Electromagnetic Radiation Shielding Research Articles

Improving EMI shielding effectiveness and dielectric properties of polyaniline-coated polyester fabric by effective doping and redoping procedures

Conductive polymers with their medium level of conductivity are synthetic materials that can be used as electromagnetic wave absorber. In this work, the effect of aging and washing on the surface resistivity and also the influence of efficient doping and redoping procedure on the dielectric properties and electromagnetic radiation shielding of uniformly polyaniline coated polyester fabric are investigated in the X-band frequency range. They can affect the shielding effectiveness by changing the surface resistivity and dielectric permittivity. It is found that lightweight, flexible, and thin polyaniline-coated polyester fabric sample prepared in 1:1:7 monomer:oxidant:dopant molar ratio and redoped with concentrated HCl vapor shows the highest transmission loss (53–43%) in 8.2–12.4 GHz. Compared to single layer, double and triple layer samples attenuated 71–61% and 83–77% of incident wave, respectively. Absorption was the dominant shielding mechanism. It is also demonstrated that the increment of surface resistivity due to washing of samples is compensated by the redoping process.

Carbonized nano/microparticles for enhanced mechanical properties and electromagnetic interference shielding of cementitious materials

In the present work, carbon nano/microparticles obtained by controlled pyrolysis of peanut (PS) and hazelnut (HS) shells are presented. These materials were characterized by Raman spectroscopy and field emissionscanning electron microscopy (FE-SEM). When added to cement paste, up to 1 wt%, these materials led to an increase of the cement matrix flexural strength and of toughness. Moreover, with respect to plain cement, the total increase in electromagnetic radiation shielding effect when adding 0.5 wt% of PS or HS in cement composites is much higher in comparison to the ones reported in the literature for CNTs used in the same content.

Metal-plated carbon and basalt fabrics for shielding of electromagnetic radiation

The possibility of using metal-plated carbon and basalt fabrics for shielding electromagnetic radiation in a wide frequency range was demonstrated. The electrophysical characteristics of carbon, metal-plated carbon, and metal-plated basalt fabrics were compared. The optimum conditions of metal plating of complex textile structures, ensuring high electrophysical properties of the resulting combined materials, were determined, including the optimum conditions for pretreatment of nonconducting fibers and fabrics prior to metal plating and compositions of low-temperature electrolytes for electroless copper and nickel plating, with which uniform distribution of the metals can be obtained on each element of the textile structure.

Development and investigation of electromagnetic shielding fabrics with different electrically conductive additives

Abstract To obtain the protection against electromagnetic radiation (EMR) emitted by operating electrical and electronic devices, the shielding materials based on woven fabrics coated with the highly conductive layers were designed and investigated. The electrostatic charge dissipation properties and EMR shielding properties within certain frequency bands were investigated and compared with such properties of textile fabrics with incorporated conductive metal fibres. Also the influence of washing on electrical properties of developed fabrics was examined. This study presents technological guidelines for designing coated textile fabrics, which are able to safeguard high electrostatic charge dissipation properties and to provide effective protection against EMR, using two types of electrically conductive coatings. The results of EMR shielding measurements, especially within the range of 2 GHz–20 GHz, showed that fabrics with conductive coatings exhibit certain advantages over fabrics with incorporated metalized yarns. Whereas shielding properties at the low frequency range of 20 kHz–50 kHz for all investigated conductive fabrics are similar despite the type of conductive additive. Methods for measurement of electrostatic properties, reflection and transmission as well as the assessment of EMR shielding effectiveness (SE) are also presented.

The effect of irradiation on electrical and electrodynamic properties of nanocarbon-epoxy composites

The aim of this work is to examine the effect of irradiation on the structure, the electrical resistivity and electromagnetic radiation (EMR) shielding (frequency range of f = 25.5–37.5 GHz) of nanocarbon–epoxy composites (CMs). The graphite nanoplatelets (GNPs) and multi-walled carbon nanotubes (MWCNTs) are used as fillers in epoxy polymer matrix (epoxy resin ED20). Nanocarbon filler content is 1–2.2 vol.%. Polymer-nanocarbon CMs were irradiated by different methods: UV irradiation for 51 h, СuKα X-ray radiation (U = 30 kV, i = 20 mA) for 1 h, electron irradiation (1.8 MeV, the absorbed dose is 1 MGr), ions H+ (1.5 MeV, 5 × 1016), C+ (3 MeV, 4 × 1016). It was shown, that the different types of radiation provide different influence both on the value and character of the temperature dependence of resistivity. The most significant change of resistivity was observed for the specimen irradiated by UV – resistivity decreases almost by three orders (by 806 times), the temperature dependence of resistivity being weakened. For specimens irradiated by UV and X-ray we also have observed the increase of shielding efficiency as compared with initial CM, while the irradiation of specimen by electrons leads to a decrease of shielding efficiency SET. According to Raman investigation results, the irradiation by H+ ions of CM 2 wt.% MWCNTs-ED20 with intensity 1.5 MeV leads to significant destroying of nanotube structure and formation of homogeneous amorphous material.

