REALISTIC COMPUTER-MODELS OF AEROGELS

This paper describes methods employed to make realistic models of neutral- acid- and base-catalyzed silica aerogels and carbonized resorcinol-formaldehyde aerogels for use in studies of transport and material properties. The objective was to produce models consistent with experimental data including scattering data, microphotographs, and density measurements. To attain this goal, aggregation techniques were used that have not been previously associated with the chemistry of neutral- and acid-catalyzed silica. The appropriateness of these techniques is argued but not addressed rigorously. The methods are unified in a single code with control parameters that allow the user to create a complete range of geometries. Characterization of the computer models is done both by calculation of the scattering function and by visualization, methods that compare directly with experimental data. The computer program embodies a combination of diffusion-limited cluster-cluster aggregation and multi-site, multi-particle diffusion-limited aggregation.