Measuring Forces between Oxide Surfaces Using the Atomic Force Microscope

The interactions between colloidal particles play a major role in processing of ceramics, especially in casting processes. With the Atomic Force Microscope (AFM) it is possible to measure the inter-action force between a small oxide particle (a few micron) and a surface as function of surface separation.

Force measurements between a-Al2O3 and TZ3Y surfaces in aqueous solutions has been performed. These data corre-sponds well to the DLVO (Derjaguin, Landau, Vervey and Overbeek) theory for surface-interaction. The derived results are in the form of an apparent surface potential, which show a strong dependency of the pH-value as ex-pected - ranging from + 110 mV at pH 5.6 to - 30 mV at pH 9.5 for a-Al2O3 and + 70 mV at pH 3 to 10 mV at pH 5.6 for TZ3Y.

The numerical highest potential values are obtained for the lowest salt concentrations in solution. The values for the surface potentials can be compared to zeta-potentials measured on powders of the same materials.