Studies of the entrapment of non-wetting fluid within nanoporous media using a synergistic combination of MRI and micro-computed X-ray tomography

Three-dimensional magnetic resonance imaging (MRI) and micro-computed x-ray tomog. (micro-CXT) were combined to study the entrapment of mercury within nanoporous silica materials following porosimetry. MR images were used to construct structural models of particular porous media within which several simulations of mercury intrusion and retraction were performed with variations in the mechanism for the snap-off' of the mercury menisci. The simulations gave rise to different predictions for the pattern of the macroscopic ( > 10 micro m ) spatial distribution of entrapped mercury, depending on snap-off' mechanism, which were then compared with corresponding exptl. data obtained from micro-CXT images of real pellets contg. entrapped mercury. The information obtained from the micro-CXT images, and also from the porosimetry curves themselves, was then used to constrain a model for the microscopic mercury retraction mechanism. Addnl. predictions of the retraction model were then subsequently confirmed using scanning loop expts. The simulations showed that the overall level of entrapment of mercury was detd. by the close interaction between the pellet macroscopic structure (particularly pore size spatial correlation), and the microscopic mercury retraction mechanism. Hence, it was subsequently possible to explain fully why high mercury entrapment occurred within one particular type of sol-gel silica material, while only low entrapment occurred in another batch of superficially similar material. [on SciFinder (R)]