Observation Technique for Wet Clay Minerals Using Film-Sealed Environmental Cell Equipment Attached to High-Resolution Electron Microscope

Abstract

We have been developing wet cell microscopy to observe hydrated materials using a film-sealed environmental cell (or hydration chamber, abbreviated as EC) (Fukami and Dukushima, 1984). By using the EC device equipped with a conventional electron microscope, atmospheric pressure around the specimen in the EC can be easily controlled from higher pressure than 1 atm to high vacuum down to 10^-3 Torr. If wet gas containing saturated water vapor is circulated in the EC as the environmental gas, the “real features” or “natural hydrated state” of some wet clay minerals, such as halloysite, montmorillonite, and vermiculite can be observed by electron microscopy without any undesirable structural or morphological deformation resulting from specimen dehydration. Specimen holders in which the EC is set have been manufactured for a 100-kV electron microscope (JEM-7A), including four top-entry and one side-entry types in series with improvement (Fukami and Fukushima, 1984). We have carried out in situ observations on the behavior of hydrated materials according to the environmental change: (1) morphological and structural change caused by evacuation around the specimens after observing them in wet gas environment, (2) chemical reaction processes between specimens and liquid chemicals injected into the EC during observation (Fukushima et al., 1987). Recently, we manufactured a new side-entry type EC holder and its related equipment for dynamic observation with high resolution (Fukami et al., 1987).