Research Progress on Intrinsically Conductive Polymers and Conductive Polymer-Based Composites for Electromagnetic Shielding

Electromagnetic shielding materials are special materials that can effectively absorb and shield electromagnetic waves and protect electronic devices and electronic circuits from interference and damage by electromagnetic radiation. This paper presents the research progress of intrinsically conductive polymer materials and conductive polymer-based composites for electromagnetic shielding as well as an introduction to lightweight polymer composites with multicomponent systems. These materials have excellent electromagnetic interference shielding properties and have the advantages of electromagnetic wave absorption and higher electromagnetic shielding effectiveness compared with conventional electromagnetic shielding materials, but these materials still have their own shortcomings. Finally, the paper also discusses the future opportunities and challenges of intrinsically conductive polymers and composites containing a conductive polymer matrix for electromagnetic shielding applications.

A magnetic X-band frequency microwave nanoabsorbent made of iron oxide/halloysite nanostructures combined with polystyrene

A novel nanocomposite has been designed and fabricated through an in situ polymerization process, based on iron oxide nanoparticles (Fe3O4 NPs), halloysite nanotubes (HNTs), and polystyrene (PS). The prepared nanocomposite (formulated as Fe3O4/HNT-PS) has been fully characterized through various methods, and its applicability in microwave absorption was investigated by using some single-layer and bilayer pellets containing nanocomposite and resin. The efficiency of the Fe3O4/HNT-PS composite with different weight ratios and pellets with the thickness of 3.0 and 4.0 mm were examined. Vector network analysis (VNA) revealed that the microwave (12 GHz) can be noticeably absorbed by Fe3O4/HNT-60% PS particles in a bilayer structure with 4.0 mm thickness and 85% resin of the pellets, resulting in a microwave absorption value of ca. -26.9 dB. The observed bandwidth (RL < -10 dB) was about 1.27 GHz, where ca. 95% of the radiated wave is absorbed. Ultimately, due to low-cost raw materials and high performance of the presented absorbent system, the Fe3O4/HNT-PS nanocomposite and the construction of the presented bilayer system can be subjected to further investigations to test and compare with other compounds for industrialization.

High-performance electromagnetic wave absorption of NiCoFe/N-doped carbon composites with a Prussian blue analog (PBA) core at 2-18 GHz

Structure design and assembly control are the two key factors in designing new microwave absorbing materials and improving their electromagnetic wave absorption (EMWA) performance; however, balancing the coordination between these factors remains a great challenge. In this manuscript, a coprecipitation method and an in-situ polymerization method were used to construct nitrogen-carbon-doped popcorn-like porous nanocomposites (NiCoFe/NC). The metallic particles were encapsulated in approximately 10 layers of graphite carbon shells, and a NiCoFe/NC core-shell structure was formed. The EMWA properties of the NiCoFe/NC composites were adjusted by varying the divinylbenzene (DVB) to acrylonitrile (AN) content. The optimized NiCoFe/NC composite showed a minimum reflection loss of -57.5 dB and a maximum effective absorption bandwidth (EAB) of 5.44 GHz. The excellent EMWA properties of the NiCoFe/NC composites can be attributed to the synergistic effect among the core-shell structure, popcorn-like structure, magnetic metal, carbon and nitrogen. This effect leads to enhanced impedance matching, interface polarization, dipole polarization, multiple reflection and scattering in the composites. In this paper, an effective strategy for the preparation of high-performance magnetic/dielectric composites is provided by carefully designing a new microstructure.

Enhanced Microwave Absorption Bandwidth in Graphene-Encapsulated Iron Nanoparticles with Core-Shell Structure

Graphene-encapsulated iron nanoparticles (Fe(G)) hold great promise as microwave absorbers owing to the combined dielectric loss of the graphene shell and the magnetic loss of the ferromagnetic metal core. Transmission electron microscopy (TEM) revealed transition metal nanoparticles encapsulated by graphene layers. The microwave electromagnetic parameters and reflection loss (R) of the Fe(G) were investigated. Graphene provided Fe(G) with a distinctive dielectric behavior via interfacial polarizations taking place at the interface between the iron cores and the graphene shells. The R of Fe(G)/paraffin composites with different Fe(G) contents and coating thickness was simulated according to the transmit-line theory and the measured complex permittivity and permeability. The Fe(G)/paraffin composites showed an excellent microwave absorption with a minimum calculated R of −58 dB at 11 GHz and a 60 wt% Fe(G) loading. The composites showed a wide bandwidth (the bandwidth of less than −10 dB was about 11 GHz). The R of composites with 1–3 mm coating thickness was measured using the Arch method. The absorption position was in line with the calculated results, suggesting that the graphene-coated iron nanoparticles can generate a suitable electromagnetic match and provide an intense microwave absorption. Excellent Fe(G) microwave absorbers can be obtained by selecting optimum layer numbers and Fe(G) loadings in the composites.

The synthesis of CoxNi1−xFe2O4/multi-walled carbon nanotube nanocomposites and their photocatalytic performance

A series of Co_xNi_1−xFe₂O₄/multi-walled carbon nanotube (Co_xNi_1−xFe₂O₄/MWCNTs) nanocomposites as photocatalysts were successfully synthesized, where Co_xNi_1−xFe₂O₄ was synthesized via a one-step hydrothermal approach. Simultaneously, methylene blue (MB) was used as the research object to investigate the catalytic effect of the catalyst in the presence of hydrogen peroxide (H₂O₂). The results showed that all the photocatalysts exhibited enhanced catalytic activity compared to pure ferrite. In addition, compared with the other photocatalysts, the reaction time was greatly shortened a significantly higher removal rate was achieved using 3-CNF/MWCNTs. There was no significant decrease in photodegradation efficiency after three catalytic cycles, suggesting that Co_xNi_1−xFe₂O₄/MWCNTs are recyclable photocatalysts for wastewater treatment. Our results indicate that the Co_xNi_1−xFe₂O₄/MWCNT composite can be effectively applied for the removal of organic pollutants as a novel photocatalyst.

A series of Co_xNi_1−xFe₂O₄/multi-walled carbon nanotube (Co_xNi_1−xFe₂O₄/MWCNTs) nanocomposites as photocatalysts were successfully synthesized. The results implied that this composites can be effectively applied for the removal of organic pollutant as novel photocatalysts.

Microwave absorption properties of lightweight and flexible carbon fiber/magnetic particle composites

Hybridized-carbon-based materials with magnetic metals and oxides have attracted much attention because of their enhanced electromagnetic wave loss. In this study, magnetic particles were coated on the surface of carbon fibers by carbonizing in a nitrogen atmosphere. The morphology, structure, thermolysis, and wave-absorption performance of the carbon fiber/magnetic particle composite were determined. Results show that the in situ-formed magnetic particles (such as Fe₃O₄, NiFe₂O₄, CoFe₂O₄, and Ni₃Fe) are uniformly dispersed along the carbon-based fibers, which exhibit different wave absorption. The absorption of the carbon fiber/magnetic particle composite can be controlled by adjusting the species and concentration of the magnetic particle coating, which provides a new and effective way of endowing the magnetic-particle-coated carbon fibers with good microwave absorption properties.

Hybridized-carbon-based materials with magnetic metals and oxides have attracted much attention because of their enhanced electromagnetic wave loss.