Radio-wave electrical conductivity and absorption-dominant interaction with radio wave of exfoliated-graphite-based flexible graphite, with relevance to electromagnetic shielding and antennas

Guan, Hongtao; Chung, D.D.L.

doi:10.1016/j.carbon.2019.10.071

Cited by 54 publications

(18 citation statements)

References 63 publications

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“…Indeed, as shown by this research group, the permittivity is much lower for the discontinuous carbons than the continuous carbons [24][25][26][27][28][29]. As a result of the high permittivity, electromagnetic absorption is significant, as recently shown by the present authors in case of aluminum [30]. This observation in aluminum is in contrast to the widely accepted notion that nonmagnetic metals are ineffective for absorption, particularly when the thickness is larger than the skin depth.…”

Section: Introductionsupporting

confidence: 42%

“…The linear absorption coefficient a (a material property defined by Eq. (1), based on electromagnetic theory) [30] increases in the order FG \ steel \ Al (Fig. 6).…”

Section: Resultsmentioning

confidence: 93%

“…Among carbon materials, only flexible graphite can satisfy these requirements. The carbon material used is exfoliated-graphite-based flexible graphite, due to it high shielding effectiveness and availability in sheet form for EMI application [30]. In contrast, polymer-free graphene aerogel is not in a form that is suitable for EMI application [45].…”

Section: Introductionmentioning

confidence: 99%

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Absorption-dominant radio-wave attenuation loss of metals and graphite

Guan

Chung

2021

J Mater Sci

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Absorption-dominant radio-wave (0.2-2.0 GHz) attenuation loss is comparatively reported for materials of high electrical conductivity, namely metals (aluminum and steel) and graphite. These materials exhibit similarly high absorption loss (B 91.5%) and similarly low reflection loss (C 8.5%), both as fractions of the total loss in dB. The absorption loss is high (\ 55 dB) and the reflection loss is low (\ 10 dB) for both graphite and the metals. The absorptiondominant attenuation loss of these high-conductivity materials is in contrast to the notion that high conductivity (due to the high impedance mismatch with air) generally causes reflection-dominant attenuation loss. The metals and graphite are in foil form, with the graphite being thicker than the metals. The linear absorption coefficient (directly related to the absorption loss per unit thickness) is lower for graphite (B 93 mm -1 ) than the metals (B 394 mm -1 ), due to the greater thickness of the graphite. The absorption loss and fractional absorption loss contribution increase with increasing frequency, whereas the reflection loss decreases, as consistent with electromagnetic theory. On the other hand, from the viewpoint of the fractional loss in power, reflection dominates over absorption for all three materials in the entire frequency range. For shielding, the metals are more effective than graphite if the absorption loss per unit thickness (\ 3400 dB/mm) is considered. For stealth, graphite is advantageous to the metals in the low reflection loss, though it is disadvantageous in the low absorption loss per unit thickness.

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Section: Introductionsupporting

confidence: 42%

“…The linear absorption coefficient a (a material property defined by Eq. (1), based on electromagnetic theory) [30] increases in the order FG \ steel \ Al (Fig. 6).…”

Section: Resultsmentioning

confidence: 93%

Section: Introductionmentioning

confidence: 99%

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Absorption-dominant radio-wave attenuation loss of metals and graphite

Guan

Chung

2021

J Mater Sci

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“…Multilayer highly ordered pyrolytic graphite (HOPG) is scraped off to produce GN by mechanical exfoliation for which scotch tape, ultrasonic oscillations, and hot press techniques are being used. In the mechanical exfoliation process two types of normal force used to peel of the graphite and shear force utilize ball milling process [9,[22][23][24][25]. The liquid phase exfoliation (LPE) method includes three basic processes, those are dispersion of graphite in suitable solvent, exfoliation, and purifying where van der Waals forces break down by solvents and ultrasound.…”

Section: Synthesis Of Graphene (Gn) and Structural Featuresmentioning

confidence: 99%

Recent Advancement of Electromagnetic Interference (EMI) Shielding of Two Dimensional (2D) MXene and Graphene Aerogel Composites

2020

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The two Dimensional (2D) materials such as MXene and graphene, are most promising materials, as they have attractive properties and attract numerous application areas like sensors, supper capacitors, displays, wearable devices, batteries, and Electromagnetic Interference (EMI) shielding. The proliferation of wireless communication and smart electronic systems urge the world to develop light weight, flexible, cost effective EMI shielding materials. The MXene and graphene mixed with polymers, nanoparticles, carbon nanomaterial, nanowires, and ions are used to create materials with different structural features under different fabrication techniques. The aerogel based hybrid composites of MXene and graphene are critically reviewed and correlate with structure, role of size, thickness, effect of processing technique, and interfacial interaction in shielding efficiency. Further, freeze drying, pyrolysis and hydrothermal treatment is a powerful tool to create excellent EMI shielding aerogels. We present here a review of MXene and graphene with various polymers and nanomaterials and their EMI shielding performances. This will help to develop a more suitable composite for modern electronic systems.

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“…Graphite is a widely used material in various industrial applications due to its thermal stability at elevated temperatures, chemical resistance to aggressive aqueous solutions and high electrical conductivity 1 . Some of the common industrial examples of this includes manufacturing of melting crucibles, heating elements as well as in the processing of the bow of ballistic missiles and spacecraft for thermal protection 2 and for the production of various elements and tools of electric machines (brushes), electric vehicles and pumping equipment (e.g.…”

Section: Introductionmentioning

confidence: 99%

Novel hybrid method to additively manufacture denser graphite structures using Binder Jetting

Popov

Fleisher

Muller‐Kamskii

et al. 2021

Sci Rep

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This study introduces two hybrid processes integrating an additive manufacturing technique with post-processing treatments namely (i) Binder Jetting Printing (BJP) + Cold Isostatic Pressing (CIP) + cycle and (ii) BJP + cycle where cycle refers to a sequence of Impregnation—Drying—Pyrolysis. These two new processes yielded additively manufactured parts with higher density and reduced defects/porosities. As a testbed, we used these new processes to fabricate graphite structures. The samples produced by both methods were compared with each other and benchmarked to the samples produced by (a) BJP alone and (b) Traditional uniaxial pressing like compaction moulding. Various characterisation methods were used to investigate the microstructure and mechanical properties which showed that the porosity of hybrid manufactured samples reduces from 55% to a record 7%. This technological pathway is expected to create a new avalanche of industrial applications that are hitherto unexplored in the arena of hybrid additive manufacturing with BJP method.

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Radio-wave electrical conductivity and absorption-dominant interaction with radio wave of exfoliated-graphite-based flexible graphite, with relevance to electromagnetic shielding and antennas

Cited by 54 publications

References 63 publications

Absorption-dominant radio-wave attenuation loss of metals and graphite

Absorption-dominant radio-wave attenuation loss of metals and graphite

Recent Advancement of Electromagnetic Interference (EMI) Shielding of Two Dimensional (2D) MXene and Graphene Aerogel Composites

Novel hybrid method to additively manufacture denser graphite structures using Binder Jetting

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