Freezing in porous materials: The view from the nanoscale
Speaker: Benoit Coasne, CNRS and MIT
Series: CEE Departmental Seminars
Location: Bowen Hall Auditorium
Date/Time: Monday, October 7, 2013, 4:30 p.m. - 6:00 p.m.
Freezing in porous materials is of fundamental interest in understanding the effect of confinement, reduced dimension, and surface forces on the thermodynamics of liquids and solids. Freezing of liquids confined at the nanoscale is also relevant to applications involving lubrication, fabrication of nanomaterials, soil science, and durability of concrete. In this seminar, I will first describe freezing of simple liquids confined in pores of an ideal geometry and show that the freezing temperature is a function of the pore size and the ratio of the wall/fluid to the fluid/fluid interactions. Then, I will consider the freezing of more complex systems by addressing the specific behavior of water and disordered porous materials. We will see that water crystallization at the pore surface is suppressed because the number of hydrogen bonds formed is insufficient while crystallization in the pore center, unless for large pores, is hindered because curvature prevents the formation of a network of tetrahedrally coordinated molecules. I will also present results showing that crystallization in disordered pores is suppressed (pores < 2 nm) or restricted to the pore center (pores > 2 nm). I will show that there is a crossover between surface-induced and homogeneous crystallization upon increasing the surface disorder of the host material.
Dr. Benoit Coasne obtained his Ph.D. in Physics on capillary condensation in nanoporous materials (Paris, 2003). Then, he worked as a postdoc with Keith Gubbins on freezing of nanoconfined systems (North Carolina, USA). In 2005, he was appointed French CNRS researcher in Montpellier, France. He is currently working in the CNRS/MIT joint department on MultiScale Materials Science for Energy and Environment located on MIT campus. He is member of the bureau of the French Zeolite Society and Cofounder and President of the French Adsorption Society. His research focuses on the thermodynamics and dynamics of systems confined in porous materials.