Tensile effect on a confined phase.
To prove that a tensile effect operated in pores due to a concave meniscus of a capillary-condensed liquid, we measured the X-ray diffraction pattern of capillary-condensed Kr in the spherical cavities of KIT-5 ordered mesoporous silica at three temperatures of 90, 92, and 94 K when the vapor pressure was successively decreased from its saturation value. The capillary-condensed Kr takes a solid form at 90 K, although it remains in a liquid form at 92 and 94 K. For all three temperatures, the position of the main diffraction peak of the confined Kr shifted to lower scattering angles with a decrease in pressure of the vapor in equilibrium with the adsorbed Kr, indicating expansion of the confined Kr phase. The expansion observed is well accounted for by the tension due to a concave meniscus of a liquid in small channels connecting directly to the vapor phase outside.
Morishige
Kunimitsu
K
Department of Chemistry, Okayama University of Science, 1-1 Ridai-cho, Okayama 700-0005, Japan.
Yasunaga
Hiroaki
H