Electromagnetic Shielding Applications Research Articles

Design and Analysis of Frequency Selective Surface for Ism and Lower Ultra-Wideband Antenna

A Compact, dual-layer Frequency Selective Surface (FSS) is presented for electromagnetic shielding applications. The square loop FSS is modified to provide band rejection characteristics for ISM band and lower Ultra-Wide Band (UWB) covering from 2.2 GHz to 7.1 GHz with the bandwidth of (S21 < -20dB) 4.9 GHz. The novel design exhibits symmetric property due to which it achieves polarization-insensitive stable band rejection of the desired frequency band for various angles of incidences up to 60°. The proposed FSS structure has compact dimensions of 0.170λ x 0.170λ x 0.0117λ. The design was fabricated on either side of the substrate made of FR-4 with a dielectric constant of 4.4 and loss tangent of 0.02. The measured results are well per the simulation results. The proposed FSS in this paper has various applications, including the aerospace industry, hospitals, random, and in the scope of electromagnetic filters, etc.

Microstructure, magnetic, and dielectric interplay in NiCuZn ferrite with rare earth doping for magneto-dielectric applications

The homogeneous conglomerate of ferrite oxide samples with increasing concentration of Neodymium and Lanthanum in the steps 0.02 with the chemical formula Ni0.6Cu0.2Zn0.2Fe2-x(Nd0.5La0.5)xO4 (0 ≤ x ≤ 0.10) were achieved by novel citric acid-metal nitrate sol–gel auto-ignition method. The nano-regime crystallites products were achieved by using Ni, Cu, Zn, La, Nd and Fe nitrates and keeping the metal nitrate to citrate ratio 1:1. The products of ensured recipe in the form of chemical formula resulted in precursor powders were calcined for removal of desiccated impurities. The ready blends were subjected to an exhaustive examination with distinctive characterizations. The completion of the reaction and phase formation temperature was confirmed by thermal analysis and structural confirmations were received by X-ray diffraction (XRD), Scanning electron microscopy (SEM), and Fourier transform infrared (FTIR) spectra. The analytics regarding the local symmetry in crystalline solids and understandings about the ordering phenomenon were discussed with the support of FTIR spectra. The diffractograms contributed to the corroboration that the powders obtained were bearing single phase and spinel structure. Evaluation of TEM and DLS confirms fine particle nature of the particles. SEM analysis and EDAX indicated that the samples were having dense, homogeneous and expected stoichiometric cation ratios. The neodymium and lanthanum content influenced the measured saturation magnetization negatively and coercivity positively. The heightened values in electrical conductivity, high ε′ and low dielectric losses in combination with high saturation magnetization, low coercivity, observed in the present samples make them prospect candidate for microwave and electromagnetic shielding applications.

The Effect of the Waste of Materials and Carbon Nanotube on the Concrete Incorporated with Steel Fibers

The addition of agricultural and industrial solid wastes and nanomaterials to concrete combined with steel fibers to improve the mechanical and electrical properties of concrete was investigated. This approach could be used in advanced applications in electromagnetic shielding and conductive concrete. Steel fibers were used at 2%wt. of sand and (induction furnace slag (EIF), carbon nanotube (CNT), steel wool fibers, prepared corn husks) at 0.5 and 1 wt.%. of cement. Obtained results of using 1% for both carbon nanotube and steel wool with steel fibers in the mixture 4 and 6, respectively, showed the highest rates of compressive strength. A similar result was shown when tested at 3,7 and 28 days of age and compressive strength was 47.4MPa,47.34MPa for the mixture 4 and 6 respectively. The electrical conductivity and electrical resistance of the samples were measured at the age of 7 days. The findings have also shown that adding steel wool as well as( CNT) gave the best results and the sample containing the furnace slag achieved satisfactory results as well.

Graphene Infused Ecological Polymer Composites for Electromagnetic Interference Shielding and Heat Management Applications.

