Synthesis of nano – neodymium oxide by homogeneous precipitation method

Nano Nd_2O_3 powder material was prepared by homogeneous precipitation method. The preparation process, the kinetics of precipitation reaction and thermal decomposition reaction of precursor precipitate were studied. Other lanthanide elements (except promethium) and yttrium oxide were prepared. The main research contents and results are as follows: Nano Nd_2O_3 was prepared by uniform precipitation method by dissolving crude Nd_2O_3 in concentrated nitric acid (Nd(NO_3)_3) and urea as precipitator. The effects of the concentration of Nd~(3+), urea concentration, reaction temperature and time, drying temperature and time, calcination temperature and time on particle size of the product were investigated. The results show that the uniformly dispersed hexagonal crystal nano Nd_2O_3 particles can be obtained under the preliminary technological conditions. Taking the particle size of the product as the index, the concentration of Nd~(3+), the concentration of urea, reaction temperature and reaction time were selected to optimize the four factors by uniform experimental design method. It was found that the reaction temperature had the greatest influence on the particle size of the product, followed by reaction time, neodymium ion concentration and urea concentration. The optimum reaction conditions for the preparation of nano-nd_2O_3 by homogeneous precipitation method were determined as follows: the concentration of Neodymium ion was 0.24mol/L; Urea concentration was 2.27mol/L; The reaction temperature is 97.3℃. The reaction time was 3.41h. The drying temperature of precursor precipitate was 105℃. Drying time is 3 hours; Calcination temperature is 800℃; The calcination time is 3 hours. Under these conditions, the predicted value of Nd_2O_3 by computer program is 26.51nm, and the average particle size of Nd_2O_3 prepared by experiment is 30nm. According to the optimized conditions of uniform design, the oxide of lanthanide (except promethium) and yttrium were prepared by uniform precipitation method. The results show that except cerium, praseodymium and terbium, all the other elements prepared are +3 oxide Re_2O_3, and the particle size decreases with the increase of the atomic number of the lanthanide elements, which is consistent with the lanthanide shrinkage theory. The influence of ionic surfactants cetyltrimethylammonium bromide, sodium dodecyl sulfonate, non-ionic surfactants Tween 80, polyethylene glycol 6000 and polyvinyl alcohol 124 as dispersants on the particle size of the product was studied. The experimental results show that the surface tension and capillary force of particles are weakened due to the inherent properties of surfactants, which can inhibit agglomeration. The dispersing effect of anionic surfactants is not as good as that of cationic surfactants because of the negative charge of the precursor precipitate surface in the reaction system. Using non-ionic surfactant as polymer, the steric hindrance effect is produced after adsorbing on particle surface, so the better dispersion effect is obtained. The spherical Nd_2O_3 particles with an average particle size of 20nm with good dispersibility and distinct boundaries were obtained when the dosage of POLYETHYLENE glycol 6000 was 4mg/mL. The kinetics of uniform precipitation reaction was studied. The reaction order of neodymium ion is 1.62 and the activation energy of precipitation reaction Ea=83.25kJ/mol. Thermal decomposition of precursor precipitates was studied by thermogravimetric and differential thermal analysis. Reaction mechanism of thermal decomposition reaction in the first stage is F (a) _1 = [- ln (1 – alpha)] ~ (1 ╱ 2), the activation energy E_1 = 200.72 kJ/mol, referring to former factor A_1 = 5.08 x 10 ~ 8 _s ~ (1); The second stage of the reaction mechanism of F (a) _2 = (1 – a) ~ (1), the activation energy of E_2 = 187.66 kJ/mol, referring to former factor A_2 = 4.68 x 10 ~ 5 _s ~ (1).

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