a large amount of polarized charge accumulates at the interface, leading to significant polarization relaxation behaviors. This work provides a deep understanding of the effect of a multilevel heterogeneous interface on dielectric polarization loss, which injects a fresh and infinite vitality for designing high-efficiency EM wave absorbers.

Crystal structure and peculiarities of microwave parameters of Mg1-xZnxFe2O4 nanospinel ferrites

Employing an advanced citrate precursor methodology, we successfully synthesized nanoscale spinel ferrites, denoted as Mg1-xZnxFe2O4 (where x ranges between 0.0 and 1.0) or MZFO. Comprehensive analysis, utilizing state-of-the-art X-ray diffraction (XRD) techniques, demonstrated the defining attributes of the crystal structure. All examined specimens consistently exhibited a singular phase, adopting a cubic crystalline architecture. XRD pattern analysis allowed us to deduce the average particle dimensions of these ferrite specimens, which span between 17.2 nm and 31.5 nm. This observed size distribution corroborates well with transmission electron microscopy (TEM) imagery estimations. Delving into the Fourier-transform infrared (FTIR) spectra, two distinctive absorption bands of ferrites emerged: the first between 540 and 570 cm−1 and the subsequent between 339 and 435 cm−1. To glean insight into the electromagnetic attributes of MZFO, we meticulously assessed the experimentally ascertained S-parameters. This scrutiny spanned a frequency spectrum of 8–18 GHz. It was inferred that electromagnetic wave energy dissipation arises chiefly from a combination of electrical and magnetic phenomena. The underlying mechanisms of electrical dissipation can be attributed to polarization processes. Concurrently, the magnetic energy losses predominantly stem from magnetization reversal dynamics. Notably, a substantial attenuation observed in the reflected wave energy, ranging between −10 and −18.5 dB, augments the potential for this material's integration into practical applications.

Broadband electromagnetic wave absorption performance of CuS-biomass carbon composites derived from moss

The absorption performance of broadband electromagnetic waves is of utmost importance in safeguarding diverse electronic equipment against electromagnetic wave pollution, necessitating materials with low density, thin thickness, and cost-effectiveness to be employed. This study presents the successful synthesis of biomass-derived carbon (BC) composites via the hydrothermal method, utilizing moss coated with flower-like CuS. The CuS was uniformly dispersed on BC matrix, contribute to dipole polarization relaxation. The formation of heterogeneous interfaces between CuS and the BC phase resulted in significant polarization loss. Additionally, the wrinkled BC and flower like CuS constructed by nanosheets boosted scattering of electromagnetic wave due to its large specific surface area, which can provide additional channels for charge transfer and avail dissipation of electromagnetic wave energy. With an efficient absorption bandwidth (EAB) that encompasses the whole X band, the electromagnetic waves absorption (EMA) performance of CuS/BC composites was able to reach a minimum reflection loss of − 28.8 dB.

Investigation on vibration mitigation methodology with synergistic friction and electromagnetic damping energy dissipation

Investigation on vibration mitigation methodology with synergistic friction and electromagnetic damping energy dissipation

Microwave absorption performance of magnetic-dielectric Fe3O4@C@PPy composites with a core-double-shell structure prepared by a low-temperature self-propagation method

Microwave absorbers have been developed to counter electromagnetic pollution, and enhancing their performance remains an ongoing concern. In this paper, carbon-coated Fe3O4 and polypyrrole (PPy) were combined to construct composites with a core-double-shell structure, and the influences of multiple synergistic effects from ternary components, carbon defects, and microstructure on the electromagnetic properties of Fe3O4@C@PPy composites were investigated. The Fe3O4@C@PPy composites were successfully prepared by the low-temperature self-propagation method and in-situ oxidation polymerization process, achieving a −53.67 dB reflection loss at 12.24 GHz when the sample thickness was 2.13 mm, and the effective absorbing (RL < 10 dB) band covered 4.16 GHz (13.84–18 GHz) with a corresponding thickness of only 1.63 mm. The core-double-shell structure perfectly integrated various advantages of each component as well as provided multiple reflections and scatterings. Meanwhile, the polarization loss was notably enhanced by heterogeneous interfaces, and the dielectric-magnetic loss mechanism cooperatively accelerated the dissipation of electromagnetic wave energy.

