High Electromagnetic Shielding Effectiveness Research Articles

Investigations on morphology, tribology, rheology, thermo-mechanical properties, and EMI shielding of WC/MWCNT nanohybrids in polypropylene

This study is focused to explore the synergism of dual nanofillers (tungsten carbide (WC) and multiwalled carbon nanotubes (MWCNTs)) in melt extruded PP composites. The synergy of fillers in PP enhanced the elastic modulus, tensile strength, and critical stress intensity factor by 141.8%, 35.4%, and 62.6%, respectively, at an optimum filler content of 1 wt% of WC and 2 wt% of MWCNTs. In the hybrid composites, activation energy to initiate thermal decomposition raised by 78% and wear resistance increased by 93%, and the hybrid composites exhibited enhanced reflectivity in the X band region, which contributed to high electromagnetic shielding effectiveness. The improvement in the properties makes the current hybrid composite system an ideal candidate in application sectors where high modulus, energy absorption, and thermal stability are required.

Preparation and high electromagnetic shielding effectiveness of Cu/FeSiBCuNb/Cu sandwich structural composites

Preparation and high electromagnetic shielding effectiveness of Cu/FeSiBCuNb/Cu sandwich structural composites

La-doped BaSnO3 for electromagnetic shielding transparent conductors

In this work, we find that La-doped BaSnO3 (BLSO) is shown to be a promising electromagnetic shielding transparent conductor. While films grown on industrially practical optoelectronic MgAl2O4 substrates have higher sheet resistance by three orders of magnitude than in previous reports, we show how to recover the sheet resistance close to the single-crystal level by use of an MgO template layer which enables high quality (001)-oriented BLSO epitaxial film growth on (001) MgAl2O4. There is a positive correlation between crystallinity and conductivity; high crystallinity minimizes scattering of free electrons. By applying this design principle to 5–20% doped films, we find that highly crystalline 5% La-doped BLSO films exhibit low sheet resistance of ~ 8.7 Ω ▯ −1, high visible transmittance of ~ 80%, and high X-band electromagnetic shielding effectiveness of ~ 25.9 dB, thus outperforming transparent conducting oxides films of Sn-doped In2O3 and SrMoO3.Graphical

Rapid Fabrication of Flexible Cu@Ag Flake/SAE Composites with Exceptional EMIS and Joule Heating Performance.

High electromagnetic interference shielding (EMIS) effectiveness and good thermal management properties are both required to meet the rapid development of integrated electronic components. However, it remains challenging to obtain environmentally friendly and flexible films with high EMIS and thermal management performance in an efficient and scalable way. In this paper, an environmentally friendly strategy is proposed to synthesize multifunctional waterborne Cu@Ag flake conductive films using water as the solvent and silicone-acrylic emulsion (SAE) as a matrix. The obtained films show high electrical conductivity and exceptional EMI SE and electrothermal conversion properties. The EMI SE in the X-band is higher than 76.31 dB at a thickness of 60 μm owing to the ultrahigh electrical conductivity of 1073.61 S cm-1. The film warms up quickly to 102.1 °C within 10 s under a low voltage of 2.0 V. In addition, the shielding coating is sufficiently flexible to retain a conductivity of 93.4% after 2000 bending-release cycles with a bending radius of 3 mm. This work presents an alternative strategy to produce high EMIS effectiveness and Joule heating films for highly integrated and flexible electronic components in a green, scalable, and highly efficient way.

