Atomic force microscopy (AFM) was used to image swelling clay (smectite) quasi-crystals in situupon initial exposure to liquid water or during the course of cation exchange. Unlike conventional x-ray diffraction studies of swelling, AFM allows the changes in individual layers to be directly measured in three dimensions as the aqueous composition is modified. Topographical images of the particles at different times throughout the swelling process reveal details of the swelling dynamics at the nanoscale. Image analysis in this study involved restricting the z values on an AFM image to isolate a plane of a quasi-crystal, which can be compared to subsequent images of the same particle plane later in the swelling process. The difference in area of these two planes revealed how swelling varies spatially across the quasi-crystal and to what extent. Similarly, the data from three dimensional representations of AFM images were manipulated to show overall swelling behavior. The analysis of AFM images in this study has shown an uneven swelling pattern across quasi-crystals. This can be described as a tilting of particle layers as water molecules are preferentially incorporated into the clay structure from one side of the quasi-crystal. The observation of non-uniform swelling suggests that natural variation in charge density across clay layers influences the swelling process.

Atomic force microscopy studies of smectite swelling

248th National Meeting (2014)

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