Optimized Quality Factor of Graphene Oxide-Reinforced PVC Nanocomposite

Graphene oxide (GO)-reinforced polyvinyl chloride (PVC) composite films were prepared by solution blending. The homogeneity of GO dispersion with PVC was confirmed by an optical microscope. Quality factor (Q-factor) as a function of temperature (40–150 °C) was measured within a broadband frequency range of 50–35 MHz. The controlled GO loading demonstrates a crucial impact on the optimization of the Q-factor, resonance frequency (f 0) and wide bandwidth. This nanocomposite may be well suited for electronic applications. The further development of GO-reinforced polymer nanocomposites based on an optimized Q-factor may result in a material for electromagnetic frequency radiation shields for radar and communication towers/devices.

Improved microwave absorption in lightweight resin-based carbon foam by decorating with magnetic and dielectric nanoparticles

Carbon foam (CFoam) decorated with Fe3O4–ZnO nanoparticles significantly improved electromagnetic radiation shielding effectiveness which is mainly dominated by absorption component.

Potential of glassy carbon and silicon carbide photonic structures as electromagnetic radiation shields for atmospheric re-entry

During high-velocity atmospheric entries, space vehicles can be exposed to strong electromagnetic radiation from ionized gas in the shock layer. Glassy carbon (GC) and silicon carbide (SiC) are candidate thermal protection materials due to their high melting point and also their good thermal and mechanical properties. Based on data from shock tube experiments, a significant fraction of radiation at hypersonic entry conditions is in the frequency range from 215 to 415 THz. We propose and analyze SiC and GC photonic structures to increase the reflection of radiation in that range. For this purpose, we performed numerical optimizations of various structures using an evolutionary strategy. Among the considered structures are layered, porous, woodpile, inverse opal and guided-mode resonance structures. In order to estimate the impact of fabrication inaccuracies, the sensitivity of the reflectivity to structural imperfections is analyzed. We estimate that the reflectivity of GC photonic structures is limited to 38% in the aforementioned range, due to material absorption. However, GC material can be effective for photonic reflection of individual, strong spectral line. SiC on the other hand can be used to design a good reflector for the entire frequency range.

A material with high electromagnetic radiation shielding effectiveness fabricated using multi-walled carbon nanotubes wrapped with poly(ether sulfone) in a poly(ether ether ketone) matrix

An electromagnetic radiation absorber material with high shielding effectiveness as well as good mechanical and thermal properties was produced using multi-walled carbon nanotubes (MWCNTs) wrapped in poly(ether sulfone) (PES) dispersed in a poly(ether ether ketone) (PEEK) matrix fabricated by melt-blending. The electromagnetic, mechanical, and thermal properties of this material were characterized using a vector network analyzer, universal tester, and thermal gravimetric analyzer, respectively. The results indicate that wrapped-MWCNT–PEEK composites show different degrees of improvement in the measured properties compared to pure PEEK. This is attributed to the high conductivity of MWCNTs, the good dispersion of wrapped-MWCNTs in PEEK, and the strong interfacial adhesion between wrapped-MWCNTs and PEEK.

Study on Biological Effect Protection of Electromagnetic Radiation Shielding Fabric

In this study, electromagnetic radiation (EMR) shielding fabric was coated by Carbonyl Iron and Nickel powder. X-ray diffraction (XRD) measure was applied to test the existence of Carbonyl Iron and Nickel. In order to study protective performance of EMR shielding fabric for living body, tests on biological effect protection were proceeded respectively using EMR shielding fabric, stainless steel fiber blend fabric and common fabric of the same specification. The results showed that colony forming unit-granulocyte and macrophage (CFU-GM), which expressed the ability of the mice’s hematopoietic function, were obviously improved after using shielding fabric. And all the other biological characterizations of the life that covered the EMR shielding fabric and stainless steel fiber blend fabric were better than that that covered common fabric. Moreover, The EMR shielding fabrics had better protective effect than pure stainless steel fiber blended fabric. The parameters of the Carbonyl Iron and Nickel coated and the stainless steel fiber were the significantly factors to affect the shielding property.

Shielding of electromagnetic radiation by using wood-cement boards modified with carbon in microwave frequency band

The paper focuses on the development of carbon-modified wood-cement boards made of wood-wool for the purpose of shielding electro-magnetic radiation in the microwave frequency band. Powder coal was used as the electric conductive admixture to increase electric conductivity of wood-cement boards, and thus also total insertion loss. Increasing the concentration of carbon up to 25 wt% resulted in considerable rise of electric conductivity by 7 orders. The total insertion loss is directly proportional to thickness of the wood-cement board.

