Measuring Material Microstructure under Flow Using 1-2 Plane flow-Small Angle Neutron Scattering

Published

February 6, 2014

Author(s)

Dave Binkley, P. Douglas Godfrin, Norman J. Wagner, Aaron P. R. Eberle, Paul Butler, Lionel Porcar

Abstract

A new small-angle neutron scattering (SANS) sample environment optimized for studying the microstructure of complex fluids under simple shear flow is presented. The SANS shear cell consists of a concentric cylinder Couette geometry that is sealed and rotating about a horizontal axis so that the vorticity direction of the flow field is aligned with the neutron beam enabling scattering from the 1-2 plane of shear (velocity-velocity gradient, respectively). This approach is an advance over previous shear cell sample environments as there is a strong coupling between the bulk rheology and microstructural features in the 1-2 plane of shear. Flow-instabilities, such as shear banding, can also be studied by spatially resolved measurements. This is accomplished in this sample environment by using a narrow aperture for the neutron beam and scanning along the velocity gradient direction. Time resolved experiments, such as flow start-ups and large amplitude oscillatory shear flow are also possible by synchronization of the shear motion and time-resolved detection of scattered neutrons. Representative results using the methods outlined here demonstrate the useful nature of spatial resolution for measuring the microstructure of a wormlike micelle solution that exhibits shear banding, a phenomenon that can only be investigated by resolving the structure along the velocity-gradient direction. Finally, potential improvements to the current design are discussed along with suggestions for supplementary experiments as motivation for future experiments on a broad range of complex fluids in variety of shear motions.

Citation

Journal of Visualized Experiments

Volume

0

Issue

84

Pub Type

Journals

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Keywords

Rheology, Shear Banding, Nanostructure, Neutron Scattering, Complex Fluids, Flow-induced structure

Citation

Binkley, D. , Godfrin, P. , Wagner, N. , Eberle, A. , Butler, P. and Porcar, L. (2014), Measuring Material Microstructure under Flow Using 1-2 Plane flow-Small Angle Neutron Scattering, Journal of Visualized Experiments, [online], https://tsapps.nist.gov/publication/get_pdf.cfm?pub_id=914122 (Accessed May 20, 2024)