Dresden 2006 – scientific programme

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MM: Metall- und Materialphysik

MM 40: Nanostructured Materials III

MM 40.3: Talk

Friday, March 31, 2006, 11:30–11:45, IFW D

Elastic Properties of nanocrystalline palladium — •Markus Thirion and Rainer Birringer — Universität des Saarlandes, FR 7.3 Technische Physik, Postfach 151150, 66041 Saarbrücken

We investigate the elastic properties of nanocrystalline palladium by means of velocity of sound measurements. The samples are prepared by inert-gas condensation and compaction and have grain sizes ranging from 10 to 25 nm. Due to an unavoidable residual porosity, the specimen densities lie in the range between 90 and 95% of the bulk density of coarse-grained palladium. From the velocities of longitudinal and transversal polarized ultrasonic waves, the elastic moduli (Young’s, shear and bulk) can be determined. In the low porosity regime (<10%), we find a linear dependence of moduli versus porosity, allowing to extrapolate the moduli of the pore-free material state. The extrapolation reveals slightly enhanced effective moduli of the nanocrystalline palladium (pore-free), as compared to the coarse-grained reference material. This enhancement will be discussed in terms of a rule of mixture approach for a two-phase system made up of crystalline grains and grain boundaries.