Annealing behavior of silica gel powders modified with silver crystalline aggregates

The annealing behaviour of silica powders added with silver, prepared by the sol-gel method, was studied using X-ray diffraction. Partial crystallization of amorphous SiO2 samples as low as 600°C has been observed. For that, silver needed to be added to the precursor solution in such a way that it formed aggregates. Silica xerogel samples were prepared using a molar ratio ethanol/H2O/TEOS of 4:11.6:1 and loaded with silver in three different ways: in the form of silver nitrate, silver chloride, or chemically synthesised silver fine particles. The microstructure of the silica xerogel powders was studied as a function of annealing temperature. Attention was paid to the evolution of the glass matrix as well as the silver aggregates in the SiO2 matrix. Partial crystallization of the glass matrix was achieved at temperatures much lower than those specified by the phase diagram, independently of preparation method of the silver aggregates.

Composites; Glasses; Structure; X-rays Amorphous materials; Annealing; Chemical modification; Crystal microstructure; Crystalline materials; Crystallization; Glass; Phase diagrams; Powders; Silver; Temperature; X ray diffraction analysis; Silica gel powders; Silver crystalline aggregates; Sol-gel method; Silica gel

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