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 23.3: Poster

Dienstag, 24. März 2009, 14:45–16:30, P4

Heterogeneous nucleation in charged colloidal model systems using spherical seeds: Controlling the crystallization kinetics — •Andreas Engelbrecht, Roushdey Salh, Thomas Palberg, and Hans Joachim Schöpe — Johannes Gutenberg-Universität Mainz, Institut für Physik, Staudinger Weg 7, 55099 Mainz, Deutschland

In the classical crystallization scenario three processes can be discriminated: crystal nucleation, growth and ripening. The crystallization kinetics and the resulting morphology of the polycrystalline material are given by a complex interplay of these mechanisms. Controlling nucleation and growth is one key to create new materials. A great deal of progress has been made in recent years using colloidal suspensions as model systems studying crystallization. Close analogies to atomic systems are observed which can be exploited to address questions not accessible in atomic solidification. We here present systematic measurements controlling the crystallization kinetics of a charged colloidal model system by adding small amounts of a second higher charged component. Using small amounts of the second component the nucleation rate is strongly accelerated whereas crystal growth is only slightly influenced. At large amounts the crystallization process is overshadowed by fractionation of the supersaturated fluid: nucleation is delayed and crystal growth slowed down. The average crystal size of the resulting polycrystalline material can be changed by a at least one order of magnitude. The crystal size distribution is strongly influenced in its shape as well.