Alternative batch compositions in the glass-forming region of the Na2O-CaO-SiO2 system

• Published in: Journal of non-crystalline solids 2003-11, Vol.329 (1-3), p.22-26
• Main Authors: GARZA MONTOYA, B, TORRES-MARTINEZ, L. M, QUINTANA, P, IBARRA, J
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Equations of state, phase equilibria, and phase transitions; Exact sciences and technology; Glass transitions; Physics; Specific phase transitions
• ISSN: 0022-3093
• DOI: 10.1016/j.jnoncrysol.2003.08.006

An alternative new method of pre-reacted batches, without free SiO2, is proposed in the glass-forming region of the system Na2O-CaO-SiO2. Compositions were prepared by solid state reaction, as pellets and as a loose powders. The batches were treated with successive heating in the 400-900 C interval, just before the liquid phase is obtained. The evolution of the phase formation was followed by powder XRD and the liquid phase was observed by polarized light optical microscopy. The use of pellets favors the presence of Na2Ca(CO3)2, which enhances the formation of several ternary phases and avoids the formation of free calcium oxide. Three mixtures were selected on the basis that they showed the lowest free SiO2 content, therefore being considered the best candidates to be prepared using raw materials supplied from the glass industry. The best compositions were localized in the low SiO2 content, since the liquid phase appears above 1100 C. 12 refs.