The Catalytic Dissolution Of Fe(OH)₃ Gel By Fe(OH)～+ And The Preparation Of Nanometer α-Fe₂O₃

Monodispersed a-Fe2O3 nanoparticles have been widely applied in fine ceramics, catalysis, light filter, light adsorption, medicine, anticorrosion, pigment, photosensitive materials and magnetic recording media, etc. The preparation of monodispersed a-Fe2O3 nanoparticles has been studied extensively. In our laboratory, a new method of preparing nanosized hematite by catalytic phase transformation in solution was successfully developed. In this method, FeCb. Fe(NO3)3 or Fe2(SO4)3 are main raw materials and Fe(OH)3 gel is firstly prepared, then a-Fe2O3, is obtained by the catalytic dissolution of Fe(OH)3in aqueous solution. It was considered that the new-method is with such outstanding characteristics as simple equipment, high initial concentration, fast rate of phase transformation, and gentle reaction conditions etc.On the basis of the former work of our laboratory, in this paper the main research aspects are as follows:(1)The preparation of Fe2(SO4)3 solutionFirst, pure iron with low carbon is acidized by FSO and then we can obtain FeSO4 solution. Second, Fe2(SO4)3 solution is prepared through the oxidization of the FeSO4 solution with HNO3. the obtained Fe2(SO4)3 solution haven't hydrolysis and is fit for the preparation of a-Fe2O3.(2) The effect of Fe(II) on the phase transformation of Fe(OH)3This research shows that when more Fe(II) is added, the diameters of a-Fe2O3 nanoparticles are smaller, but that there is a limit in the increasing of Fe(II) content. Moreover, a-Fe2O3 nanoparticles are more affected by the content of Fe(II) than the concentration of reactant Fe(III).(3) The effect of carboxylic acid on the phase transformation of Fe(OH)3In this paper, a small amount of carboxylic acid was added to the Fe(OH)3 gel under neutral condition, a-FeO with different morphology was produced after a certain period of reaction time. The effect of different carboxylic acid on the phase transformation rate and a-Fe203 morphologies was studied in this paper. The reaction mechanism was discussed.(4) The formation of intermediate product FeOOH and the effect on the preparation of a-The intermediate products FeOOH play an important role in the preparation of a-Fe2O3 In this particle, the reaction is studied under the dynamic and static condition. The research of three temperature 80 60 , 40 explains the proceeding of the transition of intermediate product a-FeOOH, (3-FeOOH and y-FeOOH during the the preparation of oc-Fe2O3, and their effects on the occurrence of a-Fe2O3.