Fractal Dimension of Alumina Aggregates Grown in Two Dimensions

The concepts of fractal geometry are applied to the analysis of 0.4-μm alumina constrained to agglomerate in two dimensions. Particles were trapped at the bottom surface of a drop of a dilute suspension, and the agglomeration process was directly observed, using an inverted optical microscope. Photographs were digitized and analyzed, using three distinct approaches. The results indicate that the agglomerates are fractal, having a dimension of approximately 1.5, which agrees well with the predictions of the diffusion-limited cluster–cluster aggregation model.