【作者】 王红；

【导师】 李晓天；

【作者基本信息】 吉林大学 ， 材料物理与化学， 2008， 博士

【摘要】 本论文以水热合成法为主要研究手段,通过调控水热合成条件,成功合成了一系列具有特殊形貌的氧化铁纳米材料,实现了对氧化铁粒子结构、尺寸、形状的控制,总结了晶体的生长规律,并探讨了产物形成的可能机理。具体内容如下:1.合成了平均粒径为100 nm的单分散氧化铁纳米粒子。产物具有良好的磁学性质。表面活性剂对粒子的分散性起到了决定性的作用。此外,还合成了单分散立方体氧化铁微粒。研究表明,反应时间、反应温度,pH值和反应物的配比对以上两种产物均有很大的影响。2.采用水热法制备了尺寸均一和结晶完整的微孔球状氧化铁纳米粒子。实验结果表明,反应温度和溶液pH值对晶粒尺寸和形貌有重要影响,对产物的磁学性质研究表明,产物具有与体材料不同的磁学性质。此外,以溶剂热方法合成了球形氧化铁纳米粒子,通过调节溶剂一元醇碳链的长度,实现了对其尺寸的控制合成。3.采用水热方法合成了空心球、球壳状、桔子瓣状、珊瑚状、棒状、梭形等多种形状和尺寸氧化铁微粒,并对产物形成的机理进行了研究。通过调节溶液pH值、反应物浓度和反应温度实现了对粒子形貌的控制合成。利用溶剂热方法,成功地合成了平均粒径为50nm的Fe3O4纳米粒子。通过加入不同表面活性剂、盐和溶剂等,实现了对Fe3O4纳米粒子尺寸的控制合成。研究表明,此纳米粒子具有超顺磁性质。4.设计制备了钙、铁双元类水滑石化合物,并选择性溶出其中的钙来制备多孔纳米水铁矿。研究了其作为锂离子电池电极材料的电化学性质。研究结果表明通过选择性溶出方法制备的水铁矿具有较高的放电容量和较好的循环性能。更多还原

【Abstract】 To control the structure, size and morphology of nanomaterials is a great goal in the fields of synthetic chemistry and materials science, because the physical and chemical properties of materials depend not only on the chemical composition, but also on their size and shape. Aiming at novel functional materials, many efforts have been focused on synthesis of monodispersed nanocrystals with various shapes. Although many materials have been prepared by hydrothermal methods, it is still difficult to obtain materials with controllable morpologies. Therefore, a number of researchers have focused on developing effective hydrothermal methods to control the size and/or shape of nanoparticles. In the past few decades, iron oxide, as one of the most important transition magnetic metal oxides, has received increasing attention due to its extensive applications, such as magnetic recording materials, catalysts and biomedical applications. Many efforts have been directed toward the fabrication of iron oxide nanomaterials with different shapes and sizes to enhance their performance in current applications.In the present work, monodispersedα-Fe2O3 nanoparticles modified by surfactant with good-crystalline properties and size of 100 nm on average have been successfully synthesized via a hydrothermal process. The as-prepared products were characterized by XRD, FTIR, SEM, SQUID. The effect on reaction time , reaction temperature , pH and starting mixtures to the morphologies of hematite in the hydrothermal conditions have been studied. It is found that sodium dodecyl benzene sulfonate (SDBS) surfactant plays an important role on controlling the final morphology of the products. Magnetic hysteresis measurements reveal that monodispersedα-Fe2O3 nanoparticles exhibit normal ferromagnetic behaviors with the remanent magnetization and coercivity of 0.2389 emu/g and 2339.0 Oe at room temperature. Monodispersed pseudocubic hematite (α-Fe2O3) particles were synthesized through a hydrothermal method. When the concentration of surfactant and FeCl3 were changed, the particles with tunable sizes were obtained. The capping agent–cationic surfactant–CTAB can confine the growth of products.The sphericalα-Fe2O3 nanoparticles were obtained under hydrothermal conditions. The products were characterized by XRD, SEM, TEM, ED, IR, TG-DSC, BET etc. The results indicate that spherical, diamond-like, plate-like hematite particles can be obtained by adjusting the pH value of the starting mixtures. The sizes of particles change from nanometer to micrometer scale. Morphologies ofα-Fe2O3 particles can be controlled. It is interesting to note that the spherical nanoparticles are single crystals possessing unique microporous structure. The temperature-dependent magnetic susceptibility curve shows that the as-synthesized microporous sphericalα-Fe2O3 nanoparticles possess a blocking temperature of 119 K. Furthermore, sphericalα-Fe2O3 nanoparticles have been synthesized in aliphatic alcohol solution. The particle size of sphericalα-Fe2O3 nanocrystals can be controlled by adjusting the alkyl carbon chain aliphatic alcohol in the solvothermal method. For example, we synthesized sphericalα-Fe2O3 nanocrystals with sizes of 100,80 and 50 nm through the reaction in the ethanol, propanol and butanol, respectively.Uniform hollow hematite (α-Fe2O3) spheres were obtained by hydrothermal method. XRD, SEM, and SQIUD measurement were used to characterize the final products. It shows a normal ferromagnetic behavior at room temperature with remanent magnetization and coercivity of 0.2482 emu/g and 2516 Oe at room temperature. The effects of reaction time and temperature on the formation of the hollow spheres are investigated. The growth of the hollow spheres may be related to the gaseous cavities resulted from the freshly produced CO2, which act as heterogeneous nucleation centers for the growth of single crystal or polycrystalline. Sphere shell-likeα-Fe2O3 particles and tangerine-likeα-Fe2O3 particles have been prepared by a template-free hydrothermal synthetic route. Coral-likeα-Fe2O3 superstructures have been obtained by water assisted solvothermal process, and reaction temperature was the crucial factor that determined the morphologies of the products. Magnetic hysteresis measurements reveal that coral-likeα-Fe2O3 superstructures display normal ferromagnetic behaviors with the remanence and coercivity of 0.2346 emu/g and 1862 Oe at room temperature. Uniform shuttle-likeα-Fe2O3 particles andα-Fe2O3 nanorods could be formed by hydrothermal reactions. Their sizes can be controlled by adjusting the pH and concentration of starting mixtures.Magnetite (Fe3O4) nanoparticles have been synthesized in novel solution without adding any additives, using FeCl3?6H2O and NH4HCO3 as the starting materials. The experiment results reveal that the solvent have important influences on the phase and morphology of the products based. The nanoparticles exhibit a superparamagnetic behavior and saturation magnetization strength of 70.87 emu/g according to the magnetic hysteresis curve measured at room temperature. The magnetite has a high Brunauer-Emmett-Teller (BET) surface area of 55.45 m2/g. The nanoparticles size can be controlled in the range of 10-90 nm in diameter by changing surfactant or inorganic salt in the solvothermal process. They showed different saturation magnetization strength. By simply using different solvents, superparamagneticα-Fe2O3 nanoparticles have been efficiently obtained and the average size of the spherical particles is around 60 nm.We first investigated the potential of 2-line ferrihydrite for application in electrode materials of lithium ion battery. Besides the conventionally rapid hydrolysis route, a novel selective extraction route from layered double hydroxides (LDHs) and their calcinates (LDOs) has been designed and employed to prepare 2-line ferrihydrite. The electrochemical results reveal 2-line ferrihydrites from LDHs is one of the best of them, possessing a high discharge capacity of 133.4 mAh g–1 after the activation process and a good cycle performance remaining 115.4 mAh g–1 after 21 cycles.更多还原