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Diffusion charger-based aerosol surface area monitor response to silver agglomerates with 2-D fractal dimensions ranging from 1.58 to 1.94.

Ku-BK; Maynard-A
Proceedings of the AAAR 23rd Annual Conference, October 4-8, 2004, Atlanta, Georgia. Mount Laurel, NJ: American Association for Aerosol Research, 2004 Oct; :221
The effect of particle morphology on a diffusion charger-based aerosol surface area monitor has been comprehensively investigated using the LQ1-DC diffusion charger (Matter Engineering, Switzerland). Silver particles sintered at various temperatures ranging from 20 oC (no sintering) to 700 oC were used to provide different particle shapes. With the exception of the 20 nm particles measured with the diffusion charger, the data response is fitted well with a power model of the form y=axb (where x is mobility diameter, y is normalized surface area and x is in the range from 20 to 100 nm), giving power b equal to almost 2. The deviation at 20 nm may be partly accounted for by the detection limit of the diffusion charger. For the diffusion charger response vs. particle sizes extended up to 200 nm, the power b decreases to 1.62 when instrument response to particles larger than 100 nm is included. The change in response appears to start at mobility diameter 80~90 nm. Fitting data above and below 80 nm indicates two distinct response regions, with data above 80 nm being described by a power law with an exponent of 1.5. Diffusion charger response to the agglomerates at temperatures not larger than 300 oC (complex shape) is slightly higher than those at temperatures above 500 oC (spherical), indicating that the attachment rate of charged ions in the diffusion charger to particles appears to depend slightly on particle morphology. It is hypothesized that complex shaped agglomerates entering the diffusion charger will have a lower charge-to-surface ratio than equivalent spherical particles, thus leading to a greater probability of multiple charging.
Aerosols; Surface-properties; Silver-compounds; Morphology; Aerosol-particles; Temperature-effects; Models; Particulates
National Institute for Occupational Safety and Health (NIOSH), 4676 Columbia Parkway, MS R-3, Cincinnati, OH 45226
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Proceedings of the AAAR 23rd Annual Conference, October 4-8, 2004, Atlanta, Georgia