Synthesis and characterization of pure nanocrystalline magnesium aluminate spinel powder

Synthesis of nanocrystalline magnesium aluminate spinel (MgAl2O4) by mechanical activation of a powder mixture containing Al2O3 and MgCO3 with subsequent annealing was investigated. Simultaneous thermal analysis (STA), X-ray diffraction (XRD), and scanning electron microscopy (SEM) techniques were utilized to characterize the as-milled and annealed samples. Results showed that pure nanocrystalline spinel could be fabricated completely by 5 h of mechanical activation with subsequent annealing at 1200 °C for 1 h with a crystallite size of about 45 nm. Further milling had no significant effects on structure or phase composition of spinel phase after subsequent annealing. The nanocrystalline spinel powder obtained after 60 h of milling and subsequent annealing at 1200 °C for 1 h had a crystallite size of about 25 nm according to Williamson–Hall approach and particle sizes smaller than 200 nm. Enhanced mechanical properties were observed in samples prepared from the powder mixture and milled for a longer period.