Shear Thickening and Gel Elasticity in a Colloidal System with Attractive Interactions

Dilute oil dispersions of carbon black particles with attractive Van der Waals interactions display shear thickening in two distinct regimes. The first occurs at low shear rates, γ̇c1 ≈ 100s−1 along with the formation of vorticity aligned shear-induced structures. The second high shear regime with γ̇c2 ≈ 102−3s−1 is driven by hydrodynamic breakup of clusters. Pre-shearing in the high rate shear thickening regime produces enhanced-modulus gels where G′ ∼ σ1.5−2 pre−shear and is directly proportional to the residual stress in the gel measured at a fixed sample age. The observed data can be accounted for using a simple scaling model for the breakup of fractal clusters under shear stress.