Accelerating the synthesis of carbon aerogel precursors

We have systematically modified the synthesis process for resorcinol and formaldehyde (RF) aerogels in order to reduce the time necessary for production of carbon aerogels. Firstly, the synthesis step that starts with mixing a solution of resorcinol and formaldehyde at relatively high resorcinol-to-catalyst, R/C, ratios (1000-3000) was modified by varying the gelation/aging temperature and time. Secondly, the progress of solvent exchange (acetone for water) in the RF backbone of the gels was investigated at subcritical conditions and the effect of the pore liquid upon subcritical drying on the pore structure was studied. All RF aerogel samples were characterized using nitrogen sorption. We find that reducing the process time for gelation/aging from three days (1 day at 22degreesC, 1 day at 50degreesC, and 1 day at 90degreesC) to 24 h at a gelation/aging temperature of 90degreesC generally results in slightly smaller structures (i.e., particle and pore sizes) as compared to the three day cycle. Such changes can be compensated for if the R/C ratio is increased accordingly. (C) 2004 Elsevier B.V. All rights reserved.