10th International Aerosol Conference September 2 - September 7, 2018 America's Center Convention Complex St. Louis, Missouri, USA
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Using Electron Tomography to Better Characterize the Fractal Morphology of Aerosol Aggregates
CHENCHONG ZHANG, Pai Liu, William Heinson, Qing Li, Jingkun Jiang, Rajan K. Chakrabarty, Washington University in St. Louis
Abstract Number: 1626 Working Group: Aerosol Physics
Abstract Freshly emitted soot particles normally demonstrate complex fractal-like morphologies which could significantly influence atmospheric radiative forcing and aerosol-cloud interaction. An accurate parameterization of the morphology of these particles is an essential prerequisite for evaluating their role in global radiative forcing. However, retrieving the complete morphological information in 3-dimension (3-d) remains a challenging task due to information loss incurred during image processing of projected electron microscopy images of soot. As a result, the currently adopted morphological descriptors for soot commonly assume the monomers to be point-contacted and equally-sized spheres, which deviate considerably from their true morphology especially when considering their unevenly coated surfaces and sintering. Here, we demonstrate a novel 3-d reconstruction algorithm for soot aggregates using the electron tomography technique. Particle tomograms, retrieved from a tilt-series of transmission electron images, were used to generate 3-d geometric models of soot aggregates after proper rescaling. Our methodology precisely captures the detailed morphological information of the particles, for example, the exact shapes of primary particles and degree of sintering. We calculated the structure factor of the reconstructed models by performing Fourier transform of the voxel density autocorrelation function. We compare the structure factors of our 3-d reconstructed model with those of aggregates simulated using the classical 3-d off-lattice diffusion limited cluster-cluster aggregation technique. We anticipate our findings to improve upon the morphological descriptors of soot and fractal-like aggregates produced from various combustion processes.