Synthesis of Spinel MnCo_2O_4 by Thermal Decomposition of Carbonates and Kinetics of Thermal Decomposition of Precursor

摘要

The cubic MnCo_2O_4 was prepared by calcining MnCO_3-2CoCO_3·1.5H_2O above 600℃ in air. The precursor and its calcined products were characterized by thermogravimetry and differential scanning calorimetry, Fourier transform infrared spectroscopy, X-ray powder diffraction, scanning electron microscopy, and vibrating sample magnetometer. The result showed that high-crystallized MnCo_2O_4 with cubic structure [space group Fd-3m(227)] was obtained when the precursor was calcined above 600℃ in air for 6 h. Magnetic characterization indicated that cubic MnCo_2O_4 behaved weak magnetic behavior at room temperature. The thermal process of the precursor in air experienced three steps, which are: first, the dehydration of 1.5 water molecules, then the decomposition of MnCO_3-2CoCO_3 into cubic MnO_2 and cubic Co_3O_4, and at last the reaction of MnO_2 with Co_3O_4 into cubic MnCo_2O_4. Based on the KAS equation, the values of the activation energies associated with the thermal process of MnCO_3-2CoCO_3·1.5H_2O were determined.