In the age of mobile electronics and increased aerospace interest, multifunctional materials such as the polymer composites reported here are interesting alternatives to conventional materials, offering reduced cost and size of an electrical device packaging. We report a detailed study of an ecological and dual-functional polymer composite for electromagnetic interference (EMI) shielding and heat management applications. We studied a series of polylactic acid/graphene nanoplatelet composites with six graphene nanoplatelet loadings, up to 15 wt%, and three different flake lateral sizes (0.2, 5 and 25 μm). The multifunctionality of the composites is realized via high EMI shielding efficiency exceeding 40 dB per 1 mm thick sample and thermal conductivity of 1.72 W/mK at 15 wt% nanofiller loading. The EMI shielding efficiency measurements were conducted in the microwave range between 0.2 to 12 GHz, consisting of the highly relevant X-band (8–12 GHz). Additionally, we investigate the influence of the nanofiller lateral size on the studied physical properties to optimize the studied functionalities per given nanofiller loading.

Influence of ion beam and silver nanoparticles on dielectric properties of flexible PVA/PANI polymer composite films

ABSTRACT In this work, a solution cast technique was used to prepare flexible nanocomposite films of PVA/PANI/Ag with different concentrations of PANI and AgNPs. The samples were described by X-ray diffraction (XRD), transmission electron microscope (TEM), and infrared spectroscopy, which confirmed the successful synthesis of the nanocomposite films. After that, the PVA/10%PANI/6%Ag nanocomposite film was irradiated by different influences of the oxygen ion beam (8 × 1017, 16 × 1017, and 24 × 1017 ions/cm2). The Ac conductivity, dielectric properties, electric modulus, complex impedance behaviour, and the energy density efficiency of the non-irradiated and irradiated films were measured in the frequency range of 100–106 Hz. The results revealed significant changes in these parameters with an increase in concentrations of PANI and Ag nanoparticles inside the host and also with ion beam irradiation. The reported improvements in this study would open the road for appropriating the unirradiated and irradiated nanocomposite films for electromagnetic shielding and optoelectronic applications.

Efficient fabrication of carbon/silicon carbide composite for electromagnetic interference shielding applications

Ceramic matrix composites are typically prepared by a costly, time-consuming process under severe conditions. Herein, a cost-effective C/SiC composite was fabricated from a silicon gel-derived source by Joule heating. The β-SiC phase was generated via carbothermal reduction, and the carbon fabric showed a well-developed graphitic structure, promoting its thermal and anti-oxidation stabilities. Owing to the excellent dielectric loss in carbon fabric, SiC and SiO2 as well as the micropore structure of the ceramic matrix, the absolute electromagnetic interference shielding (EMI) effectiveness (SSE/t) reached 948.18 dB∙cm2∙g-1 in the X-band, exhibiting an excellent EMI SE. After oxidation at 1000 °C for 10 h in the air, the SSE/t of the composite was only reduced to 846.02 dB∙cm2∙g-1. The C/SiC composite promises the efficient fabrication of high-temperature resistant materials for electromagnetic shielding applications.

Multifunctional Graphene Microstructures Inspired by Honeycomb for Ultrahigh Performance Electromagnetic Interference Shielding and Wearable Applications.

High-performance electromagnetic interference (EMI) shielding materials with ultralow density, excellent flexibility, and good mechanical properties are highly desirable for aerospace and wearable electronics. Herein, honeycomb porous graphene (HPG) fabricated by laser scribing technology is reported for EMI shielding and wearable applications. Due to the honeycomb structure, the HPG exhibits an EMI shielding effectiveness (SE) up to 45 dB at a thickness of 48.3 μm. The single-piece HPG exhibits an ultrahigh absolute shielding effectiveness (SSE/t) of 240 123 dB cm2/g with an ultralow density of 0.0388 g/cm3, which is significantly superior to the reported materials such as carbon-based, MXene, and metal materials. Furthermore, MXene and AgNWs are employed to cover the honeycomb holes of the HPG to enhance surface reflection; thus, the SSE/t of the HPG/AgNWs composite membrane can reach up to 292 754 dB cm2/g. More importantly, the HPG exhibits excellent mechanical stability and durability in cyclic stretching and bending, which can be used to monitor weak physiological signals such as pulse, respiration, and laryngeal movement of humans. Therefore, the lightweight and flexible HPG exhibits excellent EMI shielding performance and mechanical properties, along with its low cost and ease of mass production, which is promising for practical applications in EMI shielding and wearable electronics.

