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Current Issues in Sol-Gel Reaction Kinetics

Published online by Cambridge University Press:  28 February 2011

Roger A. Assink  and
Bruce D. Kay
Roger A. Assink
Affiliation:
Sandia National LaboratoriesAlbuquerque, NM 87185
Bruce D. Kay
Affiliation:
Sandia National LaboratoriesAlbuquerque, NM 87185
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Abstract

This paper surveys a few of the current issues in sol-gel reaction kinetics. Many times seemingly modest changes in reactants or reaction conditions can lead to substantial differences in the overall reaction rates and pathways. For example, qualitative features of the reaction kinetics can depend on catalyst concentration. At very high acid-catalyst concentrations, reverse reactions are significant for TMOS solgels, while for moderate acid-catalyst concentrations, reverse reactions are substantially reduced. The reaction kinetics of two similar tetraalkoxysilanes: tetramethoxysilane (TMOS) and tetraethoxysilane (TEOS), can be markedly different under identical reaction conditions. Under acid-catalyzed reaction conditions, a TMOS sol-gel undergoes both water- and alcoholproducing condensation reactions while a TEOS sol-gel undergoes only water-producing condensation. The early time hydrolysis and condensation reactions of a TMOS sol-gel are statistical in nature and can be quantitatively described by a few simple reaction rate constants while the reaction behavior of a TEOS sol-gel is markedly nonstatistical. A comprehensive theory of sol-gel kinetics must address these diverse experimental findings.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 180: Symposium A – Better Ceramics Through Chemistry IV , 1990 , 21
Copyright
Copyright © Materials Research Society 1990

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References

REFERENCES

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