Sommaire:

Changes in the structure of network-forming glasses occur in response to applied pressure. Moreover, different amorphous states with distinct short- and/or intermediate-range orders as well as contrasting physical properties can be produced following separate thermomechanical paths. Even if these phenomena, termed polyamorphism, have been extensively studied during the last decades, their complete understanding still remains an ongoing challenge. It relates to the difficulty in carrying out conclusive experiments at high pressure. Vitreous silica is the archetypal tetrahedral network-forming glass whose behavior under pressure is of long-standing interest due to its primary importance as the analog material of silicates in geophysics. At room temperature, the hydrostatic compression is reversible up to ~10 GPa. When compressed above this limit, the recovered glasses after complete unloading exhibit residual densification. The latter saturates at about 20% for maximum pressures around 20-25 GPa.
In this talk, I will present how In situ high-pressure Brillouin light scattering experiments along pressure cycles are used to investigate the compressibility of vitreous silica. And how combined with density data we provide a series of quantitative results related to the transformations along loading-unloading paths. I will also show how, contrary to common wisdom, the residual densification of the recovered silica samples can be figured out from changes in elastic properties along pressure cycles, ruling out a plastic description of the latter process.

Pour plus d'informations, merci de contacter Mebarki M.