What is the reason for hysteresis loop at high relative pressure (0.8-1.0 p/po) in N2 ads-des isotherm?

I am getting a high pressure hysteresis loop for a porous material in the p/po range of 0.8-1.0. The hysteresis loop is well-defined. What may be the plausible mechanism for the high pressure...

18 November 2014 2,411 11 View