M2/PhD Position: Coarsening of foam made from yield stress fluids
M2 Internship/PhD 2021 advertisement
Coarsening of foam made from yield stress fluids
Discipline: Soft Matter Physics
Funding: European Space Agency (ESA) / French Space Agency (CNES)
Internship location: Institut des NanoSciences de Paris, Sorbonne Université, 4 place Jussieu, 75005 Paris and Laboratoire Navier, Rheophysics & Porous Media, Cité Descartes cluster, Bienvenüe building, Champs-sur-Marne
Keywords: experiments, foam, emulsion, complex fluids, microfluidic, elasticity, plasticity, capillarity
Description: Aerated materials are a promising route towards smart light sustainable applications in a variety of domains (building construction, remediation,…). However, controlling the morphology and the functional properties of foamed materials constitutes a difficult task. This is due to the intrinsic aging processes at play in liquid foams1 before the hardening step, among which coarsening remains challenging to be counteracted. This effect is detrimental to the production of well controlled foamed materials. In the building industry for example, lighter foamed construction materials could be produced if coarsening were efficiently controlled. Actually, strong scientific questions remain about coarsening, especially in the case of liquid foams made with complex fluids, such as yield stress foaming fluids. Here we propose to study coarsening properties of foams made with a model yield stress fluid.
The study will be based on the foaming of a concentrated oil-in-water emulsion, which exhibits a simple elastoplastic behavior, i.e. characterized by only two rheological parameters: the elastic modulus and the yield stress. Foams and emulsions will be elaborated with micro- or milli-fluidic devices. Material coarsening will be investigated using several probes and methods: videomicroscopy at the cell wall and bulk diffuse-transmission spectroscopy (DTS) will be used to measure bubble size, diffusing-wave spectroscopy will be used to measure the dynamics of bubbles rearrangements.
This study will benefit from coarsening experiments performed on-board the ISS, where parasitic gravity effects are totally suppressed. The results will be interpreted in order to identify the conditions for which coarsening is efficiently counteracted by the emulsion elasticity and plasticity, in terms of critical dimensionless numbers, as a function of gas volume fraction2,3. Coarsening dynamics in such yield stress foams will be analyzed and compared to dynamics in simple aqueous foams in order to propose a global description of coarsening in foams.
 “Foam: Structure and Dynamics“, Cantat, Cohen-Addad, Pitois, et al., Oxford University Press (2013) ISBN: 978-0-19-966289-0 ;  Gorlier, Khidas, Pitois, Journal of Colloid and Interface Science, 501 (2017) 103-11 ;  Bey, Wintzenrieth, Ronsin, Höhler, Cohen-Addad, Soft Matter, 13 (2017) 6816
Candidate profile: Background in material science (physics/chemistry) or fluid mechanics. A taste in experimental work is expected.
Skills acquisition: Scientific and lab work management. Physics of liquid foam. Modelling. Light scattering spectroscopy techniques. Data and image analysis tools.
Feel free to contact us by email: sylvie.cohen-addad [at] insp.upmc.fr, firstname.lastname@example.org