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      https://www.ias.ac.in/article/fulltext/boms/034/04/0865-0872

    • Keywords

       

      MgAl2O4 spinel; coprecipitation technique; mixing; milling; phase transformation.

    • 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-Al2O3 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.

    • Author Affiliations

       

      Soumen Pal1 A K Bandyopadhyay1 S Mukherjee2 B N Samaddar3 P G Pal1

      1. Department of Ceramic Technology, Government College of Engineering and Ceramic Technology, Kolkata 700 010, India
      2. School of Materials Science and Nanotechnology, Department of Metallurgical and Material Engineering, Jadavpur University, Kolkata 700 032, India
      3. Ex-emeritus Professor (AICTE), Department of Metallurgical and Material Engineering, Jadavpur University, Kolkata 700 032, India
    • Dates

       
  • Bulletin of Materials Science | News

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