Search results for "thermal treatment"
showing 10 items of 146 documents
Oxygen stoichiometry control of nanometric oxide compounds: The case of titanium ferrites
2011
Three techniques have been coupled with an original device, based on H{sub 2}/H{sub 2}O equilibrium, controlling oxygen partial pressure: XRD, TGA and DC conductivity in order to characterize very reactive compounds such as nanometric powders. From XRD, both the structure and the oxygen stoichiometry (thanks to their lattice parameter) were investigated in situ. From TGA, it was the oxygen stoichiometry (thanks to mass gain or loss) which was determined. From DC conductivity, it was both the structure and the oxygen stoichiometry (thanks to the activation energy) which were obtained. The advantages were to determine very rapidly and with a small amount of powder the equilibrium conditions (…
Mechanism of crystallization of Co-cordierites from stoichiometric powdered glasses
2002
Abstract The influence of cobalt, as a divalent cation, on the crystallization behaviour of the cordierite based glasses was studied. Powdered glass specimens of stoichiometric composition 2MO 2Al 2 O 3 5SiO 2 (M=Co and/or Mg) were obtained and thermally treated at several temperatures and times, and the sequence of crystallization and their microstructural evolution were analysed by X-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM). Results on the crystallization sequence showed that the steps in the crystallization path are independent of the nature of the divalent cation. The first crystalline phase detected displayed the μ-cordierite structure, i.e. a solid…
Electrochemical Studies of Nonstoichiometric TiO<sub>2-x</sub> Ceramic
2014
TiO2 ceramic was prepared using extrusion technology and thermal treatment in two stages: sintering in air and subsequent annealing under high vacuum conditions. Sample thermal treatment in high vacuum conditions causes formation of nonstoichiometric titanium oxide ceramic. As a result electrical conductivity of the material significantly increases. Such a material can be used for electrode production for electrochemical water treatment.
Photoelectrochemical removal of chlorfenvinphos by using WO3 nanorods: Influence of annealing temperature and operation pH
2019
[EN] A visible-light driven photoelectrochemical degradation process has been applied to a solution polluted with the organophosphate insecticide chlorfenvinphos. Different WO3 nanosheets/nanorods have been used as photoanodes. These nanostructured electrodes have been fabricated by anodization of tungsten and, subsequently, they have been subjected to a thermal treatment (annealing). The combined influence of annealing temperature (400¿°C and 600¿°C) and operation pH (1 and 3) on the photoelectrocatalytic behavior of these nanorods has been examined through a statistical analysis. Morphological, structural and photoelectrochemical characterizations have also been carried out. The chlorfenv…
Physicochemical characterization and photoelectrochemical analysis of iron oxide films
2013
Iron oxide films with a nanoporous structure were grown by anodizing sputter-deposited Fe in a fluoride containing ethylene glycol solution and annealed under air exposure at different temperatures. X-ray diffraction and Raman spectroscopy allowed to identify the presence of hematite and/or magnetite after thermal treatment for films annealed at T ≥ 400 °C under air exposure. According to GDOES compositional depth profiles, the thermal treatment sensitively reduced the amount of fluoride species incorporated into the film during the anodizing process. A band gap value of ~2.0 eV was estimated for all the investigated layers, while a flat band potential dependent on both the growth condition…
Atomic layer deposition of Ti-Nb-O thin films onto electrospun fibers for fibrous and tubular catalyst support structures
2018
Here, the authors report on the preparation of core-shell carbon-ceramic fibrous as well as ceramic tubular catalyst supports utilizing electrospinning and atomic layer deposition (ALD). In this paper, ALD of Ti-Nb-O thin films using TiCl4, Nb(OEt)5, and H2O as precursors is demonstrated. According to the time-of-flight-elastic recoil detection analysis and Rutherford backscattering spectrometry, carbon and hydrogen impurities were relatively low, but depend on the pulsing ratio of the precursors. Optimized ALD process was used for coating of sacrificial electrospun polyvinyl alcohol (PVA) template fibers to yield tubular Ti-Nb-O structures after thermal or solution based PVA removal. Anoth…
Influence of Structure Ordering, Defects and External Conditions on Properties of Ferroelectric Perovskites
2000
Results of comprehensive studies of the (A’A“)(B’B”)O3-ferroelectric perovskites are reported. Examined compositions include Pb1-xLax(Zr0.65Ti0.35)1-x/4O3(PLZT), PbSc0.5Nb0.5O3(PSN), PbSc0.5Ta0.5O3(PST), and PMNT, PSNT and PLuNT pseudo-binary systems exhibiting pronounced dielectric, electrooptical, and electromechanical properties. Degree of ordering in the materials has been varied by chemical composition (modification, isomorphic ion substitution), by variation of technology (hot-pressing, specific thermal treatment, thin films), and by irradiation of different kind and intensity (γ-rays, electrons, neutrons).
Effects of Ionising Radiation on Optical Properties of Lithium Niobate Single Crystals
2005
Studies of thermal and γ-irradiation effects on the optical properties in congruent lithium niobate single crystals containing Mg and Gd dopants including samples with double dopants Y, Mg are reported. Formation of defects at irradiation and thermal treatment of the samples is explored by analysis of the behaviour of electron absorption spectra. Considerable increase of absorption with the dose of γ-radiation is observed at 500 nm. The changes of absorption examined under different conditions are explained by creation and destruction of Nb 4+ defects.
Large scale synthesis of nanostructured zirconia-based compounds from freeze-dried precursors
2013
Nanocrystalline zirconia powders have been obtained at the multigram scale by thermal decomposition of precursors resulting from the freeze-drying of aqueous acetic solutions. This technique has equally made possible to synthesize a variety of nanostructured yttria or scandia doped zirconia compositions. SEM images, as well as the analysis of the XRD patterns, show the nanoparticulated character of those solids obtained at low temperature, with typical particle size in the 10–15 nm range when prepared at 673 K. The presence of the monoclinic, the tetragonal or both phases depends on the temperature of the thermal treatment, the doping concentration and the nature of the dopant. In addition,…
Water diffusion and swelling stresses in ionizing radiation cured epoxy matrices
2017
Abstract In this work a DGEBF epoxy monomer was cured by electron beam radiation in the presence of an iodonium salt and the obtained system was hydrothermally aged as such and also after a thermal treatment, in order to obtain two systems having different uniformity in the cross-linking degree. On both systems, the transient stress field arising from swelling was measured and monitored by an optical Photoelastic technique and the results were commented with reference to a thermally cured epoxy system containing the same monomer and already discussed in a previous work. Beam samples with identical dimensions, obtained from the irradiated systems, have been aged at 80 °C in water, and charac…