Synthesis of NiCo2O4/CF composites with heterogeneous interfaces as excellent microwave absorbers

The absorbers with strong absorption capacity, wide effective absorption bandwidth (EAB), low filling, lightweight and thin thickness are the future development direction of electromagnetic wave (EMW) absorption field. NiCo2O4/CF composites were synthesized by simple hydrothermal method and calcination method in this study. X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and vector network analyzer (VNA) were used to study the crystal structure, microstructure, surface chemical states and microwave absorption properties of the composites, respectively. Carbon fiber (CF) was used as nucleation carrier, and NiCo2O4 formed a dense conductive network on its surface in the shape of nanoneedles. In addition, there are abundant oxygen vacancies and heterogeneous interfaces on the surface of composite materials, which can cause dipole polarization and interface polarization and lead to more dissipation of electromagnetic wave energy. The minimum reflection loss (RLmin) of the NiCo2O4/CF composite is − 59.75 dB at the thickness of 2.01 mm. The maximum effective absorption bandwidth (RL < −10 dB) of the composite is 4.12 GHz (8.84–12.96 GHz) at the thickness of 2.18 mm. In the thickness range of 1.2–5 mm, the effective absorption frequency range of the composite material accounted for 80.78% of the measurement range (3.46–18 GHz), which covered the whole C-band, X-band and Ku-band, as well as a portion of the S-band. NiCo2O4/CF composites have the characteristics of strong absorption and wide absorption bandwidth due to the synergistic effect of dielectric loss and magnetic loss, good impedance matching characteristics and more Debye relaxation processes, which provide new inspiration for the structure and component design of lightweight microwave absorbing materials (MAMs).

3D skeletal porous nanocage of ternary metallic oxide with excellent electromagnetic wave absorption

With the development of radio technologies, great efforts have been made to manufacture high-performance electromagnetic wave (EMW) absorbers for electronic information security, anti-reconnaissance stealth and human health protection. Reaching both excellent impedance matching and electromagnetic (EM) energy dissipation at the same time is still a challenge for EMW absorption materials. In this study, a 3D skeletal porous nanocage structure made from Co-Fe-Ni ternary metal oxide (CFN-TMO) was designed to simultaneously improve the impedance matching and guarantee sufficient EM energy dissipation of the EMW absorber. The integrity of the 3D skeletal nanocage structure and pore size on the cage wall can be tailored by the calcination temperature to optimize its EMW absorption capability. With a suitable pore size and complete skeleton structure, the best performance of the nanocage reaches a high reflection loss (RL) of −67.2 dB and an ultra-wide effective absorption bandwidth (EAB) of 8.2 GHz. The outstanding EMW absorption performance is mainly attributed to the nanocage structure, which can optimize the impedance matching and trigger multiple reflections of the EMWs. The skeleton constructed with the Co-Fe-Ni ternary metal oxide can improve the EMW dissipation by introducing a large number of interfaces, lattice defects and oxygen vacancies. This work reveals a nanostructure design route for optimizing the impedance matching, which can greatly increase the EMW absorption and provide important guidelines for the design and fabrication of lightweight and high-performance EMW absorption nanomaterials.

Rational design of heterointerface between MoO2 and N-doped carbon with tunable electromagnetic interference shielding capacity

Exploring highly efficient electromagnetic interference (EMI) shielding filler is urgently desired for next-generation wireless communication and integrated electronics. In this regard, a series of heterogeneous MoO2/N-doped carbon (MoO2/NC) nanorods with tunable conductivity have been successfully synthesized by regulating the pyrolysis temperature within 600, 700 and 800 °C. Profiting from the rational design of heterointerface and low-dimensional structure, the MoO2/NC powder achieves stronger EMI shielding capacity with the incremental temperature. It is found that the MoO2/NC-800 nanorods exhibit the optimal average EMI shielding effectiveness (SE) of 57.2 dB at a thickness of ∼0.3 mm in the X band. Meanwhile, the corresponding shielding mechanisms of MoO2/NC nanorods are also elaborately explained. More interestingly, the increase of sintering temperature makes an obvious effect on absorption loss but has little influence on reflection loss, demonstrating that adjusting the pyrolysis temperature is an effective strategy to strengthen the electromagnetic energy dissipation.

Biopolymer‐Based Aerogels for Electromagnetic Wave Shielding and Absorbing

Comprehensive SummaryThe rapid development of communication technology and electronic industry has brought unprecedented serious electromagnetic interference (EMI) and electromagnetic wave (EMW) pollution. Although EMI shields and EMW absorbers based on metal or magnetic materials were used to solve these problems, they have long been criticized for their high price, high density and easy corrosion. In order to achieve low density and efficient dissipation of electromagnetic energy, aerogels stand out among manifold materials. However, constructing aerogels with good EMI shielding or EMW absorption performance and acceptable mechanical properties is not an easy task. Burgeoning biopolymers, such as cellulose, lignin, chitin/chitosan and alginate, breathe new life into aerogels for high‐efficiency EMW shielding and absorbing. Here, we reviewed the contributions of biopolymers in the fields of aerogels for EMW shielding and absorbing. At the same time, some challenges and outlook were also pointed out, aiming to promote the advance of aerogel‐based EMI shields and EMW absorbers as well as the rational utilization of biopolymers.

