Microwave absorption in nanocomposite material of magnetically functionalized carbon nanotubes

Abstract

The interaction of electromagnetic radiation in X and Ka bands with magnetic nanocomposite of disordered carbon nanotubes arrays has been investigated both experimentally and theoretically. Samples were synthesized on the quartz reactor walls by decomposition of ferrocene and xylene which provided random intercalation of iron phase nanoparticles in carbon nanotube array. The exhaustive characterization of the samples by means of the scanning electron microscopy, Raman spectroscopy, and x-ray photoemission spectroscopy was performed. It was found that the absorption of the electromagnetic wave monotonically increases with the frequency. To describe these experimental data, we extended the Bruggeman effective medium theory to a more complex case of a magnetic nanocomposite with randomly distributed spherical ferromagnetic nanoparticles in a conducting medium. The essential feature of the developed model is the consideration of the complex nature of the studied material. In particular, such important parameters as magnetic and dielectric properties of both the carbon nanotube medium and the nanoparticles, the volume concentration and the dimensions of the nanoparticles, the wave impedance of the resistive-capacitive shells of the conductive nanoparticles are explicitly taken into account in our model. Moreover, analysing the experimental results, we were able to obtain the frequency dependencies of permittivity and permeability of the studied nanocomposite.

Interaction of electromagnetic radiation in the 20–200 GHz frequency range with arrays of carbon nanotubes with ferromagnetic nanoparticles

“…Under standard FCCVD conditions (i.e., synthesis temperature: 1150 K, ferrocene concentration: 5-10 wt %, injection rate of the Ar carrier gas: 100 cm3/min, growth duration: 1 min), the multiwall CNTs are formed. The height of the structure is approximately 50 μm and the average CNT diameter is less than 40 nm [8]. The conductivity of such samples is usually in the range of 100-120 (Ω·m)−1 at room temperature [8] and at liquid helium temperature, this decreases to 40-50 (Ω·m)−1.…”

“…Based on a previously developed approach [8], in this paper, the interaction of EMR with a CNT-based nanocomposite in the frequency range 20-200 GHz is theoretically studied. Special attention is given to the role of the resonance resistive-inductive-capacitive (RiLiC i) circuits, which leads to a deeper understanding of the problem.…”

“…In particular, the interaction of electromagnetic radiation (EMR) with CNT-based magnetic nanocomposites is developed in several directions [4,5,6,7,8]. One of the main problems is related to the elucidation of the absorption mechanisms of the EMR by such complex nanocomposites composed of a porous carbon matrix, ferromagnetic nanoparticles and the interfaces between them [8].…”

“…New magnetic nanocomposites based on carbon nanotubes (CNTs) [ 1,2,3] are very promising for high frequency applications [ 4,5,6,7,8,9,10,11,12,13,14] such as transmission lines, mixtures and detectors [15,16,17], antennas and absorbing materials [18,19,20,21,22,23,24,25,26]. The absorption properties of CNT-based nanocomposites are primarily determined by the dielectric loss [27].…”

Synergistic effect of magnetite nanoparticles and carbon nanofibres in electromagnetic absorbing composites

“…As fre quency increases, polarization of dielectrics becomes less influential because the formation of dipoles cannot follow the applied electric field and losses its responsiveness to it. As permittivity is a direct measure of the relationship be tween the polarization and the applied field [52], if a given polarization process loses its response, permittivity tends to decrease. In our case, for any given concentration, this effect is reflected in the decreasing trend observed for both the real and imaginary (not shown) parts of the permittivity with increasing frequency (Fig.…”