Effect of pyrene treatment on the properties of graphene/epoxy nanocomposites

Graphene is a two-dimensional nanocarbon that is currently being investigated for applications in a variety of areas. Graphene has unusual properties including a large surface area of 2,600 m·g, high thermal conductivity of ~3,000 W m·K, high electrical conductivity of ~550 S·cm, a high modulus of ~1 TPa, and a high aspect ratio of several hundreds. Aksay et al. recently reported that graphene sheets can be produced in bulk by the thermal expansion of sufficiently oxidized graphite oxide (GO). These exfoliated sheets are called functionalized graphene sheets (FGSs) because some of the oxygen containing groups such as epoxy groups remain after thermal treatment. FGSs have an affinity for polar solvents and polymers, as well as have a high electrical conductivity of about 10 S·cm. Polymers such as epoxy resin are generally good electrical insulators. However, an improvement in electric conductivity is necessary for applications that require electrostatic dissipation or electromagnetic radiation shielding. Nanocarbons with high conductivity and a large aspect ratio can be effectively utilized in the preparation of conductive polymer nanocomposites. Recent studies have demonstrated the emergence of FGS as fascinating conductive nanofillers with low percolation thresholds. In nanocomposites, nanofiller dispersion and interfacial interactions with the matrix polymer can be significantly enhanced through chemical or non-covalent physical modification of the nanofiller surface character. Many researchers have reported that polycyclic aromatic hydrocarbons such as pyrene or perylene are strongly adsorbed onto graphene sheets or carbon nanotubes through π-π interactions. We observed that the dispersibility of FGSs in the epoxy resin matrix was improved when the FGSs were treated with pyrene. This paper describes the effect of pyrene treatment on the dispersion, electric, and rheological properties of FGS/epoxy nanocomposites.

Dispersion of iron nano-particles on expanded graphite for the shielding of electromagnetic radiation

Abstract Composite materials containing electrically conductive expanded graphite (EG) and magnetic iron nano-particles for electromagnetic shielding were prepared by impregnating EG with an ethanol solution containing iron nitrate and acetic acid, followed by drying and reduction in H 2 . Magnetic nano-iron particles were found to be highly dispersed on the surface of EG in the Fe/EG composites, and played the role of enhancing the electromagnetic shielding effectiveness (SE) at low frequencies (0.3–10 MHz), which seemed to depend proportionally on magnetic hysteresis loss of loaded iron nano-particles.

Dielectrical properties of composites LDPE+CB

There is currently great interest in the technological properties of conductive polymer composites because their cost-performance balance. They have a wide range of industrial applications -in anti-static materials, self regulating heaters, current overload and overheating protection devices, and materials for electromagnetic radiation shielding. Measurements of the electrical properties of polymer composites are one of the most convenient and sensitive methods for studying polymer structure. A polymer composite differs substantially from a free polymer in a wide range of properties. The presence of filler affects both the electrical, as well as mechanical properties. One of the most important characteristics of conductive polymer composites is that their electrical conductivity increases nonlinearly with the increase of the concentration of filler particles. When the concentration of filler particles reaches a certain critical value, a drastic transition from an electrical insulator to a conductor is exhibited. This conductivity behavior resulting in a sudden insulator-conductor transition is ascribed to a percolation process, and the critical filler concentration at which the conductivity jump occurs is called ?percolation threshold?. In the past few years, a lot of studies have been carried out to analyze the percolation phenomenon and mechanisms of the conductive behavior in conductive polymer composites. It has been established that the electrical conductivity of conductive polymer composites uncommonly depends on the temperature. Some of such composites show a sharp increase and/or decrease in electrical conductivity at specific temperatures. The conductive temperature coefficient (CTC) of conductive polymer composites has been widely investigated. In these work we investigated how concentration of the CB affects the dielectrical properties of the composite LDPE+CB. The ac electrical conductivity, ?ac, for such composites was measured. The temperature and frequency dependence of the dissipation factor were analyzed. It was found that the ac conductivity and dissipation factor were highly affected by the concentration of the filler.

Influence of fabric structural model on shielding effectiveness of electromagnetic radiation shielding fabric

In this paper, the shielding mechanism of electromagnetic shielding fabric was simply introduced to explain the influence of bedded form of silver-plated filament in the fabric on the shielding effectiveness. Then the different bedded models were constructed and the shelf was designed to roll the filament based on the bedded model. The shielding effectiveness of these models was measured according to the standard plain material's testing method of the shielding effectiveness. Results show that when the bedded models are different there are significant changes of the shielding effectiveness. Under the same testing condition the shielding effectiveness of the model in which the yarns were arranged at right angle and kept conducted was the best, while the model, in which the yarns were arranged in parallel, was the worst. And the arrange density of the yarns in the model influenced the shielding effectiveness significantly. It can be concluded that there is a power function between the diagonal length of the grid in the model of two contact sets of yarns arranged at right angle and the shielding effectiveness of the samples, and the shielding effectiveness decreased with the increase of the diagonal length.