Magnetic‐Dielectric Complementary Fe‐Co‐Ni Alloy/Carbon Composites for High‐Attenuation C‐Band Microwave Absorption via Carbothermal Reduction of Solid‐Solution Precursor

AbstractFerromagnetic alloys/carbon composites with excellent electrical and magnetic properties are highly desirable as electromagnetic wave absorption materials, but achieving high‐attenuation performance in C‐band (4–8 GHz) remains a challenge. Herein, a direct carbothermal reduction of organic gluconate solid‐solution precursor method is developed to synthesize ferromagnetic Fe‐Co‐Ni alloy/carbon composites, which realize high‐attenuation electromagnetic wave absorption in C‐band. By virtue of Fe, Co, and Ni elements homogeneously dispersing at the molecular level in the solid‐solution precursor with the regulated mole ratio, serial FeCo2Ni/C, Co7Fe3/C, FeNi3/C, and Co3Ni/C composites can be deliberately prepared. First‐principles calculations and off‐axis electron holograms can clearly unravel that these Fe‐Co‐Ni alloys could perform as excellent dielectric‐magnetic complementary loss units to trigger synergistic electronic dipole polarization oscillation, magnetic moment resonance, and magnetic coupling interaction. Meanwhile, the rich alloy–carbon interfaces and conductive carbon skeleton can facilitate delightful interfacial polarization and conductive loss. Combining these positive electromagnetic energy dissipation characteristics, FeCo2Ni/C with strengthened dipole polarization oscillation and outstanding impedance matching realizes an extremely high‐attenuation absorption performance with a minimum reflection loss of −82.2 dB at 5.21 GHz. This work provides a feasible and flexible insight into producing magnetic‐dielectric complementary Fe‐Co‐Ni alloys/carbon composites with various alloy compositions as excellent electromagnetic wave absorbers.

Stereolithographically 3D Printed SiC Metastructure for Ultrabroadband and High Temperature Microwave Absorption

AbstractBroadband microwave absorption is essential on the realms of electromagnetic compatibility and protection in civil application scenarios. However, coordination of material and structure is difficult without proper iterative design between material and structure resulting in insurmountable drawbacks of traditional microwave absorption medium operating under high temperature erosion. Herein, SiC metastructure is manufactured in bulk by stereolithographic 3D printing. The dielectric loss tangent of SiC sintered body is over 0.5 and up to 1.5 at most showing good electromagnetic energy dissipation properties. The optimized SiC metastructure with complicated suspended features achieves −10 dB broadband microwave absorption from 6.96 to 40 GHz at room temperature (RT) across total frequency range of 33.04 GHz. The proposed SiC metastructure is able to endure in situ 1000 °C and ex situ 1600 °C erosion in air atmosphere maintaining −10 dB effective bandwidth in 4.54–40 and 10.89–39.67 GHz, respectively. Broadband microwave absorption under oblique incidence from 0° to 60° is also achieved in a wide temperature range from RT to 1600 °C. The densification of SiC results in a high mechanical strength of 217.36 MPa for structural load bearing applications. The intrinsic electromagnetic variation of SiC under different temperature is relaxed and adapted to the metastructure design. The functions of broadband microwave absorption and high temperature protection are integrated into one metastructure.

Fine grid model for the dielectric characteristics of ground‐penetrating radar in mixed media

ABSTRACTThe Fisher–Yates random shuffling algorithm combined with the finite‐difference time‐domain method is proposed to construct a fine grid model for the forward simulation of ground‐penetrating radar in mixed media. First, the finite‐difference time‐domain method was used to divide the coarse grid model into several fine grid models by conforming to the boundary conditions of different media, and the corresponding dielectric parameters were assigned to Yee cells in each fine grid model. Then, the Fisher–Yates random shuffling algorithm was used to randomly scramble all Yee cells with equal probability, and the array of scrambled Yee cells was recombined into a coarse grid model. Finally, the geoelectric model of mixed media was generated with the finite‐difference time‐domain method, and a ground‐penetrating radar image excited by electromagnetic wave pulses was obtained. To explore the characteristic signals and dielectric properties of the ground‐penetrating radar electromagnetic response in mixed media, image entropy theory was used to describe the ground‐penetrating radar image, and waveform analysis and wavelet transform mode maximum methods were used to analyse the single‐channel ground‐penetrating radar signal of the mixed media. The results showed that the Fisher–Yates random shuffling–finite‐difference time‐domain method can be used to construct a valid and stable fine grid model for simulating ground‐penetrating radar in mixed media. The model effectively inhibits electromagnetic attenuation and energy dissipation, and the wavelet transform mode maximum method explains the relative dielectric permittivity distribution of the mixed media. The findings of this study can be used as a theoretical basis for correcting radar parameters and interpreting images when ground‐penetrating radar is applied to mixed media.

