Electromagnetic Effectiveness Research Articles

Effect of dielectric and magnetic nanofillers on electromagnetic interference shielding effectiveness of carbon/epoxy composites

Tremendous development in electronic devices and their indiscriminate use has created a severe problem of electromagnetic pollution. Different types of electromagnetic interference (EMI) shielding materials and structures are used to protect electronic devices from the harmful effect of electromagnetic pollution. A present study was conducted to compare the effect of dielectric and magnetic nanofillers on electromagnetic shielding effectiveness (EMI SE) of carbon fiber reinforced composite structures (CFRC). Composites structures were developed using different dielectric and magnetic nanofillers. Effect of nanofillers on microwave absorption properties and reduction in electromagnetic pollution was investigated. Relationship between electrical conductivity and EMI shielding effectiveness in L, S, C, and X-frequency range was also studied. Among the dielectric nanofillers, silicon carbide showed excellent EMI SE in X-frequency range, while among magnetic nanofillers, zinc oxide showed excellent EMI shielding characteristics in a broad frequency range of 100 MHz to 13.6 GHz. Among magnetic nanofillers, CFRC with zinc oxide nanofillers showed the lowest skin depth value of 3.32 × 10−4 mm and among dielectric nanofiller, CFRC with silicon carbide nanofillers gave the lowest skin depth value of 6.49 × 10−4 mm, implying their excellent potential in EMI shielding applications.

Electromagnetic shielding effectiveness for A16061 metal matrix composite based mesh wire reinforced with Flyash for oblique incidence of EM wave

Nowadays, flywire is used exclusively in aeronautical applications. A plane’s complete control is dependent on electronic technology, yet it suffers from high-intensity radiated fields. An electromagnetic shield may be necessary to protect this equipment from external electromagnetic pollution. The current project attempts to create a protective barrier around the operating equipment to enhance its efficiency. AL6061 composite material was used to create a metal matrix mesh shield. It is reinforced with fly ash in various volume fractions, and the electrical characteristics and Shielding Effectiveness are determined (SE). The maximum SE is 45.36dB obtained, which can be effectively used as a shield for aerospace and other applications.

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.

Excellent Thermally Conducting Ni Plating Graphite Nanoplatelets/Poly(phenylene sulfone) Composites for High-Performance Electromagnetic Interference Shielding Effectiveness.

First, nickel particles were deposited on the surface of graphite nanoplatelets to fabricate highly conductive GnPs@Ni core-shell structure hybrid fillers via electroplating. The modified GnPs were blended with polyphenylene sulfone via the solution blending method, followed by the hot-pressing method to achieve high thermally conducting GnPs@Ni/PPSU composites for high performance electromagnetic interference effectiveness. The results showed that in-plane and through-plane thermal conductivity of the composite at the 40 wt% filler loading could reach 2.6 Wm−1K−1 and 3.7 Wm−1K−1, respectively, which were 9.4 and 20 times higher than that of pure PPSU resin. The orientation degree of fillers was discussed by XRD and SEM. Then, heat conduction data were fitted and analyzed by the Agari model, and the heat conduction mechanism was further explored. The testing results also demonstrated that the material exhibited good conductivity, electromagnetic shielding effectiveness and superior thermal stability. Overall, the GnPs@Ni/PPSU composites had high thermal conductivity and were effective electromagnetic shielding materials at high temperatures.

Multifunctional nacre-mimetic Ti3C2Tx films with tunable conductivity and mechanical properties by controlling interlay supramolecular interactions

Nacre-mimetic strategy provides an enlightening approach to design high-performance bioinspired nanocomposites. Yet, it is still a big challenge to integrate excellent mechanical properties and tunable multifunctionality into artificial nacre materials. Herein, we develop a pioneering strategy to simultaneously modulate the electrical conductivity and mechanical properties of nacre-mimetic nanocomposite films by controlling interlay supramolecular interactions. A series of novel waterborne polyurethanes with 2-ureido-4[1H]-pyrimidinone (UPy) quadruple hydrogen bonding motifs in the side-chains were elaborately designed and synthesized, and further assembled with Ti3C2Tx MXene nanosheets to construct lamellar nacre-mimetic nanocomposite films with highly ordered nanostructure. This research revealed for the first time that merely varying the content of UPy groups on polyurethane realize significant modulation of mechanical properties, electrical conductivity, and even the electromagnetic shielding effectiveness of nacre-mimetic nanocomposites. Strikingly, the tensile strength of the nanocomposites can be improved from 87.91 to 136.96 MPa and the electrical conductivity from 3214.0 to 4136.1 S cm−1 when the UPy content is increased from 0 to 15%. Additionally, the nacre-mimetic nanocomposite film is capable of fast responsive Joule heating performance at low trigger voltage. This work would open up a new avenue for fabricating multifunctional and mechanically robust biomimetic nanocomposites.

