Electromagnetic Shielding Behavior Research Articles

Polysilane–Barium Titanate Polymeric Composite Obtained through Ultrasonication

This work describes the synthesis of a polysilane (PSH)–barium titanate (BT) ferroelectric polymer composite that keeps stable in the presence of ultraviolet light (UV). To evaluate the stability in the presence of UV radiation and the mechanism of interaction between the PSH matrix and BT, FTIR measurements were carried out. The UV/VIS absorption measurement reveals that PSH absorbs strongly in the ultraviolet range, while the composite behaves similarly to BT. Although PSH is a semiconductor, the dielectric spectrometry analysis determined that BT is a ferroelectric material due to its high dielectric constant and low dielectric losses. In contrast to the polymer matrix, the composite polymer has a greater dielectric constant and a lower loss permittivity. PSH is a semiconductor, as indicated by its electrical conductivity of 10−5 S/cm; nevertheless, the UV-irradiated polymer has antistatic properties (10−8 S/cm). Irradiated or not, the polymer composite is a semiconductor, with conductivity of 10−6 S/cm, significantly lower than that of PSH. The interaction with electromagnetic radiation indicates electromagnetic shielding behavior for both BT (highest absorption magnitude of −57 dB) and the polymer composite (maximum absorption magnitudes range from 8.4 to −15.2 dB). Based on these research results, the novel composite with specific characteristics may be used in electronic applications in UV-irradiated conditions.

Effect of morphology and microstructure of NiCo nanoparticles on the electromagnetic shielding behavior of flexible and durable NiCo-coated carbon fibers

Effect of morphology and microstructure of NiCo nanoparticles on the electromagnetic shielding behavior of flexible and durable NiCo-coated carbon fibers

Synergetic effect of reduced graphene oxide and reticulated open-cell aluminum hybrid composite foam for high-performance electromagnetic wave absorption

In the present work, open-cell aluminum-reduced graphene oxide composite (Al-rGO) foam with varying concentrations of reduced graphene oxide (rGO) was fabricated through the template method and foam's electrical, mechanical, and electromagnetic shielding behavior was studied. The reticulated Al-rGO foam allows the electromagnetic wave (EMW) to go inside the structure and resulting in multiple scattering which enhances the wave absorption capacity of the material. Adding rGO into open-cell aluminium foam (OCAF) enhances its shielding properties, particularly the absorption component. The Al-rGO3 foam shows a total EMI shielding of ∼62 dB at 8.4 GHz frequency and out of which 61.34 dB (> 99% of total shielding) is the absorption component. The Al-rGO foam also exhibited maximum compressive strength of 2.96 MPa and EMI shielding of ∼62 dB at 1.5 wt% rGO, even though the electrical conductivity reduces with rGO content. This may be due to a greater degree of multiple scattering of EMW inside the cellular structure and different energy losses at rGO-Al interfaces. This work shows a new way to use the lightweight metallic structure for high EMW absorption applications with good mechanical stability in the defense and aerospace sectors.

Design of PDMS/SiO2@MXene composites with “Floatable Interlayer” structure for the electromagnetic shielding behavior improvement

Designing inhomogeneous structure is an efficient method to prepare polymer composites with electromagnetic interference (EMI) shielding. According to principle of phase separation induced by volatilizing solvent, herein, sandwich structure with a SiO2@MXene “floatable interlayer” is designed by regulating the affinity of mixed solvents (dimethylbenzene and tetrahydrofuran) and SiO2@MXene, and then compounded with poly(dimethylsiloxane) (PDMS). The interactions among SiO2@MXene, PDMS and mixed solvents can be dynamically adjusted during solvents evaporation via controlling the nano-SiO2 in/on MXene, which accurately regulates the dispersion of SiO2@MXene in PDMS for further forming floatable conductive interlayer. The composite PDMS/SiO2@MXene-0.25 (SiO2: MXene = 0.25) containing 10 wt% of MXene exhibits typical sandwich structure owing to the opportune specific surface area (545.42 m2 g−1) and surface-loaded SiO2 of the SiO2@MXene-0.25 nanohybrids. The special sandwich structure brings superior performances to the PDMS/SiO2@MXene composites including an average EMI shielding effectiveness of 43.3 dB (0.2 mm in thickness) in X-band, stable mechanical property (remain > 97% after 150 cycles of stretch testing) and wide temperature window in application (-50 ∼ 200 °C). Thus, this study provides a novel method for designing sandwich-like heterostructure of PDMS/SiO2@MXene composites that can be used for EMI shielding in a wide temperature range.

