The Flow Property of Powder in Vibrating State

Abstract

The viscosity of powder was measured with the rotational viscometer in a vibrating state. In this experiment, the outer cylinder of Stomer viscometer was tightly connected to the vibrator which had constant frequency (120cps), and the amplitude was varied by changing the voltage applied to the vibrator. The α-alumina powders with several kinds of particle sizes were used as samples.
The flow curves, obtained of powders of various particle sizes under different amplitudes and temperatures, were found to be similar to one of non-Newtonian liquids. When the amplitude decreased, each powder behaved like a continuous solid.
The apparent viscosity was obtained from these flow curves in relation to the different amplitudes and particle sizes. At a constant rate of shear and large amplitude, the apparent viscosity decreased with decrease in particle size. When the amplitude was sufficiently small, the apparent viscosity reached its minimum at a definite particle size. It was considered that in the fine powders their coagulated secondary particles moved as flowing units, and that these coagulated particles were broken into primary particles with increase of amplitude.