Perfect Conductor Research Articles

In-situ Construction of Petal-liked porous Co coating layers for electromagnetic wave absorption materials with rich interface-polarization

With the rapid advancements in 5G and communication technology, electromagnetic wave (EMW) absorption materials play a crucial role in reducing interference, enhancing the efficiency and stability of communication equipment, and minimizing maintenance requirements. However, the challenge remains in effectively utilizing cost-effective raw materials with simple synthesis conditions to achieve highly consistent product quality and superior EWM absorption performance. This study employs carbon nanofibers (CNFs) derived from polyacrylonitrile (PAN) as substrates and utilizes electrodeposition technology to create a composite material that exhibits both magnetic and dielectric properties. The results show that the petal-like porous Co composite CNFs (Co/CNFs) demonstrates excellent impedance matching and significant EMW absorption capabilities, which can be attributed to synergistic microstructural effects and multiple loss mechanisms. At a filling ratio of 20 wt% and a thickness of 1.8 mm, the Co/CNFs achieves a minimum reflection loss of −45 dB, extending the effective absorption bandwidth to 4.6 GHz. Performance assessment through power loss density (PLD) and radar cross-section (RCS) simulations evaluates the material’s capabilities, confirming the enhanced performance of Co/CNFs compared to the perfect electrical conductor (PEC). This efficient preparation method holds substantial potential for practical applications and serves as a comprehensive guide for achieving a balance between high performance, efficiency, and cost-advantages.

Cavity-modulated visualization of dual magnetic coupling behavior for multifunctional Co/DMAOP composites

The demand of microwave-absorbing materials for the marine environment requires the multifunctional characteristic, including microwave absorption, corrosion protection, and antimicrobial. However, achieving these properties without compromising on the microwave-absorbing performance remains a significant challenge. Here, we present a self-sacrificial template strategy to synthesize Co-metal–organic framework (MOF)-74 nanorods, achieving synergistic anticorrosion and antibacterial effects by the introduction of dimethyl octadecyl (3-trimethoxysilylpropyl) ammonium chloride (DMAOP). Our findings show that by adjusting the cavity shape, internal and exterior double-coupling behaviors may occur simultaneously, greatly increasing the synthetic composites’ capacity for magnetic loss. As a result, the Co/DMAOP-120 with 100.00 % cavity structure has an ideal reflection loss (RL) value of up to − 68.05 dB and an effective absorption bandwidth (EAB) of 4.88 GHz at a thickness of 3 mm. This material also shows significant corrosion resistance and a bacterial inhibition rate against Staphylococcus aureus (S. aureus) of 93.89 %. The maximum radar scattering cross section (RCS) of Co/DMAOP-120 under far-field conditions is significantly reduced compared to that of a perfect electrical conductor (PEC), further validating the highly efficient wave-absorbing capability of Co/DMAOP-120 in real-world environments. The new magnetic loss mechanism offers fresh recommendations for designing the microstructure of materials that waves in absorb several ways.

High-Frequency Modeling and Analysis of Single-Layer NiZn Ferrite Inductors for EMI Filtering in Power Electronics Applications

In the high-frequency (HF) region, specifically within the 150 kHz to 30 MHz range for conducting electromagnetic interference (EMI) modeling, NiZn inductors exhibit enhanced efficiency due to their low core losses and stable permeability. Consequently, the accurate modeling of NiZn ferrite toroidal inductors is essential, given their widespread applications in the HF domain, with the aim of addressing existing knowledge gaps. Previous inductor models often relied on the perfect electric conductor (PEC) assumption, which simplifies the analysis but does not fully represent the electromagnetic behavior of the cores to which the PEC assumption cannot be applied. This study investigates the actual electromagnetic behavior of NiZn cores, treating them as dielectrics, which diverges from the traditional PEC-based models. Furthermore, this research fully considers the actual geometry of the inductors, proposing a comprehensive and precise analytical model for NiZn ferrite toroidal inductors. The impact of various winding methods on core capacitance is also explored. The paper provides a detailed explanation of the physical significance underlying the proposed model. A comparative analysis of both modeling methods is presented, and the efficacy of the suggested approach is validated through simulations and experimental results in several distinct scenarios.