Water vapor transmission and electromagnetic shielding characteristics of stainless steel/viscose blended yarn woven fabrics

In this study, stainless steel/viscose blended yarn was prepared and different structured woven fabrics were prepared for studying the moisture transmission and electromagnetic shielding behaviour. By doubling viscose spun yarn with SS filament yarn, the SS/viscose blended yarn was prepared. The woven fabrics were made in a sample loom using viscose yarn and SS/viscose blended yarn. By changing the metal content, thread density and conductive fibre proportions at different levels, the developed fabrics were analyzed for maximum shielding effectiveness in the frequency of 300 kHz to 1.5 GHz. The fabric having conductive threads in warp and weft directions showed larger shielding effectiveness (SE) compared to fabric having conductive threads in one direction. The increase in weft density, proportions of conductive threads (in weft direction) and metal content increases the shielding level of fabric. The highest SE of 56 dB was observed for plain woven fabric compared to 3/1 twill, 2/2 twill and 2/2 basket fabrics in the frequency of 700 MHz. The influence of environmental factors such as relative humidity and pH on shielding behaviour of fabrics were also studied. As the relative humidity was increased, the SE was also increased. The fabric treated with acidic (or) basic condition exhibited better SE than the fabric in neutral condition. Similarly, air permeability and water vapour transmission characteristics of the developed conductive fabrics were also analyzed. The air permeability of the fabric was higher when the metal content in the fabric was low. The fabric having more floats showed higher air permeability compared to fabrics with less floats. Similarly, the water vapour transmission rate was also high for long float fabrics. The developed conductive fabrics could be used as wall covering and personal protective clothing in defense industry.

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.

Electromagnetic shielding behavior of epoxy multi‐hybrid composites comprises of E‐glass fiber, Ag nanoparticle, and Ni nanosheet: A novel approach

AbstractHigh performance epoxy based EMI shielding hybrid composites were prepared and characterized for their mechanical, magnetic, and Electromagnetic Interference (EMI) shielding behavior. The aim of this research was to enhance the electromagnetic interference shielding effect of a nanocomposite at high frequency with good mechanical strength. The shielding effectiveness of the epoxy composite was improved via the addition of E‐glass/silver nanoparticle and nickel nanosheets. The reinforcements were silane surface modified to enhance the adhesion and dispersion of reinforcements with matrix. The composites were prepared via hand layup process using glass fiber, silver nanoparticle, and Ni nanosheets followed by room temperature curing. The characterization of hybrid composites was done in accordance with ASTM standards. The results revealed that the Ag and Ni along with E‐glass fiber improved conductivity, permittivity, and permeability of epoxy composite. Similarly, the mechanical behavior of nanocomposite was found to be increased for tensile, flexural, and Izod impact toughness. Moreover, a maximum wave attenuation of –48 dB was observed for 3‐mm thick composite shielding material in “J” band frequency. These mechanically sound high EMI shielding lightweight polymer composites could be used as potential material for aerospace, defense, tele‐communication, and satellite data transfer applications. Besides the reduction of EMI effect between electronic gadgets could improves the utility and life span of electromagnetic devices and gadgets in several engineering applications.

Polyaniline/V2O5 composites for anticorrosion and electromagnetic interference shielding

Conducting polyaniline (PANI)/vanadium pentoxide (V2O5) nanocomposites have been synthesized by interfacial polymerization technique. The composites have been characterized by X-ray diffraction (XRD), Fourier transforms infrared (FTIR) spectroscopy, and scanning electron microscopy (SEM). The electrical conductivity (σac) and dielectric measurements have been carried out in the frequency range of 50 Hz to 1 MHz at ordinary lab temperature. The dielectric constant of the composites has been increased to a very high-value of 3.75 × 105 at lower frequency (1 kHz) for 15 wt% concentration of V2O5 in PANI. The electromagnetic shielding behavior of the composites has been investigated in the frequency range 12–18 GHz (Ku-band) of the microwave region. The shielding results demonstrate the synergistic effect of the composite phases with average shielding effectiveness (SE) values in the range of ~17 to 19 dB (<99% electromagnetic energy attenuation). To explore the multifunctional application potential of the composites, surface protection of PANI/V2O5 on mild steel (MS) in 5 M HCl acid solution has been screened by atomic absorption spectroscopy (AAS), Tafel curves, ac impedance, and SEM. AAS and SEM reveal adsorption dominated high inhibition property of these nanocomposites of the order of 91.397%. The potentiodynamic polarization scan indicates both the cathodic and anodic dissolution inhibition role of PANI/V2O5. Nyquist plots greatly sustain the improvement of charge transfer resistance with PANI/V2O5 in the corrosive (5 M HCl) solution. The results show that these nanocomposites could be optimized for diverse applications in corrosion inhibition and stealth technology.

