R. Saliger et al., CARBON AEROGELS FROM DILUTE CATALYSIS OF RESORCINOL WITH FORMALDEHYDE, Journal of non-crystalline solids, 221(2-3), 1997, pp. 144-150
Aqueous polycondensation of resorcinol with formaldehyde leads to orga
nic gels the structure of which can be controlled by the reaction para
meters. The amount of catalyst controls the size of the particles cons
tituting the gel network. We could show that for very low catalyst con
centrations in a high dilution of reactants, the particle growth can b
e further enhanced if the reaction temperature is kept low, and the ge
l time is prolonged. The resultant structure is largely affected by th
is treatment, producing particles with sizes of about 2 mu m and avera
ge pore sizes of up to 7 mu m Due to these coarse structures it is pos
sible to dry these RF gels subcritically with very little shrinkage. T
he structure has been studied by nitrogen sorption, small angle X-ray
scattering and acoustic sound propagation. The change of the elastic m
odulus caused by pyrolysis at around 1000 degrees C has been investiga
ted. Mechanical properties of carbon aerogels are correlated with thei
r electrical properties. The derived carbon aerogels have large specif
ic surface areas, very little mesopore volume however, micron-sized ma
cropores. (C) 1997 Elsevier Science B.V.