Sol–gel transition study and pyrolysis of alumina-based gels prepared from alumatrane precursor

Abstract

Alumina gels were prepared by the sol-gel method using alumatrane or tris(alumatranyloxy-i-propyl)amine as precursor synthesised directly from the reaction of inexpensive and readily available compounds, aluminium hydroxide and triisopropanolamine (TIS), via the one step process. Sol-gel process parameters, such as gel time, were correlated to variables of the initial stage of the process, such as pH, temperature of hydrolysis and hydrolysis ratio. The sol-gel transition of alcoholic alumatrane solutions was monitored by multiple waveform rheological measurements. The gel time could be determined from the evolution of the storage (G ) and loss (G ) moduli versus time at different frequencies using the Winter Chambon criterion (convergence of the loss tangents at the gel point). Increasing pH values, hydrolysis ratio and/or temperature accelerated the kinetics of hydrolysis-condensation reactions and thus reduced the gel time. The apparent activation energy of the cross-linking leading to the gelation calculated from the gel times at various temperatures was found to be approximately 139 kJ mol −1 and independent of hydrolysis ratio. Alumina materials prepared from the heat treatment of obtained gel at 500 • C were analysed using X-ray diffraction and the BET method.

Activated alumina preparation and characterization: The review on recent advancement

“…Many researches had studied on methods for alumina regeneration due to the fact that regeneration is cheaper than replacement [20]. Furthermore, regeneration and reuse of alumina is also a practical way to reduce secondary pollution and conserve natural resources [19]. Generally, activated alumina behaves in much way like activated coal, which is a familiar adsorbent.…”

“…Activated alumina is a high-surface-area, highly porous form of aluminium oxide which recently attracted the attention of various researchers [19] . It can absorb gases and liquids without changing its form.…”

The characterization of ceramic alumina prepared by using additive glass beads

“…There are two general approaches to enhance sintering process or to lower the sintering temperature. The first is to improve powder processing, that is, to use fine starting powders and to eliminate agglomerates in the green pre forms such as by chemical routes [7].…”

“…The second approach is to use sintering aids or additives [7]. Additives in solid solutions can enhance diffusion and hence sintering by increasing defect, while additives forming a liquid phase can facilitate particle rearrangement and soIution / reprecipitation [8,9].…”

Fabrication of Ceramic Nanofibers Using Atrane Precursor

“…Chelating agents, such as acetylacetone, are sometimes added to control hydrolysis during the gelation process, and the reactions often are carried out in nitrogen atmosphere. The synthesis of novel precursor is necessary for the development of metal alkoxide chemistry and the investigation in sol-gel field (Charoenpinijkarn et al, 2001;Ksapabutr et al, 2004a;Ksapabutr et al, 2004b;Ksapabutr et al, 2005c). Generally, the atrane complexes are performed by means of trans-esterification reaction, using alkoxide derivatives in nonaqueous dried solvent under an inert atmosphere.…”