Figures & data
Figure 1. Aggregate morphology evolution with increasing coating thickness. Simulated aggregates are shown in (b), (d), and (f). These aggregates closely mimic real-world soot aggregates (a), (c), and (e) from China et al. (Citation2013). (a) and (b) are bare soot aggregate with point contacting monomers and an open morphology (Df = 1.8). Partially coated aggregates are shown in (c) and (d). Thickly coated or embedded aggregates are displayed in (e) and (f). Although the aggregates in (c) through (f) have had voids filled with coating and thus appear to be compact, their mass continues to scale with Df = 1.8 as shown in .
Figure 2. Scaling of coated aggregate mass with size. (a) Bare simulated aggregates exhibit Df = 1.8 and k0 = 1.35. The partially coated (b) and embedded (c) aggregates both exhibit Df = 1.8 with k0 = 3.40 and k0 = 6.98, respectively. These plots show that Df is invariant with increasing coating mass. Coating affects k0, which controls the shape anisotropy and monomer packing density of an aggregate.
Figure 3. Structure factor S(q) of bare and coated aggregates. Aggregates were simulated in the range N = 30–4000. In (a), the S(q) of bare simulated aggregates show a Df = 1.8 for q−1 < a; beyond this size, S(q) exhibits a power-law exponent of −4 which is characteristic of a spherical three-dimensional monomer. For the partially coated (b) and embedded (c) aggregates, the crossover from −1.8 to −4 moves to smaller q values due to the increase in effective monomer size with coating. The key point to note in these plots is the existence of the −1.8 slope for even the extremely coated (embedded) aggregates.
Figure 4. Scaling relationships for fractal prefactor k0 with coating mass and a’. (a) The ratio of total aggregate to bare aggregate mass Mtotal/Mbare scales with prefactor k0 and follows the relationship k0 = 1.34(Mtotal/Mbare)0.56. (b) The effective monomer radius a’ scales with prefactor k0 and follows the relationship k0 = 1.34(a’/a)1.70.
