Study On The Preparation And Properties Of CeO₂Nanomaterials With Different Morphologies

Ceria (CeO2) is an important rare-earth product with wide applied prospect. Recent years,the controls of morphology, size and microstrucuture for CeO2nanomaterials have beenintensively investigated, and achieved plenty of positive results. In this dissertation,multi-morphology CeO2nanomaterials, such as paricles, rods and films, were synthesized byhydrothermal precipitation method under normal temperature and pressure. The effect factorsand formation mechanisms of the nanomaterials were also investigated using XRD, SEM, TEMand AFM. At the same time, the photocatalytic activity of these CeO2nanomaterials wasevaluated by degradating methyl orange under UV irradiation. In addition, an uvioresistant fabriccomposites were fabricated using a simple ammonia vapor deposition technique. The maincontents and results are described as follows:1. Not adding any surfactant, CeO2nanoparticles and nanorods were prepared by a verysimple hydrothermal method. CeO2nanoparticles and nanorods were successfully synthesizedjust by dropping ammonia into cerium nitrate (Ce(NO3)3·6H2O) water solution at roomtemperature. The synthesized nanoparticles are spherical with10~30nm in diameter and thenanorods are100~200nm in length and5~10nm in diameter.2. Without any surfactant and template, nanothick CeO2films were prepared by droppingcerium nitrate (Ce(NO3)3·6H2O) water solution into ammonia at room temperature. The resultsshow the products morphology strongly depends on the pH value of the starting solution. Thefilms with several square micrometers area and about a dozen nanometers in the thickness justcan be synthesized in strong alkali solution; the AFM image of ceria nanofilms clearlydemonstrates there are several remarkable step edges with3nanometers height.3. Above CeO2nanoparticles, nanorods and nanofilms showed good catalytic activity withmore than150m2/g in specific surface. Above CeO2nanoparticles, nanorods and nanofilmsshowed good catalytic activity, and the catalytic results demonstrate nanofilms show higher reactivity commpared with particles and rods owing to its special surface structure. For example,when degrade methyl orange with2g/L ceria nanofilms, the degradation rate of methylorangecan be up to98%. Hydroxyl radicals were successfully detected during the catalytic oxiditionexperiments, which dedicate that the catalytic mechanism is due to hydroxyl radicals generatedon the catalyst surface under UV irradiatoin.4. An uvioresistant fabric composites were fabricated by coating CeO2particles on thesurface of cotton or polyester fabric using a simple ammonia vapor deposition technique. Theresults show the fabric composites have good uvioresistant performance. After treatment, theultraviolet protection factor (UPF) of the cotton fabric composites significantly increases from8.71to298.26, while the transmittance of Ultraviolet A (UVA) value drops down from17.95%to2.11%. Moreover, the uvioresistant performance of the polyester fabric after treatment hasgreatly improved. Even after30times washings, the fabric composites still keep gooduvioresistant performance.