High specific surface area TEOS-based aerogels with large pore volume prepared at an ambient pressure

The experimental results on the synthesis of tetraethoxysilane (TEOS)-based silica aerogel with high specific surface area and large pore volume, via ambient pressure drying (APD) route, are reported. The silica aerogels were prepared by the acid‐base sol‐gel polymerization of TEOS precursor followed by the drying of the alcogels at an ambient pressure. The solvent present in the alcogel (i.e. ethanol) was replaced by a non-polar solvent such as hexane prior to the surface modification step. In order to minimize the drying shrinkage, the surface of the gels was modified using trimethylchlorosilane (TMCS) before the APD. The FTIR spectra of the surface modified aerogels showed Si‐CH3 peaks at 2965 and 850 cm � 1 . The effect of the base catalyst (NH4OH) addition to the sol, at different time intervals (T), on the physical and textural properties of the resulting aerogels has been investigated. It has been observed that the surface area and the cumulative pore volume of the aerogels enhanced considerably from 819to1108 m 2 g � 1 and 2.65to 4.7 cm 3 g � 1 , respectivelywith anincrease inthe Tvalue from 6to48 h.Silica aerogelswith very low bulk density (0.06 g cm � 3 ), extremely high specific surface area (1108 m 2 g � 1 ) and large cumulative pore volume (4.7 cm 3 g � 1 ) could be synthesized by drying the alcogels at the ambient pressure. The aerogels were mesoporous solids with the average pore size ranging from 12 to 17 nm.Theresultshave beendiscussed bytaking intoconsideration thehydrolysisand condensationreactions duringthesol‐gelpolymerization of the TEOS precursor. # 2007 Elsevier B.V. All rights reserved.