1,720,996 research outputs found
Controlling the processing of mesoporous titania films by in-situ FTIR spectroscopy: getting Crystalline Micelles into the Mesopores
No full textAn alternative sol-gel route for the preparation of thin films in CeO(2)-TiO(2) binary system
No full textThin films of titania-ceria have been prepared via sol-gel processing by employing titanium and cerium chloride compounds in highly acidic conditions for the precursor sol. This sol-gel route allows obtaining titania-ceria and cerium titanate films, CeTi(2)O(6), after thermal treatment in air. The films exhibit a high optical transparency which is modulated by controlling the composition and the thermal treatment. The materials have been characterized by X-ray diffraction, UV-visible spectroscopy, ellipsometric spectroscopy and atomic force microscopy. The titania-ceria films show, as a function of the composition, the formation of different phases after thermal treatment in air at 800 degrees C. In particular, with the composition Ce25-Ti75 we have obtained a pure cerium titanate phase, CeTi(2)O(6), which can be formed only in a very strict range of compositions. (C) 2009 Elsevier B.V. All rights reserved
Liquid-Phase Preparation and Characterization of Zinc Oxide Nanoparticles
No full textZinc oxide (ZnO) nanoparticles have been prepared by a wet chemical method,
from zinc acetate and LiOH ethanol-based solutions. The resulted nanoparticles
were dispersed in a solvent. The effect of solvent (ethanol or butanol) and surfactant
(polyethylene glycol-PEG 200) on the average size and size distribution of the nanoparticles
was investigated by light scattering measurements. Smaller size was
observed for ZnO nanoparticles dispersed in butanol and PEG 200. The statistical
parameters of the Gaussian size distribution curves were calculated. ZnO nanoparticles
have been prepared to be used as seeds on a substrate for the growth of ZnO
nanowires. The morphology, surface roughness, crystalline structure, and orientation
of the nanoparticles deposed on silicon substrate were characterized by atomic
force microscopy and x-ray diffraction, respectively
Crystallization in hybrid organic-inorganic materials through self-organization from 3-glycidoxypropyltrimethoxysilane
No full textHybrid organic-inorganic materials can organize into layered crystalline structures through self-organization when bridged silsesquioxanes are used in the sol-gel synthesis. Crystallization is, however, also observed in hybrid materials when 3-glycidoxypropyltrimethoxysilane is left to react in highly basic conditions; this synthesis route shows a peculiar property which is the possibility of preparing also crystalline hybrid films by controlling the sol-gel process. The crystalline films exhibit optical anisotropy and are optically transparent. In this article we briefly review the main achievements of our research group in the field. (C)2011 The Ceramic Society of Japan. All rights reserved. RI Takahashi, Masahide/C-3326-200
Formation of cerium titanate, CeTi(2)O(6), in sol-gel films studied by XRD and FAR infrared spectroscopy RID D-5301-2009
No full textThe process of formation of cerium titanate films as a function of annealing temperature and composition has been studied by combining X-ray diffraction analysis and far infrared spectroscopy. The films have been prepared by a sol-gel synthesis using metal chlorides as precursors; the synthesis allows obtaining cerium titanate films upon annealing in air. A brannerite type, CeTi(2)O(6), phase has been identified by X-ray diffraction and Rietveld analysis on thin films. CeTi(2)O(6) is formed upon annealing at 700 A degrees C and in a limited range of ceria-titania mixed compositions. The far infrared spectra are useful to observe the formation of crystalline phases at the beginning of the crystallization process at lower firing temperatures, when the XRD analysis is not enough sensitive
Sol-Gel Processing of Bi(2)Ti(2)O(7) and Bi(2)Ti(4)O(11) Films with Photocatalytic Activity
No full textA new sol-gel synthesis based on chloride compounds as precursors has been used to prepare bismuth titanate (BT) films. The films have been deposited by dip-coating and fired at different temperatures in air; they remain amorphous up to 500 degrees C, and crystallize into the pyrochloric cubic phase Bi(2)Ti(2)O(7) between 600 degrees and 700 degrees C while at higher temperatures of firing the stable Bi(2)Ti(4)O(11) monoclinic phase is formed. The films have been characterized by X-ray diffraction analysis at gracing incidence, X-ray photoelectron spectroscopy, ellipsometric spectroscopy, UV-visible absorption, and atomic force microscopy. The photocatalytic properties of the films have been evaluated by exposing a methyl orange solution containing the BT films to UV light. The test has shown that the Bi(2)Ti(2)O(7) films have a higher activity in comparison with reference anatase titania films
Sol-Gel Processing of Bi(2)Ti(2)O(7) and Bi(2)Ti(4)O(11) Films with Photocatalytic Activity
No full textA new sol-gel synthesis based on chloride compounds as precursors has been used to prepare bismuth titanate (BT) films. The films have been deposited by dip-coating and fired at different temperatures in air; they remain amorphous up to 500 degrees C, and crystallize into the pyrochloric cubic phase Bi(2)Ti(2)O(7) between 600 degrees and 700 degrees C while at higher temperatures of firing the stable Bi(2)Ti(4)O(11) monoclinic phase is formed. The films have been characterized by X-ray diffraction analysis at gracing incidence, X-ray photoelectron spectroscopy, ellipsometric spectroscopy, UV-visible absorption, and atomic force microscopy. The photocatalytic properties of the films have been evaluated by exposing a methyl orange solution containing the BT films to UV light. The test has shown that the Bi(2)Ti(2)O(7) films have a higher activity in comparison with reference anatase titania films
Formation of Cerium Titanate, CeTi2O6, in Sol-Gel Films Studied by XRD and Far Infrared Spectroscopy
No full textFormation of hybrid nanocrystals in organic–inorganic films from a basic sol
No full textOrganic-inorganic films containing hybrid nanocrystals have been prepared by sol-gel processing in controlled conditions. We have systematically changed the temperature and the aging time of a precursor sol containing an organically modified alkoxide bearing an epoxy group, 3-glycidoxypropyltrimethoxysilane, to obtain a controlled crystallization of hybrid layered structures in hybrid films. The precursor sol has been aged at different temperatures, from 5 to 60 A degrees C, and for 1, 2 or 3 days; the films have been deposited from the aged sol and immediately after characterized by X-ray diffraction, Fourier transform infrared spectroscopy and Raman spectroscopy. We have observed that the formation of the hybrid crystals can be obtained only when at least 50% of the epoxies are opened and a larger silica condensation is achieved. These conditions are reached after aging at 60 A degrees C for 1 day, or at longer aging times when the sol is aged at lower temperatures. Transmission electron microscopy and optical polarized images have confirmed the formation of the hybrid crystals. RI Takahashi, Masahide/C-3326-2009; Innocenzi, Plinio/D-5301-200
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