MORPHOLOGICAL CHARACTERIZATION OF MICROCELLULAR CARBON FOAMS

Microcellular carbon foams have been prepared by the high-temperature carbonization of polyacrylonitrile (PAN) foams in an inert atmosphere. The PAN precursor foams were first prepared by thermally induced phase separation of PAN solutions followed by gelation/extraction or freezing/freeze-drying processes. The resulting carbon foams have low densities and open-celled morphologies. We have developed two complementary techniques to characterize objectively carbon foam morphologies, BET surface area measurements and mercury porosimetry. These two measurement techniques, when used in conjunction with known stereological rules, allow us to calculate densities and average cell sizes or cell size distributions. As a bonus, values of the bulk modulus for low-density carbon foams also can be determined from mercury porosimetry. Unlike other techniques, our determinations do not require carefully prepared surfaces (such as for microscopy) or an assumed morphological model (required for most other techniques).