Berlin 2008 – wissenschaftliches Programm
Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe
CPP: Fachverband Chemische Physik und Polymerphysik
CPP 26: Micro and Nano Fluidics I: Liquids at structured materials
CPP 26.4: Vortrag
Mittwoch, 27. Februar 2008, 15:00–15:15, C 264
Liquid morphologies in random assemblies of spherical beads — •Martin Brinkmann1, Mario Scheel1, Daniel Hornung1, Marcus Schwamberger1, Ralf Seemann1,2, and Stephan Herminghaus1 — 1MPI for Dynamics and Self-Organization, 37073 Göttingen — 2Saarland University, D-66041
Small amounts of wetting liquids mixed into a random assembly of spherical glass beads are present in the form of capillary bridges between adjacent beads. At higher liquid content these bridges coalesce into larger liquid structures that eventually percolate the whole assembly. Inspired by recent X-ray microtomography data we examine the liquid morphologies in local triangular configurations of spheres where two pairs of spheres are in mutual contact while the remaining pair forms a small gap. Using numerical minimizations of the interfacial energy we predict the appearance of certain liquid morphologies as controlled by their volume, respectively, Laplace pressure, contact angle, and gap separation. The morphology diagram can be quantitatively compared to wetting experiments using isolated triangular configurations of spherical beads. Based on these results we propose a simple model to describe the consecutive coalescence of capillary bridges. This model allows to predict the percolation transition of liquid structures in a pile of beads solely based on the contact angle and the local packing geometry.