Ultralight and flexible electrospun PMIA/AgNW/Ni composite membrane with thermostability and excellent electromagnetic interference shielding effectiveness

In order to deal with the more complex electromagnetic radiation environment, there is highly desirable to manufacture a high-performance electromagnetic shielding material with excellent electromagnetic shielding efficiency, flexibility, thermal properties, fatigue resistance, and other qualities. In this paper, we fabricated an ultralight, flexible, and heat-resistant poly-m-phenylene isophthalamide (PMIA)/Ag nanowires(AgNWs)/Ni composite nanofiber film via electrospinning, spray coating, and electroless plating. Compared with different AgNWs spraying contents, the highest electromagnetic shielding effectiveness, about 96 dB with a thickness of ∼150 µm, is generated by spraying 33.333 mg/cm2 AgNWs suspension. Additionally, because of the benefit of the PMIA, this PMIA/AgNW/Ni composite membrane maintains a constant EMI SE value (over 90 dB) after a high-temperature process under 200 °C, which only decreases by 3.33 %. The excellent performance of the material is due to its large porosity and sandwich structure, which can dissipate electromagnetic waves within the material, with only a very small portion of the electromagnetic waves passing through it. Therefore, this material has a potential application for use in diverse harsh settings.

Direct conversion of CO2 to graphene via vapor–liquid reaction for magnesium matrix composites with structural and functional properties

Converting CO 2 to valuable materials is attractive in environmental protection and resource utilization. In this study, a vapor–liquid interface reaction system for mass production of high-quality graphene is reported. The graphene obtained has high crystallinity and few defects during the reaction of CO 2 and Mg melt. The growth mechanism of graphene is demonstrated in vapor–liquid interface area by combining the CO 2 bubbles as a soft template to guide growth with the confinement effect of dense MgO nanoparticles. The quality of the graphene is verified by epoxy composites with high electromagnetic shielding effectiveness. Additionally, the V–L reaction method ingeniously solves the dispersion of graphene in metal, providing a preparation strategy of Mg matrix composites with structure and function integration.

Strong conductivity enhancement of La-doped BaSnO3 transparent films on Al2O3 with the assistance of templated epitaxy for electromagnetic shielding in extreme environments

Transparent La-doped BaSnO3 (BLSO) epitaxial films grown on expensive perovskites show promising conductive properties. However, BLSO films on Al2O3 have a higher sheet resistance by two orders of magnitude. In this research, the sheet resistance of BLSO films is recovered to that of the single-crystalline level by growing (111)-oriented BLSO epitaxial films on (0001)Al2O3 with the assistance of (111)BaZrO3/MgO template bilayer. Their intriguing transparent conductive properties, including high electromagnetic shielding effectiveness (~ 13.2 dB at 10 GHz) and high stability at 700 °C, will promote stable optoelectronic applications in extreme environments with economic benefits.Graphical

Preparation of lightweight and high‐strength polypropylene‐based ternary conductive polymer foams by in situ microfiber reinforcement

AbstractConductive polymer composites (CPCs) have demonstrated significant potential in the aerospace, electronics, and communications industries. In this study, polypropylene (PP)/multiwalled carbon nanotubes (MWCNTs) binary composites and in situ fiber reinforced multicomposites made from PP/MWCNTs were fabricated by microcellular injection molding. In addition to crystallization behavior, foam morphology, mechanical properties, dielectric properties, and electromagnetic shielding properties of the composites were analyzed. According to the results, microporous structures can facilitate the distribution of conductive fillers, thereby enhancing the electromagnetic shielding performance and mechanical properties of the composite. In situ microfiber networks display a heterogeneous nucleation effect, resulting in an increase in foam density, which improves composite performance. In situ fiber‐reinforced microporous multicomposites are capable of exhibiting higher elongation at break and electromagnetic shielding properties than binary systems, and the multicomposites can achieve greater electromagnetic shielding effectiveness (SE) with fewer conductive fillers. Ultimately, fiber‐reinforced microporous composites with an elongation at break of 194.40%, an electromagnetic shielding effect of >20 dB, and an absorption mechanism are produced. A feasible method is presented in this study for preparing CPCs that produce light weight, excellent mechanical properties, and high electromagnetic SE at low filler levels.

