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Interactive use of Electron Microscopy and Light Scattering as Diagnostics for Pyrogenic Aggregates

Published online by Cambridge University Press:  15 February 2011

Richard A. Dobbins
Richard A. Dobbins*
Affiliation:
Division of Engineering, Brown University, Providence, RI 02912
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Abstract

Both electron microscopy and light scattering have played an important role in elucidating the processes of inception, growth, and oxidation of carbonaceous particles in flames. The techniques developed have application to the various pyrogenic materials including the metallic oxides, carbides, etc. Thermophoretic sampling has been developed to afford efficient extraction of particle samples from hot reaction zones. The sampling procedure preserves the particle morphology for subsequent analysis by transmission electron microscopy (TEM). Studies using this technique have shown aggregate structures with fractal dimensions of 1.6 to 1.8, a result that is consistent with the computer simulations of the cluster-cluster aggregation process. Diverse morphologies, including microparticles found in the particle inception zone, reveal the evolution of these aggregates. The optical cross sections for polydisperse aggregates which are used to interpret the laser scattering/extinction tests (LSE) are described. Population averaged properties - volume fraction, volume mean diameter, monomer and aggregate number concentrations, mean-square radius of gyration - are derived. The interactive use TEM and LSE data leads to a global description of the aggregate dynamic processes which are found to be regionally partitioned within the laminar hydrocarbon diffusion flame.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 250: Symposium R – Chemical Vapor Deposition of Refractory Metals and Ceramics II , 1991 , 101
Copyright
Copyright © Materials Research Society 1992

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