Broadband Electromagnetic Interference Shielding Research Articles

Improved broadband electromagnetic interference shielding and strain sensing properties of multifunctional reduced graphene oxide/iron–cobalt ferrite composites

Improved broadband electromagnetic interference shielding and strain sensing properties of multifunctional reduced graphene oxide/iron–cobalt ferrite composites

Highly tunable rGO composites for EMI shielding inks: A tailored approach to modulate broadband EMI shielding

In this study, we demonstrate the ability to design tunable electromagnetic interference (EMI) shielding by controlling the dominant shielding mechanism, whether it is absorption or reflection, using graphene-based nanocomposites. We synthesized four different composites and their corresponding acrylic- based inks to investigate the impact of additives on the EMI shielding mechanism. We conducted measurements on both liquid and printable structures, and the results were highly promising. The coatings exhibited a maximum shielding efficiency of over 200 dB/mm. To achieve targeted shielding for specific frequency bands (here 10 GHz), we tested metastructures printed with the synthesized inks for their shielding effectiveness. Remarkably, these structures, when screen printed on flexible and transparent polyvinyl chloride substrate, achieved over 90% microwave attenuation. Overall, this research highlights the potential of printable EMI shielding solutions, enabled by graphene-based nanocomposites, to effectively address microwave interference issues in a wide range of electronic devices and defence applications.

Recent advancements in carbonaceous nanomaterials for multifunctional broadband electromagnetic interference shielding and wearable devices

The ever-increasing proliferation of 5G wireless communication technologies and modern electronics gadgets raises concerns about electromagnetic pollution. Among the myriad e-pollution, electromagnetic interference (EMI) is a recently emphasized realm with much more implications. It affects the performance including malfunctioning and has negative impact on organisms and ecosystems. Therefore, multi-functional EMI shielding materials are essential for minimizing electromagnetic pollution and protecting human beings as well as the nearby devices or systems. In this regard, carbonaceous materials are considered as promising for efficient EMI shielding and microwave absorber due to their synergistic loss mechanism as well as the tunable architecture design. Recent progress revealed that there is significant attention in the construction of carbonaceous material with a unique multiple-interface (i.e. multi-layer, core-shell) framework. More impressively, the multilayer strategic approach is able to relocate the EMI shielding mechanism from reflection to absorption. It generates a significant number of heterogeneous interfaces among the various EM constituents resulting increased interfacial polarisation and dielectric loss. The progress of heterogeneous interface material is endless and this novel class of materials is widely used in various wearable devices and radiation source. Finally, the challenges and prospects on the development of carbon-based multiple-interfaces composites are discussed in detail.

Transition metal impregnated nanostructured oxide material for broadband electromagnetic interference shielding: A theoretical and experimental insight

In this communication, the electromagnetic interference shielding (EMI) performance and dielectric properties of the high temperature sustainable α-MnO2 semiconductor quantum dots (SQDs) have been modulated by incorporating cobalt ions into its crystal structure by employing a modified chemical synthesis technique as well as post-calcination treatment. The phase and structural investigation confirm the Co atoms are present inside the (2×2) tunnel of α-MnO2 hollandite type network and with the increasing sintering temperature the crystallite size of the samples has been found to be increasing. The theoretical bandgap energy of the samples using generalized gradient approximation with Hubbard U correction term (GGA + U) is found to be in good agreement with the experimental findings. From PL spectra it has been found that the peak locations are shifted because of the variation of the inherent bandgap energy which confirms the particles are quantum dots (QDs) in nature. Gigantic dielectric constant has been observed for the sample CM450 at low frequency (∼0.7 M at 40 Hz) with moderate tangent loss. This enhances the shielding performance (∼48 dB at 17.5 GHz) of the unwanted electromagnetic signals emitted from the daily using electronic gadgets at X-band and Ku-band. Such valuable shielding performance can be ascribed to the dual effect of dipolar as well as Maxwell Wagner Sillars (MWS) interfacial polarization effect. Considering all the performance it can be clearly concluded that the presence of a foreign element like Co creates a remarkable footprint to enhance all the electrical performance of the α-MnO2 SQDs and makes the material highly suitable for high dielectric separator as well as an efficient material for EMI pollution shielding application in electronic industry.

