Moisture-induced ageing in granular media and the kinetics of capillary condensation

In 1773 Coulomb recognized that the static properties of granular systems can be discussed in terms of the frictional properties between different layers, leading to his relationship between the angle of repose of a granular pile ( 0) and the coefficient of static friction µ s: tan  0 =µs. Two centu...

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Bibliographic Details
Published in:Nature (London) 1998-12, Vol.396 (6713), p.735-737
Main Authors: Bocquet, L, Charlaix, E, Ciliberto, S, Crassous, J
Format: Article
Language:English
Subjects:
Aging
Angle of repose
Bridges (structures)
Capillarity
Condensed matter: structure, mechanical and thermal properties
Condensing
Cross-disciplinary physics: materials science
rheology
Exact sciences and technology
Friction
Granular solids
Humanities and Social Sciences
Kinetics
letter
Material form
Media
multidisciplinary
Physics
Rheology
Science
Science (multidisciplinary)
Solid-fluid interfaces
Static friction
Surfaces and interfaces
thin films and whiskers (structure and nonelectronic properties)
Wetting
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Summary:In 1773 Coulomb recognized that the static properties of granular systems can be discussed in terms of the frictional properties between different layers, leading to his relationship between the angle of repose of a granular pile ( 0) and the coefficient of static friction µ s: tan  0 =µs. Two centuries later, solid friction and granular media still present many puzzles. One such is that the coefficient of static friction depends on the time during which the solids remain in contact before the measurement. Here we show that this ageing effect is manifested too in the angle of repose of granular media and originates from capillary condensation of water vapour between the packed particles, leading to the formation of water bridges. By assuming that the kinetics of this process are governed by the thermally activated nucleation of bridges, we can reproduce both the time- and humidity-dependence of the ageing behaviour. Our results also clarify the kinetics of adsorption in porous media more generally.
ISSN:0028-0836
1476-4687
DOI:10.1038/25492