Achieving absorption-type electromagnetic shielding performance in silver micro-tubes/barium Ferrites/Poly(lactic acid) composites via enhancing impedance matching and electric-magnetic synergism

High conductivity can give materials excellent electromagnetic shielding performance, but it leads to serious impedance mismatching and causes inevitable secondary pollution. Developing materials with both excellent microwave absorption and microwave shielding performance remains a formidable challenge. Herein, absorption-type electromagnetic shielding materials with high electromagnetic shielding effectiveness (EMW SE) values were successfully prepared by combining hollow silver micro-tubes and magnetic nano-barium ferrites. The electromagnetic parameters and impedance matching of the composites could be easily regulated by changing the ratio of silver micro-tubes (C) and nano-barium ferrites (M). Thanks to micro-tube structure and the electric-magnetic synergism of the fillers, the composites with the C:M ratio of 9:1 exhibited a high absorption coefficient (A) value of ∼0.77 and a high EMW SE value of ∼100 dB, simultaneously. The absorption-type shielding mechanism of the composites was also evaluated via discussing real and imaginary parts of complex permittivity, real and imaginary parts of complex permeability, and Cole-Cole curves. Furthermore, the composites with the C:M ratio of 3:7 exhibited excellent microwave adsorption performance with the minimum reflection loss of −46.3 dB at thickness of 3.0 mm and a maximum effective absorption band-width of 6.13 GHz.

Stable Correlated 4d2 SrMoO3 Films Epitaxially Coated on Al2O3 for Electromagnetic Shielding and Transparent Conductors

AbstractCorrelated perovskites have attracted significant attention worldwide for their potential application in transparent conductors. However, most studies in this area have focused on single‐crystalline films grown on expensive perovskites. In this study, the transparent conducting properties of SrMoO3 epitaxial films grown on Al2O3, the most commonly used substrate for optoelectronics, are investigated. The 45−80‐nm‐thick SrMoO3 epitaxial films on ‐oriented Al2O3 exhibit low sheet resistance (< 50 Ω □−1) at room temperature and high ultraviolet‐visible transmittances (> 60%), comparable with the values expected from single‐crystalline films. The highly conductive properties induced by two electrons in the outermost 4d orbitals guarantee a high electromagnetic shielding effectiveness of approximately 28.5 dB at 10 GHz in the X‐band. The SrMoO3 films are thermally stable below 450 °C in air and 700 °C in vacuum. Taken together, these results indicate that SrMoO3 epitaxial films grown on Al2O3 can be highly promising for optoelectronic applications in extreme environments.

Conductive and superhydrophobic Ag/PDMS films with high stability for passive de-icing and electromagnetic shielding

In this work, silver nanoparticles (AgNPs) are synthesized and sprayed onto the surface of cotton fabric to produce a conductive film. Then a layer of poly(dimethyl siloxane) (PDMS) was deposited onto the film to prepare Ag/PDMS composite film. The Ag film is with FCC crystalline and particle-like morphology, while layers of organic PDMS are cladding the Ag micro-nano structures. With increasing spraying time, nano‑silver particles changed from round spherical to worm-like, resulting rougher and higher electrical conductivity. By optimizing the PDMS coatings, the contact angle of surface winkled-like microstructure reached 163° and volume resistivity was 9.2 × 10−3 Ω·cm. In addition to the improvement of interfacial adhesion, the introduction of PDMS made the loose particles closely connected, which enhanced the stability of the structure. Meanwhile, the films exhibited great electron-thermal effects, which could be applied in high-speed deicing. Combined with superhydrophobicity, the electromagnetic shielding efficiency can reach 75 dB. The Ag/PDMS films maintained high electromagnetic shielding effectiveness even for servicing in harsh environments, showing that this conductive superhydrophobic fabric composite can be applied as a new electromagnetic shielding material for flexible electronic devices.

