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Powder Synthesis in Aerosol Reactors


Wu, Jin Jwang (1987) Powder Synthesis in Aerosol Reactors. Dissertation (Ph.D.), California Institute of Technology. doi:10.7907/njvw-jn75.


The onset of homogeneous nucleation of new particles from the products of gas phase chemical reactions has been explored using an aerosol flow reactor. Silicon seed particles were used as a probe to study the transition from seed growth by cluster deposition to runaway nucleation. This transition was found to be very abrupt. The mechanism of formation of solid particles from large excesses of low vapor pressure condensible species has been investigated by studying the microstructure of the product aerosol. A discrete - sectional solution of the aerosol general dynamic equation was derived in order to examine the aerosol evolution associated with fast chemical reactions. This kinetic model quantitatively predicts the aforementioned transition. Application of the understanding of aerosol generation and growth has led to the production of a high quality silicon powder suitable for ceramic applications. This powder was synthesized by the pyrolysis of silane in an aerosol reactor and has nearly ideal characteristics, i.e., controlled size distribution, spherically shaped, nonagglomerated submicron particles. A simple reaction coagulation model was developed to facilitate mapping of the nucleation and growth domains. This, in conjuction with the discrete-sectional model, was used to evaluate the various aerosol processes for powder synthesis. The influence of the initial reactant concentration, reaction rate, temperature profile, seed particle conditions, and residence time on the final powder characteristics were examined. The structure of the particles also depends on the way particles fuse together. Particle fusing was therefore, modeled along with the formation and growth processes to study the effects of coalescence on the extent of agglomeration of the product powder. A recipe for the synthesis of ideal powders was proposed.

Item Type:Thesis (Dissertation (Ph.D.))
Subject Keywords:Environmental Engineering Science; Chemical Engineering
Degree Grantor:California Institute of Technology
Division:Engineering and Applied Science
Major Option:Environmental Science and Engineering
Minor Option:Chemical Engineering
Thesis Availability:Public (worldwide access)
Research Advisor(s):
  • Flagan, Richard C.
Thesis Committee:
  • Flagan, Richard C. (chair)
  • Weinberg, William Henry
  • Morgan, James J.
  • Johnson, William Lewis
  • Cass, Glen Rowan
Defense Date:1 October 1986
Record Number:CaltechETD:etd-06152006-074336
Persistent URL:
Related URLs:
URLURL TypeDescription adapted for Chapter 4. adapted for Appendix A1
Default Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:2605
Deposited By: Imported from ETD-db
Deposited On:29 Jun 2006
Last Modified:16 Apr 2021 22:29

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