Study of dielectric and electromagnetic shielding behaviour of BaTiO3‐CoFe2O4 filled LDPE composite

AbstractThis paper reports the formation of BaTiO3/CoFe2O4 (BT‐CFO) filled low‐density‐polyethylene (LDPE) composite via the process of melt mixing and characterization for their dielectric and electromagnetic shielding behaviors. The X‐Ray diffraction (XRD) result of synthesized CoFe2O4 shows the cubic phase structure formation with a crystallite size of 28.6 nm. The BT nanopowder and synthesized nanopowder of Cobalt ferrite (CFO) were mixed together in an equal amount (50:50), and sintered at 800°C for 1 hour. A series of samples of BT‐CFO was prepared by taking a different amount of BT‐CFO (ie, 4, 8, 12, 16, and 20 wt%) with LDPE. The dielectric measurements of BT‐CFO/LDPE composites were carried out at different temperatures using LCR meter at a frequency range from 40 Hz to 5 MHz. The dielectric behaviour of samples exhibited a change in dielectric constant with an increase in temperature and frequency. The electromagnetic shielding measurements were examined over X‐band with a frequency range from 8.2GHz to 12.4GHz of the prepared BT‐CFO/LDPE composites. The EMI shielding effectiveness of prepared BT‐CFO/LDPE composites exhibited a maximum value of 17.9 dB.

Electromagnetic shielding behavior of heat-treated Ti3C2TX MXene accompanied by structural and phase changes

Ti3C2TX MXenes have great application prospects in the electromagnetic shielding field owing to their unique accordion structure and excellent electrical conductivity. However, understanding the correlation between their thermal stability and electromagnetic shielding performance is still lacking. Additionally, owing to the complex etching environment, some termination groups are present on the surface of MXenes, significantly affecting their thermal and electromagnetic performance. Here, to solve these problems, a heat treatment process was used. In this study, the effect of heat treatment on the removal of these surface adsorption groups was evaluated. Moreover, the evolution of structure, phase, and electromagnetic shielding properties of MXenes with the change in heat treatment temperature was also studied in detail. After heat treatment at 1100 °C, the phase of MXenes changed. Multilayer-TiC, a derivative of MXenes, still exhibited excellent shielding performance, which can be attributed to the elimination of surface end groups, the maintenance of multiple structure, and the increase in content about amorphous C. The total and absorbing shielding effectiveness reached 76.1 dB and 61.3 dB, respectively. Its conductivity was 265 S/m. This study is valuable in studying application prospects of Ti3C2TX MXene in high temperature fields, such as the field of electromagnetic shielding.

Improved electromagnetic shielding behaviour of graphene encapsulated polypyrrole-graphene nanocomposite in X-band

The graphene encapsulated polypyrrole-graphene nanocomposites containing 0 to 0.2 wt% of graphene have been synthesized through in-situ chemical oxidative polymerization method. The electromagnetic shielding and dielectric behaviour of nanocomposite have been investigated in X-band (8.2–12.4 GHz) of microwave region. Nanocomposite containing 0.2 wt% of graphene (PG2) possess maximum shielding effectiveness due to absorption (SEA) ~ 33 dB and least due to reflection (SER) ≪ 1 dB in X-band. PG2 nanocomposite also has minimum skin depth ~250 μm (a criteria to decide the thickness of material for microwave application) and maximum attenuation constant. Enhanced microwave absorption and extremely suppressed reflection is attributed to increased dielectric loss. Increased dielectric loss is ascribed to formation of multiple interfaces, interfacial polarization, and formation of conducting pathways due to encapsulation of graphene in polypyrrole-graphene nanocomposites. The material exhibiting increased absorption and decreased reflection could be useful for many important applications such as stealth technology in aerospace, microwave communications, and checking of electromagnetic pollution.

