PEG-directed hydrothermal synthesis of multilayered alumina microfibers with mesoporous structures

Abstract

Novel superstructures of multilayered Al 2O 3 microfibers with mesoporous structures are successfully synthesized from a hydrothermal preparation and thermal decomposition of a layered precursor of ammonium aluminum carbonate hydroxide (denoted as AACH). Nanolayer-based AACH microfibers are self-assembled by the hydrothermal process by using aluminum nitrate nonahydrate and urea as the starting materials. The corresponding multilayered Al 2O 3 microfibers with mesoporous structures are obtained by the thermal decomposition AACH precursor at 1173 K. SEM images show that the average diameter of Al 2O 3 microfibers is about 300–500 nm, and the length is around 5–10 μm. Studies also show that well-crystallized pores are embedded in the multilayer of the Al 2O 3 microfibers. The N 2 adsorption–desorption experiment show that the as-synthesized alumina microfibers have large surface area (ca. 358 m 2/g) and narrow pore-size distributions. A plausible layer-by-layer self-assembly mechanism using in situ formed AACH microfibers as the precursor for this multilayered alumina microfibers is also proposed.