Measurement for Metallic Nanoparticle Agglomerates Generated from Spark-discharge using the Universal NanoParticle Analyzer (UNPA)

ZHUN LIU (1), Seong Chan Kim (1), Jing Wang (1), Heinz Fissan (2), David Y. H. Pui (1)

(1) University of Minnesota, (2) Institut für Energie- und Umwelttechnik eV (IUTA)

     Abstract Number: 150
     Last modified: April 25, 2010

Abstract
Nanoparticle agglomerate characterization and measurement is a popular area for recent aerosol research because most naturally occurring aerosols exist in agglomerate form rather than single spherical particle and many engineered aerosols (TiO2, SiO2) are agglomerates, because of the high concentration in the synthesis process.

We describe here an experimental system in which a recently developed instrument called Universal NanoParticle Analyzer (UNPA) (Wang et al., 2010) was used in the measurement of metallic nanoparticle agglomerates generated from spark-discharge and coagulated inside an agglomeration chamber. The UNPA sensitivity S, defined as S = I/N, where I is the current reading of NSAM internal electrometer and N is the concentration reading of CPC, was measured for particles of Au, Ag, and Ni. The particle morphology varies from loose agglomerate, to partly sintered aggregate, and sphere, which is controlled by a sintering furnace.

The primary particle sizes were evaluated from the sensitivity, and they agree reasonably well with those obtained by electron-microscopy. The capability of UNPA to provide fast online measurement of agglomerate structural properties makes it a useful tool in monitoring synthesis processes for engineered aerosols. Furthermore, the primary sizes were plugged into Lall’s model (Lall and Friedlander, 2006) to obtain agglomerate size distribution based on the raw size scanning result. It was found that raw scanning data can overestimate agglomerate volume concentration by about ten times. This shows another potential application of the instrument in agglomerate mass concentration measurement, e.g. diesel engine soot emission. Comparisons of UNPA measurement and filter sampling results are also being conducted in the ongoing research.