Synthesis, characterization and formation mechanism of hexagonal prism polycrystalline γ-Al2O3
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摘要: 以AlCl3·6H2O为前驱物,在氨水介质中用水热法制备了具有新颖形貌特征的六棱柱状多晶γ-Al2O3颗粒。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)及N2物理吸脱附等方法对所制备的γ-Al2O3颗粒进行了表征,并对其形貌形成机制进行了分析。结果表明,铝前驱物在氨水介质中通过水热处理后,经焙烧可以形成形貌规整的六棱柱状γ-Al2O3颗粒,其边长与长度分别约为0.3 μm和2.5 μm。TEM图片显示,六棱柱颗粒是由尺寸在10 nm左右的粒子聚集而成,因而具有多晶γ相特征。所制备的γ-Al2O3材料具有发达的孔隙结构,比表面积为274 cm2/g,孔容为0.51 cm3/g,孔径集中分布在5.5 nm周围。研究发现,γ-Al2O3六棱柱形貌的形成机制与AlOOH二次粒子在NH4+正电荷作用下发生的最稳态排列形式具有密切的关联。Abstract: Novel hexagonal prism polycrystalline γ-Al2O3 particles were hydrothermally synthesized in ammonia medium by using AlCl3·6H2O as aluminum precursor. The γ-Al2O3 particles were characterized by means of XRD, SEM, TEM and nitrogen sorption measurements and the formation mechanism of crystal morphology was investigated. The results indicated that after the hydrothermal treatment of aluminum precursor in ammonia medium as well as the later calcination process, γ-Al2O3 particles with perfect hexagonal prism shape can be obtained; the border size and length of the hexagonal prism are about 0.3 and 2.5 μm, respectively. TEM images show that the hexagonal prism γ-Al2O3 particles are aggregated with fine particles of about 10 nm and then take the polycrystalline gamma phase. Such a γ-Al2O3 material exhibits a BET area of 274 cm2/g and pore volume of 0.51 cm3/g with a narrow pore size distribution centered at 5.5 nm. The results also suggest that the formation of the hexagonal prism γ-Al2O3 particles is closely related to the arrangement of the steady AlOOH precursors interacted with NH+4 ions.
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Key words:
- alumina /
- hexagonal prism /
- polycrystalline /
- morphology
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