Dislocation model for sorption hysteresis in deformable solids

Abstract Adsorption and desorption branches of sorption isotherms for soft materials often differ from each other even at low relative vapor pressures of the adsorbate. This low vapor pressure hysteresis may result from elastic deformations produced by the capillary tension that condensates exert on pore walls. A dislocation model for materials with very narrow slit pores is proposed. The shape of adsorption/desorption isotherms of soft solids with slit pores depends on a dimensionless parameter, which is proportional to Young's modulus, the square of pore width, and inversely proportional to the adhesion energy of the solid. The model designed for soft solids can be modified to describe low vapor pressure hysteresis in more rigid materials such as hardened cement pastes.