The precipitation of uniform silica particles through the controlled hydrolysis of silicon alkoxides
Bogush, Gregory Harry
This item is only available for download by members of the University of Illinois community. Students, faculty, and staff at the U of I may log in with your NetID and password to view the item. If you are trying to access an Illinois-restricted dissertation or thesis, you can request a copy through your library's Inter-Library Loan office or purchase a copy directly from ProQuest.
Permalink
https://hdl.handle.net/2142/22008
Description
Title
The precipitation of uniform silica particles through the controlled hydrolysis of silicon alkoxides
Author(s)
Bogush, Gregory Harry
Issue Date
1990
Doctoral Committee Chair(s)
Zukoski, Charles F.
Department of Study
Chemical and Biomolecular Engineering
Discipline
Chemical Engineering
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
Engineering, Chemical
Language
eng
Abstract
The formation of uniform silica particles by the alkoxide route has been investigated. Rates of chemical reactions involved in the precipitation are reported and linked to particle growth rates. Seeded growth experiments indicate that reactions between soluble species occur at rates that are independent of the size and number density of the seed particles. Estimates of hydrolyzed alkoxide concentrations based on solution conductivity suggest that the soluble silica concentration is above that required for nucleation until late in the reaction. These results are consistent with a particle growth mechanism whereby reactions occurring in solution proceed independently of the presence of particles, resulting in the formation of silica nuclei, which aggregate to form larger particles. This hypothesis has been further checked by carrying out precipitations at different electrolyte concentrations. While rates of hydrolysis and condensation are not substantially affected by NaCl concentrations up to 10$\sp{\rm -2}$ M, final particle size increases drastically.
An aggregative growth model has been developed and tested with rate and particle size distribution data gathered under various reaction conditions. Smoluchowski population balance equations with a source term were solved for conditions applicable to the precipitations studied. Size dependant aggregation rate constants were determined from estimates of particle properties. By assuming that particles grow solely by aggregation, the model provides good estimates of final particle size distribution parameters from measured reaction rates.
Use this login method if you
don't
have an
@illinois.edu
email address.
(Oops, I do have one)
IDEALS migrated to a new platform on June 23, 2022. If you created
your account prior to this date, you will have to reset your password
using the forgot-password link below.
