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Reference : UMR7608-GEOGAU-001
Workplace : ORSAY
Date of publication : Thursday, May 14, 2020
Scientific Responsible name : Georges Gauthier
Type of Contract : PhD Student contract / Thesis offer
Contract Period : 36 months
Start date of the thesis : 1 October 2020
Proportion of work : Full time
Remuneration : 2 135,00 € gross monthly
Description of the thesis topic
Research in line with the pioneer work of Pickering succeeded recently to produce new objects which can be described as gas pockets in air and are named gas marbles . They are made of gas surrounded by a layer of grains constrained by thin liquid film in gas environment. The exceptional mechanical strength of their granular shell promise them to many applications  (for example: gas encapsulation, generation of materials with hierarchical porosity, acoustic insulation, vibration dampers).
The aim of the PhD is to characterize and to understand the rheological behavior of granular films. At the microscale the rheology depends on 3 mechanisms: capillary bridges, grains contact and energy dissipation due lubrication flow between the grains and at the interface liquid/air.
The PhD work will start with the experimental determination of the shear viscosity of granular films using an MCR 501 rheometer. This study will be completed with the measurement of the grains displacement during shearing. Taking advantage of the two dimensional nature of the material, the position of each grains will be obtained by visualization and image processing. These experimental results will be analyzed in the framework of the generic granular suspension rheology, mu(I) . Within this framework, confinement pressure should be the key parameter, with two ways of varying it; the contact angle between the grains and the fluid, and the global pressure in the liquid film that can be controlled independently. Finally, the study will be completed with out of plane solicitation in the aim of improving the gas marble generation processes.
 Y. Timounay, O. Pitois, F. Rouyer, Gas Marbles: Much Stronger than Liquid Marbles, Phys. Rev. Lett. (2017). doi:10.1103/PhysRevLett.118.228001.
 “Gas Marbles” Store Air in Strong Spheres, June 2, 2017• Focus Physics 10, 62. “Fortified gas marbles are 10 times stronger than regular bubbles”, Daily news, News Scientist, 8 June 2017. “Gas marbles are tough when squeezed”, Physics Today, 5 Jul 2017 in Research & Technology.
 F. Boyer, É. Guazzelli, O. Pouliquen, Unifying suspension and granular rheology, Phys. Rev. Lett. (2011). doi:10.1103/PhysRevLett.107.188301.
This PhD work is part of a ANR (French Agency of Research) project : PRC PhyGaMa starting January 2020 which concerns the PHysics of GAs MArbles. The project joins researchers from two laboratories : NAVIER (UMR CNRS, Ecole des Ponts et Université Gustave Eiffel) and FAST (UMR CNRS, Université Paris-Saclay).
This PhD will be conducted within the Granular and suspension team from FAST Laboratory, in close cooperation with the Navier's team.
The candidate must have a degree Master degree (or engineer diploma) in Physics or Mechanics. The post requires knowledge of hydrodynamic, soft matter or granular matter as well as good level of communication skills, both oral and written (French and English required). Motivation, seriousness, ability to work independently and as part of a team will be taken into account during recruitment.
Applications must include a detailed CV; at least two references (people who may be contacted); a one page letter; a one-page summary of the master's thesis; grades
for the Masters 1 or 2 or the engineering degree).
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