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Licensed Unlicensed Requires Authentication Published by De Gruyter (O) September 25, 2009

Characterization of the Grain Size in Ferromagnetic Colloids: Comparing Torsional-Pendulum Measurements with Standard Complementary Methods

J. Embs , H. W. Müller , C. E. Krill , F. Meyer , H. Natter , B. Müller , S. Wiegand , M. Lücke , K. Knorr and Rolf Hempelmann

Summary

A recently introduced shear-flow-free method for measuring the rotational viscosity of a resonantly forced torsional pendulum is used to determine the transverse magnetic relaxation time in magnetite and cobalt-based ferrofluids. From these data the average size of the ferromagnetic grains and their hydrodynamic diameter (core plus surfactant coating) are deduced under in-situ conditions, i.e. without diluting the sample. The reliability of the method is demonstrated by comparing the results with those of the complementary techniques of magneto-granulometry, X-ray diffraction, electron microscopy, and photon-correlation spectroscopy.

Received: 2005-9-27
Accepted: 2005-11-16
Published Online: 2009-9-25
Published in Print: 2006-2-1

© by Oldenbourg Wissenschaftsverlag, München

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