Electromagnetic Interference Pollution Research Articles

Materials’ Properties of Lightweight Spiral Hybrid CNT/Epoxy Composites Enhanced Reflection Loss

Recently, various electronic devices have been developed to meet the requirements of higher frequency technology applications. This widely used application without realizing has created more electromagnetic interference pollution that is harmful to human health and other equipment. Therefore, more research interest focuses on fabricating the electromagnetic (EM) wave absorbing materials that can absorb the EM wave interference. In this regard, this research highlights the use of Iron Oxide and Cobalt Oxide as catalyst to synthesize hybrid CNT by using Thermal Vapor Deposition Tube (TVDT) method. The spiral hybrid CNT/epoxy composites were prepared at thickness of 1mm, 2mm and 3mm. The phase formation, microstructural, particle size and structural analysis of the hybrid CNT were analyzed by using X-ray diffractometer (XRD), Scanning Electron Microscope (SEM), Transmission Electron Microscope (TEM) and RAMAN spectrometer respectively. The microwave characterization of the hybrid CNT/epoxy composite samples was analyzed by using Vector Network Analyzer (VNA) at GHz frequency range. The phase analysis confirmed the existence of Carbon and iron carbide in the sample. The microstructural of CNT formation are mostly in spiral and straight like structure. On the other hand, the structural analysis shows the sample are more towards defective structure with higher and broader D-band peak. This could enhance the EM wave absorption performance. The minimum reflection loss (RL) peak was ̴-23dB (t=3mm) obtained for all hybrid CNT composite samples. The differences of minimum reflection loss peak at different weight percentages are most likely shown by the shift of frequency range. Thus, this lightweight spiral hybrid CNT/epoxy composites results in better EM wave performance at different thin thickness used for different applications.

Insitu assembly of Fe3O4@FeNi3 spherical mesoporous nanoparticles embedded on 2D reduced graphene oxide (RGO) layers as protective barrier for EMI pollution

Electromagnetic interference (EMI) is a major issue due to the increased use of electronic devices operating in the gigahertz frequency range. Consequently, to reduce electromagnetic pollution, materials with considerable magnetic and dielectric loss can be used for the attenuation of electromagnetic waves. In this paper, Fe3O4 FeNi3 spherical mesoporous nanoparticles embedded on reduced graphene oxide (RGO) layers have been synthesized using the hydrothermal reduction method. The specific surface area of Fe3O4@FeNi3/RGO nanocomposite was 67.4 m2/g with a pore size diameter of 3.4 nm (i.e., mesoporous range). Fe3O4@FeNi3/RGO nanocomposites show an enhanced absorption dominant shielding effectiveness (SE) value of 46.49 dB as compared to its binary counterpart Fe3O4@FeNi3, having SE value of 25.21 dB. The synthesized Fe3O4@FeNi3/RGO nanocomposite of thickness 1.42 mm has SER of ∼10.32 dB and SEA of ∼36.15 dB at 15 GHz. Furthermore, it is observed that shielding efficiency increases with increasing reduced graphene oxide (RGO) content in Fe3O4@FeNi3, which is owing to an excellent interconnected network between RGO and Fe3O4@FeNi3. The RGO sheets can create a comprehensive conductive network for the distribution of charges and can enhance dielectric loss because of the layered structure, greater specific surface area and large aspect ratio. Additionally, the mesoporous Fe3O4@FeNi3 hybrid embellished on the surface of RGO may be employed as a multi-pole polarisation centre, enhancing the electronic and space charge polarization of the composites, which is helpful for strong EM wave absorption. It was believed that these nanocomposites would pave the way for the development of RGO-based mesoporous nanocomposites as broadband, lightweight and effective shielding material for practical applications.

Fe/Co decorated C@CNTs derived from bimetallic metal-organic-framework for microwave absorption with wide bandwidth

It’s a hurry to introduce a lightweight and high-efficiency microwave absorption material that is easy to synthesize, since the electromagnetic interference pollution is getting increasingly serious. Carbon-based microwave absorption material based on bimetallic metal-organic frameworks (MOFs) gets high conductivity and good magnetism at the same time, and thus can be regarded as an efficient microwave absorber with lightweight. Herein, we introduce an easy method to compose bimetallic carbon-based microwave absorbers based on ZIF-67. By changing the proportion of Fe3+ and Co2+, not only the magnetism of the material can be adjusted, the amount of carbon nanotubes (CNTs) and so as the dielectric property of the material can also be regulated. The method of introducing precursors at room temperature and then calcinating at an Ar atmosphere is simple to repeat and appropriate for mass production. When the dosage molar ratio of Co2+: Fe3+ is 3: 2, the minimum reflection loss (RLmin) can reach − 24.83 dB while the effective absorption bandwidth (EAB) can reach 5.14 GHz when the thickness is 1.7 mm, under a 30 wt% filling loading. We believe that this work can provide a reliable method to introduce carbon-based microwave absorption material based on bimetallic MOF materials.

