THE CHEMICAL ANALYSIS OF DIFFERENTLY PREPARED GLASS SURFACES - THE COMPARISON BETWEEN EDX AND XRF

Abstract

Two sets of model glasses differing by molar fractions of bridging (BO) and non-bridging (NBO) oxygens and of Q³ and Q⁴ structural units were prepared. Glasses in each set are isostructural on BO/NBO level that means the fractions of BO and NBO are the same. The groups mimic Float glass and the commercial barium crystal glass. The study compares three different ways of glass surface preparation in order to find the most realistic results of chemical analyses. The studied surfaces were: i) the original surface created by melting and exposed to the ambient atmosphere, ii) polished sample routinely prepared in way common for X-ray microanalysis, and iii) freshly fractured surface. Glasses were also analysed by XRF and the results were compared with the EDX analysis. The data suggest the EDX analysis of fresh fractures provide the most realistic composition. The comparison of XRF and EDX provide useful insight into the differences between two methods and further enhances the complexity of the glass surface study. While XRF offers a reliable analysis of bigger volume and provides averaged composition, EDX yields a more realistic surface and local composition. EDX of freshly prepared fractures revealed strong sodium enrichment on the surface due to the active participation of this element in the relaxation of the newly formed surface.

Keywords

• silicate glass
• glass surface
• chemical analysis
• edx
• glass corrosion