Berlin 2005 – wissenschaftliches Programm

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M: Metallphysik

M 14: Wachstum

M 14.5: Vortrag

Freitag, 4. März 2005, 15:45–16:00, TU H2038

Controlling of symmetry and fractal dimension of Xe dendrites by heating — •Marco Fell, Herman M. Singer und Jörg H. Bilgram — Laboratorium für Festkörperphysik, ETH, CH-8093 Zürich, Switzerland

Xenon dendrites, grown in supercooled melt ( Δ T ∼ 100−200 mK ), show characteristic sidebranching frequencies depending on supercooling. They are statistically symmetric and the contours’ outlines have a characterictic fractal dimension, depending on morphologies: dendrite, seaweed and dendritic doublon.

We experimentally perform periodical heating of the melt close to the melting point and observe a change in the growth morphology of the crystal: The whole dendrite stops growing or even begins to melt, depending on power and duration of heating. After stopping the heating, the liquid xenon cools down and growth restarts. Interestingly four absolutely symmetrical lobes start to grow at the main tip.

This process is found to form crystals with a lower fractal dimension as well as a lower curvature of the contour than known in the morphologies for free growth.