High EMI SE Research Articles

An analysis of effect of water hyacinth carbonization temperature on fabrication and EMI shielding radar

The need to increase the ability of water hyacinth composites as EMI radar protection is related to the carbonization process of organic materials. This research aimed to determine the effect of water hyacinth carbonization temperature on the effectiveness of fabrication and EMI shielding radar. The research method includes the preparations such as cutting, washing, and drying the water hyacinth. The drying process is carried out using an oven with a temperature of 70 °C for 4 days. Then the water hyacinth is mashed until it reaches the 80 mesh size. Then the carbonization process is carried out, with variations in carbonization temperature ranging from 500 °C, 600 °C, 700 °C, 800 °C, 900 °C and 1,000 °C, with a heat increase speed of 3 °C/minutes. After reaching the specified temperature, a holding time is then carried out for 1 hour. Furthermore, the composite composition of 30 % water hyacinth activated carbon powder and 70 % phenol-formaldehyde (PF) resin was molded using a hot press with a pressure of 300 kg/cm2 at 180 °C for 10 minutes. The results showed that the water hyacinth composite could be used as an EMI protection material at the X-Band frequency (8–12.5 GHz). Where the electrical conductivity and EMI SE increases with increasing carbonization temperature. Water hyacinth composites at a carbonization temperature of 1,000 °C showed the highest electrical conductivity and the highest EMI SE, respectively 4.64∙10-2 S/cm and 41.15 dB (attenuation 99.99 %) at a frequency of 8 GHz. The high absorption contribution is associated with the synergy combination of KCl and the pore structure of the goitre. KCl contributes to the magnetic properties and pore structure with high electrical conductivity values

Poly(vinylidene fluoride‐co‐hexafluorpropylene)/polyaniline conductive blends: Effect of the mixing procedure on the electrical properties and electromagnetic interference shielding effectiveness

AbstractPoly(vinylidene fluoride‐co‐hexafluoropropylene)/polyaniline (PVDF‐co‐HFP/PAni) conductive blends were prepared by two methodologies involving the in situ polymerization in two different media and dry blending approach using ball milling. Dodecylbenzenesulfonic acid (DBSA) was used both as surfactant and as protonating agent in PAni synthesis. X‐ray diffraction (XRD), scanning electron microscopy (SEM), ultraviolet–visible (UV–Vis) spectroscopy, and thermogravimetric analysis were used for characterizing the blends. PAni and PVDF/PAni prepared by in situ polymerization in H2O/toluene medium exhibited superior electrical conductivity, higher thermal stability and significantly higher electromagnetic interference shielding effectiveness (EMI SE) than those prepared in H2O/dimethylformamide (DMF) medium. PVDF/PAni with high‐PAni content (>40%) prepared by the dry blend approach presented higher conductivity and EMI SE than those prepared by in situ polymerization. The molding temperature exerted significant influence on the conductivity and EMI SE for the blend containing higher amount of PAni. The free‐solvent dry blending approach using ball milling presented similar conductivity value but the higher EMI SE when compared with in situ polymerization, and is considered environmentally and technologically interesting.

Electromagnetic interference shielding effectiveness of sol-gel coating on Cu-plated fabrics

In this work, we developed the electromagnetic shielding effective (EMI SE) polyester woven fabrics by simple electroless plating with copper. Subsequently, it was coated with various precursors to investigate their influence on the EMI SE values. In addition, we studied the effect of copper sulfate concentration and the number of dips required to improve the EMI SE values. The results of the experiment confirm that the Cu particle deposition on the fabric has a strong influence on the EMI SE values. EMI shielding is directly proportional to the concentration of copper particles as well as the sol-gel coating process. However, the EMI SE value of sol-gel coated Cu-plated fabric depends on the type of precursor. Among the precursors, Triethoxyphenylsilane provides two times higher EMI SE values than the Cu-plated fabrics which is a novel effect. The morphology of deposited copper particles was studied by employing SEM analysis in order to find the durability of copper particles on the polyester fabric surface. It was observed that the copper particles that are coated on the fabric pores have no significant decrease in air permeability due to partial coverage.

