MEASUREMENT OF FRICTIONAL FORCE AND VISCOSITY OF HIGH-PURITY MONTMORILLONITE BY AFM

The frictional force and viscosity of high-purity montmorillonite were measured with an Atomic Force Microscope (AFM). The results confirmed that both the coefficient of friction (μ) for Na-montmorillonite and that for Ca-montmorillonite exhibit a graded decrease with an increase in relative humidity (RH). The results also showed that, in terms of its relationship with temperature, the coefficient of friction (μ) for Na-montmorillonite increases with an increase in temperature when the RH is 30% or higher but remains constant regardless of temperature when the RH is 20% or lower. The coefficient of friction (μ) for Ca-montmorillonite, on the other hand, increases with an increase in temperature regardless of the RH. It was confirmed that the viscosity of both Na-montmorillonite and Ca-montmorillonite has a graded increase with an increase in the RH. The viscosity of Na-montmorillonite remains constant regardless of temperature when the RH is 20% or lower, but decreases with an increase in temperature when the RH is 30% or higher. The viscosity of Ca-montmorillonite, however, diminishes as the temperature increases regardless of the RH. And finally, a comparison of frictional forces in the macro and micro regions showed that the coefficient of friction (μ) in the macro region calculated from the direct box shear test does not match the coefficient of friction (μ) in the micro region measured by using an AFM