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

Here a method for estimating the effective parameters (effective conductivity) of spherical aerogels of multilayer carbon nanotubes (CNTs) is proposed using the measured values of their polarizability and the wire medium model. While aerogels have a structure formed with tangles of curved nanotubes with chaotic contact distribution, the possibility to describe their electrophysical properties using the regular connected wire medium is estimated here. Calculations of the polarizability of regular structures consisting of copper and CNT wires of identical diameters (not less than 50 nm) for different models are performed. It is suggested that by selecting the parameters of a regular medium, it is possible to achieve the closeness of the polarizability values of samples of the same shape consisting of regular and irregular media. The calculated polarizability values of aerogels are consistent with the results of measurements of polarizability performed using the method of open resonators in the range 8–12 GHz. The possibility of estimating the electrophysical characteristics of carbon aerogels is considered for further modeling of the electromagnetic characteristics of composites based on them. The physical model of a spherical aerogel medium formed with tangles of curved nanotubes with chaotic contact distribution is considered. For this irregular structure, an equivalent wire regular structure is searched using the parameters described by known relations for wire media adapted for the case of nanowires. The equivalence criterion is an empirical characteristic – the measured value of the electrical polarizability of a spherical aerogel sample. The model makes it possible to estimate effective parameters of the aerogel media, in particular, the effective conductivity.