Iron oxide synthesis using a continuous hydrothermal and solvothermal system

Iron oxide synthesis via a continuous hydrothermal and solvothermal reaction were studied. In the hydrothermal synthesis, fine α-Fe2O3 (hematite) particles were obtained at 250–420 °C and 30 MPa. The α-Fe2O3 crystals were grown in sub-critical water via a dissolution and precipitation process. The growth of α-Fe2O3 crystals in supercritical water was suppressed due to the rather low solvent power of water. Crystalline Fe3O4 was obtained as the temperature was raised above the supercritical state in the solvothermal preparation. Isopropanol (IPA) was oxidized in acetone which provided a reducing atmosphere. Acetone molecule adsorption onto the Fe3O4 particle surface inhibited crystallite growth.