Morphological characterization of fumed silica aggregates

Transmission electron microscopy has been used to evaluate the primary particle size distributions and aggregate structure of a fumed silica sample. The primary particle size distribution within an individual aggregate is narrow, with a geometric standard deviation of ̃1.2. The distributions of maximum diameters, projected areas, and average primary particle diameters were all skewed, and all were better described by a log-normal distribution than a normal distribution. The data confirmed the fractal description of the fumed silica aggregate structure, with a mass fractal dimension of 1.86. The fractal prefactor or lacunarity was evaluated from the aggregate volume and the maximum particle dimension, and found to have a value of 0.83 for this sample.