Abstract
A magnetorheological sample environment is presented that allows for in situ magnetic field and shear flow during small-angle neutron scattering (SANS) measurements and is now available at the Institut Laue-Langevin (ILL). The setup allows performing simultaneous magnetorheological measurements together with the investigation of structural and magnetic changes on the nanometer length scale underlying the rheological response of ferrofluids. We describe the setup consisting of a commercial rheometer and a custom-made set of Helmholtz coils and show exemplarily data on the field and shear flow alignment of a dispersion of hematite nanospindles in water.Graphical abstractA magnetorheological sample environment is presented that allows for in-situ magnetic field and shear flow during Small-Angle Neutron Scattering (SANS) measurements and is now available at the Institut Laue-Langevin (ILL).
Highlights
Recent progress toward magnetic soft matter combines the unique properties of soft matter and magnetic materials into complex magnetic fluids, such as original or inverse ferrofluids, ferrogels, and ferroelastomers [1,2,3,4,5,6,7,8,9]
A magnetic field of 20 mT is far below a nominal saturation field, and from magnetization measurements, an average orientation of the magnetic easy axis of ψ = 46.3° toward the applied magnetic field is expected according to the Langevin function LðξÞ 1⁄4 hcosψi with the Langevin parameter ξ μμ0 H kBT
Small-angle scattering is a valuable tool for studying flowing systems of dispersed nanoparticles to reveal the collective orientation distribution of particles and the relation between microscopic organization and macroscopic rheological properties
Summary
Recent progress toward magnetic soft matter combines the unique properties of soft matter and magnetic materials into complex magnetic fluids, such as original or inverse ferrofluids, ferrogels, and ferroelastomers [1,2,3,4,5,6,7,8,9]. Ferromagnetic liquid crystals combine nematic order as well as ferromagnetic order and show non-Newtonian behavior in flow field [16,17,18,19]. With the assistance of a magnetic field, the dynamics and the flow properties of the dispersion can be tuned. The fluid-mechanical properties are determined by the particle orientation and the potential creation of clusters, where the interparticle arrangement is governed by the competition of attractive magnetic dipolar and disruptive shear forces. The knowledge of such flowand field-induced microstructural changes is important to understand the origin of the magnetorheological properties, including the magnetoviscous effect and shear-thinning and shear-thickening behaviors
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