Microscopic Structure Control for Composite Fine Particles by Using Microscopic Reaction Field

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W/O/W emulsion (emulsion liquid membrane; ELM) system has been used for separation and concentration of metal ions. In this study, the ELM system was utilized for preparation of fine particles, aiming to control their size and morphology, by using the micrometer-sized internal water droplets as size-restricted reaction area. The interface between the organic membrane phase and the internal water phase gives hydrophobia reaction sites for the) particles formation, and template effect for particle formation may be expected.1. Preparation of Calcium Phosphate Particles Calcium ions were transported from the external water phase into the internal water phase through the organic membrane phase, and well-defined spherical, micrometer-sized phosphate particles were obtained, mainly consist of calcium hydroxyapatite, by the reaction with phosphate anions in the internal phase. Alumina-containing β-TCP (calcium triphosphate) spherical particles were also prepared, by the addition of aluminum ions in the internal phase, and by the calcination of the resulting composite phosphate particles.2. Preparation of Phosphor Fine Particles Rare earth ions are transported into the internal phase and oxalate particles were prepared. When both Y and Eu ions were transported, composite Y-Eu oxalate particles were obtained, which give Y_2O_3:Eu^<3+> particles. The size of the oxide particles could be controlled by changing the ELM system employed. The Y_2O_3:Eu^<3+> particles showed red emission by excitation with UV light.