STRUCTURAL STUDIES OF VAPOR-PHASE AGGREGATES VIA MERCURY POROSIMETRY

The physical structure (i.e., primary particle size, cluster fractal dimension) of a series of vapor-phase aggregates (fumed silica, carbon black) has been studied using mercury porosimetry. By employing an isostatic pressing technique, intrusion at low pressure is shown to be the result of cluster compaction for a range of Cab-O-Sil fumed silica and two carbon black samples. Analysis of the intrusion/compaction curve indicates fractal behavior with a D value of 2.5-2.6. Primary particle sizes determined via porosimetry support the theory that the nitrogen surface areas of fumed silica samples differ as a result of both particle size and surface roughness variation. The ratio of the mercury porosimetry-derived primary particle size to that determined from nitrogen adsorption was found to correlate with the surface fractal dimension as determined from scattering for both carbon black and fumed silica. © 1990.