Moderate thermal oxidation of iron oxide found in nature as raw materials for ferrite magnets

Abstract

Iron oxide found in nature with high iron oxide content has potential to be utilized as raw material for magnetic application. In this study, an attempt has been made to increase hematite content through thermal oxidation or roasting in moderate temperature with additional oxygen gas to accommodate oxidation. Iron oxide powders were milled in 6 hours then washed and dried. Roasting processwere performed at four varying temperatures of 480°C, 520°C, 560°C, and 600°C with oxygen influx 3L min-1, preceded by isothermal holding at 385°C. TGA-DSC (thermogravimetric analysis – differential scanning calorimetry) and XRD (X-Ray Diffraction) characterization has been performed to understand iron oxide behavior in response to thermal oxidation at moderate temperature. It is observed that two main reactions are clearly distinguished. In DTG curve, first peak indicate reduction followed by oxidation at the second peak. XRD results has shown that the highest content of α Fe2O3 was achieved by roasting at 600 °C for 1 hour which produced hematite portion of 31 wt. %, yet it is still insufficient to be utilized as raw material for ferrite based magnets fabrication. To prevent reduction reaction of Fe3O4 which will retard the oxidation process, it is suggested to avoid isothermal run or lower heating rate at temperature below 406°C