Synthesis of Fe:MgAl2O4 nanopowders by laser ablation

The features of production of Fe:MgAl2O4 nanopowders by evaporation of targets made from a simple oxide mixture (Fe2O3, MgO, Al2O3) by repetitively pulsed CO2 laser radiation with I = 1.8 MW/cm2 peak power density and Paver = 600 W average radiation power as well as by ytterbium fiber laser radiation (I = 0.4 MW/cm2 and Paver = 300 W) were studied. It was demonstrated that the nanopowder produced with the use of the CO2 laser has the specific surface of 56 m2/g and contains two crystalline phases, i.e. MgAl2O4 (98.2 wt%) and MgO (1.8 wt%), with Fe ions dissolved in them. At the average radiation power of 600 W, the output of the nanopowder was 16 g/h. For the nanopowder produced using the ytterbium fiber laser, a twofold increase of the specific surface (105 m2/g) was observed. This nanopowder contains four phases, i.e. MgAl2O4 (67.5 wt%), γ-Al2O3 (24.8 wt%), Fe3O4 (3.2 wt%) and MgO (4.5 wt%). In this case, the output of the nanopowder was 2.7 g/h due to high transparency of initial target and the formation of a “forest-like” array of 4–5-mm-high spikes covered with a semitransparent melt layer. Significant differences in the phase compositions of the nanopowders obtained using these lasers are associated with a higher rate of the laser plume cooling for the ytterbium fiber laser.