Preparation of hollow alumina microspheres by microwave-induced plasma pyrolysis of atomized precursor solution

Hollow alumina microspheres have been prepared by microwave- induced (MI) plasma pyrolysis of atomized aerosols of precursor solutions and subsequent calcination at 1300 degrees C for 2 h. When an aqueous solution of 0.5 mol dm(-3) Al(NO3)(3) without any additives was used as a precursor, hollow alpha-Al2O3 microspheres with a thick shell wall were prepared after post-calcination at 1300 degrees C. The addition of a polypropylene (PO)-polyethylene(EO) blockcopolymer (molecular weight: 2900-6500) to the precursor solution was effective for increasing the yield of hollow microspheres, but resulted in the formation of many cracks and holes in the thinned shell wall. Hollow alumina microspheres with a thin, but strong, shell layer could be prepared by the simultaneous addition of tetraethylorthosilicate. (c) 2004 Elsevier Ltd. All rights reserved.