EM Shielding Research Articles

WITHDRAWN: Shielding performance analysis of flexible multi-layered textile sheets based on polymer substrate

Abstract The need for effective Electro Magnetic Interference (EMI) Shielding became inevitable due to the rise of terahertz range technologies based electronic devices in civil, military and healthcare domains. In this paper we analyzed shielding performances of multilayered textile sheets with flexible polymeric substrate. The analysis considered factors like sensitivity of shielding effectiveness, conductivity of polymer inter-layers, thickness of textiles and frequency range. Many researchers contributed to the problem of EM shielding. The literature revealed that carbon based shielding is not mechanically flexible. Metal based shielding is heavy weight and not easy for tuning performance. Synthetic material with laminated sheets containing textile fabrics and conductive polymers was found a promising solution. Recently Aloia et al. explored shielding performances of flexible multilayer screens based on chemically doped graphene on polymer substrate. However, their research was not considering textiles. Textiles with polymer substrate will have impact in making EM shielding. Therefore further investigation is required to focus on textiles with conductive polymers in making EM shielding. This is the focus of the paper which analyzes various combinations and permutations of textile sheets and polymer substrate. Our mathematical and analytical results revealed that the proposed methodology can help improve decision making on EM shielding effectiveness significantly.

Electromagnetic shielding performance of Co0.5Zn0.4Cu0.1Fe2O4-GO/paraffin wax hybrid nanocomposite through magnetic energy morphing prepared by facile synthesis method

High-performance in electromagnetic interference (EMI) and lightweight materials with very effective shielding properties as well as wide bandwidth are extremely desirable, but their development remains a formidable challenge. With this objective, the present report provides a detailed analysis of the graphene oxide (GO)-Co0.5Zn0.4Cu0.1Fe2O4 (CZCF) nanocomposite (CZCFG) which serves an efficient shielding medium for EM interference in the GHz range. Simple co-precipitation method were used for the preparation of CZCFG nanoparticles. Structural including microstructure, dielectric, magnetic and EM shielding parameters are investigated to recognize their important role in EM shielding performance. Spherical nanoparticles with a maximum magnetization of 43.9 emu/g is achieved, which is well incorporated into the GO layers. Absorption is dominated over reflection loss for EMI shielding and presence of GO in nanocomposite disseminate this absorption power by transforming the magnetic energy to that of dielectric energy in combination with improved impedance matching. As a result, a significant electrical conductivity of 21 s/m and an high EMI shielding efficiency of approximately 53.2 dB over the X- and KU- bands were achieved for the resulting composite with a loading of 60 wt% in paraffin wax, which is quite attractive in the context of recent reported work on conductive polymer nanocomposites. In addition, dipole/interfacial polarization, eddy current effect, and multiple scattering also cause a powerful EMI shielding effect.

An ultra-broadband and optically transparent metamaterial absorber based on multilayer indium-tin-oxide structure

In this work, an ultra-broadband and polarization-insensitive metamaterial absorber (MA) with high optical transparency is presented. Indium-tin-oxide (ITO) films are used as frequency selective surfaces in multiple conductive layers and also as the reflective backplane. Numerical simulation analysis demonstrates that the absorptivity of the proposed absorber exceeds 90% in the frequency range from 10 to 75.5 GHz, corresponding to a relative absorption bandwidth of 153%. The proposed structure has a total thickness of 2.9 mm, which is approximately 1/10 of the free space wavelength of its lowest operating frequency. The absorber also has good polarization insensitivity due to its symmetric geometry. Moreover, for TE-polarized waves, the proposed absorber can maintain an absorptivity greater than 70% for frequencies ranging from 10 to 80 GHz as the incident angle is increased to 45°. For TM-polarized waves, it provides absorptivity of more than 80% at incident angles up to 60°. Surface current distribution on each conductive ITO layer was simulated to analyze the absorption mechanism of the MA. A prototype composed of 16 × 16 unit cells was fabricated and the experimental results show a good agreement with the numerical simulations. Due to its ultra-wideband absorption and wide-incident-angle stability, the proposed MA has potential value in electromagnetic applications such as optically transparent EM shielding and microwave radiation protection.

