Preparation Of CeO₂ Nanometer Powers By Precipitation Method

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, nanopaticle has become one of the quite popular problem in materials research field, it gains much attention of the scientist from different countries in the world.CeO2 is a cheap and of use wide light rare earth oxide material. After it becomes nanoparticle,it will show some new properties and applications like other inorganic naoparticles.However.at present, because there aren't is no sophisticated approaches and technologies that limit its development, the preparation of the CeO2 nanoparticles still stays the experimental stage. In conclusion, it is important to synthesize and application CeO2 nanoparticles because of its extensive use.This paper has reviewed the resources of CeO2 in our country, the markets and the condition of application. The advantages and drawbacks of the important preparation methods were reviewed. It puts emphasis on the reaction mechanism of precipitation method to nanoparticals and analyzes redox potential between Ce3+ and Ce4+, puts forward a new technics named "a two-stage precipitation process" to succeed in obtaining nanocrystalline powers of cerium oxide.The main contents of this dissertation are summarized as follows.(l)By investigating and preparing the CeO2 nanoparticles with various precipitators we choosed the cerium(III) nitrate, hydrogen peroxide and ammonia as the materials to prepared the nanoparticles by a two-stage precipitation method The process differents from the generalprecipitation process. The first stage is that Ce3+ is oxidized by hydrogen peroxide, and the second is that Ce4+ is precipitated by ammonium hydroxide.(2)The affecting factors such as components in precipitation process, the add-on, add on of precipitator, calination temperature and calination time were studied in the preparation process of CeO2 nanoparticles. The TG was used to analyze the processor, the XRD, SEM and TEM were used to characterize the size of crystal type of products. By a series of designed experiments the interaction between different factors and impacts on the preparation of CeO2 nanoparticles were probed, and the optimum preparation condition was gotten. The small particle sizes of lOnm and well dispersivity of CeO2 nanoparticles were gotten.(3)The Mechanism model of forming rigid agglomeration agglomeration and elimination methods were investigated, which are the critical problem in the preparation of ultrafine partical during liquid-phase process. The methods were employed such as the distributing agent PVA of macromolecule and changing the drying method to improving the dispersivity of CeO2 nanoparticles and overcome the problem of agglomeration.(4)The ultraviolet absorption character of CeO2 nanoparticles prepared in experiment and CeO2 microparticals sold in the market were analyzed and contrasted by ultraviolet radiation-visible light photometer. The investigation indicates that CeO2 nanoparticles prepared in experiment has the good ultraviolet absorption property. However, it is not found that CeO2 nanoparticles were employed at light degradation catalysis aspect. It is preliminary studied the ultraviolet absorption character of CeO2 nanoparticles were used for degrading helianthine with the help of the 721-type spectrophotometer.