23 research outputs found
NANO-OBJECTS IN OWN MATRIX - SELF COMPOSITE
No full textEstablishing the principles of nanoscience and nanotechnology has led to rethinking our understanding of the material\u27s properties. Therefore, some earlier results deserve to be analyzed again. In this paper, we present our results, which led to establishing a new type of nanocomposite - Self composite. The Self composite consists of matrix and nanometric size dispersed phase, with the specificity that the nano-object is formed from the same material or its parts, such as a matrix. We have made these nanocomposites using standard methods for the production of monocrystals or molecular beam epitaxy, but slightly above the solubility limit of the starting components. The possibility of obtaining Self composite by laser surface treatment of monocrystalline samples and agglomeration of a part of nanodimensional materials was also presented. Self composites are characterized (SEM, AFM, XRD, far-infrared, and Raman spectroscopy), and results were analyzed by Effective Medium Theory
Raman study of surface optical phonons in ZnO(Co) nanoparticles prepared by hydrothermal method
No full textOptical properties of plastically deformed copper: an ellipsometric study
No full textIn this paper the results of optical properties investigations on plastically deformed copper are presented. The optical properties of the plastically deformed copper were studied using spectroscopic ellipsometry in the ultraviolet-visible (UV-VIS) range. Chemically pure copper was deformed by applying the Equal Channel Angular Pressing (ECAP) technique. During the last decade, equal-channel angular pressing procedure was used for the fabrication of ultrafine-grained metals and alloys. The plastic deformation of metallic materials leads to the production of bulk nano-scale structures with ultrafine grains and cross-sections, which remain about equal before and after deformation. The parameters of the sample were calculated using a two-film model together with the Bruggeman effective medium approximation
Pb1xMnxTe single crystals and their structural properties
No full textPb1-xMnxTe crystals were grown by the vertical Bridgman method. Their structural properties were observed both by optical microscopy after chemical polishing and ething, and by X-ray powder diffraction analysis. A solution of 5 vol. % Br2 in HBr at room temperatur, for an exposure of 2 min was determined for chemical polishing. A solution of 20 g KOH in 1 ml H2O2, 2 ml glycerol (C3H8O3), and 20 ml H2O at room temperature for an exposure for 6 min was found to be a suitable etching solution. The obtained results are discussed and compared with published data
CHARACTERIZATION OF BARIUM BISMUTH TITANATE OBTAINED BY MECHANOCHEMICAL SYNTHESIS
No full textBarium bismuth titanate, BaBi4Ti4O15 (BBT) was prepared by homogenization and
sintering of mixture of stoichiometric quantities of BaTiO3 and Bi4Ti3O12 obtained via
mechanochemical synthesis. The reaction mechanism of BaBi4Ti4O15 formation and the
characteristics of BBT powders and ceramics were studied using XRD, Raman
spectroscopy and SEM. The results confirmed that BaBi4Ti4O15 was formed by
tetragonal symmetry. Only 4 Raman modes are clearly observed. Ba2+ ions randomly
occupy the Bi sites of a pseudo-perovskite layer and may enter in a bismuth oxide layer.
BaBi4Ti4O15 ceramics possess the plate-like structure typical for layered structure
materials
Pb1-xMnxTe and PbTe1-xSx compounds and their optical properties
No full textPb1-xMnxTe crystals were obtained by the Bridgman method and PbTe1-xSx crystals were grown by the vapour–liquid–solid technique. The tructural properties of Pb1-xMnxTe (x £ 0.10) and PbTe1-xSx (x £ 0.05) were observed by X-ray powder diffraction analysis. The optical properties were studied by Raman spectroscopy as a function of temperature. Measurements on these samples of different composition gave information about the Mn and S position in the lattice (off-centering), their clustering and ordering, as well as of the influence of these processes on the crystal structure and properties. The model of phonon behaviour based on the Random Element Isodisplacement model was applied, and it was found that the phonons in PbTe1-xSx show a two-mode behaviour (each TO-LO mode pair of the end members degenerates to an impurity mode), while the Pb1-xMnxTe optical phonons have a ntermediate one-two-mode behaviour (the LO-mode frequency shifts continuously from PbTe to MnTe, while the other modes resemble the two-mode case)
