US4943543A
Expired / Lapsed
US
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Sintered ceramic materials
Assignee: Sandvik AB
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Filing: 1988-12-07
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Granted: 1990-07-24
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Expires: 2008-12-07
Abstract
Abstract This invention relates to sintered ceramic materials in which the densification during sintering takes place with a liquid phase preferably based on silicon nitride. During sintering such materials are often embedded in a powder of inert material such as BN, etc. The invention resides in the fact that by embedding the material to be sintered in a protective powder with a composition similar to that of the intergranular phase, a surface zone with a composition and/or structure different from that of the core can be obtained.
Inventors
- 👤 Nils A. Ingelstrom
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 12:43
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/597
Claims Analysis
Total Claims: 17
Claim 1
Independent Claim
58 words
Sintered ceramic material based on silicon nitride, silicon oxide, aluminum nitride, aluminum oxide or mixtures thereof, in which the densification during sintering takes place with an intergranular liquid phase, said material comprising a core and a surface zone with a gradual transition in at least one of composition and crystal structure between said core and said surface zone.
Claim 2
Dependent Claim
58 words
Sintered ceramic material based on silicon nitride, silicon oxide, aluminum nitride, aluminum oxide or mixtures thereof, in which the densification during sintering takes place with an intergranular liquid phase, said material comprising a core and a surface zone with a gradual transition in at least one of composition and crystal structure between said core and said surface zone.
Claim 3
Dependent Claim
29 words
Sintered material according to claim 1, in which the surface zone is more than 100 μm thick and with a density of more than 98% of the theoretical density.
Claim 4
Dependent Claim
10 words
Sintered material according to claim 1, based on silicon nitride.
Claim 5
Dependent Claim
10 words
Sintered material according to claim 2, based on silicon nitride.
Claim 6
Dependent Claim
32 words
Method of producing a sintered material according to claim 1 comprising the step of sintering the ceramic material in a protective powder with a composition similar to that of the intergranular phase.
Claim 7
Dependent Claim
32 words
Method of producing a sintered material according to claim 5, wherein the surface zone is more than 100 μm thick and with a density of more than 98% of the theoretical density.
Claim 8
Dependent Claim
18 words
Method of producing a sintered material according to claim 5, wherein the material is based on silicon nitride.
Claim 9
Dependent Claim
20 words
Sintered ceramic material according to claim 1 in which the thickness of the surface zone is greater than 500 μm.
Claim 10
Dependent Claim
19 words
Sintered ceramic material according to claim 8 in which the thickness of the surface zone is from 0.8-2 mm.
Claim 11
Dependent Claim
27 words
Sintered ceramic material according to claim 1 in which the surface zone comprises beta-sialon ceramic material and the core comprises mixtures of alpha- and beta-sialon ceramic materials.
Claim 12
Dependent Claim
27 words
Sintered ceramic material according to claim 1 in which the surface zone comprises mixtures of alpha- and beta-sialon ceramic materials and the core comprises beta-sialon ceramic material.
Claim 13
Dependent Claim
17 words
Sintered ceramic material according to claim 1 wherein the sintered ceramic material includes fiber or whisker reinforcements.
Claim 14
Dependent Claim
19 words
Method of producing a sintered material according to claim 5 wherein sintering is performed in a nitrogen gas-containing atmosphere.
Claim 15
Dependent Claim
20 words
Method of producing a sintered material according to claim 13 wherein sintering is performed at nitrogen pressures above 1 atmosphere.
Claim 16
Dependent Claim
20 words
Method of producing a sintered material according to claim 14 wherein the nitrogen pressure is from 15 to 30 atmospheres.
Claim 17
Dependent Claim
21 words
Method of producing a sintered material according to claim 14 wherein sintering aids are included in the material to be sintered.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-07-23 | 1994-01-22 | 1994-07-24 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-07-23 | 1998-01-22 | 1998-07-24 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-07-23 | 2002-01-22 | 2002-07-24 | $7700.00 | Window Closed / Lapsed |