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The Influence of Alkali Metal Hydroxides on Silica Condensation Rates: The Role of Ion Pairing

Published online by Cambridge University Press:  25 February 2011

A. V. McCormick ,
A. T. Bell  and
C. J. Radke
A. V. McCormick
Affiliation:
Department of Chemical Engineering, University of California, Berkeley, CA. 94720
A. T. Bell
Affiliation:
Department of Chemical Engineering, University of California, Berkeley, CA. 94720
C. J. Radke
Affiliation:
Department of Chemical Engineering, University of California, Berkeley, CA. 94720
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Abstract

The condensation kinetics and the role of Ion pairing are investigated for silicate anions in alkaline solutions. Selective, and non-selective inversion recovery experiments are performed using the Si NMR spectrum of alkali metal silicate solutions. In this way the rates of condensation of silicate monomers is studied as a function of the nature of the base. These rates exhibit maxima with increasing cation size. The maxima are interpreted in terms of the concentration and activity of ion pair intermediates of the Si exchange reaction.

Interactions between alkali metal cations and larger silicate anions in silicate solutions are investigated using NMR spectroscopy of the cations. The chemical shift and the resonance llnewidths are used to estimate the concentration of cation-silicate ion pairs. The concentration of pairs involving large anions increases with increasing cation size. Thus it is expected that condensation kinetics are influenced by the size of the silicate fragment.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 121: Symposium H – Better Ceramics Through Chemistry III , 1988 , 67
Copyright
Copyright © Materials Research Society 1988

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References

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