ATOMIC FORCE MICROSCOPY OF ULTRAFINE CLAY PARTICLES

Atomic force microscopy (AFM) was applied to small clay particles of illite/smectite from North Sea Jurassic rock, which is the most important source rock for North Sea oil. The clay is dispersed in water and a drop is then dried on graphite or mica. The images show flat particles with areas from 1000 to 30000 nm2 and sides of equal length. Details of the surface topography of the illite/smectite particles can be imaged and it is possible to resolve both the distance between unit-cells (0.51 nm) and the distance between oxygen atoms (0.3 nm). Systematic thickness measurements show that the particles are 2 to 4 nm thick on average. The measurements also showed that the material contains 1 nm thick single silicate 2:1 layers. Information about the thickness, size and surface structure of mixed layers of illite/smectite can provide new insight into their formation.