Flexible CoNiZn@Ti3CNTx MXene@carbon fabrics with hierarchical structure for efficient electromagnetic wave absorption

The widespread application of 5G technology has significantly exacerbated concerns regarding electromagnetic radiation. However, the rigidity and lack of flexibility of traditional electromagnetic wave (EMW) absorption materials make them ill-suited for protecting humans and certain specialized, complex shapes of equipment. Therefore, there is an increasing urgency to develop flexible EMW absorbing fabrics to effectively mitigate electromagnetic pollution. In this study, hierarchical structure CoNiZn@Ti3CNTx MXene@carbon fabrics (CoNiZn@Ti3CNTx@CF) were constructed from nano-flower structure CoNiZn-MOF, Ti3CNTx MXene and fabrics by self-assembly, in-situ growth and pyrolysis. The carbon fabric acts as a skeleton to form a 3D interconnected conductive network, in which loaded nano-flower structure CoNiZn@Ti3CNTx MXene (CoNiZn@Ti3CNTx@C) composites exists excellent dielectric loss and magnetic loss, so that EMW enters the fabric and optimizes the impedance matching, increasing the multiple reflection and scattering of EMW, thereby effectively attenuating EMW. The minimum reflection loss (RLmin) of CoNiZn@Ti3CNTx@CF reaches -44.51 dB at 14.88 GHz with filling ratio of 15 % and thickness of 1.50 mm and the effective absorption bandwidth (EAB) of CoNiZn@Ti3CNTx@CF reaches 4.32 GHz (13.04–17.36 GHz) at 1.55 mm. The EAB of CoNiZn@Ti3CNTx@CF is expanded to 14.56 GHz (3.44–18.00 GHz) through thickness adjustment (1–5.50 mm), covering most of the S, C, X, and Ku bands. The radar cross-section (RCS) value of CoNiZn@Ti3CNTx@CF is 17.3 dB m2 lower than the perfect electrical conductor (PEC), which effectively reduces the probability of the target being detected by the radar detector. This work provides ideas for design and development of flexible EMW absorbing materials.

Discovery of Electromagnetic Surface Waves at the Interface between Perfect Electric Conductor and Perfect Magnetic Conductor Parallel-Plate Waveguides.

We propose new electromagnetic surface waves at the interface formed by connecting perfect electric conductor (PEC) and perfect magnetic conductor (PMC) parallel plate waveguides containing materials with positive permittivities and permeabilities. This challenges the conventional understanding that surface waves require materials with negative permittivity or permeability. Theoretical mode analysis and numerical simulations have confirmed the existence of surface waves at the PEC-PMC interface. Additionally, a simulated prism coupling experiment validated the excitation of the surface watpdel 1ve at the PEC-PMC interface. The resonant response of the localized surface waves on the enclosed PEC-PMC surface of a cylinder also closely resembles that of a Drude cylinder. Our finding broadens the understanding of the conditions for generating electromagnetic surface waves and deepens our comprehension of electromagnetic phenomena.

The Effect of the Wall Thickness of the Material Loaded Cavity On the RCS Reduction

In this paper, the effect of a parallel plate waveguide's wall thickness on radar cross-section reduction (RCS) is rigorously analyzed for H-polarization by using the Wiener-Hopf Technique, when the waveguide region is loaded with dielectric material and terminated with a perfect electric conductor (PEC) plate. Transfer matrices are incorporated into the analysis to account for the effect of different material layers through continuity relations. The Fourier transforms of the diffracted field and the boundary conditions yield a modified scalar Wiener-Hopf equation of the second kind (MWHE-2). The classical procedure to solve the MWHE-2 is applied and the approximate expression of the diffracted far field is obtained. Numerical results are given by comparing with the results available in the literature for the case of the wall thickness of the cavity not being considered.