Effect of processing conditions on electromagnetic shielding and electrical resistivity of injection‐molded polybutylene terephthalate compounds

AbstractThis research introduces an analysis of the anisotropic electrical resistivity (ER) and its relation to the electromagnetic shielding effectiveness (EMSE) for two injection‐molded carbon‐fiber‐reinforced polybutylene terephthalates (PBTs). The properties were measured for 2‐mm thick injection moldings considering the effect of melt temperature, injection velocity, and flow distance. The results for one compound showed an EMSE in the range of 30–40 dB, while EMSE for a compound with lower filler content is in the range of 45–75 dB. A combination of higher temperature and higher velocity leads to an increase of EMSE for both compounds in the range of 3%–8.5%. However, the increase in flow path reduced the EMSE for both compounds up to 10%. A novel experimental apparatus was used to measure the anisotropic ER in the three directions, that is, parallel, perpendicular, and transversal to flow. It is evident that injection molding induced high anisotropy for both compound specimens, and, depending on the processing conditions, produced similar longitudinal resistivity (0.2–4 Ω.cm) but higher transversal resistivity (8–22 Ω.cm). ER properties were compared with EMSE, evidencing an inverse relation as expected. Furthermore, it was found that the longitudinal resistivity is the main contributor to the specimens shielding.

Sandwiched cellulose nanofiber /boron nitride nanosheet /Ti3C2Tx MXene composite film with high electromagnetic shielding and thermal conductivity yet insulation performance

The rapid development of electronic devices has led to widespread demand and research on electronic packaging materials with electromagnetic shielding and thermal conductivity (TC) properties due to the inevitable issues of the electromagnetic radiation and thermal accumulation. However, there exists a huge challenge to simultaneously achieve high electromagnetic shielding and TC as well as the electrical insulation requirement as electromagnetic shielding predominantly relies on electrical conductivity of materials. Multilayer structure can endow composite materials with a variety of properties. Therefore, in this work, we fabricated sandwiched cellulose nanofiber/boron nitride nanosheet/Ti3C2Tx MXene films by using a simple and effective alternating vacuum filtration method, and as a result, the special sandwich structure endows the film with excellent electromagnetic shielding, insulation and TC performance. The composite film has an extremely high electromagnetic shielding effectiveness up to 60.7 dB at 8.2 GHz as well as still maintains good electrical insulation properties due to the presence of the CNF/BNNS layer on the surface. Moreover, when the content of BNNS in the CNF/BNNS layer reaches 70 wt%, the sandwiched film has excellent in-plane TC of 19.97 W m−1 K−1. The sandwiched film with excellent electromagnetic shielding and high TC yet insulation performance has great application value in highly integrated electronic devices.

Electromagnetic Shielding Effectiveness of Glass Fiber/Epoxy Laminated Composites with Multi-Scale Reinforcements

In this study, an experimental investigation has been performed to understand the electromagnetic interference-shielding effectiveness (EMI-SE) of glass fiber/epoxy laminated composites embedded with carbon nanotubes (CNTs) and Fe3O4 nanoparticles, reinforced with micro carbon fibers along the thickness direction. Micro carbon fibers were reinforced along the thickness direction between the laminates using an electro-flocking process and a vacuum infusion process used to fabricate the composites. The EMI-SE of the composites was measured in the X-band frequency range (8–12 GHz). The effect of carbon fibers of three different lengths (80 µm, 150 µm, and 350 µm) with two different fiber densities (1000 and 2000 fibers/mm2) and two different amounts of Fe3O4 nanoparticles (0.5 and 1 wt.%) on total SE, absorption, and reflection was investigated. Due to the synergetic effect of Fe3O4 nanoparticles, CNTs, and carbon fibers, the final EMI shielding of the composites was mainly dominated by the absorption process. The absorption was more pronounced in the composites of longer carbon fibers with improved electrical conductivity. The presence of Fe3O4 nanoparticles also enhanced total SE values with improved magnetic permeability. The composite with micro carbon fibers of 350 µm length and 2000 fibers/mm2 density with 1 wt.% of Fe3O4 nanoparticles showed the maximum value of total SE.

