| Autor: |
Bonacci F; Navier, Ecole des Ponts, Univ Gustave Eiffel, CNRS, Marne-la-vallée, France., Chateau X; Navier, Ecole des Ponts, Univ Gustave Eiffel, CNRS, Marne-la-vallée, France. xavier.chateau@enpc.fr., Furst EM; Department of Chemical and Biomolecular Engineering, University of Delaware, Newark, DE, USA., Fusier J; Navier, Ecole des Ponts, Univ Gustave Eiffel, CNRS, Marne-la-vallée, France., Goyon J; Navier, Ecole des Ponts, Univ Gustave Eiffel, CNRS, Marne-la-vallée, France., Lemaître A; Navier, Ecole des Ponts, Univ Gustave Eiffel, CNRS, Marne-la-vallée, France. anael.lemaitre@ifsttar.fr. |
| Abstrakt: |
The ageing behaviour of dense suspensions or pastes at rest is almost exclusively attributed to structural dynamics. Here, we identify another ageing process, contact-controlled ageing, consisting of the progressive stiffening of solid-solid contacts of an arrested colloidal suspension. By combining rheometry, confocal microscopy and particle-scale mechanical tests using laser tweezers, we demonstrate that this process governs the shear-modulus ageing of dense aqueous silica and polymer latex suspensions at moderate ionic strengths. We further show that contact-controlled ageing becomes relevant as soon as Coulombic interactions are sufficiently screened out that the formation of solid-solid contacts is not limited by activation barriers. Given that this condition only requires moderate ion concentrations, contact-controlled ageing should be generic in a wide class of materials, such as cements, soils or three-dimensional inks, thus questioning our understanding of ageing dynamics in these systems. |
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