EMI Shielding Materials Research Articles

Exploring the Potential of Graphene as an EMI Shielding Material – An Overview

Graphene- 2D, single layered, one atom thick material has gained high importance as an electromagnetic interference shielding material due to its superior electrical property and large aspect ratio.It is an allotrope of carbon with sp2 configuration that exhibits excellent mechanical and thermal properties. Graphene have been used as electromagnetic interference shielding material in the form of ultrathin flexible film, paper, laminates, microcellular foams, sheets etc. Electromagnetic shielding efficiency of graphene can be as high as 135 dB, whereas the commercial applications requirement is only 20 dB. The present review work mainly focuses on the use of graphene as an EMI shielding materialin composites, free standing films, foams and aerogels. This study also reviews the use of different dopants to dope graphenethat can be used as EMI shielding material. Methods of production of different forms of graphene and mechanisms of EMI shielding have been briefly discussed in the current review. The study reveals that the highest EMI SE is exhibited by graphene aerogels, as high as 135 dB. The study explores the effective use of graphene as an EMI shielding material in various electronic devices. Despite possessing many superior properties, few limitations that exist to the usage of grapheme have also been listed out in this review

Highly Robust, Flexible, and Large‐Scale 3D‐Metallized Sponge for High‐Performance Electromagnetic Interference Shielding

AbstractElectromagnetic interference (EMI) is a type of pollution that is caused by the ubiquitous usage of electronic communication in general, and military radar equipment in particular. Even though this is a common problem for a long time, the fabrication of large‐area, flexible, and robust EMI shielding materials is still a challenge today. In this work, the 3D meshing strategy is simulated for most efficient utilization of metallic silver for X‐band EMI shielding, and propose a roll‐to‐roll (R2R) process to fabricate robust, flexible, and large‐scale EMI shielding sponge, silver nanowires/polyvinyl butyral (PVB) melamine sponge (AgPMS). Typically, 0.5 cm thick sponge has about 60 dB total EMI shielding efficiency (SE) in the microwave band, which is higher than for commercial EMI shielding sponges (about 45 dB) of the same thickness. AgPMS shows unchanged electrical properties after 1000 compression and bending cycles. Moreover, a AgPMS garment is made to demonstrate the excellent EMI shielding performance and remarkable flexibility of this material. Those properties suggest that AgPMS can be readily applied in challenging environments like hospitals, military installations, remote communication centers, and for any devices with curved surfaces.

Reduced Graphene Oxide Functionalized Strontium Ferrite in Poly(3,4‐ethylenedioxythiophene) Conducting Network: A High‐Performance EMI Shielding Material

AbstractThe advent of nanotechnology leading to high‐frequency device realization has resulted in a rapid increase in radiation pollution. The synthesis of core–shell morphology based poly(3,4‐ethylenedioxythiophene) (PEDOT)/ reduced graphene oxide (RGO) nanocomposites incorporated with SrFe12O19 nanoparticles via in situ emulsion polymerization is a step to control ever‐increasing radiation pollution. For electromagnetic (EM) shielding, impedance matching, and absorption of EM wave being the two key parameters. RGO and PEDOT establish an interconnected conducting network inside the PEDOT matrix and the resulting conductive pathway provides better impedance matching for the incident radiation. The RGO sheets decorated with ferrite nanoparticles strengthen the mechanism of the shielding by absorbing incoming EM radiation. The synergic coupling of the magneto‐dielectric characteristics of nanocomposites result in high electromagnetic shielding effectiveness (SE) of 42.29 dB at 12.4 GHz for 2.5 mm thick sample. The SE is mainly dominated by absorption and also measured as a function of thickness resulting in SE(max) value of 62 dB at a thickness of 4.66 mm. The present set of nanocomposites are found to exhibit attenuation of more than 99.999% and have the potential for commercial application in EM shielding.

