Berlin 2008 – wissenschaftliches Programm

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MM: Fachverband Metall- und Materialphysik

MM 45: Nanostructured Materials VI

MM 45.3: Vortrag

Donnerstag, 28. Februar 2008, 15:30–15:45, H 0111

Elastic properties of argon adsorbed in nanoporous glass — •Klaus Schappert and Rolf Pelster — Universität des Saarlandes, FR 7.2 Experimentalphysik, Campus E 2.6, D-66123 Saarbrücken

We have performed isothermal adsorption and desorption experiments on argon in nanoporous Vycor. The effective shear modulus has been determined measuring the amount of absorbed argon as well as the ultrasonic velocity near 12.5 MHz. Since fluids cannot sustain shear stress, argon only affects the effective shear modulus at temperatures below its freezing point ( T_f,conf<T_f,bulk). Depending on the filling fraction, three different behaviours are observed: (i) The first adsorbed argon layers do not contribute to the measured shear modulus. (ii) In an intermediate range the shear modulus increases linearly with increasing argon content. (iii) At a characteristic filling fraction an abrupt enhancement of the shear modulus is observed. We discuss these phenomena in terms of capillary sublimation and crystallization.