The effective thermal conductivity of samples of cryocrystal nanocomposite obtained from argon and SiO 2 nanopowder was determined in the temperature interval 2-35 K using the steady-state method. The thermal conductivity of crystalline argon with nanoparticles of amorphous silica oxide embedded in its structure shows a weak dependence on particle linear dimension in the interval 5-42 nm. The temperature dependence of the thermal conductivity of the nanocomposites can be well approximated by taking into account only the two mechanisms of heat carrier scattering: phonon-phonon interaction in U-processes and scattering of phonons by dislocations. PACS: 65.60 +a Thermal properties of amorphous solids and glasses: heat capacity, thermal expansion, etc.; 66.70.-f Nonelectronic thermal conduction and heat-pulse propagation in solids; thermal waves; 63.20.-e Phonons in crystal lattices.
The experimental setup for obtaining and determination of the thermal conductivity of simple van der Waals crystal-based nanocomposites is described. Preliminary thermal conductivity results of measurements carried out in the temperature range 1-40 K on two samples of methane crystals containing nanoparticles of hydroxyapatite are presented. These results confirm usability of the setup and its suitability as a proper experimental method for investigations of the thermal conductivity of the nanocomposites.
Nanocrystalline La0.9A0.1MnO3 (where A is Li, Na, K) powders were synthesized by a combustion method. The powders used to prepare nanoceramics were fabricated via a high-temperature sintering method. The structure and morphology of all compounds were characterized by X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). It was found that the size of the crystallites depended on the type of alkali ions used. The high-pressure sintering method kept the nanosized character of the grains in the ceramics, which had a significant impact on their physical properties. Magnetization studies were performed for both powder and ceramic samples in order to check the impact of the alkali ion dopants as well as the sintering pressure on the magnetization of the compounds. It was found that, by using different dopants, it was possible to strongly change the magnetic characteristics of the manganites.
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