Powerful absorbing and lightweight electromagnetic shielding CNTs/RGO composite

Combination of lightweight and superior electrical conductive performance is charming for the application of macroscopic graphene foam composite. A porous carbon nanotubes/reduced graphene oxide (CNTs/RGO) foam composite are prepared by freeze-drying and in-situ catalytic grown methods. The CNTs/RGO foam composite consists of interconnected RGO nanosheets as the 3D frame and in-situ growth CNTs as the electromagnetic wave (EM) absorbing reinforcement, which grow on graphene substrate. The in-situ grown CNTs on graphene nanosheets lead to the enhancement of conductive and polarization loss, which results in the enhancement of absorption shielding performance. The CNTs/RGO foam composites with different CNT loading are prepared to investigate their EM shielding properties in X-band. The EM shielding effectiveness (SE) of CNTs/RGO foam composite reaches 31.2 dB with 2 mm thickness, especially the specific EMI shielding effectiveness reaches 547 dB cm3/g with an ultralight density of 57 mg cm−3, the absorption is the primary shielding mechanism. Furthermore, SE value reaches 49 dB with thickness of 3.1 mm. Owing to the unique 3D foam hierarchical architecture, light density and outstanding SE performance, our work shows a promising designable approach of preparing CNTs/RGO foam composite to lightweight and absorption type EMI shielding materials.

Investigation of electrical conductivity and electromagnetic interference shielding effectiveness of preferentially distributed conductive filler in highly flexible polymer blends nanocomposites

Motivated by the impact of electromagnetic radiation on electronic gadgets and living beings, herein we developed a light weight flexible EMI shielding material to meet the demands of consistently developing technology. In the present study, we utilized the concept of preferential distribution and double percolation to fabricate a conductive polymer composite that absorbs EM radiation. We employed EMA/EOC (50/50) wt% binary blend as the polymer matrix and MWCNT as the functional filler. With the addition of 3 wt% MWCNT, the composite demonstrated a shielding efficiency of −18.66 dB and with 15 wt% MWCNT, a total shielding efficiency of −34.06 dB was attained combined with good mechanical and thermal properties. We believe this work provides an insight in developing a scalable and affordable EMI shield finding its potential in both academic and industrial application.

High Performance EMI Shielding Materials and Spraying Process Parameters for High Frequency FCBGA Application

Abstract We studied and demonstrated high-performance Ag epoxy composites. A variety of shaped Ag particles were teste to optimize the electrical properties and mechanical reliability. The resulting Ag epoxy composites containing flake-shaped Ag particles showed less than 5×10−7Ω·m electrical conductivity and about 20mΩ series-resistance of PKG daisy chain, which directly corresponded to the excellent shield effectiveness. The shield effectiveness of resulting EMI shielding layer made of Ag and matrix is as high as 60dB, 65dB, 70dB at 5um, 10um, 20um-thick film, respectively by ASTM standard. We studied that how various factors, such as curing temperature, Ag contents, and film thickness, effects the electrical properties of shielding material and FCBGA package. It was found that the resistivity of conductive shielding material and the series-resistance were affected by the curing temperature than the curing time. Additionally, we demonstrated the electrical properties of AgCu epoxy composites.

Effect of N2 flow rate on electromagnetic interference shielding effectiveness of TiNx films

TiNx films with different nitrogen contents were fabricated using direct current reactive magnetron sputtering. Influence of N2 flow rate on the resistivity and electromagnetic interference (EMI) shielding effectiveness (SE) of TiNx films was studied. The EMI SE of TiNx films was found to be related with the resistivity. With the rise of N2 flow rate, the resistivity of TiNx films increased, while the EMI SE decreased. When the N2 flow rate was 1 sccm, the EMI SE of TiNx films was over 20 dB with the thickness of 1.47 µm, which was much smaller than the thickness of the presently known EMI-shielding materials. The results indicated that TiNx films could be applied as ultrathin thickness, lightweight, and design flexibility shielding materials.