Durable cellulose paper by grafting thiol groups and controlling silver deposition for ultrahigh electromagnetic interference shielding

Electromagnetic interference (EMI) shielding paper with durability and high effectiveness is of significant importance to long-term service for preventing EMI pollution. Herein, we report a practical method for preparing cellulose paper/Ag composite with outstanding durable and ultrahigh EMI shielding performance by electroless silver plating. The silver deposition process, the surface morphology, the silver content and conductivity of the composite can be controlled by varying the amount of N-acetyl-L-cysteine (NAC) grafted onto the cellulose fibers and ammonia amount for silver-ammonia complex formation. Moreover, the grafted NAC with thiol groups on cellulose can enhance the adhesion between silver and cellulose paper, meanwhile, NAC as the reducing agent can result in a more complete flower-shaped silver structure and reducing the reflection of electromagnetic waves in silver layer. The composite exhibited excellent conductivity, EMI shielding effectiveness (SE) up to 106 dB and outstanding durability. After 10,000 bending times and 60 abrasion cycles respectively, the electrical resistance of the composite only increased from 0.030 Ω/sq. to 0.041 Ω/sq. and 0.050 Ω/sq., and the EMI SE decreased to 102 dB and 105 dB.

Effect of carbon reinforcement on the EMI shielding response of LiFe5O8 ceramics

Carbon black (CB) reinforced lithium ferrite composites (LFO/CB) are synthesized to enhance EMI (electromagnetic interference) shielding effectiveness (SE) as nowadays EMI pollution is becoming a serious matter of concern for technology as well as human health. The formation of pure phase lithium ferrite and composites are analyzed. Though saturation magnetization decreased with the incorporation of CB, it did not create any huge decrement. Shielding efficiency is analyzed in the X band (8.2–12.4 GHz) and Ku (12.4–18 GHz) band frequency range. The highest total SE (28 dB) is obtained for 20 wt% of CB with LFO (3 mm thickness), out of which reflection-based shielding effectiveness (SER) is 4.58 dB and absorption based (SEA) is 23.17 dB. The highest absorption efficiency of the composites is measured to be ~99.68% for both LFO/CB (15) and LFO/CB (20) in the broad frequency range (8.2–18 GHz), which confirmed that the composite provides absorption-based SE rather than reflection based. Both real and imaginary part of permittivity drastically increased with incorporation of CB concentration (LFO: ε’ = 4, ε“= 0.11; LFO/CB (20) : ε’ = 46, ε”= 19.05 @8.2 GHz). Complex permeability also increased with CB content. However, dielectric, magnetic, and EMI shielding responses can be tailored by governing the amount of ferrite as well as carbon compound. Further, this study confirms that LFO/CB composites can be a potential candidate for application in the defense and telecommunication sector.

Constructing hierarchical structure via in situ growth of CNT in SiO2-coated carbon foam for high-performance EMI shielding application

Carbonated melamine foam (CMF) with a three-dimensional (3D) inner connected network is considered as one of the promising candidates to fabricate electromagnetic interference (EMI) shielding materials. To further improve EMI shielding performance, CMF based hybrids with three-dimensional structure by the combination of SiO2 and in-situ growth carbon nanotubes (CNT) have been synthesized for preparing polydimethylsiloxane (PDMS) composite: CMF@SiO2-CNT/PDMS. Owing to the structural match between the length of CNT and the diameter of holes in the CMF@SiO2, the relatively high electrical conductivity of 50.43 S/m has been achieved in the composite with the thickness of 2 mm, which assures an excellent EMI shielding effectiveness (SET = 61.34 dB) in the frequency range from 8.2 to 12.4 GHz. Meanwhile, a high absorption effectiveness (SEA = 53.65 dB) of the composite infers an absorption dominant performance of the composite because of the unique porous structure and inter-connected conductive network, which helps to avoid secondary EMI pollution. We hope this work can provide a new route for fabricating EMI shielding materials with high performance.

