Electromagnetic Interaction Between Spherical Aerogels of Multi‐Walled Carbon Nanotubes

Abstract

Lightweight materials for efficient electromagnetic interference shielding over a wide range of frequency are of great interest. Aerogels of multi-walled carbon nanotubes (MWCNTs) distributed in a dielectric matrix may interact effectively with electromagnetic radiation. Moreover, being arranged in specific patterns, they can also provide metamaterial characteristics (e.g., negative refractive index). In the present paper, we have studied the interaction between two spheres of the carbon nanotube aerogels in order to obtain a comprehensive basis for producing periodic 2D and 3D structures of such aerogel spheres in a dielectric matrix. We have extended the open resonator technique to the case of two units of MWCNT aerogels in order to reveal the interaction between them. The performance of the system depends on the orientation of the electric field to the axis of the aerogel cluster: MWCNT aerogel spheres (d ¼ 4.5 mm) interact considerably at the gap between spheres $0.2λ (11.6 GHz) for perpendicular orientation, while, in case of axial orientation, the interaction is negligible even at the distances close to the contact between aerogels ($0.02λ). Additionally, the cluster of two carbon nanotube aerogel spheres provides the polarizability close to that of copper spheres while having only 1% of their weight.

Fe–Mo and Co–Mo Catalysts with Varying Composition for Multi‐Walled Carbon Nanotube Growth

“…Carbon nanotubes (CNTs) are among the key nanostructures that have been actively developed and investigated during the last two decades due to their unique electrophysical properties, such as high electrical and thermal conductivity, high mechanical strength, relative chemical inertness, the ability to absorb electromagnetic radiation over a wide range of wavelengths, etc. CNTs are considered as promising candidates for many potential applications such as nanocomposite materials, catalyst and catalyst supports, field emitters, sensors, energy storage devices, hydrogen storage, fuel cells, nanoelectronics, bionanomaterials, and nanomedicine . Generally, most of multi‐walled carbon nanotubes (MWCNTs) are used to improve the physical and chemical characteristics of numerous composite materials based on polymeric, metal and oxide matrices .…”

Interaction of Multiwalled Carbon Nanotube Aerogels with Quasi‐Optical Terahertz Beams

“…It was interesting to compare this value with any independent data on the average distance between nanotubes in the aerogel. Unfortunately the analysis of average distances between MWCNTs using SEM images of aerogel is a complex task that requires obtaining tomographic images and extremely time‐consuming statistical analysis due to the tangled structure of curved nanotubes. So we used the analysis based on the volume fraction of nanotubes.…”

“…This model is semi‐empirical since the experimentally determined polarizability of a spherical sample is used to estimate the electrophysical parameters of the aerogel environment. An experimental study of spherical aerogels in the gigahertz range (8–12 GHz) showed that, despite the high conductivity of CNTs in the aerogel media and high density of their packages compared to the wavelength, effective parameters of aerogels noticeably differ from those of metals.…”

The Usage of Conducting Wire Sphere Models for the Estimation of Electrophysical Properties of Multiwalled Carbon Nanotube Spherical Aerogels

“…There are known models of a regular wire medium formed by macroscopic conductors, whereas for nanoscale objects such models are not available. We propose to construct such models by applying a macroscopic approach to nanoscale copper conductors, since their electrophysical properties are known and experimentally confirmed . The problem is that the wire medium models use bulk conductors, while the MWCNTs are considered as 2D objects, so a transition to some effective conductivity is required.…”