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The mechanochemical treatment of the α-Fe2O3 (hematite) powder in air and a dispensing liquid (ethanol), using a planetary ball mill was performed. The influence of the atmosphere and the milling time in α-Fe2O3 transformation was investigated. X ray difraction (XRD) arid Mössbauer measurements showed partial transformation from α-Fe2O3 to γ-Fe2O3 (maghemite) for prolonged milling time in air, while only one α-Fe2O3 phase was obtained for the milling using ethanol. Lattice parameters and particles size has been calculated from the XRD patterns for the different times and milling conditions. [ABSTRACT FROM AUTHOR]

Fe-doped TiO2 powders were obtained by mechanical alloying. The starting materials were anatase TiO2 and metallic iron (α-Fe). The influence of different milling conditions such as: ball to powder weight ratio (20:1, 40:1); milling time (6, 12, 18 and 24 hours); rotation velocity of supporting disc (250 and 390 rpm) and dopant concentration ( 1, 4 and 8 at%) on the structural and magnetic properties were investigated.. All experiments were performed at atmospheric conditions. The milled powders were characterized by X-Ray diffraction (XRD) using Rietveld refinement and room temperature Mössbauer spectrometry. Mössbauer spectra reveal the presence of Fe2+ and Fe3+ states as well as α-Fe in samples obtained from metallic iron. The Fe3+ contribution could be attributed to Fe incorporated in the TiO2 structure and the Fe2+ can be assigned to surface ferrous ions in the TiO2[3]. [ABSTRACT FROM AUTHOR]

We have derived the Melchers' mathematical model of the oxygen diffusion across the rust layer formed on the surface of the steels submitted to total immersion, by a most fundamental principle: the Planck-Nersnt law. To achieve it, we have neglected the convection and migration of the oxygen molecules, and we have assumed both that this problem is 1-D and that oxygen consumption, due to chemical reactions, can only occur at the interface between the metallic surface and the rust. Furthermore, we have experimentally determined an α value for Melchers's model, which accounts for the amount of iron coming from the steel which is converted into adherent rust. [ABSTRACT FROM AUTHOR]