Cluster-cluster aggregation kinetics and primary particle growth of soot nanoparticles in flame by light scattering and numerical simulations (Articolo in rivista)

Type
Label
  • Cluster-cluster aggregation kinetics and primary particle growth of soot nanoparticles in flame by light scattering and numerical simulations (Articolo in rivista) (literal)
Anno
  • 2002-01-01T00:00:00+01:00 (literal)
Alternative label
  • di Stasio S. 1, Konstandopoulos A.G. 2, Kostoglou M. 2 (2002)
    Cluster-cluster aggregation kinetics and primary particle growth of soot nanoparticles in flame by light scattering and numerical simulations
    in Journal of colloid and interface science (Print)
    (literal)
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  • di Stasio S. 1, Konstandopoulos A.G. 2, Kostoglou M. 2 (literal)
Pagina inizio
  • 422 (literal)
Pagina fine
  • 432 (literal)
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  • Paper frutto di cooperazione internazionale fra CNR-IM e Centro greco di Ricerca sugli Aerosol CERTH-CPERI. (literal)
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  • 73 (literal)
Rivista
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  • La paper descrive la cinetica dei processi di formazione di aggregati e di crescita superficiale delle particelle primarie costituenti gli stessi, studiati \"in situ\" in fiamma con tecniche di static light scattering. La parte sperimentale fornisce l'evidenza di un processo di aggregazione caratterizzato da un kernel costante e ne rileva la costante di tempo caratteristica. Inoltre, viene valutata la rate di crescita superficiale delle particelle primarie. Le simulazioni numeriche consentono di ottenere previsioni in accordo con i dati sperimentali, e, in particolare, di caratterizzare sia l'evoluzione delle dimensioni delle particelle primarie a partire dalla condensazione di specie idrocarburo sulla superficie dei nuclei, sia l'evoluzione della dimensione frattale degli aggregati di nerofumo. Tuttavia lo schema adottato nelle simulazioni non e' in grado di spiegare il processo di restructuring subito in fiamma da parte degli aggregati stessi. (literal)
Note
  • ISI Web of Science (WOS) (literal)
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  • 1) Istituto Motori, CNR, Napoli, Italy; 2) CERTH/CPERI Thermi Thessaloniki, Greece. (literal)
Titolo
  • Cluster-cluster aggregation kinetics and primary particle growth of soot nanoparticles in flame by light scattering and numerical simulations (literal)
Abstract
  • The agglomeration kinetics of growing soot generated in a diffusion atmospheric flame are here studied in-situ by light scattering technique to infer cluster morphology and size (fractal dimension Df and radius of gyration Rg). SEM analysis is used as a standard reference to obtain primary particle size Dp at different residence times. The number Np of primary particles per aggregate and the number concentration n_A of clusters are evaluated on the basis of the measured angular patterns of the scattered light intensity. The major finding is that the kinetics of the coagulation process that yields to the formation of chain-like aggregates by soot primary particles (size 10 to 40 nm), can be described with a constant coagulation kernel beta_c,exp=2.37×10^-9 cm^3/s (coagulation constant 0.28 ms). This result is in nice accord with the Smoluchowski coagulation equation in the free molecular regime, and, vice versa, it is in contrast with previous studies conducted by invasive (ex-situ) techniques, which claimed the evidence in flames of coagulation rates much larger than the kinetic theory predictions. Thereafter, a number of numerical simulations is implemented to compare with the experimental results on primary particle growth rate and on the process of aggregate re-shaping that is observed by light scattering at later residence times. The restructuring process is conjectured to occur, for not well understood reasons, as a direct consequence of the atomic rearrangement in the solid phase carbon due to the prolonged residence time within the flame. Thus, on one side, it is shown that the numerical simulations of primary size history compare well with the values of primary size from SEM experiment with a growth rate constant of primary diameter about 1 nm/ms. On the other side, the evolution of aggregate morphology is found to be predictable by the numerical simulations when the onset of a first-order \"thermal\" restructuring mechanism is assumed to occur in the flame at about 20 ms residence time leading to aggregates with an asymptotic fractal dimension Df~2.5. (literal)
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