Annealing-induced enhancement of electrical conductivity and electromagnetic interference shielding in injection-molded CNT polymer composites

Carbon nanotubes (CNTs) are of great interest to polymer scientists as reinforcements in polymer matrices to produce conductive thermoplastics. Unfortunately, their orientation distributions after the injection molding process have been found to provide low interparticle contact and electrical conductivity. In this study, we attempt to improve these characteristics in CNT-reinforced polycarbonate (PC) composites produced by injection molding using both types of CNTs, namely, single- and multi-walled carbon nanotubes (SWCNTs and MWCNTs, respectively). However, electrically conductive CNT networks were found to be re-tailored through post-processing annealing at high temperatures. For example, the conductivity of SWCNT(1 wt%)/PC was improved 1012 times with annealing. Herein, the electrical network of SWCNT-based polymer composites transformed after annealing was investigated for the first time in detail. Polarized Raman mapping clearly demonstrated the transition from aligned, unconnected CNTs before annealing to a randomly oriented interconnected network after annealing. Moreover, the annealing-induced expansion of the CNT electrical network path was directly visualized using the lock-in thermography technique, which clearly showed an increase in the degree of interconnection among CNTs in all regions of the molded parts from the skin to the core. Notably, the response of the composite to electromagnetic waves changed from absorption to reflection owing to this improved conductivity. The 3 wt% SWCNT/PC, which exhibited the highest electrical conductivity of 2.37E-01 S/cm also provided the highest electromagnetic interference (EMI) shielding effectiveness of 46.7–51.1 dB, providing its wide-ranging applicability in EMI pollution protection.

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.

3D hierarchical porous composites based on natural loofahs/cobalt nanoparticles/graphene oxide with efficient electromagnetic interference shielding performance

Using biomass carbon materials to construct the electromagnetic wave shielding system is an efficient solution for electromagnetic interference pollution. In this study, carbonized loofahs/Co nanoparticles/graphene oxide composites were prepared with a 3D hierarchical porous structure for efficient electromagnetic interference shielding by a facile and efficient thermal reduction process. The carbon matrix is inlaid with cobalt nanoparticles, promoting the graphitization of composites and the fabrication of a 3D conductive network. Simultaneously, the synergistic effect between nanoparticles and carbon matrix good electromagnetic properties, inducing the improvement in both dielectric and magnetic loss. As a result, the average shielding effectiveness and specific shielding effectiveness of composites reach 61.05 dB and 714.76 dB cm3/g within the frequency range of 12.4–18 GHz (Ku-band) separately, whose intense absorption loss and wideband response are superior to other composites based on biomass carbon. It is believed that this work may promote the application of biomass material in the field of electromagnetic shielding.

Facile synthesis of coral cauliflower‐like polypyrrole hemispheres toward screening electromagnetic interference pollution

AbstractIn this study, coral cauliflower‐like polypyrrole (PPy) hemispheres are synthesized on an alumina substrate via a simple chemical oxidative polymerization route. The stony coral‐like morphology of PPy hemispheres acts as a conducting trap in absorbing electromagnetic (EM) radiation via multiple internal reflections. A PPy thin film deposited at 0.2 M pyrrole concentration shows a minimum reflection loss (RL) of −30.80 dB (99.9% microwave absorption) at the frequency of 14.2 GHz, and the highest total shielding effectiveness achieved is −18.3 dB at 16.8 GHz at 4.38 μm film thickness. The thin films exhibit excellent microwave absorption ability at low thicknesses, and the effective absorption bandwidth (RL < –10 dB) attains a high value of 2.2 GHz in the frequency range of 13–15.2 GHz. These findings can help researchers to enhance the EM wave absorption characteristics in a broad frequency region using lightweight intrinsically conducting polymers.