A Hybrid Mechanism Metasurface Based on Absorption and Phase Cancellation for Ultra‐Wideband RCS Reduction

AbstractThis paper proposes a hybrid mechanism based on phase cancellation and absorption to design a metasurface with ultra‐wideband 10 dB radar cross‐section (RCS) reduction from 6 to 64.7 GHz (171%). At high frequencies of 15–64.7 GHz, 10 dB RCS reduction is achieved by a phase cancellation mechanism, which is realized by arranging a perfect electric conductor (PEC) to form an arrayed structure with varying heights. At low frequencies of 6–15 GHz, 10 dB RCS reduction is achieved by the absorption mechanism, which is realized by designing a rotationally symmetric dual‐pattern absorber. The coupled mode theory (CMT) is used to explain the absorption mechanism. Additionally, it is found that a 180° phase difference is obtained by two different patterns to enhance RCS reduction in the high‐frequency band of 28–35 GHz. Finally, the phase cancellation and absorption mechanisms are combined to achieve an ultra‐wideband 10 dB RCS reduction from 6 to 64.7 GHz, which is realized by integrating the absorber into the arrayed structure to form the ultra‐wideband RCS reduction metasurface. The designed metasurface has a compact size (subwavelength), and a thin profile with 0.105λL.

Perfect conductor and mu-metal enhancement of effects in electromagnetic fields over single emitters near topological insulators

Perfect conductor and mu-metal enhancement of effects in electromagnetic fields over single emitters near topological insulators

A contour integral-based method for nonlinear eigenvalue problems for semi-infinite photonic crystals

In this study, we introduce an efficient method for determining isolated singular points of two-dimensional semi-infinite and bi-infinite photonic crystals, equipped with perfect electric conductor and quasi-periodic mixed boundary conditions. This specific problem can be modeled by a Helmholtz equation and is recast as a generalized eigenvalue problem involving an infinite-dimensional block quasi-Toeplitz matrix. Through an intelligent implementation of cyclic structure-preserving matrix transformations, the contour integral method is elegantly employed to calculate the isolated eigenvalue and to extract a component of the associated eigenvector. Moreover, a propagation formula for electromagnetic fields is derived. This formulation enables rapid computation of field distributions across the expansive semi-infinite and bi-infinite domains, thus highlighting the attributes of edge states. The preliminary MATLAB implementation is available at https://github.com/FAME-GPU/2D_Semi-infinite_PhC.

Enforcing interface field continuity to advance finite element approximations in heterogeneous materials

To investigate the discrete field continuity at the interface of inhomogeneous materials, this paper investigates the scattering of electromagnetic waves interacting with a perfect electrical conductor object coated with dielectric materials, employing the finite element method. In the derivation process of the variational formulation, the tangential continuity of electric fields eliminates any discrepancies occurring along the internal interfaces. However, while it is important to maintain tangential continuity of electric and magnetic fields at the interface between different dielectrics, this requirement is not met precisely within discrete space. As a result, approximations can exhibit inaccuracies and potentially fail to fully capture the underlying physical phenomena. To alleviate these issues, we propose an imposition of tangential continuity of the magnetic field within the minimizing functional, thereby ensuring adherence to interface conditions between two dielectric layers. This approach can be naturally applied to a variety of interface problems to enhance the approximation accuracy of interaction models in real-world environments.

SUB-6 5G NETWORKS: DESIGN OF BUTTON MUSHROOM MIMO ANTENNA AND IT’S INVESTIGATION

The unlicensed National Information Infrastructure radio band (n77, n78, and n46) is taken into consideration for this research work's "Multiple-input-multiple-output (MIMO)" antenna with dual band features. Gradually, the form design of simple single-patch MIMO antennas gives way to four-element MIMO antennas. Four microstrip antennas are integrated using button-like circular caps on the main patches. Reduced ground is also used in the construction of many band characteristics. Excellent isolation can be achieved by using Rectangular Metallic Strip (RMS). The suggested MIMO antenna has the advantage of covering two significant frequency bands. At 3.07 GHz and 6.31 GHz, the antenna system resonates with a total bandwidth of 2.43 GHz. The antenna design uses a FR4 substrate measuring 35 mm by 49 mm by 1.6 mm in thickness. For simulation purposes, Teflon and a specially made SMA connector with a perfect electrical conductor (PEC) are used to enhance impedance matching. An 8.2 mm feed line with an inset feed is also utilized. Research and investigation are conducted on radiation properties, including mean effective gain, envelope correction coefficient, reflection coefficient, and more. Both the reflection and isolation coefficients have values of less than -10 dB, with the former being less than -15 dB. It is a 16.30 dB increase overall. 5G applications will greatly benefit from having this smaller, four-element MIMO antenna.

