Shielding Behavior Research Articles

Role of Zinc Oxide and Nickel Nanoparticles on EMI Shielding Behavior of Chopped Carbon Fibre/Electrospun Fibrous Cobalt Epoxy Composites in X and Ku Band Microwave Frequencies

Role of Zinc Oxide and Nickel Nanoparticles on EMI Shielding Behavior of Chopped Carbon Fibre/Electrospun Fibrous Cobalt Epoxy Composites in X and Ku Band Microwave Frequencies

Role of adding carbon nanotubes in the electric and electromagnetic shielding behaviors of three different types of graphene in hybrid nanocomposites

Graphene-related materials (GRM) are promising materials to improve mechanical, electrical, and optical polymer properties. Adding multi-wall carbon nanotubes (MWCNT) on GRM nanocomposites promotes synergistic effects on its electrical properties and electromagnetic interference shielding effectiveness (EMI SE). This study focused on evaluating the addition of MWCNT on three different polycarbonate (PC)/acrylonitrile butadiene styrene (ABS)/GRM nanocomposites. These hybrid nanocomposites were prepared by melt mixing using extrusion and injection-mold processes. The morphologies of the nanocomposites were evaluated by field emission gun scanning electron microscopy (FEG-SEM), and their proprieties were characterized by X-ray diffraction (XRD), oscillatory rheological, dielectric spectroscopy, and EMI SE analyses. The electrical behavior of all hybrid nanocomposites was anisotropic due to the injection-molded preparation process. The lateral size, thickness, and production method of the GRM were indicated to be critical factors for the electrical and EMI SE behaviors of these composites. The nanocomposites with GRM2, which had the smallest lateral size and thickness (graphene nanoplatelets), promoted total attenuation levels around 20 dB with 1.5 wt% of MWCNT, matching the EMI SE required for some commercial applications.

Mass stopping power and nuclear shielding behavior of lead borate glasses: Influence of gamma irradiation on physical properties

Four glassy systems with dissimilar PbO ratios were synthesized by the melting method. Raman scattering was used to study the chemical bonds inside the glass structures and follow the chemical changes occurring inside their networks after using the glasses in a radiation field. The glass samples are based on several tetrahedral and triangular groups where in BO3 is predominant. The energy gap of each sample was calculated from two different equations extracted from absorption and transmission measurements as ETauc and ETrans, respectively. Also, chemical durability has been studied to show the stability of these glasses against acidic environmental effect and followed by SEM images. Our findings showed that radiation effect on the prepared samples did not cause significant variations of structural and optical characteristics, however, increasing PbO concentrations resulting in enhancement of several radiation attenuation competencies. This study presented a comprehensive study of the radiation shielding properties of lead borate glass by assessing the effectiveness of proton, electron, neutron, and gamma shielding. Mass stopping power (ψp) and projected range (PR) values were calculated for proton particles (H1) using SRIM Monte Carlo simulation code and its subroutine TRIM, which predicts the radiation damage and atomic displacements per atom (dpa), while the ESTAR program was used to calculate ψe and the continuous slowing down approximation (CSDA) range for electrons. Furthermore; the findings estimate the excess lifetime cancer risk% for radiation workers behind the glass shields. Also, the glass with the lowest PbO content has the highest ΣR value, whereas the sample with the highest PbO content has the highest MAC value of gamma rays.

Electromagnetic shielding behaviors of planar frequency selective surface fabrics, with emphasis on decoupling analysis, lamination direction and tunable selective frequency

Planar frequency selective surface (FSS) fabrics with grids, strips or patches by simple methods of patching, embroidery, clipping and carving were fabricated. The periodic structures, laminated structures, processing method and materials pertaining to the electromagnetic shielding behaviors were investigated. Firstly, equivalent circuit and electromagnetic (EM) shielding behavior of basic frequency selective structure units and complex fretwork structure were provided, involving the decoupling of complex fretwork structure. In addition, various laminating structures of SPs and SGs were determined, one of superposition of SPs and SGs provides a SE peak of 40.2 dB (average SE of 25.1 dB in the whole frequency domain), the other presents a SE peak of 27.1 dB (average SE of 19.1 dB in the whole frequency regime). Furthermore, tunable selective electromagnetic shielding by a simple mechanical way was provided, which can realize a tunable SE peak varying from 730 MHz to 1580 MHz. This work might provide a perspective for the assemble and analytical approximation of FSS fabrics for scientists and engineers in this cross-disciplinary field.

