EMI SE Value Research Articles

Lignin doped epoxy acrylate sandwich electromagnetic shielding material synergized with Fe3O4 and CNT

A kind of novel electromagnetic shielding sandwich coating material with excellent electromagnetic interference shielding and coating properties was explored in this work. The interlayer was obtained through the in situ reaction of lignin, epoxy and acrylate doped with modified Fe3O4 nanoparticles (Fe3O4) and multi-wall carbon nanotubes (CNT) (FCLBEA). The FCLBEA layer was coated by two layers of lignin-based epoxy acrylate (LBEA) on both sides, and the total thickness was only around 1 mm. The SEM image showed that the Fe3O4 and CNT are uniformly dispersed in the LBEA matrix. The electromagnetic interference shielding efficiency (EMI SE) of LBEA@FCLBEA@LBEA sandwich material (LFL) was tested in the frequency range of 8.2–18 GHz, and the EMI SE value was higher than 10 dB in the entire measurement range. When the content of Fe3O4 and CNT was both 5% and the lignin content was 15%, the maximum EMI SE reached 14.8 dB. The LFL showed excellent hardness (4H) and adhesion (standard 1). The lignin enhanced the mechanical properties of LFL due to its benzene ring skeleton structure. In addition, the benzene ring of lignin interacted with CNT through π-π bond, which enhanced the dispersion of carbon nanotubes and Fe3O4 in the matrix, and promoted a complete electronic network formed in the system. The most important, the benzene ring in lignin has certain electromagnetic shielding effect, and can also form a synergistic effect with Fe3O4 and CNT to enhance the electromagnetic shielding performance. It was illustrated that the LBEA@FCLBEA@LBEA sandwich material with excellent overall properties can be promising in wide applications, such as EMI coatings, dark room and military fields.

Effect of printing parameters on the electromagnetic shielding efficiency of ABS/carbonaceous-filler composites manufactured via filament fused fabrication

• FFF to manufacture polymer composites samples for EMI SE application. • Printing patterns influence sample’s electrical conductivity and EMI SE. • Layer high influences sample’s shielding effectiveness. • Increase in CNT amount improves samples electric and electromagnetic properties. This work assesses the influence of material composition as well as printing parameters on the electromagnetic interference shielding effectiveness (EMI SE) of polymeric composites based on poly(acrylonitrile-co-butadiene-co-styrene) (ABS) filled with carbon nanotubes (CNT) and/or carbon black (CB), manufactured via fused filament fabrication (FFF). In the study three compositions were analyzed, ABS with 5 wt% of CNT, ABS with 5 wt% of CB, and a hybrid composite with also 5 wt% total of additive but a (75:25) fraction of CNT:CB. The materials properties were evaluated on samples printed in three different growing directions, horizontal concentric (HC), perpendicular concentric (PC) and horizontal at ±45° (H45). The electrical conductivity of the printed samples are highly influenced by the CNT presence in the composition, and increased with its incorporation. The electrical conductivity values for ABS with 5 wt% of CB were in the range of 10 −12 S. cm -1 , while for hybrid composite and ABS with 5 wt% of CNT values between 10 -8 and 10 -5 S. cm -1 were observed. The EMI SE, for all patterns of printed samples, also increased with the increase of CNT amount and layer thickness, with values of around -16 dB for the composite with only CNT sample, and -14 dB for the hybrid sample. The PC pattern shows high anisotropy among the studied samples, presenting the highest EMI SE value for PC when measured horizontally (PC-H) and the lowest value when measured vertically (PC-V). The results obtained in this study show the real potential of applying FFF for the manufacturing of ABS/carbonaceous composites to be use in EMI shielding applications.

