Nanofilms of adsorbed water in clay: Mechanism of formation and properties

Abstract

The process of adsorption of water molecules by silicate surfaces of clay minerals is considered. The process leads to the formation of nano-thickness films of adsorbed water. An epitaxial mechanism of nanofilm formation is considered, consisting in the growth of structured hydrate layers under the effect of oxygen and hydroxyl surfaces of clay minerals. The difference between the sizes of hexagonal cells of the solid surface and the forming water film deforms hydrogen bonds and produces inner stress in both the film structure and the mineral lattice. The latter is reflected in the changing size of montmorillonite cell along the b-axis. The thickness of the newly formed adsorption water layer is shown to be controlled by the degree of hydrogen bond deformation, the stress developed inside the nanofilm, the cell size, and the rigidity (strength) of the mineral structure. The deformation of hydrogen bonds and water nanofilm structure determines its specific properties, i.e., wedging pressure, high viscosity, low temperatures of water freezing, dielectric conductivity, etc.