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Preparation, Characterization and Properties of Nano-sized Oxides of Rare Earth Using Ammonium Bicarbonate as Precipitant

Author: ZhangShaoYang
Tutor: DiYongQing
School: Hebei University
Course: Inorganic Chemistry
Keywords: Rare earth oxides Nanocrystalline Precipitation method Ammonium bicarbonate Dispersant Nature
CLC: TB383.1
Type: Master's thesis
Year: 2007
Downloads: 45
Quote: 1
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Abstract


The rare earth elements is a general term for the 17 elements of the periodic table of elements Sc, Y, and La-based. China's rare earth resources and production in the world's dominant. Preparation and Application of rare earth nanomaterials has become a hot topic in the current, because the set of rare earth characteristics of the material and nano-features in one is bound to open up the excellent characteristics of the non-rare earth nanomaterials and rare earth nanomaterials do not have a comprehensive. Nano-rare earth oxide is an important part of the rare earth nanomaterials, because of its special physical and chemical properties of the new material of the 21st century. Therefore, smaller particle size, uniform distribution of nano-rare earth oxides prepared to become an urgent need to study by more and more attention. At present, the state of matter of ultrafine powder preparation technology respectively by solid, liquid and gas phase. Nanometer rare earth oxides preparation process according to the domestic and foreign research progress, combined with the actual needs of the industrial production, precipitation is the more appropriate method, but industrial precipitation method for the production of rare earth oxides with oxalic acid as the precipitating agent, prepared rare earth oxides are the micron level. The main subject of study precipitation with ammonium bicarbonate Preparation of nanometer rare earth oxides, and by means of TG-DTA, XRD, IR, SEM, UV, fluorescence spectrophotometer, such as the composition of the precursor decomposition process, the formation process of the product, morphology, particle size and nature of a series of studies, as raw materials of the rare earth nitrates NH4HCO3 as precipitating agent, by controlling the reaction conditions, was prepared easy settlement, washing, filtration of the rare earth carbonate precursor, roasting can be obtained rare earth oxide nanocrystals, particle spherical shape and good dispersion. The method is low-cost, simple operation, the reaction process is easy to control, energy saving, easy to industrialization. The results also showed that: cerium carbonate precursor calcined at 400 ℃, that is obtained pure cubic crystal CeO2 nanocrystals. Addition of CeO2 nanocrystalline grain size increases with the calcination temperature and the type of dispersant also have a large impact on its morphology and dispersion, thereby CeO2 nanocrystal light absorption and photocatalytic activity big impact, the smaller the particle, the better the dispersibility of the higher photocatalytic activity, under suitable conditions, enables the decolorization rate of more than 97%. Lanthanum carbonate precursor can be prepared hexagonal crystal lanthanum oxide nanocrystalline calcined at 700 ℃, and to determine the lanthanum carbonate composition is: La2 (CO3) 3.3 .1 H20, decomposition reaction in two steps: La2 (CO3) 3 → La2O2CO3 → 2La2O3. The study also found that the dispersant types affect a La2O3 the morphology, La2O3 is a chemically unstable oxide will slowly absorb water in the air into La (OH) 3, after the high-temperature burning , can be changed back to the lanthanum oxide. Carbonate precursor of Gd (Eu), calcined at 700 ℃ cubic crystal system Gd2O3: Eu nanocrystalline pure phase, and to determine the composition of the carbonate precursor of Gd (Eu) RE2 (CO3) 3.2 .44 H2O decomposition process step, without intermediate product. Micron crystalline Gd2O3: Eu material, Gd2O3: Eu nanocrystalline XRD peaks broadened excitation spectrum of the red shift of about 10nm, the quenching concentration increased from 6% to 8%, reflects the nanomaterials small size effect and surface effect. Yttrium carbonate (Eu) precursor calcined at 600 ℃, that cubic crystal Y2O3: Eu nanocrystalline pure. Compared with the high-temperature solid-phase method, this Law, the synthesis of Y2O3: Eu nanocrystals of small particles, good dispersion and high luminous intensity. Calcination temperature and the addition of boric acid could significantly improve the luminous intensity of Y2O3: Eu nanocrystals. With the continuous increase of the europium content, the luminous intensity is enhanced weakened, the quenching phenomenon occurs when the europium content is 5%.

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