Forces Between Slurry Particles Due To Surface Tension

Abstract

Equations are derived defining the shape of small bubbles or drops which may form between pairs of slurry particles, immersed in a liquid vehicle; the system considered is axially symmetric. The resultant bubble or drop shapes are also presented graphically.

The force which a bubble or drop may transmit between particles is derived and evaluated for some particular cases of interest.

In a system with only two components, any bubble must contain the vapour phase of the liquid vehicle, at reduced pressure. Such a bubble can only exist if the contact angle, measured in the liquid phase, exceeds 90° and it will always exert a cohesive force, holding the slurry particles in contact.

Three component systems can be formed with bubbles or immiscible liquid drops joining adjacent slurry particles, provided that the contact angle is greater than zero, and they may transmit a cohesive force. This was demonstrated qualitatively by experiments with glass particles in water which flocculated heavily when shaken in air and dispersed when de-aerated, or when the contact angle was reduced to zero.

When a liquid metal slurry is exposed to neutron irradiation, gas may be generated, and may cause flocculation by this mechanism. Degassing may prove to be difficult.