Thermochemistry of aqueous silicate solution precursors to ceramics

A quantitative understanding of the thermochemistry of silicate solution systems is necessary for the design, optimization and control of sol-gel, colloid and zeolite preparations. This review is intended to be a compendium of ready information for the growing number of chemical engineers active in solution-based materials synthesis. Experimental measurements of Silica solubility, silicate speciation and silanol deprotonation in aqueous solutions are summarized and critiqued. The thermochemical properties of monomeric and dimeric silicate anions are also assessed. The trends that are then evident are compared with expectations fr om simplistic gas-phase molecular orbital calculations to illustrate the importance of solvation. Finally, the equilibrium behavior of simple silicate oligomers is rationalized, and the future direction to quantitative modeling of the behavior of more complex oligomers is suggested