The damage mechanisms involve a complex interplay between chemical reactions and transport problems under strong stress gradients in the neighborhood of glass-environment interfaces (confined or not). The effect of structural and chemical alterations on the local elastic properties and stress fields must also be accounted properly. The damage mechanisms are investigated at the bulk level by spectroscopic techniques, at the nanometer scale by AFM observations and at the molecular level by numerical modeling. This will allow in turn understanding the size effect on these properties. A special attention will be devoted to modeling the densification behavior of anomalous and normal glasses under hydrostatic pressure, as well as the influence of the water contents.
Involved researchers : M. Ciccotti, M. George, A. Grimaldi, G. Pallares, F. Lechenault The investigations on the slow crack propagation in silicate glasses are based on an original experimental setup combining an Atomic Force Microscope (AFM) and a loading setup which allows for very stable and slow crack propagation in a DCDC glass sample. The whole equipment is enclosed in a glove box containing a mixture of nitrogen ant vapour. By combining optical and atomic force microscopy we can monitor in (...)
Involved researchers : M. Ciccotti, M. George, A. Grimaldi, G. Pallares (Collaboration L. Wondraczek, E. Charlaix) The environmental condition at the crack tip has a determinant effect on the propagation processes. In particular, the development of AFM phase imaging techniques has allowed to demonstrate the presence of a capillary condensed phase in the most confined portion of the crack tip cavity. This phase was shown to be in equilibrium with regard to the external atmosphere and to provide (...)
Involved researchers : M. Ciccotti, M. George, G. Pallares (Collaboration C. Marlière, F. Célarié) 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 (...)
Involved researchers : M. Ciccotti, M. Foret, C. Genix, M. George, B. Hehlen, B. Rufflé, C. Weigel The efforts of development of high resolution spatially resolved spectroscopic techniques is aimed at investigating the structural changes related to damage development in glasses, especially concerning the interaction with environmental corrosive molecules like water under elevated stress. This is aimed at complementing the AFM investigations which are presently effectuated around propagating crack (...)
Involved researchers : M. Foret, B. Hehlen, B. Rufflé, H. Tran (PhD), C. Weigel Because of their dominant brittle character, glasses experience plasticity only under high pressure or high stress concentration conditions. In practice, the reference case corresponds to the situation of the mechanical contact. The plastic properties of glasses thus condition their resistance to surface damage. For reasons which are both theoretical (the absence of a crystalline lattice does not allow the use of (...)