Abstract
The effect of H2O and the slow thermal annealing on the properties of pure silica (SiO2) and phosphosilicate (SiO2-P2O5) gel-glasses are presented. The monolithic samples have been prepared via sol-gel process using tetraethorthosilicate (TEOS), Si(C2H5O)4 and Triethylphosphate (TEP) (C2H5O)3P(O) as SiO2 and P2O5 precursors. Phosphate incorporates into the silicate network by substituting Si atoms and consequently, we observed changes in structural and spectroscopic properties for these systems. The structures of prepared samples were examined by observed weight loss, XRD and FTIR. It has been found that in the structure of pure silica and phosphosilicate glasses there are formed domains characterized by certain degree of ordering of the units present in their composition, while the structure of pure silica is still amorphous of these glasses. The changing character of domains structure may be the reason of different chemical activities of phosphosilicate glass.
Highlights
The sol-gel technique is considered to be excellent and the most practical chemical method in recent years for preparing chemically homogeneous monolithic, coatings and powders with a variety of useful applications such as optic, coating materials and biological [1]-[4]
High rates of hydrolysis are required, which leads to the opining network of silicate system to overcome the agglomeration of particles
The synthesized solutions were homogeneous and transparent, the viscosity of pure silica and phosphosilicate which increased with the increasing aging time of the solutions
Summary
The sol-gel technique is considered to be excellent and the most practical chemical method in recent years for preparing chemically homogeneous monolithic, coatings and powders with a variety of useful applications such as optic, coating materials and biological [1]-[4]. I. Ali sists of the following major stages: hydrolysis of the precursors (generally, metal alkoxides) to form a homogeneous sol, poly-condensation of the sol to form a non-crystalline gel network, several steps to remove excess solvent and unreacted precursors, drying and calcination treatments to form end product. The starting materials of the sol-gel process, are known for their relatively high reactivity, especially to water. High rates of hydrolysis are required, which leads to the opining network of silicate system to overcome the agglomeration of particles. In these cases, it is necessary to modify the precursors so as to increase their stability toward hydrolysis [5]-[7]
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