Synthesis Of α-Fe₂O₃ By The Solution-based Method And Its Characterizations

Recent year,much attention has been focused on the synthesis and properties of hematite(α-Fe₂O₃)nanostructures due to its wide application in various fields such as pigment,sensors,catalyst and electrode materials.In this dissertation,solution-based chemical routes were employed in the preparation ofα-Fe₂O₃ nanostructures.By investigating the experiment process,some reasonable growth models are proposed for the formation of the hematite nanostructures.The physical properties of the as-obtained hematite nanostructures are investigated in order to find out the relationship between the morphology and physical properties,which will facilitate the preparation of hematite naostructures with desired physical properties.The main points of thedissertations are summarized as follows:1.By using Na₂SO₃ and FeSO₄ as the starting materials,α-FeOOH nanorods was successfully synthesized,which could convert to hematite nanorods through calcinations.The influence of the reactants' concentrations on the morphologies of the products is carefully investigated,which result in the hematite nanorods with gradient in size by simply changing the concentration of the reactants.The relationship between the size and the physical properties of the product are also carefully investigate,which clearly shows that the absorption,electrochemical,magnetic and photocatalytic properties are closely related to the size of the product.2.By solvothermal treatment of FeCl₃.6H₂O in ethanol,porous hematite nanoflowwer are successfully prepared.The role of ethanol played in the synthesis of such nanostructures are carefully investigated,which shows that the ethanol not only act as the solvent but also as the reactant.The influence of the solvent on the morphologies of the products is investigated.The porous structure has great effect on the magnetic,electrochemical and photocatalysis properties of the product,for example,the Morin transition of the as-obtained product disappears due to the high surface area of the product,while the performance of the product in lithium ion battery and photocatalysis is greatly enhanced by the porous structure.3.Using the oxalate acid as the chelating reagent,the selective preparation of hematite hollow structures has been realized,by using different basic source as starting material,hematite hollow spindles and hollow microspheres has been prepared respectively.The role of oxalate acid is discussed.The amount and kind of the basic source is also discussed in detail.Based on the experiment fact,a growth model based on Ostward Ripeng process is proposed.Considering the unique hollow structure of the product,the application of the as-obtained hematite hollow structure in lithium ion battery and water treatment are investigate and the result shows that the cycling performance of the product in lithium ion batter and the performance in water treatment are greatly enhanced by the hollow structure.4.Hematite nanoparticles with sea urchin-like morphology have been successfully prepared by the inorganic salt assisted method.The influence of the inorganic salt's kind on the product is carefully discussed.The influence of the inorganic salt's amount on the product is investigated and a reasonable explanation is given.By changing the inorganic salt present in the solution,product with different morphology such as nanofibers and nanocubes are obtained.The magnetic properties of the sea urchin-like hematite are investigated with show that the coercivity force of the product is really low due to its symmetrical shape.The product could be encapsulated by TiO₂ to form the TiO₂@α-Fe₂O₃ composite structure.The photocatalytic properties of the composite structures are also investigated,which clearly shows that the photocatalytic performance of the product is greatly enhance by the encapsulation of TiO₂ outward.