Investigation On Phase Transition Mechanism Of Iron(Ⅲ) Oxide And Ferroferric Oxide

Steel industry plays a major role in our national economy.With the rapid development of the national economy,the requirement of steel is intensely demanded.However,due to the disadvantage of poor endowment of Chinese iron resources,lag reserve growth,limited production capacity,serious shortage of self-sufficiency and etc.,which lead to a prominent contradiction of foreign incoming.Hence,it has great strategic importance to accelerate the rapid development of iron and steel industry and strengthen the technology and the development of metallurgical industry.In order to strengthen the theoretical research of beneficial process,we focus our attention on phase transition of Fe2O3 and Fe3O4 and investigate systematically,according to the combination of thermodynamic theory and experiment,it proves the order of reduction of hematite in magnetized roasting,as follows:calcination temperature less than 570℃,the reduction order is Fe2O3→Fe3O4→Fe;when calcination temperature higher than 570℃,the reduction order is Fe2O3→ Fe3O4→FeO→Fe.The optimal calcination temperature could be acquired by the reduction order,that is,much closed calcination temperature of 570℃,and the largest concentration of CO gas.Besides,the magnetized roasted products are susceptible to be oxydic when annealing in air,and strong magnetic maghemite(γ-Fe2O3)or hematite(α-Fe2O3)are produced.Experimental results show that the air could be passed when the temperature is cooled down to 230℃ and at that time,the amount of the magnetic hematite is the largest.In this reactions,a lot of thermal energy are produced and this energy could be recycled.In recent years,with the extensive applications of environmental magnetism,the magnetic hematite(γ-Fe2O3)is more and more recognized in our daily life.Magnetic hematite has metastable phase and the structure is similar with Fe3O4 which belongs to spinel structure.It could be transformed into α-Fe2O3 corundum structure at heating condition.This study proves that the γ-Fe2O3 is fit for the space group of P41212 by of Rietveld refinement.In addition,this article compares the magnetic origin of Fe3O4 andγ-Fe2O3 from the perspective of electron orbital and spin motion,and calculate the unit mass of saturated magnetic moment is 11:10.Analytical Fe3O4 sintering experiments proved that in the air or oxygen,the oxidation order is Fe3O4→γ-Fe2O3→α-Fe2O3.In addition,through the analysis of gibbs free energy thermodynamic,the reaction from γ-Fe2O3 to α-Fe2O3 is single irreversible,and which also proves that Fe3O4 is directly generated from α-Fe2O3 and no middle phase(α-Fe2O3)exists.