ABSTRACT
The surface geometry of Vycor porous glass was examined by using the relative permeability (PR) technique in a H2O/He system. At a water relative pressure of approximately 0.3, a maximum is observed on the PR curve. This maximum is explained in terms of geometrical changes taking place due to the deposition of a water film on the internal Vycor surface. When the sample is dry, diffusion in a fractal system is found to be more appropriate in describing the process. When the sample is wet, the diffusion process obeys classical Knudsen theory for smooth cylinders. Copyright 1998 Academic Press.
ABSTRACT
The interface geometry of Vycor porous glass was examined by adsorption of water in conjunction with small-angle scattering of X rays and neutrons. When the sample is dry, a fractal surface with a fractal dimension D approximately 2.5 was detected. When wet, a soft hydrogel is formed, resulting in a diffuse boundary. To observe a fractal surface, thorough drying of the sample is necessary, however. It was shown that a small amount of water, 3% w/w, is sufficient to render the surface smooth. Copyright 1997Academic Press
