EM Shielding Research Articles

Advanced VO2-Graphene based compact THz absorber for EM shielding and biosensing applications

Advanced VO2-Graphene based compact THz absorber for EM shielding and biosensing applications

New system for green EMI shielding: Organohydrogel with multi-band green electromagnetic shielding, sensing, and infrared-stealth capacity

The investigation of absorption-led shielding mechanisms has now made practical progress as a result of the concept of green EM shielding. The extant studies primarily concentrate on the introduction of magnetic particles into the system, with the objective of enhancing the absorption rate (A) through dielectric-magnetic modulation for absorption-led electromagnetic shielding. In contrast, this paper presents a novel approach whereby PVA, glycerol, and MXene are combined into an organohydrogel (PMG) with oriented pores. This results in the creation of a non-magnetic medium that exhibits high absorption loss in multiple bands, thereby establishing a novel shielding system. The PMG20–3 organohydrogel (0.78 wt % MXene) has a shielding performance in the X-band of 42.34 dB (A/R = 1). In the terahertz band, the organic hydrogel gel exhibits an absorption rate of 99.9 %, a performance that exceeds that of the majority of previously reported systems. The PMG gel displays remarkable flexibility and strength, with a hysteresis return line that remains stable under 1000 compression cycles. Additionally, it offers versatile sensing capabilities and infrared stealth. The findings of this study offer novel insights that may facilitate the accelerated utilization of innovative multifunctional and environmentally conscious electromagnetic interference (EMI) shielding materials.

RGO loaded Fe3O4 strategy to construct high toughness PAM hydrogel for electromagnetic shielding

With the continuous development of electronic products, polymers with EM shielding have received widespread attention. In this study, Fe3O4@RGO was prepared by the hydrothermal synthesis method, which solved the problems of Fe3O4 precipitation and RGO stacking. Using it as a precursor, Fe3O4@RGO/PAM conductive hydrogel was prepared. The research shows that the conductivity of this hydrogel reaches 16.2 S/m at a thickness of 0.3 cm, and the maximum EMI SE is 27.1 dB. Among them, RGO can form a conductive framework, and Fe3O4 can optimize the impedance matching and provide additional magnetic loss. The combined effect of the two makes the hydrogel have excellent EMI SE. In addition, PAM-based hydrogels have good thermal stability, crystallinity, water content, and mechanical properties.

Thin film resonant metasurface absorbers using patch-based arrays on liquid crystal polymer substrates for centimeter-wave applications

This paper reports the design and development of thin-film resonant absorbers for narrowband and multiband operation in the frequency regions centered at 10 GHz. The structure of the resonant metasurface absorber (RMA) is based on a liquid crystal polymer (LCP) thin-film spacer with a copper patch array on the front surface and un-patterned copper film on the back surface of the LCP film. The design and simulation works were carried out using full-wave analysis of the RMA characteristics. The copper-based periodic patch array acts as a metasurface. The perfect RMA for a given LCP film thickness can be obtained through impedance optimization by adjustment of the dimensions of the lattice periods. The electric and magnetic field distributions were studied. The resonant film absorber based on a 100 μm thick LCP film has an electrical thickness of λ/300 at 10 GHz. The experimental work was conducted using a narrowband RMA prototype consisting of 11×11 cells. The measured result of the resonant absorption is at 10.1 GHz, which is in close agreement with the design frequency of 10 GHz. For multiband functionality, double- and quad-band film resonant absorbers have been designed based on a coplanar supercell utilizing the superposition of the resonance effect. The LCP film-based absorbers have the potential to be used in EM shielding and sensing applications in centimeter-wave applications.

Effect of Sodium Ion Addition on Copper Selenide/Chitosan Film Towards Electrical and Shielding Efficiency Improvement

