Preparation and characterization of metal/ceramic nanoporous nanocomposite powders

The Fe/MgO nanocomposite powders, which could be available for magnetic and the catalytic applications, were fabricated by spray pyrolysis using an ultrasonic atomizer. The liquid source was prepared from Fe and Mg nitrates with a pure water solvent. The mist of the liquid source was generated by an ultrasonic atomizer and carried into a preheated chamber (500-800 °C) by air carrier gas. Then the mist was decomposed into γ-Fe₂O ₃ and MgO nanopowders. The entire processes were performed at 1 atm. At this time, the obtained oxide powders are reduced by a hydrogen atmosphere (flow rate: 1 l/min) at different temperatures. After a reduction reaction, the primary particles, such as Fe, MgO, which were about ∼20 nm in diameter and the spherical porous secondary particles of submicron size were formed with pores of less than 10nm. The particle sizes of Fe/MgO samples were increased by increasing the chamber and reduction temperatures. The Fe/MgO nanocomposite powders, which were prepared and reduced at 600 °C, exhibited ferromagnetic properties. The coercive force (H_c) of this sample was determined to be 680 Oe, which is much higher than that of pure iron.