Facile Preparation of Al2O3 Hollow Microspheres Via a Urea-mediated Precipitation Process

Abstract

Al2O3 hollow microspheres without noticeable aggregation have been prepared via a facile templating route with urea-mediated precipitation. The precipitation process is different from the surface-adsorption method which is confined to the adsorption capacity of the template surface. TEM and SEM images indicate that most of these Al2O3 hollow microspheres with shell thickness of tens of nanometers and diameters in a narrow range of 100–200 nm consist of a shell of closely packed nanoparticles. The optimal amount of H2O and EtOH are 40 and 120 mL, respectively. The specific surface area, average pore size and pore volume of the Al2O3 hollow microspheres (calcinated at 600 °C) are 328.52 m2/g, 17.496 nm and 1.985 cm3/g, respectively. As the calcination temperature increases from 600 to 1 100 °C, the phase composition changes from γ-Al2O3 to θ-Al2O3 and α-Al2O3, and the surface morphology appears to change from a relatively rough surface formed by nanoparticles to a smooth surface formed by lamellar, which lead to the closure of pore channels and the reduction of specific surface.