STRUCTURE OF CARBON AEROGELS NEAR THE GELATION LIMIT OF THE RESORCINOL-FORMALDEHYDE PRECURSOR

Resorcinol-formaldehyde (RF) gels with a very high molar ratio of reso rcinol/catalyst (R/C), e.g., 1500 and a low relative molar mass conten t of resorcinol + formaldehyde (RF-ratio) of about 30% can be ambient pressure dried with minimal shrinkage. The resulting RF-aerogels exhib it average cluster and pore sizes > 50 nm. Upon pyrolysis the RF-aerog els are transformed into carbon aerogels exhibiting the same morpholog y of the gel network but in addition showing a high amount of micropor osity (< 2 nm). Below an RF-ratio of thirty mass percent the average p article and pore size increase to several hundred nanometers. The macr o- and microscopic properties of these aerogels were investigated by s canning electron microscopy, permeability measurements, small angle X- ray scattering and CO, sorption. (C) 1998 Elsevier Science B.V. All ri ghts reserved.