The Effects of Magnetic Property on the Dispersion of Iron Oxide Powders in Solvents

Abstract

In this paper the author reports the effects of magnetic property on the dispersion of iron oxide powders in solvents. Acricular γ·Fe₂O₃ and α·Fe₂O₃ powders have been chosen for specimens. The dispersibility and its time variation have been measured by the size distribution of flocculated particles for various method of dispersion in solvents which are mostly hydrophobic type.
The results of measurement show that α·Fe₂O₃ has far better dispersibility compared to that of γ· Fe₂O₃. The least effective diameters measured as median of the size distribution below 20μ which correspond to the best dispersion are 3.0μ and less than 0.7μ for γ·Fe₂O₃ and α·Fe₂O₃ respectively.
It is found that the dispersibility of γ·Fe₂O₃ in the solvents is inversely related to the magnetic property, especially to the residual magnetization of the specimen. The unit particles of γ·Fe₂O₃ are considered to be composed of still smaller particles and to behave as a single domain magnet. The residual magnetization gives a measure of the magnetic attraction which sets the limitation and order of dispersibility.