BaCO3とTiO2の反応の速度論的研究

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The reaction between BaCO3 and TiO2 has been studied in air and in CO2 at 700-1020°C. Several products (Ba2TiO 4, BaTiO3, BaTi3O7, and BaTi4O9) were obtained when the mixtures of BaCO3 and TiO2 were heated in air, but, under the CO2 atmosphere of 300-700mm Hg, BaTiO3 with very small amounts of BaTi3O7 was observed. The kinetics of the reaction between BaCO3 and TiO2 under the CO2 atmosphere of 500mm Hg were studied. The process of the reaction is composed of two steps, i.e. a phase boundary reaction followed by a subsequent diffusion process. The kinetic data can be expressed reasonably by the first-order equation for the earlier stage, and by Tammans equation for the later one. The activation energy for the earlier stage of rutile is about 43Kcal/mol. There is a discontinuity at about 830°C in the plotting of log k against l/T for the earlier stage of anatase. The activation energies are about 34 and l6Kcal/mol above and below 830°C respectively. The activation energy for the later stage is about 34Kcal/mol for both anatase and rutile.
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