On the behaviour of the rheological and magnetic parameters of densified γ-Fe2O3

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Abstract
Magnetic characteristics (coercivity, remanent coercivity, remanence/saturation ratio, coercivity factor) and rheological properties (tap density, apparent density and wettability) for a number of &-Fe2O3samples are analyzed. The samples are the following: I. &-Fe2O3produced from densified &-FeOOH at various densification times; II. Densified &-Fe2O3withdrawn from the densifier at different densification times; III. Densified and non-densified materials available on the market. The magnetic data as a function of the densification degree (i.e. vs. apparent density) confirm the increase of interactions and the re-assembling of the loose particles in a distribution of single particles, sheaf and ring shaped clusters. The wettability of the I samples is largely different from that of II samples; an hypothesis is made: densification produces a rough cleaning of the particles surface thus bringing out the reactive sites of the surface that can therefore be easily wetted out. Samples III confirm this hypothesis.