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| Titel |
Changing shapes and implied viscosities of suspended submicron particles |
| VerfasserIn |
Y. Zhang, M. S. Sanchez, C. Douet, Y. Wang, A. P. Bateman, Z. Gong, M. Kuwata, L. Renbaum-Wolff, B. B. Sato, P. F. Liu, A. K. Bertram, F. M. Geiger, S. T. Martin |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1680-7316
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| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 15, no. 14 ; Nr. 15, no. 14 (2015-07-16), S.7819-7829 |
| Datensatznummer |
250119903
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| Publikation (Nr.) |
 copernicus.org/acp-15-7819-2015.pdf |
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| Zusammenfassung |
| The change in shape of atmospherically relevant organic particles is
used to estimate the viscosity of the particle material without the
need for removal from aerosol suspension. The dynamic shape factors
χ of particles produced by α-pinene ozonolysis in a flow
tube reactor, under conditions of particle coagulation, were
measured while altering the relative humidity (RH) downstream of the
flow tube. As relative humidity was increased, the results showed
that χ could change from 1.27 to 1.02, corresponding to a
transition from aspherical to nearly spherical shapes. The shape
change could occur at elevated RH because the organic material had
decreased viscosity and was therefore able to flow to form spherical
shapes, as favored by the minimization of surface area. Numerical
modeling was used to estimate the particle viscosity associated with
this flow. Based on particle diameter and RH exposure time, the
viscosity dropped from 10(8.7±2.0) to
10(7.0±2.0) Pa s (two sigma) for an increase in RH from
< 5 to 58 % at 293 K. These results imply that the
equilibration of the chemical composition of the particle phase with
the gas phase can shift from hours at mid-range RH to days at low
RH. |
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