Prediction of the Electromagnetic Shielding Effectiveness of Metal Grid Using Neural Network Algorithm

With the advantages of simple structure, high electromagnetic (EM) shielding effectiveness (SE), wide shielding bandwidth and adjustable transmittance, the metal grid is a popular tool in the field of electromagnetic shielding. In this work, the deep learning algorithm of artificial neural network was used to predict the EM SE of the metal grid. After certain number of trainings, both the SE spectrum and the minimum SE value in a given frequency band can be predicted accurately and effectively. On the other hand, for a target SE, the design parameters of the metal grid structure can be immediately predicted. The results show that the relative mean square deviation of the predicted SE curve is about 5%, the relative error of the minimum SE value of the curve is less than 5%, and the average relative error of the minimum SE value in the predicted frequency band is 11.5%.

Two-step randomized design of multi-rings metallic mesh for ultra-uniform diffraction distribution

We propose a random multi-rings metallic mesh (RMR-MM) with the two-step randomized design process. By randomly shrinking the radii and changing the center positions of the basic rings, adding and interrupting the external common tangent rings, filling random sub-rings and supplementary rings, the superposition probability of diffraction spots generated by the multi-rings is reduced to a ultra-low level and thus ultra-uniform diffraction pattern is achieved. Experiment shows that the maximum high-order diffraction energy of RMR-MM experience an 85.96% drop from that of traditional triangle-distributed basic ring mesh, while the average normalized visible transmittance as high as 95.76% in 400–700 nm is achieved. In addition, the 200-nm-thick aluminum RMR-MM exhibits an electromagnetic shielding effectiveness of over 17.5 dB in the Ku-band. These excellent properties indicate RMR-MM is favorable in transparent electrodes as well as electromagnetic interference shielding application for optically transparent devices.

A one-step graphene induction strategy enables in-situ controllable growth of silver nanowires for electromagnetic interference shielding

The introduction of silver nanowires (AgNWs) with high electrical conductivity into graphene skeletons significantly enhances its electromagnetic shielding performance. However, the complicated procedures and low yield of the AgNWs preparation and the lack of strong interaction between graphene and AgNWs by physical self-assembly method limits the electromagnetic shielding application. Herein, a one-step graphene induction strategy without other nucleating and morphology agents of halide ion is exploited for the in-situ synthesis graphene/AgNWs composite. The O=C–O groups of graphene provide a nucleation site to combine Ag nucleus. Importantly, graphene with oxygen functional groups acts as an “Ag+ pool” to store and release abundant Ag+, supplying consecutively Ag+ for AgNWs growth and inhibiting excessive nucleation. Benefiting from the high ohmic loss of 3D conductive network, the resulting graphene/AgNWs coating exhibits remarkable electromagnetic shielding effectiveness of 76.59 dB. This provides a broad prospect for the as high-performance electromagnetic shielding materials.

Vermicular Ni@RL-CS: Preparation, characterization and its applications in electromagnetic shielding

One-dimensional conductive materials are of great significance to the construction of conductive network in the polymer matrix due to their large aspect ratio. In this work, a nickel-plated rod-like calcium silicate composite (Ni@RL-CS) with unique vermicular structure was successfully fabricated by an electroless plating method. The structure and property of as-prepared Ni@RL-CS were characterized, and its electromagnetic shielding ability was evaluated through mixing with thermoplastic polyurethane (TPU). Results indicate that the Ni@RL-CS shows good electrical conductivity, magnetic property and strong dielectric loss ability. The Ni@RL-CS with a one-dimensional vermicular structure is easier to construct a continuous conductive network in TPU matrix, which greatly improves the electromagnetic shielding effectiveness of the TPU resin. TPU/Ni@RL-CS binary composite with 20 vol% Ni@RL-CS achieves ultrahigh specific EMI SE/thickness of 92.6 dB/mm in the frequency of X-band. By further hybridizing Ni@RL-CS with GNPs, the TPU/Ni@RL-CS/GNPs trinary composite exhibits excellent electromagnetic shielding performance. When the contents of Ni@RL-CS and GNPs are 10 vol% and 1.5 vol%, respectively, the specific EMI SE/thickness of the corresponding trinary composite reaches 74.6 dB/mm in the X-band owe to the dense conductive network, which is 56.5% higher than that of the binary TPU/Ni@RL-CS composite with the same content of 10 vol% Ni@RL-CS.. The synergistic effects of dielectric loss, magnetic loss, and the interfacial polarization loss are the main shielding mechanism. This work provides a strategy to prepare a functional filler based on an insulating inorganic material for electromagnetic shielding. The as-prepared Ni@RL-CS with the unique vermicular structure and outstanding electromagnetic shielding performance can serves as a functional filler to modify polymers for electromagnetic shielding applications.

