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Micrqporous Silica Gels from Alkylsilicate-Water Two Phase Hydrolysis

Published online by Cambridge University Press:  21 February 2011

L. Chu ,
M. I. Tejedor-Tejedor  and
M. A. Anderson
L. Chu
Affiliation:
Water Chemistry Program, University of Wisconsin-Madison, Madison, Wisconsin 53706
M. I. Tejedor-Tejedor
Affiliation:
Water Chemistry Program, University of Wisconsin-Madison, Madison, Wisconsin 53706
M. A. Anderson
Affiliation:
Water Chemistry Program, University of Wisconsin-Madison, Madison, Wisconsin 53706
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Abstract

Microporous silica gels have been synthesized through a nano-particulate sol-gel route. These gels have uniformly distributed and extremely small pores(< 15Â in diameter). Hydrolysis and condensation reactions leading to these gels were carried out in an alkyl silicate-water (ammonia) two phase system. These reactions took place at the alkyl silicate droplet-water interfacial boundary. No alcohol was added. A clear, stable and uniformly distributed colloidal silica suspension having an average particle size less than 6 nm was prepared by this method. Fast hydrolysis, slow condensation and low solubility all contribute to a high supersaturation level and result in the formation of small particles. This process is consistent with classic nucleation theory. When the particles are produced under acidic rather than under basic reaction conditions, smaller particles are formed due to the slower condensation rate and lower solubility of these silica particles in acidic conditions. At the same pH, alkylsilicates having smaller alkyl groups react faster with water leading to smaller primary particles. Homogeneous nucleation conditions are achieved when the water/alkylsilicate ratio is high.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 346: Symposium N – Better Ceramics Through Chemistry VI , 1994 , 855
Copyright
Copyright © Materials Research Society 1998

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References

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