Resumen

GARNICA-ROMO, M.G. et al. Estudio de polvos y recubrimientos de SiO₂ con introducción de Ag preparados mediante el proceso Sol-Gel. Superf. vacío [online]. 2007, vol.20, n.1, pp.14-20. ISSN 1665-3521.

Coatings on glass corning and SiO₂ powders were prepared with incorporation of Ag particles using the sol-gel method. The starting solutions to obtain SiO₂ were prepared mixing tetra-ethyl-orthosilicate (TEOS), water and ethanol. Samples with four different H₂O/TEOS molar ratios (3.3, 5, 7.5 and 11.7, respectively) and with several nominal Ag concentrations incorporated by nitrates were prepared to obtain the following molar ratios of Ag/SiO₂ in the final product (0.025, 0.05 and 0.10). The samples were thermally treated in the range of 100 to 800°C. The experimental results shown that different species from silver were formed during the thermal treatment; such as Ag₂⁺, Ag⁺, Ag⁰ and metallic aggregates. The characterization of the system was carried out by means of X-ray diffraction, emission spectroscopy and electron paramagnetic resonance (EPR). Each specific type of silver species observed was dependent of the SiO₂ matrix structure and on the thermal treatment; in that sense the samples prepared from precursor solutions with a H₂O/TEOS ratios of 3.3 and 5.0 they give place to a structure of SiO₂ matrix in which the formation of Ag particles at lower temperatures was promoted. Samples prepared from solutions with H₂O/TEOS ratios of 7.5 and 11.7 give place to a SiO₂ structure matrix in which was observed the formation of atomic and molecular species of Ag, and a process of crystallization of the SiO₂ in its α-cristobalite phase at low temperature.

Palabras llave : Coatings; SiO₂ powders; Molecular species of Ag; Electron paramagnetic resonance; α-cristobalite.

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