Construction of compressible Polymer/MXene composite foams for high-performance absorption-dominated electromagnetic shielding with ultra-low reflectivity

The conductive polymer composite (CPC) foams are always accompanied with obvious reflection of EM waves during electromagnetic interference (EMI) shielding, and the significant reduction of EM reflection via structural design of CPC foams to minimize the secondary EMI pollution is deemed very important. Herein, for preparing designable MXene-based CPC foams with high-efficiency EMI-shielding performance and ultra-low reflectivity, novel MXene-decorated polymer foam beads (MPFBs) were fabricated to serve as building blocks by the assistance of polyaniline (PANI), and CPC foams were constructed by assembling MPFBs into 3D accumulation with MXene networks followed by the encapsulation of polydimethylsiloxane (PDMS), which presented superb EMI SE of ∼23.5–39.8 dB with only ∼0.0225–0.0449 vol% MXene (plus ∼0.02 vol% PANI), along with low R coefficient of ∼0.20–0.31. By further employing the asymmetric gradient configuration, ultra-low R coefficient of ∼0.05 was obtained with effective EMI SE of ∼23 dB at total MXene content of only ∼0.0225 vol%, which is the lowest R values for effective EMI shields ever reported. In addition, because of their remarkable compressibility, convenient SE regulation of PDMS/MPFB composite foams by mechanical compression was demonstrated, showing a function to switch between inefficient shielding of SE < 20 dB and effective shielding of SE > 20 dB.

Bifunctional carbon-encapsulated FeSiAl hybrid flakes for enhanced microwave absorption properties and analysis of corrosion resistance

Designing of materials which can resist aging and corrosion in harsh reaction conditions is required to mitigate the omnipresent issue of electromagnetic interference pollution. Particularly, FeSiAl alloy is a relevant composite material, however, it always suffers aging and corrosion when exposed to crude saline environment. Herein, Carbon-encapsulated FeSiAl (FeSiAl@C) hybrid flakes are developed by catalytic chemical vapor deposition (CCVD) technique through the reaction of FeSiAl precursor with acetylene (C2H2) gas at 300 °C for 5 min. The carbon coating efficiently improves the impedance matching characteristics of FeSiAl powder leading to enhance microwave absorption. Not only that, the carbon capsule also plays an effective shielding function to prevent the alloy from corroding. Specifically, the FeSiAl@C-300 °C delivers increased complex permeability and permittivity in the frequency range of 7–14 GHz, as well as improved impedance matching. In addition, the corrosion resistance is measured using linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) in 5 wt% NaCl solution. The results indicate that the synthesized hybrid exhibits excellent corrosion resistance capability. So, the composite synthesis is a worthy approach to design hybrid materials for effective microwave absorption and corrosion resistance properties for practical applications.

Facile One-Pot Solvothermal Synthesis of the RGO/MWCNT/Fe3O4 Hybrids for Microwave Absorption.

How to effectively regulate the electromagnetic parameters of magnetic composites to achieve better microwave absorption (MA) performances is still a serious challenge. Herein, we constructed nanocomposites composed of magnetic constituents and carbon materials to obtain high-efficiency electromagnetic wave absorbers. Self-assembled, multi-interfacial, and porous RGO/MWCNT/Fe3O4 hybrids (GMFs) were synthesized via in situ one-pot solvothermal method. The growth mechanism of the GMFs would be that the defects on reduced graphene oxide (RGO) provide sites for the crystallization of Fe3O4. Also, the RGO and Fe3O4 were further linked by the cross-connection of multiwalled carbon nanotubes (MWCNTs), which acted as a bridge. The MA mechanism of GMFs was studied while considering the synergistic effects between the three components (RGO, MWCNT, and raspberry-shaped Fe3O4) and their multi-interfacial and porous structure. Also, the MA performance of the GMFs was conducted. The GMFs exhibited a maximum reflection loss (RL) value of −61.29 dB at 10.48 GHz with a thickness of 2.6 mm when the contents of RGO and MWCNT were 6.3 and 1.3 wt %, respectively. The RL values (≤−10 dB) were observed to be in the range of 8.96–12.32 GHz, and the effective microwave absorption bandwidth was tunable from 3.52 to 18 GHz by changing the sample thickness. The results revealed that the multi-interfacial and porous structure of the GMFs is beneficial to MA performance by inducing multiscatterings. Since no toxic solvents were used, this method is environmentally friendly and has potential for large-scale production. The prepared GMFs may have a wide range of applications in MA materials against electromagnetic interference pollution.

