US5045513A
Expired / Lapsed
US
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Sintered body of silicon nitride and its manufacture
Assignee: Niterra Co Ltd
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Filing: 1989-08-15
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Granted: 1991-09-03
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Expires: 2009-08-15
Abstract
Abstract A sintered body of silicon nitride with high density, strength, toughness, and hardness, which can be used for a structural part of an engine, etc. The sintered body of the invention includes 80 to 94 wt % Si 3 N 4 , 2 to 10 wt % Mg compound calculated in MgO equivlent, and 2 to 10 wt % Y compound calculated in Y 2 O 3 equivalent. The Si 3 N 4 contains 5 to 40% α-phase. The sintered body is manufactured in the following steps: (a) mixing powdery Si 3 N 4 with a Mg compound and a Y compound in the above proportions, and then molding the mixture in which the Si 3 N 4 powder contains 80% or more α-phase and its grains are 1 μm or less in diameter on average; (b) performing primary sintering at 1,600° C. or less in an atmospher of nitrogen or of an inert gas at 20 atm or less; and (c) performing secondary sintering at 1,400° to 1,600° C. in an atmosphere of nitrogen or of an inert gas at 300 atm or more.
Inventors
- 👤 Kenichi Mizuno
- 👤 Katsuhisa Yabuta
- 👤 Masakazu Watanabe
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 14:30
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/5935
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
85 words
A sintered body of silicon nitride having a relative density of 98% or more, comprising 80 to 94 wt % Si 3 N 4 , 2 to 10 wt % compound calculated in MgO equivalent, and 2 to 10 wt % Y compound calculated in Y 2 O 3 equivalent, wherein the Si 3 N 4 contains 5 to 40% α-phase and the Si 3 N 4 comprises grains 90 vol % or more of which have a minor axis of 1 μm or less.
Claim 2
Dependent Claim
85 words
A sintered body of silicon nitride having a relative density of 98% or more, comprising 80 to 94 wt % Si 3 N 4 , 2 to 10 wt % compound calculated in MgO equivalent, and 2 to 10 wt % Y compound calculated in Y 2 O 3 equivalent, wherein the Si 3 N 4 contains 5 to 40% α-phase and the Si 3 N 4 comprises grains 90 vol % or more of which have a minor axis of 1 μm or less.
Claim 3
Dependent Claim
186 words
A process for manufacture of a sintered body of silicon nitride comprising the steps of: (a) mixing 80 to 94 wt % powdery Si 3 N 4 with 2 to 10 wt % Mg compound calculated in MgO equivalent and with 2 to 10 wt % Y compound calculated in Y 2 O 3 equivalent, and then molding the mixture, in which the Si 3 N 4 powder contains 80% or more α- phase, and the grains are 1 μm or less in diameter on average; (b) performing primary sintering of the molded object in step (a) at 1,600° C. or less in an atmosphere of nitrogen or nitrogen and an inert gas at 1 to 20 atm to provide a sintered body having a relative density of 85% or more; and (c) performing secondary sintering of the sintered body in step (b) at 1,400° to 1,600° C. in an atmosphere of nitrogen and an inert gas at 300 atm or more, such that 90 vol % or more of the grains in the sintered body produced have a minor axis of 1 μm or less.
Claim 4
Dependent Claim
186 words
A process for manufacture of a sintered body of silicon nitride comprising the steps of: (a) mixing 80 to 94 wt % powdery Si 3 N 4 with 2 to 10 wt % Mg compound calculated in MgO equivalent and with 2 to 10 wt % Y compound calculated in Y 2 O 3 equivalent, and then molding the mixture, in which the Si 3 N 4 powder contains 80% or more α- phase, and the grains are 1 μm or less in diameter on average; (b) performing primary sintering of the molded object in step (a) at 1,600° C. or less in an atmosphere of nitrogen or nitrogen and an inert gas at 1 to 20 atm to provide a sintered body having a relative density of 85% or more; and (c) performing secondary sintering of the sintered body in step (b) at 1,400° to 1,600° C. in an atmosphere of nitrogen and an inert gas at 300 atm or more, such that 90 vol % or more of the grains in the sintered body produced have a minor axis of 1 μm or less.
Claim 5
Dependent Claim
48 words
A process for manufacture of a sintered body of silicon nitride as in claim 2 wherein said secondary sintering is conducted in an atmosphere of nitrogen and an inert gas, in which the nitrogen partial pressure in both the primary and secondary sintering is 1 atm or more.
Claim 6
Dependent Claim
32 words
A process for manufacture of a sintered body of silicon nitride as in claim 2 in which the temperature in the secondary sintering is in the range of 1,450° to 1,550° C.
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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) | 1994-09-02 | 1995-03-04 | 1995-09-03 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1998-09-02 | 1999-03-04 | 1999-09-03 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2002-09-02 | 2003-03-04 | 2003-09-03 | $7700.00 | Window Closed / Lapsed |