Regensburg 2004 – wissenschaftliches Programm
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DY: Dynamik und Statistische Physik
DY 11: Ferrofluids
DY 11.1: Vortrag
Montag, 8. März 2004, 10:30–10:45, H3
Investigation of the microstructure of ferrofluids using small angle neutron scattering (SANS) — •Loredana Pop1, Stefan Odenbach1 und Albrecht Wiedenmann2 — 1ZARM, University of Bremen, Am Fallturm 28359 Bremen — 2Hahn-Meitner-Institut Berlin, Glienicker Str. 100, 14109 Berlin
Experimetal studies made for different ferrofluid samples under shear flow have shown that increasing the magnetic field strength yields an increase of the fluids viscosity, the so called magnetoviscous effect, while increasing shear rate leads to a decrease of the magnitude of the viscosity (shear thinning). The change of the viscosity with magnetic field strength is theoretically explained as an effect of chain-like structure formation in ferrofluids whereas its magnitude depends on the particle-particle interaction. Both effects, the shear thinning and the magnetoviscous effect, can therefore be related to the microstructure and microstructure dynamics of ferrofluids. Using a specially designed rheometer, ferrofluids having different magnitude of the magnetoviscous effect were investigated by SANS. Correlated to the structure formation in the fluid, the scattered intensity shows a variation with the magnetic field and shear rate only in the case of the fluids with a high magnetoviscous effect. The results which will be presented show that there is a strong connection between the rheological behaviour of ferrofluids and their microstructure.