Electromagnetic interference shielding effectiveness of carbon materials

Progress in preparation, processing and applications of polyaniline

The growth in the application of electronic devices across a broad spectrum of military, industrial, commercial and consumer sectors has created a new form of pollution known as noise or radio frequency interference (RFI) or electromagnetic radiation or electromagnetic interference (EMI) that can cause interference or malfunctioning of equipment. Therefore, there is a greater need for the effective shielding of components from its adverse effects. This review surveys the shielding materials like metals, conducting plastics and conducting polymers for the control of electromagnetic radiations. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2009

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EMI shielding: Methods and materials—A review

Materials for the electromagnetic interference (EMI) shielding of electronics and radiation sources are reviewed, with emphasis on composite materials and resilient EMI gasket materials, which shield mainly by reflection of the radiation at a high frequency.

Materials for electromagnetic interference shielding

The rapid proliferation and elevated usage of electronic devices have led to a meteoritic rise in electronic pollutions such as electronic noise, electromagnetic interference (EMI) and radiofrequency interference (RFI) which leads to improper functioning of electronic devices. Metals and their alloys can serve as the best EMI shielding materials but their heavy weight, high cost and low corrosion resistance have limited their applications in EMI shielding. The emergence of flexible polymer composites have substituted the metal and metal alloy based EMI shielding materials due to their unique features such as light weight, excellent corrosion resistance, superior electrical, dielectric, thermal, mechanical and magnetic properties that are highly useful for suppressing the electromagnetic noises. In this review article, the EMI shielding effectiveness of flexible polymer composites comprising of metals and various forms of carbon nanofillers such as carbon black, carbon nanofibers, carbon nanotubes, graphite, graphene, graphene oxide, graphene nanosheets, graphene nanoribbons and graphene nanoplatelets have been deeply reviewed.

Recent advances in electromagnetic interference shielding properties of metal and carbon filler reinforced flexible polymer composites: A review

The effect of filler content, temperature, and frequency of the applied electric field on DC and AC electrical conductivities of composites of nickel-coated carbon fibers and polypropylene are considered. The impedance behavior and the dielectric properties of these composites were studied in the low frequency range 10 Hz–30 kHz. It was found that the volume electrical resistivity shows filler content and temperature dependence. The calculated activation energy of the thermal rate-process decreases with the filler concentration, while the shielding effectiveness increases. The overall observed permittivity of the composites increases with the filler concentration, and the dielectric behavior is discussed in terms of the space charge, electronic and interfacial polarization within the covered frequency range. It was observed that the AC conductivity is nearly independent of the frequency below 100 Hz and increases with frequency above this range. Finally, it was concluded that addition of nickel-coated carbon fibers could alter the electrical conduction mechanism and the polarization process of the polymeric matrix.

The electrical conductivity of polypropylene and nickel-coated carbon fiber composite

This paper reports results on the electrical properties of laminated epoxy composite containing 25 layers of carbon fibers in the form of mats. The dependence of the activation energy (calculated from DC resistivity measurements) on temperature reveals two independent conduction processes. The AC impedance is independent of the applied frequency below 75°C, and the real componet of the dielectric constant is also independent of temperature at high frequencies. The determined shielding effectiveness is dominated by the insertion loss. The observed optimum shielding effectiveness occurs at 30 mm spacing and applied frequency 9 GHz.

Electrical and electromagnetic shielding behavior of laminated epoxy–carbon fiber composite

Optical properties of epoxy-glass microballoons composite

A microwave bench operating in the frequency range 8–12 GHz (X-band) was used to investigate some of the electrical characteristics of the talc filled polypropylene composite. The impedance, return loss, and insertion loss are measured as a function of frequency in the X-band range. It was found that electromagnetic waves interact with the material via the impurities, inclusions and voids existing in the bulk composite. The impedance, return loss and insertion loss show relatively low frequency dependence. Also, the return loss and the impedance exhibit a resonance behaviour at 11.91 GHz. The results suggest that this composite material could be used in some microwave applications.

M. S. Ahmad

Papers

The electrical conductivity of polypropylene and nickel-coated carbon fiber composite

Electrical and electromagnetic shielding behavior of laminated epoxy–carbon fiber composite

Optical properties of epoxy-glass microballoons composite

Microwave properties of the talc filled polypropylene

The optical properties of polymethylmethacrylate polymer dispersed liquid crystals