THEORETICAL-STUDIES OF THE AVAILABLE VOLUME FOR ADSORPTION IN A RANDOM QUENCHED AND DEPLETED DISORDERED MEDIUM

The use of a removable template during synthesis of a disordered porou s material can result in a material of greatly differing pore structur e. We present here a theoretical study of the influence of a template on the material's available volume. We model the material as a medium formed by quenching and depleting an equilibrium fluid and develop a t heoretical method by which the available volume for adsorption in this model material may be investigated. This method makes use of the know n relationship between the direct correlation function and the availab le volume. An analysis of the diagrams contributing to the available v olume shows that two types of field points are present: those correspo nding to the density of the medium following depletion (rho) and those corresponding to the density of the original quenched fluid (rho(q)). A perturbation term to the available volume is derived that accounts for the diagrams containing rho(q) field points. The resulting express ion contains only the direct and total correlation function; these qua ntities are known exactly for a hard sphere system within the Percus-Y evick approximation. Using this approach, we show that for materials o f a given density, those formed by depletion can possess available vol umes enhanced by up to an order of magnitude. (C) 1997 American Instit ute of Physics.