Fe3O4 nanoparticles decorated flexible carbon foam for efficient electromagnetic interference shielding

Magnetic nanomaterials have been shown to be effective additives to conductive materials for enhancing electromagnetic interference shielding (EMI) shielding performance, but the comprehensive mechanism remains unknown. Herein, a 3D flexible carbon foam composite decorated with Fe3O4 nanoparticles was designed and constructed. The composite exhibited good flexibility and mechanical strength (approximately 45 KPa). Due to the synergistic effect of dielectric and magnetic losses, the composite delivered a shielding effectiveness (SE) of 21 dB in the X-band and a corresponding specific SE (SSE) value of 210 dB cm2/g. The transmission coefficient (T) was discovered to be as low as 0.008, indicating that the composite can successfully shield EM, while the reflection coefficient (R) was found to be higher than the absorption coefficient (A). Moreover, the complicated permittivity, permeability, and magnetism magnetization of the composite were discussed in order to better understand the origin of the composite's shielding behavior.

Investigation of Neutron Shielding Behaviour of Unreinforced and Calcite Reinforced Concrete Samples

Neutron particles are different, due to their nature of interacting directly with the atomic nucleus and making indirect ionization. In this study calcite containing and non-calcite containing concrete samples neutron shielding capabilities was compared with each other. CaCO3 (calcite) added concrete and pure concrete was experimentally compared against an isotropic Am-Be neutron source. Naturally, calcite containing concrete was in heavy form in comparison with pure concrete, means that the aim of these experiment is comparing neutron shielding properties of heavy and light concrete. In both samples, thickness of the samples was started with 2 cm and reach to 10 cm with 2 cm increases. The effect of thickness and the effect of material type on neutron shielding was investigated. According to the test results, pure concrete samples shows better shielding characteristics.

The Impact on Addition of WO3 for Radiation Shielding Properties of TeO2–BaO Glass System

This research focus on a series of (70 – x) TeO2: 30BaO: xWO3 glass systems (where x = 10, 20, 30, 40 and 50 mol%) have been synthesized and simulated in terms of radiation shielding behaviors. The simulation of mass attenuation coefficients (μm ), effective atomic numbers (Z eff) and effective electron densities (N el) were calculated by WinXCom software program at energy ranging from 1 keV to 100 GeV. The method of geometric progression (G–P) fitting has been used to calculated at wide energy ranging from 15 keV to 15 MeV and up to 40 penetration depths (mfp) for build-up factors and energy absorption build-up factors (EBF and EABF). The simulation data reported that WO3 partial replacement of TeO2 in glass system (70 – x) TeO2: 30BaO: xWO3 which shows increased behavior of radiation attenuation and shown best shielding properties. Hence, the prepared glass samples find potential use in transparent shielding material application.

Study of comprehensive shielding behaviors of chambersite deposit for neutron and gamma ray

Comprehensive shielding behaviors of chambersite deposit in China for neutron and gamma ray were systematically analyzed for the first time. Monte-Carlo method simulation technique, American Evaluated Nuclear Data File (ENDF/B-VIII.0), XCOM program and Phy-X/PSD program were used to perform the analysis. Transmission against different neutron resources and cross section for neutrons, mass attenuation coefficient, half value thickness, effective atomic number and electron density for narrow beam gamma ray at 0.001–100000 MeV, and equivalent atomic number, G-P Fitting Parameters, exposure buildup factors and energy absorption buildup factors against wide beam gamma ray for penetration depths up to 40mfp at 0.015–15 MeV were obtained. Shielding performance of chambersite deposit is excellent for high energy and low energy neutrons because of Mn and B respectively, and better than SWX-210. Shielding ability for gamma ray dependent on the element with high-Z or higher content and is between steel-magnetite concrete and ilmenite concrete. The shielding performance for both thermal neutron and gamma ray of the prepared sample is better than SWX-201 and SWX-261. Thus chambersite deposit will be an excellent shielding raw material for both gamma ray and neutron, also combining it with hydrogen rich materials can improve its attenuation properties and expand its possible uses.

Structural design of compressible shape-memory foams for smart self-fixable electromagnetic shielding with reduced reflection

To face the coexistence of the intended and unintended electromagnetic radiation in complex electromagnetic and harsh environment as well as minimize the secondary electromagnetic interference (EMI) pollution, the development of highly designable EMI shields for smart self-fixable EMI shielding with reduced reflection is of great importance. Herein, compressible shape-memory composite foams with strong structural designability have been fabricatd through a simple double dip-coating process, which could not only exhibit excellent shielding effectiveness (SE), but also achieve smart self-fixable SE adjustment under self-fixable compression originating from the ideal thermal/electrical-response shape-memory ability. More importantly, incorporating the concept of structural design, such as the construction of an asymmetric descending gradient structure or reasonable 3D patterns in the foams, could enhance the tunability of EM reflectivity effectively, which contributes to the reduction of EM reflection or even reverse the tendency of EM reflection to increase during the process of self-fixable compression-induced SE adjustment, thus minimizing the aggravated secondary EMI pollution significantly. The strategy and mechanism in this work highlights a significant plateau, on which smart self-fixable EMI shielding behavior with reduced reflection could be realized in highly designable shape-memory foam materials.

