Scattering of quasi-optical THz beams on spherical MWCNTs aerogels

Results of research of lateral scattering of electromagnetic radiation by aerogel of MWCNTs are presented. Frequency dependences of lateral scattering of THz radiation of spherical MWCNTs aerogels with diameter of 4.5 and 6 mm at frequency range 43-970 GHz are given

Temperature Dependences of Conductivity and Magnetoconductivity of Multiwall Carbon Nanotubes Annealed at Different Temperatures

Представлены температурные зависимости проводимости (в диапазоне 4.2-300 K) и магнето- проводимость (в полях до 10 кГ при 4.2 K) многослойных углеродных нанотрубок со средним внешним диаметром 8-10 и 20-22 нм, отожженных при различных температурах (1600, 2200, 2600, 2800◦C). Показано, что зависимость проводимости для нанотрубок со средним диаметром 20-22 нм характерна для квантовых поправок к проводимости взаимодействующих электронов в двумерных проводниках с локальным беспорядком. Для нанотрубок со средним диаметром 8- 10 нм имеет место одномерная прыжковая проводимость с переменной длиной прыжка. Показано, что при температурной обработке многослойных углеродных нанотрубок изменяется вклад квантовых поправок в проводимость, а также параметры прыжковой проводимости, что отжиг образцов влияет на магнетопроводимость. Многослойные углеродные нанотрубки со средним диаметром 20-22 нм имеют положительную магнетопроводимость.Temperature (in range 4.2-300 K) and magnetic field (in fields up to 10 kG at 4.2 K) dependences of the conductivity of two sets of multiwall carbon nanotubes with different average diameters (8-10 nm and 20-22 nm) heated at various temperatures (1600, 2200, 2600, 2800◦C) were investigated. Temperature dependences for nanotubes with average diameter 20-22 nm is typical for quantum corrections to conduc- tivity of the systems with interaction electrons in two dimensional conductors with local disorder. For nanotubes with average diameter 8-10 nm temperature dependences corresponds to one-dimensional variable range hopping conductivity (VRHC). The variation of annealing temperature of MWNTs influence on the contribution of corrections to conductivity and parameters of VRHC. The magnetoconductivity of MWNTs also depends on the annealing temperature and is less than that of highly oriented pyrographite. Annealed MWNTs with average diameter 20-22 nm has a positive magnetoconductivity

Electromagnetic parameters of composite materials based on polyethylene and multi-walled carbon nanotubes modified by iron oxide nanoparticles

Specifi c features are revealed of how composite materials are formed on the basis of polyethylene and multi-walled carbon nanotubes modifi ed with iron oxide nanoparticles (Fe3O4/MWCNT–PE), produced by the mechanical mixing method from a polyethylene melt. The conditions in which the composite materials are obtained were optimized to provide a uniform distribution of the Fe3O4/MWCNT fi ller in the polyethylene matrix. The infl uence exerted by the Fe3O4/MWCNT fi ller on the electrical properties of the resulting composite materials was determined. Introduction of Fe3O4 nanoparticles gives rise to magnetic properties of a composite material in the frequency range from 1 kHz to 2 MHz. An analysis of the frequency dependences of refl ectance, transmittance and absorbance demonstrated that an increase in the sample thickness leads to a higher refl ectance and lower transmittance. The composite materials can be used to create coatings lowering the electromagnetic radiation intensity by up to 40%. It was shown that increasing the content of Fe3O4/MWCNT to more than 10 wt % leads to a decrease in both the electrical conductivity and the complex dielectric permittivity and magnetic permeability of the composite material. This occurs due to the decrease in the fl owability of the polymer material and to the resulting nonuniform distribution of the fi ller in the bulk of polyethylene