The Fabrication And Characterization Of Ceria-based Nanomaterials

Ceria was widely used in catalys is, solid-state oxide fuel cells, functiona l ceramics,ultraviolet absorbent. The structure, size and morphology of the ceria nanomaterials arecrucial for its effic ient applications. Controlling of the morphology of the ceria hasbecome a key issue in the scientific area. In this thesis, a simple hydrotherma l methodwas employed to synthesize the ceria nanostructures by adjusting the sort and amount ofthe precipitant and the temperature. The main results achieved in this t hesis are list asfollows:（1） The fabrication of one-dime nsiona l ceria nanostructures:â‘ The Ce（OH）₃nanotubes with hexagona l cross-section were fabricated by a simp le hydrothermal us ingCeCl₃as the cerium source, hexamine as the precipitant and PVP as the surface activeagent. After being calc ined, ceria nanotubes with hexa gonal cross-section were obtained.The time-dependent experiments reveal that the nanotubes were derived from thenanoprisms and the dissolved oxygen plays an important role in the fabrication of theceria nanotubes.â‘¡The ceria nanorods were fabricated by adjusting the concentration ofCeCl₃, ethylened iamine, and PVP. The formation process of the nanorods was deducedby the time-dependent experiments.（2） The fabrication of the two-dimens iona l ceria nanostructures: A nanosheetstructure of CeO₂with30-50nm in thickness and about a feature size of300nm in thelateral direction has been obtained via controlling the morphology of CeOHCO₃precursors by a facile hydrothermal technique. The dependences of morphologies andphase transitions of CeOHCO₃precursors on reaction time, chemical compositions aresystematica lly investigated. Results show that the precursors exhib it one-dime nsiona lnanowire morphology with an orthorhombic crystal structure when the reaction time isless than3hours, and two-dimens ional nanosheet with a hexa gonal crystal structurewhen the reaction time is longer than9hours. The detailed transition process is recordedby snapshots of products between3and9hours. Experimenta l results reveal that theamount of acetic acid is a key parameter for the nucleation and crystal growth of CeOHCO₃nanosheets. A defect driven dissolving and recrystallization mechanism isproposed for the phase and morphology transition behavior of the precursors. The CeO₂nanosheet is obtained after thermal decomposition of the precursors. Compared to thenanodisk, the CeO₂nanosheet shows a blue shift in the UV-Vis absorption spectra due tothe quantum confinement effect. We fabricated La doped CeOHCO₃nanosheets. Afterbeing calc ined, the La doped CeO2nanosheets were obtained.