In this study, the effect of mechanical activation on structural changes, reducing behavior and reduction kinetics of the hematite-Graphite mixture in the presence of Iron was investigated. For this purpose, a mixture of hematite-graphite (with the stoichiometric ratio C/O = 1) in the presence of different amounts of iron (0, 5 and 10 wt%) was milled from 0 to 50 hours. In order to study structural changes in the process of grinding, XRD analysis was performed on the samples. The morphology of the powder mixture during milling was studied using SEM analysis. It is obsereved that after 5h millig, the peak corresponding to graphite was completely eliminated that was concerned to amorphisation of graphite structure. It was founded that with increasing milling time, the diffraction patterns of the magnetite peak gradually appeared and their intensity increased. Also the wustite peak appeared in diffraction pattern whith 50h milling. It was concern to reduction of some hematite to magnetite and wustite during milling. The grain size and lattice strain of hematite powder particles were determined using the Williamson - Hall method. Also mechanical activation parameter (?/d) was calculated and used as a criterion of the energy stored in the powder mixture. The results showed that the existing of Iron had positive effect on decreesing of grain size, increasing structural strain and mechanical activation parameter. SEM images showed the formation of dense structures in the long time of milling, indicating the amount of energy stored in the powder particles. Reducing and kinetic behavior of the samples was studied using TG-DTA analysis by 10, 15 and 20 °C/min of heating rate from room temperature to 1200 °C. The results showed that with increasing milling time, temperature of reaction initiation reduced. Reduction patterns showed that the start temperature of the reduction in presence of 5% wt of iron was reduced 60 °C. Reduction kinetics studies was carried out using model-free method of (Ozawa (FWO) and Kissinger (KAS)) and the constant slope fitting method. These studies showed that the grinding, reduces the activation energy of reduction. For example 50 hours of milling reduces the activation energy to 50 percent. The presence of iron was very effective so that in the presence of 5 wt% iron, the activation energy decreased to less than one-third. Calculation of activation energy of the activated and inactivated samples by model-free and constant slope methods and their comparison showed that the reaction was of chemical control type and the carbon gasification reaction was determined as the controlling step in presence and absence of Iron for the carbothermic reduction of hematite with graphite. Keywords: Carbothermic reduction, kinetic analysis, thermal analysis, mechanical activation, catalyst, activation energy, catalytic effect of iron, hematite.
