1198 ISSN 0020-1685, Inorganic Materials, 2016, Vol. 52, No. 11, pp. 1198–1203. © Pleiades Publishing, Ltd., 2016. Original Russian Text © O.S. Yakovenko, L.Yu. Matzui, L.L. Vovchenko, V.V. Oliynyk, V.L. Launetz, A.V. Trukhanov, 2016, published in Neorganicheskie Materialy, 2016, Vol. 52, No. 11, pp. 1271–1276. Dielectric Properties of Composite Materials Containing Aligned Carbon Nanotubes O. S. Yakovenko a, *, L. Yu. Matzui a , L. L. Vovchenko a , V. V. Oliynyk a , V. L. Launetz a , and A. V. Trukhanov b, c a Shevchenko National University, Volodymyrs’ka vul. 64/13, Kyiv, 01601 Ukraine b Moscow Institute of Steel and Alloys (National University of Science and Technology), Leninskii pr. 4, Moscow, 119049 Russia c Scientific–Practical Materials Research Centre State Research and Production Association, Belarussian Academy of Sciences, ul. Brovki 19, Minsk, 220072 Belarus *e-mail: alenka-ya@ukr.net Received July 6, 2015; in final form, February 26, 2016 Abstract—This paper presents a study of the electrodynamic properties of polymer-matrix composite mate- rials containing a filler in the form of multiwalled carbon nanotubes. We have examined the effect of filler alignment in the composites on their interaction with electromagnetic radiation. The composite materials have an anisotropic electrical conductivity, dielectric permittivity, and electromagnetic radiation attenuation coefficient because an applied electric field produces a preferential filler alignment direction. Keywords: carbon nanotubes, composite materials, dielectric permittivity, electromagnetic shielding, anisotropy DOI: 10.1134/S0020168516110182 INTRODUCTION In recent years, many research groups have focused on the preparation and properties of composite mate- rials with an enhanced electromagnetic response [1–3]. Increased interest in this area of research has been aroused by the importance of creating structural mate- rials capable of effective electromagnetic interference (EMI) shielding [4, 5]. The fillers most widely used so far to produce shielding materials have been metals: when incorporated into a polymer matrix, they ensure high magnetic losses in the material [6–8]. Unfortu- nately, the metals have high density, rapidly oxidize, poorly absorb electromagnetic radiation, and are not always satisfactory fillers for producing shielding materials. Recent years have seen a steadily increasing interest in EMI shielding composites using carbon nanomate- rials because such fillers have a number of advantages over conventional carbon fillers (carbon fibers, carbon black, and others) as to their structural and electrical properties [9–11]. The incorporation of a carbon filler into a polymer matrix makes it possible to vary the dielectric properties of the material. Among the diver- sity of carbon fillers, particularly distinctive are carbon nanotubes (CNTs) owing to their unique physical properties, in particular, high thermal and electrical conductivity and excellent mechanical and absorption properties [12]. The use of CNTs as a filler in compos- ite materials (CMs) for producing EMI shields makes it possible to impart appropriate shielding properties to materials at low filler concentrations, thereby main- taining the light weight and strength of the polymer matrix [13]. However, even though the shielding prop- erties of composites, as well as their mechanical, elec- trical, thermal, optical, and many other properties, have recently been the subject of intense research, data on these properties are rather fragmentary and are not always satisfactory. The large aspect ratio of CNTs determines their anisotropy relative to their axis [14]. However, in com- posites produced by standard processes, the anisotro- pic properties of individual CNTs do not show up because of the strong tendency for CNTs to agglomer- ate. For the fabrication of polymer-matrix nanocom- posites possessing anisotropic physical properties, an ordered ensemble of aligned nanoparticles—should be incorporated into a matrix. The methods proposed to date for aligning nanoparticles employ various external influences, such as a magnetic or electric field and mechanical loads [15–19]. The use of an electric field for aligning nanoparticles appears to be the simplest and most effective approach, especially when CNTs are used as a filler. Basic to this approach is that an electric field E creates a polarization of charges P in a conductive nanotube: P = α || Ecos ϕ. Here, α || is the longitudinal polarizability of the tube and ϕ is the angle between the axis of the tube and the direction of the external field E. Note that, according to numerical calculations