Domain theory for capillary condensation hysteresis

Abstract

We discuss how the original domain theory for capillary condensation hysteresis [D. H. Everett, The Solid--Gas Interface, Vol. 2 (Marcel Dekker, New York, 1967), pp. 1055--1113] must be modified to account for the presence of the film adsorbed at the pore surface. We show that the original predictions (scanning behavior, congruence) are not valid unless the existence of the adsorbed film is neglected or the dependence of its thickness on the pressure is neglected. We also calculate the scanning curves and subloops that are expected for an assembly of pores having either a regular or irregular (nonconstant) section. These predictions over the scanning behavior within capillary condensation hysteresis can be used to check whether real materials are made up of independent pores or not. Our results are discussed in the light of experiments and density functional theory calculations for adsorption in porous media.