Planar Saltwater Analysis for Transparent Electromagnetic Shielding Applications

Optically transparent electromagnetic applications, such as EMC windows, require high optical transparency (OT) while maintaining good electrical performance which is difficult to achieve with conventional transparent electrodes (TEs). In this paper, we proposed a novel planar saltwater as a solution to overcome the difficulty. The electrical and optical characterizations of the planar saltwater are experimentally investigated with good agreement to theoretical prediction. The saltwater has a high average OT of 91.8% which is highest among conventional TEs. Moreover, the planar saltwater shows a shielding effectiveness (SE) above 22 dB with only 3 mm of thickness in the C-band. The SE can be significantly improved by an increase in the thickness of planar saltwater. Along with other advantages of cheap, safe, easy access, and flexible performance, the saltwater can be considered as a potential candidate for transparent electromagnetic shielding applications.

Flexible electrospun carbon nanofibers/silicone composite films for electromagnetic interference shielding, electrothermal and photothermal applications

• Large-area flexible CNFFs are first prepared for EMI shielding material. • Stacking hot-pressing is suitable for large-scale preparation of AMS films. • The EMI shielding efficiency can reach ~ 100 dB with a low thickness of 0.6 mm. • The AMS films present excellent electro-thermal and photo-thermal performances. High-performance conductive films with electromagnetic interference (EMI) shielding, electrothermal, and photothermal properties are highly promising for the development of wearable devices, artificial intelligence, medical care, etc. However, designing such a film with flexibility and toughness remains a challenge. Here, a flexible and multi-responsive composite film for EMI shielding is proposed by coating large-area electrospun carbon nanofiber films (CNFFs) and silicone with an alternating multilayer structure (AMS). The optimal AMS film presents superior EMI shielding (the EMI shielding effectiveness can reach ~ 100 dB with a low thickness of 0.6 mm). Moreover, ultrafast electrothermal response and gratifyingly photothermal performances are also achieved, which can guarantee the normal functioning of AMS films in cold conditions. Furthermore, the outstanding flexibility can be still maintained even after 1000 continuous bending cycles, without worsening the EMI shielding, electrothermal, and photothermal performances. Such superior properties are attributed to the high electrical conductivity, the large specific surface area of carbon nanofibers (CNFs), and strong interface bonding strength, as well as the alternating multilayer structure. Considering the extraordinary performance and the facile preparation method, AMS films show tremendous potential in large-scale applications as advanced EMI protection materials.

Additively manufactured metastructure design for broadband radar absorption

BackgroundRecent advances in material science and electronics led to the rapid development of communication devices and radar detection techniques resulting in an ever-increasing demand for improved stealth performance of air vehicles during scouts. Absorber design employing metastructure concept has recently become a popular approach to improving radar stealth performance. Metastructure permits the realization of desired absorption characteristics by careful design of geometrical structures and material compositions. In this study, a metastructure designed based on graphite SLS composite for radar absorption has been demonstrated. The unit cell of the proposed structure is simulated by COMSOL Multiphysics to determine the frequency-dependent absorption characteristic of the structure. It is fabricated by using a low-cost selective laser sintering technique of additive manufacturing technology.ResultsThe prototype, while measured, shows effective absorption bandwidth of 1.04 GHz that is in reasonable agreement with the simulated response of 2.08 GHz. The optimized structure exhibits ≤ − 10 dB reflectivity within a broad frequency range extending from 7.60 GHz to 18.00 GHz under normal incidence in both TE and TM polarizations. Furthermore, the absorption performance under different polarizations and incident angles has been investigated. Results indicate that the absorber displays polarization indifference and exhibits a wide-angle of incidence tolerance of up to 45° in TE polarization and 30° in TM polarizations.ConclusionIn this paper, the feasibility of using graphite SLS material to design and 3D print a metastructure design for radar absorbing has been established as confirmed by the simulation and the measurement results. The advantages of low cost, ultra-broad operating band, wide-angle of incidence feature, and polarization insensitivity qualifies the proposed absorber for stealth and electromagnetic shielding applications.

