The Preparation Of Nanometer Barium Carbonate By Solid-state Reaction At Room Temperature

Barium carbonate is an important material for electronic, architectural, metallurgical and chemical industry. Because nanometer barium carbonate has more excellent qualities than ordinary barium carbonate, it has been one of the important directions of the barium carbonate industry. In this thesis the solid-state reaction at room temperature was applied to prepare nanometer barium carbonate. The feasibility of this method was studied and an optimized procedure for the preparation of nanometer barium carbonate was set up. Its content includes:For solid-state reaction system of Ba(NO3)2 and Na2CO3 at room temperature, those factors which might influence the solid-state reaction, including the molar ratio of reactants grinding time heat treatment and adding sequence of the reactants, were inspected. Of them, the adding sequence has the most important influence on the reaction. The XRD K-value method was used to quantitatively analyze the productivity at different reaction times. The solid-state reaction mechanism at room temperature was preliminarily discussed. It was postulated that the diffusion of the substances might be the rate-determining step for the solid state reaction.For BaCl2 2H2O and Na2CO3, Ba(NO3)2 and NH4HCO3 systems, the molar ratio of reactants, grinding time and heat treatment et al. were discussed. The results showed that both two systems react easily once grinding at the room temperature. At the same experiment conditions, changing the ratio of the reactants led to completely different results for these two systems. After heat treatment, the products of the Ba(NO3)2 and NH4HCO3 system would react sequentially, and heat treatment is therefore considered unfavorable for the production of BaCO3.The products were characterized by X-ray diffraction (XRD) and transmissionelectron microscope (TEM). The results showed that spherical BaCO3 particles with low reaggregation and uniform size of about 100nm could be prepared by using solid-state reaction of Ba(NO3)2 and Na2CO3 at room temperature; while stick shape particles, whose size is not uniform, were obtained for the BaCl2 2H2O and Na2CO3 system. For the Ba(NO3)2 and NH4HCO3 system, the products are spherical whose average size is about 200nm. XRD results showed that the products from these three systems are of the same structure.For comparison, ordinary aqueous precipitation method was used to prepare barium carbonate by using Ba(NO3)2 and NH4HCO3 as the reactants. The influences of adding sequence of the reactants and surfactant et al. on the products were discussed. Compared to the solid-state reaction system at room temperature, the shape and particle size of the products were not uniform.It is seen from the experiment that the new method of solid-state reaction at room temperature is simple and environmentally friendly. Its characteristics, such as high yield, little pollution, low cost, no need of solvent, and low tendency of reaggregation (compared to the aqueous solution reaction), are very much promising for industrialization.