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MM: Fachverband Metall- und Materialphysik

MM 36: Topical Session: Thermodynamics at the nano scale IV - Electrochemistry and strain

MM 36.3: Topical Talk

Mittwoch, 2. April 2014, 11:00–11:30, BAR 205

Interface stress effects and critical behavior in nanocrystalline materials — •Rainer Birringer — Universität des Saarlandes, Saarbrücken

We discuss the concept of interface stress in nanocrystalline (nc) materials made up of grain- and/or phase boundaries. Interface stress is an inherent property of any interfacial material manifesting solid-solid or solid-liquid interfaces. In nc metals the stress exerted by interface stress on the abutting crystallites scales as one over grain size and may assume values of the order of several GPa in the limit of small grain sizes. We present data for grain boundary stress in noble metals and address the issue of interface stress at the Ni-Ag phase boundary.

The critical behavior at the para- to ferromagnetic phase transition is usually considered not being dependent on the microstructural details of the system but depends only on the respective universality class, the dimensionality of the space and the symmetry of the order parameter. We studied nc Gadolinium to scrutinize whether or not the randomness and disorder associated with nanocrystallinity may act as a relevant scaling field and so make the system change its universality class, derived from the single crystalline state, when approaching the asymptotic critical regime in the limit of small grain sizes.