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Grinding Assistance in the Transformation of Gibbsite to Corundum

Published online by Cambridge University Press:  31 January 2011

Rosa M. Torres Sánchez
Affiliation:
Centro de Tecnología en Recursos Minerales y Cerámica (CETMIC), Camino Centenario y 506, C.C. 49, 1897 Gonnet, Argentina
A. Boix
Affiliation:
Instituto de Calalisis y Petroquimica -Universidad Nacional del Litoral, Santiago del Estero 2829, 3000 Santa Fe, Argentina
R. C. Mercader
Affiliation:
Departamento de Física, IFLP, Facultad de Ciencias Exactas, Universidad Nacional de La Plata, Argentina
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Abstract

After gibbsite was milled for 5 min in a Cr-steel oscillating mill, corundum was obtained by heating the powder for 3 h at 800 °C. We found that iron contamination, produced by the milling process, is essential to attain the transformation at this low temperature and is located at the surface of the gibbsite particles. The knowledge of the oxidation state and location of the contaminant elements, necessary to control the solid-state reactions and/or phase transformations induced by the milling, was realized in this work by a characterization performed by chemical analysis, x-ray photoelectron spectroscopy, Mössbauer spectroscopy, and isoelectric point determination. The iron contamination amounted to about 3% (as Fe2O3) for the sample milled for 60 min. That the iron contamination that occurred mainly on the gibbsite amorphous surface was concluded after a comparison of the isoelectric point determination of the milled samples with that of a mechanical mixture of gibbsite and hematite. X-ray diffraction studies showed that gibbsite looses its crystallinity after the first 5 min of milling.

Type
Articles
Copyright
Copyright © Materials Research Society 2002

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