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Interactions entre contacts solides et cinétique de la condensation capillaire. Aspects macroscopiques et aspects microscopiques.

Abstract : This work concerns the influence of liquid bridges on macroscopical surfaces. It also deals with
the nucleation mechanism of this liquid bridge. The maximum stability angle in a granular material,
also called avalanche angle of glass beads in a rotating drum, is modified if there is some cohesion between
the beads. We have studied: i) the slow evolution of the avalanche angle with the resting time of the
heap. This is called the aging of the avalanche angle. We have shown that aging is not only influenced by
humidity but also by wear. The experiments indicate a smaller aging if the resting angle is far from the
avalanche angle. ii) We also report aging of the apparent friction coefficient of glass beads in presence of an
organic vapour of ethanol. This increase of the adhesion between the beads can be related to an increase
of the wetted area due to capillary condensation. In order to interpret this dynamics, we have studied the
metastability and the effects of nucleation of the capillary condensation. The energy barrier to condense
a liquid bridge is much larger than the thermal energy of the system when the width of the pore tends to
the critical nucleation distance. We then have proposed a model of thermally activated nucleation between
rough surfaces which explain our experiences on glass beads. We have built a new surface force apparatus
to study the statical and dynamical interactions at the length scale imposed by capillary condensation, i.e. at
nanometric level. First results in nanorheology of simple fluids in a confined geometry and of the influence
of the contact time and normal force on adhesion are reported.
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Contributor : Frédéric Restagno <>
Submitted on : Friday, September 6, 2002 - 2:45:10 PM
Last modification on : Thursday, November 21, 2019 - 2:29:41 AM
Long-term archiving on: : Friday, April 2, 2010 - 6:13:39 PM


  • HAL Id : tel-00001627, version 1


Frédéric Restagno. Interactions entre contacts solides et cinétique de la condensation capillaire. Aspects macroscopiques et aspects microscopiques.. Analyse de données, Statistiques et Probabilités []. Ecole normale supérieure de lyon - ENS LYON, 2000. Français. ⟨tel-00001627⟩



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