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Abstract
The effect of α-Al2O3 seeds and MgO on the densification behavior and microstructure of the nanocrystalline γ-Al2O3 powder was investigated. The required α-Al2O3 seeds were produced by ‘autogenous seeding’ where the seeds were obtained by calcination of the initial nanosized γ-Al2O3 powders above its transformation temperature and incorporated into γ-Al2O3 matrix. The seeds were characterized by means of laser particle size analyzer, X-ray diffraction, and Brunauer–Emmett–Teller surface analyzer. The simultaneous influence of α-Al2O3 seeds and MgO on γ-Al2O3 behavior was evaluated by differential thermal analysis, densitometry, and electron microscopy. The results showed that simultaneous presence of MgO and seeds in γ-Al2O3 matrix has a great impact on densification and microstructural evolution. The main role of MgO and the seeds are densification enhancement and grain refinement, respectively. The grain morphology is more equiaxed and desirably finer by using smaller seeds prepared using shorter calcination times.