Dresden 2011 – wissenschaftliches Programm
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DY: Fachverband Dynamik und Statistische Physik
DY 31: Glasses and Glass Transition (jointly with CPP, DF)
DY 31.7: Topical Talk
Donnerstag, 17. März 2011, 12:30–13:00, ZEU 114
Concentration fluctuations and intrinsic confinement effects in binary glass forming liquids: Insights from neutron scattering and X-ray photon correlation spectroscopy — •Thomas Blochowicz1, Sebastian Schramm1, Emmanuel Gouirand1, Philipp Gutfreund2, Bernd Stühn1, Bernhard Frick2, and Yuriy Chushkin3 — 1TU-Darmstadt, Darmstadt, Germany — 2ILL, Grenoble, France — 3ESRF, Grenoble, France
We investigate the dynamics in a series of binary glass forming liquids using dielectric spectroscopy (DS) in combination with quasielastic neutron scattering, dynamic light scattering and X-ray photon correlation spectroscopy (XPCS). It turns out that, although macroscopically the systems are fully miscible in the whole temperature range, two glass transitions can be clearly distinguished due to the high Tg contrast of the components. By means of DS the corresponding relaxation processes are identified, and it turns out that contrary to expectation the small molecules take part in both glass transitions, which suggests that two dynamical species can be distinguished among the small molecules. Moreover, the relaxation connected with the lower glass transition shows properties typical of dynamics in confinement like an Arrhenius-type temperature dependence and a broad distribution of relaxation times. On the other hand it is revealed by XPCS that the concentration fluctuations exhibit a significantly weaker temperature dependence than the α-relaxation and show a crossover from a diffusive to a so-called ballistic wave vector dependence and from stretched to compressed relaxation functions around the upper Tg.