Grinding assistance in the transformation of gibbsite to corundum

TORRES SANCHEZ, ROSA; BOIX, ALICIA V.; MERCADER, R. C.

JOURNAL OF MATERIALS RESEARCH

Materials Research Soc. Hanover

Lugar: Pennsylvania USA; Año: 2002 vol. 17 p. 101 - 106

0884-2914

After gibbsite was milled for 5 min in a Cr-steel oscillating mill, corundum was obtained by heating the powder for 3 h at 800ºC. 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 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, Mossbauer 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 isoelectric point determination of the milled samples with that of a mechanical mixture of gibbsite and hematite. X-ray diffactio studies showed that gibbsite looses its crystallinity after the first 5 min of milling.