【作者】 曾涑源；

【导师】 唐凯斌；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2008， 博士

【摘要】 近年来,α-Fe₂O₃纳米结构因其在涂料、传感器、催化以及电极材料等方面的应用而成为近年来研究的热点。本论文的主要研究目的在于利用基于液相的化学路线对α-Fe₂O₃纳米结构进行制备。通过对于反应过程的研究,提出一些合理的模型来解释α-Fe₂O₃纳米结构的生长机制,对所得α-Fe₂O₃纳米结构的性能进行测试,寻找形貌与其物理性质之间的联系,以期制备出的α-Fe₂O₃纳米结构具有所期望的物理性质。论文的主要内容总结如下:1.使用Na₂SO₃和FeSO₄为原料合成了α-FeOOH的纳米棒,并通过煅烧前驱体的方法制得了α-Fe₂O₃的一维纳米棒。研究了反应物浓度对于产物形貌的影响,并且通过改变反应物的用量得到了一系列具有尺寸梯度的α-Fe₂O₃纳米棒。研究了产物尺寸对于化合物性质的影响。结果显示所得α-Fe₂O₃纳米棒的光吸收性质、电化学性质、磁性以及光催化性能与纳米棒尺寸之间的都有着密切的联系。2.使用乙醇作为溶剂,FeCl₃.6H₂O作为原料,在溶剂热的条件下制备了α-Fe₂O₃的花状多孔纳米结构。研究了乙醇在反应中的作用,发现所使用的乙醇除了作为溶剂之外,其本身也通过醚化的方式提供水分子参加反应。对于反应溶剂对于产物形貌的研究进行了详细的研究。并对多孔结构对其磁性、电化学性能以及光催化性能的影响进行了初步表征,结果显示,由于产物具有较大的比表面积,使得其在M-T曲线中无法观察到Morin相变,而与此同时,产物在锂离子电池以及光催化方面的性能的因为所具有的多孔结构而得到相应的增强。3.使用草酸辅助的水热方法,成功的对α-Fe₂O₃空心纳米结构实现了选择型的制备,通过控制不同的碱源,分别得到了α-Fe₂O₃的空心椭球颗粒和空心微米球。研究了草酸以及碱的用量对于所得产物形貌的影响,并进一步对不同碱源对于产物的影响进行了研究。根据所观察到的实验事实,提出了基于Ostward熟化过程的生成机理。考虑到产物所具有的空心结构,所得α-Fe₂O₃空心纳米结构在锂离子电池以及水污染处理方面的应用进行了初步探讨,结果显示空心结构有利于产物在锂离子电池中循环性能的提高,同时空心结构也使得其对离子的吸附能力显著增强。4.使用无机盐辅助的水热方法对于海胆状α-Fe₂O₃纳米结构进行了制备,并对无机盐种类对于产物的影响进行了研究。研究了无机盐浓度对于所得产物的影响并对相关现象进行了解释。通过改变无机盐的种类,成功的获得了诸如纳米纤维、纳米立方块等一系列形貌。对所得海胆状α-Fe₂O₃纳米结构的磁性质进行了表征,结果表面,由于产物的具有交对称的形状,使得其在室温下矫顽力极小。我们进一步使用所得的α-Fe₂O₃海胆状纳米结构作为原料,实现了其与TiO₂的复合,形成了TiO₂@α-Fe₂O₃复合结构。并对所得复合结构的光催化性能进行了表征,结果显示,比起单独的α-Fe₂O₃海胆状纳米结构,所得复合结构在光催化性能上有了明显的增强。更多还原

【Abstract】 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.更多还原