Electromagnetic Shielding of Composite Films Based on Graphite, Graphitized Carbon Black and Iron-Oxide

The present work regards the development of paint-like composites based on mixtures of carbon materials with magnetite in polyvinyl butyral matrix, and the investigation of the dependence on the electrical characteristics and the frequency of their electromagnetic shielding properties. It was found that high electromagnetic shielding effectiveness requires not only the presence of a high content of carbon components in the composite, but also the absence of an agglomeration of filler particles. Using these paint-like materials, a shielding effectiveness of up to −35 dB of UHF radiation can be obtained. A combination of fillers based on carbon-graphite materials of different morphology and magnetite was found to enhance shielding efficiency.

Biomass-Derived, Highly Conductive Aqueous Inks for Superior Electromagnetic Interference Shielding, Joule Heating, and Strain Sensing.

Conductive composite inks are widely used in various applications such as flexible electronics. However, grand challenges still remain associated with their relatively low electrical conductivity and require heavy use of organic solvents, which may limit their high performance in broad applications and cause environmental concerns. Here, we report a generalized and eco-friendly strategy to fabricate highly conductive aqueous inks using silver nanowires (AgNWs) and biomass-derived organic salts, including succinic acid-chitosan (SA-chitosan) and sebacic acid-chitosan. SA-chitosan/AgNW composite coatings can be prepared by directly casting conductive aqueous inks on various substrates, followed by subsequently heating for cross-linking. The composite coatings exhibit an ultrahigh electrical conductivity up to 1.4 × 104 S/cm, which are stable after being treated with various organic solvents and/or kept at a high temperature of 150 °C, indicating their high chemical and thermal resistance. The flexibility and performance durability of these composite coatings were demonstrated by a suite of characterization methods, including bending, folding, and adhesion tests. Moreover, a high electromagnetic interference shielding (EMI) effectiveness of 73.3 dB is achieved for SA-chitosan/AgNW composite coatings at a thickness of only 10 μm due to the ultrahigh electrical conductivity. Additionally, we further demonstrated that such conductive composite inks can be used for fabricating functional textiles for a variety of applications with high performance, such as EMI shielding, Joule heating, and strain sensing. The robust and highly conductive inks prepared by this simple and environmental-friendly method hold great promise as important material candidates for the potential large-scale manufacturing of flexible and wearable electronics.

Sandwiched cellulose nanofiber /boron nitride nanosheet /Ti3C2Tx MXene composite film with high electromagnetic shielding and thermal conductivity yet insulation performance

The rapid development of electronic devices has led to widespread demand and research on electronic packaging materials with electromagnetic shielding and thermal conductivity (TC) properties due to the inevitable issues of the electromagnetic radiation and thermal accumulation. However, there exists a huge challenge to simultaneously achieve high electromagnetic shielding and TC as well as the electrical insulation requirement as electromagnetic shielding predominantly relies on electrical conductivity of materials. Multilayer structure can endow composite materials with a variety of properties. Therefore, in this work, we fabricated sandwiched cellulose nanofiber/boron nitride nanosheet/Ti3C2Tx MXene films by using a simple and effective alternating vacuum filtration method, and as a result, the special sandwich structure endows the film with excellent electromagnetic shielding, insulation and TC performance. The composite film has an extremely high electromagnetic shielding effectiveness up to 60.7 dB at 8.2 GHz as well as still maintains good electrical insulation properties due to the presence of the CNF/BNNS layer on the surface. Moreover, when the content of BNNS in the CNF/BNNS layer reaches 70 wt%, the sandwiched film has excellent in-plane TC of 19.97 W m−1 K−1. The sandwiched film with excellent electromagnetic shielding and high TC yet insulation performance has great application value in highly integrated electronic devices.

