Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 10: SYM Phase Transformations in Metallic Melts IV
MM 10.5: Vortrag
Montag, 25. Februar 2008, 17:30–17:45, H 1058
From solid solutions to the onset of compound formation and eutectic mixtures in binary charged colloidal suspensions — •Thomas Palberg1, Nina Lorenz1, and Patrick Wette2 — 1Institut f. Physik, Johannes Gutenberg Universität Mainz, — 2Institut f. Materialwissenschaft im Weltraum, DLR, Köln
Aqueous colloidal charged sphere suspensions closely mimic the behaviour of metals on a mesoscopic model level. We here ask, whether this also holds for their binary mixtures. We studied the structure, elasticity and solidification kinetics of such mixtures as a function of mol fraction x and total particle density n. At an interaction ratio s = AA/BB = 1 we observe solid solutions of bcc structure, with elasticity and solidification kinetics varying linearly with composition [1]. The onset of compound formation, with extended stability of the crystal phase and corresponding anomalies in elasticity and solidification kinetics occurs at s<0.7. Most recently we found an eutectic behaviour for s=0.55 at x=0.7 with a strongly increased melt stability [2]. Close to the eutectic composition solidification kinetics are dramatically slowed. Our observations are discussed in relation to colloidal mixtures of different interactions (hard spheres, oppositely charged spheres) but moreover carefully analyzed in view of the possible extension of the role of colloids as model systems going from single component to binary systems.
[1] P. Wette, H. J. Schöpe, T. Palberg, J. Chem. Phys. 122, 144901 1-8, (2005).
[2] N.Lorenz, J.Liu, T. Palberg, Colloids Surf. A (at press 2007)