Solid State Phenomena Vol. 151

Abstract: The Nanocomposite group of AIDICO and the Nanomaterials Group of University of Valencia collaborate in the research of new organic-inorganic hybrid materials with application in construction products. Tribological properties and good thermal stability are some of the required specifications for such applications. Some hybrid coatings based on simultaneous formation of epoxy and silica networks are introduced in this work. Elastic modulus and hardness obtained from TDMA analyses and indentation techniques, together with thermal stability by TGA, are the main properties analysed in order to fulfil the requirements for construction coating applications. New routes for obtaining these coatings based on sol-gel have been explored.

Abstract: Different compositions of α- and α-/β- SiAlON materials have been prepared from separate nanopowders and their composites: Si3N4 – AlN, Si3N4, Al2O3 and Y2O3, produced by the method of plasma-chemical synthesis. Compositions have been sintered by spark plasma sintering (SPS) method in vacuum at 1700 °C with a heating rate of 100 °C/min and holding time of 5 min. The densification behaviour of the materials at these sintering conditions depends insignificantly on the powder composition. It is possible to obtain dense ceramic materials with relatively fine-grained structure (200-400 nm) and good mechanical properties from nanosized powders at relatively low temperatures (1400-1600 °C). The holding time at applied compacting conditions is still too short to ensure the formation of α- SiAlON phase corresponding to the phase diagram. All samples consist of β- SiAlON’s of differing composition and this is the reason for relatively low hardness of samples (HV5 = 15,6-16,9 GPa).

Abstract: In this work, cobalt ferrite nanowires were chemically synthesized using FeOOH array a template. The FeOOH nanoarray was obtained by the hydrolysis and precipitation of Fe+3, from FeCl3.4 H2O. The cobalt ion (Co+2) was added in order to make it interact with FeOOH nanorods of 20 nm of diameter and 150 nm of length. These nanorods are grouped into packages having different orientations due to the interaction with the cobalt ions. The arrays were calcinated at 700 and 800 °C to obtain cobalt ferrite nanowires with 70 nm of diameter and some micrometers of length. The morphology and the average size of the nanorods and nanowires were determined using Field Emission Scanning Electron Microscopy (FESEM). The Fourier Transform Infrared Spectroscopy (FTIR) was used to study the interaction between the nanorods and the cobalt ions. The phases of the material were identified using X-ray Diffraction.

Abstract: A field-assisted solid state ion exchange (FASSIE) approach is used to dope silicate glasses with mono- and/or multivalent ions, in which the diffusion of ions coming from a film deposited onto the glass surface is driven by an external electric field. Metal precipitation to form nanoparticles may take place during the ion exchange, depending on the process parameters, or it can be induced by irradiation with high power laser beams. Characterization of silicate glass samples doped with either gold or silver is performed by optical absorption and transmission electron microscopy.

Abstract: Сomposite films containing II-VI based semiconductor nanoparticles have been prepared by different physical and chemical techniques. Non-magnetic CdS1-xSex nanoparticles were grown by melting of the semiconductor doped fine powder borosilicate glass. The composite semimagnetic semiconductor Cd1-xMnxTe based films were fabricated by embedding in SiO2 matrix with using of pulsed laser deposition technique. New chemical approach to synthesis of Cd1-xMnxS nanoparticles in polymer matrix has been proposed. The optical absorption edge for CdS1-xSex , Cd1-xMnxTe nanoparticles and exciton structure in the spectrum of Cd1-xMnxS nanoparticles shifted to the higher-energy side compared to those for bulk crystals due to the quantum confinement effect. Magneto-optical Faraday effect for non-magnetic semiconductor nanoparticles in glass demonstrates only small changes as compared with that of bulk semiconductors. The revealed peculiarities in spectral and magnetic field dependences of the Faraday rotation for the studied semimagnetic semiconductor composite films can be attributed to the influence of dimensionality on spin exchange parameters for such kind of nanostructures.

Abstract: The “islands” of ZnO nanocrystals on amorphous monodisperse 200 nm SiO2 spheres (core-shell particles) were obtained by simple one-step technique based on low-temperature crystallization from liquid phase. The influence of starting reagents types and concentration of zinc ions in the reaction mixture on the morphology of ZnO shells obtained was studied. Crystalline structure of ZnO nanocrystals obtained was proofed by the X-ray diffraction data. The average diameter of ZnO nanocrystals on SiO2 spheres is 10 nm according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) data. It was shown that SiO2/ZnO particles obtained have high luminescence characteristics. Photoluminescence spectra of core-shell SiO2/ZnO particles show two emission peaks centred at 386 nm and 570 nm. Core-shell SiO2/ZnO particles obtained are perspective for active photonic crystals creation for UV-spectral region.