Formation of iron oxide nanocrystals by reactions of iron with supercritical fluids H2O and H2O/CO2

Abstract

Wide application of water supercritical fluid (SCF) as an operating fluid in thermal and nuclear power plants,1,2 involvement of natural resources of supercritical H2O and H2O/CO2 into power production, 3 as well as the develop ment of the plants with reactors based on supercritical water to dispose toxic wastes4,5 and convert low grade fuels6,7 have generated the interest to research on corro sion of structural materials in supercritical media.8 Nano particles of iron oxide are also extensively used in medi cine, bioengineering, in manufacturing of magnetic mem ory devices, and in catalysis.9 Various methods9,10 includ ing hydrothermal techniques11,12 are applied to synthesize iron oxide nanoparticles. In this work, the oxidation of iron (Fe) particles in supercritical H2O and H2O/CO2 at different temperatures T is described (Table 1). The initial pressure of SCF in the reactor P0 (see Table 1) containing iron particles was gen erated by injecting SCF from a mixer with the volume approximately 20 times larger that of the reactor. The reactor with Fe particles was preliminary evacuated and heated up to operating temperature. The Fe particles were evenly placed at the bottom of a flat cell located along the axis of