Impact of Zn2+-Zr4+ substitution on M-type Barium Strontium Hexaferrite’s structural, surface morphology, dielectric and magnetic properties

We report the synthesis of Ba0.5Sr0.5ZnxZrxFe12-2xO19 (x = 0.00–1.00) samples using sol–gel auto combustion method. The Rietveld refinement of XRD data indicates a) pure phase formation, b) increase in lattice parameters with composition and c) the absence of undesirable phases such as α–Fe2O3, BaCO3 and SrCO3. FESEM and TEM micrographs reveal an increase in grain size with ‘x’. The broadening of Raman peaks without any peak shift in all the samples indicates that the Zn2+/Zr4+ions are incorporated into Ba0.5Sr0.5Fe12O19 without altering the local structure. Magnetic measurements reveal that the maximum value of saturation magnetization (Ms) is 67.37 emu/g in x = 0.4 sample. The coercivity (Hc) monotonically decreases from 4.936 KOe to 1.029 KOe with increasing concentration of non-magnetic dopants. The dielectric constant values decreases monotonically as function of frequency for all the samples. The samples because of their superior magnetic properties could be vital for high density perpendicular recording, high density parallel recording EM shielding and permanent magnet applications.

Multilayered salt water with high optical transparency for EMI shielding applications

Electromagnetic interference (EMI) shielding for visual observation applications, such as windows utilized in military or aerospace, is important but difficult to realize due to conventional materials having difficulty in achieving sufficient transparency and EMI shielding simultaneously. In this paper, we present multilayered structures based on salt water for simultaneous highly optical transparency (OT) and EM shielding effectiveness (SE) performance. In the proposed structures, planar acrylic and glass were used as two types of clear substrates to hold salt water. The measured OT of both acrylic/salt water/acrylic and glass/salt water/glass structures was higher than 90% with a nearly uniform light transmission, which introduced a negligible impact on optical observation. Furthermore, both simulations and experimental results demonstrated that the SE of the multilayer structure was higher than 20 dB in the X-band from 7.5 to 8.5 GHz. Moreover, the SE was significantly enhanced by increasing the thickness of the salt water layer. Especially, both OT and SE of the multilayered structures were improved simultaneously by increasing the salinity of the salt water. These proposed structures demonstrate great potential in EMI shielding observation applications.

A Dielectric Panel Design for RCS Reduction and EM Shielding

A novel dielectric panel structure that contains no metal layer or conductive compound is proposed for electromagnetic shielding and radar cross section (RCS) reduction uses. It is configured as a planar slab with periodically positioned holes. By choosing appropriate slab thickness, material properties, aperture-to-dielectric area ratio, and hole spacing, the holey panel can suppress reflection and transmission at the same time for plane wave incidences. It conceals back scattering features of targets behind and the panel-to-target distance is not necessarily a fixed number. A thorough analysis is provided to explain how this metalless, nonabsorptive, periodic structure reduces the reflection level by deforming the plane wave with the propagation delay difference between air and dielectric regions. Simulated and measured results of a prototype designed in the E-band indicate that it can provide more than 15 dB RCS reduction at the designated transmission suppressing frequency and the 10 dB reduction bandwidth is more than 20%.

