Study On The Preparration Process Of Cerium Dioxide Nano-Powder

Developing new kind of polishing nano-powder which has the advantages of low cost, satisfying fineness, high efficiency and long-life has great significance in improving product's competition ability at international market especially for cathode-ray tube and liquid crystal display device, owing to broad application-market and cheerful prospect of cerium-based polishing powder at home and abroad.In this thesis, employing liquid chemical precipitation method, the process of cerium dioxide nano-powder preparation is discussed sufficiently. Further studies focusing on process parameters in each step have been carried out with the experimental apparatus of spectrophotometer. X-ray diffraction (XRD), transmission electron microscope (TEM), thermogravimetric (TG) analysis and differential thermal analysis (Dl A). In experiments, particular emphasis is placed upon two problems: one is to dissolve the coarse cerium dioxide particles; the other is to control particle's measurement of cerium dioxide nano-powder. As a result, series of feasible process parameters are proposed for enlarged experiments and production stage.With proper dissolving process, which has been illustrated by studies, the coarse cerium dioxide particles can be dissolved over 90 percent: reaction temperature of dissolving is maintained 35℃~50℃, nitric acid concentration is 7~8.5mol/l, volume ratio between peroxide of hydrogen and nitric acid is 1:8, reaction time of dissolving is kept forone hour. According to the following parameters in preparation process which have been demonstrated by spectrophotometer experiments, the agglomeration of Ce(OH)4 is minority: concentration of Ce(NO3)3 and NH3-H2O are 0.15mol/l and 6.8mol/l respectively, volume ratios between NH3-H2O and Ce(NO3)3, ethanol and ethylene, total alcohol and Ce(NO3)3 solution are 1:10,1:1 and 1:10 respectively, reaction temperature is 20℃.TEM and XRD results indicate that reasonable baking parameters of Ce(OH)4 are 100℃ for 5~6h, sintering parameters are 250℃ to 350 ℃ or500℃ to700℃ for 2-2.5h which correspond to less than 20nm nano-grain or 30~40nm critical nano-grain. Analysis of TEM illustrates the cerium dioxide nano-powder has a uniform measurement and regular spherical shape prepared with process above. With XRD analysis, it can be concluded that non-integrated crystal morphology samples can be prepared below the temperature of 250癈, while over 350℃ is multi-crystal nano-powder. Crystal grain size measured by TEM photos accords substantially with the size calculated by XRD experiment.Experiments of thermal analysis show the reaction of Ce(OH)4 transforms to CeQz performs step by step, during which CeO(OH)2 is formed and complete transformation from Ce(OH)4 to CeOa starts at240 ℃.