Impact of Temperature Variation on the Electromagnetic Shielding Behavior of Multilayer Shield for EMC Applications

Impact of Temperature Variation on the Electromagnetic Shielding Behavior of Multilayer Shield for EMC Applications

The effects of the structural parameters of three-dimensional warp interlock woven fabrics with silver-based hybrid yarns on electromagnetic shielding behavior

The main objective of the present study was to investigate the increase in the electromagnetic shielding effectiveness (EMSE) of a set of five variants of three-dimensional (3D) warp interlock woven fabrics containing silver multifilament yarns arranged in a 3D orthogonal grid. The EMSE enlargement as a factor of increasing the quantity of the conductive material per unit area was investigated. The quantity of the conductive material per unit area in a 3D woven fabric can be enlarged by increasing either the yarn undulation or the number of conductive yarn systems, while the yarn density and yarn fineness are fixed. Thus, the binding depth of the conductive warp was gradually increased for the first four variants in order to increase the yarn undulation. Alternatively, the conductive weft system was doubled for the last variant with the aim of increasing the quantity of the conductive component. It should be noted that changing the weave structure requires less effort and energy while keeping the same threading of warps in the reed compared to altering the warp density. The EMSE was measured in an anechoic chamber and the shielding was satisfactory for all the variants in the frequency range of 1–6 GHz (19–44 dB). The results revealed that increasing only 7% of the waviness degree of the conductive warps led to 17% EMSE improvement due to increasing of the conductive yarns through the thickness of the variants. Moreover, no upward EMSE was detected for the last variant, despite the fact that the conductive weft system was doubled.

Advanced Radar Absorbing Ceramic-Based Materials for Multifunctional Applications in Space Environment.

In this review, some results of the experimental activity carried out by the authors on advanced composite materials for space applications are reported. Composites are widely employed in the aerospace industry thanks to their lightweight and advanced thermo-mechanical and electrical properties. A critical issue to tackle using engineered materials for space activities is providing two or more specific functionalities by means of single items/components. In this scenario, carbon-based composites are believed to be ideal candidates for the forthcoming development of aerospace research and space missions, since a widespread variety of multi-functional structures are allowed by employing these materials. The research results described here suggest that hybrid ceramic/polymeric structures could be employed as spacecraft-specific subsystems in order to ensure extreme temperature withstanding and electromagnetic shielding behavior simultaneously. The morphological and thermo-mechanical analysis of carbon/carbon (C/C) three-dimensional (3D) shell prototypes is reported; then, the microwave characterization of multilayered carbon-filled micro-/nano-composite panels is described. Finally, the possibility of combining the C/C bulk with a carbon-reinforced skin in a synergic arrangement is discussed, with the aid of numerical and experimental analyses.

Investigation of Woven Characteristics on Electromagnetic Shielding Behaviour

Textiles have been highly applied for electromagnetic shielding purposes due to the increasing concern about health issues caused by human exposure to radiation. Properties of conductive yarn, fabric structure, and garment design have extreme effects on the electromagnetic behaviour and comfort of the final product. Lots of electromagnetic shielding textiles are made of metallic yarns regarding their high electrical conductivity. Therefore, some researchers have worked on electromagnetic shielding textiles made of metals. For example; the shielding effectiveness of woven fabrics made of hybrid yarns containing stainless steel wire was investigated. As discussed earlier, the fabric structure has significant effects on electromagnetic protection. Consequently, woven samples were produced using two different commercial electroconductive yarns (PA12 coated with Ag and Inox) to investigate the effects of the fabric structure. The main purpose was to define the best pattern among three basic woven patterns leads to the highest electromagnetic shielding. Moreover, the different weft yarn densities were applied to examine the effects of yarn density on the level of electromagnetic shielding. The electromagnetic shielding effectiveness of all the 2-layer samples was evaluated in the frequency range from 0.8 to10 GHz in an anechoic chamber. The woven sample with higher yarn density of PA12 coated with Ag yarns shows higher protection against radiation. To conclude, the results show that the yarn properties play the main role in shielding as well as yarn density and fabric pattern.

