Origins of Yielding and Viscoelasticity in Highly Concentrated, Gelled Colloidal Suspensions: An Experimental Study of Microstruture and Rheology

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Abstract9813824M.J. Solomon, U. of MichiganThe microstructural origins of the yield stress and viscoelasticity in highly concentrated colloidal suspensions will be investigated. The interparticle forces give rise to gelation, linear viscoelasticity and yielding. Recent models based on flocculation, percolation and fractals will be experimentally tested using the small and wide-angle light scattering methods of model colloidal suspensions as they undergo yielding transition and shear. Nearly refractive index matched suspensions of metal oxide particles (spheres and rods of variable aspect ratios) in both organic and aqueous solvent will be investigated for volume fractions between 0.02 and 0.2. The project will examine the strain-induced changes in structure of the suspension just prior to yielding. A connection between the microstructural phenomena and macroscopic rheological behavior will be obtained. The proposed work has relevance in processing of colloidal suspensions in the manufacture of ceramics, magnetic storage media and coatings.