Thermally conductive MWCNTs/Fe3O4/Ti3C2T MXene multi-layer films for broadband electromagnetic interference shielding

• MWCNTs/Fe 3 O 4 /Ti 3 C 2 T x MXene composite film with multi-layer architecture was fabricated by a facile method. • The obtained composite film exhibited high comprehensive performance, including high thermal conduction property and broadband EMI shielding property. • The EMI shielding mechanism of the composite film was comprehensively disclosed. The Ti 3 C 2 T x MXene is thought to be a promising candidate for next-generation electromagnetic interference (EMI) shielding materials. However, its broadband shielding capability and thermal conduction performance are insufficient to meet the growing demands. Herein, we reported a layer-by-layer composite film composed of Ti 3 C 2 T x MXene, multi-walled carbon nanotubes (MWCNTs), and Fe 3 O 4 nanoparticles. Benefitting from the architecture and the synergistic effect of components, the obtained composite film exhibited high comprehensive performance. Specifically, the introduction of Fe 3 O 4 magnetic nanoparticles effectively reduced the impedance mismatch between the composite film and air and enhanced the magnetic loss of the composite film. The layered structure prolonged the transmission path of electromagnetic waves inside the composite film and constructed a rich conductive network, causing interfacial polarization and ohmic loss. The results indicated that the composite film (52 μm) delivered a high EMI shielding effectiveness of 49 dB in the frequency range from X-band to K u -band. Furthermore, the MWCNTs layers in the composite films provided numerous heat transfer channels, reducing phonon scattering during heat transfer and resulting in a maximum thermal conductivity of 8.241 W/(m K).

3D printing of resilient, lightweight and conductive MXene/reduced graphene oxide architectures for broadband electromagnetic interference shielding

The lightweight MXene scaffolds by direct ink writing technique show great structure design flexibility, tunable electromagnetic shielding effectiveness up to ∼100 dB and excellent reversible compressibility of up to 90% strain.

Flexible liquid metal/cellulose nanofiber composites film with excellent thermal reliability for highly efficient and broadband EMI shielding

• A novel strategy was proposed to achieve flexible liquid metal/cellulose nanofiber film. • The film exhibits excellent structural stability and EMI shielding effectiveness of ~ 65 dB. • Simulation in the frequency domain was introduced to investigate the shielding mechanism. Liquid metal (LM) is a promising candidate for electromagnetic interference (EMI) shielding due to the superb electrical conductivity and easy processing. However, poor compatibility caused by high surface tension, insulated oxide shells formed during processing, and unmanageable fluidity at elevated temperature of LM severely hinder its application in the field of EMI shielding. Herein, we develop a novel processing strategy integrating ball-milling dispersion, freeze-drying and compression molding to achieve free-standing and flexible LM/cellulose nanofiber composites (LM/CNF) film, in which the oxide shells of LM droplets generated by ball-milling are broken by mechanical compression, and LM droplets are coalesced while confined by CNF to construct a continuously conductive path. As a result, the robust LM/CNF film shows tensile strength of above 30 MPa, and it possesses electrical conductivity of 96,000 S/m, leading to remarkable shielding effectiveness (SE) of above 65 dB with a thickness of only 300 µm in a broad frequency range of 4–18 GHz covering C-band, X-band and Ku-band. Moreover, LM/CNF film exhibits excellent structural stability and EMI shielding performance reliability after high-temperature treatment. Besides, simulation in the frequency domain with ANSYS HFSS 2019 R2 is performed to intuitively understand the shielding mechanism of LM/CNF film. It is found that the attenuation of electromagnetic waves is mainly based on reflection. This study proposes a fresh scenario to achieve high-performance EMI shielding material and paves the way for potential applications of LM in portable and wearable smart electronics.

