DBPapers
DOI: 10.5593/sgem2012/s04.v2010

STUDY OF MAGNESIA -SPINEL BASED COMPOSITIONS DERIVED FROM DIFFERENT RATIOS OF PURE MAGNESIA/ALUMINA AND ADDITIVES

P. LAMPROPOULOU, C.KATAGAS, D.PAPOULIS
Wednesday 1 August 2012 by Libadmin2012

References: 12th International Multidisciplinary Scientific GeoConference, www.sgem.org, SGEM2012 Conference Proceedings/ ISSN 1314-2704, June 17-23, 2012, Vol. 2, 425 - 432 pp

ABSTRACT

Eighteen new synthesized magnesium aluminate spinel based refractory compositions
containing alumina ranging from 50% to 70% and additives of either ZrSiO4 (0.5-2%)
or chromite (2-5%), were prepared using a two stage sintering process at 1760oC.
In this study we investigate the effects of different starting Alumina (A) / Pure
Magnesia (M) wt% ratios and additives content on the mineralogical phases formed and
their chemical composition, as well as on the lattice parameters of the spinel crystals,
microstructures and densification of the spinel based compositions. ICP- chemical
analyses of bulk samples, optical microscopy, powder XRD analysis, and SEM
imaging of polished samples combined with qualitative EDS and quantitative WDS
analysis have been used to obtain the characterization of the materials.
The results show that with increasing A /M ratio the bulk density, the spinel content
and its crystal size as well as the spinel-spinel direct bonding are increased, while the
periclase content and its crystal size are reduced. On increasing ZrSiO4 content the bulk
density of samples with 1/1 and 6/4 A /M wt% ratios increases, while in chromitebearing
samples a similar trend has been also noticed for compositions with 50 and 60
wt% alumina content.
In compositions with zirconium silicate, the spinel crystal density and its lattice
parameter range to lower values than those of spinels formed in the chromite added
compositions while a positive relation between the additive content and spinel crystal
density has been observed only in samples with chromite and 7/3 A/M ratio. The study
revealed also that the samples with 5% chromite, host spinels with the higher lattice
parameter values.

Keywords: spinel compositions, density, crystal parameter, microstructure, phases

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