Synthesis, Characterization And Catalytic Property Of Iron Oxide Nano-structure Via Hydrothermal/Solvothermal Route

Because of low costs,low pollutions,high resistance to corrosion and good stability,iron oxides are applied in many industry fields,such as catalyst,painting, magnetic recording medium,magnetic coating,gas sensor,gas sweetening and sewage disposal in environmental protection and so on.Iron oxide nanomaterails with different morphologies and sizes are superior to massive texture for its nanometer-effect.So,it is important to focus on the synthesis,characterization and performance study of iron oxide.In this thesis,α-Fe₂O₃ was synthesized via hydrothermal/solvothermal route, using ferric inorganic salts and KOH/NaOH as main-raw materials.The influences of solvent,capping agent,mineralizer,reaction time and temperature onα-Fe₂O₃ nanostructures were studied.The phases,morphologies and catalytic properties of samples were characterized by various testing methods.Probable reaction mechanisms were also discussed.The main work and results in this paper include:1.The squareα-Fe₂O₃ nanosparticles with uniform side length of 20～30nm were prepared via ethanol-thermal route,using oleic acid and oleyl amine as capping agents. The as-preparedα-Fe₂O₃ nanoparticles showed well crystalline and dispersibility.It was found that different ferric inorganic salts and the content of mineralizers and capping agents affect the morphologies ofα-Fe₂O₃ nanoparticles.The present method is simple and well repeated for the synthesis of squareα-Fe₂O₃ nanoparticles.2.Iron oxide powders with various sizes and shapes were prepared by solvothermal method using different volume ratios of ethylene glycol to distilled water.The phase,morphology of products and reaction mechanism were also investigated.Because of the chelation and deoxidization of ethylene glycol on Fe ion, and the effect of water on the formation and gowning of iron oxides,small size Fe₃O₄ particles were obtained with large quantity of ethylene glycol,while larger sizeα-Fe₂O₃ particles with short circular column,cube-like and spindle morphology were obtained with fewer ethylene glycol in mixed solution. 3.Large-scaleα-FeOOH nanorods were synthesized by hydrothermal reaction. Then theα-FeOOH nanorods were heat treated at different temperatures,and single crystalline and multiporousα-Fe₂O₃ nanorods were obtained.The results revealed that the phase transition ofα-FeOOH nanorods toα-Fe₂O₃ nanorods occurs between 239℃and 295.1℃.On the surfaceα-Fe₂O₃ nanorods,lots of holes appeared because of dehydration.The holes disappeared as the temperature increasing.4.α-Fe₂O₃/CuO mixed oxide powders with different molar ratios of Fe and Cu were prepared via hydrothermal route of Fe(NO₃)₃·9H₂O and Cu(NO₃)₂·3H₂O,using KOH as precipitator and mineralizer.Pureα-Fe₂O₃/CuO mixed oxides were obtained when 0.45～0.50g KOH was used.5.The temperatures for the exothermic decompositions of ammonium perchlorate (AP)over differentα-Fe₂O₃ andα-Fe₂O₃/CuO mixed oxide powders were tested and the catalytic property of iron oxides was investigated.The results showed that higher-temperatures of exothermic peaks of AP shifted towards low temperatures when differentα-Fe₂O₃ powders were introduced into the reaction.Particle size, special nanostructures and synergistic effect of transition metal oxides are main factors effecting the catalytic property of iron oxides.The decrement of higher-temperatures for exothermic decompositions of AP over quareα-Fe₂O₃ nanosparticles,short circular columnα-Fe₂O₃ nanosparticles,multiporousα-Fe₂O₃ nanorods andα-Fe₂O₃/CuO mixed oxide powders with the same molar of Fe and Cu reached 78.1℃,74.2℃,106.3℃and 143.9℃,respectively.