Laboratoire Charles Coulomb UMR 5221 CNRS/UM2 (L2C)


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Density fluctuations in glasses, investigation through small angle X-ray scattering

par Sébastien LAYSSAC - publié le , mis à jour le

The amplitude of density fluctuations in a glass strongly depends on its thermal history, a glass frozen at high temperature is significantly more disordered than a glass with the same composition and frozen at a lower temperature. These measurements also allow determining the compressibility in the glassy state. Temperature scanning small-angle X-ray scattering can also be used as a tool to characterize the glass transition in vitreous silica or binary SiO2-Al2O3 glasses (this technique offers an alternative to dilatometry or calorimetry techniques in glasses were those measurements are difficult due to the high glass transition temperature. Collaboration with A. Faivre (GES, Montpellier), R. Bruning (University Mount Allison, Canada), JL. Hazemann (ESRF), JP Simon (Laboratoire de thermodynamique et Physico-chimie métallurgiques, Grenoble), R. Le Parc (LCVN), B. Champagnon (LPCML, Lyon).

Study of the influence on density fluctuations and first sharp diffraction peak induced near the glass surface by ionic implantation. Ionic implantations are used to mimic irradiation effects, but the induced modifications are confined to the surface of the glass. We have performed a GISAXS (grazing incident small angle x-ray scattering) study in order to probe the modifications of density fluctuations at nanometer scale and structure at slightly larger scattering vector near the glass surface at several probing depth in silica and borosilicate glasses, and for several kind of implanted atoms and implantations energies. Collaboration with A Faivre (GES, Montpellier) et Sylvain Peuget (CEA Marcoule)

Scattered intensity extrapolated to q=0 as a function oftemperature, for samples having different fictive temperatures. The temperature dependent term due to phonons Iph calculated from Brillouin measurements of J. Phys. : Conds. Matter 18 7507, is plotted with dashed lines shifted up of 18 e.u./molecule for clarity - © L2C

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