Ag/GNS conductive laminated woven fabrics for EMI shielding applications

ABSTRACT In flexible electronics, a highly electroconductive, flexible, and durable material is important for various applications. This study describes the property changes in graphene nanosheets (GNSs) doped into a conductive silver (Ag) paste that is used to form a grid-style pattern on a polyurethane hot melt film (PU HMF) for electromagnetic wave shielding. Electrical conductivity, thermal conductivity, and bending tests were performed for materials fabricated by an electronic printing method. The results showed that the conductive paste with a loading of 0.3 wt% GNSs (3SC) had good electromagnetic shielding effectiveness (EMSE, 49.9 dB at 1800 MHz), much better electrical conductivity (4.63*104 S/cm) than the pure silver paste (1.38*104 S/cm), and an improved bending ability. The coefficient of variation of GNS loading (3.01% to 3.80%) under 1000 cyclic bending tests was better than that of the pure silver paste (6.94%) at 2.4% strain, but the results under 500 cyclic elongation tests at 10.0% strain did not exhibit the same pattern. The coefficients of variation (CVs) of all samples in the GNS group (8.3–13.3%) were worse than those of the pure silver group (6.3%) after the elongation test. The reason for the differences in the electrical conductivity and flexibility was explained by the SEM results, which indicated notable damage after the bending and elongation tests. Woven fabrics laminated with a PU/Ag/GNS conductive film that were doped with different amounts of fillers were successfully manufactured by electronic printing and can be used for Electromagnetic Interference (EMI) shielding materials, electrodes for sensor components, wearable elements, smart home textiles, and conductive materials, for example.

A Combination of Enhanced Mechanical and Electromagnetic Shielding Properties of Carbon Nanotubes Reinforced Cu-Ni Composite Foams.

Carbon nanotubes (CNTs) reinforced double-layered Cu-Ni composite foams (Cu-Ni/CNT foams) were prepared through chemical plating and electrodeposition, for the purpose of combining enhanced mechanical and electromagnetic shielding properties. The microstructure characterization revealed a quite uniform dispersion of the CNTs embedded in the metal layers, even after heat treatments. The property testing showed the compressive strength, energy absorption capacity and electromagnetic shielding effectiveness (SE) of Cu-Ni/CNTs foams were significantly improved, as compared to Cu-Ni foams. The heat treatments of the composite foams resulted in an interdiffusion of the Cu and Ni layers, causing an increase of compressive strength and a slight decrease of average SE. The possible mechanisms of the property evolution are discussed.

A Silver Yarn-Incorporated Song Brocade Fabric with Enhanced Electromagnetic Shielding.

The fabrics with electromagnetic interference (EMI) have been used in various fields. However, most studies related to the EMI fabrics focused on the improvement of the final electromagnetic shielding effectiveness (EM SE) by adjusting the preparation parameters while the breathability of the EMI fabrics was affected and the visible surficial patterns on the EMI fabric was limited. In this work, the two samples based on the Song Brocade structure were fabricated with surficial visible pattern ‘卐’. One was fabricated with silver-plated polyamide (Ag-PA) yarns and the silk yarns, the another with polyester (PET) yarns and the silk yarns. The weaving structure of the two samples were investigated by scanning electronic microscopy (SEM) and laser optical microscopy (LOM). The resistance against the EM radiation near field communication (NFC) and the ultraviolet (UV) light was also evaluated. Besides, the surface resistance, the air permeability and the water evaporation rate were investigated. The results revealed that the ‘卐’ appeared successfully on the surface of the two samples with stable weaving structure. The Ag-PA yarn-incorporated Song Brocade fabric had the EMI shielding effectiveness value around 50 dB, which was supported by the low surface resistance less than 40 Ω. The excellent NFC shielding of the Ag-PA yarn-incorporated Song Brocade was also found. The ultraviolet protection factor (UPF) value of the Ag-PA yarn-incorporated Song Brocade fabric was higher than 190. The air permeability and the evaporation rate of the Ag-PA yarn-incorporated Song Brocade fabric was higher than 99 mm/s, and 1.4 g/h, respectively. As a result, the Ag-PA yarn-incorporated Song Brocade fabrics were proposed for both the personal and the industrial scale utilization.

