Nanocomposites and nanomaterials

Controllable microwave properties of segregated polymer-carbon composites
Lazarenko O.A., Lozitsky O.V., Vovchenko L.L., Matzui L. Yu.
Department of Physics, Taras Shevchenko National University of Kyiv.
64/13, Volodymyrska Street, City of Kyiv, Ukraine, 01601
E-mail: alazar@univ.kiev.ua

Nanocarbon composites with segregated structure cause an increased interest due to the opportunity to reduce the amount of filler significantly and hence, cost of the resulting material and maintaining its mechanical properties. It is known, that segregated system can be characterized by two values of filler concentration, the average concentration φ related to the whole volume of composite and the local concentration of particles φloc in the wall of the formed mesh ( φloc>φ). [1] Electrical and thermal conductivity, dielectric and mechanical properties in composite with the segregated structure are improved significantly compared to composite with random distribution of filler at the same concentration. However, there is a lack of numerical studies of the microwave absorbing properties of segregated composites, which is essential for the manufacture of materials with adjustable absorbing parameters. 
In order to analyze the effect of polymer particles size, filler concentration, dielectric and magnetic permeability of the polymer and filler particles on s-parameters of composites with a segregated structure the electromagnetic response of a monolayer and several layers based on polymer spheres segregated carbon particles has been numerically investigated in the Ka-band (26–37GHz). As a basis for the calculation, we used the model proposed in [2] for a heterostructure based on a monolayer of hollow glassy carbon spheres packed in 2D lattice. For modeling of segregated systems, we changed the model to consider the electromagnetic response not only for contacting spheres but also for cube-shaped particles. The segregated structure contains more controllable parameters of the material (like distance between particles) compared to a bulk material which may achieve superior frequency dependencies of transmission, reflection and absorption coefficients.

1.	Yevgen Mamunya. Carbon Nanotubes as Conductive Filler in Segregated Polymer Composites - Electrical Properties, Carbon Nanotubes - Polymer Nanocomposites, 2011.- Siva Yellampalli, IntechOpen.
2.	D. Bychanok, S. Li, A. Sanchez-Sanchez, G. Gorokhov, P. Kuzhir et al.
Hollow carbon spheres in microwaves: Bio inspired absorbing coating //
Appl. Phys. Lett.  – 2016. – 108. - 013701.