Abstract
Micron-sized inorganic microparticles with hollow inside were prepared by interfacial reaction method, in which the ion exchange reaction between Na+ and metal cation dissolved in internal and external aqueous phases proceeded through oil phase involving a cation carrier. The diameter of microballoons was about 10 µm and shell thickness was below 2 µm. The effects of preparation conditions against the formation of microballoons were also examined. The factors examined were metal species in external aqueous phase, the concentrations of metal chloride and cation carrier. When the cross-section of resulting microparticles was measured by scanning electron microscope (SEM), the inner space of some metal silicates was not hollow but filled up. The increase of salt concentrations led to the increase of the diameter and shell thickness of microballoons. Since the penetration of metal cation through oil phase was promoted by the increase of carrier concentration, the formation of microballoons was possible in a short time less than 30 min.
