The shear‐distorted microstructure of adhesive hard sphere dispersions: A small‐angle neutron scattering study

Abstract

In a small‐angle neutron scattering experiment, we measured the shear‐distorted microstructure of a concentrated model dispersion of adhesive hard spheres in the low shear rate regime (Pe≤1) using a couette shear cell. The nonequilibrium structure factor was probed in the velocity–vorticity plane. By changing the temperature, the interaction potential of the particles was varied from a hard sphere repulsion to a strong attraction. The particle distribution which is isotropic at rest, is anisotropically disturbed by the shear flow. At high temperatures, the dispersion is effectively a hard sphere system. In this case the main distortion of the scattering pattern is in the direction of the fluid flow, the shear flow shifts the first maximum in the structure factor toward smaller scattering angles. In the vorticity direction, no significant distortion of the equilibrium structure is observed. Qualitative agreement is found with theoretical predictions for the shear‐distorted structure factor. With decreasing...