Modeling the Electromagnetic Scattering Characteristics of Carbon Nanotube Composites Characterized by 3-D Tomographic Transmission Electron Microscopy

Ahmed M Hassan,Estelle Cohen,Bharath Natarajan,Edward J Garboczi,Brian L Wardle,Noa Lachman,Renu Sharma,Itai Y Stein,J Alexander Liddle,Spencer On,Md Khadimul Islam

doi:10.1109/ojap.2020.2987879

Abstract

In all prior electromagnetic modeling studies of carbon nanotube (CNT) composites, the exact three-dimensional (3D) shape and spatial distribution of the CNTs in the composite were unknown. Therefore, simplifying assumptions had to be made regarding the CNT distributions. The effect of such assumptions on the electromagnetic response of CNT composites has not been quantified. Recent advances in electron-tomography and image analysis have allowed the generation of 3D maps of multi-walled carbon nanotube (MWCNT) distributions with sub-nanometer resolution. In this work, the electromagnetic responses of experimentally mapped 3D structures of aligned-CNT polymer nanocomposites were calculated using both full-wave electromagnetic solvers and dilute-limit Effective Medium Approximations (EMA). Our results show that the electromagnetic response calculated using the full-wave solver exhibits additional resonances that are absent in the response calculated using the dilute-limit EMA. This difference is due to the strong electromagnetic coupling between adjacent MWCNTs, within five CNT radii, of each other. Using the mapped 3D MWCNTs, we also studied the anisotropy in the electromagnetic response of the composites and showed that it increases with the MWCNT volume fraction. The full-wave analysis presented in this work provides a more accurate understanding of the electromagnetic reflection and anisotropy of CNT composites.

Highlights

C ARBON nanotubes (CNTs) are considered the additive of choice in a wide range of applications due to their exceptional electrical, mechanical, chemical, and biological properties
We study the electromagnetic response of simple multi-walled carbon nanotube (MWCNT) distributions to explain the results achieved from the reconstructed MWCNT distributions
We use the reconstructed 3D MWCNT distributions to investigate the dependence of the electromagnetic response of the composites on the direction of the incident field

Summary

Introduction

C ARBON nanotubes (CNTs) are considered the additive of choice in a wide range of applications due to their exceptional electrical, mechanical, chemical, and biological properties. CNTs are added to a polymer matrix to create a composite with enhanced properties that cannot be achieved by the components on their own. One of the recent applications of CNT composites is as advanced electromagnetic shielding films [1]. CNTs are added to a low-density polymer, which is transparent in its undoped state to microwave radiation, to create a light and tunable composite with high shielding effectiveness [1], [2]. CNT composites have recently been proposed for thermotherapy [3]. Additional examples can be found in several reviews such as in [7], [8]

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