IN SITU ATOMIC FORCE MICROSCOPY (AFM) INVESTIGATIONS OF CLAY MINERAL SWELLING

Atomic force microscopy (AFM) was used to observe the swelling behavior of single nontronite quasi-crystals in an aqueous environment. The nanometer-scale changes in the interlayer spacing were directly observed in situ during cation exchange processes. The basal spacings of multiple individual layers within the quasi-crystals were monitored as the chemical composition of the surrounding solution was manipulated, allowing the heterogeneity of swelling within each particle to be assessed. Acquisition of a series of images in continuous capture mode allows the rate of swelling change to be calculated.