Sol-gel processing of silica
- Sandia National Labs., Albuquerque, NM (United States)
The sol-gel process for preparing silica and silicates from metal alkoxide precursors is reviewed and compared to the processing of aqueous silicates as described by Iler. Sol-gel processing combines control of composition and microstructure at the molecular level with the ability to shape material in bulk, powder, fiber, and thin-film form. In sol-gel processing of metal alkoxides, hydrolysis reactions replace an alkoxide group with a hydroxyl group. Subsequent condensation reactions involving the hydroxyl groups produce siloxane bonds. The structure of the evolving silicates is a consequence of the successive polymerization, gelation, aging, drying, and heating steps. Often the structures of polymers, gels, and dried gels (either xerogels or aerogels) may be characterized on the 1-20-nm length scale by a mass or surface fractal dimension. On longer length scales, dried gels are micro- or mesoporous, with surface areas often exceeding 800 m{sup 2}/g. During heating, these gels undergo continued polymerization, structural relaxation, and viscous sintering; dense amorphous silica essentially indistinguishable from its conventionally prepared counterpart ultimately results. 123 refs., 18 figs., 2 tabs.
- OSTI ID:
- 86471
- Report Number(s):
- CONF-900802--
- Country of Publication:
- United States
- Language:
- English
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