Synchrotron x-ray scattering studies of water intercalation in a layered synthetic silicate.

Synchrotron x-ray diffraction studies were performed on a synthetic layered silicate Fluorohectorite clay. Diffraction patterns along the stacking direction were obtained in surface reflection and bulk transmission geometries on bulk pressed samples under controlled temperature and relative humidity. One-dimensional structure factors modeling the positions of the intercalant atoms have been obtained for three stable hydration states. From the narrow (00l) peak widths we conclude that well-crystallized domains consist of stacks of about 100 platelets, forming crystallites of the order of 0.1 microm thick. These crystallites have an orientational angular distribution of about 24 degrees around the stacking direction and represent the solid framework for microporosity in these samples.