SUB-6 5G NETWORKS: DESIGN OF BUTTON MUSHROOM MIMO ANTENNA AND IT’S INVESTIGATION

The unlicensed National Information Infrastructure radio band (n77, n78, and n46) is taken into consideration for this research work's "Multiple-input-multiple-output (MIMO)" antenna with dual band features. Gradually, the form design of simple single-patch MIMO antennas gives way to four-element MIMO antennas. Four microstrip antennas are integrated using button-like circular caps on the main patches. Reduced ground is also used in the construction of many band characteristics. Excellent isolation can be achieved by using Rectangular Metallic Strip (RMS). The suggested MIMO antenna has the advantage of covering two significant frequency bands. At 3.07 GHz and 6.31 GHz, the antenna system resonates with a total bandwidth of 2.43 GHz. The antenna design uses a FR4 substrate measuring 35 mm by 49 mm by 1.6 mm in thickness. For simulation purposes, Teflon and a specially made SMA connector with a perfect electrical conductor (PEC) are used to enhance impedance matching. An 8.2 mm feed line with an inset feed is also utilized. Research and investigation are conducted on radiation properties, including mean effective gain, envelope correction coefficient, reflection coefficient, and more. Both the reflection and isolation coefficients have values of less than -10 dB, with the former being less than -15 dB. It is a 16.30 dB increase overall. 5G applications will greatly benefit from having this smaller, four-element MIMO antenna.

The novel impedance matching device realized by the structure of air-gap ring based on the doping method at microwave frequency

The doping method enabled the epsilon-near-zero (ENZ) medium to adjust its permeability effectively. In this study, we theoretically analyze that the gap ring structure formed by the ENZ medium doped with perfect electrical conductor (PEC) can be equivalent to the controllable series reactance. Based on this concept, a universal matching network that can match any complex impedance load by adjusting the gap ring spacing is constructed. We used the above universal matching network to carry out theoretical and simulation calculations on the matching effect of a random-sized stepped waveguide and horn antenna, and the results show that the impedance-matching technology has a good matching effect for different loads. Finally, experimental verification is carried out. Compared with traditional impedance-matching networks, the proposed structure has the characteristics of simplicity, reliability, low loss, high carrying power, low preparation requirements, and good application prospects. This work is a good example of the practicality of ENZ media and also provides a very meaningful idea for the development of new electromagnetic matching devices.

Magnetic bimetallic nanoparticles confined growth for enhancement of electromagnetic loss in void@Fe@SiO2/Co/C particles

The dispersion of diverse magnetic metallic in a single particle plays an important role in microwave absorption; however, its contribution is not clear due to the challenge of controllable synthesis of magnetic bimetallic nanoparticles in one micro/nanostructure. Herein, a series of magnetic bimetallic nanoparticles separately confined growth in a hollow multi-shell microsphere with proper impedance matching characteristic were prepared, which can be used as theoretical models to elucidate magnetic coupling effect between diverse magnetic metallic nanoparticles in a single particle on electromagnetic attenuation. The coupling effect of magnetic Co and Fe nanoparticles dispersed in different shell effectively enhance the microwave absorption performance of void@Fe@SiO2/Co/C particles with minimum reflection loss (RLmin) of −62.3 dB (RL=-20 dB, 99 % absorption) at a thickness of 2.05 mm, provoking the maximum radar cross-section (RCS) reduction value of perfect electric conductor (PEC) 37.37 dBm2. Meanwhile, broad effective bandwidth (EBW, RL≤-10 dB, ≥90 % absorption) response of 7.04 GHz at a thickness of 2.44 mm was achieved. These findings can provide guidance for the designation of novel magnetic broadband microwave absorbing materials (MAMs).