Ti3C2Tx-coated diatom frustules-derived porous SiO2 composites with high EMI shielding and mechanical properties

Effective electromagnetic interference (EMI) shielding materials have garnered substantial interest for their efficacy in attenuating electromagnetic wave energy, ensuring data confidentiality, ensuring the operational stability of fragile electronic systems. To begin, artificially cultured diatom frustules (DF)-derived porous silica (DFPS) skeletons were constructed as templates in this study. Porous ceramics hot-pressed at 800 °C displayed a high compressive strength with a high specific surface area due to their three-dimensional (3D) multilayered and porous structures. Then, mechanically robust Ti3C2Tx/DFPS composites with exceptional EMI shielding performance were fabricated by immersing porous DF-based ceramics into Ti3C2Tx solutions and annealing in an argon environment to increase the materials’ shielding efficiency (SE). The EMI SE of composites hot-pressed at 800 °C achieved the maximum EMI SE of 43.2 dB in the X-band and a compressive strength of 67.5 MPa, establishing a hitherto unreported balance of mechanical characteristics and shielding performance. Prolonged transmission paths, multiple dissipation, scattering and reflection of electromagnetic energy were achieved using a well-maintained hierarchical porous silica framework decorated with MXene, with adsorption caused by surface MXene serving as the primary shielding mechanism for the composites. Due to their superior overall performance, MXene/DFPS EMI shielding composites have a bright future in the aircraft sector as delicate electronic device components.

Shattered pellet injection experiments at JET in support of the ITER disruption mitigation system design

A series of experiments have been executed at JET to assess the efficacy of the newly installed shattered pellet injection (SPI) system in mitigating the effects of disruptions. Issues, important for the ITER disruption mitigation system, such as thermal load mitigation, avoidance of runaway electron (RE) formation, radiation asymmetries during thermal quench mitigation, electromagnetic load control and RE energy dissipation have been addressed over a large parameter range. The efficiency of the mitigation has been examined for the various SPI injection strategies. The paper summarises the results from these JET SPI experiments and discusses their implications for the ITER disruption mitigation scheme.

Preparation and characterization of ferrite/carbon aerogel composites for electromagnetic wave absorbing materials

Ferrite/carbon aerogel composites have been fabricated via vacuum impregnation and coprecipitation of iron ions. The resultant Fe3O4/carbon aerogels possess high specific surface area, electronic conductive interconnected network and uniformly dispersed magnetic nanoparticles, showing an excellent electromagnetic wave absorption performance, which can be tactfully regulated by the pyrolysis temperature and incorporated Fe3O4 content. The minimum reflection loss of −57 dB is achieved with a filler loading of 10 wt%, and the effective absorption bandwidth can cover 5.2 GHz with a thickness of 1.8 mm. Furthermore, the electromagnetic energy dissipation mechanism has been discussed to provide a new route for preparing electromagnetic wave absorption materials.

Weak Alfvénic turbulence in relativistic plasmas. Part 2. current sheets and dissipation

Alfvén waves as excited in black hole accretion disks and neutron star magnetospheres are the building blocks of turbulence in relativistic, magnetized plasmas. A large reservoir of magnetic energy is available in these systems, such that the plasma can be heated significantly even in the weak turbulence regime. We perform high-resolution three-dimensional simulations of counter-propagating Alfvén waves, showing that an $E_{B_{\perp }}(k_{\perp }) \propto k_{\perp }^{-2}$ energy spectrum develops as a result of the weak turbulence cascade in relativistic magnetohydrodynamics and its infinitely magnetized (force-free) limit. The plasma turbulence ubiquitously generates current sheets, which act as locations where magnetic energy dissipates. We show that current sheets form as a natural result of nonlinear interactions between counter-propagating Alfvén waves. These current sheets form owing to the compression of elongated eddies, driven by the shear induced by growing higher-order modes, and undergo a thinning process until they break-up into small-scale turbulent structures. We explore the formation of current sheets both in overlapping waves and in localized wave packet collisions. The relativistic interaction of localized Alfvén waves induces both Alfvén waves and fast waves, and efficiently mediates the conversion and dissipation of electromagnetic energy in astrophysical systems. Plasma energization through reconnection in current sheets emerging during the interaction of Alfvén waves can potentially explain X-ray emission in black hole accretion coronae and neutron star magnetospheres.

