Regensburg 2010 – scientific programme

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DY: Fachverband Dynamik und Statistische Physik

DY 9: Granular Matter/ Contact Dynamics I

DY 9.4: Talk

Tuesday, March 23, 2010, 10:45–11:00, H47

A Lattice Model with Fragmentation and Reagglomeration — •Alexander Weuster, Lothar Brendel, and Dietrich E. Wolf — Universität Duisburg-Essen, Fachbereich Physik and CeNIDE, 47048 Duisburg, Germany

Van der Waals forces play a major role in the formation-process of uncharged nanoparticles, since they exceed other forces, such as gravity. Agglomerates of ultra-fine cohesive particles, often referred to as nanopowders, can reach porosities up to 98 %. In fact, the porosity of a nanopowder plays a key-role in industrial application e.g. gas sensors, catalysts and diesel soot traps.

Aerosol aggregation processes produce fractal clusters, which increase, when deposited, the porosity of a nanopowder, in contrast to single particle deposition processes (Mädler et al. 2006). A new algorithm to create such a fractally substructured nanopowder was proposed by Schwager, Wolf and Pöschel(2008). Based on this work, we present a lattice model to generate such nanoparticle agglomerates in two and three dimensions. Fragmentation is done by a sieving procedure with a prescribed mesh size, followed by a ballistic deposition. Continous fragmentation and reagglomeration lead to a steady state configuration with a fractal substructure. By tuning the mesh size, the model is capable of producing agglomerates of arbitrarily high porosity. Results for fractal dimension, mass-distribution of the fragmentation process and scaling-relations are discussed.