Synthesis of Alumina Aerogels by Ambient Drying Method and Control of Their Structures

Abstract

A new method to synthesize alumina aerogels was introduced in this article. Alumina aerogels were firstly prepared by sol-gel process, using Al(β) inorganic compound as a precursor, 1,2-epoxy propane as a gelation inducing agent (GIA) and methane amide as drying control chemical additive (DCCA), followed by ambient drying method (ADM). The bulk alumina aerogels were examined by TEM, SEM and BET method, which have similar qualities to those prepared by supercritical fluid drying method (SCFM). Propane oxide was introduced to accelerate the gelation rate of Al(β) ions and improve the homogeneity of pore distributions of aerogels, formamide as drying control chemical additive (DCCA) to improve the homogeneity of oxide particles in the gel texture. Alumina gels were aged and reinforced through a solvent exchanging of alcohol, the immersing of tetraethyl orthosilicate (TEOS)/alcohol and absolute alcohol at a certain temperature. The aged gels were dried at the ambient pressure and the bulk alumina aerogels with high surface areas and higher porosity were obtained. On the base of the relationship of the variation of alumina aerogels, structures with molar ratio of propylene oxide/Al, the structure of alumina aerogels can be controlled by adjusting molar ratio of propylene oxide/Al.