Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Topical Session Heterogeneous Nucleation and Initial Evolution of Microstructure - Poster
MM 23.2: Poster
Dienstag, 24. März 2009, 14:45–16:30, P4
Colloidal model system for undercooled metals — •Ina Klassen1, Patrick Wette1, Dirk Holland-Moritz1, Thomas Palberg2, Stephan V. Roth3, and Dieter M. Herlach1 — 1Institut für Materialphysik im Weltraum, — 2Institut für Physik, Johannes-Gutenberg-Universität Mainz, — 3HASYLAB, DESY, 22603 Hamburg, Germany
Model systems are often used to describe equilibrium properties of simple fluids and solid materials. Charged colloidal spheres in aqueous dispersion show a rich phase behavior and many phenomena known from metals are also observed here, like selection of the metastable phase at large undercoolings. By contrast to metals heterogeneous nucleation can either be efficiently suppressed or, if present, clearly discriminated and separated from data evaluation. Our colloidal particles are characterized by convenient time scales (seconds) and particle distances (300-500nm) and thus accessible by optical techniques. Microscopy and light scattering yield complementary information on equilibrium properties and crystallization kinetics from real and reciprocal space (phase behavior, solidification mechanisms, growth velocities, nucleation rate densities). Structural changes of the melt with increased undercooling and the corresponding changes of the solidification can be monitored by Ultra Small Angle X-Ray Scattering (USAXS) performed at HASYLAB (Hamburg).