University of Illinois Urbana-Champaign

Experimental study of physical-chemical factors in the sol-gel process

Hua, Duen-Wu

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Description

Title
Experimental study of physical-chemical factors in the sol-gel process
Author(s)
Hua, Duen-Wu
Issue Date
1991
Doctoral Committee Chair(s)
Jonas, Jiri
Department of Study
Chemistry
Discipline
Chemistry
Degree Granting Institution
University of Illinois at Urbana-Champaign
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
  • Chemistry, Analytical
  • Chemistry, Physical
Language
eng
Abstract
  • A variety of experimental techniques (multinuclear NMR, Raman, small angle neutron scattering, fluorescence polarization, viscosity, turbidity, static and dynamic light scattering experiments) have been employed to investigate the nature of the sol-gel process of tetramethyl orthosilicate; Si(OCH$\sb3$)$\sb4$; TMOS. These experiments probe changes in structural and dynamical properties at the macroscopic and microscopic level in the course of the sol-gel process and the transition state. The experimental results are compared with recent theories for the gelation process.
  • Another important factor that influence the gel formation is the catalyst, usually a base or acid, or the so called drying control chemical additives (DCCA) which not only can greatly reduce the gelation time but can avoid cracking during the sintering process. Small angle neutron scattering measurement has been used to investigate the particle size, structural evolution and growth process of the fluorine catalyzed sols. The effect on pore structure of the resulting gels and its evolution during heat treatment have been studied by the nitrogen ad(de)sorption isotherm (BET) measurements. The applicability of catalyst fluoride on the sol-gel systems and the comparison with the plain gel are studied.
  • Pressure is also a parameter that affects the sol-gel process, especially the kinetics. Since the existing functional reactivity theory for the sol-gel kinetics has only been applied on the acidic catalyzed system, the application of this theory to the plain (neutral) system seemed necessary. In addition the pressure effects on the kinetics can provide information about the origin of the mechanisms of the process. The experiment shows that both the hydrolysis and condensation reactions are accelerated by the pressure, the latter being affected to a larger extent. The experimental data obtained allow us to use the functionality theory for the beginning stage of the sol-gel process. (Abstract shortened with permission of author.)
Type of Resource
text
Permalink
http://hdl.handle.net/2142/20914
Copyright and License Information
Copyright 1991 Hua, Duen-Wu

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