Composite structure-based transparent ultra-broadband metamaterial absorber with multi-applications

In this paper, an approach is proposed to realize optically transparent metamaterial absorber (OTMA) with ultra-broadband absorption properties by using composite resonant structure. The indium tin oxide (ITO) resistive film is used to construct the resonant structure to induce high ohmic loss and broaden the bandwidth of the resonances, thus achieves more than 90% absorptivity in the wide bandwidth of 8–30.3 GHz, which can cover the X and Ku bands of the airborne and surveillance radar signal frequencies. The novelty of designed structure lies in the properties of larger absorption bandwidth (covering X, Ku, K and part of Ka bands), lower thickness, and absorption capacity over a wide range of incident angles. Moreover, by replacing the intermediate air spacer with polydimethylsiloxane (PDMS) and polymethyl methacrylate (PMMA) dielectrics, the OTMAs that can be used for conformal applications and rigid window glass of stealth armament are designed. This strategy provides more flexibility for the applications of broadband OTMA in different occasions, and has potential application prospects in radar stealth system, EM shielding and transparent RF equipment fields. The average optical transmittance of the whole structure in the visible light range exceeds 78%.

Design and development of polymeric nanocomposite reinforced with graphene for effective EMI shielding in X-band

The effect of filler material concentration on Electromagnetic Interference (EMI) Shielding Effectiveness (SE) of polymeric nanocomposites has been studied. Computational model was developed for shielding performance of graphene polymeric nanocomposites. Nanocomposites were fabricated using High Pressure Resin Transfer Molding (HPRTM) method, latter EM shielding properties were measured experimentally using waveguide technique. It is observed that SE increases with increase in wt% of graphene. From the results, it is perceived that nanocomposite with 2.5 wt% of graphene shows good shielding with the range of −27 dB to −30 dB, doubled in comparison to pure polymeric composite. Numerical simulations of various graphene nanocomposites have been carried out for the prediction of SE while incorporating EM properties of corresponding nanocomposite as input. Excellent agreement between numerical simulations and experimental results has been observed. The developed numerical model predicts SE values of graphene nanocomposites in −30 dB range which certainly falls in the X-band.

A Tri-band Angularly Stable Frequency Selective Surface with Controllable Resonances for EM Shielding

AbstractIn the paper, a tri-band angularly stable frequency selective surface (FSS) with controllable resonances for electromagnetic shielding is proposed. Different from traditional single-layer structure, the FSS proposed is based on cascaded structure that creates three adjustable blocking bands around frequency 5.93 GHz, 7.33 GHz and 9.17 GHz, respectively. The designed FSS has a low profile with thickness of λ0/100, where the λ0 represents wavelength of the first band-stop resonance frequency. Besides, the proposed FSS exhibits stable frequency response up to 70° with respect to different polarizations. Therefore, this FSS is flexible and can be used in electromagnetic shielding field where needs conformal screen. To investigate and understand the operating mechanism better, a equivalent circuit model (ECM) is deduced and given in the Section 2, the calculated results match the full-wave EM simulation results perfectly. Finally, a prototype of this FSS is fabricated and measured, the measurement results are in accordance with the simulation results.

Ultra-fast laser-based surface engineering of conductive thin films

Modern electronics facilitate the need for fast, efficient, and reliable methods for direct laser-based surface engineering of conductive thin film materials on flexible substrates. Recent advances in pulsed laser source development only incrementally increased the processing speeds, as those are limited by the available scanning systems. Our goal was to combine a high pulse repetition frequency high-power pulse-on-demand fiber laser source with an ultra-fast resonant scanner to achieve high throughput surface engineering. The enabling factor to compensate a resonant scanner’s sinusoidal movement were the laser’s intrinsic pulse-on-demand capabilities beyond simple pulse picking solutions.The high temporal resolution at full laser power was exploited for spatially controlled surface texturing, allowing a minimally 3 μm positioning accuracy throughout the scanner’s range at up to 60 m/s scan speed with a 10 μm laser spot size. We applied the setup to processing of ITO and metallic films on flexible substrates for touchscreens, position sensors, or EM shielding. Surface modification and patterning of the conductive layer was successfully demonstrated while keeping the underlying surface intact. We employed a simple laser ablation model in comparison to the experimental data to improve the understanding of the ablation process. The resulting surface topography was observed and analysed.

