بررسي اثر آهن بر فعال سازي مكانيكي و احياي مخلوط هماتيت

چكيده انگليسي :

AbstractIn this study the effect of iron on mechanical activation MA structural evolution and reductionbehavior of hematite H and graphite G mixture has been investigated Different amounts of iron 0 10 wt were added to the H G C O 1 powder mixture Then mechanical milling in an inertatmosphere was performed on H G Fe mixtures for different time periods 0 50 hr using aplanetary ball mill X ray diffraction XRD analysis revealed that G peaks completely disappearedin diffraction patterns of samples milled for more than 5 hr due to the annihilation of G crystalstructure In addition magnetite M peaks emerged in diffraction patterns of samples milled for 10hr and more indicating the reduction of some of the H to M due to milling in the presence of G Obtained results regarding the grain size and structural microstrain of H particles by using one ofthe methods based on integral breadth analysis Gaussian Gaussian approach showed that millinghas a tremendous impact on reducing the grain size and increasing the structural microstrain of Hparticles and iron enormously intensifies the changes Furthermore it was found that H and Gamorphization degree and H dislocation density increased by extending the milling time andincreasing the iron content The MA parameters tan and d were introduced for evaluation ofMA and also as criterion for comparing the intensity of MA in different mixtures The obtainedresults from the methods were in agreement with previous findings regarding the effect of millingtime and iron content on intensity of MA and stored energy in the mixtures Scanning electronmicroscopy SEM observations revealed that MA produces a compacted composite structure ofparticles especially in samples milled for more than 5 hr The formation mechanism of theaforesaid structure is by getting stuck of H and G brittle particles in iron ductile particles This stateleads to a considerable increase in stored energy Therefore iron not only intensifies the structuralevolution of H G mixture but also accelerates taking place of different stages of MA The effect ofmilling time and iron content on reduction process of different samples was thoroughlyinvestigated by STA Samples were heated in an argon atmosphere with a constant heating rate of10 C min from room temperature to 1200 C TGL and DTA curves of different samplesillustrated that by increasing the milling time and iron content and as a result of higher storedenergy in the mixture the initial temperature of all the reduction reactions notably reduces whiledegree of reduction increases Additionally RTG and DSC curves showed that reduction rateincreases and necessary heat for reduction reactions decreases as milling time and iron contentincreases Catalytic effect of iron on reduction process was observed The catalytic effect of iron onreducing the reaction temperature and accelerating the reduction process was notable especially insamples with higher contact area between particles samples milled for 30 hr and more The initialreduction temperature in H G samples with 10 wt Fe and milled for 30 and 50 hr reduces to 520and 490 C respectively A mechanism was proposed for catalytic effect of iron

طهماسبي، رسول

بررسي اثر آهن بر فعال سازي مكانيكي و احياي مخلوط هماتيت - گرافيت

روش گوسي- گوسي