Electromagnetic interference shielding effectiveness of carbon materials
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.
About: This article is published in Carbon.The article was published on 2001-02-01. It has received 1676 citations till now. The article focuses on the topics: Electromagnetic shielding & Graphite.
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TL;DR: In this article, a detailed analysis of the thermal expansion mechanism of graphite oxide to produce functionalized graphene sheets is provided, where it is shown that the decomposition rate of the epoxy and hydroxyl sites exceeds the diffusion rate of evolved gases, yielding pressures that exceed the van der Waals forces holding the graphene sheets together.
Abstract: A detailed analysis of the thermal expansion mechanism of graphite oxide to produce functionalized graphene sheets is provided. Exfoliation takes place when the decomposition rate of the epoxy and hydroxyl sites of graphite oxide exceeds the diffusion rate of the evolved gases, thus yielding pressures that exceed the van der Waals forces holding the graphene sheets together. A comparison of the Arrhenius dependence of the reaction rate against the calculated diffusion coefficient based on Knudsen diffusion suggests a critical temperature of 550 °C which must be exceeded for exfoliation to occur. As a result of their wrinkled nature, the functionalized and defective graphene sheets do not collapse back to graphite oxide but are highly agglomerated. After dispersion by ultrasonication in appropriate solvents, statistical analysis by atomic force microscopy shows that 80% of the observed flakes are single sheets.
3,340 citations
TL;DR: The mechanical flexibility and easy coating capability offered by MXenes and their composites enable them to shield surfaces of any shape while providing high EMI shielding efficiency.
Abstract: Materials with good flexibility and high conductivity that can provide electromagnetic interference (EMI) shielding with minimal thickness are highly desirable, especially if they can be easily processed into films. Two-dimensional metal carbides and nitrides, known as MXenes, combine metallic conductivity and hydrophilic surfaces. Here, we demonstrate the potential of several MXenes and their polymer composites for EMI shielding. A 45-micrometer-thick Ti3C2Tx film exhibited EMI shielding effectiveness of 92 decibels (>50 decibels for a 2.5-micrometer film), which is the highest among synthetic materials of comparable thickness produced to date. This performance originates from the excellent electrical conductivity of Ti3C2Tx films (4600 Siemens per centimeter) and multiple internal reflections from Ti3C2Tx flakes in free-standing films. The mechanical flexibility and easy coating capability offered by MXenes and their composites enable them to shield surfaces of any shape while providing high EMI shielding efficiency.
3,251 citations
TL;DR: It is believed that high electrical conductivity and connectivity of the conductive fi llers can improve EMI shielding performance.
Abstract: IO N The rapid development of modern electronics packed with highly integrated circuits generates severe electromagnetic radiation, which leads to harmful effects on highly sensitive precision electronic equipment as well as the living environment for human beings. Great effort has been made for the development of high-performance electromagnetic interference (EMI) shielding materials. In addition to high EMI shielding performance, being lightweight and fl exible are two other important technical requirements for effective and practical EMI shielding applications especially in areas of aircraft, aerospace, automobiles, and fast-growing next-generation fl exible electronics such as portable electronics and wearable devices. [ 1 ] Recently, electrically conductive polymer composites have received much attention for EMI shielding applications, [ 1–12 ] because of their light weight, resistance to corrosion, fl exibility, good processability, and low cost compared to the conventional metal-based materials. The EMI shielding effectiveness of the polymer composites depends critically on the intrinsic electrical conductivity, dielectric constant, magnetic permeability, aspect ratio, and content of conductive fi llers. [ 1–12 ] It is believed that high electrical conductivity and connectivity of the conductive fi llers can improve EMI shielding performance. [ 1 , 2 , 4 , 7 , 8 ]
1,621 citations
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.
1,540 citations
Cites background from "Electromagnetic interference shield..."
...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 article, the electromagnetic interference (EMI) shielding mechanisms of multi-walled carbon nanotube (MWCNT)/polymer composites were analyzed experimentally and theoretically.
1,222 citations
Cites background from "Electromagnetic interference shield..."
...[3] Chung DDL....
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...A device is considered electromagnetically compatible with its surrounding if it does not interfere with other devices or itself, and it does not affected by emissions from other devices [1–3]....
