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M.G. Garnica-Romo J.M. Yánez Limón J. González-Hernández R. Ramírez-Bon D. Ramírez-Rosales R. Zamorano-Ulloa S. Tirado-Guerra 《Journal of Sol-Gel Science and Technology》2002,24(2):105-112
In this work, SiO2 samples with silver, prepared using the sol-gel method, were analyzed after being thermally treated in air in the range of 100 to 800°C. The sol-gel starting solutions were prepared by mixing tetra-ethyl-orthosilicate (TEOS), water and ethanol. Samples with 4 different H2O/TEOS molar ratios (3.3, 5, 7.5 and 11.7 respectively) and with different nominal Ag concentrations were prepared (1, 2 and 4%vol. of Ag). It was found that upon annealing, different silver spices were formed, such as Ag2
+, Ag+, Ag°, and metallic silver aggregates. The identification of these spices was carried out by means of X-ray diffraction, Electron Paramagnetic Resonance (EPR), optical emission and optical absorption. It was also found that the specific type of silver spices observed depends on the structure of the SiO2 matrix and on the annealing temperatures. It was found that samples prepared from precursor solutions with a low H2O/TEOS ratio have a more open structure, and therefore silver diffuses faster and forms agglomerates at lower temperatures. Samples prepared from solutions with larger H2O/TEOS ratios have a more dense structure, which allows the formation of atomic or molecular spices in addition to silver particles. A systematic study of this system was carried out using EPR on samples prepared from solutions having different H2O/TEOS molar ratios, various Ag concentrations and subjected to different thermal treatments. 相似文献
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M.G. Garnica-Romo J.M. Yañez-Limón M. Villicaña J.F. Pérez-Robles J. González-Hernandez 《Journal of Physics and Chemistry of Solids》2004,65(6):1045-1052
SiO2 based glasses added with nanometric-silver particles have been prepared by the traditional sol-gel process, using the tetraethyl-orthosilicate alkoxide. The Ag particles were prepared using a new method described in this article, the method uses a cementation reaction between Ag ions and an iron electrode. The size of the particles, measured in the dried glass, was in the range of 100-200 nm. The observed structural changes depend on the annealing conditions, such as the annealing temperature, the amount of silver particles and the type of acid (HCl or HNO3) used to catalyze the hydrolysis/condensation reactions during the sol-gel process. Samples prepared using both acids crystallized into the cristobalite phase after thermal annealing at 800 °C. The amount of SiO2 crystallized depends on the amount of Ag present in the glass. Samples prepared from solutions catalyzed with HCl acid show the formation of nanometric Ag particles after thermal annealing at 500 °C, these small particles are not observed after similar treatments when HNO3 is used as the catalytic acid. HCl and Ag2O form AgCl which is reduced by residual carbon to form Ag ultrafine particles. The diffusion of the reduced Ag spices, which form these particles, is facilitated by the opened structure of the glasses added with Ag, as indicated by IR measurements. 相似文献
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Abuhani Waleed A. Dasgupta-Schubert Nabanita Mattusch Jürgen Villaseñor-Cendejas Luis M. Landsberger Sheldon Alexander Steven Garnica-Romo Ma. Guadalupe 《Journal of Radioanalytical and Nuclear Chemistry》2019,322(3):1365-1371
Journal of Radioanalytical and Nuclear Chemistry - Three geothermal microecologies, constituted of fumaroles, hydrothermal springs and the native volcanic superstratum at the Los Azufres (Mexico)... 相似文献
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