The Structure and Heat of Immersion of Ultra-fine Ferric Oxides

Abstract

The ultra-fine ferric oxides of 50 to 650 Å in diameter were examined by X-ray diffraction, differential thermal analysis, electron microscope and H₂O adsorption in order to find the cor- relation of the ultimate and agglomerated structures of the ferric oxides with the heat of im- mersion in water, ΔH_I.
It was shown that ΔH_I is almost independent of the particle size, except B-500-1 and B500-2, samples which showed higher ΔH_I values (Fig.2). These two samples were prepared by heating amorphous hydrous oxide at 500° C, and showed partial crystallization to α-Fe₂O₃ and considerable sintering. Higher ΔH_I values of the sintered samples were interpreted by the' presence of interparticle micropores, through which H₂O molecules are more easily permeable than N2 molecules. The surface activity incident to the structural change is also thought to be pertinent to the higher ΔH_I.