Lightweight and flexible conducting polymer sponges and hydrogels for electromagnetic interference shielding

The electromagnetic interference (EMI) shielding of Sm-containing magnesium alloys in the 30–1500 MHz testing frequency range was investigated by coaxial cable method. The results demonstrated that Mg–3Zn alloys displayed the best electromagnetic shielding property. When 0.5 wt% of Zr was added for crystal grain refinement, the shielding effectiveness (SE) was apparently reduced. The addition of the rare earth element Sm in ZK magnesium alloys can improve the electromagnetic interference shielding of magnesium alloys. The main reason for the differences in electromagnetic interference shielding of magnesium alloys was the change in conductivity. The addition of Zr in Mg–Zn alloys can refine the grains and consequently improve the grain boundary area significantly. Therefore, the number of irregularly arranged atoms at the grain boundaries increased, decreasing the conductivity of magnesium alloys and leading to a decrease in the electromagnetic interference shielding. Following the Sm addition, the Mg–Zn–Sm phase was precipitated at the grain boundaries and in cores. The precipitation of Sm-containing rare earth phases could consume the solid-soluted Zn atoms within the Mg, resulting in an increase in electrical conductivity and electromagnetic interference shielding improvement.

Silver (Ag)/carbonyl iron particles (CIPs) were prepared by electroless plating successfully to improve the electromagnetic interference (EMI) shielding and antioxidation properties of CIPs. The microstructure, phase composition, thermogravimetric (TG), electromagnetic and EMI shielding properties were analyzed respectively. Experimental results show that Ag particles were uniformly distributed on the surface of CIPs. TG results show the apparent weight gain temperature of Ag/CIPs was deferred compared with the weight gain temperature of CIPs. The total EMI SE value of Ag/CIPs/EP composite reaches about 36 dB with thickness 1.5 mm, which is far superior to the value of CIPs/EP composite. The EMI shielding result shows such Ag/CIPs composite material has an outstanding EMI shielding effect in the measured frequency band (8.2 GHz–12.4 GHz).

Comparative study of electromagnetic interference shielding properties of injection molded versus compression molded multi-walled carbon nanotube/polystyrene composites

Multilayer composite films with enhanced electromagnetic interference shielding and thermal management properties based on bamboo cellulose nanofibers.

Enhancing structural analysis and electromagnetic shielding in carbon foam composites with applications in concrete integrating XGBoost machine learning, carbon nanotubes, and montmorillonite

Preparing lightweight and versatile products is the unremitting goal of industry to save resources and energy. Lightweight carbon fiber reinforced polypropylene (CF/PP) composite foams with high‐performance electromagnetic interference (EMI) shielding materials were fabricated by microcellular injection molding (MIM) technology. The average length and distribution of CF in CF/PP composite foams were examined. Thanks to the introduction of foaming process, the average CF length of composite foams was 33.98% longer than that of solids, which effectively enhanced the electrical conductivity and EMI shielding properties. The effect of shot size, gas content, and injection rate on the electrical conductivity and EMI properties was investigated. With melt shot size of 2/3 of the cavity volume, gas content of 0.5 wt% N2 and injection rate of 100 mm/s, optimal cellular structure of the composite material was obtained. The EMI shielding effectiveness (SE) reaches 36.94 dB, which is the highest value achieved by using MIM technology to the best of the authors' knowledge. In addition, the mechanical properties of cellular structure can still maintain good values, with the tensile strength and impact strength improved by 15.3% and 14.03%, respectively.

We herein report the enhancement of thermal, electrical, electromagnetic interference (EMI) shielding, and mechanical performance of polyethylene (PE) nanocomposites by the introduction of non‐covalently modified multi‐walled carbon nanotube (MWCNT) and ethylene‐glycidyl methacrylate (EGMA) copolymer. For this purpose, benzylacetic acid‐functionalized MWCNT (BA‐M) is prepared by ball milling, and it is melt‐mixed with EGMA to prepare a masterbatch. The masterbatch is then melt‐compounded with neat PE to manufacture a series of PE/EGMA/BA‐M nanocomposites with 0.5–5 wt% MWCNTs. Electron microscopic and spectroscopic analyses confirm the successful fabrication of non‐covalently functionalized BA‐M, the uniform dispersity of MWCNTs in the PE matrix, and the chemical reactions between the carboxylic acid groups of BA‐M and the epoxy group of EGMA in the nanocomposites. Scanning calorimetric data reveals that BA‐M acts as an efficient nucleating agent for the crystallization of PE. The excellent dispersity and robust interfacial bonding of BA‐M in the PE matrix result in improved electrical and EMI shielding properties in PE/EGMA/BA‐M nanocomposites. Furthermore, the tensile strength, initial modulus, and impact strength of the nanocomposites gradually rise as the BA‐M content increases. Thus, the PE/EGMA/BA‐M nanocomposite containing 5 wt% MWCNT achieves excellent performance of EMI shielding effectiveness of ~14.7 dB/mm, tensile strength of ~34.5 MPa, initial modulus of ~295.7 MPa, and impact strength of ~539.9 J/m, which represent enhancements of ~265%, ~40%, ~82%, and ~452%, respectively, compared to pristine PE.Highlights Non‐covalently modified MWCNT (BA‐M) was prepared by facile ball milling. PE nanocomposites with BA‐M and EGMA were prepared by masterbatch melt‐mixing. Excellent dispersity and interfacial bonding of MWCNT in the PE matrix were attained. Tensile strength and initial modulus of the nanocomposites were highly improved. EMI shielding effectiveness of the nanocomposite with 5 wt% MWCNT was ~14.7 dB/mm.

