Abstract
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.
Highlights
Silica glass has an estimated theoretical strength of 35 GPa,[1] its extreme sensitivity to surface imperfections or damage is often attributed to the considerably lower strength values reported for bulk samples[2] is often attributed to an extreme sensitivity to surface damage
As the indentation test best mimics everyday life surface aggression, it makes this technique extremely popular and suitable for studying surface damage properties of materials in general. In using this technique it was shown that oxide glasses deform at first elastically and in a permanent way through two concomitant deformation mechanisms: a volume conservative one and a nonvolume conservative one.[4−6] Their relative importance is believed to play a major role in the so-called normal or anomalous behavior exhibited by glasses and may trigger the occurrence of the median/radial crack system,[7] the most jeopardizing crack system regarding the mechanical integrity of glass structures
The effect of nanoindentations on the chemical durability of silica glass and soda-lime silicate glass (WG) in a basic solution was studied by atomic force microscopy
Summary
Silica glass has an estimated theoretical strength of 35 GPa,[1] its extreme sensitivity to surface imperfections or damage is often attributed to the considerably lower strength values reported for bulk samples (of the order of 20 MPa)[2] is often attributed to an extreme sensitivity to surface damage Such surface imperfections or damage often result from the mechanical contact of the pristine glass surface with hard particles. Such an event may leave behind on the surface a permanent imprint and, providing the applied load is high enough, a well developed cracking system.[3] As the indentation test best mimics everyday life surface aggression, it makes this technique extremely popular and suitable for studying surface damage properties of materials in general. Deformation mechanisms are of first importance to understand the nucleation of crack systems under sharp contact conditions
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