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

Novel superstructures of multilayered Al2O3 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 Al2O3 microfibers with mesoporous structures are obtained by the thermal decomposition AACH precursor at 1173 K. SEM images show that the average diameter of Al2O3 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 Al2O3 microfibers. The N2 adsorption–desorption experiment show that the as-synthesized alumina microfibers have large surface area (ca. 358 m2/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.