The importance of explicitly considering interparticle interactions in the rheology of dense sus- pensions and particle slurries is well established, although the exact relationships between particle- level quantities and macroscopic rheology and stability are at best qualitative. Most of the un- derstanding has been developed for low shear rheological (linear viscoelastic) properties and/or for dilute dispersions. This project has the goal of providing experimental evidence for the influ- ence of interparticle surface forces and hydrodynamic forces (due to the presence of the solvent) on the moderate to high shear rheological properties and shear stability of dispersions that span the colloidal to particulate range (colloidal dispersions to slurries). Of particular interest is the shear thickening transition and dilatancy, and how that explicitly depends on the strategy used to stabilize the dispersion or slurry (i.e. steric, electrostatic, polymeric stabilization), as well as the hydrodynamic forces important at higher shear rates.
The research to date has the following components:
-Systematically explore the influence of the basic methods of particle stabilization on the shear thickening and dilatancy of well-characterized colloidal dispersions and slurries of non- colloidal particles. In this report in particular, particle concentration and the properties of the solvent have been varied to study the influence of hydrodynamic forces on the shear thickening and dilatant behavior.
-Develop the rheological method of stress-controlled parallel superposition rheometry for di- rectly deconvoluting the relative influence of hydrodynamic to interparticle forces in colloidal dispersions and slurries.