Acetic-acid-catalyzed and subcritically dried carbon aerogels with a nanometer-sized structure and a wide density range

Organic acids used as catalysts allow for the preparation of resorcinol-formaldehyde (RF) and carbon aerogels without any metallic impurities. In this paper we present RF aerogels originating from an aqueous gelation and subcritical drying after the exchange of the pore water against acetone. In contrast to earlier attempts, very high catalyst concentrations of the weak acetic acid were used. The samples exhibit a wide density range from 200 to 1400 kg m(-3) and pores sized in the nanometer range. For conventional concentrations of the acetic-acid catalyst, we only obtain nanostructured subcritically dried aerogels with densities >600 kg m(-3). For an accurate characterization of the nanostructure, scanning electron microscopy (SEM), small-angle X-ray scattering (SAXS and USAXS) and gas sorption were employed. (C) 2004 Elsevier B.V. All rights reserved.