Sol-gel processing of controlled pore films
During sol-gel film formation via dipping, polymeric precursors are aggregated on the substrate surface by a process involving gravitational flow, drying, and continued condensation reactions. To understand film formation in situ, we use ellipsometric imaging and infrared spectroscopy. The structure and porosity of the deposited film are determined by SAXS, ellipsometry, and surface acoustic wave (SAW) methods. We find that weakly-branched silicate precursors deposited near the isoelectric point of silica result in dense films (volume percent porosity, V/sub p/ < 5%) in which any pores present have radii <0.2 nm, regardless of precursor size. More compact precursors result in films in which the porosity and refractive index are controlled by the size of the precursor species prior to deposition and the relative rates of condensation and evaporation during deposition. The porosity and refractive index of these films may be varied as follows: volume percent porosity (0 less than or equal to V/sub p/ less than or equal to 56%); pore radius (0 less than or equal to r less than or equal to 3.1 nm); surface area (1.2 less than or equal to S less than or equal to 263 m/sup 2//g); refractive index (1.18 less than or equal to n less than or equal to 1.45). For repulsive, monosized particulate precursors, higher coating rates promote ordering providing an additional means of pore size control. 18 refs., 7 figs.
- Research Organization:
- Sandia National Labs., Albuquerque, NM (USA)
- DOE Contract Number:
- AC04-76DP00789
- OSTI ID:
- 6048707
- Report Number(s):
- SAND-88-2392C; CONF-890275-4; ON: DE89013584
- Country of Publication:
- United States
- Language:
- English
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