High conductivity and stability of polystyrene/MXene composites with orientation-3D network binary structure

Recently, two-dimensional transition metal carbide/nitride (MXene) and its composites with polymers have attracted great interest from researchers due to their potential applications in flexible electronics, electromagnetic shielding, catalysis, and energy storage. However, the easy oxidation of MXene and the low efficiency of traditional composites preparation methods have brought great challenges to the practical application of polymer/MXene composites. Here, we prepared polystyrene/Mxene (PS/MXene) composites with a 3D conductive network structure through particle construction strategy. Because of the compact and ordered structure, the conductivity of the material reached 3846.15 S/m when the filler content was only 1.81 vol%, and it can retain 53.4% of the initial value after 180 days. Furthermore, based on the 3D network, we orientated the MXene nanosheets in the matrix to form the MXene orientated 3D network binary structure. This unique structure design further increased the utilization rate of MXene and made the material conductivity reach to 4471.13 S/m, with the percolation threshold as low as 0.175 vol%. We believe that this research can provide a feasible way for the practical application of MXene composite materials.

Effective electromagnetic interference shielding using foamy polyurethane composites

AbstractPolyurethane/Graphite composite foam samples with different filler loadings were synthesized for application in electromagnetic shielding. The samples were characterized using Fourier transform infra‐red, thermal gravimetric analysis, scanning electron microscope, universal testing machine, and rheometer. Moreover, to adapt and customize this work in the field of aerospace, the measurements were performed in the X‐band at the range of (8–12) GHz. The results showed that the increase in filler content improves the mechanical properties and thermal stability of the composite materials. The electromagnetic interference shielding effectiveness reached (− 45) dB with 30 wt% filler content. It is expected that the polyurethane/graphite composite foamy materials may be considered a promising material to be used in electromagnetic shielding applications.

Conductance and dielectric properties of hydrogen and hydroxyl passivated SiCNWs* *Project supported by the National Natural Science Foundation of China (Grant No. 11574261) and the Natural Science Foundation of Hebei Province, China (Grant No. A2021203030).

Based on the transport theory and the polarization relaxation model, the effects of hydrogen and hydroxyl passivation on the conductivity and dielectric properties of silicon carbide nanowires (SiCNWs) with different sizes are numerically simulated. The results show that the variation trend of conductivity and band gap of passivated SiCNWs are opposite to the scenario of the size effect of bare SiCNWs. Among the influencing factors of conductivity, the carrier concentration plays a leading role. In the dielectric properties, the bare SiCNWs have a strong dielectric response in the blue light region, while passivated SiCNWs show a more obvious dielectric response in the far ultraviolet-light region. In particular, hydroxyl passivation produces a strong dielectric relaxation in the microwave band, indicating that hydroxyl passivated SiCNWs have a wide range of applications in electromagnetic absorption and shielding.

2D MXenes: Tunable Mechanical and Tribological Properties.