Hydrothermal synthesis of micro-flower like morphology aluminum-doped MoS2/rGO nanohybrids for high efficient electromagnetic wave shielding materials

In this study, a three-dimensional (3D) micro-flower like morphology aluminum-doped molybdenum disulfide/reduced graphene oxide (Al@MoS2/rGO) nanohybrids have been developed using a simple and sensitive hydrothermal approach. Their electromagnetic (EM) parameters (permittivity, permeability) and microwave shielding parameters (S11, S12) have been analyzed and reported for the first time in the microwave frequency range of 8.0–12.0 GHz. It is interesting to note that the electrical conductivity of the nanohybrids increases with the doping concentration of Al-ions, whereas skin-depth has a reverse trend. The 12% Al@MoS2/rGO nanohybrid shows a higher total electromagnetic interference shielding effectiveness (EMI SE) value about SET ~33.38 dB, whereas undoped MoS2/rGO nanohybrid exhibits a lower value around ~17.07 dB at the same thin thickness. The higher doping concentration of Al-ion creates lattice distortion and crystal defects with high charge carrier mobility between multiple interfaces and at defective sites. Hence, the Al-doping into MoS2 lattice supported on the rGO surface can greatly enhance EM wave absorption and EMI SE value. The present work suggests that the 12% Al@MoS2/rGO nanohybrid can be treated as a good microwave absorbing and shielding material and useful in various techno-commercial devices.

Efficient natural rubber latex foam coated by rGO modified high density polyethylene for oil-water separation and electromagnetic shielding performance

The current research work demonstrates preparation and characterization of Reduced Graphene Oxide (rGO)@ High-Density Polyethylene (HDPE) aerogel coated Natural Rubber Latex foam (NRLF) with superhydrophobic and superoleophilic character, good sorption capacity for oil-water separation, high electrical conductivity and electromagnetic interference shielding effectiveness (EMI SE) of the same were studied. The coated NRLF was prepared by using a solution of rGO and HDPE in xylene solvent with cooling process to result into thermally induced phase separation of the graphene and Polyethylene molecular network. The rGO modified HDPE aerogel coated NRLF showed superhydrophobicity with static water contact angle > 150°. The rGO@HDPE aerogel coated NRLF with 2 wt% rGO has reached EMI SE value of 24 dB, meeting commercial requirements. The electrical conductivity, EMI SE and the hydrophobicity of the composites significantly improved after mixing rGO into HDPE sol. This prepared superhydrophobic NRLF with high electric conductivity may find attractive application in oil-water separation and EMI Shielding, which would also be economically favored option in the current scenario.

Plasmolysis-inspired yolk–shell hydrogel-core@void@MXene-shell microspheres with strong electromagnetic interference shielding performance

A high-performance electromagnetic interference shielding film contains PNIPAM@void@PS@Ti3C2Tx nanocomposite microspheres, whose maximum EMI SE value of the film reaches 72 dB at 9.5 GHz with a thickness of 25 μm.

High-efficiency microwave absorption and electromagnetic interference shielding of Cobalt-doped MoS2 nanosheet anchored on the surface reduced graphene oxide nanosheet

In this paper, Co-doped molybdenum disulfide anchored on the surface reduced graphene oxide (Co@MoS2/rGO) has been successfully synthesized using a simple and effective hydrothermal approach to measure their microwave shielding properties. The X-ray diffraction (XRD) technique confirmed the successful doping of magnetic atoms into the MoS2 lattice. The experiments show that 15% and 20% Co@MoS2/rGO nanocomposite have higher electromagnetic interference shielding effectiveness (EMI SE) value up to SET ~ 38.26 and ~ 46.02 dB, respectively. But pure MoS2/rGO nanocomposite demonstrates a lower EMI SE value of around ~ 28.90 dB over the frequency range of 8.0–12.0 GHz with a 1.7 mm thickness. A higher value of the EMI SE depends mainly on the doping percentage of Co-ion. This nanocomposite network enhances the defect dipole polarization, electric conduction, interfacial polarization, and impedance matching characteristics. It is favorable for strong attenuation and dissipation loss ability of microwave energy inside the shielding material. The actual role of Co-doping is to form a highly conductive and magnetic channel between multi-interfaces leading to enhance the migration and hopping of electrons at defective sites or interface. Therefore, the 20% Co@MoS2/rGO nanocomposite is considered as novel microwave shielding material and can be widely used in electronic information and communication devices.

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.