The operation of electronic devices can be disrupted by unwanted electromagnetic signals, affecting its operation. Deploying electromagnetic shielding is a viable solution to minimize the impact of electromagnetic interference (EMI). The conventional methods of electromagnetic shielding use metal gaskets to safeguard sensitive electronic components, which have drawbacks of cost and weight. Hence, electromagnetic shielding polymer can be an alternative to replace metal gaskets. This work investigates the effect of sodium ion (Na) addition to copper selenide/chitosan (CuSe/Ch) film for electromagnetic shielding applications. The shielding polymers were produced using solution casting methods, while the CuSe was synthesized using the chemical coprecipitation method. Impedance spectroscopy and two port waveguide methods were used to characterize the prepared polymer's electrical properties and shielding efficiency. The results indicate that Na incorporation in the CuSe/Ch film resulted in a 47 % decrease in bulk resistivity and increased DC conductivity from 6.07 × 10-6 S/cm to 3.69 × 10˗5 S/cm. The AC conductivity of films containing Na demonstrates a similar level of conductivity at lower frequencies, followed by a sharp increase at higher frequencies, indicating a more substantial influence of Na at higher frequencies. Higher absorption shielding efficiency (SEA) and lower reflection shielding efficiency (SER) were achieved by introducing Na into the CuSe chitosan film. The Na/CuSe/Ch film shows higher total shielding efficiency at an average of 20 dB, equivalent to 99 % of the EM power shield.

Microwave characterization of nanomaterials using planar slot resonator

Nanomaterial characterization using microwaves is needed in nanoscale semiconductor devices, microwave imaging, EM shielding, and wireless communication. Many nanomaterials are used as metallic or dielectric layers in these applications. In this paper, we report the characterization of nanomaterials using planar Microwave Slot Resonator (MSR) which was designed and studied using 3D EM simulation tool. The response of MSR is parameterized which offers a platform to calculate relative permittivity (ε r) and conductivity (σ) from measured high frequency response of nanomaterial loaded MSR. With simplified method, this microwave characterization offers accurate and faster results which be used in design, calculation and numerical analysis of nanomaterial based electronic/optoelectronic devices and sensor/shielding applications.

Broadband metal-free graphite absorber for the shielding of far-infrared radiations

An ultrathin metal-free broadband absorber covering the far-infrared region is designed and implemented. A graphite resonator and reflector are used to provide the dual-resonance with merged spectrum. The graphite resonator is perturbed to improve the impedance bandwidth of the absorber at both the resonances. This helps in obtaining the wide and merged resonance to provide the wide absorption spectrum by maintaining the level of absorption more than 90%. The electromagnetic resonances taking place in the absorber structure are the reason behind the operation of the proposed absorber hence the circuit model analysis is carried out to validate its operation. Moreover, the shielding effectiveness of the absorber can vary from 40 to more than 150 dB proving its capability to be utilized in EM shielding, packaging and thermal storage applications in lower THz frequency band with ultrathin structure.

Design and demonstration of high-power density infrared nonlinear filtering window with EM shielding.

Directional energy weapons such as high-power microwaves and high-energy lasers pose a huge threat to optoelectronic detection systems. With that in mind, we designed an infrared optical window that has a nonlinear optical response to high-energy lasers and electromagnetic shielding to microwaves. By constructing a periodic metal circular hole array structure at the subwavelength scale, surface plasmons resonance is excited and its local field enhanced characteristics are utilized to form information transmission compatibility in the infrared band. At the same time, after laser etching off the subwavelength structure, the remaining metal forms a continuous conductive structure, forming an ultra-wideband shielding layer to achieve ultra-high and wide protection in the microwave band. Moreover, a layer of Ge2Sb2Te5 thin film was deposited between the transparent substrate and the metal film. Utilizing its nonlinear optical properties of high-temperature phase transition to reduce damage of directed energy weapons to the photoelectric detection system and equipment. Thus, when the photoelectric detection system or device is damaged or interfered by signals of different frequency bands or energies, the filtering window can achieve multi-mode shielding function.

Effective attenuation of electromagnetic waves via silane surface modified zinc oxide/polybenzoxazine nanocomposites for EMI shielding application