Highly-efficient electromagnetic interference shielding and microwave dielectric behavior of a (Bi2O3 + B2O3)-doped MWCNT/BaTiO3 ceramic nanocomposite

Microwave dielectric properties along with electromagnetic interference shielding effectiveness (EMI SE) of a multi-walled carbon nanotube (MWCNT)/barium titanate (BaTiO3) nanocomposite are investigated in this paper. Appropriate amount of sintering additive (Bi2O3 + B2O3) was doped into some nanocomposites to reduce the sintering temperatures. The dielectric properties of the nanocomposites with various MWCNT and sintering additive contents were evaluated at different microwave frequency ranges. It was found that the incorporation of optimized amount of (Bi2O3 + B2O3) can give rise to significantly good dielectric properties. Results also indicated that incorporation of 6 wt% (Bi2O3 + B2O3) into 1.5 mm-thick nanocomposite containing 8 wt% MWCNT led to an EMI SE greater than 28 dB, suggesting this novel nanocomposite as a promising candidate for microwave absorption and electromagnetic interference applications.

Effect of graphene nanoplatelets structure on the properties of acrylonitrile–butadiene–styrene composites

In this study, the effects of various types of commercial graphene nanoplatelets (XG Sciences xGnP M5, C300, C500, and C750) on the thermal, electromagnetic shielding (EMI SE), electrical and mechanical behavior of an acrylonitrile–butadiene–styrene (ABS) copolymer matrix were investigated. The selected nanofillers were characterized and compared in term of surface area, different oxygen content, dimension and density (X‐ray photoelectron spectroscopy, scanning electron microscopy, and helium pycnometry). Graphene nanoplatelets were dispersed in ABS by direct melt compounding at 2, 4, and 8 wt%. Melt flow index (MFI) values almost linearly decreased with all the type of xGnPs, especially with the highest surface area nanofiller (C750). Moreover, EMI SE of neat ABS was improved from −0.7 dB to −2.5 dB (increase more than 3 times) for xGnP (C300, C500, and C750) and to −6.2 dB (increase about 9 times) for xGnP‐M5, in agreement with proportional reduction of electrical resistivity. xGnP‐M5 also resulted in being most effective in enhancing the tensile modulus which improved up to 64%, while a maximum increment of about 20% was obtained with the others xGnP nanoparticles. However, yield stress slightly decreased for xGnP‐M5 (about −9%) and remained fairly constant for others nanofillers. Halpin–Tsai model used to predict the tensile modulus of the nanocomposites suggested that graphene nanoplatelets were randomly oriented in the ABS matrix in a three‐dimensional (3D) manner. POLYM. COMPOS., 40:E285–E300, 2019. © 2017 Society of Plastics Engineers

Synthesis and electromagnetic shielding behaviour of poly(o‐toluidine)/red mud composite

This paper is an attempt to find out application of red mud in controlling electromagnetic pollution. Composite of PoT/RM has been prepared by in‐situ chemical oxidative polymerization and has been tested for electromagnetic shielding effectiveness. Red mud here acted as a filler material. The incorporation of 50 wt% red mud in the polymer matrix results in a shielding effectiveness of 8.9 dB in 8.2 to 12.4 GHz frequency range (X‐band). Furthermore, the structural analysis, morphology, and magnetization have been studied using XRD, TEM, and VSM techniques, respectively. TEM image of the composite shows the distribution of red mud particles in the polymer matrix. The magnetization decreases on incorporation of red mud in the polymer matrix.

MWCNT modified structure-conductive composite and its electromagnetic shielding behavior

Abstract In this paper, a structure-conductive carbon fiber reinforced composites (CFRPs) were fabricated. Its mechanical and electrical properties were characterized. The contribution of its modifier, multi-wall carbon nanotube (MWCNT) to the overall EMS (electromagnetic shielding) effectiveness of CFRP was analyzed. To simultaneously enhance the mechanical strength and electrical conductivity, the MWCNT was well dispersed into aerospace grade epoxy base resin. Afterward, The MWCNT carrying resin was impregnated over unidirectional fiber yarns to produce unidirectional prepreg, and MWCNT modified CFRP (MWCNT-CFRP) laminates were molded in an autoclave. The static mechanical strength, electrical conductivities, and electromagnetic shielding (EMS) effectiveness of MWCNT-CFRPs were tested. Relative analysis verified the conductivity dependence of their EMS performance, indicating the promising prospect of MWCNT-CFRPs for EMS structural composite.