Silica glass devitrification enhancement by a drop of sodium hydroxide saturated solution

Abstract

This study investigates silica glass devitrification achieved 2 h after applying a drop of NaOH saturated solution at 200 °C-1000 °C. At 200 °C and 300 °C, the liquid phase including bubbles presumed to be water glass is observed from behind the silica glass slab. A crystalline layer with X-ray diffraction (XRD) peaks of Na2CO3 crystal covers the water glass front. We observed weak peaks of sodium metasilicate (Na2SiO3) at 500 °C. At 600 °C and 700 °C, these peak intensities observed at 500 °C became higher along with the polycrystalline domain. At 700 °C, XRD peaks of quartz and cristobalite were observed along with the peaks observed at 500 °C-600 °C: 100 °C lower than that of devitrification temperature obtained when NaCl crystal grains react with silica glass. At 800 °C, XRD peaks of cristobalite and sodium disilicate (Na2Si2O5) were observed. At 900 °C and 1000 °C, we observed only pure silica crystal peaks of cristobalite and tridymite.