Synthesis Of Nano Cerium Dioxide Related Materials And Investigation Of Their Properties

Cerium is an important rare earth metal, and is richly contained in the earth. Ceria is a cheap and widely used material, which has been applied in the areas of luminous material, UV absorption material, catalyst, polishing, election ceramics, and so on. Recent years, with the development of nanotechnology and new rare earth materials, it is found that nano ceria powder have some novel properties and applications. So the research of synthesize, functional properties and application of nano ceria materials is an interesting subject.In this study, we developed a novel simple method composite-hydroxide-mediated (CHM) route to synthesize ceria nanoparticles, carbon nanotubes coated with ceria nanoparticles and Ba doped ceria nanowire. This method only requires low synthesis temperature and pressure, which is beneficial for mass-production with low costs.The ceria nanoparticles synthesized though CHM method are characterized by XRD, TEM, HRTEM and UV-vis analysis. The diameter of the nanopaticles is found to be very small, about 2-8 nm. We discover strong agglomeration of the nanoparticles, which induce the abnormal XRD pattern.The carbon nanotubes pretreated by nitric acid are coated with ceria nanoparticles. The products are characterized by XRD, SEM, UV-vis and FTIR analysis. We find that carbon nanotubes of perfect graphite structure can be hardly deposited with ceria nanoparticles. But when carbon nanotubes are pretreated by nitric acid, the graphite structure is partially destroyed with connecting hydroxyl and carboxyl on their surface. These functional groups work as active centers and make ceria nanoparticles deposit on the carbon nanotubes. So the surface modification of carbon nanotubes is very important for the coating of carbon nanotubes by ceria nanoparticles.Ba-doped ceria nanowires are synthesized by CHM method. Characterized by XRD, SEM, TEM, and HRTEM, the nanowires are found to have the typical fluorite structure, single crystal, and the length of 3-20μm. The growth direction of the nanowies is [110], and a'dissolution- crystallization'model is proposed to explain the growth mechanism. The film electrode composed with Ba-doped ceria nanowires has an excellent humidity property, the resistance change sharply with the humidity. The response time and recover time of the humidity sensor are found to be 1 minute and 2 minute, respectively. The mechanism of humidity sensitivity is explained by the ion conductance model.The Ba-doped nanowire as building block contrusts a single nanowire FET with the help of Focused Ion Beam technology. The I-V curve of a single Ba-doped ceria nanowire is measured. The I-V curve is found to have a nonlinear behavior, which is explained by the metal- semiconductor contacting effect.