Study On Control Synthesis And Properties Of Micro-Sized Materials By Soft Chemistry Routes

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.