Processing routes have been developed for the production of thin ceramic films through precipitation from aqueous solutions. The techniques are based on crystal nucleation and growth onto functionalized interfaces. Surface functionalization routes have been developed by the mimicking of schemes used by organisms to produce complex ceramic composites such as teeth, bones, and shells. High-quality, dense polycrystalline films of oxides, hydroxides, and sulfides have now been prepared from "biomimetic" synthesis techniques. Ceramic films can be synthesized on plastics and other materials at temperatures below 100 degrees C. As a low-temperature process in which water rather than organic solvents is used, this synthesis is environmentally benign. Nanocrystalline ceramics can be produced, sometimes with preferred crystallite orientation. The direct deposition of high-resolution patterned films has also been demonstrated. The process is well suited to the production of organic-inorganic composites.

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The interactive effects between ductile iron and PNL 76-68 borosilicate glass were investigated as a function of time in 90°C static deionized, tuff, and basalt groundwaters. A synergistic effect occurs between the two materials, i. e. iron enhances glass dissolution and glass enhances iron corrosion. An iron silicate precipitate forms, part of which is colloidal in nature. This precipitate effectively removes many of the elements from solution and therefore inhibits the saturation effects which normally cause decreases in elemental removal rates. Thus, the effects of initial solution composition on the glass leach rates are significantly reduced and the relatively high early leach rates normally observed in deionized water are maintained for longer times due to the suppression of saturation effects. This results in more total elemental removal from the glass in all of the groundwaters evaluated. The precipitate and its colloidal form require further characterization.

Leaching tests of PNL 76-68 glass in deionized water have been performed using the standard MCC-l static leaching procedure but with varied glass surface area to solution volume ratios (SA/V).It was found that leaching could be strongly influenced by the SA/V ratio, due largely to an effect of silicon solubility limitations. The conclusion that solubility and not solid state diffusion is most important in regulating leaching rates is supported by (1) the similarities in depth profiles of all soluble glass components with none depleted to depths greater than that of silicon despite vastly different solid state diffusivities, and (2) the lack of dependence of leaching rates on reaction layer thicknesses.To more directly examine the influence of dissolved silicon on glass leaching rates, leaching tests were performed in silicic acid solutions and in two actual groundwaters.As expected, leaching rates of all soluble glass components were reduced by amounts roughly proportional to the silicon saturation fraction.Since solubility modifies leaching rates in all but very dilute solutions, short-term tests at high SA/V values can be used to predict solution concentrations for long-term tests at low SA/V values, although reaction layers formed are not of the same thickness.Glass leaching data for a range of leaching times and SA/V values can be represented by a single curve when plotted versus the product of SA/V and time.However, the use of SA/V variations may have limited usefulness in accelerated leach testing for multicomponent systems.Events such as silica colloid and certain alteration phase formations modify the above relationship.