Nanostructured Gamma Alumina from Amorphous Precursors
نویسنده
چکیده
Introduction Nanocrystalline gamma-phase (γ) alumina is among many polytypes of alumina that find extensive applications as a catalyst and catalytic supports. The most useful properties these aluminas provide as catalyst supports are high surface area and welldefined porosity. These properties result primarily from the nano-scale crystalline character of the alumina. The problem is that both the alumina precursor phase type and the thermal history have pronounced effects on the gamma structural transformations. Thus, precise control over the gamma transformation is a key to understanding many of the mysteries associated with this material in catalytic processes (1). We will clearly demonstrate that very significant atomic rearrangements take place at relatively low temperatures in the gamma-alumina amorphous precursors that affect both the gamma structure, and the ultimate transition to the thermodynamically stable alpha phase.
منابع مشابه
Controlled Synthesis of Alumina Nanopowders Using Supercritical Fluids for Ceramics Applications
Alumina is the most widely used oxide ceramic material. It exists in many metastable forms which lead upon severe thermal treatment towards the thermodynamically stable phase alpha. Sintering of alumina generally takes part in a minimum of two stages: i) phase transition(s) towards the stable phase alpha and ii) densification of this phase alpha. The former step(s), linked to transition phase(s...
متن کاملAn investigation on the effect of alumina on hydrothermal stability of nanostructured silica membrane prepared by sol-gel method
In the present study, the effect of alumina on the pore structure and hydrothermal stability of nanostructured silica was investigated. SiO2 and SiO2-15wt%Al2O3 membranes were prepared by dip coating on mesoporous γ-Al2O3 coated macroporous α-alumina support. The particle sizes of sol were increased by adding of alumina to silica...
متن کاملAbatement of Benzyl Alcohol and Methyl Ethyl Ketone (MEK) from Polluted Air Over Nanostructured Mn -Supported Alumina Catalyst
متن کامل
The effect of cobalt addition on the meso-porous structured γ-Alumina synthesized by aqueous sol-gel method
In the present study, the gamma alumina (γ-Al2O3) nano powders have been prepared with addition of 1%mol Co using an aqueous sol-gel method at lower temperature than the pure gamma alumina. The synthesis process accomplished by partial hydrolysis of the aqueous solution of metallic ions Al3+ and Co2+, with ammonia. The Al(NO3)3.9H2O and Co(NO3)2.6H2O salts were used as cations sources. The obta...
متن کاملMorphology investigation of alumina nano-powders prepared by a sol-gel combustion method
Highly sinterable alumina nano-powders have been synthesized by a sol-gel combustion method with glycine asfuel. The preparation involved the thermal decomposition of a chelating agent (fuel)-nitrate gel and theformation of amorphous precursors. The nanopowders calcined at 1100°C were characterized by X-ray powderdiffraction (XRD) and Scanning Electron Microscopy (SEM). It was found that the ch...
متن کامل