تاثير فعال سازي مكانيكي بر احياي كربوترمي موليندنيت در حضور كربنات سديم

چكيده انگليسي :

Effect of mechanical activation on the carbothermic reduction of molybdenite in the presence of sodium carbonate Kazem Sheybani k sheybani@ma iut ac ir November 10 2013 Department of Materials Engineering Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Supervisors Mohammad Hasan Abbasi Prof Abbasi32@cc iut ac ir Morteza Shamanian Prof Shamanian@cc iut ac ir Abstract In this research the effect of mechanical activation on structural changes and reduction treatment of mixed powders from molybdenite graphite and sodium carbonate have been studied Also thermodynamic and kinetics of carbothermic reduction of molybdenite in the presence of sodium carbonate were studied To study the effect of mechanical activation on structural changes and reduction reaction mechanical activation of mixed powders of molybdenite graphite and sodium carbonate with 1 4 2 mole ratio was carried out via milling in a planetary ball mill under argon atmosphere for 10 20 40 50 and 70 h To study the effect of sodium carbonate amount on structural changes and reduction reaction mixed powders from molybdenite graphite and sodium carbonate with three mole ratios 1 4 2 1 4 3 and 1 4 4 were mechanically activated for 40 hours The results of X ray diffraction for activated samples showed that no reaction occurred during milling in different samples The effect of mechanical activation on grain size and lattice strain of molybdenite particles was investigated by Williamson Hall method The results indicated that the grain size of molybdenite decreased with increasing the activation time and grain size of molybdenite increased with increasing the amount of sodium carbonate in different samples SEM micrographs of activated samples indicated that increasing the activation time led to the reduction of particle size and formation of agglomerate particles In order to study the kinetics of carbothermic reduction of molybdenite in the presence of sodium carbonate simultaneous thermal analysis STA under heating rates of 10 15 and 20 0C min was carried out on the activated samples XRD patterns and thermadynamic analysis of reaction products indicated that carbothermic reduction of molybdenite in the presence of sodium carbonate was advanced through the formation of intermediate phases Na2MoO4 MoO2 where the final products were Mo 2C Na2S The kinetics of reduction reaction was investigated using Friedman Kissinger Ozawa and Coats Redfern methods and it was found that Mechanical activation decreased the reaction temperature and activation energy Also it was found that the temperature and activation energy of molybdenite carbothermic reduction in the presence of sodium carbonate increased with increasing the amount of sodium carbonate The kinetic model for non activated molybdenite was determined as chemical control with E 218 kJ mol A 1 69 106 S 1 and mechanical activation of mixture for 70 h changed the kinetic model to chemical control in interface with E 143 6 kJ mol and A 7 31 109 S 1 For the sample activated for 40 h with the mole ratio of 1 4 4 the kinetic model was found to be diffusion control Key words Molybdenite carbothermic reduction kinetics mechanical activation sodium carbonate

شيباني تذرجي، كاظم

تاثير فعال سازي مكانيكي بر احياي كربوترمي موليندنيت در حضور كربنات سديم

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