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Title

EFFECT OF MECHANICAL ACTIVATION ON CARBOTHERMIC REDUCTION OF MOLYBDENITE IN THE PRESENCE OF MAGNESIUM OXIDE

Pages

 Start Page 109 | End Page 123

Abstract

 In this study, the effect of MECHANICAL ACTIVATION on Carbothermic reduction of MOLYBDENITE in the presence of MAGNESIUM OXIDE was studied. MECHANICAL ACTIVATION of all powder mixtures (Molybdenite: Graphite: MAGNESIUM OXIDE=1: 2: 2) was performed in argon atmosphere for different time periods (0-50 hours), using a planetary ball mill. Phase changes in the powder mixtures were investigated by X-ray diffraction (XRD). The Results showed that no reaction occurred in the mill to produce new phases in the mixtures. Observations indicated that Carbothermic reduction of MOLYBDENITE in the presence of MAGNESIUM OXIDE was formed as easily as possible and goes on by formation of intermediate phases such as Molybdenum Oxide (MoO2) and Magnesium Molybdate (MgMoO4). The effects of MECHANICAL ACTIVATION on the reduction of different samples were thoroughly investigated by simultaneous Thermal Analysis (STA). The samples were heated in argon atmosphere with the linear heating rates of 10, 15, 20oC/min. The plots of process conversion degrees showed that the reaction temperature in the reduction reaction starting temperature is strongly affected by the amount of MECHANICAL ACTIVATION. So that by doing 50 hours of milling, the temperature of the starting of reduction reaction was decreased by about 170oC. KINETICS reduction of powder mixtures was studied by model- fitting (Coats-Redfern) and model-free (Ozawa and Friedman) methods the dominating Model over the reaction was the chemical control at the intersection and the amount of activation energy and pre-exponential factor was determined to be about 251 kJ.mol-1 and 1´106 Sec-1.

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