Development of lightweight carbon nanotube-based epoxy nanocomposite shield for broadband electromagnetic interference shielding: estimating shielding effectiveness and experimental validation

Lightweight carbon nanotube (CNT)-based epoxy nanocomposite shield with 0.5 mm thickness are fabricated at various CNT concentrations for broadband electromagnetic interference shielding in this work. The electromagnetic parameters of the samples measured using impedance spectroscopy are used to estimate shielding effectiveness in the X and Ku frequency bands using finite element-based method. The shielding effectiveness obtained using the finite element model at 2 wt.% CNT concentration in the X and Ku bands are 19 dB and 26 dB which agrees well with experimental results obtained using waveguide measurement which amounts to 20 dB and 27 dB, respectively. The finite element model developed for the estimation of shielding effectiveness provides promising results in both X and Ku bands which are experimentally validated. Shielding effectiveness of the prepared samples in the Ku band is superior to that in the X band. High values of shielding in both X and Ku bands qualify it as a good broadband shield with minimal thickness and less weight and cost. Absorption phenomenon dominates the shielding mechanism in both these bands due to the dielectric losses and the electron-rich skeletal structure of CNT. The dominance of absorption loss increases as the frequency shifts from X to Ku band qualifying the developed nanocomposite material as a good broadband shield covering both X and Ku bands.

Characterization of Carbon-Based Epoxy Nanocomposite Shield for Broadband EMI Shielding Application in X and Ku Bands

Electromagnetic interference (EMI) shielding in the X and Ku bands of electromagnetic spectrum are vital for communication and military applications. This work aims at developing and characterizing nanocomposite shield with two nano fillers- carbon nanotubes (CNT) and carbon nanofibers (CNF) dispersed at various weight combinations for shielding both X and Ku bands at minimum cost. DC conductivity of the prepared CNT-CNF based epoxy nanocomposites obey classical law of percolation theory. AC conductivity follows universal dynamic response (UDR) when CNT concentration is above 0.5wt.%. The rise in permittivity with filler concentration at a particular frequency is more prominent with the increase in CNF concentration. The measurement of shielding effectiveness of the prepared samples demonstrates that maximum shielding obtained is 24 dB and 30 dB in the X and Ku bands respectively and the optimum filler combination is 1wt.%CNT-5wt.%CNF agreeing with the results obtained from characterization. The nanocomposites with higher CNF content exhibit better shielding as compared with higher CNT content owing to the higher aspect ratio of CNF used. The shielding efficiency increases as the frequency band shifts from X to Ku. Absorption loss is the prominent mechanism of shielding in both bands, avoiding the chance for electromagnetic pollution.

Dynamic mechanical analysis and broadband electromagnetic interference shielding characteristics of poly (vinyl alcohol)-poly (4-styrenesulfonic acid)-titanium dioxide nanoparticles based tertiary nanocomposites

ABSTRACTNovel tertiary nanocomposite films comprising of poly (vinyl alcohol) (PVA), poly (4-styrenesulfonic acid) (PSSA) and titanium dioxide (TiO2) nanoparticles (NPS) were prepared using simple solvent casting method. The structural, thermal, morphological, thermo-mechanical and electromagnetic interference (EMI) shielding properties of PVA/PSSA/TiO2 nanocomposite films were investigated. The EMI shielding effectiveness (SE) of PVA/PSSA/TiO2 nanocomposite films in the X and Ku band was found to be 12 dB and 13 dB respectively at 25 wt% TiO2 NPs loading. These results demonstrate the possible applications of PVA/PSSA/TiO2 nanocomposite films as low cost, lightweight and flexible material for EMI shielding.

Highly Transparent and Broadband Electromagnetic Interference Shielding Based on Ultrathin Doped Ag and Conducting Oxides Hybrid Film Structures.

