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Modeling of the Formation of Boron Carbide Particles in an Aerosol Flow Reactor

Published online by Cambridge University Press:  25 February 2011

Yun Xiong ,
Sotiris E. Pratsinis  and
W. Weimer
Yun Xiong
Affiliation:
Center for Aerosol Processes, Department of Chemical Engineering, University of Cincinnati, Cincinnati, OH 45221
Sotiris E. Pratsinis
Affiliation:
Center for Aerosol Processes, Department of Chemical Engineering, University of Cincinnati, Cincinnati, OH 45221
W. Weimer
Affiliation:
Ceramics and Advanced Materials Research, Dow Chemical U.S.A., Midland, MI 48674
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Abstract

The formation of submicron crystals of boron carbide (B4C) by rapid carbothermal reduction of intimately mixed carbon-boron oxide precursor powders in an aerosol flow reactor at temperatures above the boiling point of boron oxide is investigated. The employed high heating rates (105 K/s) of the process force release of gaseous boron oxide and suboxides and rupture of the precursor particles resulting in formation of boron carbide molecular clusters that grow to macroscopic particles by coagulation. Consequently, the formation and growth of B4C particles is described by simultaneous interparticle collision and coalescence using a two-dimensional distribution model that traces the evolution of both size and shape characteristics of the particles through their volume and surface area. Here, in addition to the coagulation term, the governing population balance equation includes a coalescence contribution based on B4C sintering law. The predicted evolution of the two-dimensional particle size distribution leads to a direct characterization of morphology as well as the average size and polydispersity of the powders. Furthermore, model predictions of the volume and surface area of boron carbide particles can be directly compared with experimental data of B4C specific surface area and grain size.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 242: Symposium G – Wide Band-Gap Semiconductors , 1992 , 643
Copyright
Copyright © Materials Research Society 1992

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