Shear-Induced Structure in Concentrated Dispersions: Small Angle Synchrotron X-ray and Neutron Scattering

Abstract

The influence of shear on the Bragg scattering of concentrated colloidal dispersions made from charged particles is considered in this paper. First, the reciprocal space of a layered sample at rest and under the influence of a disordering torque is considered. Next, the commonly used Couette cell and our disk shear cell are compared in view of the Ewald construction. An introduction of α- and β-rotation axes follows. The first experimental example is concerned with the neutron scattering from a layered colloidal sample at rest. As a second experimental example from the same sample the dependence of synchrotron X-ray scattering on the shear rate is considered. It turns out that the sample does not achieve a microcrystalline state as claimed previously but remains in an orientationally disordered layered state. Finally, the intensity distribution I(l) along the two types of Bragg rods as obtained with remarkable precision by synchrotron X-ray scattering is presented.