Pressure-driven flows of concentrated alumina suspensions depending on dispersion states of particles

Abstract

The flow developments of 25 vol% alumina suspensions in slit channel were visualized and analyzed depending on the dispersion states. For the coagulated alumina suspension, the shear stress showed an N curve that included a region of stress decrease with an increase in shear rate followed by a monotonic increase. Depending on the region in the stress curve, the flow profile changed from a shear-banded profile to a plug-like flow profile similar to the Newtonian fluid. In addition, it was observed that the transient flow behavior over time at high shear rate in liquid state experienced all of the steady state flow profiles at lower shear rates in solid-liquid transition. During the solid-liquid transition, the flow profile was found to be shear banded, and the pressure profile did not reach a steady state but fluctuated with a characteristic time period. In contrast, the well-dispersed suspension showed only a monotonic increase of shear stress in the range of shear rates we could measure, indicating that the suspension was in liquid state. The flow profile was plug-like, and the pressure was fluctuating without any characteristic time period.