Preparation of Hollow Alumina Microspheres by Mechanofusion and Ultrasonic Spray Pyrolysis

摘要

Hollow alumina microspheres with various diameters were prepared by using mechanofusion and ultrasonic spray pyrolysis followed by calcination in air. Core/shell-type hybrid particles, polymethylmethacryrate (PMMA) microspheres (diameter (d): 10 μm) coated with a layer of α-Al{sub}2O{sub}3 powders (d: ca. 0.2 μm) containing 5wt%SiO{sub}2 fine powders (d: ca. 0.011μm), were easily prepared by utilizing the mechanofusion system. Hollowα-Al{sub}2O{sub}3 microspheres of 10-60μm in diameter were obtained by calcination of the core/shell microparticles at 1600°C for 3 h. On the other hand, hollow alumina microspheres of 0.1-5.0μm in diameter could be prepared by ultrasonic spray pyrolysis (frequency: 1.6 MHz) of an aqueous Al(NO{sub}3){sub}3 a solution by adjusting the flow rate of air as a carrier gas and the concentration of Al(NO{sub}3){sub}3. The hollow alumina microspheres as-obtained were metastableδ-Al{sub}2O{sub}3, but the post-calcination at 1300°C for 1 h in air transformed the product intoα-Al{sub}2O{sub}3. These two methods are promising for preparation of hollow ceramic microspheres.