Influence of hydrothermal conditions on the phase transformations of amorphous alumina

Abstract

Monophasic amorphous alumina was obtained by heat treating in muffle furnace at 550 ?С during 2 h (heating rate 5 ?С/min). Precursor of amorphous alumina was the product of aluminum isopropoxide hydrolysis by water vapor and included )90 wt% of amorphous hydroxide. Polyaluminoxanes, stabilized in aluminum monohydroxide (boehmite), and amorphous aluminum hydroxide were formed during hydrolysis of aluminum alkoxides. Amorphous aluminum hydroxide was transformed into amorphous alumina after heat treatment at T (550 ?С, aluminoxanes and boehmite were converted analogously to γ-Al2O3