ABSTRACT
Uniform Silica Particles . . . . . . . . . . . . . . . . . . . . . . 566
Size-Dependent Aggregation Rates . . . . . . . . . . . . . 568
Uniform Titania Particles . . . . . . . . . . . . . . . . . . . . . 569
Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 571
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . . 572
References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 572
The mechanism of precipitation of uniform particles through the hydrolysis and condensation of metal
alkoxides is discussed. Final particle sizes were found to be sensitive to the reaction medium ionic strength
and the surface potential of the growing particles. In addition, the rate of loss for soluble metal-containing
species was found to be independent of the surface area of the growing particles. These observations imply
that the major growth pathway is through agglomeration of small gel particles produced by reactions
between soluble species that proceed independent of the presence of particles. Calculations that are
presented support this growth mechanism.
