Treatment of soda-lime-silica glass surfaces with fluorine-containing gases

Abstract

Laboratory investigations are carried out to elucidate the interaction between fluorine-containing gases and glass surfaces in the temperature range between 450 and 650 °C. The influence of tetrafluoromethane and difluoroethane (1 vol% in air atmosphere) is studied upon two soda-lime-silica glasses, a tube glass (Danner drawing process) and a flat glass (Fourcault drawing process). The reactions in the gas atmosphere are investigated mass-spectrometrically, the changes of the glass surfaces are studied by means of scanning electron microscopy and infrared reflection spectroscopy. The atmosphere doped with tetrafluoromethane has no effect on the glass surface, whereas the treatment with difluoroethane leads to dealkalized glass surfaces and to the incorporation of fluorine into the silicate network. A reaction mechanism is proposed to explain the dealkalization process and the fluorine incorporation.