Dramatically enhanced electromagnetic wave absorption of hierarchical CNT/Co/C fiber derived from cotton and metal-organic-framework

Lightweight, low-cost electromagnetic (EM) wave absorption materials are in urgent need, as EM interference pollution is increasingly serious. Carbon material as EM absorber has attracted ever increasing attention. However, their absorption property is still limited. Herein, we propose a very simple strategy to prepare hierarchical carbon fiber coated with Co/C nano-dodecahedron particles where CNTs were anchored (HCF@CZ-CNTs), using cotton and metal-organic-framework (MOF) as raw materials. One of MOF, ZIF-67 particles were in-situ grown onto the surface of cotton fibers. Lightweight HCF@CZ-CNTs samples were obtained by direct carbonization, the apparent density of which is only 0.0198 g/cm3. The minimum reflection loss (RLmin) of hierarchical HCF@CZ-CNTs was dramatically enhanced to −53.5 dB at 7.8 GHz, compared with pure carbonized cotton fiber (RLmin = −18.9 dB at 16 GHz). Meanwhile the effectively absorption bandwidth was also remarkably enlarged to 8.02 GHz. The excellent EM wave absorption performance is attributed to the micro-to-nano hierarchical hollow fibrous structure, as well as the synergetic effect of polarization relaxation and magnetic loss. These results illuminate a low-cost and sustainable strategy to prepare ultra-lightweight microwave absorbers with excellent EM wave absorbing ability utilizing biomass precursor and MOF.

A Comprehensive Comparison of EMI Immunity in CMOS Amplifier Topologies

This paper provides the results of a comprehensive comparison between complementary metal oxide semiconductor (CMOS) amplifiers with low susceptibility to electromagnetic interference (EMI). They represent the state-of-the-art in low EMI susceptibility design. An exhaustive scenario for EMI pollution has been considered: the injected interference can indeed directly reach the amplifier pins or can be coupled from the printed circuit board (PCB) ground. This is also a key point for evaluating the susceptibility from EMI coupled to the output pin. All of the amplifiers are re-designed in a United Microelectronics Corporation (UMC) 180 nm CMOS process in order to have a fair comparison. The topologies investigated and compared are basically derived from the Miller and the folded cascode ones, which are well-known and widely used by CMOS analog designers.

Bi-phase metallic cobalt with efficient broadband absorption in X and Ku bands

Broadband and lightweight microwave absorbers have gained considerable research interest in overcoming electromagnetic interference pollution. Here, mixture of two phase (fcc and hcp) metallic cobalt powders with broadband absorption was synthesized through solvothermal method using ethylene glycol as the reducing agent. The effect of NaOH content on the structure and morphology of the prepared Co powders is investigated by X-ray diffraction and field-emission scanning electron microscopy. Ring samples of 7.00/3.04 mm of out/inner diameter were prepared with paraffin for microwave absorption testing by vector network analyzer. It was observed that the increase of NaOH content caused a relative higher generation of hcp-Co phase and formation of irregular microspheres. The reflection loss (RL) peak and effective absorbing bandwidth (EABW, RL ≤ − 10 dB) shifted towards lower frequency when the sample thickness increased from 1.00 to 3.00 mm with EABW covering almost all the C, X and Ku bands (4–18 GHz). The bi-phase Co prepared in a low base solution exhibited enhanced microwave absorption properties. The width of largest EABW has reached 6.33 GHz covering partial Ku band and almost all the X band with optimal RL of − 56.95 dB at a sample thickness of only 1.85 mm, which is superior to EABW of Co crystals reported earlier. We proposed that such a wide EABW is due to the fact of Z values closed to 1.0 (0.8 ≤ |Z| ≤ 1.2) at almost the whole frequency range. This indicates that the prepared bi-phase Co powders are excellent microwave absorbers with large bandwidth, have good prospects.

Ultralight and Mechanically Robust Ti3C2Tx Hybrid Aerogel Reinforced by Carbon Nanotubes for Electromagnetic Interference Shielding.

Lightweight materials with high electrical conductivity and robust mechanical properties are highly desirable for electromagnetic interference (EMI) shielding in modern portable and highly integrated electronics. Herein, a three-dimensional (3D) porous Ti3C2Tx/carbon nanotube (CNT) hybrid aerogel was fabricated via a bidirectional freezing method for lightweight EMI shielding application. The synergism of the lamellar and porous structure of the MXene/CNT hybrid aerogels contributed extensively to their excellent electrical conductivity (9.43 S cm-1) and superior electromagnetic shielding effectiveness (EMI SE) value of 103.9 dB at 3 mm thickness at the X-band frequency, the latter of which is the best value reported for synthetic porous nanomaterials. The CNT reinforcement in the MXene/CNT hybrid aerogels enhanced the mechanical robustness and increased the compressional modulus by 9661% relative to that of the pristine MXene aerogel. The hybrid aerogel with high electrical conductivity, good mechanical strength, and superior EMI shielding performance is a promising material for inhibiting EMI pollution.

