Regensburg 2007 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 22: Granular matter / contact dynamics I

DY 22.3: Talk

Wednesday, March 28, 2007, 16:15–16:30, H2

In-situ investigation of the structural and electrical properties of nanosized silicon powders — •Ingo Plümel^1,2, Hartmut Wiggers², and Axel Lorke¹ — ¹Experimental Physics and CeNIDE, University Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany — ²Institute of Combustion and Gas Dynamics, University Duisburg-Essen, Lotharstr. 1, 47057 Duisburg, Germany

Nanosized Silicon powders were characterized by determining in-situ the conductivity, impedance, and mechanical compaction while applying a mechanical pressure. In porous systems like powders, the macroscopic electrical properties result from transport mechanisms such as hopping and tunneling between particles as well as from structural properties such as the amount and shape of particle contacts. Thus the density change of the powder during electrical measurements was characterized by means of a laser interferometer. Conductivity measurements as a function of the applied pressure show an exponential dependence for nanosized particles and a power law for microsized particles which can be partly associated to scaling effects for decreasing particle size. A time dependent change in conductivity together with an increase in density was observed while applying a constant pressure suggesting friction limited compaction of the powder. To separate the contributions of the particle cores and particle contacts to the complex conductivity and capacity, impedance spectroscopy was performed. In agreement with the observed compaction of the powder, the spectra show a strong increase of the sample capacity and conductivity as a function of the applied pressure.