Structure and phase behavior of fluids in porous media
Date of Issue2011
School of Chemical and Biomedical Engineering
Fluids confined within pores, which are micro- to nanometer size in one dimension have been investigated in recent years due to unusual properties of these confined fluids as compared to those of the bulk. Their practical applications can be sought in the fields of capillary condensation, gas adsorption, and transport phenomena in porous materials. In such areas, the common geometries of confinement can be simplified as the slit, cylindrical and spherical shapes representing complex porous media. The experimental restriction due to small size stimulates molecular modeling approach to be an apt choice for characterizing atomistic behaviors in pores. Many studies have been conducted to understand phase behavior, thermodynamic properties, and packing of fluid molecules in the pore, yet there are little known about the dependence of phase behavior and structure in terms of different pore sizes and pore structure, in which our aim for this work lies. We first construct the simple cylindrical and spherical pores, which exert either repulsive or attractive forces on fluid particles, which exhibit simple model potentials; hard sphere and square-well. We investigate the thermo-physical properties by determining the equation of states using classical molecular dynamics method. Density profiles, axial distribution function, structure factor and bond order parameters are emphasized to reveal structural properties of fluid-like and solid-like ones. Next, we extend the simple confinement geometries to structural walls of realistic porous media such as single-walled carbon nanotubes (SWCNTs). The influences of the surface chirality of the SWCNTs to the confined fluid are investigated in terms of solidification.
DRNTU::Engineering::Chemical engineering::Chemical processes