Synthesis Of Fe-Group Metal Oxide Nanostructures By Thermal Oxidation And Their Magnetic Properties

In this paper, we review the preparation of Fe-group metal oxide nanostructures by the thermal oxidation method developed in our lab. By this method, we have prepared several kinds of nanostructures, including nanowires and nanoleaves. The magnetic properties of these nanostructures have also been studied. By carefully controlling the reacting time, temperature, and humidity, we have prepared alpha-Fe2O3, gamma-Fe2O3, Fe3O4, and Co3O4 nanowires and alpha-Fe2O3 nanoleaves by heating the substrates in proper atmosphere. The alpha-Fe2O3 and Co3O4 nanowires are produced by directly oxygenating pure metal at 550 similar to 650 degrees C and 480 similar to 520 degrees C, separately. The gamma-Fe2O3 and Fe3O4 nanowires are produced by reducing as-prepared alpha-Fe2O3 nanowires in a mixture of N-2 and H-2. The nanowires are about 10 similar to 20 mu m, with diameter of about 20 similar to 100 nm. Most of the nanowire arrays are grown vertically from the surface of the substrate at a high surface density (10(8)similar to 10(9) cm(-2)). Compared with the nanowires prepared by hydrothermal process and template method, Most of our nanowires are structurally uniform and single crystallites. The magnetic properties of these nanostructures are also studied, and demonstrate some novel properties.