AAAR 32nd Annual Conference
September 30 - October 4, 2013
Oregon Convention Center
Portland, Oregon, USA
Abstract View
Online Characterization of Nanoparticle Growth during Flame Aerosol Synthesis
ARTO GROEHN, Sotiris E. Pratsinis, Karsten Wegner, ETH Zurich
Abstract Number: 352 Working Group: Instrumentation and Methods
Abstract A method for online characterization of nanoparticle growth in aerosol reactors is presented. By combining a differential mobility analyzer (DMA), an aerosol particle mass analyzer (APM) and a condensation particle counter (CPC) the average agglomerate size and structure as well as the number and size of primary particles can be determined [1, 2]. Here, this approach was applied to study agglomerate growth during production of zirconia nanoparticles by flame spray pyrolysis at rate of 30 g/h [3].
Nanoparticles were sampled from the reactor plume at temperatures up to 1500 K and particle concentrations up to 10$^(18) /m$^3, with a probe allowing continuous aerosol extraction and rapid dilution with quench air that effectively suppressed coagulation. Primary particle growth was shown to be completed at 75 mm above burner as a constant primary particle diameter was observed for all radial and downstream axial positions. Such homogeneity indicates well mixed conditions in the high temperature region of the flame where sintering takes place. As expected, the average agglomerate size was found to increase with axial distance from the burner. However, larger agglomerates were observed at the fringes of the aerosol plume attributed to prolonged residence time due to lower gas velocity there. Results were compared against off-line particle size characterization by nitrogen adsorption and thermophoretic sampling/transmission electron microscopy as well as model predictions [3].
The detailed spatial characterization of particle growth helps to better understand and optimize the flame aerosol process. Furthermore, such real-time particle diagnostics can assist control of nanoparticle manufacturing processes and assure product quality.
[1] Park, K., Cao, F., Kittelson, D.B., McMurry, P.H. (2003), Environ. Sci. Technol. 37, 577.
[2] Eggersdorfer, M.L., Gröhn, A.J., Sorensen, C.M., McMurry, P.H., Pratsinis, S.E. (2012), J. Colloid. Interface Sci. 387, 12.
[3] Gröhn, A.J., Pratsinis, S.E., Wegner, K. (2012), Chem. Eng. J. 191, 491.