Effects of WO3 on Radiation Shielding Properties of WO3–TeO2 Binary Tellurite Glass System

In this research, a series of (100–x)TeO2–xWO3 glass systems (where x = 0, 10, 20, 30, 40 and 50 mol%) have been simulated in terms of radiation shielding behaviors. The simulation of mass attenuation coefficients (μm), effective atomic numbers (Zeff) and effective electron densities (Nel) were calculated by WinXCom software program at energies ranging from 1 keV–100 GeV. The method of geometric progression (G–P) fitting has been used to calculate at wide energies ranging from 15 keV–15 MeV and up to 40 penetration depths (mfp) for buildup factors: exposure and energy absorption buildup factors (EBF and EABF). The simulated data reports that WO3 partial replacement of TeO2 in glass system (100–x)TeO2–xWO3 which increases behavior of radiation attenuation and 50TeO2–50WO3 showed the best shielding properties and potential to use as a transparent shielding material.

Evaluation of three different glassy composites (quinary matrix designed using Cr2O3/Na2O/MnO2) in respect of radiation shielding behaviors

Novel multiple glassy composite materials were offered for gamma shielding applications, photovoltaic applications, nuclear engineering, etc. as an alternative to concrete and pure lead. Studied glassy composite materials demonstrated better gamma-ray shielding than ordinary glass and concrete in the 15 keV–15 MeV energy range. The multiple composites were prepared with (xA + 0.11B + 0.02C + (0.87− x)[(1 − y)D1 + yD2] = 1) recipe. BXCOM software was used to calculate exposure buildup factors (EBFs), energy absorption buildup factors (EABFs), and effective atomic numbers (Z eff). Monte Carlo simulations were performed via MCNP 6.2 code to evaluate the important shielding factors like mass attenuation coefficients (µm ), half-value layers (HVLs) and compared with XCOM results. The quinary composites were compared in each step with each other to determine which component is better for radiation shielding [(Cr2O3/Na2O/MnO2), Sb2O3, B2O3, V2O5, and Fe2O3]. From the investigated ratios, Cr2O3 and MnO2 at 85%, and Na2O at 70% were evaluated to be the best ratios to reduce radiation dose in the incident energy range. Also, Fe2O3 addition at 10% enhanced shielding ability. According to the simulation results, the quinary MnO2 composite (MnO2/Sb2O3/B2O3/V2O5/Fe2O3) was determined to have the best shielding property among all the studied composites. A gamma spectroscopy system with NaI(Tl) detector was used to determine the shielding properties of this best material, experimentally. All the studied composites indicate better gamma shielding properties than concrete, some of them are approaching pure lead.

X-ray shielding behavior of TeO2-Li2O-GeO2-ZnO-Bi2O3 glass system using EPICS2017 library and Phy-X software

X-ray shielding behavior of TeO2-Li2O-GeO2-ZnO-Bi2O3 glass system using EPICS2017 library and Phy-X software

Dual Behavior of Dispersed Ni Nanoparticles for Hydrogen Evolution Reaction at the Interface of Ni/Alkaline Solution

The electrode kinetic parameters, that is, the interaction parameter (ɡ), fractional coverage (θ), and equilibrium constant (K), for the Frumkin adsorption isotherm in the Volmer step cannot be readily determined using conventional methods. These parameters for the Frumkin isotherm of H for the hydrogen evolution reaction (HER) in the Ni/0.1 M KOH (H2O and H2O + dispersed Ni nanoparticles) solutions were determined using the phase-shift method. The Frumkin isotherms of H are K = 9.8 × 10−4 exp(−5.7θ) mol−1 for the 0.1 M KOH (H2O) solution and K NPs = 1.2 × 10−4 exp(−3.5θ) mol−1 for the 0.1 M KOH (H2O + dispersed Ni NPs) solution. The dispersed Ni NPs behave as electrostatic shielding for the H adsorption in the Volmer step and as an electrocatalyst for the H2 evolution in the Tafel and/or Heyrovsky steps. The dual behavior of the dispersed Ni NPs in the HER was similar regardless of the weight of the dispersed Ni NPs. The electrostatic shielding behavior of the dispersed Ni NPs in the HER has been previously overlooked or missed. We hope that the dual behavior of dispersed NPs at the interfaces of electrocatalysts/solutions will be studied in more detail for their potential applications.