Ultra-fast heat dissipating aerogels derived from polyaniline anchored cellulose nanofibers as sustainable microwave absorbers

Electromagnetic (EM) pollution is ubiquitous and has soared to a great extent in the past few decades. The use of plant sourced cellulose nanofibers to fabricate sustainable and high performance electromagnetic shielding materials is foreseen as a green solution by the electronics industry to address this unseen pollutant. In this view, we report a facile and environmentally benign strategy to synthesize ultra-light and highly conductive aerogels derived from cellulose nanofibers (CNF) decorated with polyaniline (PANI) via a simple in-situ polymerization and subsequent freeze drying process devoid of any volatile organic solvents. The obtained conductive aerogels exhibited density as low as 0.01925 g/cc with a maximum EMI shielding value −32 dB in X band region. These porous shields demonstrated strong microwave absorption behavior (95 %) with minimal reflection (5 %) coupled with high specific EMI SE value ∼1667 dB.cm3. g−1 which make these aerogels a potential candidate for use in telecommunication, military and defense applications.

Achieving improved electromagnetic interference shielding performance and balanced mechanical properties in polyketone nanocomposites via a composite MWCNTs carrier

A simple and scalable melt compounding strategy is reported to prepare polyketone (POK) nanocomposites with high electrical, dielectric, EMI SE and excellent mechanical properties using poly(vinylidene fluoride) (PVDF) as a carrier of MWCNTs based on the selective distribution and migration of MWCNTs in POK/PVDF blend. The electrical percolation threshold of the POK/PVDF/MWCNT nanocomposites is only a half of that of POK/MWCNT composites due to the homogeneous dispersion of MWCNTs and the double percolation network. The enhanced dielectric performance originates from the interfacial polarization and numerous microcapacitors comprised of MWCNTs within the polymer. The EMI SE performance of the nanocomposites is significantly enhanced due to the selective localization of MWCNTs in the POK phase which provides high conductivity and heterogeneous dielectric media with multiple interfaces. Thus, this study provides possibilities to realize a high-performance polymer nanocomposites and a wider EMI shielding application potentials for POK materials via a composite MWCNTs carrier.

Exploring the Potential Use of Clean Scrap PVDF as Matrix for Conductive Composites Based on Graphite, Carbon Black and Hybrids: Electromagnetic Interference Shielding Effectiveness (EMI SE)

Clean polyvinylidene fluoride scrap (rPVDF) from flexible oil pipelines was used as a matrix for the development of cost effective conductive composites. Carbon black (CB), expanded graphite (EG) and mixtures of both fillers were mixed with rPVDF in different compositions by melt processing. The influence of the conductive fillers on the electromagnetic interference shielding effectiveness (EMI SE) and microwave absorbing properties in the frequency range of X-band (8–12 GHz) was also investigated. Higher EMI SE was observed for the composite prepared with CB due to the higher conductivity. However, a synergistic effect was observed in both electrical conductivity and EM attenuation by reflection (reflection loss) by using hybrid materials. For composites containing 5 wt% of filler, that loaded with EG/CB (2:3 wt%) hybrid filler displayed higher attenuation of the EM (around 97%) at a frequency of 12.3 GHz. Increasing the CB in the hybrid, decrease the EM attenuation but the efficiency was observed in a broadband range, which is very important for stealth technology purpose. The influence of the fillers on the electrical, morphological and rheological properties of the composites was evaluated. Composite loaded with 7 wt% of the hybrid filler (EG/CB = 2:5 wt%) presented higher conductivity than that containing 7.5 wt% of CB but significantly lower viscosity, indicating outstanding processability. From scanning electron microscopy (SEM), it was possible to infer that the presence of CB in the hybrid promoted a better dispersion of EG, thus favoring the formation of the conducting pathway.

