【作者】 张东恩；

【导师】 ??；

【作者基本信息】 中国科学技术大学 ， 无机化学， 2007， 博士

【摘要】 纳米材料在实际生产生活中有着非常广泛的应用。由于纳米材料的性质与其形貌和尺寸有着密切的关系，因此，制备具有特殊形貌和优良性质的纳米材料一直是材料领域的研究热点。本论文旨在探索纳米无机磁性材料和电极材料的制备方法，研究材料结构和性质之间的关系。1．在液相体系中，利用水合肼和金属镍盐作为反应物，采用微乳液软模板控制镍的生长，得到金属镍纳米棒。利用X—射线衍射（XRD），透射电子显微镜（TEM）等研究了产物物相和微结构。通过对比实验，探讨了纳米粒子的生长机理和影响粒子生长的各种因素，并对产物磁性进行了测量。2．采用液相水合肼还原法制备出铁纳米粒子，反应条件温和简单，过程易操作。压力对反应有比较关键的作用。同时研究了碱的浓度和溶剂等实验条件对反应是否能够进行的影响。在表面活性剂十六烷基三甲基溴化铵（CTAB）的存在条件下，制备得到分散较好的微米级棒状产物。表面活性剂CTAB在微米棒的生成过程中起到了重要作用：一是作为纳米颗粒的稳定剂；二是扮演着晶习改变剂的角色，CTAB可能是有选择地吸附在生长颗粒的某些晶面上，导致这些晶面的生长速率大大降低，从而使具有各向同性结构的晶体发生各向异性的生长。该表面活性剂辅助的低温溶液法，对合成其它具有各向异性晶体结构的铁磁材料的一维结构具有一定的指导意义．3．利用聚合物辅助水热合成技术成功合成出了NiFe₂O₄和Fe₃O₄纳米材料，并对其结构和磁学性能进行了一系列的表征。利用聚乙二醇（PEG-400）完全伸展的高分子链对纳米晶核的吸附与限制作用，合成了NiFe₂O₄一维纳米材料；对比实验结果表明一缩二乙二醇（DEG）在六边形Fe₃O₄纳米片的形成过程中发挥了决定性作用。整个聚合物辅助水热路线的优点在于操作简单、反应温度低、反应过程及产物的结构和形貌易于控制。4．利用EDTA和三乙醇胺等不同配位剂的辅助作用，水热合成了具有八面体形貌的Fe₃O₄、MnFe₂O₄等铁氧体颗粒。EDTA、DEA是强的配位体，它能与金属离子形成稳定的配合物，降低了溶液中自由金属离子的浓度，使得反应速率大大的降低，从而使得晶体的生长速率也大大得降低，较低的生长速率更有利于晶体沿着<100>方向生长，不会沿着其他面快速生长，只会在八面体的八个{111}面均匀生长，最终得到微米级的八面体颗粒。将此配位剂辅助合成法推广应用到其它铁氧体体系，结果都能够获得大量的尺寸均一的八面体颗粒，证实了该反应路线的普适性。5．探索了新型锂离子电池负极材料CeO₂的制备方法。（1）先利用沉淀法得到草酸盐的一维纳米前驱物，再通过低温热解来制备CeO₂纳米棒。由该路线合成的纳米棒具有物相纯，颗粒尺寸均一和结晶好等优点。（2）通过低温水热合成路线，成功合成了纺锤体形及三足状树枝形枝晶CeO₂纳米结构材料。性质研究表明，所合成的氧化物具有良好的光学性质和优异的电化学性能，对电极材料的发展预期有较大的推动作用。更多还原

【Abstract】 Nanoscaled materials show wide applications in practical life. The properties of nanomaterials have intimate relations with their sizes and morphologies. Therefore, the preparation of nanomaterials with special shapes and excellent properties has been put much atention by researchers. The aim of this thesis involved the preparation and properties characterization of magnetic metal materials and electrode materials with nanosize.1. Rod-like nickel nanoparticles with a diameter of 6-18 nm and a length of 100 nm have been prepared in the cationic w/omicroemulsion of water/CTAB/ n-butanol/n-octane by reduction of nickel chloride with hydrazine hydrate. X-ray difraction （XRD）, Transmission electron microscopy （TEM） and Scanningelectron microscopy （SEM） and some other techniques were used to characterize the phase and microstructure of the products. Several factors influencing the growth of particles were investigated. The magnetic properties of the product were also measured.2. A mild one-step route was successfully established for the preparation of iron nanoparticles by reduction of iron salts with hydrazine hydrate in a strong alkaline solution. Pressure played an important role for the fabrication of a pure a-Fe phase. The effects of the concentration of alkali and solvents on the formation of iron were also investigated. This synthetic method proved to be very facile and easy to be scaled up. Rodlike Fe particles were prepared in the presence of CTAB. The use of CTAB is a key factor that influences the formation of the microrods from the contrast experimental: suppressing the aggregation of metal nanoparticles in initial stage of crystal growth, and kinetically controlling the growth rates of various crystallographic facets of face-centered cubic metals through selectively adsorbing on these facets. The present method is expected to be transferable to other magnetism materials.3. Solution-based routes assisted by polymers were developed to synthesis of NiFe₂O₄ and Fe₃O₄ nanoparticles. The as-prepared powders were characterized in detail by conventional techniques such as XRD,SEM and TEM, and their magnetic properties were evaluated on a vibrating sample magnetometer. It is found that the full extension of the polymer chain of PEG-400 are responsible for the 1D growth of NiFe₂O₄ nanorods; the results obtained from contrast experiment indicate that the DEG has a significant influence on the formation of flake-like Fe₃O₄ nanocrystals. The advantages of this synthesis method are: simplicity of operation, low reaction temperature, and the controllable reation process, structure and morphology of the resulting products.4. A complexant-assisted solution-phase approach was developed to prepare uniform octahedrons of Fe₃O₄ and MnFe₂O₄ It should be noted that complexants EDTA and TEA are strong coordinating agents, could coordinate with matel ions forming very stable complexes. The formation of the complexes can kinetically control the reaction rates, the slow reaction rate is favorable for the faster growth rate along <100> over that along <111> due to the lowst energy of the {111} surfaces. Such a complexant-assisted method could be extended to the other ferrite formation, which was proved as a general route for the synthesis of octahedron-like ferrite particles.5. The synthesis of new anode materials for lithium ion batteries of CeO₂ is discussed. （1） CeO₂ nanorods particles were obtained by the thermal decomposition of the 1D metal oxalate precursors at relatively low temperature. The resulting nanorods are pure and well crystallized with narrow size distribution. （ 2） Three-fold shape dendritic crystal and spindle of CeO₂ particles were synthesized thorough low temperature hydrothermal route. The results of the examination on the properties show that the as-prepared oxides exhibit excellent opticles and electrochemical properties. The high capacity of CeO2 crystallites makes it attractive as a possible cathode for rechargeable lithium cells in the future.更多还原