Absorption Dominated Directional Electromagnetic Interference Shielding through Asymmetry in a Multilayered Construct with an Exceptionally High Green Index

Sushmita, K and Ghosh, D and Nilawar, S and Bose, S (2022) Absorption Dominated Directional Electromagnetic Interference Shielding through Asymmetry in a Multilayered Construct with an Exceptionally High Green Index. In: ACS Applied Materials and Interfaces, 14 (43). pp. 49140-49157.

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Abstract

Fabricating green electromagnetic interference (EMI) shields is the need of the hour because strong secondary reflections in the vicinity of the shield adversely affect the environment and the reliability of the neighboring devices. To this end, the present work aims to maximize the absorption-based EMI shielding through a multilayered construct comprising a porous structure (pore size less than λ/5), a highly conducting entity, and a layer to match the impedance. The elements of this construct were positioned so that the incoming electromagnetic (EM) radiation interacts with the other layers of the construct before the conducting entity. This positioning of the layers in the construct offers a high green shielding index (gs) and low reflection coefficient (R ∼0.1) with an exceptionally high percent absorption (up to 99%). Polyurethane (PU) foams were fabricated using the salt-leaching technique and strategically positioned with carbon nanotube (CNT) papers and polycarbonate (PC)-based films to obtain symmetric and asymmetric constructs. These structures were then employed to gain mechanistic insight into the directional dependency of shielding performance, gs, and heat dissipation ability. Interestingly, maximum total shielding effectiveness (SET) of -52 dB (88% absorption @8.2 GHz) and specific shielding effectiveness/thickness (SSEt) of -373 dB/cm2g were achieved for a symmetric construct whereas, for the asymmetric construct, the SET and SSEt were -37 dB and -280 dB/cm2g, respectively, with an exceptionally high gs of 8.6, the highest reported so far. The asymmetricity in the construct led to directional dependence of the absorption component (% SEA, shielding effectiveness due to absorption) and heat dissipation, primarily governed by the electrical and thermal conductivity gradient, respectively. This study opens new avenues in this field and reports constructs with an exceptionally high green index.

Item Type:	Journal Article
Publication:	ACS Applied Materials and Interfaces
Publisher:	American Chemical Society
Additional Information:	The copyright for this article belongs to American Chemical Society.
Keywords:	Carbon films; Carbon nanotubes; Electromagnetic pulse; Electromagnetic shielding; Electromagnetic wave interference; Foams; Magnetic shielding; Pore size; Signal interference, Carbon nanotube paper; Electromagnetic interference shielding; Green indices; Leaching techniques; Multi-layered; Polyurethane Foam; Porous structures; Salt leaching; Shielding effectiveness; Symmetrics, Polyurethanes
Department/Centre:	Division of Mechanical Sciences > Materials Engineering (formerly Metallurgy) Division of Interdisciplinary Sciences > Centre for Nano Science and Engineering
Date Deposited:	20 Nov 2022 07:09
Last Modified:	20 Nov 2022 07:09
URI:	https://eprints.iisc.ac.in/id/eprint/77902

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