Hydrothermal Synthesis, Characterization Of CeO₂ And Ceria-based Oxide Micro/nanomaterials

Ceria is a cheap and widely used industry material, which has a broad market applied prospect. Recently, the controls of morphology, size and applications of properties about CeO₂ nanomaterials have been the key issues. In this paper, ceria and ceria-based oxide nanomaterials were prepared by hydrothermal method, the preparation, characterization and optical properties of as-prepared nanomaterials have been studied. The main results achieved in this paper are listed as below:1. The bunchy, cubic, octahedral, short rod-like, discal CeO₂ precursor structures have been synthesized by hydrothermal method under different reagents, surfactants, reaction times and temperatures. The CeO₂ nanostructures were obtained after heat treatment at 500°C. (1) The different morphologies of CeO₂ nanomaterials were prepared in the presence of Ce(NO₃)₃6H₂O, urea and CTAB under different reagent concentrations, reaction temperatures and times. The morphology and particle size were controlled through reaction time, temperature and urea concentration. And the cause of controlling morphologies and particle sizes were discussed. The optical properties of CeO₂ nanoparticles with cubic and octahedron morphologies were investigated. (2) The discal CeO₂ nanoparticles have been prepared in the presence of CeCl₃7H₂O, urea, PVP and acetic acid at 180°C for 3h. The possible formation mechanism was discussed, and the optical properties of particles were also studied.2. The different morphologies of CeO₂-MOx (M=Cu, Si, Ti, Al, Zn, Fe, Co) nanocomposites precursors have been synthesized by a simple hydrothermal method. In these experiments, proper ratios of Ce(NO₃)₃6H₂O,CeCl₃7H₂O, urea, acetic acid and metallic oxide precursors were used. And after heat treatment, the metallic oxide nanocomposities were obtained. (1) The uniformed CeO₂-CuO nanowires were synthesized. The diameter of CeO₂-CuO nanowires was about 10-20nm, and the length was several micrometer. The HRTEM and SAED images showed that CuO nanoparticles were sticked on the surface of CeO₂ nanowires. The possible mechanism for the nanowires formation was supposed. The acetic acid is a key factor during the formation of nanowires. UV-vis absorption analyses revealed the nanowires have very strong absorption which of the absorption region is up to 800nm.(2) The other CeO₂-MOx (M= Si, Ti, Al, Zn, Fe, Co) nanocomposities were characterized by XRD, FESEM, UV-vis spectra. (3)α-Fe₂O₃ ordered hollow nanorod-arrays were synthesized. FESEM, TEM images showed that the morphology of nanorod top was square structure, and the morphology of bottom was acicular structure. The diameter of nanorods was about 20-30nm, and the length was about 60-70nm. HRTEM analyses supposed that the nanorods were grown along with [021]. UV property of CeO₂-Fe₂O₃ nanocomposite revealed that the UV sheliding effect was better than CeO₂-MOx (M= Si, Ti, Al, Zn, Co) nanocomposits.3. CeO₂@C and CeO₂-SiO₂@C nanocomposities have been synthesized by two-steps hydrothermal methods under certain reaction temperatures and times. The thickness of C layer can be controlled by adjusting the dosages of compositions and reaction times.