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

Controllable fabrication of elastomeric and porous graphene films with superior foldable behavior and excellent electromagnetic interference shielding performance

Materials possessing ultrathin, lightweight and foldable characteristics while simultaneously exhibiting superb electromagnetic interference shielding effectiveness (EMI SE) are urgently required to guarantee the operation of portable electronics. Herein, a novel and facile approach is reported to controllably fabricate porous graphene films (PGFs) with chosen thickness by reduction-induced foaming of graphene oxide film with a spatial confinement strategy. In striking contrast to unconstrainedly expanded graphene films, the confined PGFs surprisingly exhibit excellent elastomeric behavior and strong repeated folding stability. Even after high and ultralow temperature treatment, the folding performance of PGFs is not compromised. Intriguingly, considerably enhanced EMI SE and microwave-absorbing phenomenon are achieved for PGFs compared to compact graphene films due to the efficient wave attenuation in the porous structure and highly conductive network. Significantly, the annealed PGFs exhibit a remarkably high EMI SE of 63.0 dB, enough to block and absorb 99.99995% of the incident radiation, which is far superior in performance compared to all graphene-based shielding materials. The largest specific SE/thickness of 49750 dB cm2 g−1 is among the highest values of all the shields known to date. Therefore, such thin, lightweight, elastic PGFs with outstanding EMI-shielding performance are highly promising for applications in foldable and wearable electronics.

Effect of electroless nickel plating on electromagnetic interference shielding effectiveness of pitch-based carbon papers/epoxy composites

To develop high-quality electromagnetic interference shielding efficiency (EMI SE) materials, nickel-pitch-based carbon papers (Ni-PCPs) were prepared using an electroless nickel-plating method and a wet-laid process to obtain Ni-PCPs/epoxy composites with enhanced EMI SE. The morphologies and structural properties of Ni-PCPs were determined using scanning electron microscopy and x-ray diffraction. It was found that the intensity of the metallic Ni peak increased with increasing Ni-plating time. In the frequency range of the electromagnetic waves from electrical appliances (0.5–1.0 GHz), the 5Ni-PCPs/epoxy composites of 0.25 mm thickness exhibited high EMI SE. The EMI SE of the composites was measured according to ASTM D4935-99 and increased in proportion to the current density because of the role of Ni particles. This result implies that the presence of Ni on the pitch-based carbon fibers can lead to good EMI SE, owing to the EMI adsorption behaviors of the metal particles.

Ceramic based multi walled carbon nanotubes composites for highly efficient electromagnetic interference shielding

In this work, for the first time a highly conductive ceramic composite was made by incorporating multi-walled carbon nanotubes (MWCNT) in aluminum (Al)/alumina (Al2O3) matrix by a simple mechanical mixing technique. The different weight percentage (wt%) of MWCNT incorporated with Al/Al2O3 and their role on the electrical and electromagnetic interference shielding effectiveness (EMI SE) of ceramic composites were investigated. The high electrical conductivity of 280 S/m was achieved for MWCNT@Al/Al2O3 composites with 8 wt% MWCNT content which is 280 times higher than MWCNT@Al/Al2O3 composites (1 S/m) with 1 wt% MWCNT. In addition, MWCNT@Al/Al2O3 sample showed a high EMI SE value of 46 dB for the X-band which is capable to block more than 99.9% of incident electromagnetic radiation. The high electrical conductivity and EMI SE properties of MWCNTs embedded ceramic composite system has originated from the homogenous distribution of conducting carbon nanotubes to form a percolated network at low filler loading. This work presents a strategy to develop a conductive ceramic composites for the excellent EMI shielding and electrical properties by a simple mechanical mixing approach.

Ultrahigh Conductive Copper/Large Flake Size Graphene Heterostructure Thin-Film with Remarkable Electromagnetic Interference Shielding Effectiveness.

