Thèses

Jeudi 9 Novembre 2023 à 14h00.

Changes of salt solutions induced by humidity cycles in nanoporous media : evaporation, condensation, crystallization, and deliquescence

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Directeurs de thèse / thesis director :
Olivier Vincent, Jean Colombani

Membres du jury / jury members :

Elisabeth Charlaix (LIPHY, Grenoble)
Denis Morineau (IPR, Rennes)
Noushine Shahidzadeh (Univ. Amsterdam)
Laurent Joly (ILM)
Jean Colombani (ILM)
Olivier Vincent (ILM)

Résumé / Abstract :

The aim of this thesis is to study the phase changes of salt solutions in nanoporous media under the influence of humidity cycles. In such environments, confinement modifies the behavior of the solutions.

We initiated our study with theoretical background and a review of the transport, thermodynamic equilibria and phase changes of a salt solution in a nanoporous medium.

We then developed an experimental set-up to investigate the behavior of a salt solution as it evaporates, crystallizes, condenses, and dissolves within the medium.

Our results enable us to identify the state of the solution and its phase transitions (crystallization, deliquescence) through the analysis of isotherms (water content response to imposed humidity). We then explored the effects of humidity cycles, the initial salt concentration introduced into the medium, and the effect of pore size on supersaturation and humidity at which phase changes occur.

To complement this analysis, we conducted experiments at the DESY synchrotron, which allowed us to observe crystallization and deliquescence through another means : X-ray diffraction. Additionally, we obtained preliminary results regarding the crystallography of confined salts.

Finally, we addressed the dynamical aspect of the problem by studying the transport of a water droplet in a nanoporous medium, more precisely imbibition. Our goal was to understand how imbibition dynamics could be influenced in a medium where pores can be partially filled depending on humidity levels.

To complement this analysis, we conducted experiments at the DESY synchrotron, which allowed us to observe crystallization and deliquescence through another means : X-ray diffraction. Additionally, we obtained preliminary results regarding the crystallography of confined salts.

Finally, we addressed the dynamic aspect of the problem by studying the transport of a water droplet in a nanoporous medium, more precisely imbibition. Our goal was to understand how imbibition dynamics could be influenced in a medium where pores can be partially filled depending on humidity levels.

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