Micro and nano scale metal oxide hollow particles produced by spray precipitation in a liquid–liquid system

Microfabrication of Al2O3, TiO2 and ZrO2 hollow particles were carried out by spray precipitation that the fast polymerization is induced from dehydration or acid–base neutralization on the interface of the sprayed droplet to form rigid shell structure, and then removing the remained solvent within the shell. High yield of the smooth hollow particles can be achieved by selecting a highly polymeric precursor, which has higher surface tension, viscosity and density than those of the precipitation agent. In this work, micro to nano scaled Al2O3, TiO2, and ZrO2 hollow particles are obtained, respectively, by spraying their precursor solutions including: aluminum chlorohydrate, titanium chloride, and zirconly chloride into the precipitation agents including acetone, triethylamine and tributylamine. Subsequently, the remained water in the inner shell particles are allowed to vaporize carefully and calcinated. A bottle structure was demonstrated by increasing the momentum of sprayed droplets to impact with the precipitation agent.