Morphology Control of ZnO Particles

－ Effectiveness of Mixing Control of Reactive Gasses in CVD Process －

Abstract

ZnO particles formed via the oxidation of Zn vapor in air have various morphologies, such as sphere, tetrapod and needle. It is difficult to control their shape and size by the gas-phase CVD process. In the present work, we applied a flow restrictor to change the local mixing state between Zn vapor and oxygen so as to control the spatial formation rate of ZnO monomers. As a result we found that a simple device of flow restrictor is effective for producing ZnO embryos in the core stream of ZnO and subsequent growth of embryos to form tetrapod-shaped ZnO by the condensation of ZnO monomers onto the embryos. The effectiveness of flow restrictor for the formation of tetrapod-shaped ZnO was confirmed by solving the distribution of reaction rate of Zn vapor in air by using a CFD simulation.