Structural Investigation of Resorcinol Formaldehyde and Carbon Aerogels Using SAXS and BET

The structure of organic RF aerogels (RF (=) over cap Recorcinol Formaldehyde) and carbon aerogels, their pyrolized counterparts, can be modified upon variation of the resorcinol to catalyst (RC) ratio. RF aerogels with RC ratios between 100 and 1500 have been produced in steps of 100. The densities for the organic aerogels were kept in the range of 350 to 390 kg m(-3): After pyrolysis, these samples have nearly the same density as their RF precursors, except the ones with very low RC ratios. This is due to the combined shrinkage and mass loss during the heat treatment. All samples were investigated using small angle X-ray scattering (SAXS) and nitrogen sorption (BET) as well as transmission electron microscopy (TEM). Two main effects have been observed. On the one hand, the particle/pore diameter distribution widens with increasing RC ratio, i.e., decreasing catalyst concentration. The average pore diameter increases from 20 nm to about 100 nm. On the other hand the pyrolysis generates a considerable amount of micropores in the particles.