Abstract

Nanoparticles of iron oxides have been prepared by the levitational gas condensation (LGC) method, and their structural and magnetic properties were studied by XRD, TEM and Mossbauer spectroscopy. Fe clusters were evaporated from a surface of the levitated liquid Fe droplet and then condensed into nanoparticles of iron oxide with particle size of 14 to 30 nm in a chamber filled with mixtures of Ar and O_2 gases. It was found that the phase transition from both gamma-Fe_2O_3 and alpha-Fe to Fe_3O_4, which was evaluated from the results of Mossbauer spectra, strongly depended on the O_2 flow rate. As a result, gamma-Fe_2O_3 was synthesized under the O_2 flow rate of 0.1≤Vo_2(Vmin)≤0.15, whereas Fe_3O_4 was synthesized under the O_2, flow rate of 0.15≤Vo_2(Vmin)≤0.2.

• Keywords: Levitational gas condensation;Nano iron oxide;Mossbauer spectrum;