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DFT Investigation of the Mechanism and Chemical Kinetics for the Gelation of Colloidal Silica

Published online by Cambridge University Press:  21 May 2013

Steven S. Burnett  and
James W. Mitchell
Steven S. Burnett
Affiliation:
Howard University 2300 Sixth Street, Rm. 1124, NW, Washington, DC 20059 U.S.A.
James W. Mitchell
Affiliation:
Howard University 2300 Sixth Street, Rm. 1124, NW, Washington, DC 20059 U.S.A.
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Abstract

The mechanism for the gelation reaction of colloidal silica, Si(OH)4 +Si(OH)3 (O)- ----> Si2O8H5- + H2O, by an anionic pathway was investigated using density functional theory(DFT). Using transition state theory, the rate constants were obtained by analyzing the potential energy surface at the reactants, saddle point, and the products. In addition, reaction rate constants were investigated in the presence of ammonium chloride (NH4Cl) and sodium chloride (NaCl). These salts act as catalysts to induce gelation by destabilizing the double layer of colloidal silica to allow for Van der Waal interactions. Furthermore, it was observed that ammonium chloride plays an important role by initiating a hydride transfer allowing the reaction to proceed from the second transition state to the final product.

Keywords

chemical reactioncolloidsol-gel
Type
Articles
Information
MRS Online Proceedings Library (OPL) , Volume 1547: Symposium M – Solution Synthesis of Inorganic Functional Materials—Films, Nanoparticles and Nanocomposites , 2013 , pp. 173 - 182
Copyright
Copyright © Materials Research Society 2013 

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