CARBON AEROGELS FROM DILUTE CATALYSIS OF RESORCINOL WITH FORMALDEHYDE

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.