To guarantee the normal operation of next generation portable electronics and wearable devices, together with avoiding electromagnetic wave pollution, it is urgent to find a material possessing flexibility, ultrahigh conductive, and superb electromagnetic interference shielding effectiveness (EMI SE) simultaneously. In this work, inspired by a building bricks toy with the interlock system, we design and fabricate a copper/large flake size graphene (Cu/LG) composite thin film (≈8.8 μm) in the light of high temperature annealing of a large flake size graphene oxide film followed by magnetron sputtering of copper. The obtained Cu/LG thin-film shows ultrahigh thermal conductivity of over 1932.73 (±63.07) W m-1 K-1 and excellent electrical conductivity of 5.88 (±0.29) × 106 S m-1 . Significantly, it also exhibits a remarkably high EMI SE of over 52 dB at the frequency of 1-18 GHz. The largest EMI SE value of 63.29 dB, accorded at 1 GHz, is enough to obstruct and absorb 99.99995% of incident radiation. To the best of knowledge, this is the highest EMI SE performance reported so far in such thin thickness of graphene-based materials. These outstanding properties make Cu/LG film a promising alternative building block for power electronics, microprocessors, and flexible electronics.

A particular interfacial strategy in PVDF/OBC/MWCNT nanocomposites for high dielectric performance and electromagnetic interference shielding

Multi-walled carbon nanotubes (MWCNTs) were easily dispersed at the interface of polyvinylidene difluoride (PVDF) and ethylene-α-octene block copolymer (OBC) blend by melt compounding and the nanocomposites exhibited enhanced dielectric performance, electromagnetic interference shielding effectiveness (EMI SE) and balanced mechanical performance. Through the simple, efficient and scalable interfacial strategy to disperse MWCNTs at the interface of PVDF and OBC phases, the accumulation of charge carriers at the interfaces and strong interfacial polarization effect can be achieved. At low frequency, PVDF/OBC/MWNCT nanocomposite exhibits high dielectric permittivity (753.8) and low dielectric loss tangent (0.8), offering great potential in energy storage applications. Simultaneously, in X-band range, PVDF/OBC/MWNCT nanocomposite shows high EMI SE of around 34 dB which is higher than the industrial requirement when the content of MWCNTs is as low as 2.7 vol.%. This study provides possibilities to realize high-performance polymer nanocomposites via the particular interfacial structure through one-step melt processing.

Salt leached viable porous Fe3O4 decorated polyaniline – SWCNH/PVDF composite spectacles as an admirable electromagnetic shielding efficiency in extended Ku-band region

Abstract This study describes the preparation of porous poly(vinylidene fluoride) (PVDF)/(ferrosoferric oxide (Fe3O4) decorated polyaniline/single wall carbon nanohorn (SWCNH)) PFC composite through a simple solution blending process using pre-synthesized PFC composite prepared by the in-situ oxidative polymerization of aniline in the presence of SWCNH with FeCl3 as oxidant (also used as the Fe source in the synthesis of Fe3O4) for highly efficient electromagnetic shielding application with high absorption capability. PFC was homogeneously dispersed in the PVDF matrix as conductive nanofiller to develop the conducting network and the porous morphology in the composite was achieved by leaching out of the salt (NaCl) added during solution blending process. The composite shows an excellent EMI shielding effectiveness (EMI SE) due to its porous structure and presence of continuous conductive network (polyaniline-SWCNH) and ferromagnetic Fe3O4 nanoparticles. Moreover, the highly conductive (∼2.5 × 10−2 S cm−1) PVDF-PFC composite (2 mm thickness) has greater dielectric loss and permeability property with a high EMI SE value (≈−29.7 dB) at very low loading (10 wt %) of PFC and SWCNH (1 wt%) in extended Ku-band region. The microwave absorption value also exceeds the reflection as the incident microwaves reflected and scattered multiple times internally and dissipated by the conductive 3D network of SWCNH and polyaniline throughout the composite pore wall.

