Assessment of Shear-Induced Structures by Real Space and Fourier Microscopy
We report preliminary measurements of the shear-induced sliding layer structure in an aqueous suspension of highly charged polystyrene spheres. Particle interaction was controlled by advanced conditioning procedures to result in fluid or body-centred cubic equilibrium structures. Shear was applied in an optical plate-plate shear cell of variable slit width. Fourier microscopy yielded complementary information to real space analysis. The accessible range of scattering vectors was (3.5 ≤ k ≤ 7.2) μm−1 We checked the experimental performance by recording the form factor of a non-interacting suspension and structure factors of less dilute suspensions in dependence on electrolyte concentration c. For deionized suspensions of particle number densities of n = 0.34 µm−3 we observed crystallisation. Shearing this sample we obtained two-dimensional structure factors which are compatible with sliding layer formation. The observed quantitative discrepancies to the theoretical model calculations are discussed.
Key wordsColloidal suspensions Shear-induced structure Microscopy Light scattering
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