Fabrication including sol-gel processing
US5944866A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 3, 1998 |
| Grant date | Aug 31, 1999 |
| Priority date | — |
| Expiry date | Jun 3, 2018 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S65/901
- WIPO fieldMaterials, metallurgy
- WIPO sectorChemistry
Abstract
The invention provides an alternative to conventional sol-gel methods that utilize undesirably high amounts of a stabilizing agent such as TMAH and a gelling agent such as methyl formate. The method involves the steps of (a) providing a colloidal silica dispersion containing a stabilizing/gelling agent, where only a portion of the molecules of the agent ionize, and (b) subsequently adding to the silica dispersion a pH-reducing additive. The stabilizing/gelling agent has a dual function. The agent, e.g., an amine, initially acts as a stabilizer in the silica dispersion in that a portion of its molecules ionize, while an appreciable amount of the agent remains non-ionized. The agent later transforms in situ to a gelling agent upon addition of a pH-reducing additive. Specifically, as the pH-reducing additive lowers the pH to values at or around the pK.sub.a of the stabilizing/gelling agent, more of the agent's molecules are ionized, these cations contributing to charge neutralization, and thus gellation, of the colloidal silica particles.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.