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Rapid Synthesis Of Rare Earth Halides In A Microwave Field

Posted on:2004-03-05Degree:MasterType:Thesis
Country:ChinaCandidate:X F ZhangFull Text:PDF
GTID:2121360095457768Subject:Inorganic Chemistry
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Rare earth halides. are widely used in many fields, such as in petroleum company, glass, metallurgy, breed aquatics industry and so on . Meanwhile, it is very useful in carbon arc stick luminescence, iron, addiction in colored metals and manufacture of rare earth metals, etc. In recent years, rare earth halides are of very importance in preparation of new electron-resource material, fluoride. IR fluorescent powder, etc.When it comes to the preparation of rare earth halides, there are three conventional methods in the synthesis of anhydrous rare earth fluoride, i.e. produce REF:, precipitation in solution by the reaction between rare earth oxides and HF acid . then dehydrate the rare earth halides under vacuum: reaction between rare earth oxides and HF gas ; Reaction between rare earth oxides and ammonium bifluoride (NH4HF2). Three prototypes of methods were applied in preparing anhydrous rare earth chlorides hydrates, and halogenation of rare earth oxides, and reaction between rare earth refined ore and chlorine at high temperature with C. But in the above conventional methods in preparing rare earth halides, the toxic, erode gas such as HF. HCl and Cl2 are often used, which do great harm to people, and pollute environment seriously. They have many shortcomings, such as it is difficult to operate and energy-wasting, and need very long treatment time.Recently . microwave technology has been widely used in almost every chemistry research fields due to its particular heating character. Compared with conventional heating means, heating in microwave field, the material will produce internal heating due to the medium consumption in itself, thuswill produce internal heating due to the medium consumption in itself, thus the temperature of this material will rise rapidly in very short time, which can avoid the abnormal growth of crystal particle during the process of synthesis. A kind of pure, small, equally distributed material can be manufactured in microwave field. But when the power are off, the products can cool rapidly in the environment with lower temperature, which because the microwave ovens cannot radiate heat itself, thus it can improve the surrounding and conditions of labor.It is possible to rapidly synthesize the material with high purity, nanometer-sizes, high activation, which can make good use of the reactors and reduce pollution. In this paper, rare earth fluorides and cerium chloride are successfully prepared in air in a domestic microwave oven for the first time.Firstly, the reactors between rare earth oxides and ammonium fluoride(NH4F) were intimately mixed, the mixture was put into an alumina crucible and covered with absorbent of microwave radiation and was fired with 400W for 15-20min. All rare earth fluorides and rare earth fluoride oxides and rare earth fluoride double salts can be successfully obtained. The constitute and structure of the samples are observed by XRD, TG-DTG and FE-SEM. The mechanism of these reactions are discussed roughly, and the effect of microwave radiation in the process of rare earth fluorides are studied.Secondly, the cerium(â…¢) chloride and cerium(â…¢) double salt were synthesized by the oxidation-reduction reaction between CeO2 and NH2OH-HCl, NH4C1 respectively in microwave radiation field with 400W for 20-30min. The constitute and structure of the samples are observed by XRD, TG-DTG and FE-SEM. The mechanism of these reactions are discussed roughly. In this thesis, the problems of different materials havedifferent absorbing capacity for absorbing microwave radiation and different absorbent of microwave radiation will affect the reaction also are studied roughly.Above all , in comparison with the conventional heating methods, rapid synthesis of rare earth halide in a microwave field exhibits interesting features, such as the microwave treatment time is very short, material-saving, and it is simple ,easy to operate, efficient and energy-saving .
Keywords/Search Tags:Microwave radiation systhesis, Rare earth oxides, Rare earth fluorides, Rare earth fluoride oxides, Rare earth fluoride double salts, Cerium(Ⅲ) chloride, Cerium (Ⅲ) chloride double salt, Nanometer-sizes, Oxidation -Reduction
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