Simultaneous achievement of high electromagnetic shielding effectiveness (X-band) and strength in Mg-Li-Zn-Gd/MWCNTs composite

In this study, the Mg-9Li-3Zn-0.5Gd/MWCNTs composite was prepared by the method of heat treatment+electrophoretic deposition (EPD)+accumulative roll bonding (ARB), and the microstructure, electrical conductivity, electromagnetic (EM) shielding properties in the X-band (8.2–12.4 GHz) and strength were evaluated. The microstructure characterization shows that, after five ARB cycles, MWCNTs are uniformly distributed in the Mg-Li matrix, and severe plastic deformation promotes the dynamic precipitation of the nano-scale secondary phase particles, which greatly weakens the lattice distortion of the Mg-Li matrix. Besides, MWCNTs induces a large amount of ultrafine nano-scale W-phase precipitation. The property evaluation indicates that the electrical conductivity, ultimate tensile strength and yield strength of C-ARB5 sheet are 7.60 MS/m, 280 MPa and 264 MPa, respectively, which are increased by 1.9%, 4.2% and 4.9% compared with ARB5 sheet. In the X-band frequency range, the electromagnetic interference (EMI) shielding effectiveness (SE) of ARB5 sheet is 77–96 dB, and that of C-ARB5 sheet is increased to 89–100 dB. The improvement of C-ARB sheets property is mainly attributed to the uniformly distributed MWCNTs inducing precipitation of ultrafine nano-scale W-phase.

Patternable cellulose/MWCNT laminated nanocomposites with anisotropic thermal and electrical conductivity

To construct eco-friendly materials with anisotropic thermal/electrical conductivity and designable structure and shape not only is the goal of electrical materials, but also meets the requirement of sustainable society. In this work, patternable and laminated cellulose/MWCNT nanocomposites with excellent anisotropic thermal and electrical conductivity are prepared by a scalable and eco-friendly process, including a paper-making step, assembly step and in-situ welding step. In the obtained nanocomposites, the cellulose layer acts as the insulator, and the cellulose/MWCNT layer as the electrical and thermal conductor with a special segregated MWCNT network. As a result, the in-plane and through-plane electrical conductivity of the cellulose/MWCNT nanocomposite with 22.7 wt% MWCNT are 1458 and 1.48 × 10-10 S/m, respectively, and the in-plane and through-plane thermal conductivity are 1.98 and 0.34 W·m-1·K-1, respectively. Moreover, the cellulose/MWCNT nanocomposites have high electromagnetic shielding effectiveness of 31.1 dB when the thickness is 0.9 mm, good tensile strength of 156 MPa, and high shape stability at 240 °C. More interestingly, the laminated cellulose/MWCNT materials with patterned shape and sophisticated conductive circuit can be easily fabricated to work as a special and custom-tailor electronic element, thermal management device and electric-heating anti-counterfeiting pattern. Such novel cellulose/MWCNT nanocomposites prepared by a simple, effective and scalable process exhibit a huge potential in environmentally-friendly electrical and thermal management device, electromagnetic shielding element and advanced electronic anti-counterfeiting tag.

Sandwich-structural Ni/Fe3O4/Ni/cellulose paper with a honeycomb surface for improved absorption performance of electromagnetic interference

Highly efficient shielding materials with an excellent electromagnetic wave absorption have gained increased attention. A new design was used to provide cellulose paper with a high electromagnetic shielding effectiveness (EMI SE) and improve the absorption performance by constructing an asymmetry sandwich structure that consisted of a dense nickel coating, Fe3O4 nanoparticles and a porous nickel layer. This unique structure caused a “multiple reflection-absorb-reflection” process when the electromagnetic waves penetrated the sample. The EMI absorption (SEA) and total SE (SET) increased with Fe3O4 absorption time increasing at 8.2–12.4 GHz, which was attributed to the synergistic effect between porous nickel layer and Fe3O4 nanoparticles. The SEA and SET of the sample with a thickness of 0.195 mm can achieved 18.57 and 41.88 dB, respectively. The design was conducive to improving the magnetic and corrosion resistance properties. This study provided a novel path to obtain a low cost and lightweight electromagnetic shielding material that can reduce secondary radiation.

