The Mobility and Structure of Aerosol Agglomerates

Abstract

The relation between the aerosol agglomerate structure and transition regime mobility can be explained with a simple model incorporating fractal geometry and results from computer simulations. The model is consistent with previous measurements of the shape factors and allows some structural information to be inferred from these measurements, although the data are insufficient for a rigorous comparison between theory and experiment. Experiments conducted here with well-characterized TiO₂ and Si agglomerates support the model' assumption that the mobility diameter of a particle in the free-molecule regime is determined solely by the projected area of the particle. The correlation between the projected area and the mobility equivalent size remains remarkably good throughout the transition regime for the agglomerate particles studied here. The model predicts this result for particles with fractal dimensions of approximately D _f = 2