Nanocarbon-Epoxy Composites as Electromagnetic Shielding Materials

We present the results of studies of the electromagnetic radiation (EMR) shielding by epoxy-nanocarbon composites (CMs). The EMR frequency range was 25.5–37.5 GHz. Thermoexfoliated graphite and multiwalled carbon nanotubes (CNT) have been used as fillers in CM (the content of a filler was 0.5–2 wt.%). We examined the effect of carbon filler's type in CM on characteristics of the electromagnetic shielding. It is shown that, even for low contents (∼ 1–2 wt.%) of a nanocarbon filler in CMs, the coefficient of EMR transmission is − (25-27) dB (for h = 1 mm).The real ϵ′ and imaginary ϵ″ parts of dielectric permittivity of the composites under investigation have been determined.

Detonation nanodiamond and onion‐like carbon: applications in composites

AbstractSeveral properties and envisioned related applications in structural and functional composites of nanodiamond (ND) and their derivatives, onion‐like carbon (OLC) are reported. The electromagnetic radiation shielding properties of the OLC‐polyurethane composites had been characterized in the 120–165 GHz spectral range for 1–15 wt% OLC loading. It was also demonstrated that nanodiamond particles embedded to a polymer matrix attain photoluminescent properties when irradiated with a flux of MeV protons. This suggests an application of the ND‐polymer coatings as fluorescence‐induced indicators of a proton dose acquired by a spacecraft vehicle. Finally, we report on the fabrication of novel composites of carbon nanotubes incorporated into a nanodiamond matrix obtained by electrophoretic codeposition of these two strongest nanocarbon components. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Electromagnetic radiation shielding by composites of conducting polymers and wood

AbstractPolyaniline or polypyrrole composites with fir or oak wood have been prepared by in situ polymerization of the corresponding monomers in an aqueous suspension of wood sawdust. The percolation threshold of compressed coated particles is located below 5 wt % of the conducting component and, above this limit, the conductivity of most composites was higher than 10−3 S cm−1. The conductivity of composites containing ca 30 wt % of conducting polymer was of the order of 10−1 S cm−1, an order of magnitude lower than that of the corresponding homopolymers, polyaniline and polypyrrole. The conductivity stability has been tested at 175°C. The polypyrrole‐based composites generally lasted for a longer time than pyrrole homopolymers, also on account of the improved mechanical integrity of the samples provided by the presence of wood. The reverse order was found with polyaniline composites. The dielectric properties of the composites were determined in the range of 100 MHz–3 GHz, indicating that thick layers of composite material, ∼ 100 mm, are needed for the screening of the electromagnetic radiation below −10 dB level in this frequency range. Nevertheless, considering the potential production cost of composites and their low weight, such composite materials could be of practical interest in the shielding of electromagnetic interference. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 95: 807–814, 2005

Carbon Black-Filled Polymer Blends: A Scanning Probe Microscopy Characterization

ABSTRACTConducting polymer composites, that consist of a conducting filler randomly distributed throughout an insulating polymer or polymer blend, attract interest in several application fields such as sensors or electromagnetic radiation shielding. The macroscopic electrical resistivity of the filled polyblend strongly depends on the localization of the filler. Here, we investigate the morphology of Carbon Black (CB)-filled polymer blends in order to determine the parameters governing the selective localization of CB in one phase of the blend components or at the interface between the components. The dispersion of the CB particles in the polymer blend is observed by means of Lateral Force Microscopy (LFM) as a function of the blend composition and the load in C.B. The selective localization of CB at the interface enables the reduction of the percolation threshold down to 0.5 wt%; as a result, the mechanical properties of the polymer blend can be fully retained. Different techniques can be used to locate the CB at the interface; we compare their efficiency experimentally.

Electromagnetic radiation shielding by intrinsically conducting polymers

The shielding efficiency of various intrinsically conducting polymers (ICPs) as a function of their intrinsic properties (conductivity and dielectric constant), thickness, and temperature is determined. Two types of shielding, reflection and absorption, by ICPs are discussed. The high shielding efficiencies of highly conducting doped polyaniline, polypyrrole, and polyacetylene are reported and compared to that of copper. The easy tuning of intrinsic properties by chemical processing suggests the wide applications of ICPs, especially polyaniline for shielding.