Characterizations of continuous carbon fiber-reinforced composites for electromagnetic interference shielding fabricated by 3D printing

With an increase in electromagnetic interference pollution, composites for electromagnetic interference shielding (EMIS) with good shielding performance and friendly processability are widely demanded. Herein, a methodology for preparing composites with controllable shielding effectiveness (SE) is proposed. Carbon fiber (CF)-reinforced polylactic acid composites were fabricated by a 3D printing process, and the SE of the composites was controlled by varying the process parameters. To systematically investigate the feasibility of the methodology, the shielding properties, processability, and mechanical properties of the composites were investigated. The results showed that the SE was controlled in the ranges of 25.1–69.9 dB, 51.1–75.6 dB, and 6.8–78.9 dB by tailoring the number of layers (2–12), hatch spacing (1.6–0.8 mm), and filling angle (90°–0°), respectively. The critical mechanism of the controllability is that the content, spatial distribution, and orientation of CFs can be facilely and digitally controlled during processing. A conformal shell with a SE of 38.5 dB was fabricated to demonstrate superior processability of a complex geometry. The maximum tensile and flexural strengths of the composites were 111.0 and 152.9 MPa, respectively, which were much larger than those of most engineering plastics. Using this methodology, an appropriate SE that is neither excessive nor deficient can be readily realized, which helps to maintain high resource utilization. Complex geometries for EMIS can be rapidly and cheaply obtained without molds, which is difficult for traditional processes. These advantages make the 3D-printed CF-reinforced composites competitive with other EMIS materials and traditional processes.

Innovations in polymer nanocomposite coatings for EMI Shielding applications

Start Excessive usage of electronic gadgets, telecommunication devices and electrical appliances has led to unwanted electromagnetic interference (EMI) as side effect. The EMI pollution interferes with the performance and functioning of the electrical equipments, which is generated through the conduction or radiation of emitted electromagnetic (EM) waves. In addition to affecting the quality of electrical appliances, EMI has a huge negative impact on the health and life of living organisms. Moreover, microwave frequency operated functions such as radar surveillance systems; weather radar, military aviation, radar guns, wireless technology and satellite communication are more prone to EMI pollution and specifically with regard to stealth purposes. In this paper carbon nanomaterial based polyurethane nanocomposites have been synthesized and investigated for decreasing the EM wave pollution due to their light weight, flexibility, optimum conductivity and good dielectric properties. Three different types of graphene sheets such as thermally reduced and exfoliated graphene (TRG); chemically reduced graphene (CRG) and Polyvinyl-pyyrolidone stabilized silver nanoparticles based graphene nanohybrid (Ag-PVP-CRG) have been synthesized and characterized for EMI shielding properties. Further, TRG, CRG and Ag-PVP- CRG sheets have been dispersed in thermoplastic polyurethane (TPU) polymeric matrix to create multifunctional nanocomposite films with properties such as EMI shielding, electrically conductivity and dielectric behavior. The study presents for the first time a comparative evaluation of three different types of graphene sheets in both neat and nanocomposite form. The synthesis of Ag-PVP-CRG nanohybrids and its application for EMI shielding is novel and reported for the first time for such an application.

Synthesis of reduced and functional graphene oxide with magnetic ionic liquid and its application as an electromagnetic-absorbing coating

The current study fabricated magnetic functional graphene oxide (MFGO) and magnetic functional reduced graphene oxide (MFRGO) by relying on FeCl4− magnetic anion confined to cationic 1-methyl imidazolium to absorb electromagnetic interference pollution. MFGO and MFRGO were characterized by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Raman spectroscopy, and field emission scanning electron microscopy. As a microwave-absorbing material, (MFGO)/epoxy resin composite was prepared using 10%–50% (wt) MFGO at thicknesses of 1–5 mm. The composites showed excellent microwave absorption in the microwave range of 8.0–12.0 GHz. The composite with 40% (wt) MFGO at 4 mm in thickness displayed several broad absorption bands. The strongest absorbing peak achieved a maximum absorption of −14.83 dB at 8.62 GHz and the maximum reflection loss was −25.21 dB at 8.62 GHz. When compared to with graphene oxide composites, both the MFGO and MFRGO composites exhibited significantly greater microwave absorption over the X band frequency range.