Abstract:

Nano-alumina powders were prepared by vacuum freeze drying combined with reverse microemulsion method. The reverse microemulsion system consisted of cyclohexane/polyethylene glycol octylphenyl ether (Triton X-100)-hexadecyl trimethyl ammonium bromide (CTAB)/n-butylalcohol/water. The morphology, structure, specific surface area, pore volume, and pore size of the alumina nanoparticles were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and specific surface area analysis. The specific surface area of the alumina nanoparticles was about 550.0 m2·g-1 (changed with different reaction parameters) and the crystal structure was γ-Al2O3. The particle size was very uniform and smaller than 10.0 nm. The influence of different drying methods (normal hot-gas drying, normal vacuumdrying, vacuumfreeze drying) and the main parameters of vacuum freeze drying on the physical properties of the product were studied. Results showed that the nano-alumina powders obtained by vacuum freeze drying had much higher specific surface area and pore volume than that obtained by the two other drying methods. The specific surface area and pore structure of the nano-alumina were affected by the freezing rate, pre-freezing time, and drying time in the vacuumfreeze drying process.

Key words: Vacuumfreeze-drying, Reverse microemulsion, Nano-Al2O3, Specific surface area, Pore volume