Locally enhanced dissolution rate as a probe for nanocontact-induced densification in oxide glasses

Atomic force microscopy (AFM) was used to characterize the surface damage (nanoindentations) effect on the chemical durability of glass surfaces (silica and soda-lime silicate glasses, WG). In basic solutions, an enhanced dissolution rate is reported and quantified at indentation sites (+10.5 nm/h and +52 nm/h for silica and WG, respectively) whereas none was observed once the indented surfaces were thermally annealed at 0.9 × T(g) for 2 h, a thermal treatment known for curing high pressure-induced permanent densification in oxides glasses. A direct link between high pressure-induced structural modifications encountered during nanoindentation and the measured dissolution rates is established. It is shown that this property conjointly used with the high resolution of the atomic force microscope may be used for probing, at the nanometer scale, the size and the nature of the structurally modified area underneath residual nanoindentation impressions. As an example, for 10 mN Vickers nanoindentations on WG, the zone affected by the permanently and structurally modified zone under the residual impression is found to be equal to (741 ± 30) nm with a transition zone thickness from the fully densified material to the elastically deformed one ranging between 115 and 165 nm.