Gas release phenomena in soda-lime-silica glass

• Published in: Journal of non-crystalline solids Vol. 500; pp. 158 - 166
• Main Authors: Vernerová, Miroslava, Němec, Lubomír, Kloužek, Jaroslav, Hujová, Miroslava
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 15-11-2018
• Subjects: Bubble nucleation; Evolved gas analysis; Glass fining; Nucleation temperature; Sodium sulfate; Glass fining; Bubble nucleation; Evolved gas analysis; Nucleation temperature; Sodium sulfate
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2018.07.058

Heterogeneous bubble nucleation during the production of commercial glasses is one of the negative factors affecting their technology and technical properties. In order to eliminate these bubbles, we conducted extensive research of bubble nucleation in soda-lime-silica glass melts at increasing temperatures and variable redox states of glass. Evolved gas analysis (EGA) coupled with gas chromatography and mass spectrometry were used to identify and evaluate crucial chemical reactions during the melting. The reactions were indicated also by the bubble compositions estimated from bubble contraction during the temperature drop. The fining action of sulfates in the reducing conditions was observed at temperatures between 1200 and 1300 °C using high temperature monitoring. This was confirmed by the relatively high average values of the bubble growth rates. In addition, extensive nucleation of bubbles took place at relatively low temperatures. The temperature region of nucleation was determined by monitoring bubble nucleation on the Pt wire immersed in the melt at increasing temperatures. The nucleation of the bubbles in variously reduced glasses has been observed at temperatures even lower than 1300 °C which further decreased with the increasing C/SO42− ratio. Next, we tried to clarify whether the process of bubble nucleation at a low redox state of glass was caused by supersaturation of the glass melt by either physically dissolved or chemically bound gases. We suppose that the nucleation of bubbles SO2 around 1300 °C can be attributed to the reaction between the sulfate remaining in melts and sulfides which have been formed by reduction reactions.
•SLS glass containing sulfate with reducing agent was examined by several methods.•Temperature regions of gas release and bubble nucleation were determined.•Rate of the fining process was assessed from bubble growth rates and compositions.•Reaction between sulfate and sulfide caused supersaturation of melt by gas.