title: Size-controlled synthesis of monodispersed mesoporous α-alumina spheres by a template-free forced hydrolysis method.
abstract: We demonstrated the formation of monodispersed spherical aluminum hydrous oxide precursors with tunable sizes by controlling the variables of a forced hydrolysis method. The particle sizes of aluminum hydrous oxide precursors were strongly dependent on the molar ratio of the Al(3+) reactants (sulfates and nitrates). In addition, the systematic phase and morphological evolutions from aluminum hydrous oxide to γ-alumina (Al(2)O(3)) and finally to α-Al(2)O(3) through thermal dehydrogenation were characterized by X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), and transmission electron microscopy (TEM). After annealing the amorphous aluminum hydrous oxide in air at 900 °C and 1100 °C for 1 h, we observed complete conversion to phase-pure γ- and α-Al(2)O(3), respectively, while maintaining monodispersity (125 nm, 195 nm, 320 nm, and 430 nm diameters were observed). Furthermore, both γ- and α-Al(2)O(3) were found to be mesoporous in structure, providing enhanced specific surface areas of 102 and 76 m(2) g(-1), respectively, based on the Brunauer-Emmett-Teller (BET) measurement.
authors.affiliation: Department of Materials Science & Engineering, Seoul National University, Shillim-dong, San 56-1, Gwanak-gu, Seoul 151-744, Korea.
authors.forename: Hee-Suk
authors.initials: HS
authors.lastname: Roh
authors.forename: Geun Kyu
authors.initials: GK
authors.lastname: Choi
authors.forename: Jae-Sul
authors.initials: JS
authors.lastname: An
authors.forename: Chin Moo
authors.initials: CM
authors.lastname: Cho
authors.forename: Dong Hoe
authors.initials: DH
authors.lastname: Kim
authors.forename: Ik Jae
authors.initials: IJ
authors.lastname: Park
authors.forename: Tae Hoon
authors.initials: TH
authors.lastname: Noh
authors.forename: Dong-Wan
authors.initials: DW
authors.lastname: Kim
authors.forename: Kug Sun
authors.initials: KS
authors.lastname: Hong