Study on gamma radiation attenuation and non-ionizing shielding effectiveness of niobium-reinforced novel polymer composite

Advanced radiation applications have been widely used and extended to many fields. As a result of this fact, choosing an appropriate shielding material based on the radiation application has become vital. In this regard, the integration of elements into polymer composites has been investigated and contributed to the quantity and quality of radiation shielding materials. This study reports photon attenuation parameters and electromagnetic shielding effectiveness of a novel polymer composite prepared with a matrix reinforced with three different proportions (5, 10, and 15 wt%) of niobium content. Addition of Nb dopant improves both photon attenuation and electromagnetic shielding effectiveness for the investigated composites. Therefore, Nb(15%) polymer composite with highest concentration has been found to be the best absorber for ionizing and non-ionizing radiations. Consequently, the performed analyzes provide evidences that the prepared Nb-reinforced polymer composite could be effectively used as photon radiation attenuator and electromagnetic shielding material.

Conducting Polymeric Composites Based on Intrinsically Conducting Polymers as Electromagnetic Interference Shielding/Microwave Absorbing Materials—A Review

The development of sophisticated telecommunication equipment and other electro-electronic devices resulted in a kind of electromagnetic pollution that affects the performance of other equipment as well as the health of human beings. Intrinsically conducting polymers (ICP), mainly polyaniline and polypyrrole, have been considered as promising candidates for applications in efficient electromagnetic interference shielding (EMI) due to their ease of preparation, light weight, good conductivity and corrosion resistance. One of the important advantages of these materials is the capability to interact with the EM radiation through both absorption and reflection mechanisms thus enlarging the field of application. In this context, this review article describes a recent overview of the existing methods to produce intrinsically conducting polymers and their blends for electromagnetic shielding application. Additionally, it highlights the relationship between preparation methods reported in the literature with the structure and properties, such as electrical conductivity, electromagnetic shielding effectiveness (EMI SE), complex permittivity and permeability of these materials. Furthermore, a brief theory related to the electromagnetic mechanism and techniques for measuring the microwave absorbing properties are also discussed.

Rational design of multi-walled carbon nanotube-reduced graphene oxide hierarchical porous paper toward superior electromagnetic interference shielding

The ever-intensifying electromagnetic (EM) pollution drives the intense demand for EM shielding materials. Through evaporative self-assembly and hydrazine hydrate vapor reduction strategy, intricate multiwalled carbon nanotube (MWCNT) ingeniously anchors on the porous reduced graphene oxide (RGO) paper. The synthesized MWCNT-RGO composite paper manifests a better EMI shielding performance compared with pure RGO. Typically, S5-15 (5 wt% MWCNT, 15 g mixture) furnishes the maximum electromagnetic shielding effectiveness up to 47.88 dB with a thickness of 1.04 mm in the X band. These ingenious bicomponent microstructures possess abundant heterointerfaces and defects. Consequently, they synergistically balance the impedance matching, and contribute to conduction loss, polarization relaxation and multiple reflection and scattering. This work supplies the inspiration for the facile preparation of carbon composite with high EM shielding efficiency and thin lamellation by consolidating MWCNT and RGO to form porous heterostructure.

Research on a projectile-borne measuring apparatus for electromagnetic launcher

In order to evaluate the electromagnetic launch effectiveness and understand the corrosion damage of the electromagnetic launcher, it is necessary to master the magnetic field data in the bore. At present, there is no related research on the measurement of the bore magnetic field of the electromagnetic launcher. Therefore, a small-scale projectile-borne measuring apparatus based on B-dot probe is developed in this paper. This apparatus uses FPGA as the core. Through the static magnetic field measurement experiment, the data of the induced voltage and the induced magnetic field can be obtained. The projectile-borne magnetic field measuring apparatus designed in this paper can accurately measure the bore magnetic field of the electromagnetic launcher, which lays the foundation for further analysis of the influence of the electromagnetic field in the bore on the launch effect and investigation of the corrosion damage of the electromagnetic launcher.

Electromagnetic shielding effectiveness of lightweight and flexible ultrathin shungite plates

Carbon-containing shielding materials, especially with absorbing properties, received a lot of attention from the scientific community as having flexibility, lightness and corrosion resistance. Reducing the thickness of such materials (usually a few millimeters) is also an urgent task. In this paper, we offered results of studying the reflective and absorbing properties of shielding materials from natural graphene-containing shungite. Flexible shungite plates with a thickness of 10–20 μm showed good reflection and absorption similar shielding performance to a thicker 2–3 mm synthetic polymer/carbon based composites. Such characteristics are associated with the fact that shungites are unique natural composites with a conductive carbon matrix and micro-sized dielectric mineral inclusions. Shungite could be considered as a raw to manufacture shielding materials, and as a model for more complete understanding of interaction of radiation with graphene-containing conducting solids in order to improve the shielding performances.