The role of dipole interactions in coagulation of silicon agglomerates (Articolo in rivista)

Type
Label
  • The role of dipole interactions in coagulation of silicon agglomerates (Articolo in rivista) (literal)
Anno
  • 2000-01-01T00:00:00+01:00 (literal)
Alternative label
  • A. A. Onischuk 1, S. di Stasio 2, A. I. Levykin 1, V. P. Strunin 1, V. V. Karasev 1, K. K. Sabelfeld 3, V. N. Panfilov 1 (2000)
    The role of dipole interactions in coagulation of silicon agglomerates
    in Journal of aerosol science
    (literal)
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  • A. A. Onischuk 1, S. di Stasio 2, A. I. Levykin 1, V. P. Strunin 1, V. V. Karasev 1, K. K. Sabelfeld 3, V. N. Panfilov 1 (literal)
Pagina inizio
  • S950 (literal)
Pagina fine
  • S951 (literal)
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  • 31 (literal)
Rivista
Note
  • ISI Web of Science (WOS) (literal)
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  • 1) Institute of Chemical Kinetics and Combustion, SB-RAS, Novosibirsk, Russia; 2) Istituto Motori, CNR, Napoli, Italy; 3) Dipartimento di Matematica, Università di Berlino, Germany. (literal)
Titolo
  • The role of dipole interactions in coagulation of silicon agglomerates (literal)
Abstract
  • The interest of the scientific community about the agglomeration of aerosol nanoparticles is strongly motivated by the direct implications of this process on the synthesis mechanisms of very different particulate matter, such as soot, silica, titania. In this paper we carry out both experimental and numerical investigation of agglomeration occurring between silicon particles. Aerosol particles are formed by silane pyrolysis in a flow reactor and the coagulation mechanism is observed in the cold downstream zone. Reactor temperature is 873 K, residence time in the reactor is t=0.5 s and cold zone coagulation time is in the range 0.1 to 200 s. Agglomerate shape and size are analyzed by a Transmission Electron Microscope (TEM). An imaging system is used to observe in real time agglomerate sticking to each other. A primary He-Ne laser beam is passed inside the measurement volume which is fdled by the aerosol. A CCD camera and an optical microscope collect the light scattered by the agglomerates at 90° and images are transferred to a TV Recorder. Sensitivity of the image system with regard to aggregate shape is about 3 ¼m. An example of two agglomerates sticking to each other is shown in Fig. 1. The distance between agglomerates vs. time is reported in Fig. 2. The approaching velocity of agglomerates is increasing with time, and, in particular, some attractive interaction force between agglomerates is observed. This evidence is consistent with the fact that the agglomerates, which deposit onto the surface of the tube through which aerosol is passing, do form chain-like tendrils. Fig. 3 illustrates against time the process of sticking between an aggregate and a tendril attached to the tube surface. Fig. 4 reports the distance between the agglomerate and the tendril as a function of time. Also in this case the velocity of the agglomerate approaching the tendril is increasing with time, i.e., some attractive interaction force is present. The investigation of the agglomerate behavior in homogeneous and inhomogeneous electric fields furnish evidence that agglomerates are dipoles with a net charge equal to zero. The evaluated dipole moment is about 10-13 (units of CGSE) for agglomerates sized 0.3 mm. While it seems quite reasonable to assume that the dipole interaction does effect the aggregate shape, by contrast, it is a point of further investigation both the spatial range and the amount of the interaction effects and the rate of coagulation between aggregates. In order to light this question numerical simulations of coagulation process are carried out by assuming that there was no interaction between sticking agglomerates. Coagulation growth is modeled by a system of differential equations which is solved by a sectional algorithm. The initial conditions in the calculation are the agglomerate concentration and size spectrum, both measured in correspondence of the reactor exit. (literal)
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