In recent years, there has been a significant emphasis on advancing nanomaterials with exceptional properties, including high reflection loss (RL), reduced thickness, broad bandwidth, and low density. The primary goal is to augment their effectiveness in absorbing EM waves while maintaining a streamlined manufacturing process. This study, investigated the application of novel thermosetting phenolic resin as a polymeric matrix for EM shielding. Among these resins options, benzoxazine stands out due to its exceptional characteristics, which encompass facile monomer preparation through solvent-free synthesis, the absence of by-product release during polymerization, high thermal stability and superb mechanical properties. The assessement of this resin both individually and in combination with zinc oxide nanoparticles. Silanization of the nanoparticles was confirmed via Fourier transform infrared spectroscopy (FTIR). The thermal properties were investigated through differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). The outcomes indicated that the incorporation of zinc oxide nanoparticles enhanced the material's stability. The thermomechanical attributes of the composites were evaluated using Dynamic Mechanical Analysis (DMA), revealing an increase in the storage modulus and a decrease in the glass transition temperature (Tg). In summary, the results from the electromagnetic tests underscore the remarkable capability of the developed composites in absorbing EM radiation, achieving highly impressive RL values of up to –50 dB. However, they exhibited acceptable shielding efficiency.

Terahertz Optical Properties of Graphite-Cement Paste

Mixing conducting particles in cement present various applications in electromagnetic shielding and in-situ inspection of structures. In this study, graphite was incorporated in cement paste at varying concentrations which enhanced its EM shielding. The samples were characterized using Terahertz Time-Domain Spectroscopy (THz-TDS) to determine its optical properties and calculate for the conductivity. The Ultraviolet-Visible (UV-Vis) spectroscopy was also used to characterize the sample to confirm the variation of graphite content which showed small peaks at 258 nm caused by the excitation of π electrons in the graphitic structure. The refractive index, absorption coefficient and conductivities were determined from the amplitudes and phase difference obtained in the frequency domain. The spectral cut-off in the THz region decreases with increasing graphite content due to THz absorption of graphite. The THz refractive index appeared to be not frequency-independent while the absorption coefficient showed a power-law behavior. The THz conductivities were calculated and was found to be proportional to the graphite content. This is attributed to an increase in the conducting network of cement paste and increase in the charge carriers in the insulating cement matrix.

Superconducting Synchronous Motor Development for Airplane Applications - Mechanical and Electrical Design of a Prototype 100 kW Motor

A 100 kW, 4500 RPM synchronous superconducting motor is being built at the Paihau-Robinson Research Institute, Victoria University of Wellington, New Zealand. The motor has superconducting excitation field coils on the rotor and a conventional stator winding. To minimize mass the motor is an air-core type, meaning no ferromagnetic materials are employed inside the motor. Some of the salient features of this motor include: 1) field winding coils employing REBCO CORC conductor; 2) field coils powered with a contactless superconducting dynamo exciter; 3) an EM shield on the rotor for protecting the field coils from high frequency magnetic fields due to stator harmonics and the switching of the drive electronics; 4) a unique single-layer winding design for the stator winding, where the stator coils are made with copper Litz wire and are liquid-cooled. This paper describes the electrical design and 3D simulation of the motor including the superconducting dynamo, and highlights stator and rotor coil developments that will be validated in the prototype. Sensitivity to critical design parameters has been assessed in simulation and initial sub-system prototypes manufactured for testing. Preliminary design is projecting this motor diameter and axial length as 360 mm and 550 mm respectively, with an efficiency of 96.4 % at the rated load. These numbers may be comparable with permanent magnet motors of similar rating, but this motor is being built to serve as a test-bed for evaluating different technologies for rotor and stator components. The ultimate goal for this program is a 3.0 MW machine with superconducting armature and field windings. In comparison with the permanent magnet motor in 2.5 - 3.0 MW range, the superconducting motors are expected to be 4 to 5 times smaller in size and mass with efficiency exceeding 99 %.

Research on Reflection Mechanism of Nonuniform Plasma

The surface of the near-space hypersonic vehicle is covered with a plasma sheath (PSh) with fluid properties. During the radar detection of hypersonic vehicles, the spatial distribution characteristics of PSh parameters affect the reflected wave intensity and the position of the maximum reflection layer of plasma in the vehicle’s different areas, resulting in significant differences in the intensity and frequency offset of echo signals in various areas. In order to further study the reflection characteristics of nonuniform plasma, this article uses the equivalent wave impedance method to calculate the reflection and transmission coefficients of each layer of plasma, analyzes the reflection intensity distribution mechanism of nonuniform plasma, and reveals the EM shielding effect (ES-effect) of plasma. Based on the typical carrier frequency, collision frequency, electron density, and electron density distribution gradient, the variation law of maximum reflection position and maximum reflection intensity in nonuniform plasma is revealed. The research results lay a theoretical foundation for analyzing echo signal characteristics of the PSh-covered target, radar detection anomaly suppression, and EM stealth.