2D transition metal carbides, nitrides, and carbonitrides, known as MXenes, were discovered in 2011 and have grown to prominence in energy storage, catalysis, electromagnetic interference shielding, wireless communications, electronic, sensors, and environmental and biomedical applications. In addition to their high electrical conductivity and electrochemically active behavior, MXenes' mechanical properties, flexibility, and strong adhesion properties play crucial roles in almost all of these growing applications. Although these properties prove to be critical in MXenes' impressive performance, the mechanical and tribological understanding of MXenes, as well as their relation to the synthesis process, is yet to be fully explored. Here, a fundamental overview of MXenes' mechanical and tribological properties is provided and the effects of MXenes' compositions, synthesis, and processing steps on these properties are discussed. Additionally, a critical perspective of the compositional control of MXenes for innovative structural, low-friction, and low-wear performance in current and upcoming applications of MXenes is provided. It is established here that the fundamental understanding of MXenes' mechanical and tribological behavior is essential for their quickly growing applications.

Semi-Crystalline Polyaniline with an Enhanced Conductivity Synthesized with a Novel Binary Dopant Sulfonic Acid-Surfactant: Mechanical, Electrical and Shielding Performances of Nylon/PANI Conductive Fabrics at 9.45 GHz

Aniline was doped by a novel binary dopant agent, sulfonic acid-surfactant. Naphthalene disulfonic acid (NDSA) and an anionic surfactant (sodium dodecyl sulfate, SDS) were used to form the binary dopant agent; synthesis of the doped PANI was accomplished by using ammonium peroxydisulfate (APS) as the oxidant via a hybrid microemulsion polymerization at various temperatures (–10, 0, 20, and 40 °C). The synthesized polyaniline (PANI-NDSA-SDS) salts were characterized by Fourier transform infrared, UV-visible and Raman spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), the electrical properties were determined using a four-point probe method, and the mechanical properties of the fabric samples were also studied. The PANI-NDSA-SDS salts showed a semi-crystalline structure with nanostructure morphology. Among the four polyaniline salts, the PANI-NDSA-SDS prepared at 20 °C showed higher values of conductivity and polymerization yield. In this study, this polyaniline salt was used as coating materials for preparation of conductive Nylon fabrics. As a result, the tensile strength increased by 15%, from 27.21 to 31.42 MPa. Higher electrical performance was obtained for the Nylon/polyaniline composites, 128–724 ohm/square; thus, for electromagnetic shielding applications, the conducting polyaniline coated Nylon fabrics can be used as a shield material for the control of electromagnetic interference at 9.45 GHz, the frequency of the instrument used for the measurements. The conducting fabrics showed an electromagnetic interference value between 20.09 and 34.44 dB.

Impact of the Zr-substitution on phase composition, structure, magnetic, and microwave properties of the BaM hexaferrite

Rapid developments in information technologies and a large rise in electrical and electronic equipment have generated different forms of electronic environmental contamination. Microwave absorption materials are important to avoid the damage that can be caused by electromagnetic radiation. A necessary condition for the absorption of the most incoming radiation is balanced wave impedance at the air/shield interface, which depends on the studied materials' magnetic and electrical properties. The paper introduces the preparation of BaFe12-xZrxO19 (x = 0.1, 0.3, 0.6, 0.9, and 1.2) using a solid-state reaction technique. The studied samples were examined by X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer, and a vector network analyzer. The studied samples showed that controlling the grain size and the prepared samples' magnetic properties play an important role in enhancing the microwave radiation absorption. The examined samples can be a promising absorption material in electromagnetic shielding applications.

Lightweight and flexible poly(ether-block-amide)/multiwalled carbon nanotube composites with porous structure and segregated conductive networks for electromagnetic shielding applications

An innovative method was firstly used to prepare lightweight, deformable, and stable conductive composites with segregated structure and microcellular morphology inside. The segregated structure enables the composites to achieve satisfactory conductivity and electromagnetic interference shielding effectiveness with low multiwalled carbon nanotube content. Additionally, the microcellular poly(ether-block-amide) beads promote the composites to display lightweight and outstanding deformability, while protecting the continuity of conductive network during deformation process. The elongation at break of composites has reached to be 70%, and the hysteresis during cyclic tension and compression is as low as 15%. After undergoing cyclic deformation behavior in tension and compression modes, the conductivity and electromagnetic interference shielding effectiveness of the composites remained almost the same as those original values, indicating well stable conductivity. Thus, this composite with light weight, outstanding deformability and stable conductivity obtained via an environmentally friendly and simple molding process has very advantageous application in flexible electronic field.