Recent experiments have revealed two distinct percolation phenomena in carbon nanotube (CNT)/polymer nanocomposites: one is associated with the electrical conductivity and the other is with the electromagnetic interference (EMI) shielding. At present, however, no theories seem to exist that can simultaneously predict their percolation thresholds and the associated conductivity and EMI curves. In this work, we present an effective-medium theory with electrical and magnetic interface effects to calculate the overall conductivity of a generally agglomerated nanocomposite and invoke a solution to Maxwell’s equations to calculate the EMI shielding effectiveness. In this process, two complex quantities, the complex electrical conductivity and complex magnetic permeability, are adopted as the homogenization parameters, and a two-scale model with CNT-rich and CNT-poor regions is utilized to depict the progressive formation of CNT agglomeration. We demonstrated that there is indeed a clear existence of two separate percolative behaviors and showed that, consistent with the experimental data of poly-L-lactic acid (PLLA)/multi-walled carbon nanotube (MWCNT) nanocomposites, the electrical percolation threshold is lower than the EMI shielding percolation threshold. The predicted conductivity and EMI shielding curves are also in close agreement with experimental data. We further disclosed that the percolative behavior of EMI shielding in the overall CNT/polymer nanocomposite can be illustrated by the establishment of connective filler networks in the CNT-poor region. It is believed that the present research can provide directions for the design of CNT/polymer nanocomposites in the EMI shielding components.

Composites with different arrangements of continuous carbon fibers, with the poly(ethylene terephthalate)-spunbond nonwoven fabrics as substrates, were fabricated for optimization of electromagnetic interference shielding performance. Effects of these structural parameters, including array spacing, the number of layers, and overlap angle, were investigated within the frequency band of 30 MHz–1.5 GHz, which includes the major electromagnetic wave frequency from daily electronic device or apparatus. Within 30 MHz–750 MHz, shielding effectiveness was fortified with the decrease of array spacing and the increase of the number of layers owning to the increase of the continuous carbon fiber content. Whereas, within the frequency band of 750 MHz–1.5 GHz, the number of layers presented little effect on the shielding performance reasoning that the impact of continuous carbon fiber orientation was more significant than that of continuous carbon fiber content. While the array spacing was 8 mm and the maximum value of shielding effectiveness for the two-layer composites was 46.8 decibel at frequency of 1000 MHz. For multilayer composites, shielding performance was improved by synergistic effects of overlap angle and array spacing. Hence, composite with three layers, array spacing of 12 mm and overlap angle of 0°–0°–45° achieved the highest electromagnetic interference shielding properties of 60.49 decibel, corresponding frequency of 1.0 GHz. The results of this work demonstrated a potentially efficient and economical way to fabricate the electromagnetic interference shielding composites with less content of continuous carbon fiber and to simultaneously achieve superb shielding performance. This work will be significant for further study in the electromagnetic interference shielding composite industry in the near future.

Electromagnetic interference shielding and absorption properties of CF/PDA/Fe3O4 hybrid composites

This study proposes a novel method of fabricating nanohybrid particles composed of carbon nanotubes and carbonyl iron powder (CNT@CIP), which are then embedded in a polymer for use as electromagnetic interference (EMI) shielding. First, a method of fabricating CNT@CIP nanohybrid particles is introduced, and their formation is verified using characterization tools such as zeta potential analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy, and Raman spectroscopy. Then, the CNT@CIP nanohybrid particles are incorporated into a polymeric matrix. The electrical conductivity and EMI shielding capability of the resulting composites are systematically investigated. According to the experimental results, it can be found that the electrical conductivity and EMI shielding effectiveness increase with increasing of CNT@CIP nanohybrid particles contents. In addition, they are improved by the alignment of the CNT@CIP hybrid particles caused by the magnetization curing, reducing the amount of electrically conductive fillers required. Consequently, utilization of CNT@CIP nanohybrid particles and magnetization curing can greatly improve the electrical conductivity and EMI shielding capability, showing their potential as EMI shielding composites in various practical applications.

