Shear induced periodic structure changes in concentrated alumina suspensions at constant shear rate monitored by FBRM

Concentrated aqueous suspensions of alumina as disperse phase show a particular non-Newtonian time dependent flow behavior. The apparent viscosity measured by means of a rotational viscometer with coaxial cylinders at constant shear rate oscillates with time. The period of the oscillations varies on a scale of several hundred seconds. It is assumed that this behavior is caused by shear induced self-organized structure changes. In order to detect structure changes during the shear process a particle analysis system based on the focused beam reflectance measurement (FBRM) technique was applied. We have found a significant correlation between the oscillations of the viscosity and alterations of the chord length distribution.