Preparation And Characterization Of Rare Earth Compound Nanomaterials

In this dissertation, nanomaterials of rare earth compound have been studied. Firstly, the cerium oxide nanomaterials were synthesized via templated method and microemulsion mediated hydrothermal process. By systematically adjusting the reaction parameters such as temperature, sorts of surfactant, sorts of solvents, and calcinations methods, the size and dimension of the product cerium oxide nanomaterials could be successfully controlled. Secondly, the composite carbon nanotubes coated with monodisperse CeO₂ and SnO₂ nanoparticles were prepared by using microwave heating method. Thirdly, the small dimension nanoparticles and walnut-like nanoparticles of Lanthanum phosphate were produced through microwave-solvothermal process and solvothermal process. The growth process and the possible microstructure controlling mechanism of the cerium oxide nanomaterials were also studied based on the thermodynamic and kinetic analysis combined with the electron microscopy observations and structure characterizations. In addition, the optical properties of cerium oxide, tin oxide, rare earth oxide coated carbon nanotubes, and Lanthanum phosphate nanomaterials were also studied.The influence of reaction conditions on the morphology development of CeO₂ nanomaterials were systematically studied and therefore realized the product dimensional control. Under different reaction conditions, CeO₂ nanowire, nanorod, prism-like and comet-like nanomaterials were obtained respectively. Based on the electron microscope observations and the structure characterization of the products, it was found that when the pH value of the system is higher than 7 the reaction precursor was CeOHCO₃. Adding different surfactants could change the morphology of CeOHCO₃. When the pH value of the reaction system is lower than 7, the component of the precursor became the hydrate of cerium oxide rather than CeOHCO₃. The sorts and flow rate of the caning gas in the calcination process were believed also to have influence on the morphology of the products. The ratio of alcohol to water also determined the component and morphology of the precursor in the alcohol/water mixedsolvents. When the precursor component remained unchangeable, adding different surfactant in mixed solvents system could determine the morphology of precursor as well as the final products.In another part of the dissertation, our study was focused on coating the semiconductor oxides of CeCh, SnO2 and their mixture on the carbon nanotubes using microwave method. Since the microwave heating was uniform and the reaction time was short so that the products did not need calcinations and the nanoparticles with a diameter of 3-4nm could well coated on carbon nanotubes to form a monodisperse coating. The optical properties of these composites were also studied.In addition, nanoparticles of Lanthanum phosphate and Lanthanum phosphates doped with rare earth ions with small dimension and walnut-like shape were also synthesized via microwave-solvothermal methods and solvothermal methods.In summary, we successfully prepared rare earth oxide and Lanthanum phosphate nanomaterials and controlled their size and morphology by different synthesis approaches in liquid phase such as template method, microemulsion-solvothermal method, and microwave method. It was found that the composition and morphology of the reaction precursor is a key factor on the morphology of the final product. Illustrated by successfully coating CeO2, SnO2 nanoparticles on carbon nanotubes, a simple and high efficient method of coating oxide nanoparticles on carbon nanotubes was developed.