Patent US3953221A successfully refreshed from Google Patents.
US3953221A
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US
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Fully dense ceramic article and process employing magnesium oxide as a sintering aid
Assignee: United States Department of the Navy
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Filing: 1975-04-22
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Granted: 1976-04-27
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Expires: 1995-04-22
Abstract
Abstract Fully dense ceramic articles are prepared by mixing powders of silicon nitride, aluminum oxide and magnesium oxide to form a composite powder composition wherein the magnesium oxide acts as a sintering aid, forming the composite powder into a desired shape, and heating the shaped composite powder composition in the absence of applied pressure at a temperature sufficient to effect sintering of the composition.
Inventors
- 👤 Frederick F. Lange
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-24 23:25
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/597
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
117 words
A process for producing a fully dense ceramic article which comprises the steps of a. mixing Si 3 N 4 , Al 2 O 3 and MgO powders to form a composite powder composition wherein the composition comprises about 50 to about 80 weight percent of Si 3 N 4 , about 15 to about 50 weight percent of Al 2 O 3 , and about 0.25 to about 5 weight percent of MgO based on the total weight of the composition; b. forming the composite powder composition into a desired shape; and c. heating the shaped composite powder composition in an non-oxidizing atmosphere under ambient pressure at a sintering temperature from about 1400°C to about 1750°C.
Claim 2
Dependent Claim
117 words
A process for producing a fully dense ceramic article which comprises the steps of a. mixing Si 3 N 4 , Al 2 O 3 and MgO powders to form a composite powder composition wherein the composition comprises about 50 to about 80 weight percent of Si 3 N 4 , about 15 to about 50 weight percent of Al 2 O 3 , and about 0.25 to about 5 weight percent of MgO based on the total weight of the composition; b. forming the composite powder composition into a desired shape; and c. heating the shaped composite powder composition in an non-oxidizing atmosphere under ambient pressure at a sintering temperature from about 1400°C to about 1750°C.
Claim 3
Dependent Claim
18 words
The process of claim 1 wherein the composite powder composition is heated from about 1650°C to about 1750°C.
Claim 4
Dependent Claim
8 words
The product of the process of claim 1.
Claim 5
Dependent Claim
90 words
In a process for producing a dense ceramic article by mixing powders of Si 3 N 4 and Al 2 O 3 , forming the mixture into a desired shape, and heating the shaped mixture in a non-oxidizing atmosphere under ambient pressure at a temperature sufficient to effect the sintering thereof, the improvement which comprises adding to the Si 3 N 4 - Al 2 O 3 powder mixture about 0.25 to about 5 weight percent of MgO, based on the total weight of the mixture, as a sintering aid.
Claim 6
Dependent Claim
90 words
In a process for producing a dense ceramic article by mixing powders of Si 3 N 4 and Al 2 O 3 , forming the mixture into a desired shape, and heating the shaped mixture in a non-oxidizing atmosphere under ambient pressure at a temperature sufficient to effect the sintering thereof, the improvement which comprises adding to the Si 3 N 4 - Al 2 O 3 powder mixture about 0.25 to about 5 weight percent of MgO, based on the total weight of the mixture, as a sintering aid.
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) | 1979-04-27 | 1979-10-27 | 1980-04-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-04-27 | 1983-10-27 | 1984-04-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-04-27 | 1987-10-27 | 1988-04-27 | $7700.00 | Window Closed / Lapsed |