Rapid advances in electronics has led to a significant increase in electromagnetic radiation from electronic devices, posing potential threats to human health. Developing lightweight, high‐performance, and green electromagnetic interference (EMI) shields is crucial for mitigating electromagnetic pollution. EMI shielding research over the last decade has provided numerous alternatives to metal shields using carbon nanotubes, graphene, MXenes, etc. However, these shields are mostly reflection‐dominant, just like metals, due to their high conductivity, offering hardly any remedy to the secondary pollution issue. Thus, the research focus has shifted to reduce the reflection and develop absorption‐dominant EMI shields. A green index, defined as the ratio of absorption over reflection, must be well over 1 and preferably even as high as 10. This article provides an in‐depth review of the theoretical foundations of EMI shielding, highlighting various loss mechanisms, along with recent advances in absorption‐dominant EMI shields. Various strategies to reduce reflection through better impedance matching, including foam and aerogels, semiconductor fillers, magnetic fillers, gradient conductivity shields, conductivity‐magnetic dual gradient, segregated structures, printed shields, metastructures and others are discussed . Finally, design strategies of absorption‐dominant shields are analyzed, and current challenges and potential pathways are outlined to guide future advancements and facilitate practical implementation.

In this study, a nanocomposite of reduced graphene oxide (RGO) nanofiller-reinforcement poly(lactic acid) (PLA)/poly(ethylene glycol) (PEG) matrix was prepared via the melt blending method. The flexibility of PLA was improved by blending the polymer with a PEG plasticizer as a second polymer. To enhance the electromagnetic interference shielding properties of the nanocomposite, different RGO wt % were combined with the PLA/PEG blend. Using Fourier-transform infrared (FT-IR) spectroscopy, field emission scanning electron microscopy (FE-SEM) and X-ray diffraction, the structural, microstructure, and morphological properties of the polymer and the RGO/PLA/PEG nanocomposites were examined. These studies showed that the RGO addition did not considerably affect the crystallinity of the resulting nanomaterials. Thermal analysis (TGA) reveals that the addition of RGO highly improved the thermal stability of PLA/PEG nanocomposites. The dielectric properties and electromagnetic interference shielding effectiveness of the synthesized nanocomposites were calculated and showed a higher SE total value than the target value (20 dB). On the other hand, the results showed an increased power loss by increasing the frequency and conversely decreased with an increased percentage of filler.

Rapid advancements in nanotechnology have led to electronic devices with densely integrated components, contributing to increased Electromagnetic Interference (EMI) pollution. EMI, a high-frequency electromagnetic signal, disrupts electronic circuits and can originate from external devices or within the affected component itself. Beyond causing electronic malfunctions, EMI exposure leads to health risks. This review discusses the Electromagnetic Interference Shielding (EMIS) mechanisms, such as reflection, absorption, and multiple reflection. It also examines recent advancements in EMIS materials, based on carbon-based, polymer-based, and carbon-polymer hybrid nanocomposites. It also investigates carbon-based materials, carbon nanotubes, graphene, and activated carbon due to their high electrical conductivity and EMI absorption properties. Polymer-based composites, incorporated with conductive polymers and metal oxides, are evaluated for their flexibility and processability. Carbon-polymer hybrid nanocomposites are highlighted due to their synergistic effects, combining the strengths of both components to achieve a high EMIS performance. This review also addresses the materials that are sustainable and recyclable for EMIS applications.

Dual-functional magnetic/dielectric Fe/Fe3C@C composites were fabricated by pyrolysis of MIL-88B (Fe) in an Ar atmosphere, which was used for microwave absorption and electromagnetic interference (EMI) shielding. The Fe/Fe3C nanocrystals were completely encapsulated in crystalline carbon, which can improve oxidation resistance capacity. Owing to remarkable impedance matching and strong attenuation constants, the Fe/Fe3C@C composites show an optimal reflection loss (RL) value of −56.4 dB at 14.0 GHz and a broad effective absorption bandwidth (RL ⩽ −10 dB) of 4.8 GHz when the filling ratio and absorber thickness are only 20 wt% and 1.9 mm, respectively. Resulting from the high conductivity of crystalline carbon, magnetic loss of Fe/Fe3C, and core–shell structure, the Fe/Fe3C@C composites also show remarkable EMI shielding properties at the X band, which are enhanced by increasing the filling ratio of the Fe/Fe3C@C composites. When the filling ratio is 50 wt%, the EMI shielding efficiency can reach 35 dB. This work suggests that magnetic/dielectric Fe/Fe3C@C is a good candidate in microwave absorption and EMI shielding.