Lightweight and Flexible Cotton Aerogel Composites for Electromagnetic Absorption and Shielding Applications

AbstractCurrently, a versatile route is urgently required to achieve excellent electromagnetic wave (EMW) absorption and shielding functions simultaneously. A lightweight, flexible and sustainable 3D framework aerogel is designed to reach this goal, which is assembled by unique “1D‐1D” combination, nanoscale carbon nanotubes (CNTs) grown on microscale carbon fiber. EM absorption requires appropriate conductivity of filler to acquire moderate permittivity. On the contrary, EM shielding requires great conductivity to reflect most of the incident EMW. Based on this design concept, the change of electric conductivity of as‐obtained samples through in situ regulation of the growth state of CNTs is successfully controlled. When the CNTs are short and curly, the optimized conductivity favors excellent microwave absorption with wide absorption bandwidth of 5.08 GHz at only 1.6 mm. When the CNTs are long and straight, the increased conductivity is clearly boosted with 29.8 dB EM shielding effectiveness. This elaborate architecture and controlled CNT growth allow the designed 3D framework aerogel to be applied in both EM wave absorption and shielding. This conductivity tunable route gives inspiration for fabricating other efficient EM absorption and shielding devices.

ELECTROMAGNETIC SHIELDING OUT OF PLASMA COATED WOVEN FABRICS

Electromagnetic radiation of telecommunication is undesired in rooms for data privacy [1]. One way to shield EM radiation is by achieving textile fabrics with electrical conductive properties [2,3]. Buildtech technical textiles are used in constructions and as such they need fireproof properties, too. Magnetron plasma sputtering is a novel technique for rendering nanometer scale coatings on woven fabrics. It is an eco-friendly technique, which leaves the bulk properties of the fabric unaltered and modifies only the surface properties. Thus, textile EM shields out of magnetron plasma coated fabrics keep initial properties of textile materials, such as flexibility, light weight, 3D shape-ability, good mechanical resistance and receive as well novel functionalities. The ERA-NET Manunet TexEMFiRe project aims to research Buildtech technical fabrics with electromagnetic shielding and fireproof properties, made out of magnetron plasma coating. TexEMFire envisages an optimization of plasma coated fabrics based on fabric structure parameters (density) and plasma coating parameters (generator power) The project has duration of two years (Apr. 2018-Mar. 2020) and five partners: INFLPR, INCDTP, Majutex from Romania and UniUPO and TecnoLab from Italy. Project website is: http://texemfire.inflpr.ro/ .

Electromagnetic Shielding Effectiveness of Nylon-66 Nanofiber Interleaved Carbon Epoxy Composites

Frequency dependence of the electromagnetic interference shielding effectiveness of carbon fiber epoxy composites have been investigated over the frequency range of 8–18 GHz. The effect of nylon-66 nanofiber interleaving on the shielding effectiveness of the multilayered quasi-isotropic composite has been examined for three different percentages of interleaving of nylon-66 nanofibers. Effect of γ-irradiation on the electromagnetic shielding efficiency has also been investigated. Though attenuation due to absorption is dominant in carbon fiber epoxy composites, it is observed that γ-irradiation helps in improving the attenuation due to reflection of the electromagnetic waves. The observed variations in the EM shielding of the composites are explained on the basis of the measured attenuation of EM radiations by absorption and reflection. The investigation has highlighted the usefulness of the carbon fiber epoxy composites, which are traditionally used in mechanical strength applications, for electromagnetic shielding in the range of microwave frequencies.

