The aqueous dissolution of alkali silicate glasses: reappraisal of mechanisms by H and Na depth profiling with high energy ion beams

The dissolution of a soda-lime glass has been investigated in three different aqueous solutions (deionised water, 5 M NaCl, and Si rich solutions) and at two temperatures (100 and 2000C), in order to discriminate between proposed models based on ion exchange and/or molecular water diffusion. H and Na depth profiles of leached samples have been obtained with specific resonant nuclear reactions. We show that the variations with depth of both the ratio of incorporated H to released Na and the difference between these quantities are key parameters, suggesting the simultaneous involvement of H+ and H2O in the dissolution of this silicate glass, the dominant species depending on both temperature and solution composition. We tentatively attribute the chemical characteristics of the hydrated layer to the formation of a stoichiometric Ca hydrosilicate. (author)