Comparative shielding behavior of binary PbO-B2O3 and Bi2O3-B2O3 glasses with high heavy metal oxide contents towards gamma irradiation revealed by collective optical, FTIR and ESR measurements

Selected glasses with high percent of heavy metal oxides (60-85 mol%) from the two binary systems (PbO-B2O3) and (Bi2O3-B2O3) were prepared. Collective characterization of the prepared glasses was carried out through optical, FTIR and ESR spectral measurements before and after gamma irradiation. Optical absorption data of these glasses indicate the appearance of distinct UV absorption bands which are related to unavoidable contaminated trace iron impurities (Fe3+ ions) together with the presence of absorption due to Pb2+ or Bi3+ ions. Gamma irradiation causes some obvious variations in the UV spectra of the lead borate glasses but the bismuth borate glasses are more stable. FTIR spectral measurements reveal the appearance of vibrational bands due to triangular BO3 and tetrahedral BO4 groups within their different characteristic wavenumbers. The deconvoluted IR spectra refer to the interfering vibrational bands due to PbO4, BiO3, BiO6 groups beside the presence of the two highly distinguish differently coordinated borate groups (BO3, BO4). The effects of gamma irradiation on the FTIR spectra are limited on lead borate glasses and bismuth borate glasses but are more noticed in the equalization of the intensities of both the vibrations due to tetrahedral and triangular borate groups due to the light weight of the boron element which shows response in triangular groups but less effect in compact tetrahedral borate groups. Also, the near-IR bands due to vibrations of OH, water are observed to decrease dut to their loose bonding in the network.ESR data indicate the stabilization upon irradiation of Bi2O3-B2O3 glass while the PbO-B2O3 show small changes.

Effective EMI shielding behaviour of thin graphene/PMMA nanolaminates in the THz range

The use of graphene in a form of discontinuous flakes in polymer composites limits the full exploitation of the unique properties of graphene, thus requiring high filler loadings for achieving- for example- satisfactory electrical and mechanical properties. Herein centimetre-scale CVD graphene/polymer nanolaminates have been produced by using an iterative ‘lift-off/float-on’ process and have been found to outperform, for the same graphene content, state-of-the-art flake-based graphene polymer composites in terms of mechanical reinforcement and electrical properties. Most importantly these thin laminate materials show a high electromagnetic interference (EMI) shielding effectiveness, reaching 60 dB for a small thickness of 33 μm, and an absolute EMI shielding effectiveness close to 3·105 dB cm2 g−1 which is amongst the highest values for synthetic, non-metallic materials produced to date.

Ta2O5 Nanocrystals Strengthened Mechanical, Magnetic, and Radiation Shielding Properties of Heavy Metal Oxide Glass.

In this study, for the first time, diamagnetic 5d0 Ta5+ ions and Ta2O5 nanocrystals were utilized to enhance the structural, mechanical, magnetic, and radiation shielding of heavy metal oxide glasses. Transparent Ta2O5 nanocrystal-doped heavy metal oxide glasses were obtained, and the embedded Ta2O5 nanocrystals had sizes ranging from 20 to 30 nm. The structural analysis of the Ta2O5 nanocrystal displays the transformation from hexagonal to orthorhombic Ta2O5. Structures of doped glasses were studied through X-ray diffraction and infrared and Raman spectra, which reveal that Ta2O5 exists in highly doped glass as TaO6 octahedral units, acting as a network modifier. Ta5+ ions strengthened the network connectivity of 1–5% Ta2O5-doped glasses, but Ta5+ acted as a network modifier in a 10% doped sample and changed the frame coordination units of the glass. All Ta2O5-doped glasses exhibited improved Vicker’s hardness, magnetization (9.53 × 10−6 emu/mol), and radiation shielding behaviors (RPE% = 96–98.8%, MAC = 32.012 cm2/g, MFP = 5.02 cm, HVL = 0.0035–3.322 cm, and Zeff = 30.5) due to the increase in density and polarizability of the Ta2O5 nanocrystals.

Electromagnetic Interference Shielding Behavior of Magnetic Carbon Fibers Prepared by Electroless FeCoNi-Plating.

