OBSERVATION OF CLAY MINERAL SWELLING BEHAVIOR VIA STANDARD TRANSMISSION ELECTRON MICROSCOPE

Abstract

In order to clarify the swelling mechanism in swelling clay minerals, this study attempted direct observations of clay minerals using standard transmission electron microscopy (TEM). In order to directly observe the clay mineral interlayer spaces during swelling, resin-embedded specimens were created via ultramicrotomy. The results of the observations demonstrate that the basal spacing of swelling clay minerals grows in stages as relative humidity increases, which is consistent with the results of previous studies. Partial dehydration was observed in some specimens, but the study demonstrated that even standard TEMs are capable of observing swollen clay minerals under vacuum conditions obtained through resin embedding. Furthermore, analyses of the amounts of water molecules adsorbed via energy-dispersive X-ray spectroscopy (EDS) confirms that the amount of adsorbed water molecules changes as the water molecule layer forms. This study also demonstrated that the amount of water molecules adsorbed to swelling clay minerals tends to increase in stages, whereas this amount increases continuously in non-swelling clay minerals, demonstrating a difference in the adsorption processes.