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597d

Van Der Waals Adhesive Forces in Particle Mixing and Segregation

Isabel Figueroa, University of Pittsburgh, 1249 Benedum Hall, University of Pittsburgh, Pittsburgh, PA 15261 and Joseph J. McCarthy, Chemical Engineering, University of Pittsburgh, 1249 Benedum Hall, University of Pittsburgh, Pittsburgh, PA 15261.

Processing of fine powders is a relevant operation in many industries, from pharmaceuticals to material synthesis. As the size of the particles decreases, van der Waals forces start to play an important role in the behavior of the granular material and can dramatically impact the degree of mixing. In this work, we study the mixing and segregation behavior of fine particle systems using models capable of solving both normal and tangential interactions of elastic-plastic particles in the presence of van der Waals forces.

We use scaling arguments to analytically predict the asymptotic state of the system by comparing the relative magnitude of the adhesive force with the other relevant forces. These predictions are most easily summarized by phase-space diagrams which exhibit both mixed and segregated regions. We compare the result of our simulations for different particle systems with our predictions.