Emulsion–ion extraction technique for synthesis of hollow bicomponent oxide microspheres

Abstract

H ollow ox ide microspheres in the bicomponent systems Al₂O₃-28 wt-%SiO₂ (AS) ( mullite), Al₂O₃- 13 wt-%T iO₂ (AT), and Z rO₂-10 wt-%Y₂O₃ ( Z Y) were prepared by the emulsion-ion extraction technique. Monodisperse microsphere formation was found to depend on the experimental parameters adopted during ion ex traction and the surfactant concentration present in the emulsion system. Powder characteristics were investigated using X-ray diffraction, optical and scanning electron microscopy, and particle size analysis. The gel microspheres in the AS, AT, and ZY systems started crystallising at about 900, 800, and 400 °C respectively. The oxide microspheres were mostly spherical in morphology and the sphericity was retained even after calcination at 1300 °C for 1 h. Formation of hollow microspheres with a single spherical cavity was identified by SEM. All oxide microspheres calcined at 1300 °C for 1 h ex hibited a particle size distribution within the range 5-60 μm, the average size ( d₅₀) varying from 19 to 22 μm. BCT / 537