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...Even though EMI SE of CPCs increases with increase in composite conductivity, some researchers believe that there is no scientific relation between EMI SE and polymer composite conductivity, since conductivity requires connectivity while shielding does not [3,4,26]....
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...Three mechanisms have been reported to be involved in EMI shielding, namely: reflection, absorption and multiple-reflection [1,3,26–28]....
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References
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TL;DR: In this article, a carbon-matrix composite with continuous carbon-fibers was found to be an excellent electromagnetic interference (EMI) shielding material with shielding effectiveness 124 dB, low surface impedance and high reflectivity in the frequency range from 0.3 MHz to 1.5 GHz.
Abstract: A carbon-matrix composite with continuous carbon-fibers was found to be an excellent electromagnetic interference (EMI) shielding material with shielding effectiveness 124 dB, low surface impedance and high reflectivity in the frequency range from 0.3 MHz to 1.5 GHz. The shielding effectiveness of polymer-matrix composites with continuous carbon-fibers was less and that of polymer-matrix composites with discontinuous fillers was even less. The addition of 2.9 vol.% discontinuous 0.1 μm diameter carbon-filaments between the layers of conventional 7 μm diameter continuous carbon-fibers in a composite degraded the shielding effectiveness. The dominant mechanism of EMI shielding for both carbon-matrix and polymer-matrix continuous carbon-fiber composites is reflection.
352 citations
24 Jul 1994
TL;DR: In this paper, the degradation kinetics of the electrical conductivity of polypyrrole fabrics have been investigated and found to proceed by multiple rate laws, including diffusion controlled and diffusion-limited degradation.
Abstract: The chemical polymerization of pyrrole in the presence of textile substrates results in the formation of electrically conducting, polypyrrole coated fabrics. Applications of these materials include microwave attenuation, static charge dissipation, and EMI shielding. The degradation kinetics of the electrical conductivity of these materials has been investigated and found to proceed by multiple rate laws. In the initial stages of conductivity loss, a diffusion controlled mechanism predominates, where oxygen diffusion into the polypyrrole film is rate limiting. At longer times, the degradation follows a simple first-order decay. The dopant anion employed during polymerization has a profound influence on the stability of the resulting film, and SEM analysis indicate that film morphology plays an important role in this effect. In the absence of oxygen, conductivity loss is significantly slower and displays a strong dependence on chloride content.
260 citations
TL;DR: In this paper, the processing of nickel filaments of 0.4 Μm diameter gives polyethersulfone-matrix composites with high electromagnetic interference shielding effectiveness, high reflection coefficient and low surface impedance at 1-2 GHz.
Abstract: The processing of nickel filaments of 0.4 Μm diameter gives polyethersulfone-matrix composites with high electromagnetic interference shielding effectiveness, high reflection coefficient and low surface impedance at 1-2 GHz. With 7 vol.% nickel filaments, the composite exhibited shielding effectiveness 87 dB (compared to 90 dB for solid copper), surface impedance 1.2 Ω (same as for solid copper), tensile strength 52 MPa, modulus 5 GPa, ductility 1.0%, and density 1.87 g/cm3.
211 citations
TL;DR: In this paper, the authors measured the electrical interference shielding efficiency of polyaniline-Camphor Sulfonic acid (PCA) films in the near-field and far-field with a dual-chamber box and a transmission line method in the frequency range 0.1-1000 MHz.
201 citations
Journal Article•
TL;DR: The processing of nickel filaments of 0.4 Μm diameter gives polyethersulfone-matrix composites with high electromagnetic interference shielding effectiveness, high reflection coefficient and low surface impedance at 1-2 GHz.
Abstract: Nickel filaments of 0.4 μm diameter gave polyethersulfone-matrix composites with high electromagnetic interference shielding effectiveness and low surface impedance at 1–2 GHz. With 7 vol.% nickel filaments, the composite exhibited shielding effectiveness 87 dB (compared to 90 dB for solid copper), surface impedance 1.2 Ω (same as for solid copper), tensile strength 52 MPa, modulus 5 GPa, ductility 1.0% and density 1.87 g/cm3. The low surface impedance is valuable for microwave waveguides.
159 citations