Reducing electromagnetic interference (EMI) across a broad radio frequency band is crucial to eliminate adverse effects of increasingly complex electromagnetic environment. Current shielding materials or methods suffer from trade-offs between optical transmittance and EMI shielding capability. Moreover, poor mechanical flexibility and fabrication complexity significantly limit their further applications in flexible electronics. In this work, an ultrathin (8 nm) and continuous doped silver (Ag) film was obtained by introducing a small amount of copper during the sputtering deposition of Ag and investigated as transparent EMI shielding components. The electromagnetic Ag shielding (EMAGS) film was realized in the form of conductive dielectric-metal-dielectric design to relieve the electro-optical trade-offs, which transmits 96.5% visible light relative to the substrate and shows an excellent average EMI shielding effectiveness (SE) of ∼26 dB, over a broad bandwidth of 32 GHz, covering the entire X, Ku, Ka, and K bands. EMI SE >30 dB was obtained by simply stacking two layers of EMAGS films together and can be further improved up to 50 dB by separating two layers with a quarter-wavelength space. The flexible EMAGS film shows a stable EMI shielding performance under repeated mechanical bending. In addition, large-area EMAGS films were demonstrated by a roll-to-roll sputtering system, proving the feasibility for mass production. The high-performance EMAGS film holds great potential for various applications in wearable electronics, healthcare devices, and electronic safety areas.

Ni deposited onto MWCNTs buckypapers for improved broadband EMI shielding

Highly flexible, mechanically robust and ultra-thin Ni deposited onto multi-walled carbon nanotubes (MWCNTs) buckypapers (BPs) were fabricated via vacuum filtration and magnetron sputtering. The samples were characterized structurally using scanning electron microscopy and X-ray Diffraction. Electromagnetic interference (EMI) shielding effectiveness (SE) of Ni deposited onto MWCNTs BPs with different deposition time (0, 30 and 60 min) were tested in frequency range of 2–18 GHz, including S-band, C-band, X-band and Ku-band. The 60 min Ni deposited onto MWCNTs BPs exhibited much higher EMI SE of average value up to 42.59 dB with the thickness of only 0.105 mm. Based on reliability study, the 60 min Ni deposited onto MWCNTs BPs retains 94.3% of its EMI SE after 500 cycles of mechanical bending. Therefore, the results and techniques promise a simple and effective approach to achieve light-weight and ultra-thin composite films for a wide application at the prospect of the field of EMI shielding.

Magnetic, electrically conductive and lightweight graphene/iron pentacarbonyl porous films enhanced with chitosan for highly efficient broadband electromagnetic interference shielding

Highly efficient and lightweight electromagnetic interference (EMI) shielding materials have gained tremendous interests due to the urgent requirement for smart electronic devices and aerospace applications. Herein, we demonstrate a highly efficient hydrazine-induced foaming approach to fabricate magnetic, highly electrically conductive, and lightweight graphene/iron pentacarbonyl (IP) porous films for broadband EMI shielding application. The chitosan introduced effectively optimizes the microcellular structures by improving the interfacial adhesion between graphene sheets and thus enhances the electrical conduction of the porous films with IP flakes. The resultant porous structure not only reduces the density of the films, but also improves the electromagnetic radiation attenuation by repeated scattering of the incident microwave. The presence of magnetic IP flakes endows the porous film with magnetic property and enhanced EMI shielding performance by combining the dielectric and magnetic losses. Thus, the porous film with a small thickness of 0.3 mm and a low density of 0.12 g/cm3 exhibits an excellent broadband EMI shielding performance of >38 dB in the frequency range of 8.2–59.6 GHz with a total bandwidth of 51.4 GHz. These results indicate that the lightweight porous film with outstanding magnetic and electrical properties could be used as multifunctional high-performance EMI shielding materials.

Highly anisotropic Cu oblate ellipsoids incorporated polymer composites with excellent performance for broadband electromagnetic interference shielding

In this study, highly anisotropic Cu oblate ellipsoids incorporated polymer composites were prepared that revealed excellent broadband electromagnetic shielding effectiveness of 80.0 to 62.1 dB at a frequency region between 300.0 KHz and 12.0 GHz, at low Cu contents. Cu-coated hollow polymer beads were fabricated through electroless plating of Cu on the polymer hollow beads. The hollow polymer beads were prepared through thermal expansion of acrylonitrile-based polymer beads containing a blowing agent. These beads were capable of incorporating highly anisotropic 2-dimensional (2D) Cu oblate ellipsoids into polymer composite through simple compression molding process. The resulting broadband electromagnetic shielding performance attributes to a low percolation behavior of the composites due to high anisotropy of the conductive Cu filler and their multilayered structure in the composites.

