Preparation of mechanically activated aluminum-rich Al-Co₃O₄ powders and their thermal properties and reactivity with water steam at high temperature

A series of activated Al-Co₃O₄ powders were prepared by high-energy ball milling, and characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), thermogravimetric analysis (TGA), and differential scanning calorimeter (DSC). The properties of these activated Al-Co₃O₄ powders reacting with the water steam were systematically investigated at 700°C, 800°C, and 900°C. Morphologies and phases of their reaction products with water steam were characterized by SEM, XRD, and the residual metal aluminum content in products was also measured. The results showed that the reaction properties of the Al-Co₃O₄ powders with the water steam were closely related to the milling time. The Al-Co₃O₄ powder experiencing 3 h milling showed the finer particle size, lower initial oxidation temperature, earlier autoignition, and longer combustion in the water steam at high temperature than the other samples. The Co₂Al₉ alloy was detected in the reaction products of Al-Co₃O₄ powders with water steam. The investigation demonstrated that the activated Al-based powders could be prepared with the Al and Co₃O₄ through high-energy milling process.