Figure 3.

Overview of aerosol growth by coagulation and sintering showing the evolution of primary particle (PP) diameter, d_p (blue solid line), and agglomerate collision diameter, d_c (blue dashed line), with a typical temperature profile (red dash-dot line) (127) along with the relative magnitude of the characteristic times of coagulation, τ_c, and sintering, τ_s. The evolution can be divided into three stages: full coalescence (τ_c >> γ_s), aggregation (τ_c ~ τ_s), and agglomeration (τ_c << τ_s); the first and second stages determine the PP and average aggregate sizes, whereas the second and third stages determine the agglomerate size (64). The length of the middle stage (τ_c ~ τ_s) determines if agglomerates of aggregates (top, upper path) or of spherical particles (top, lower path) are formed---in other words, the extent of aggregate formation and hard bonding between PPs (d_cH/d_pH). For d_cH/d_pH → 1, few, if any, aggregates are formed.