Electromagnetic interference shielding properties of graphene/MWCNT hybrid buckypaper

A type of lightweight and flexible graphene/multi-walled carbon nanotube (MWCNT) hybrid buckypaper (BP) is fabricated, which show superior shielding effectiveness (SE) of electromagnetic interference and without polymer. The EMI SE of graphene/MWCNT hybrid BP with thickness of 130 μm is up to ∼51 dB at 8 GHz, which is much higher than that of pure MWCNT BP with same thickness (∼32.5 dB) and the best electrical conductivity is up to 10,000 S/m. More important, the improvement in EMI SE is contributed to the SE absorption, while the SE reflection is almost unchanged. This paper-like material is smooth, tough, and flexible enough to be attached on the complex curved surface structure. A facile way to fully develop graphene and MWCNT in lightweight and flexible EMI shielding materials and devices is provided here.

Enhanced electromagnetic interference shielding properties of silicon carbide composites with aligned graphene nanoplatelets

Graphene nanoplatelets (GNPs) were successfully incorporated into silicon carbide (SiC) ceramic matrix in a self-aligned pattern and the obtained materials displayed extremely high value of shielding effectiveness (SE) over 40 dB by adding only 3 wt.% GNPs, which was the highest SE value in all SiC-based composites reported in literature up to now. It was found that the texture distribution of GNPs was crucial to achieve the high electromagnetic interference shielding performance of SiC/GNPs composites, which can contribute to the significant improvement of both absorption and reflection. The improved absorption originated from the formation of network of mini capacitors comprised of self-aligned GNPs and multiple reflections. The improvement of reflection was attributed to the high electrical conductivity of the composite due to the introduction of GNPs. These results indicate that SiC/GNPs composites can be used as high-performance ceramic-based EMI shielding materials.

Synthesis of MoS2-reduced graphene oxide/Fe3O4 nanocomposite for enhanced electromagnetic interference shielding effectiveness

This article presents a facile two step hydrothermal process for the synthesis of MoS2-reduced graphene oxide/Fe3O4 (MoS2-rGO/Fe3O4) nanocomposite and its application as an excellent electromagnetic interference shielding material. Characterization tools like; scanning electron microscope, transmission electron microscope, x-ray diffraction, and Raman spectroscopy were used to confirm the formation of nanocomposite and found that spherical Fe3O4 nanoparticles are well dispersed over MoS2-rGO composite with average particle size ∼25–30 nm was confirmed by TEM. Structural characterization done by XRD was found inconsistent with the known lattice parameter of MoS2 nanosheet, reduced graphene oxide and Fe3O4 nanoparticles. Electromagnetic shielding effectiveness of MoS2-rGO/Fe3O4 nanocomposite was evaluated and found to be an excellent EMI shielding material in X-band range (8.0–12.0 GHz). MoS2-rGO composite shows poor shielding capacity (SET ∼ 3.81 dB) in entire range as compared to MoS2-rGO/Fe3O4 nanocomposite (SET ∼ 8.27 dB). It is due to interfacial polarization in the presence of EM field. The result indicates that MoS2-rGO/Fe3O4 nanocomposite provide a new stage for the next generation in high-performance EM wave absorption and EMI shielding effectiveness.

Ultra-light weight, water durable and flexible highly electrical conductive polyurethane foam for superior electromagnetic interference shielding materials

An inexpensive light weight radiation shielding materials have been fabricated by one step, facile technique avoiding toxic volatile organic solvents. Herein, we adopted ‘dip coating and drying’ method to prepare high surface area specialty conductive black (Ketjen-600JD) loaded polyurethane (PU) composite foam. The non-ionic surfactant stabilized black particles showed promising improvement in electrical conductivity (exceptionally low percolation threshold concentration) and water durability. The morphological analysis from electron microscopy and 3D micro computed tomography supports uniform conducting pathway formation on to the cell walls of the cellular PU system. The PU foam surprisingly showed no severe drop of porosity even after dipping in high carbon black dispersion. This efficiently supports the micro structural integrity of the foam composites which has been normally retained as the pristine foam. The EMI shielding value of the composite foam for only 2 wt% carbon black shows 65.6 dB which is amazingly high for other reported values till date. This can be said that the prepared conducting foam is suitable alternative for low cost durable EMI shielding material.

