Synthesis of Fe$_x$O$_y$ nanoparticles during iron oxidation by supercritical water

It is established that iron is oxidized by supercritical water (SCW) with the formation of H$_2$ and nanoparticles of iron oxides (Fe$_3$O$_4$, FeO, and $\gamma$-Fe$_2$O$_3$). The kinetics of H$_2$ production and iron oxidation has been studied by SCW injection at $T$ = 673, 723, 773, 823, and 873 K into a reactor with iron particles. Data of X-ray diffraction and transmission electron microscopy show that the phase composition and morphology of synthesized oxide nanoparticles depend on the SCW temperature.