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Article Dans Une Revue Journal of Non-Crystalline Solids Année : 2007

Stress-enhanced ion diffusion at the vicinity of a crack tip as evidenced by atomic force microscopy in silicate glasses

Résumé

The slow advance of a crack in soda-silicate glasses was studied at nanometer scale by in-situ and real-time atomic force microscopy (AFM) in a well-controlled atmosphere. An enhanced diffusion of sodium ions in the stress-gradient field at the sub-micrometric vicinity of the crack tip was revealed through several effects: growth of nodules in AFM height images, changes in the AFM tip–sample energy dissipation. The nodules patterns revealed a dewetting phenomenon evidenced by ‘breath figures'. Complementary chemical micro-analyses were done. These experimental results were explained by a two-step process: (i) a fast migration (typical time: few milliseconds) of sodium ions towards the fracture surfaces as proposed by Langford et al. [J. Mat. Res. 6 (1991) 1358], (ii) a slow backwards diffusion of the cations as evidenced in these AFM experiments (typical time: few minutes). Measurements of the diffusion coefficient of that relaxing process were done at room temperature. Our results strengthen the theoretical concept of a near-surface structural relaxation due to the stress-gradient at the vicinity of the crack tip. The inhomogeneous migration of sodium ions might be a direct experimental evidence of the presence of sodium-rich channels in the silicate structure [A. Meyer et al., Phys. Rev. Let. 93 (2004) 027801].

Dates et versions

hal-00407634 , version 1 (27-07-2009)

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F. Celarie, M. Ciccotti, Christian Marliere. Stress-enhanced ion diffusion at the vicinity of a crack tip as evidenced by atomic force microscopy in silicate glasses. Journal of Non-Crystalline Solids, 2007, 353 (1), pp.51-68. ⟨10.1016/j.jnoncrysol.2006.09.034⟩. ⟨hal-00407634⟩
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