Preparation And Thermal Decomposition Of Neodymium Neodymium Oxide Precursor

The rare earth elements are widely used in glass, ceramics, catalyst, magnetic and fluorescent materials due to the special electronic structures. The rare earth oxides with large particle size,uniform particle distribution and good morphology have shown good market prospect and attracted intensive attention along with the development of new material technology. In the previous work, a dual solvent system of P507-N235 was designed for rare earth extraction and the hydrochloric acid was subsequently selected to strip the loaded organic phase, which solve the ammonia-nitrogen pollution during saponification extraction process originally. With little impurities and high acidity, the stripping solution was suitable for the preparation of powder materials with large particle size because the high acidity can lower the precipitation rate and inhibit nucleation. Based on the above work, the Nd2O3 with large particle size was prepared by precipitating the neodymium trichloride stripping solution with oxalic acid, which realize the connection of non-saponification extraction-stripping-preparation of rare earth oxides with large particle size. The mechanism of precursor decomposed to Nd2O3 was further studied to provide theoretical basis for the practical reaction process. The main work and results are as follows:The precursor and Nd2O3 with large particle size was prepared by precipitating the neodymium trichloride stripping solution with oxalic acid. The results show that the particle size of precursor reaches larger than 75μm when the reaction temperature is 50 ℃, stirring velocity is 300 r/min, feeding speed of precipitant is 9 m L/min and aging time is 8 h;The particle size of the precursor can be improved by adding seeds. When the seed size is 45μm, seed amount is 9% and and aging time is 24 h, the particle size of precursor reaches larger than 90μm; The particle size of precursor is controllable in a certain range by changing the experimental parameters. The precursor decomposed completely to Nd2O3 calcined at 800℃ for 2 h., the Nd2O3 are formed by the aggregation of smaller particles, the Nd2O3 particles disperse well with the median size(D50) is larger than 50μm.The influence of reactant concentration, molar ratio of precipitant, reactant acidity and aging temperature on morphology of 10μm Nd2O3 was investigated. The results show that neodymium oxalate with particular morphology can be obtained by altering parameters to control supersaturation and aggregation of particles, further calcined to obtain Nd2O3 with homologous morphology. The Nd2O3 with good morphology and dispersion can be obtained when the reactant concentration is 0.12mol/L, the molar ratio of precipitant is 1.7:1, the reactant acidity is 2.5mol/L and the aging temperature is 45℃.The results of thermal decomposition of neodymium oxide and kinetics analysis show that the TG/DTG/DTA curves move to the high-temperature sides with the increasing of the heating rate. The higher the heating rate, the higher corresponding temperature to reach the same weight loss rate, the obviously higher weight loss rate of DTG curve with the maximum heating rate, the larger peak area of DTA curve and the higher absolute value of enthalpy under the same temperature. The activation energy values of anhydrous neodymium oxalate decomposed to Nd2O2CO3 is 130.10~187.8k J/mol and the reaction is in accordance with the three-dimensional diffusion model. The activation energy values of Nd2O2CO3 decomposed to Nd2O3 is 57.4~81.83 k J/mol.