Conditions Extrêmes et Matériaux : Haute Température et Irradiation

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M.Naji, F.Piazza, G.Guimbretière, A.Canizarès, Y.Vaills, 'Structural Relaxation Dynamics and Annealing Effects of Sodium Silicate Glass', J. Phys. Chem. B 117 5757 - 5764 (2013) doi:10.1021/jp401112s

Here we report high-precision measurements of structural relaxation dynamics in the glass transition range at the intermediate and short length scale for a strong sodium silicate glass during long annealing times. We evidence for the first time the heterogeneous dynamics at the intermediate range order by probing the acoustic longitudinal frequency in the GHz region by Brillouin light scattering spectroscopy. Or, from in-situ Raman measurements we show that relaxation is indeed homogenous at the interatomic length scale. Our results show that the dynamics at the intermediate range order contains two distinct relaxation time scales, a fast and a slow component, differing by about a tenfold factor below Tg and approaching to one another past the glass transition. The slow relaxation time agrees with the shear relaxation time, proving that Si-O bond breaking constitutes the primary control of structural relaxation at the intermediate range order.