MORPHOLOGY OF POROUS-MEDIA STUDIED BY NUCLEAR-MAGNETIC-RESONANCE

The filling processes of water and cyclohexane in porous silica (40 An gstrom, 60 Angstrom and 112 Angstrom pore size samples) were studied u sing T-2 nuclear magnetic resonance (n.m.r.) experiments. The silica p ores contained water or cyclohexane and the experiments were performed at room temperature and at filling fractions ranging from 0.02 to 1.0 (that is, completely full). Two distinct processes were observed whic h depended on the hydrophilicity of the silica surface (or the surface adhesion of the liquid). Water was found to collect in small puddles in the silica interstices, and to form a surface layer over the silica before the remaining pore volume was filled, Water in a surface-treat ed porous silica and cyclohexane in regular porous silica appeared to completely fill the smaller be-Fore the larger pores, and not form a s eparate surface-coating layer. This work also presents the techniques used to calculate quantitative information about the filling process; specifically, determination of the volume to surface-area ratio of the liquid puddles as well as the number of these puddles, is demonstrate d. (C) 1997 American Institute of Physics.