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Comparison of diffusion charging and mobility-based methods for measurement of aerosol agglomerate surface area.

Authors
Ku-BK; Kulkarni-P
Source
J Aerosol Sci 2012 May; 47:100-110
NIOSHTIC No.
20040405
Abstract
We compare different approaches to measure surface area of aerosol agglomerates. The objective was to compare field methods, such as mobility and diffusion charging based approaches, with laboratory approach, such as Brunauer, Emmett, Teller (BET) method used for bulk powder samples. To allow intercomparison of various surface area measurements, we defined 'geometric surface area' of agglomerates (assuming agglomerates are made up of ideal spheres), and compared various surface area measurements to the geometric surface area. Four different approaches for measuring surface area of agglomerate particles in the size range of 60-350 nm were compared using (i) diffusion charging-based sensors from three different manufacturers, (ii) mobility diameter of an agglomerate, (iii) mobility diameter of an agglomerate assuming a linear chain morphology with uniform primary particle size, and (iv) surface area estimation based on tandem mobility-mass measurement and microscopy. Our results indicate that the tandem mobility-mass measurement, which can be applied directly to airborne particles unlike the BET method, agrees well with the BET method. It was also shown that the three diffusion charging-based surface area measurements of silver agglomerates were similar within a factor of 2 and were lower than those obtained from the tandem mobility-mass and microscopy method by a factor of 3-10 in the size range studied. Surface area estimated using the mobility diameter depended on the structure or morphology of the agglomerate with significant underestimation at high fractal dimensions approaching.
Keywords
Aerosols; Analytical-processes; Laboratory-techniques; Author Keywords: Diffusion charging; Aerosol surface area; Agglomerates; Tandem mobility-mass approach; Mobility diameter; BET method
Contact
Bon Ki Ku, Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), 4676 Columbia Parkway, MS-R3, Cincinnati, Ohio 45226, USA
CODEN
JALSB7
Publication Date
20120501
Document Type
Journal Article
Email Address
BKu@cdc.gov
Fiscal Year
2012
NTIS Accession No.
NTIS Price
Identifying No.
B03142012
Issue of Publication
1
ISSN
0021-8502
NIOSH Division
DART
Source Name
Journal of Aerosol Science
State
OH
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