Three dimensional flower like ZnFe2O4 ferrite loaded graphene: Enhancing microwave absorption performance by constructing microcircuits

In the research of new type of absorbing materials, the influence of special three-dimensional (3D) microstructure and the composite effect of multi-component materials on the electromagnetic properties and absorbing properties of materials has attracted widespread attention. In this work, the 3D flower like ZnFe2O4 ferrite (3D-ZFO) was prepared by two solution chemical precipitation processes, and then a simple ultrasonic and heat treatment process was used to uniformly load the prepared 3D-ZFO on graphene nanosheets (GNs). A new wave absorber (3D-ZFO/GNs) composed of two-dimensional (2D) and 3D materials was obtained. Interestingly, the coprecipitation of Fe3+ and Zn2+ in alkaline solution transforms the 3D flower like ZnO template composed of flakes into ZnFe2O4 composed of lines. The combination with GNs can effectively enhance the conductance loss and dipole polarization, and create a new effective hetero interface. In addition, 3D-ZFO with high resistance and GNS with excellent conductivity form a micro circuit, which promotes the formation of micro current and is conducive to the dissipation of electromagnetic wave energy in the form of micro current. In the 2–18 GHz frequency band, 3D-ZFO/GNs with 5 wt% GNs can obtain an effective bandwidth of 5.56 GHz at a matching thickness of 1.5 mm. By controlling the thickness of the matching layer, the absorbing frequency band can be easily adjusted to meet the needs of multi-band absorbing. Considering the simple preparation process, the increase of the electromagnetic wave conduction path by the special microstructure and the synergistic effect of multiple loss mechanisms, we believe that the prepared 3D-ZFO/GNs is expected to be a candidate for high-efficiency microwave absorbers.

Tailoring electronic properties and polarization relaxation behavior of MoS2 monolayers for electromagnetic energy dissipation and wireless pressure micro-sensor

Electromagnetic radiation has become a severe problem due to the widespread utilization of wireless communications and smart electronic devices. Hence, the development of high-performance electromagnetic wave absorbers to overcome the electromagnetic pollution is of utmost significance. Herein, density functional theory (DFT) calculations are adopted to guide the design of high-performance electromagnetic wave absorbers based on layered MoS2. The results indicate that the electronic properties, the dipole moment and the electric polarization of vertically-aligned MoS2 monolayers on N-doped graphene are significantly tuned compared to horizontally-aligned MoS2 monolayers on N-doped graphene and MoS2 nanosheets, favoring the absorption of electromagnetic waves. Based on theoretical predictions, we have combined vertically-aligned MoS2 monolayers and N-doped graphene nanomesh by the spatial confinement effect of the nanomeshs. The experimental results demonstrate that the MoS2 monolayers on N-doped graphene exhibit excellent electromagnetic wave absorption performance with a minimal reflection loss of –72.83 dB and an effective absorption bandwidth of 4.81 GHz even at a matching thickness below 2.0 mm, remarkably outperforming MoS2 nanosheets. The excellent consistency between theoretical and experimental results highlights that the DFT calculations can be employed as a design tool for high-performance electromagnetic wave absorber. Based on the excellent electromagnetic absorption performance of the MoS2 monolayers, a highly sensitive wireless pressure micro-sensor is designed, which has potential apllication in internet of things.

Coherent plasmonic absorption in the femtosecond regime

Dissipation of electromagnetic energy through absorption is a fundamental process that underpins phenomena ranging from photovoltaics to photography, analytical spectroscopy, photosynthesis, and human vision. Absorption is also a dynamic process that depends on the duration of the optical illumination. Here we report on the resonant plasmonic absorption of a nanostructured metamaterial and the non-resonant absorption of an unstructured gold film at different optical pulse durations. By examining the absorption in travelling and standing waves, we observe a plasmonic relaxation time of 11 fs as the characteristic transition time. The metamaterial acts as a beam-splitter with low absorption for shorter pulses, while as a good absorber for longer pulses. The transient nature of the absorption puts a frequency limit of ~90 THz on the bandwidth of coherently-controlled, all-optical switching devices, which is still a thousand times faster than other leading switching technologies.