Dielectric Relaxation Spectroscopy and Synergy Effects in Epoxy/MWCNT/Ni@C Composites

The dielectric/electric properties of the Ni@C (carbon-coated Ni)/epoxy composites and Ni@C/MWCNTs (multi-walled carbon nanotubes)/epoxy composites loaded with fixed MWCNTs amount just below the percolation threshold (0.09 vol.%) and Ni@C at different concentrations up to 1 vol.% were investigated in broad frequency (20 Hz–40 GHz) and temperature (30 K–500 K) regions. In composites with the only Ni@C nanoparticles, the electrical percolation threshold was determined between 10 and 15 vol.%. Above the percolation threshold the dielectric permittivity (ε’) and the electrical conductivity (σ) of the composites loaded with Ni@C only are high enough, i.e., ε’ = 105 and σ = 0.6 S/m at 100 Hz for composites with 30 vol.% Ni@C, to be used for electromagnetic shielding applications. The annealing to 500 K was proved to be an effective and simple tool to decrease the percolation threshold in epoxy/Ni@C composites. For hybrid composites series an optimal concentration of Ni@C (0.2 vol.%) was determined, leading to the conductivity absolute values several orders of magnitude higher than that of a composite filled with MWCNTs only. The synergy effects of using both fillers have been discussed. Below room temperature the electrical transport is mainly governed by epoxy resin compression in all composites, while the electron tunnelling was observed only in hybrid composites below 200 K. At higher temperatures (above 400 K), in addition to the nanoparticles redistribution effects, the electrical conductivity of epoxy resin makes a significant contribution to the total composite conductivity. The dielectric relaxation spectroscopy allows estimating the nanoparticles distributions in polymer matrix and could be used as the non-destructive and fast alternate to microscopy techniques for general polymer composite fabrication control.

Percolated cermets of nickel/yttrium iron garnet for double negative metacomposites

Dielectric and magnetic properties of percolative nickel/yttrium iron garnet cermets were investigated. With nickel content increasing, microstructure evolution of the cermets exhibited characteristics of percolation, resulting in electrical conductivity increased dramatically and conduction mechanism changed from hopping to metallic behaviors. Negative permittivity and negative permeability were observed. Negative permittivity was caused by the plasmonic state of delocalized electrons. Negative permeability was attributed to magnetic resonance of ferromagnetic constituents and diamagnetic responses of eddy currents induced in interconnected nickel networks. The obtained double negative metacomposites enriched metamaterials and have great potential in electromagnetic shielding, cloaking, and attenuation applications.

Absorptive frequency selective surface with two alternately switchable transmission/reflection bands.

The traditional frequency selective surface (FSS) needs further improvement with the development of stealth technology, and the design of multifunctional FSSs is essential. In this letter, an active absorptive FSS (AFSS) has been designed based on the absorption structure of the spoof surface plasmon polariton (SSPP) and the switching activity of the active FSS. The active FSS embedded with PIN diodes realizes the shift of two transmission/reflection frequency bands by controlling the bias voltage of the feed network, which switches from one band-pass response (at around 3.06 GHz) to the other (at around 4.34 GHz). And when one of the transmission windows switches to the other, the original transmission window closes. The upper plasmonic structure achieves a continuous and efficient absorption band from 6.31 to 8.34 GHz. A sample was also fabricated and carried out to verify the numerical simulation, and the experimental and simulation results are consistent. This work provides new ideas for the design of active AFSS and promotes its application in common aperture radome, antenna isolation, and electromagnetic shielding.