Lightweight carbon fiber aerogel@hollow carbon/Co3O4 microsphere for broadband electromagnetic wave absorption in X and Ku bands

The increasing proliferation of modern communications, radar systems, and military equipment operating in the X and Ku bands (8–18 GHz) has exacerbated the issue of electromagnetic wave (EMW) pollution, highlighting the urgent need for lightweight, broadband EMW-absorbing materials. In this paper, the lightweight carbon fiber aerogel@hollow carbon/Co3O4 microsphere (CFA@H–C/Co3O4) were composed by ZIF-67 derived hollow carbon/Co3O4 microsphere and bamboo cellulose fiber derived carbon fiber aerogels and constructed by in-situ chemical deposition, dopamine treatment and pyrolysis. Carbon fiber aerogels form a lightweight three-dimensional (3D) interconnected conductive network, which expands the multiple reflection and absorption paths of EMW and increases the dielectric loss. The hollow carbon/Co3O4 microsphere inhibits the collapse of the structure by forming a polydopamine shell through the self-polymerization effect of dopamine on the surface of ZIF-67 during pyrolysis, showing dipole polarization loss, interface polarization loss and magnetic loss, which plays an important role in improving EMW polarization loss and optimizing impedance matching. The minimum reflection loss (RLmin) of CFA@H–C/Co3O4 reaches −43.5 dB at frequency of 12.88 GHz with thickness of 3.0 mm and the effective absorption bandwidth (EAB) of CFA@H–C/Co3O4 reaches 7.84 GHz (10.08–17.92 GHz) with thickness of 3.0 mm, covering most of X and Ku bands at a low filling ratio of 15 wt%. The radar cross-section (RCS) value of CFA@H–C/Co3O4 is 22.68 dB m2 lower than the perfect electrical conductor (PEC). This study provides valuable insights into materials that can improve the absorption bandwidth of electromagnetic waves in the X and KU bands.

Classical Casimir pressure in the presence of axion dark matter

We study the effects of an oscillating axion field on the pressure between two metallic plates. We consider the situation where a magnetic field parallel to the plates is present and show that the electric field induced by the coupling of the axion to photons leads to resonances. When the boundary plates are perfect conductors, the resonances are infinitely thin whilst they are broadened when the conductivity of the boundary plates is taken into account. The resonances take place at the tower of distances close to dn=(2n+1)πm, where m is the axion mass and have a finite width and height depending on the conductivity. The resulting resonant pressure on the plate depends on the induced polarization at the surface of the plates. We investigate the reach of future Casimir experiments in terms of the axion mass and the conductivity of the boundary plates. We find that for large enough conductivities, the axion-induced pressure could be larger than the quantum Casimir effect between the plates. Published by the American Physical Society 2024

Transmission anomalies in 2D photonic crystals from the checkerboard family: from broken to hidden symmetries and plasmon “spoofing”

In a field representation, the main symmetry of the electromagnetic response of complementary metal film structures is described by the Babinet principle, which is expected to be strictly obeyed by structures in vanishingly thin films of a perfect electric conductor. On the other hand, a softer version of this based on transmittance, the transmittance Babinet principle (TBP), is not so restrictive. The goal of this work is to study how severely this broken symmetry affects the optical response of such structures. We consider two geometrically distinct series of planar complementary structures from the checkerboard family: regular and bowtie. The self-complementary structure of these series is known to be very singular and breaks even the rigorous Babinet principle. Here, we study complete simulated transmittance spectral maps (T-Maps), which accumulate the whole spectral response of an entire series of structures in a single plot. The ab initio simulated T-Maps of these 2D photonic crystals were simulated for linearly polarized waves propagating perpendicular to these planar structures, made in a vanishingly thin film of a perfect electric conductor. While we confirm the expected long wavelength validity of the TBP, we show that in the frequency range where diffraction effects dominate, the standard derivation of the TBP no longer applies, and with the help of our T-Maps, we demonstrate a total collapse of the TBP in the structures considered. We show that this broken symmetry practically eliminates all but one transmission band on the hole side of the T-Maps and that the remaining strong band is a “spoof” plasmon, free of multiple frequency replicas, an important feature for optical filter applications. In addition, by symmetry arguments and simulations, we discovered that the T-Maps for bowtie and doubled-period regular structures are identical. We discuss how this hidden symmetry can benefit various applications by providing a convenient scaling, whereby simplified structures can deliver a tailored response.