Highly flexible and ultra-thin Ni-plated carbon-fabric/polycarbonate film for enhanced electromagnetic interference shielding

We report in this work a highly flexible, mechanically robust, and ultra-thin Ni-plated nonwoven carbon fabric/polycarbonate (CF/PC/Ni) film that exhibits outstanding electromagnetic interface (EMI) shielding performance. This composite film is fabricated through a four-step process — fabrication of nonwoven carbon fiber/polypropylene/polyethylene (CEF-NF) fabric, catalytic seeding and sensitization, electroless Ni plating, and lamination with polycarbonate. The as-fabricated ultra-thin (0.31 mm) CF/PC/Ni film exhibits superior EMI shielding effectiveness (EMI-SE) of 72.7 dB, which is close to 3× that of an identical film with no Ni plating (25 dB)—demonstrating Ni plating can substantially improve the EMI shielding performance. Compared with similar lightweight EMI-shielding materials, this CF/PC/Ni film shows a superior EMI-SE at lower density and smaller thickness (1376.1 dB cm2 g−1). 40 min of Ni plating (yielding a Ni thickness of 1.075 μm), followed by 2 MPa of laminating pressure at 190 °C of laminating temperature were found to provide optimal EMI shielding performance. Based on reliability study, the CF/PC/Ni film retains 96.36% of its EMI-SE after 5000 cycles of mechanical bending and 50 h of heating. Therefore, the CF/PC/Ni film exhibits outstanding flexibility, good mechanical strength, and remarkable electrical properties, making it an excellent EMI shielding material.

An effective EMI shielding material based on poly(trimethylene terephthalate) blend nanocomposites with multiwalled carbon nanotubes

The effects of blend ratio and MWCNT loading on the morphology, electrical properties and electromagnetic shielding performance of poly(trimethylene terephthalate) (PTT)/polypropylene (PP) blend nanocomposites were studied.

Correction: An effective EMI shielding material based on poly(trimethylene terephthalate) blend nanocomposites with multiwalled carbon nanotubes

Correction for ‘An effective EMI shielding material based on poly(trimethylene terephthalate) blend nanocomposites with multiwalled carbon nanotubes’ by Ajitha A. R et al., New J. Chem., 2018, 42, 13915–13926.

To study the effect of MWCNT incorporated into PVDF-Graphite composites for EMI shielding applications

Present work reports the fabrication of EMI shielding composites consisting of multi-walled carbon nanotubes (MWNTs) and graphite uniformly dispersed in an insulating polymer matrix i.e. polyvinylidene fluoride (PVDF). The EMI shielding is measured in the X-band frequency range (8–12 GHz) for all the composites. Absorption and reflection radiations are seen to be increasing with increasing the graphite and MWCNT level in the composite and a high EMI shielding effectiveness (SE) value of 14.64 dB has been achieved. The results are promising for the development of a novel, low cost, light weight, and flexible EMI shielding material.

Simultaneously improved electromagnetic interference shielding and mechanical performance of segregated carbon nanotube/polypropylene composite via solid phase molding

Conductive polymer composite with segregated structure has been well demonstrated to achieve high electromagnetic interference shielding effectiveness (EMI SE) due to the selectively distributed electrical nanofillers to establish desirable conductive networks. Nevertheless, the formation of segregated structure in low-melt-viscosity semi-crystalline polymer is still challenged and the segregated composite always suffers poor mechanical performance. Herein, elevated pressure and temperature were utilized to make a typical semi-crystalline polymer, polypropylene (PP), hold solid phase to restrict the diffusion of carbon nanotube (CNT) into its interior. Segregated CNT networks were facilely constructed in the resultant CNT/PP composite and imparted it with a superior EMI SE of 48.3 dB at 2.2 mm thickness and 5.0 wt% CNT loading, the highest EMI shielding level among the reported CNT/polymer composites at equivalent material thickness and CNT loading. Moreover, the elevated pressure and temperature effect dramatically increase the compressive, tensile, and flexural strength (modulus) of the CNT/PP composite by 133% (65%), 74% (130%) and 53% (50%), respectively, in comparison to those for conventional segregated CNT/PP composite, really overcoming the major mechanical shortcoming in the development of segregated composites for EMI shielding. Our work provides a facile strategy to fabricate the efficient EMI shielding and robust material with the construction of typical segregated structure in low-melt-viscosity semi-crystalline polymers.