Preparation and Performance of PVC/CNT Nanocomposite

ABSTRACTThe PVC/CNT nanocomposite was prepared with commercial poly(vinyl chloride) (PVC) beads and multiwall carbon nanotube (CNT). The comparative values of the electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity of PVC/CNT nanocomposite in the presence and absence of PVC beads were described. The results showed that the EMI SE values and electrical conductivity values of PVC/CNT nanocomposite had increased compared to those without PVC beads. After the addition of PVC beads, both values of the EMI SE and electrical conductivity had also increased with the increasing of the amount of PVC bead on the PVC/CNT nanocomposite, and the PVC/CNT nanocomposite in the presence of PVC bead showed high EMI SE value (22.6 dB at 4.0 wt% CNT loading in the presence of 70 wt% bead) and high conductivity value (5.31×10−2S cm−1 at 1.0 wt% CNT loading in the presence of 70 wt% bead) at low CNT loading. Thus, PVC beads effectively play a major role in enhancing the EMI SE value and electrical conductivity value of the nanocomposite. To check the bead region and solvent‐dried CNT region in the nanocomposite, morphological studies have been done and morphological studies of the PVC/CNT nanocomposite supported the two‐phase regions in the composite and the selective dispersion of the CNT in the solvent‐dried phase has been clearly observed.

A facile method to improving the electromagnetic interference shielding of a free-standing and foldable carbon nanotube mat

Free-standing and foldable CNT mats with high saturation magnetization and low electrical resistance were prepared, and a high EMI SE of 40.4–60.3 dB can be achieved at frequency ranges of 1 GHz to 18 GHz with a low mat thickness of 1.0 μm.

Polymer composites made of multi-walled carbon nanotubes and graphene nano-sheets: Effects of sandwich structures on their electromagnetic interference shielding effectiveness

This study proposes producing polymer composites with a sandwich structure. The surface layers are identical with two alternative interlayers. The surface layers are composites that are composed of polypropylene and multi-walled carbon nanotubes. Interlayers are polyvinyl alcohol (PVA)/MWCNTs composites and PVA/graphene nano-sheets composites. Maleic anhydride grafted polypropylene (PP-g-MA) serves as the coupling agent for the surface layers and the interlayer, in order to create sandwich-structured composites. The polymer composites that are constructed with different combinations are then evaluated for electromagnetic interference shielding effectiveness (EMI SE). The test results show that the incorporation of PP-g-MA reinforces the interfacial adhesion between the sandwich-structured composites, and thereby fortifies their tensile strength. When consisting of a PVA/MWCNTs interlayer, the polymer composites have an optimal electrical conductivity of 5.8 S/cm, and EMI SE of −28.60 dB for 0.0003GHz–1 GHz, −32.89 dB for 1 GHz–2 GHz, and −33.52 dB for 2 GHz–3 GHz. The sandwich-structured polymer composites that have good mechanical properties, good flexibility and high EMI SE can be achieved by using a simple and effective manufacturing method.

Carbon nanohorn and graphene nanoplate based polystyrene nanocomposites for superior electromagnetic interference shielding applications

ABSTRACTIn this article is reported the preparation of carbon nanohorn (CNH)/graphene nanoplates (GNP)/polystyrene (PS) nanocomposites through in‐situ bulk polymerization of styrene monomer in the presence of CNH, followed by the addition of suspension polymerized GNP/PS bead during polymerization of styrene, as next‐generation multifunctional material for high electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) applications. Morphological analysis revealed selective dispersion of CNH in bulk polymerized PS matrix, where GNP/PS beads were randomly distributed. The formation of continuous CNH–CNH conductive path and GNP–CNH–GNP or CNH–GNP–CNH conductive network throughout the PS matrix at exceptionally low loading of CNH (1.0 wt %) and GNP (0.15 wt %) leads to high electrical conductivity (6.24 × 10−2 S cm−1) and EMI SE ∼(−24.83 dB) when the nanocomposites was prepared in the presence of 75 wt % GNP/PS bead. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42803.