Improving dispersion and delamination of graphite in biodegradable starch materials via constructing cation-π interaction: Towards microwave shielding enhancement

• Biodegradable graphite/starch materials with high EM shielding were prepared. • Cation-π interaction improved delamination and dispersion of graphite in starch. • Orientation of graphite was also very important to EM shielding performance. • Cation-π interaction could enhance interfacial polarization of microwaves. • Orientation of graphite endowed the Salisbury screen effect. Herein, a low-cost, biodegradable, and high-performance microwave shielding graphite/starch material was fabricated via constructing a cation-π interaction between ammonium ions and graphite. The graphite flakes and starch were firstly mixed with distilled water containing ammonium hydroxide to form graphite/starch slurry under an ultrasonic assistant. The cation-π interaction could improve delamination degree and dispersion of graphite in starch matrix. The slurry was first used as a coating material on the surface of wood and paper to develop shielding packages. The effect of coating thickness and coating layers on EM shielding property of the materials was investigated. Second, the composites with a high orientation of graphite were fabricated by compression at high pressures. The electrical conductivity and EM shielding effectiveness (SE T ) of the materials were greatly enhanced by construction of cation-π interaction and orientation of graphite. Specifically, the EM SE T values increased from 56.9 to 66.8 dB for the composites with 50 wt.% graphite and 2.0 mm in thickness by constructing cation-π interaction. The EM SE T values raised from 17.4 to 66.8 dB via the graphite orientation in the materials with the same components and thickness. The shielding mechanism of the compressed composites with orientation dispersion of graphite was also discussed in comparison to the coating layer with random dispersion of graphite.

Editorial Introduction to the Special Issue on Advances and Perspectives in EM Shielding and Absorbers

The twenty-four papers in this special section focus on electromagnetic shielding and absorbers.

A Review on Graphene‐Based Electromagnetic Functional Materials: Electromagnetic Wave Shielding and Absorption

AbstractElectromagnetic (EM) functional materials play an increasingly important role in solving EM wave pollution in both modern military and civil fields. Graphene‐based materials are the most promising candidates in the applications of EM wave shielding and absorption owing to their remarkable structures and enhanced EM properties. Designing graphene‐based materials with elaborately controlled microstructures and optimized EM properties can effectively improve EM energy attenuation and conversion. Herein, the study begins with the EM attenuation mechanism, and multiscale design strategies of graphene‐based EM functional materials are outlined, including molecular‐scale, micro/nanoscale structure, macroscale structure, and integration of multiscale assembly design strategies. Applications in the EM wave shielding and absorption fields are reviewed, focusing on the latest advances in graphene‐based assemblies such as films, fabrics, and composites. Finally, the current challenges and future directions in this fast‐growing field are predicted.

Recent Progress in Electromagnetic Interference Shielding Performance of Porous Polymer Nanocomposites—A Review

The urge to develop high-speed data transfer technologies for futuristic electronic and communication devices has led to more incidents of serious electromagnetic interference and pollution. Over the past decade, there has been burgeoning research interests to design and fabricate high-performance porous EM shields to tackle this undesired phenomenon. Polymer nanocomposite foams and aerogels offer robust, flexible and lightweight architectures with tunable microwave absorption properties and are foreseen as potential candidates to mitigate electromagnetic pollution. This review covers various strategies adopted to fabricate 3D porous nanocomposites using conductive nanoinclusions with suitable polymer matrices, such as elastomers, thermoplastics, bioplastics, conducting polymers, polyurethanes, polyimides and nanocellulose. Special emphasis has been placed on novel 2D materials such as MXenes, that are envisaged to be the future of microwave-absorbing materials for next-generation electronic devices. Strategies to achieve an ultra-low percolation threshold using environmentally benign and facile processing techniques have been discussed in detail.

Angularly Independent Frequency Selective Surface With Good Ventilation for Millimeter Wave EM Shielding

A distinctive frequency selective surface (FSS) to effectively enhance the electromagnetic shielding performance of high-speed electronic systems while preserving good mechanical ventilation is proposed in this article. The FSS consists of periodic segmented circular patterns in two-dimensional view and hollow vent holes in spatial, which exhibits a wide 2 GHz stopband at the interested frequency of 28 GHz. The new design also demonstrates stability to wave oblique incidence and polarization. The FSS shielding panel is prototyped and measured for validation. A satisfactory agreement between simulation and physical experiment is achieved.

