| 摘要 |
The inventions provide nanocrystallites and processes for the production of these nanocrystallites according to known silica-based sol-gel preparation principles based on hydrolysis/condensation mechanisms. The processes include a synthesis step comprising providing a homogenized colloidal dispersion of precursors, catalyst, and surfactant to form the sol matrix. The processes further include a novel drying step for a wet hydrogel intermediate product, including a short-cycle drying period during which the liquids present in this hydrogel can be evaporated at ambient pressure and low temperature ranges in any convenient drying apparatus while, inter alia, preserving the gel structure, especially gel porosity. Porosity values for the dried product up to about 98-99% can be attained, with product He densities as low as about 0.033 g/cc. Nanocrystallites produced by this process have, inter alia, excellent clarity, thermal insulation, acoustic insulation, surface scattering, and bulk modulus properties.
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