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Enhancement of MgAl2O4 spinel formation from coprecipitated precursor by powder processing
, A.K. Bandyopadhyay, S. Mukherjee, B.N. Samaddar, P.G. Pal
Published in Indian Academy of Sciences
2011
Volume: 34
   
Issue: 4
Pages: 865 - 872
Abstract
Although low temperature fast coprecipitation technique has been used to synthesize stoichiometric (MgO-nAl2O3, n = 1) MgAl2O4 spinel forming precursor, delayed spinellization has always been the concern in this process. In this article, the precursor of this 'fast technique' has been used for bulk production by further processing by high speed mixing with solvents and mechanical activation by attrition milling in terms of superior spinellization. At 1000°C, MgAl2O4 -γ-Al 2O3 solid solution and MgO phases are formed (spinel formed by 1000°C is regarded as primary spinel). At higher temperatures, due to large agglomerate size, MgO can not properly interact with the exsolved α-Al2O3 from spinel solid solution to form secondary spinel; and consequently spinellization gets affected. Solvent treatment and attrition milling of the coprecipitated precursor disintegrate the larger agglomerates into smaller size (effect is more in attrition). Then MgO comes in proper contact with exsolved alumina, and therefore total spinel formation (primary + secondary) is enhanced. Extent of spinellization, for processed calcined samples where some alumina exists as solid solution with spinel, can be determined from the percentage conversion of MgO. Analysis of the processed powders suggests that the 4 h attrited precursor is most effective in terms of nano size (< 25 nm) stoichiometric spinel crystallite formation at ≤ 1100°C. © Indian Academy of Sciences.
About the journal
JournalBulletin of Materials Science
PublisherIndian Academy of Sciences
ISSN02504707