Pore lattice deformation in ordered mesoporous silica studied by in situ small-angle X-ray diffraction.

Sorption and capillary condensation of an organic fluid in ordered mesoporous silica were studied by in situ small-angle X-ray diffraction using synchrotron radiation. The sorption isotherm was calculated from the sample transmission data. The diffraction peaks resulting from the periodic hexagonal arrangement of the pores show characteristic changes of intensity, position and width, and a pronounced hysteresis of these parameters in the capillary condensation/evaporation regime was observed. The change of the peak positions with gas pressure is related to pore lattice deformations due to capillary stresses occurring at the gas–liquid phase transition. [ABSTRACT FROM AUTHOR]