Kerry Johanson

Measurement of oil-mediated particle adhesion to a silica substrate by atomic force microscopy

Preventing particle segregation while maintaining flow is critical to enable processing in a variety of industries. Where segregation or dusting is particularly troublesome, oil may be added to the powder to increase cohesion between particles or to attach flow-aids to the particle surface. In this investigation, the role of the capillary force produced by an oil annulus between surfaces and its influence on adhesion are explored. The results of direct measurement by atomic force microscopy are compared with ensemble powder properties, as well as a simple theoretical expression that predicts the magnitude of the adhesion force as a function of the separation distance. Agreement is achieved between theory and experimental data using only the volume of the oil annulus and its surface tension as variables.

Role of Capillary Forces in the Reduction of Dust Pollution During Transport and Handling of Powders

Mixing of dry powders with oil or liquid binder is often done to minimize segregation and dust pollution during handling and transport. The amount of binder required is determined empirically due to inadequate models. Oil as a binder forms capillary bridges between particles. In the present study, theoretical expressions are developed for the calculation of the capillary force at different oil interlayer thickness between particles. Experimental measurements using AFM were conducted to validate the theory for particle/particle and particle/wall interactions.