The effects of temperature and frequency on the dielectric properties, electromagnetic interference shielding and microwave-absorption of short carbon fiber/silica composites
TL;DR: In this paper, a dielectric spectroscopy of short carbon fiber/silica composite in the frequency range from 8.2 to 12.4 GHz at temperatures between 30 and 600°C has been performed.
About: This article is published in Carbon.The article was published on 2010-03-01. It has received 1540 citations till now. The article focuses on the topics: Dielectric & Reflection loss.
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TL;DR: In this paper, the authors evaluated the dielectric properties and microwave attenuation performances over the full X-band (8.2-12.4 GHz) at a wide temperature ranging from 100 to 500 °C.
961 citations
TL;DR: By considering good chemical homogeneity and microwave absorption, it is believed the as-fabricated Fe3O4@C composites can be promising candidates as highly effective microwave absorbers.
Abstract: Core–shell composites, Fe3O4@C, with 500 nm Fe3O4 microspheres as cores have been successfully prepared through in situ polymerization of phenolic resin on the Fe3O4 surface and subsequent high-temperature carbonization. The thickness of carbon shell, from 20 to 70 nm, can be well controlled by modulating the weight ratio of resorcinol and Fe3O4 microspheres. Carbothermic reduction has not been triggered at present conditions, thus the crystalline phase and magnetic property of Fe3O4 micropsheres can be well preserved during the carbonization process. Although carbon shells display amorphous nature, Raman spectra reveal that the presence of Fe3O4 micropsheres can promote their graphitization degree to a certain extent. Coating Fe3O4 microspheres with carbon shells will not only increase the complex permittivity but also improve characteristic impedance, leading to multiple relaxation processes in these composites, thus the microwave absorption properties of these composites are greatly enhanced. Very inte...
817 citations
TL;DR: Ferroferric oxide (Fe(3)O(4)) was selected as the phase in multiwalled carbon nanotube (MWCNT)-based composites for enhancing magnetic properties to obtain improved electromagnetic attenuation and exhibited enhanced magnetic properties coupled with increased dielectric properties.
Abstract: Light-weight nanocomposites filled with carbon nanotubes (CNTs) are developed for their significant potentials in electromagnetic shielding and attenuation for wide applications in electronics, communication devices, and specific parts in aircrafts and vehicles. Specifically, the introduction of a second phase into/onto CNTs for achieving CNT-based heterostructures has been widely pursued due to the enhancement in either dielectric loss or magnetic loss. In this work, ferroferric oxide (Fe(3)O(4)) was selected as the phase in multiwalled carbon nanotube (MWCNT)-based composites for enhancing magnetic properties to obtain improved electromagnetic attenuation. A direct comparison between the two-phase heterostructures (Fe(3)O(4)/MWCNTs) and polyaniline (PANI) coated Fe(3)O(4)/MWCNTs, namely, three-phase heterostructures (PANI/Fe(3)O(4)/MWCNTs), was made to investigate the interface influences of Fe(3)O(4) and PANI on the complex permittivity and permeability separately. Compared to PANI/Fe(3)O(4)/MWCNTs, Fe(3)O(4)/MWCNTs exhibited enhanced magnetic properties coupled with increased dielectric properties. Interfaces between MWCNTs and heterostructures were found to play a role in the corresponding properties. The evaluation of microwave absorption of their wax composites was carried out, and the comparison between Fe(3)O(4)/MWCNTs and PANI/Fe(3)O(4)/MWCNTs with respect to highly efficient microwave absorption and effective absorption bandwidth was discussed.
798 citations
TL;DR: Graphene networks with "well-sequencing genes" can serve as nanogenerators, thermally promoting electromagnetic wave absorption by 250%, with broadened bandwidth covering the whole investigated frequency, opening up an unexpected horizon for converting, storing, and reusing waste electromagnetic energy.
Abstract: Electromagnetic energy radiation is becoming a "health-killer" of living bodies, especially around industrial transformer substation and electricity pylon. Harvesting, converting, and storing waste energy for recycling are considered the ideal ways to control electromagnetic radiation. However, heat-generation and temperature-rising with performance degradation remain big problems. Herein, graphene-silica xerogel is dissected hierarchically from functions to "genes," thermally driven relaxation and charge transport, experimentally and theoretically, demonstrating a competitive synergy on energy conversion. A generic approach of "material genes sequencing" is proposed, tactfully transforming the negative effects of heat energy to superiority for switching self-powered and self-circulated electromagnetic devices, beneficial for waste energy harvesting, conversion, and storage. Graphene networks with "well-sequencing genes" (w = Pc /Pp > 0.2) can serve as nanogenerators, thermally promoting electromagnetic wave absorption by 250%, with broadened bandwidth covering the whole investigated frequency. This finding of nonionic energy conversion opens up an unexpected horizon for converting, storing, and reusing waste electromagnetic energy, providing the most promising way for governing electromagnetic pollution with self-powered and self-circulated electromagnetic devices.
