THE SURFACE GEOMETRY OF VYCOR

The interface geometry of Vycor porous glass was examined by adsorptio n of water in conjunction with small-angle scattering of X rays and ne utrons. When the sample is dry, a fractal surface with a fractal dimen sion D similar to 2.5 was detected. When wet, a soft hydrogel is forme d, resulting in a diffuse boundary. To observe a fractal surface, thor ough drying of the sample is necessary, however. It was shown that a s mall amount of water, 3% w/w, is sufficient to render the surface smoo th. (C) 1997 Academic Press.