Molecular modeling of carbon aerogels

Carbon aerogels are prepared via pyrolysis of resorcinol-formaldehyde gels. The structure consists of a highly porous three-dimensional network made u p of interconnected, roughly spherical carbon particles. The aerogel studie d in this work was mesoporous and had carbon particles having a diameter of approximate to 6 nm,connected in an open-cell structure with a porosity of approximate to 0.55. In addition to the mesopores between the carbon parti cles, the carbon particles themselves possess slit-shaped micropores with a width of approximate to 0.7 nm. We present a molecular model of this mater ial, consisting of carbon spheres of diameter 6 nm in a connected network. This matrix is prepared by first generating a random close-packed structure of slightly overlapping spheres, followed by random removal of spheres to match the targeted porosity. Structural characteristics of the model have b een studied using different MC techniques and compare well with those for t he laboratory material. Nitrogen adsorption in this model aerogel was studi ed using a parallelized Grand Canonical Monte Carlo algorithm based on a do main-decomposition scheme. Large systems are needed for this simulation in order to represent the pore network in a realistic fashion. Adsorption occu rs in the micropores at very low pressure, followed by adsorption in the me sopores, with capillary condensation occurring at the higher pressures. (C) 2001 Elsevier Science B.V. All rights reserved.