Master 2ème année
Année 2014-2015
PROPOSITION DE SUJET DE STAGE
Nom du laboratoire : Laboratoire de Physique des Solides
Adresse : Centre Scientifique d’Orsay, Bâtiment 510, 91405 Orsay CEDEX
Nom du ou des responsables du stage : Alesya Mikhailovskaia et Anniina Salonen
E-mail : alesya.mikhailovskaia@u-psud.fr , anniina.salonen@u-psud.fr
Téléphone : 01 69 15 59 86, 01 69 15 53 88
Page web : http://chercheurs.lps.u-psud.fr/Sil/spip.php?article47
Possibilité de poursuivre en thèse : oui
non X
Titre : How does a colloidal gel form inside a foam ?
Résumé : Colloidal particles (particles with a radius from a few nms to µms) can aggregate
and form space spanning networks of elastic gels under the right conditions. The structure of
the aggregates and the gels depends intricately on the interaction potential between the
particles. Fortuitously in the case of colloidal particles we have many levers to control these
interactions, allowing us to play with the detailed phase behaviour of the particles and the
strength of the resulting structures. This makes them particularly interesting for the design
of light materials with interesting mechanical properties using foams.
Bubbles dispersed in an aqueous phase constitute a foam and they are surrounded by a
network of interconnected channels, composing the foam skeleton (see Figure below). The
size of the channels can be controlled through the bubble size and the liquid fraction within
the foam. The aim of the project is to study colloidal gel formation inside the foam skeleton.
We want to understand both how the silica gel develops when constrained inside the soft
walls of the foam network, the influence of confinement on colloidal gel formation. Secondly
we want to use the stable foams
generated to make solid foams through
evaporation of the water phase,
controlling the microstructure of the
solid foams.
The experimental project will use colloidal silica particles, which can be made to gel either
through the addition of electrolytes or depleting polymers. The main interest of the project
is the multiscale approach to the characterization of the gelification process. The local
structure of the gels will be probed using small angle neutron scattering and the dynamics
of the particles using light scattering (diffusing wave spectroscopy).
[1] L. Arriaga, W. Drenckhan, A. Salonen, J. Rodrigues, R. Íñiguez-Palomares, E. Rio and D.
Langevin, On the long-term stability of foams stabilised by mixtures of nano-particles and
oppositely charged short chain surfactants. Soft Matter,8, 11085-11097 (2012).