X-ray scattering investigation of swelling clay fabric 1. The dry state

The solid phase geometry of a Na- and Ca-montmorillonite has been investiga ted by using ultra-small- and small-angle X-ray scattering and X-ray diffra ction. The scattering domain covered by combining these techniques correspo nds to characteristic distances ranging from a few angstroms to a micromete r. The intensity scattered on the whole scattering domain was decomposed in to two terms, (i) one assigned to the structure of layers' stacks and (ii) one ascribed to the porous network resulting from the entanglement of indiv idual platelets. The comparison of experimental data with theoretical simul ations revealed that the stacks of clay layers are complex and heterogeneou s. Ordered stacks of approximately 10 layers separated by 9.5 Angstrom seem to be organized in larger particles comprising around 100 layers. Distance s between 25 and 150 Angstrom were observed within those particles. Both sa mples possess a low pore volume fraction of about a few percent, with pores characterized by a highly anisotropic shape. (C) 2001 Academic Press.