SYNTHESIS OF ALUMINA BALLOONS USING A MIC ROCAPSULATION METHOD

The synthesis of alumina balloons using the microcapsulation method ha s been investigated, and was successful in producing a transparent bal loon with a diameter of 50-80 mu m and a wall thickness of less than 1 mu m. The process is as follows, 10 mass% solution of polystyrene in toluene and boehmite sols of approximately 1 mol/kg concentration are mixed by a homogenizer, The resultant W/O emulsion is redispersed in w ater to obtain a (W/O)W emulsion which produces boehmite sols encapsul ated by polystyrene in water. After keeping it for 2 days at 40 degree s C, the products are altered, dried and then the polystyrene crust is dissolved by toluene. The resultant balloon precursors of boehmite so ls are dried, fired and then the alumina balloons are obtained. In thi s paper, the effects of the concentration of polystyrene or boehmite s ols and the addition of ethylene glycol or tricresyl phosphate on the formation of alumina balloons were discussed in detail.