The interpretation of rheograms of magnetic lacquers measured with a couette apparatus

Author

Kuin, Paul N.

Author_Institution

Philips Research Labs., Eindhoven, The Netherlands

Volume

23

Issue

1

fYear

1987

fDate

1/1/1987 12:00:00 AM

Firstpage

97

Lastpage

99

Abstract

Magnetic lacquers show pseudo plastic behaviour with a yieid value. Magnetic lacquers are always flocculated suspensions due to the large magnetic attraction forces between the particles. Flocs are also seen on TEM or SEM micrographs. We postulate viscoelastic deformation of the floes with stress relaxation, described by: $\\tau (D) = \\tau _{F}(1-\\exp(-tD))$ . If this holds, the measured rheograms could be described with $\\tau (D) = \\tau _{y} + \\eta_{N}D + \\tau _{F} (1-\\exp(-tD))$ , where $\\tau _{y}, \\tau _{F}, \\eta_{N}$ and t are parameters to be fitted. The fit of this formula on the measured rheograms is very good indeed. Results of the interpretation of the rheograms as a function of the dispersion time are discussed. The viscoelastic behaviour of flocs was demonstrated elsewhefe by observing the flocs through a microscope in an alternating magnetic field.

Keywords

Coatings; Magnetic materials/devices; Magnetic tape recording; Plastic materials/devices; Elasticity; Lacquers; Magnetic field measurement; Magnetic force microscopy; Plastics; Scanning electron microscopy; Stress; Suspensions; Transmission electron microscopy; Viscosity;

fLanguage

English

Journal_Title

Magnetics, IEEE Transactions on

Publisher

ieee

ISSN

0018-9464

Type

jour

DOI

10.1109/TMAG.1987.1064758

Filename

1064758