In this study, soft magnetic metal was coated on carbon fibers (CFs) using an electroless FeCoNi-plating method to enhance the electromagnetic interference (EMI) shielding properties of CFs. Scanning electron microscopy, X-ray diffraction, and a vibrating sample magnetometer were employed to determine the morphologies, structural properties, and magnetic properties of the FeCoNi-CFs, respectively. The EMI shielding behavior of the FeCoNi-CFs was investigated in the frequency range of 300 kHz to 3 GHz through vector network analysis. The EMI shielding properties of the FeCoNi-CFs were significantly enhanced compared with those of the as-received CFs. The highest EMI shielding effectiveness of the 60-FeCoNi-CFs was approximately 69.4 dB at 1.5 GHz. The saturation magnetization and coercivity of the 60-FeCoNi-CFs were approximately 103.2 emu/g and 46.3 Oe, respectively. This indicates that the presence of FeCoNi layers on CFs can lead to good EMI shielding due to the EMI adsorption behavior of the magnetic metal layers.

Finite element modeling of electromagnetic properties of 3D printed materials in X‐band spectrum

AbstractMicrowave absorbers are distinctive class of materials, which are used to absorb undesired electromagnetic waves in the microwave spectrum. A finite element modeling approach was utilized in the present study to investigate the microwave absorption properties of three different materials such as polycaprolactone (PCL) polymer, polycaprolactone‐carbonyl iron particle (CIP) composite with random orientation of CIPs, and polycaprolactone‐carbonyl iron particle composite with oriented chain structures of CIPs, fabricated by extrusion‐based 3D printing process. A two‐dimensional model was formulated comprising the material under test and two rectangular waveguides attached to the vector network analyzer. A two‐port network model was used to emulate the real‐time experimental environment. It was found from the electric field distribution plot that the oriented PCL‐CIP model reflects and transmits marginal amplitude of electromagnetic waves when compared with nonoriented PCL‐CIP model followed by pure PCL model. The simulation results were validated with the experimental findings. A minimum loss of electromagnetic energy was observed for oriented model as compared to other models, supporting the experimental findings. Larger domain wall motions and micro capacitor behavior of oriented chains of carbonyl particles were responsible for such microwave absorption properties of oriented composites. The practical utility of the present modeling and simulation approach is multifold as it can be utilized to investigate and compare the electromagnetic shielding behavior of various polymeric composites without any material wastage, machine utilization, and physical testing.

Electromagnetic shielding, resistance temperature-sensitive behavior, and decoupling of interfacial electricity for reduced graphene oxide paper

Electromagnetic shielding behavior, resistance temperature-sensitive behavior, interfacial electricity, and their variations with heating treatment of the reduced graphene oxide (RGO) paper are of concern. Herein, self-assembling RGO papers were prepared by solution-phase deposition method. An electromagnetic shielding efficiency (EMSE) of 64 dB shielding (corresponding to a SE/Grammage of 7032 dB/(g/cm2)) covering X-band (8–12 GHz) were obtained. In addition, resistance temperature-sensitive behavior of RGO paper is investigated, and equivalent circuit model is established to decouple interface electricity. The relative resistance variations of RGO paper is caused by the temperature, and the value of ∆R/R0 drops by around 36% when the RGO paper temperature increase from 200 °C to 800 °C. This graphene-based paper provides a simple experimental approach to prepare graphene papers with remarkable electromagnetic shielding performances. More importantly, a qualitative decoupling analysis method is provided for the study and analysis of interfacial electricity. These results and decoupling method can provide useful data and method for carbon-based microwave blockers, sensors and other technologies.

Enhanced electromagnetic shielding property and anisotropic shielding behavior of corrugated carbon fiber felt composite and its sandwich structure

This work fabricated flat, corrugated, and corrugated sandwich short-chopped carbon fiber (SCF) felt/epoxy resin matrix composites for understanding the effect of fiber orientation in three-dimensional space on electromagnetic shielding property. Electromagnetic interference shielding effectiveness (EMI SE) in X band was experimentally investigated and electromagnetic simulation was carried out for investigating the surface current distribution. The results show that EMI SE of corrugated SCF felt composite decreases from 39.8 dB to 18.7 dB (@8.2 GHz) when the angle between transverse corrugated direction and field polarization direction increases from 0° to 90°, indicating obvious in-plane anisotropic shielding property. Corrugated sandwich SCF felt composite consisting of two flat and one corrugated felts has excellent EMI SE (>70 dB) in X band, which mainly results from multiple reflection in corrugated core. This kind of composite possesses good anti-compression ability and great deformability, demonstrating great potential in application of structural–functional integration and light-weight shielding composites.