Preparation of Hollow Alumina Microspheres by Ultrasonic Spray Pyrolysis

Abstract

Alumina microspheres have been prepared by spray pyrolysis of Al(NO₃)₃ aqueous solutions by adjusting the flow rate of air as a carrier gas and the concentration of Al(NO₃)₃. A mixture of hollow α-Al₂O₃ microspheres in the range of 200-700 nm in diameter and solid microparticles of smaller size were prepared by pyrolysis of 0.5mol·dm^-3 Al(NO₃)₃ at 1300°C and subsequent calcination at 1300°C for 1h in air. The use of Al(NO₃)₃ aqueous solutions at concentrations higher than 0.5 mol·dm^-3 resulted in the formation of sponge-like α-Al₂O₃ microspheres containing many closed pores.