High electromagnetic interference shielding with high electrical conductivity through selective dispersion of multiwall carbon nanotube in poly (ε‐caprolactone)/MWCNT composites

ABSTRACTThis study presents the preparation of electrically conducting poly(ε‐caprolactone) (PCL)/multiwall carbon nanotube (MWCNT) composites with very low percolation threshold (pc). The method involves solution blending of PCL and MWCNT in the presence of commercial PCL beads. The PCL beads were added into high viscous PCL/MWCNT mixture during evaporation of solvent. Here, the used commercial PCL polymer beads act as an ‘excluded volume’ in the solution blended PCL/MWCNT region. Thus, the effective concentration of the MWCNT dramatically increases in the solution blended region and a strong interconnected continuous conductive network path of CNT−CNT is assumed throughout the matrix phase with the addition of PCL bead which plays a crucial role to improve the electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity at very low MWCNT loading. Thus, high EMI SE value (∼23.8 dB) was achieved at low MWCNT loading (1.8 wt %) in the presence of 70 wt % PCL bead and the high electrical conductivity of ∼2.49×10−2 S cm−1 was achieved at very low MWCNT loading (∼0.15 wt %) with 70 wt % PCL bead content in the composites. The electrical conductivity gradually increased with increasing the PCL bead concentration, as well as, MWCNT loading in the composites. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015, 132, 42161.

Electromagnetic interference shielding effectiveness of invisible metal-mesh prepared by electrohydrodynamic jet printing

EMI shielding metal-mesh pattern was prepared on the plastic film by electrohydrodynamic (EHD) jet printing with Ag ink. The printed Ag line width in the mesh was 9.72 µm which was small enough not to be distinctly detected by human eyes. The line-to-line spacing (pitch) in the mesh pattern was modulated in order to investigate the electrical and optical properties of the EHD jet-printed metal-mesh layers. The pitch of 300 µm in the mesh led to the sheet resistance of 7 Ω/sq, the transmittance of 88.2%, and the haze less than 1%. Even though the decrease in the pitch resulted in the improvement on the electrical property of the metal-mesh layer, it was found that the decrease in the pitch simultaneously degraded the optical property such as transparency and haze. Electromagnetic interference shielding effectiveness (EMI SE) of the EHD jet-printed metal-mesh was investigated over the X-band frequency range (8–12 GHz). It turned out that the EHD jet-printed metal-mesh showed a high EMI SE of 20 dB which indicated that the mesh layer can be used in the various application of electronics for the EMI shielding purpose.

A strategy to achieve high electromagnetic interference shielding and ultra low percolation in multiwall carbon nanotube–polycarbonate composites through selective localization of carbon nanotubes

Here, we report a simple method that involves solution blending of polycarbonate (PC) in the presence of multiwall carbon nanotubes (MWCNTs) and commercial PC beads for the preparation of electrically conducting MWCNT–PC composites with high electromagnetic interference shielding effectiveness (EMI SE) and electrical conductivity at very low (∼0.021 wt%) percolation threshold (pc). Thus, electrical conductivity of ∼4.57 × 10−3 S cm−1 was achieved in the MWCNT–PC composites at an extremely low MWCNT loading (0.10 wt%) in the presence of 70 wt% PC beads in the composites. Finally, optimizing the ratio of PC beads and MWCNT loading in the composites, a very high EMI SE value (∼23.1 dB) was achieved at low loading (2 wt%) of MWCNT with 70 wt% PC beads. The effective concentration of MWCNT increases in the solution blended PC region with increasing the amount of PC beads. Thus, a strong interconnected conductive network structure of CNT–CNT is developed throughout the matrix and the presence of strong π–π interaction among the electron-rich phenyl rings of PC and MWCNT in the composites plays a crucial role in increasing the EMI shielding value and electrical conductivity of the MWCNT–PC composites.