Chemically Synthesized Ag/PPy-PVA Polymer Nanocomposite Films As Potential EMI Shielding Material In X-band

Chemically Synthesized Ag/PPy-PVA Polymer Nanocomposite Films As Potential EMI Shielding Material In X-band

China: Cabot – research centre for carbon black, plastics masterbatch & fumed silica

Conductive wood plastic composites (WPCs) take advantages of high mechanical strength, stability, low density and conductivity, are promising candidates as functional electromagnetic shielding materials. Thus, conductive SS-PE-CBx composites were prepared using agricultural sorghum straw residues (SS), high-density polyethylene (HDPE) and carbon black (CB) nanoparticles. With the help of rigid and conductive CB nanoparticles, SS-PE-CBx composites displayed enhanced mechanical properties, thermal stability and conductivity (0.4 S/cm), showed high EMI shielding capabilities (a maximum total EMI value of ~ 22.5 dB), which were favorable for practical applications. This work may pave a new and green way to recycle agriculture wastes into functional EMI shielding materials.

Role of Enhanced Hydrogen Bonding of Selectively Reduced Graphite Oxide in Fabrication of Poly(vinyl alcohol) Nanocomposites in Water as EMI Shielding Material

According to the available literature, hydrophobic nature of graphene restricts the fabrication of its polymer nanocomposites in aqueous medium without its modification or through in situ synthesis from graphite oxide. In view of this, present work reports on fabrication of nanocomposites of poly(vinyl alcohol) filled with selectively reduced graphite oxide (SRGO) in aqueous medium. FTIR study establishes the formation of nanocomposites through enhanced intermolecular hydrogen bonded network between −OH (PVA) and surplus −OH functionalities of graphene sheet in SRGO in comparison to that derived from PVA/graphite oxide (GO). PVA/SRGO-0.2 nanocomposite showed maximum improvements in tensile strength (127%), elongation at break (25%) and thermal stability (45 °C) compared to neat PVA. This is ascribed to better dispersion and presence of extensive intermolecular hydrogen bonding between PVA and SRGO. All PVA/SRGO nanocompopsites exhibited relatively higher glass transition temperature (Tg), melting temperat...

Synthesis and Characterization of Advanced Red Mud and MWCNTs Based EMI Shielding Material via Ceramic Processing

For the first time in the world advanced multi layered Red Mud and MWCNTs (ARMC) based EMI shielding material has been developed at CSIR-AMPRI, Bhopal. Red mud provides oxides of titanium and iron as precursor and the MWCNTs provides electrical conductivity characteristics necessary for making desired EMI shielding materials. The novel process involves unique designing of chemical compositions and mineralogical phases of red mud, MWCNTs together with appropriate additive and solvent which results in the simultaneous and synergistic chemical reactions among various constituents thereby forming tailored precursor powder. Further, the ceramic processing of tailored precursor powder in appropriate environment enables formation of advanced ARMC shielding material having a variety of ceramic phases with multi elemental compositions and multi layered crystal structures. The synthesized material was characterized by various techniques namely XRD, PL, FESEM, EDXA. The reflection loss (R. L.) of the sample was calculated based on the measured complex permittivity and permeability. The advanced ARMC material with thickness t = 1.5 mm showed a minimum R. L. of -35.5 Db at 14.0 GHz with a response band width of 1.8 GHz. Thus, the developed advanced ARMC material acts as a good EMI wave absorber.