Berlin 2008 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 3: SYM Phase Transformations in Metallic Melts II
MM 3.3: Vortrag
Montag, 25. Februar 2008, 12:15–12:30, H 1058
Phase Equilibria of Nanoscaled Systems — •Gerhard Wilde1, Harald Rösner2, Peter Bunzel2,3, and Jörg Weissmüller2,3 — 1Universität Münster, Institut für Materialphysik — 2Forschungszentrum Karlsruhe, Institut für Nanotechnologie — 3Technische Physik, Universität des Saarlandes
The impact of the morphology of the interface of matrix-encased nanoparticles on the melting transition has been investigated. To elucidate the interface contribution clearly, material of identical chemical composition has been synthesized by different processing pathways, resulting in distinctly different interface topologies. These results are discussed with respect of the mechanisms that lead to a size dependence of the melting temperature. Aside from the particle/matrix interfaces, internal heterophase interfaces necessarily occur, if multicomponent and especially multiphase materials are addressed. In multicomponent and nanoscaled alloy systems, interface segregation and interface-induced stresses are known to affect the phase boundary lines of the equilibrium phase diagrams at fixed size. Yet, already the presence of internal heterophase interfaces contributing an excess free energy is sufficient to severely modify the phase equilibrium and the associated phase transformations in nanosize alloy systems. Here, results on the constitutive behavior of binary nanoscaled model alloys obtained by modeling will be highlighted. In addition, experimental results concerning the constitutive behavior of nanoscale alloy systems and concerning a new approach for obtaining nanoscale systems with well-defined size are presented. Support by the DFG is gratefully acknowledged.