Hierarchical, seamless, edge-rich nanocarbon hybrid foams for highly efficient electromagnetic-interference shielding

Lightweight, flexible, ultrahigh-performance electromagnetic-interference (EMI) shielding materials are urgently required in the areas of aircraft/aerospace, portable and wearable electronics. Herein, 1D carbon nanotubes (CNT) and carbon nanofibers (CNF) with 2D edge-rich graphene (ERG) are used to form a lightweight, flexible CNT-ERG-CNF hybrid foam. This foam was fabricated through a self-sacrificial templating chemical vapor deposition process, where nanocarbons bond through covalent bonding, forming a hierarchical 3D hybridized carbon nanostructure. Multistage conductive networks and heterogeneous interfaces were constructed using edge-rich nanocarbons to increase the induced currents and interfacial polarization which makes great contributions to achieve high absorption electromagnetic shielding effectiveness (SEA). The CNT-ERG-CNF hybrid foam exhibits EMI shielding effectiveness (SE) exceeding 55.4 dB in the X-band while the specific SE (SSE, SE divided by mass density) achieves 9200 dB cm3 g-1, which surpasses that of nearly all other carbon-based composite materials. Furthermore, the structural stability and durability of the flexible CNT-ERG-CNF hybrid foams is examined by measuring EMI SE after 10000 times cyclic bending. Remarkably, this work not only provides a new idea for preparing hierarchical carbon materials for a wide range of applications, but presents some fundamental insights for achieving higher absorption losses in EMI shielding materials.

Electromagnetic Shielding Effectiveness and Conductivity of PTFE/Ag/MWCNT Conductive Fabrics Using the Screen Printing Method

The management of the electromagnetic interference (EMI) of thin, light, and inexpensive materials is important for consumer electronics and human health. This paper describes the development of conductive films that contain a silver (Ag) flake powder and multiwall carbon nanotube (MWCNT) hybrid grid on a polytetrafluoroethylene (PTFE) film for applications that require electromagnetic shielding (EMS) and a conductive film. The Ag and MWCNT hybrid grid was constructed with a wire diameter and spacing of 0.5 mm. The results indicated that the proposed conductive films with 0.4 wt% MWCNTs had higher electromagnetic shielding effectiveness (EMSE) and electrical conductivity than those with other MWCNT loading amounts. The results also showed that the film with 0.4 wt% MWCNT loading had a high 62.4 dB EMSE in the 1800 MHz frequency and 1.81 × 104 S/cm electrical conductivity. This combination improved stretchability, with 10% elongation at a 29% resistivity change rate. Conductive films with Ag/MWCNT electronic printing or lamination technologies could be used for EMI shielding and electrically conductive applications.

Significantly high electromagnetic shielding effectiveness in polypyrrole synthesized by eco‐friendly and cost‐effective technique

AbstractA facile and eco‐friendly synthesis of polypyrrole from monomer pyrrole using nominal amount of ferric chloride hexahydrate (FeCl3.6H2O) oxidant in aqueous solution by chemically oxidative polymerization method has been reported. The use of aqueous solvent and ferric chloride hexahydrate salt in polypyrrole synthesis have an eco‐friendly route favorable for the production of polypyrrole in large quantities. The synthesized polypyrrole samples exhibit good electrical conductivity (2 S/cm) and yield of 80% for reaction time of 8 hr at 5°C. Quality and properties of polypyrrole samples have been thoroughly investigated with varying reaction time and temperature while other synthesis parameters like molar ratio of oxidant to monomer, oxidant concentration, and solvent were kept constant. X‐ray diffraction analysis of polypyrrole with a shorter reaction time shows the presence of iron oxide (Fe2O3) peaks. The complete reaction may not occur at shorter reaction times due to which residual ferric ions converted into Fe2O3. X‐ray photoelectron spectroscopy measurement of polypyrrole also confirms the formation of Fe2O3. Appropriate selection of reaction time and temperature produced pure phase polypyrrole with high yield and good conductivity. Synthesized polypyrrole by our eco‐friendly and cost‐effective technique exhibits prominent electromagnetic shielding effectiveness value of 30 dB in the X‐band (8–12 GHz).