Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Poster session
MM 23.51: Poster
Dienstag, 26. Februar 2008, 14:45–18:00, Poster B
USAXS measurements of undercooled charged colloidal model systems — •Ina Klassen1, Patrick Wette1, Dirk Holland-Moritz1, Dieter M. Herlach1, Thomas Palberg2, and Stephan V. Roth3 — 1Institut für Materialphysik im Weltraum, Deutsches Zentrum für Luft- und Raumfahrt, 51170 Köln, Germany — 2Institut für Physik, Johannes-Gutenberg-Universität Mainz, 55128 Mainz, Germany — 3HASYLAB, DESY, 22603 Hamburg, Germany
We analyzed a colloidal system of charged silica particles in aqueous dispersion. The crystallization of charged colloids is driven by strong long- range electrostatic interactions between the particles. The main parameter governing the interaction is the surface charge number of the particles that can be varied in a controlled way by addition of sodium hydroxide.
Our system is characterized by convenient time scales of seconds and particle distances of microns and thus accessible by simple, yet powerful optical techniques. Microscopy and light scattering yield complementary information on equilibrium properties and crystallization kinetics from real and reciprocal space (phase behaviour, solidification mechanisms, growth velocities, nucleation rate densities). With these results we can determine the degree of undercooling of our system. 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).