US4587067A
Expired / Lapsed
US
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Method of manufacturing low thermal expansion modified cordierite ceramics
Assignee: Applied Biosystems Inc
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Filing: 1984-07-20
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Granted: 1986-05-06
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Expires: 2004-07-20
Abstract
Abstract The present invention is directed to a method of manufacturing low thermal expansion modified cordierite compositions which are especially useful in the manufacture of mirrors for high temperature applications, said method comprising the steps of: providing, on a molecular basis, a mixture of about 2 moles magnesium oxide, 2 moles aluminum oxide, and about 5 moles divided between silicon dioxide and germanium oxide; blending said materials; milling the mixture until finely divided and thoroughly mixed; forming said mixture into a desired shape; gradually heating the shape to a temperature at which reactive sintering occurs and a cordierite type structure is formed; gradually cooling the structure; and hot compacting the structure to consolidate the sintered body to very nearly 100 percent of theoretical density.
Inventors
- 👤 Dinesh K. Agrawal
- 👤 Vladimir S. Stubican
- 👤 Yogesh Mehrotra
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 03:17
CPC Classifications
G; G02; G02B; G02B5/00; G02B5/08; C; C04; C04B; C04B35/00; C04B35/01; C04B35/16; C04B35/18; C04B35/195; G02B1/00
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
177 words
A method of fabricating germanium-cordierite ceramic body comprising the sequential steps of: providing on a molecular basis, a powdered mixture of about 2 moles magnesium oxide, about 2 moles aluminum oxide, and about 5 moles divided between silicon dioxide and germanium oxide; blending said powders; homogenizing said powders until finely divided and thoroughly mixed; oven drying said powders at a temperature of about 100° C.; densifying said powders by grinding to about a -32 mesh; cold compacting said powders into a desired shape by cold pressing said powders by building up the pressure in a series of gradual steps while holding the pressure constant at each step for a period of time sufficient to allow the system to reach equilibrium; gradually heating said compact to a temperature at which reactive sintering occurs and a cordierite type structure is formed; gradually cooling said structure; and hot isotatic pressing said structure at a temperature of about 1100° C. and a pressure of about 30,000 psi to consolidate the sintered body to very nearly 100 percent of the theoretical density.
Claim 2
Independent Claim
177 words
A method of fabricating germanium-cordierite ceramic body comprising the sequential steps of: providing on a molecular basis, a powdered mixture of about 2 moles magnesium oxide, about 2 moles aluminum oxide, and about 5 moles divided between silicon dioxide and germanium oxide; blending said powders; homogenizing said powders until finely divided and thoroughly mixed; oven drying said powders at a temperature of about 100° C.; densifying said powders by grinding to about a -32 mesh; cold compacting said powders into a desired shape by cold pressing said powders by building up the pressure in a series of gradual steps while holding the pressure constant at each step for a period of time sufficient to allow the system to reach equilibrium; gradually heating said compact to a temperature at which reactive sintering occurs and a cordierite type structure is formed; gradually cooling said structure; and hot isotatic pressing said structure at a temperature of about 1100° C. and a pressure of about 30,000 psi to consolidate the sintered body to very nearly 100 percent of the theoretical density.
Claim 3
Dependent Claim
23 words
A method according to claim 1 further comprising the step of stoichiometrically correcting said materials to correct for the weight loss on ignition.
Claim 4
Dependent Claim
35 words
A method according to claim 1 wherein said mixture is milled and homogenized for from about 12 hours to about 18 hours and an anti-coagulation dispersion agent is added to the mixture prior to milling.
Claim 5
Dependent Claim
24 words
A method according to claim 1 further comprising the step of adding binder materials to said powders before said step of homogenizing said powders.
Claim 6
Dependent Claim
24 words
A method according to claim 1 further comprising the step of adding binder to said powders subsequent to the step of densifying said powders.
Claim 7
Dependent Claim
20 words
A method according claim 1 wherein said cold pressing in effected up to a maximum pressure of about 20,000 psi.
Claim 8
Dependent Claim
14 words
A method according to claim 1 wherein said sintering temperature is about 1350° C.
Claim 9
Dependent Claim
148 words
A method according to claim 1 wherein the temperature schedule in said sintering step consists of gradually heating said compact to a temperature at which sintering occurs as follows: Room temperature to about 650° C.: in about 2 hours Hold at about 650° C.: for about 2 hours About 650° C. to about 800° C.: in about 10 minutes Hold at about 800° C.: for about 1.50 hours About 800° C. to about 900° C.: in about 10 minutes Hold at about 900° C.: for about 16 hours About 900° C. to about 1100° C.: in about 0.5 hours Hold at about 1100° C.: for about 2 hours About 1100° C. to about 1300° C.: in about 30 minutes Hold at about 1300° C.: for about 2 hours About 1300° C. to about 1360° C.: for about 30 minutes Hold at about 1360° C.: for about 2 hours.
References Cited (Backward Citations)
US4296065A
Cited
US4403017A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1989-05-05 | 1989-11-04 | 1990-05-06 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1993-05-05 | 1993-11-04 | 1994-05-06 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1997-05-05 | 1997-11-04 | 1998-05-06 | $7700.00 | Window Closed / Lapsed |