New EMC Effects with Multi-layered Type of EM Shield

Electro-magnetic interference is one of the biggest problems which hinder electrical and/or electronic devices from operating efficiently in addition to the negative impact it can have on environment. However, with proper shielding, unwanted electromagnetic interference can be substantially reduced, hence to achieve better EM compatibility among devices and avail safer environment. This paper presents multi-layered electromagnetic shield design analysis by considering different scenarios. The analysis is based on simulation done using MATLAB

THE GAIN IN SHIEDLING EFFECTIVENESS ACHIEVED BY SUPERPOSITION OF STAINLES-STEEL PLASMA COATED WOVEN FABRICS

Electromagnetic shielding based on textile fabrics is important in applications for ensuring proper work of electronic equipment and for protection of human’s health. Fibre-based materials include a good capability for a precise design of the physical and electric properties of the EM shields. There are two main methods to impart electroconductive properties to textile fabrics: insertion of conductive yarns into the fabric structure and coating with conductive layers. In our approach, both methods were applied: cotton woven fabrics with conductive yarns of stainless steel and silver, were coated by magnetron sputtering with stainless steel layers. Electromagnetic shielding effectiveness (EMSE) was determined by Transversal-Electric- Magnetic (TEM) cell measurement system, according to standard ASTM ES-07. Moreover, EMSE was determined for the superposition of the manufactured textile shields. The stainless-steel plasma coating improves EMSE with 20 dB in case of the fabrics with stainless steel yarns and with 15-17 dB in case of the fabrics with silver yarns, in the frequency range of 0.1-1000 MHz. By superposition of the plasma coated shields, the gain in EMSE achieved was of 6 dB for the fabrics with stainless steel yarns and of 5-8 dB for the fabrics with silver yarns, on the same frequency range. EMSE has significant higher values in case of the superposed shields with silver yarns and stainless-steel coating for the frequency domain of 100-1000 MHz, due to the higher thickness and the significant contribution of the multiple reflection term.

Flexible conductive nanocomposite PEDOT:PSS/Te nanorod films for superior electromagnetic interference (EMI) shielding: A new exploration

How to gain excellent bendable, easily-processable, flexible and high conducting materials with maintaining their brilliant electromagnetic shielding functions has become a great challenge, which hinders its potential applications. In this regard, a polymeric nanocomposite based on telluride (Te) nanorods embedded into poly(3,4-ethylene-dioxythiophene):poly (styrenesulphonate) (Te/PEDOT:PSS) films have been applied for the electromagnetic interference (EMI) wave shielding for the first time. Te/PEDOT:PSS shields with high Te dispersion, excellent adhesion property, good distribution, high compatibility and high anisotropic conductivity (σ// = 87.87 ± 5 and σ⊥ = 36. 78 ± 3 S/cm at 20 wt.%) have a brilliant shielding effectiveness SET = 60.88 dB at 12 GHz for 20 wt.%. The dielectric constants of the shields show an exponential decay behavior with the giga-hertz frequency regime (1−12 GHz). The ε′ > 1 improves with increasing the Te content due to the growth in the interfacial polarization and the free charge carrier’s concentrations inside the shield. The main mechanism beyond shielding effectiveness is the absorption. The impact of 0.1 M of various functionalized (benzene BSA, p-toluene TSA and Chompor CSA) sulfonic acid on the σ//, σ⊥ and SET values has significantly studied by treating the (20 wt.% Te/PEDOT:PSS) shield with these acids. It has been found that the increase in the anisotropic σBSA > σTSA > σCSA is reflected by the increase in SET (BSA) > SET (TSA) > SET (CSA) due to the planar structure of BSA and TSA acids. This study offers an excellent bendable, easily-processable, flexible, conducting and brilliant absorber of EM wave based on Te/PEDOT:SS nanocomposite that can be ranked as one of the highest shields. Finally, it has been expected that this nanocomposite to be applied in biological, EM shields, wearable and electronic devices at an affordable cost.