Fine Powder Processing of Alkoxide Method by Using Three-Phase Reactor

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The alkoxide method is used to prepare alkaline-earth perovskite ceramics with complex compositions. In this study, a novel process of fine powder production named as "three-phase alkoxide method" has been developed, which is the precipitation in a three-phase bubble column by injecting steam gas. The morphology of particles formed from the hydrolysis of titanium tetraisopropoxide and the reaction mechanism have been studied. The relationship between the particle size and the operation conditions was investigated.In conclusion:1) The increase of steam feed rate in the three-phase alkoxide method promotes hydrolysis reaction and raises the yield of the products.2) An additional supply of steam promotes particle growth without the secondary nucleation, leading to narrow particle size distribution.3) The rapid hydrolysis of alkoxide is caused by the additional injecting of steam. The subsequent condensation reaction between Ti-OH groups takes place, leading to the formation of a highly cross-linked Ti-O network and he particle growth.4) In addition, a structural model for predicting axial solid concentration profile in three- phase reactors is presented. The solid concentration in the wake is a controlling factor for determining axial solid concentration profiles.