Patent US4029755A successfully refreshed from Google Patents.
US4029755A
Expired / Lapsed
US
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Transparent ultrafine grained ceramics
Assignee: United States Department of the Army
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Filing: 1973-04-11
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Granted: 1977-06-14
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Expires: 1993-04-11
Abstract
Abstract A pressure sintering process for the fabrication of ultrafine grained cercs having improved strength and enhanced transparency comprising the cold compressing of a ceramic oxide powder having a cubic crystal structure, removing undesired gases, raising to a temperature at which full density of the compact can be obtained in isothermal increments of about 50° under elevated pressures while maintaining the temperature at each incremental increase for a period of about 50-60 minutes, and recovering the product.
Inventors
- 👤 George E. Gazza
- 👤 Sunil K. Dutta
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 10:12
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64; C04B35/645; C01; C01F; C01F7/00; C01F7/02; C01F7/04; C01F7/043; C04B35/01; C04B35/44; C01P; C01P2002/00; C01P2002/30; C01P2002/32; C01P2004/00; C01P2004/60; C01P2004/61; C01P2006/00; C01P2006/10; C01P2006/60; Y; Y10; Y10S; Y10S264/00; Y10S264/91
Claims Analysis
Total Claims: 2
Claim 1
Independent Claim
151 words
Light-transparent ultrafine grained lithium aluminate made by a method of cold-pressing a lithium aluminate powder having a cubic crystal structure and having the formula LiAl 5 O 8 , to form a compact, followed by pressing the compact; said method comprising the steps of: cold-compressing said lithium aluminate powder to about 40-50% of theoretical density to form a compact, heating the compact under a vacuum to about 600° C to remove undesired gases, raising the temperature of said compact to about 1,150° C, applying a pressure of about 6000-7000 p.s.i., maintaining said compact at said temperature and pressure for about 50-60 minutes, further raising the temperature of said compact to about 1,600° C in isothermal increments of about 50° C under said pressure while maintaining the temperature at each incremental increase for a period of about 50-60 minutes, and recovering a full-density light-transparent product having a grain of about 1 micron.
Claim 2
Dependent Claim
151 words
Light-transparent ultrafine grained lithium aluminate made by a method of cold-pressing a lithium aluminate powder having a cubic crystal structure and having the formula LiAl 5 O 8 , to form a compact, followed by pressing the compact; said method comprising the steps of: cold-compressing said lithium aluminate powder to about 40-50% of theoretical density to form a compact, heating the compact under a vacuum to about 600° C to remove undesired gases, raising the temperature of said compact to about 1,150° C, applying a pressure of about 6000-7000 p.s.i., maintaining said compact at said temperature and pressure for about 50-60 minutes, further raising the temperature of said compact to about 1,600° C in isothermal increments of about 50° C under said pressure while maintaining the temperature at each incremental increase for a period of about 50-60 minutes, and recovering a full-density light-transparent product having a grain of about 1 micron.
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) | 1980-06-13 | 1980-12-13 | 1981-06-14 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-06-13 | 1984-12-13 | 1985-06-14 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-06-13 | 1988-12-13 | 1989-06-14 | $7700.00 | Window Closed / Lapsed |