Fluid-solid transitions on walls in binary hard-sphere mixtures

¹ Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33 St., Philadelphia, PA 19104, USA
² Unilever Research Port Sunlight Laboratory, Quarry Road East, Bebington, Wirral, L63 3JW, UK
³ Department of Physics and Astronomy, The University of Edinburgh, Mayfield Road, Edinburgh, EH9 3JZ, Scotland, UK

Received: 27 June 1997
Accepted: 8 August 1997

Abstract

We present measurements and theory of a fluid-solid phase transition at a hard, flat wall in a two-sized hard-sphere mixture. With particle concentrations well below the level for bulk phase separation, a fluid monolayer (enriched in the larger spheres) forms at the wall. At slightly higher concentrations, the wall-fluid freezes into a wall-solid phase which coexists with the bulk fluid. Measurements of large-sphere area fraction vs. small-sphere bulk concentration in the fluid and solid phases are in reasonable agreement with the predictions of a model that accounts for entropic excluded-volume effects at a flat wall.