Hybrid Composites Based on Thermoplastic Polyurethane With a Mixture of Carbon Nanotubes and Carbon Black Modified With Polypyrrole for Electromagnetic Shielding

Hybrid conducting composites comprising thermoplastic polyurethane (TPU) and mixtures of carbon black modified with polypyrrole (CB-PPy) and carbon nanotubes (CNT) were prepared by melt mixing process. The electrical conductivity, rheological properties and electromagnetic shielding effectiveness (EMI SE) of TPU/CB-PPy and TPU/CNT composites were also carried out and compared to those results observed for TPU/CB-PPy/CNT hybrid composites. TPU/CNT composites show a very sharp insulator-conductor transition and the electrical percolation threshold was about 1 wt% of CNT, which was lower than that found for TPU/CB-PPy (7 wt%). Moreover, EMI SE values of TPU/CNT composites were higher than those for TPU/CB-PPy due to the denser CNT conductive pathway into TPU matrix. In order to achieve the highest electrical conductivity and EMI SE values, considerable amount of CB-PPy was replaced by CNTs. In fact, the electrical conductivity values increased by combining CB-PPy and CNT, resulting in hybrid composites of TPU/CB-PPy/CNT with higher EMI SE values when compared to TPU/CB-PPy composites. The present study demonstrates the potential use of hybrid polymer composites containing 5 wt% or 8 wt% of CB-PPy/CNT at specific CB-PPy/CNT ratios that reach an EMI SE value as high as -20 dB, indicating the potential use of these materials for electromagnetic shielding application in the X-band frequency region.

Green and eco-friendly chemical exfoliation of two-dimensional nanosheets in the C2H4O3-based system under the assistance of microwave irradiation

Eco-friendly exfoliation of two-dimensional nanosheets from their layered bulks is very attracting but still remains a big challenge. Here, we report a novel preparation route of two-dimensional nanosheets through soaking the bulk layered material in the C2H4O3-based chemical exfoliation system followed by microwave irradiation. This route has demonstrated the effective exfoliation of two-dimensional nanosheets (graphene nanosheets, BNNS and MoS2NS) from their layered bulks in a green and eco-friendly way. The average layer-number of the obtained graphene nanosheets, BNNS and MoS2NS is 4, 6 and 5, respectively, behaving a few-layer feature. Interestingly, when the graphene paper is prepared from the exfoliated graphene nanosheets by simple vacuum filtration and mechanical pressing, its average electrical conductivity is up to 7.36 × 105 S/m and the EMI SE value reaches to 61 dB, both among the highest for the graphene papers reported previously. Since there exists no serious fragmentation of layered materials during the whole exfoliation, the present exfoliation strategy is more competent in preparing the large-sized two-dimensional nanosheets over those conventional green routes.

High-performance copper mesh for optically transparent electromagnetic interference shielding

A wide-spectrum high-transmittance copper mesh was designed and fabricated for effective shielding of electromagnetic waves. Using mask lithography and chemical etching, the copper mesh can be easily fabricated. The thickness of the copper mesh is uniform, whether at the crossing section and the copper wire. The average transmittance of the copper mesh from ultraviolet band to near-infrared band (200–2500 nm) is 96%, in agreement with the designed results. The electromagnetic interference shielding efficiency (EMI SE) is to 16 dB in Ku-band. The result of X-ray photoelectron spectroscopy analysis shows that a large amount of Cu2+ on the surface is reduced to Cu0 and Cu+ after annealing. As result, the EMI SE value of copper mesh has increased by 1.5 dB in Ku-band. We envision that the copper mesh can provide a good solution for optically transparent electromagnetic interference shielding.

Graphene/Carbon Nanotube Hybrid Nanocomposites: Effect of Compression Molding and Fused Filament Fabrication on Properties.

