粉体の動的構造と流動性

抄録

The powder bed in a vibrating state of various graphite of different particle sizes have been experimentally studied with respect to their relation between their fluidity and structure. The structure of powder bed in a vibrating state has been discussed on the bases of variation of electric resistance of powder bed with the vibration intensity, since the electric resistance is related to the packing structure of particles in the bed. The fluidity measurements were made with a rotary type viscometer. A slight increase of electric resistance of the powder bed has occurred with increase in amplitude of vibration. Further increase in vibration results in rapid increase of electric resistance. During this stage, the slopes of amplitude-electric resistance plot increases in proportion to the particle size of the powder.
As amplitude of vibration increases further, the net drag force exceeds the gravitational force on the particles, and the increase of electric resistance is slow. The change in fluidity with vibration shows the same tendency to the amplitude-electric resistance plots. These relations between the amplitude and electric resistance or fluidity of powder bed are similar to the change found in the relation of temperature vs. specific volume in glass transition of various materials. In the region where the vibration force exceeds the gravitational force acting on particles, the relation between the change of electric resistance due to the vibration and the fluidity of powder bed can be expressed in the following equation:
φ=aexp(-bR_o/R_x)
where φ stands for fluidity, R_o and R_x for the electric resistance of powder bed in fixed-bed and in vibrating state, and a, b as constant and b is related to the particle sizes of the powder.
These results will point to the fact that the varying process in the moving structure of powder bed, which is due to the vibration, consists of two different packing structures based on the motion of the particles.