Unexpected sorption-induced deformation of nanoporous glass: evidence for spatial rearrangement of adsorbed argon.

Sorption of substances in pores generally results in a deformation of the porous matrix. The clarification of this effect is of particular importance for the recovery of methane and the geological storage of CO2. As a model system, we study the macroscopic deformation of nanoporous Vycor glass during the sorption of argon using capacitative measurements of the length change of the sample. Upon desorption we observe an unpredicted sharp contraction and re-expansion peak, which contains information on the draining mechanism of the porous sample. We have modified the theoretical model by Gor and Neimark1 to predict the sorption-induced deformation of (partly) filled porous samples. In this analysis, the contraction is attributed to a metastable or nonequilibrium configuration where a thin surface layer on the pore walls coexists with capillary bridges. Alternatively, pore blocking and cavitation during the draining of the polydisperse pore network can be at the origin of the deformation peak. The results are a substantial step toward a correlation between the spatial configuration of adsorbate, its interaction with the host material, and the resulting deformation.