The present work reports on the production and characterization of acrylonitrile butadiene styrene (ABS) hybrid nanocomposite filaments incorporating graphene nanoplatelets (GNPs) and carbon nanotubes (CNTs) suitable for fused filament fabrication (FFF). At first, nanocomposites with a total nanofiller content of GNP and/or CNT of 6 wt.% and a GNP/CNT relative percentage ratio of 0, 10, 30, 50, 70, and 100 were produced by melt compounding and compression molding. Their mechanical, electrical resistivity, and electromagnetic interference shielding effectiveness (EMI SE) properties were evaluated. The hybrid nanocomposites showed a linear increase in modulus and decrease in strength as a function of GNP content; on the other hand, the addition of CNT in hybrid nanocomposites determined a positive increase in electrical conductivity, but a potentially critical decrease of melt flow index. Due to the favorable compromise between processability and enhancement of performance (i.e., mechanical and electrical properties), the hybrid composition of 50:50 GNP/CNT was selected as the most suitable for the filament production of 6 wt.% carbonaceous nanocomposites. EMI SE of ABS-filled single CNT and hybrid GNP/CNT nanofillers obtained from compression molding reached the requirement for applications (higher than −20 dB), while slightly lower EMI SE values (in the range −12/−16 dB) were obtained for FFF parts dependent on the building conditions.

3D Shapeable, Superior Electrically Conductive Cellulose Nanofibers/Ti3C2Tx MXene Aerogels/Epoxy Nanocomposites for Promising EMI Shielding.

In this work, 3D highly electrically conductive cellulose nanofibers (CNF)/Ti3C2Tx MXene aerogels (CTA) with aligned porous structures are fabricated by directional freezing followed by freeze-drying technique, and the thermally annealed CTA (TCTA)/epoxy nanocomposites are then fabricated by thermal annealing of CTA, subsequent vacuum-assisted impregnation and curing method. Results show that TCTA/epoxy nanocomposites possess 3D highly conductive networks with ultralow percolation threshold of 0.20 vol% Ti3C2Tx. When the volume fraction of Ti3C2Tx is 1.38 vol%, the electrical conductivity (σ), electromagnetic interference shielding effectiveness (EMI SE), and SE divided by thickness (SE/d) values of the TCTA/epoxy nanocomposites reach 1672 S m−1, 74 dB, and 37 dB mm−1, respectively, which are almost the highest values compared to those of polymer nanocomposites reported previously at the same filler content. In addition, compared to those of the samples without Ti3C2Tx, the storage modulus and heat-resistance index of TCTA/epoxy nanocomposites are enhanced to 9792.5 MPa and 310.7°C, increased by 62% and 6.9°C, respectively, presenting outstanding mechanical properties and thermal stabilities. The fabricated lightweight, easy-to-process, and shapeable TCTA/epoxy nanocomposites with superior EMI SE values, excellent mechanical properties, and thermal stabilities greatly broaden the applications of MXene-based polymer composites in the field of EMI shielding.

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.

Highly oriented three-dimensional structures of Fe3O4 decorated CNTs/reduced graphene oxide foam/epoxy nanocomposites against electromagnetic pollution

Three-dimensional Fe3O4 decorated carbon nanotubes/reduced graphene oxide foam/epoxy (3D Fe3O4-CNTs/rGF/EP) nanocomposites with highly oriented three-dimensional structures were fabricated by facile template method. Scanning electron microscope (SEM), transmission electron microscope (TEM), thermal gravimetric analyses (TGA), X-ray photoelectron spectroscopy (XPS) and Raman all proved the successfully graft of Fe3O4 onto the surface of CNTs and the formation of interconnected 3D highly aligned porous framework inner Fe3O4-CNTs/rGF. Owing to the presence of Fe3O4 and 3D nanohybrid framework, the obtained 3D Fe3O4-CNTs/rGF/EP nanocomposites with 0.24 wt% rGF and 2.76 wt% Fe3O4-CNTs showed remarkable electrical conductivity of 15.3 S/m and wonderful EMI SE value of 36 dB within the X-band range, almost 482% enhancement compared to physically blended Fe3O4-CNTs/EP nanocomposites without three-dimensional structure (∼6 dB). The excellent magnetic property and efficient 3D framework structures are considered as the main reasons for outstanding EMI shielding performances of the 3D Fe3O4-CNTs/rGF/EP nanocomposites.

Nanostructured ZrO₂/MWCNT Hybrid Materials: Fabrication, Characterization and Applications in Shielding of Electromagnetic Pollution.

