The Synthesis And Characterization Of Rare Earth Oxide Nanotubes And Nanowires

The rare earth (La, Ce, Nd and Sm) oxides nanotubes and nanowires were synthesized by taking surfactants as the structure-directing agents. The thermal stability of products and effects to nanotubes and nanowires of surfactants were investigated in detail. The products' structure, formation mechanism and crystal transformation were also been studied. The materials have been characterized by Powder X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), the selected area electron diffraction (SAED) and FT-IR spectra. The results are showed in the following:(1) The SDS as template-agent, urea as precipitating agent and nitrate cerium(Ⅳ) as rare earth resource, the lamellar mesostructured materials were synthesized in hydrothermal condition at 80℃. The effects of reaction time, pH values and other factors to the mesostructure were also been studied.(2) The octadecylamine (C18H37NH2) as template-agent, urea as a precipitating agent and nitrate cerium(Ⅳ) as rare earth resource, the hierarchically well-aligned nanotublar bunches of the cubic fluorite ceria were successfully synthesized. The products exhibited the hierarchically well-aligned nanotublar bunch which was composed of single nanotube with outer and inner diameter 10~20 and 5~6nm. The growth process of nanotublar bunches was monitored. Firstly, the separated nanotube appeared in the reaction system. Subsequently, the separated nanotubes integrated into the hierarchically well-aligned nanotublar bunch each other. In addition, the products have different crystalline phase and composition as increasing the final pH value of reaction system; And when the final pH values of reaction system were at 5~6, 6~8 and >8 respectively, the crystalline phase of the products were respectively cubic fluorite CeO2, mixtures of cubic fluorite CeO2 and hexagonal CeCO3OH, hexagonal CeCO3OH.(3) The cubic fluorite CeO2 nanowires were synthesized by the reaction of nitrate cerium (Ⅳ) with ammonia in the presence of template-agent octadecylamine. HRTEM observations indicate that the products have lengths up to several hundreds of nanometers and diameters around 20nm. XRD patterns of the samples show that the characteristic diffraction peaks of a cubic fluorite structured CeO2. SAED patterns of the samples show that they are single crystals. The FT-IR spectrum of the material, after calcinations at 673K, shows that the surfactant has been eliminated. The growth morphologies of the cubic CeO2 single crystal nanowires were monitored at different periods of hydrothermal process, which clearly revealed the formation process of the CeO2 nanowires. In addition, the proposed formation mechanism of nanowires was given. (4) Changing the rare earth resource, hexagonal La(OH)3 nanowires, tetragonal La2CO5 nanowires, cubic Nd6O11 and Sm2O3 nanowires and nanorods had also been synthesized using octadecylamine (C18H37NH2) as template-agent,ammonia as a precipitating. And all products can still keep the one-dimensional structure.