Dresden 2009 – wissenschaftliches Programm

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DY: Fachverband Dynamik und Statistische Physik

DY 12: Poster I

DY 12.2: Poster

Dienstag, 24. März 2009, 14:30–16:30, P1A

Microstructure and Pattern Formation during Zone Melting of Colloidal Crystals — •Thomas Palberg1, Enrique Vilanova Vidal1, Nina Lorenz1, Hans-Joachim Schöpe1, and Hartmut Löwen21Johannes Gutenberg Universität, Institut f. Physik, D-55128 Mainz, Germany — 2Heinrich Heine Universität, Institut f. theoretische Physik II, D-40225 Düsseldorf, Germany

We mimic the zone melting process of metals using colloidal model systems subjected to a gradient in particle interaction. We first study the continuous melting process of a confined one-component colloidal charged sphere crystal pushed up a gradient in salt concentration by a hydrostatic pressure difference along a slit cell. Here we study the dependence of interfacial morphology on system parameters and gradient strength. a polycrystalline to columnar transition is found, persumably caused by the applied shear. In addition we study the melting behavior if the salt is applied homogeneously and no drive is applied. Here we observe a swiss cheese morphology. Finally we study (again without drive) the morphology and the segregation behavior, when a second component is added, taking the role of an impurity. Contaminated crystals melt at low salt concentration, where purified crystals are still stable and in fact reform from the melt via heterogeneous nucleation. A zoo of interesting morphologies including dendrites and phase separation is observed.

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