Direct observation of cooperative effects in capillary condensation: The hysteretic origin

We tailor anodized alumina with pores with well-defined, simple geometries, in order to study the effects of constrictions in hysteretical capillary condensation, independently from other cooperative processes such as network effects. We confirm, by direct observation using optical interferometry, the occurrence of two cooperative phenomena: the classical pore blocking effect in nearly ideal “inkbottle” pores and the advanced adsorption in pores with a change in the cross section. They are relevant for the development of a theory of the poorly understood hysteresis in complex porous materials.