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RHEOMETER

In this example, the detector was combined with a unique rheometer setup using a vertical X-ray beam geometry [1]. A rheometer drives complex fluid materials to states far from equilibrium and measures the viscoelastic properties of the sample. In our case we applied steady shear to colloidal particles in suspension at PETRA-III, P10. According to the requirements of the vertical beam geometry, the LAMBDA detector was mounted vertically above the rheometer to measure scattering patterns. Figure 4 below shows typical scattering patterns when the shear rate is increased. We obtained information about both a change in particle spacing (wider spacing along the direction of flow) and increased disorder in the sample. The LAMBDA detector provided sufficient spatial and temporal resolution to measure fast dynamical changes of complex fluid materials under controlled shear conditions. Figure 4. Logarithm of the small-angle scattering signal from colloidal silica spheres, measured with LAMDBA at PETRA-III P10. The images show the signal at low and high shear rates; at high shear rates, the spacing between spheres increases in the direction of flow (left to right) and the ordering is decreased.
[1] B. Struth, K. Hyun, E. Kats, T. Meins, M. Walther, M. Wilhelm and G. Grübel, “Observation of new states of liquid crystal 8CB under nonlinear shear conditions as observed via a novel and unique rheology/Small- Angle X-ray Scattering combination”, Langmuir 27 (6), 2880-2887, 2011.
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