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Reference : UMR8234-VIRMAR-001
Workplace : PARIS 05
Date of publication : Wednesday, May 20, 2020
Scientific Responsible name : Virginie Marry
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
Clay minerals are nanoporous aluminosilicate materials composed of charged sheets. They are widely used in the fields of catalysis, energy and environment because of their remarkable properties of adsorption and retention. A correct description of the properties of the water contained in these materials is crucial to explain and predict the sorption and transport properties of mobile species. In the context of radioactive waste storage in deep geological formation, the DARIUS project seeks to provide a multiscale vision of the mechanisms of water and solutes diffusion, from the scale of the clay layer to that of the stacking of clay particles, under various conditions of partial water saturation. Within this project, the Phenix and IC2MP laboratories are proposing a thesis (CNRS-BRGM funding) to better understand the role of the crystallochemistry of clay minerals and the nature of the charge-compensating cations on the surfaces wettability.
At the theoretical level, Molecular Dynamics and Monte Carlo Grand Canonical simulations will be undertaken in order to determine the thickness of the water films formed in the pores as a function of humidity and to describe the structure and dynamics of water and mobile species at the clay layer scale. At the experimental level, laboratory experiments (measurements of contact angles at the solid / water / air interface and at the solid / oil / water interface) as well as measurements on large instruments ( X-ray reflectivity, XPS under ambient pressure) will be carried out. The experimental results obtained within the framework of the thesis will be compared to the simulation results. So the robustness of the simulation tools will be tested, in particular the force fields used, which constitute the set of equations and parameters necessary to calculate the interactions between atoms. In particular, the existing non-polarizable force fields (clayFF) will be compared to the PIM polarizable force field developed at PHENIX laboratory. At higher scales, this work will be integrated to results obtained in collaboration with the BRGM by various imaging techniques (TXM, X and neutron tomography, ptychography, etc.) in order to determine the impact of the wettability of surfaces on the status of water in partially saturated clay porous media. The objective of this work is to have a molecular description allowing to correctly apprehend the influence of the compositional variability of clay minerals on the structural and dynamic properties of confined fluids which are, at present, imperfectly reproduced.
The thesis will take place at the PHENIX laboratory and will involve strong collaborations with the Poitiers Institute of Chemistry of Environments and Materials (IC2MP, Poitiers) and the Geological and Mining Research Office (BRGM, Orléans).
The PHENIX laboratory (PHysicochemistry of Electrolytes and Interfacial Nanosystems) is a joint research unit of CNRS and Sorbonne University, located on the site of Jussieu in Paris. The phD student will work with Virginie Marry and Pierre Levitz from the Multi-scale Experiences and Modeling team and Laurent Michot from the Inorganic Colloids team.
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