Synthesis And Characterization Of Ceria Nanoparticles

Nano-materials synthesis is one of the hot research topics recently. Because of its many particular properties in optics, acoustics, electricity, magnetism, heat, catalysis, mechanics chemical activity etc, and its great potential high technology applied prospects, nanotechnology gains much attention of the scientist from different countries in the world. CeO₂ and CeO₂-based nano-powders have been applied widely in the fields of high technology, such as superconductor, ceram, three-way catalyst, oxygen sensors, UV absorbent, glass-polishing material and electrolytes and electrodes in solid oxide fuel cells (SOFCs). However, at present, there are no sophisticated approaches and technologies, and the preparation and application of CeO₂ nanoparticles are still at its laboratory scale stage. In conclusion, it is important to synthesize and apply CeO₂ nanoparticles.The main contents and results of this dissertation are summarized as follows.(1) Cerium (III) nitrate and ammonia were chosen as the materials to prepare the CeO₂ nanoparticles via ammonia direct precipitation, precipitation with glycol or glycerol as dispersants, respectively. TG, XRD and nitrogen adsorption and desorption were used to characterize precursors of CeCO₂ and CeO₂ products. The results showed that nanosized CeO₂ powder prepared by precipitation with glycerol as dispersant had smaller crystalline size (7.6 nm) and higher BET area (79.3 m²/g). The possible reason is that glycerol molecular has more hydroxyls which could complex with Ce³⁺ strongly, slow down the speed of precipitation and prevent the particles from aggregating and growing up.(2)Glycol, glycerol and sorbitol were adopted as fuels in CeO₂ synthesis. Glycerol and sorbitol were used as new fuels to CeO₂ synthesis in this paper. Sorbitol is found to the best fuel, and the possible reason is more hydroxyls and longer carbon chains of sorbitol molecular could complex with Ce³⁺ strongly and prevent the particles from growing up and aggregating effectively.(3)The crystallinesize and BET area of CeO₂ could be controlled through fuel-to-nitrate ratio and pH value of the solution. The crystalline size and BET area of CeO₂ powder were 16.4～5.1 nm and 36.3～74.1 m²/g, respectively. Moreover, the particle size of CeO₂ powder was homogeneous.(3) As a fuel of low-temperature combustion to form CeO₂, the necessary condition is that the organic compound could complex with Ce³⁺ in a suitable intensity.