719 citations
References
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Book•
01 Jan 1966
TL;DR: In this article, two-and three-dimensional boundary value problems are studied for two-dimensional waveguides with Cylindrical Conducting Boundaries (CCLB).
Abstract: Stationary Electric Fields. Stationary Magnetic Fields. Maxwell's Equations. The Electromagnetics of Circuits. Transmission Lines. Plane-Wave Propagation and Reflection. Two- and Three-Dimensional Boundary Value Problems. Waveguides with Cylindrical Conducting Boundaries. Special Waveguide Types. Resonant Cavities. Microwave Networks. Radiation. Electromagnetic Properties of Materials. Optics. Appendices. Index.
2,852 citations
"The effects of temperature and freq..." refers background in this paper
...According to the free electric theory [29], e00 could therefore be obtained to be e00 rðTÞ 2pe0f : ð8Þ...
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...[29] Ramo S, Whinnery JR, Duzer TV....
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TL;DR: In this paper, the absorption properties of CNT/crystalline Fe nanocomposites have been investigated and it was shown that the absorption property is due to the confinement of crystalline Fe in carbon nanoshells, deriving mainly from magnetic rather than electric effects.
Abstract: CNT/crystalline Fe nanocomposites (see Figure) have excellent microwave-absorption characteristics. This absorption property is shown to result from the confinement of crystalline Fe in carbon nanoshells, deriving mainly from magnetic rather than electric effects-the complex permittivity and permeability depend both on the shape and phase of the CNT/Fe nanocapsulates.
1,780 citations
"The effects of temperature and freq..." refers background in this paper
...out to investigate the dielectric property, electromagnetic interference (EMI) shielding and microwave-absorption [1–8] for protecting environment and sensitive circuits from the microwave radiation emitting from telecommunication apparatus....
[...]
...[1] Che RC, Peng LM, Duan XF, Chen Q, Liang XL....
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TL;DR: Carbon materials for electromagnetic interference (EMI) shielding are reviewed in this article, including composite materials, colloidal graphite and flexible graphite, and they include carbon filaments of submicron diameter.
1,676 citations
"The effects of temperature and freq..." refers background in this paper
...Although polarization plays a role in the imaginary part, free electrons have more effect on it, due to the good electrical conductivity of CFs [12,28]....
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...[12] Chung DDL....
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...Carbon materials, such as carbon nanotubes, carbon black, graphite flakes, carbon fibers (CFs) and filaments, have attracted increasing interest because of their potential applications in ideal absorbers [9–14]....
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...A number of research works have been carried out to study the microwave-absorption and related mechanisms of CFs [12]....
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...ous commercial and domestic applications [12,15–17]....
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TL;DR: In this paper, composites based on graphene-based sheets have been fabricated by incorporating solution-processable functionalized graphene into an epoxy matrix, and their electromagnetic interference (EMI) shielding studies were studied.
1,175 citations
"The effects of temperature and freq..." refers background in this paper
...Carbon materials, such as carbon nanotubes, carbon black, graphite flakes, carbon fibers (CFs) and filaments, have attracted increasing interest because of their potential applications in ideal absorbers [9–14]....
[...]
...[11] Liang JJ, Wang Y, Huang Y, Ma YF, Liu ZF, Cai FM, et al....
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TL;DR: The electromagnetic interference (EMI) shielding effectiveness measurements indicated that a novel carbon nanotube-polystyrene foam composite can be used as very effective, lightweight shielding materials.
Abstract: A novel carbon nanotube-polystyrene foam composite has been fabricated successfully. The electromagnetic interference (EMI) shielding effectiveness measurements indicated that such foam composites can be used as very effective, lightweight shielding materials. The correlation between the shielding effectiveness and electrical conductivity and the EMI shielding mechanism of such foam composites are also discussed.
1,152 citations
"The effects of temperature and freq..." refers background in this paper
...out to investigate the dielectric property, electromagnetic interference (EMI) shielding and microwave-absorption [1–8] for protecting environment and sensitive circuits from the microwave radiation emitting from telecommunication apparatus....
[...]
...[2] Yang YL, Gupta MC, Dudley KL, Lawrence RW....
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