A lightweight, strength and electromagnetic shielding polymer composite structure for infant carrier strollers

AbstractElectromagnetic (EM) shielding is a protection about reducing the EM fields in a space by blocking the waves with barriers including conductive materials. EM shielding has become an important concept in recent years as a result of increased EM environment pollution. Its long‐term effects are still being investigated in terms of public health. Because of gaining more and more importance in daily life, there are a large number of research subjects including not only raw materials but also end‐products in the literature. In this study, EM shielding characteristics and strength analysis of a diverse range of polymer composites were evaluated and compared for use in an infant carrier stroller body. This type of strollers is not only used for carrying infants, but also some parts of them are used as baby car seats which should be light and strength. Since, the strollers are commonly used in public areas which the infant is exposed to EM radiation and it is strongly recommended to protect infants from EM radiation, sample polymer composite plates have been produced and electromagnetic shielding effectiveness (EMSE) measurements in an anechoic chamber were performed. According to EMSE performances of the plates in frequency range of 700 MHz to 3 GHz, two of the nine different (carbon, aramid, hybrid, glass fiber) textiles were selected to be used in two infant carrier prototypes. After production of prototypes, samples from these prototypes were taken, tensile and impact tests were performed to determine if the molded structures were strength and light enough.

Powerful absorbing and lightweight electromagnetic shielding CNTs/RGO composite

Combination of lightweight and superior electrical conductive performance is charming for the application of macroscopic graphene foam composite. A porous carbon nanotubes/reduced graphene oxide (CNTs/RGO) foam composite are prepared by freeze-drying and in-situ catalytic grown methods. The CNTs/RGO foam composite consists of interconnected RGO nanosheets as the 3D frame and in-situ growth CNTs as the electromagnetic wave (EM) absorbing reinforcement, which grow on graphene substrate. The in-situ grown CNTs on graphene nanosheets lead to the enhancement of conductive and polarization loss, which results in the enhancement of absorption shielding performance. The CNTs/RGO foam composites with different CNT loading are prepared to investigate their EM shielding properties in X-band. The EM shielding effectiveness (SE) of CNTs/RGO foam composite reaches 31.2 dB with 2 mm thickness, especially the specific EMI shielding effectiveness reaches 547 dB cm3/g with an ultralight density of 57 mg cm−3, the absorption is the primary shielding mechanism. Furthermore, SE value reaches 49 dB with thickness of 3.1 mm. Owing to the unique 3D foam hierarchical architecture, light density and outstanding SE performance, our work shows a promising designable approach of preparing CNTs/RGO foam composite to lightweight and absorption type EMI shielding materials.

Microwave-based preparation and characterization of Fe-cored carbon nanocapsules with novel stability and super electromagnetic wave absorption performance

Microwave-metal discharge was proposed as a facile methodology to prepare unique Fe-cored carbon nanocapsules (Fe@CNCs) with high purity, novel stability and extraordinary electromagnetic wave (EMW) absorption performance. The effect of microwave power, irradiation time and cyclohexane/ferrocene ratio on the production of Fe@CNCs was examined and the properties of the nanocapsules, such as their Fe content, phase, yield, degree of graphitization and associated microstructures were investigated in detail. It was found that the prepared Fe@CNCs, which can easily be separated from the reaction system, displayed exceedingly high electromagnetic wave (EMW) absorption performance over the 2–18 GHz range. At the minimal reflection loss (RL) values over −10 dB, the EMW absorption bandwidth can reach up to 13.8 GHz with an absorber thickness of 1.5–5 mm. In addition, novel thermo-oxidative stability and super anti-corrosion property were also obtained for the Fe@CNCs as no signs of any corrosion or oxidative degradation loss were observed from the accelerated degradation tests in air and acid at temperatures up to 420 °C. The exceedingly high EMW absorption performance coupled with the superior anti-degradation and anti-corrosion properties of the prepared nanocomposite microcapsules highlights the novel capability of microwave-metal discharge in synthesizing advanced metal-cored nanocarbon microcapsules with promising application potentials in diverse fields, such as but not limited to microwave absorption, EM shielding and advanced separations etc.

