Numerical characterization of the morphology of aggregated particles

The structures of both cluster}cluster and particle}cluster fractal-like aggregates were investigated in the present study. Statistically signi"cant populations of numerically simulated aggregates having appropriate fractal properties and prescribed number of primary particles per aggregate were generated in order to characterize three-dimensional morphological properties of aggregates, such as fractal dimension, fractal pre-factor, coordination number distribution function, and distribution of angles between triplets. E!ects of aggregation mechanisms (i.e., cluster}cluster or particle}cluster) and aggregate size were taken into consideration. In addition, the morphological properties of aggregates undergoing partial sintering and restructuring were also investigated. To ful"ll these objectives, aggregates were initially built without considering sintering or restructuring e!ects. Partial sintering of primary particles was then considered by introducing a penetration coe$cient that allows touching particles to approach each other. Restructuring of aggregates was modeled during the process of building the cluster}cluster aggregates. For each pair of clusters that were attached together due to the normal aggregation procedure, a further mechanism was included that allowed the cluster to collapse until a more compact and stable position was achieved. The population studied was composed of ca. 450 simulated aggregates having a number of primary particles per aggregate between 8 and 1024. Calculations were performed for aggregates having a penetration coe$cient in the range of 0}0.25 with and without restructuring. The following properties were investigated: fractal dimension, fractal pre-factor, coordination number distribution function, angle between triplets, and aggregate radius of gyration. ( 2001 Elsevier Science Ltd. All rights reserved.