Patent US4786618A successfully refreshed from Google Patents.
US4786618A
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Sol-gel method for making ultra-low expansion glass
Assignee: Corning Glass Works
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Filing: 1987-05-29
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Granted: 1988-11-22
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Expires: 2007-05-29
Abstract
Abstract Ultra-low thermal expansion TiO 2 --SiO 2 glasses are prepared using a sol-gel process wherein a stable alkali silicate solution comprising colloidal TiO 2 and having a pH above 9 is gelled to form a semisolid silicate gel, the gel comprising homogeneously dispersed colloidal TiO 2 but being essentially free of agglomerated TiO 2 particles, washing the gel with aqueous media to remove alkali therefrom, and finally drying and consolidating the gel to a clear, void-free TiO 2 --SiO 2 glass which is substantially free of compositional inhomogeneities and has a thermal expansion coefficient below that of pure fused silica.
Inventors
- 👤 Robert D. Shoup
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 16:24
CPC Classifications
C; C03; C03B; C03B19/00; C03B19/12; C03C; C03C3/00; C03C3/04; C03C3/06; C03C3/076; C03B2201/00; C03B2201/06; C03B2201/30; C03B2201/40; C03B2201/42; C03C2201/00; C03C2201/06; C03C2201/30; C03C2201/40; C03C2201/42; C03C2203/00; C03C2203/20; C03C2203/24
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
193 words
A method for making a low expansion TiO 2 --SiO 2 glass which comprises the steps of: (a) preparing an aqueous sol wherein the liquid phase comprises at least one soluble silicate compound selected from the group of alkali silicates and ammonium silicates, and wherein the solid phase comprises colloidal TiO 2 , the sol being formed by combining a TiO 2 sol with a silicate solution containing dissolved SiO 2 compounds, said aqueous sol having a pH of at least 9 and being substantially free of precipitated SiO 2 and TiO 2 , the proportion of TiO 2 in the sol being such as to provide a TiO 2 concentration of TiO 2 and SiO 2 ; (b) gelling the sol to form a semisolid silicate gelled shape wherein the colloidal TiO 2 is homogeneously distributed; (c) removing alkaline constituents from the semisolid gelled shape to provide a dealkalized gel; (d) drying the dealkalized gel to remove water and residual volatile solution components and to provide a porous body therefrom; and (e) firing the porous body to a temperature sufficient to consolidate it to a non-porous TiO 2 --SiO 2 glass article.
Claim 2
Independent Claim
193 words
A method for making a low expansion TiO 2 --SiO 2 glass which comprises the steps of: (a) preparing an aqueous sol wherein the liquid phase comprises at least one soluble silicate compound selected from the group of alkali silicates and ammonium silicates, and wherein the solid phase comprises colloidal TiO 2 , the sol being formed by combining a TiO 2 sol with a silicate solution containing dissolved SiO 2 compounds, said aqueous sol having a pH of at least 9 and being substantially free of precipitated SiO 2 and TiO 2 , the proportion of TiO 2 in the sol being such as to provide a TiO 2 concentration of TiO 2 and SiO 2 ; (b) gelling the sol to form a semisolid silicate gelled shape wherein the colloidal TiO 2 is homogeneously distributed; (c) removing alkaline constituents from the semisolid gelled shape to provide a dealkalized gel; (d) drying the dealkalized gel to remove water and residual volatile solution components and to provide a porous body therefrom; and (e) firing the porous body to a temperature sufficient to consolidate it to a non-porous TiO 2 --SiO 2 glass article.
Claim 3
Dependent Claim
27 words
A method in accordance with claim 1 wherein the sol has an effective silica concentration in the range of about 1-12 moles of SiO 2 per liter.
Claim 4
Dependent Claim
32 words
A method in accordance with claim 2 wherein the soluble silicate compound is an alkali silicate compound, and wherein the sol has an effective SiO 2 concentration of 3-12 moles per liter.
Claim 5
Dependent Claim
20 words
A method in accordance with claim 3 wherein the solid phase of the sol additionally comprises colloidal SiO 2 .
Claim 6
Dependent Claim
44 words
A method in accordance with claim 3 wherein the sol is gelled by the addition of a gelling agent thereto which is effective to reduce the pH of the sol to a value at which SiO 2 will precipitate therefrom as a semisolid gel.
Claim 7
Dependent Claim
31 words
A method in accordance with claim 5 wherein the gelling agent is selected from the group consisting of formaldehyde, paraformaldehyde, formamide, glyoxal, methyl formate, methyl acetate, ethyl formate, and ethyl acetate.
Claim 8
Dependent Claim
31 words
A method in accordance with claim 3 wherein the TiO 2 is provided as an aqueous colloidal TiO 2 suspension containing quaternary ammonium ions and having a pH above about 9.
Claim 9
Dependent Claim
45 words
A method in accordance with claim 7 wherein the colloidal TiO 2 in the sol is present in a concentration providing a TiO 2 content in the range of about 7-10% of the total effective concentration of TiO 2 and SiO 2 in the sol.
Claim 10
Dependent Claim
17 words
A method in accordance with claim 8 wherein the gel has a pore size of 2000-3000 Å.
Claim 11
Dependent Claim
30 words
A method in accordance with claim 2 wherein the step of removing alkaline constituents from the semisolid gel comprises the immersion of the semisolid gel in an aqueous acidic medium.
Claim 12
Dependent Claim
36 words
A method in accordance with claim 2 wherein the step of drying the dealkalized gel comprises heating the gel to a temperature in the range of about 1000°-1100° C. to volatilize water and organic constituents therefrom.
Claim 13
Dependent Claim
15 words
A method in accordance with claim 2 wherein the step of drying comprises microwave heating.
Claim 14
Dependent Claim
37 words
A method in accordance with claim 2 wherein the step of firing the gel comprises heating the gel to a temperature in the range of about 1350°-1700° C. to consolidate the gel to a dense, non-porous glass.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-11-22 | 1992-05-23 | 1992-11-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-11-22 | 1996-05-23 | 1996-11-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-11-22 | 2000-05-23 | 2000-11-22 | $7700.00 | Window Closed / Lapsed |