Anisotropic character of talc surfaces as revealed by streaming potential measurements, atomic force microscopy, molecular dynamics simulations and contact angle measurements

A study of the interfacial properties of the basal plane and the edge surfaces of talc is described in this paper. The isoelectric points measured at two different crystallographic surfaces by the streaming potential method were found to be similar and exist at about pH 3.0. In the case of the edge surface, the zeta potential increases at higher pH values which can be attributed to the hydration of surface magnesium ions. The forces between the edge of a 20 mu m talc particle and the two different crystallographic surfaces of talc were measured at various pH values using atomic force microscopy (AFM). These measurements show differences between the properties of the basal plane and edge of the talc. Finally, the differences in the hydration of the basal plane and the edge of talc are revealed from molecular dynamics (MD) simulations. The basal plane of talc is much less hydrated than the edge as can be seen from the water density distribution functions which correlate quite well with the contact angle measurements at the basal plane surface and the edge surface. Improved quality of the edge surface was achieved by sandblasting (erosion with alumina) and research regarding the characteristics of this edge surface is in progress.