A polarization conversion metasurface for broadband and high-efficiency bidirectional filtering

Here, we demonstrate a polarization conversion metasurface which is composed of a single layer square split-ring resonator and bi-layered slotted perfect electrical conductor (PEC) to realize broadband and high-efficiency bidirectional filtering. The numerical results indicate that y-polarized waves can be converted to x-polarized transmission waves in the frequency range of 6.6 GHz to 13.9 GHz, while prevent this polarized waves with frequency beyond this band, and purity x-polarized waves can be obtained as electromagnetic (EM) waves are incident along negative z-axis, meanwhile, x-polarized waves can be converted to y-polarized transmission waves and only y-polarized waves available when EM waves are incident along positive z-axis. This designed polarization conversion metasurface has the function of bidirectional filtering in a wideband frequency range. Furthermore, the broadband property can be maintained as the incident angle up to 30°. The Fabry–Pérot-like cavity model is established to clarify the interference and enhancement effect of polarization conversion, and the electrical field and surface current distributions are used to elucidate the physical mechanism of polarization conversion and filtering. The experimental results are coincident with the numerical simulations. This metasurface can be employed in controlling the filtering signal of the polarized devices and can be functional as a bandpass filter in communication systems.

Three-dimensional topological crystalline insulator without spin–orbit coupling in nonsymmorphic photonic metacrystal

Abstract By including certain point group symmetry in the classification of band topology, Fu proposed a class of three-dimensional topological crystalline insulators (TCIs) without spin–orbit coupling in 2011. In Fu’s model, surface states (if present) doubly degenerate at Γ ¯ and M ¯ when time-reversal and C 4 symmetries are preserved. The analogs of Fu’s model with surface states quadratically degenerate at M ¯ are widely studied, while surface states with quadratic degeneracy at Γ ¯ are rarely reported. In this study, we propose a three-dimensional TCI without spin–orbit coupling in a judiciously designed nonsymmorphic photonic metacrystal. The surface states of photonic TCIs exhibit quadratic band degeneracy in the (001) surface Brillouin zone (BZ) center ( Γ ¯ point). The gapless surface states and their quadratic dispersion are protected by C 4 and time-reversal symmetries, which correspond to the nontrivial band topology characterized by Z 2 topological invariant. Moreover, the surface states along lines from Γ ¯ to the (001) surface BZ boundary exhibit zigzag feature, which is interpreted from symmetry perspective by building composite operators constructed by the product of glide symmetries with time-reversal symmetry. The metacrystal array surrounded with air possesses high order hinge states with electric fields highly localized at the hinge that may apply to optical sensors. The gapless surface states and hinge states reside in a clean frequency bandgap. The topological surface states emerge at the boundary of the metacrystal and perfect electric conductor (PEC), which provide a pathway for topologically manipulating light propagation in photonic devices.

The thermal conductivity of 3D network reinforced polypropylene matrix composites was constructed by the pickering‐like emulsion method

AbstractPolypropylene (PP) has the advantages of corrosion resistance, easy processing, and low dielectric loss, but its low thermal conductivity limits the application of its composites in fields such as electronic packaging. To solve this problem, in this work, composite microspheres with the segregated structure were prepared by coating boron nitride nanosheets (BNNSs) on the PP surface by Pickering‐like emulsion method, and BNNSs@PP composites with three‐dimensional thermal conductivity network were obtained after molding. Due to the high thermal conductivity of BNNSs and the formation of perfect thermal conduction pathways, the thermal conductivity of the composites reached 1.71 W m−1 K−1 when the content of BNNSs was 10.1 wt%, which was a 713% increase in thermal conductivity for that of pure PP. At the same time, the mechanical properties of the composites were ensured. This method provides a simple and effective technique to improve the thermal conductivity of PP‐based thermally conductive composites, which has a wide application potential in electronic packaging.