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.

Keywords

Al₂O₃ hollow microspheres / precipitation / nanoparticles / specific surface area

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