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Jan Peter Embs, H. W. Müller, C. E. Krill, F. Meyer, Harald Natter, B. Müller, S. Wiegand, Manfred Lücke, K. Knorr, Rolf Hempelmann
Characterization of the Grain Size in Ferromagnetic Colloids: Comparing Torsional-Pendulum Measurements with Standard Complementary Methods
Keywords: Ferrofluids, Particle Size Analysis, Relaxation Time
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.
Zeitschrift für Physikalische Chemie, Oldenbourg Wissenschaftsverlag
Print ISSN: 0942-9352
Volume: 220, 02/2006
Pages: 153 - 171