Coupling between aging and convective motion in a colloidal glass of Laponite

Ludovic Bellon (1) , Mathieu Gibert (1) , Rodrigo Hernández (2)

1 Phys-ENS - Laboratoire de Physique de l'ENS Lyon
2 LEAF-NL - Laboratorio de Estudios Avanzados en Fenomenos No Lineales, Departamento de Ingeniería Mecánica

We study thermal convection in a colloidal glass of Laponite in formation. Low concentration preparation are submitted to destabilizing vertical temperature gradient, and present a gradual transition from a turbulent convective state to a steady conductive state as their viscosity increases. The time spent under convection is found to depend strongly on sample concentration, decreasing exponentially with mass fraction of colloidal particles. Moreover, at fixed concentration, it also depends slightly on the pattern selected by the Rayleigh Bénard instability: more rolls maintain the convection state longer. This behavior can be interpreted with recent theoretical approaches of soft glassy material rheology.

Mots clés: Convection; Laponite; soft glassy material; aging; rheology

Domaines: Matière Molle [cond-mat.soft]; Mécanique des fluides [physics.class-ph]; Dynamique des Fluides [physics.flu-dyn]

Ludovic Bellon, Mathieu Gibert, Rodrigo Hernández. Coupling between aging and convective motion in a colloidal glass of Laponite. 2006. ⟨ensl-00121535v1⟩