Dresden 2014 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 25: Topical Session: Thermodynamics at the nano scale II - Thermodynamics

MM 25.1: Topical Talk

Dienstag, 1. April 2014, 11:45–12:15, BAR 205

Metal-hydrogen (M-H) systems: a tool for studying changes of thermodynamics and kinetics due to size reduction — •Astrid Pundt — Institut für Materialphysik, Universität Göttingen, Göttingen, Germany

Hydrogen easily solves on interstitial lattice sites in metals. Its high diffusivity results in short alloying times even at room temperature. At 300 K, the intrinsic defect density and the sample shape remains rather stable. This enables us to study thermodynamical and kinetical changes related to size reduction of the metal.

Many size-related effects have been reported during the last years. They are often generated by a mixture of effects due to sample size, micro-structure and mechanical stress contributions.[1] Challenge here is to split those effects related to the size reduction (finite-size effects) from those related to micro-structural changes and the mechanical stress that arises between the sample and the required stabilizer. For this, M-H thin films and M-H clusters serve as model systems. It will be shown that for systems of about 30 nm and larger the classical thermodynamics holds and conventional stress release occurs while for smaller system sizes coherent thermodynamics comes into play and ultra-high stresses are found.

Financial support by the DFG is gratefully acknowledged.

[1] A. Pundt, R. Kirchheim, Ann. Rev. Mat. Res. 36 (2006) 555.