ZrO₂/MWCNT nanocomposites have been prepared by simple refluxing method and characterized by X-ray diffraction (XRD). Fourier-transform infrared spectroscopy (FTIR), and Raman analysis suggests chemical interactions present between zirconia and Multiwalled carbon nanotube (MWCNT) in the as prepared nanocomposites. Electromagnetic inteference shielding efficiencies (EMI SE) for the nanocomposites were found to increase with increasing amount of MWCNT loading. Highest EMI SE value of 29.1-30.5 dB was obtained for nanocomposite containing 15 wt% loading of MWCNT in the microwave frequency range of 2-8 GHz. This optimum performance is due to several factors like highest percentage of intermolecular H-bonding, highly defective, interconnected network structure, high conductivity and dielectric permittivities of the nanocomposites.

Electromagnetic shielding property of carbon fiber felt made of different types of short-chopped carbon fibers

Three types of short-chopped carbon fibers (SCF), including polyacrylonitrile based T300, M40J and pitch-based XN-90-60s, were used to prepare SCF felts by wet-laid method with hydroxyethylcellulos as adhesive. Electromagnetic interference shielding effectiveness (EMI SE) in X band was investigated using waveguide method. It is found that stirring treatment leads to higher damaging degree of XN90 than those of T300 and M40J. M40J SCF felt with areal density of 42.5 g/m2 exhibits the highest EMI SE value of 66.7–71.4 dB. Absorption is believed to be the dominant EMI shielding mechanism for SCF felt, because of obvious advantage in absorption effectiveness compared with reflection effectiveness. T300 and M40J SCF felts have larger fiber stacking density, more contact points, more integrated conductive network and larger inner surface area, which lead to excellent absorption effectiveness. It shows that the type of SCF is a key factor for designing and preparing SCF felts.

PVC bead assisted selective dispersion of MWCNT for designing efficient electromagnetic interference shielding PVC/MWCNT nanocomposite with very low percolation threshold

The present study describes the electromagnetic interference shielding effectiveness (EMI SE) of poly (vinyl chloride) (PVC)/MWCNT nanocomposites prepared by solution blending in the presence of PVC beads and their corresponding electrically conductivity. Commercial PVC beads were added to the high viscous media of solution blended PVC-MWCNT during solvent evaporation of the prepared PVC/MWCNT nanocomposite. Addition of PVC beads increased the EMI SE and electrical conductivity values of the nanocomposite compared to the PVC/MWCNT nanocomposite without any PVC beads. Additionally, both EMI SE and electrical conductivity were also increased with increasing content of PVC bead at constant MWCNT loading in the nanocomposite. The insulating PVC bead regions are free from any MWCNT and acts as dispersed domains (excluded volume) which enhances effective concentration of MWCNT in the continuous PVC phase of the nanocomposites, and thus, play the key role to lower the percolation threshold, enhance the EMI SE and electrical conductivity values of the nanocomposite. The nonconductive PVC bead region in the nanocomposite acts as excluded volume that attenuates the microwave energy through multiple internal reflections by creating an impedance mismatch in the nanocomposites.

Inkjet Printing of Self‐Assembled 2D Titanium Carbide and Protein Electrodes for Stimuli‐Responsive Electromagnetic Shielding

Abstract2D titanium carbides (MXene) possess significant characteristics including high conductivity and electromagnetic interference shielding efficiency (EMI SE) that are important for applications in printed and flexible electronics. However, MXene‐based ink formulations are yet to be demonstrated for proper inkjet printing of MXene patterns. Here, tandem repeat synthetic proteins based on squid ring teeth (SRT) are employed as templates of molecular self‐assembly to engineer MXene inks that can be printed as stimuli‐responsive electrodes on various substrates including cellulose paper, glass, and flexible polyethylene terephthalate (PET). MXene electrodes printed on PET substrates are able to display electrical conductivity values as high as 1080 ± 175 S cm−1, which significantly exceeds electrical conductivity values of state‐of‐the‐art inkjet‐printed electrodes composed of other 2D materials including graphene (250 S cm−1) and reduced graphene oxide (340 S cm−1). Furthermore, this high electrical conductivity is sustained under excessive bending deformation. These flexible electrodes also exhibit effective EMI SE values reaching 50 dB at films with thicknesses of 1.35 µm, which mainly originate from their high electrical conductivity and layered structure.

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.