Regensburg 2007 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 30: Phase transitions III

MM 30.1: Vortrag

Donnerstag, 29. März 2007, 10:15–10:30, H4

nucleation kinetics analysis of pure liquid Gold * a model case? — •Gerhard Wilde¹ and John Perepezko² — ¹Institut für Materialphysik, Universität Münster, Wilhelm-Klemm-Strasse 10, 48149 Münster, Germany — ²Department of Materials Science and Engineering, University of Wis-consin-Madison, 1509 University Avenue, Madison 53706, USA

Flux treatments with a molten glass slag are commonly used to promote deep liquid undercooling or even bulk glass formation. Although the technique has demonstrated frequently the capability to yield large under-cooling, the underlying mechanisms remain uncertain. There are sugges-tions of flux induced *nucleant removal* or *surface site deactivation* interactions, but the effectiveness and operation of these processes have not been identified clearly. As a model system, the undercooling response of pure Au encased in Pyrex glass was studied systematically to develop a consistent record of the undercooling behavior. Nucleation kinetics analy-ses of statistically significant sets of measurements performed under strictly controlled conditions reveal the presence of a new mechanism based on gas-solid interactions that trigger nucleation through a nucleant precipitation reaction as the first step of the interaction. A new model, based on thermodynamic considerations and on the nucleation kinetics data is proposed that accounts for the undercooling increase including initial conditioning, atmosphere effects and undercooling saturation in a self-consistent manner.