Excellent Electromagnetic Interference Shielding and High Electrical Conductivity of Compatibilized Polycarbonate/Polypropylene Carbon Nanotube Blend Nanocomposites

Herein, we have fabricated a series of immiscible blend nanocomposites based on polycarbonate/polypropylene (PC/PP) by uniformly dispersing multiwall carbon nanotubes (MWCNTs) via a melt mixing technique. The effect of polypropylene-grafted maleic anhydride (PP-g-MA) as a compatibilizer has played a pivotal role in reducing the interfacial tension and thereby enhancing the attenuation performance of PC/PP blends. The substantial effect of compatibilization on the dispersion of MWCNTs has resulted in higher conductivity values of 0.33 S cm–1, which is a major requirement for designing EM shields. Nevertheless, both the uncompatibilized and compatibilized blend nanocomposites have shown viscoelastic phase separation processes. The percolation networks of MWCNTs in compatibilized PC/PP blends were clearly observed using a high resolution transmission electron microscope. There was also a remarkable 5-fold decrease in the percolation threshold and 2.5 fold increase in total shielding effectiveness (54.78 dB) ...

Electromagnetic shielding properties of carbon‐rich chemical vapor infiltration‐prone silicon carbide matrix composites

AbstractThis study focuses on the electromagnetic interference shielding effectiveness (EMI SE) of SiC nanowire/SiC ceramic composites (SiCnw/SiC) manufactured by chemical vapor infiltration of SiCnw aerogels with carbon‐rich SiC. The total EMI SE of a 1.0 mm thick ceramic composite specimen with density of only 2.68 g/cm3, was found to be 43‐44 dB, which indicates an excellent EM shielding capability of the ceramic composite corresponding to blocking of 99.99% of the incident EM signal. It was found that the carbon‐rich CVI‐SiC matrix possess excellent EM shielding properties, therefore, the CVI‐SiC CMCs themselves possess an excellent EM shielding property as a result of the carbon‐rich SiC matrix.

Review and Analysis of Contemporary Polymer Coats based Electromagnetic Shielding Strategies

Objectives: To understand the existing solutions in electromagnetic shielding strategies categorically on polymer coats based solutions to understand gaps and issues in existing solutions. Methods/Statistical analysis: The method adapted for the process is to conduct a detailed review of literature. Many studies were carried out earlier in the domain. Reviewing such studies, the solutions proposed in the earlier contributions and focusing on the research reports that discuss the directions for future course of research in the domain are the priorities. On the basis of inputs gathered from various studies, the information is collated to derive the requisite information. Findings: It is imperative from the study that predominantly the electromagnetic shielding using the polymers was on lead based solutions. Lead based polymers are used for designing the special aprons and solutions that can support in improving the shielding effects. However, one of the key challenges with lead based protective gears are about the increased weight of the apparel and advanced solutions like CNT can be more resourceful for EM shielding. Application/Improvements: CNT is one of the contemporary solution that is explored in the shielding of electromagnetic radiation and if the CNT polymer composites with blended process can increase the efficiency of shielding electromagnetic radiation.

Lightweight, flexible and thin Fe3O4-loaded, functionalized multi walled carbon nanotube buckypapers for enhanced X-band electromagnetic interference shielding

Electromagnetic interference (EMI) is undesirable and uncontrolled interference with the signal of intelligence. This is controlled by using either novel materials, or appropriate electronic design or a combination of both. In this context, functionalized multiwalled carbon nanotubes (FMWCNTs) have been proposed to use as EM shielding materials because of their promising electromagnetic properties, high flexibility, and high electrical conductivity. The non-functionalised MWCNTs does not demonstrate high shielding of electromagnetic waves but with acid functionalisation and further loading with optimized nanoparticles of Fe3O4, enhanced absorption (15.85 dB), enhanced reflection (9.43 dB), resulted in high total specific shielding effectiveness of around 49.56 dB (g cm−3)−1. All samples were light weight, flexible, thin and self-standing in the form of a buckypaper of thickness of 50 µm and density of 0.51 g cm−3. These buckypapers could be promising materials for electromagnetic shielding via both absorption and reflection. A fine amalgamated system of MWCNTs with half metallic Fe3O4, resulting in enhanced conductivity, in an extremely thin and flexible matrix, is considered to be the main contribution to these high shielding effectiveness values.