How to cite this paper: Zhuravlev, V.A., Suslyaev, V.I., Korovin, E.Yu. and Dorozhkin, K.V. (2014) AbstractResults of measurements of permeability, permittivity and radar absorption properties of composites on basis of carbonyl iron particles R-10 brand are presented in this paper. The calculations and experimental studies have shown that in the super high frequency (SHF) and extremely high frequency (EHF) ranges on the basis of two-layer structures with different content of carbonyl iron particles can create a radar absorbing coatings with a reflectivity of less than −10 dB over a wide bandwidth from 3.1 to 17.1 GHz and from 27 to 37 GHz. Absorbing properties of composites are saved in terahertz frequency range from 250 to 525 GHz.

Coagulation technique was applied for preparation of multiwall carbon nanotube- (MWNT-)containing polystyrene (PSt) composite materials with different MWNT loading (0.5–10 wt.%). Scanning and transmission electron microscopies were used for investigation of the morphology and structure of produced composites. It was shown that synthesis of MWNT/PSt composites using coagulation technique allows one to obtain high dispersion degree of MWNT in the polymer matrix. According to microscopy data, composite powder consists of the polystyrene matrix forming spherical particles with diameter ca. 100–200 nm, and the surface of MWNT is strongly wetted by the polymer forming thin layer with 5–10 nm thickness. Electrical conductivity of MWNT/PSt composites was investigated using a four-probe technique. Observed electrical percolation threshold of composite materials is near to 10 wt.%, mainly due to the insulating polymer layer deposited on the surface of nanotubes. Electromagnetic response of prepared materials was investigated in broadband region (0.01–4 and 26–36 GHz). It was found that MWNT/PSt composites are almost radiotransparent for low frequency region and possess high absorbance of EM radiation at higher frequencies.

A comparative study of multiwalled carbon nanotube/polyethylene (MWCNT/PE) composites produced by different methods (thermal mechanical mixing, coagulation precipitation technique and in situ ethylene polymerization with a ZieglerNatta catalyst supported on MWCNTs) has been performed. The morphology and structure of the produced composites were investigated by optical, scanning and transmission electron microscopies. MWCNT incorporation into PE matrix results in the change of conductivity mechanism from conductivity typical of a system with local disorder and effects of weak interaction of electrons (quantum correction to conductivity) to conductivity that can be described within the theory of Coulomb blockade or quasi-one-dimensional variable-range hopping conductivity with variable length of hops (Mott's law) between localized states. The electromagnetic (EM) response of composites was investigated in a broadband region (118-510 GHz). It was found that the dielectric properties of MWCNT/PE composites correlate with their electrophysical properties determined by the MWCNT distribution within the polymer matrix.Typical TEM image of MWCNT in polyethylene matrix. Distance between nanotubes filled with PE varies within a wide range ß

The frequency dependences of the magnetic permeability of Ba 3 Co 2 Fe 24 O 41 ferrite with hexagonal crystalline structure are given which have been obtained by waveguide and resonator methods in the frequency range 0.1-11 GHz. The data on the magnetic spectra of this material available in the literature have been analyzed to select the most reliable experimental results. The expert judgement on the spectra was made using the Cramers-Kronig dispersion relations. It has been shown that the Cramers-Kronig relations can be used to correct complex magnetic permeability measurements by reciprocal recalculation of the frequency dependences of the real and imaginary parts.

Interface interactions in multicomponent nanoparticles can affect electromagnetic properties of an absorbing system. In this work, we investigate the electromagnetic response of multi-walled carbon nanotubes (MWCNTs) filled with iron-containing nanoparticles (ICNs) in the terahertz frequency range. MWCNTs with different iron content have been synthesized by aerosol-assisted catalytic chemical vapour deposition method from toluene containing a certain quantity of ferrocene used as a catalyst. According to the x-ray diffraction analysis, encapsulated ICNs were mainly in the form of iron carbide. Thin composite films were prepared from the iron-filled MWCNTs and polymethylmethacrylate (PMMA) by casting and stretching methods. The composites showed an enhanced permittivity and anisotropy in the transmittance spectra when iron content increased. This behaviour was related to the mechanism based on electrical conductivity and polarization of ICNs and ICN/MWCNT interfaces. Since terahertz field penetrates inside MWCNTs, the filling of their cavities can be a way of varying the electromagnetic properties of MWCNT-containing composites.