Polyaniline-coated SnO/Y2O3 Nanocomposites for Broadband EMI Shielding and Microwave Absorption

There is an ever increasing demand for high-performance electromagnetic interference (EMI) shielding materials due to the rapid proliferation of electro/electrical systems. Herein, we report the investigations on EMI shielding and microwave absorption properties of synthesized polyaniline-coated stannous oxide/yttrium trioxide (PAni/SnO/Y2O3) nanocomposites. The spectroscopic characterizations of the composites were performed using Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The nanocomposites showed effective absorption dominant EMI shielding due to the modified electric and electromagnetic effect of the nanocomposites. The EMI shielding measurements were carried out in the frequency range of 12-18 GHz (Ku-Band), relevant for practical applications. The shielding analysis demonstrates the synergistic effect of the complementing phases (i.e. PAni, SnO and Y2O3) which leads to high shielding effectiveness (SE) in the range of –33 to –42.6 dB (< 99.9% attenuation). The absorption dominated shielding effectiveness and the possibility to tailor the properties of these nanocomposites by varying the concentration of dispersants content can be optimized for making effective broadband microwave shields.

Microcellular graphene foam for improved broadband electromagnetic interference shielding

As reported, the foaming of layered graphene films into porous graphene foams could improve their performance for absorbents, catalysis and supercapacitors. Herein, to emphasize the impact of porous structure on electromagnetic interference (EMI) shielding, the direct comparison between graphene film (G-film) and corresponding microcellular graphene foam (G-foam) in terms of EMI shielding efficiency has been investigated in a broadband frequency range of 8.2–59.6 GHz, including X-band, Ku-band, K-band, Ka-band, and U-band. Consequently, despite the lower electrical conductivity of the as-prepared G-foam, it exhibited an improved average shielding effectiveness (SE) of ∼26.3 dB over the entire frequency range in comparison with that of G-film (∼20.1 dB). Implication of the results suggested that the foaming of layered graphene films into porous graphene foams could lead to an improvement in EMI shielding, which should be ascribed to the formation of improved internal multiple reflections at the large cell–matrix interfaces owing to the existence of microcellular structure in G-foam. We believe that this research would open up new opportunity for the development of graphene foams in the field of EMI shielding.

Polyaniline–antimony oxide composites for effective broadband EMI shielding

Conducting polyaniline (PAni)–antimony trioxide (Sb2O3) composites with different weight percentages (wt%) of Sb2O3 in PAni have been synthesized by in situ chemical oxidative polymerization. The composites were structurally and morphologically characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Measurements of electromagnetic interference (EMI) shielding, complex permittivity and microwave absorbing as well as reflecting properties of the composites were carried out in the frequency range of 8–18 GHz, encompassing the microwave X and Ku bands of practical relevance. All the computations are based on microwave scattering parameters measured by transmission line waveguide technique. It is observed that the presence of Sb2O3 in the PAni matrix affects the electromagnetic shielding and dielectric properties of the composites at microwave frequencies. The composites have shown better shielding effectiveness (SE) in both the X (SE in the range −18 to −21 dB) and Ku (−17.5 to −20.5 dB) bands. e′ and e′′ values of the PAni–Sb2O3 composites are in the range of 64–37 and 63–30, respectively, in the frequency range of 8–18 GHz. Dielectric measurements indicated the decrease in dielectric constant with the increase in wt% of Sb2O3. The results obtained for the reflection and absorption coefficients indicated that PAni–Sb2O3 composites exhibit better electromagnetic energy absorption throughout the X and Ku bands. The results indicated that PAni–Sb2O3 composites can be used as potential microwave absorption and shielding materials.