EMANATION THERMAL-ANALYSIS STUDIES OF SURFACE-LAYER OF IRON-OXIDE POWDERS PREPARED BY VARIOUS GRINDING TREATMENTS

In order to examine the effects of grinding treatment on the surface layer of powders, the new technique of emanation thermal analysis (ETA), using a method of surface impregnation with the Ra-226 nuclide, was applied in the range 25-1200-degrees-C for characterization of the surface of five iron oxide powders (alpha-Fe2O3) with various preparation histories with regard to grinding treatment. The ETA results were compared with those obtained by the conventional methods: size distribution, BET surface, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The mechanochemical effects of grinding on the surface layer of the sample powders were evident as an increasing peak I and a pronounced peak IIa.