US4870036A
Expired / Lapsed
US
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High strength silicon nitride
Assignee: Honeywell International Inc
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Filing: 1988-03-08
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Granted: 1989-09-26
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Expires: 2008-03-08
Abstract
Abstract An improved silicon nitride material characterized by high mechanical strength at high temperatures comprising a combination of approximately 0.5-6.0% by weight of strontium oxide, 2.0-12% by weight of yttrium oxide and the balance silicon nitride. The improved material is densified by either an encapsulated hot isostatic pressing method or an encapsulated sinter/HIP method and can be utilized to form near net shape articles.
Inventors
- 👤 Hun C. Yeh
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 13:03
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
52 words
A densified silicon nitride article consisting essentially of 0.5-6.0% strontium oxide, by weight, formed by the in sitiu decomposition of strontium carbonate, 2-12% yttrium oxide by weight and the balance silicon nitride; wherein said article is characterized by having an average flexure strength of greater than about 465 MPa at 1400° C.
Claim 2
Dependent Claim
52 words
A densified silicon nitride article consisting essentially of 0.5-6.0% strontium oxide, by weight, formed by the in sitiu decomposition of strontium carbonate, 2-12% yttrium oxide by weight and the balance silicon nitride; wherein said article is characterized by having an average flexure strength of greater than about 465 MPa at 1400° C.
Claim 3
Dependent Claim
34 words
The article of claim 1 wherein said article has an average mechanical flexure strength of 888.8 MPa (129 KSI) at 21° C. (70° F.) and 585.7 MPa (84.3 KSI) at 1399° C. (2,550° F.).
Claim 4
Dependent Claim
54 words
The article of claim 1 made by the steps of: mixing 0.7-8.6% strontium carbonate by weight, 1.9-12.0% yttrium oxide by weight and the balance silicon nitride; forming the desired green body shape; decomposing said strontium carbonate to strontium oxide; and encapsulating/hot isostatically pressing the green body shape to form the densified silicon nitride article.
Claim 5
Dependent Claim
33 words
The article of claim 3 wherein said step of forming is preformed by one of the following processes: cold isostatic pressing, extrusion, uniaxial die pressing, injection molding or slip casting the desired shape.
Claim 6
Dependent Claim
18 words
The article of claim 3 wherein said step of encapsulating comprises coating with a glass the green-body shape.
Claim 7
Dependent Claim
23 words
The article of claim 3 wherein said step of encapsulating comprises enclosing the green-body shape in a metal can and sealing said can.
Claim 8
Dependent Claim
37 words
The article of claim 3 wherein said step of hot isostatically pressing comprises heating the encapsulated green body shape to 1600°-1900° C. and isostatically pressing said shape at 10.3-206.7 MPa (1.0-30 KSI) for 1 to 8 hours.
Claim 9
Dependent Claim
59 words
The article of claim 1 made by the steps of: mixing by weight 0.7-8.6% strontium carbonate, 1.9-12.0% yttrium oxide and the balance silicon nitride; forming a shaped green-body of said mixture; decomposing said strontium carbonate to strontium oxide; sintering said green body to form a sintered body; and hot isostatically pressing said sintered body to form the densified article.
Claim 10
Dependent Claim
70 words
The article of claim 8 wherein said steps of sintering and hot isostatic pressing art the steps of: burying in a crucible said green body shape in a mixture of powders of silicon nitride, yttrium oxide, aluminum oxide and boron nitride; and heating said green body in a nitrogen atmosphere at temperatures in the range of 1800°-1900° C. at pressures of 0.7-2.1 MPa (100-300 psi) for 2 to 6 hours.
Claim 11
Dependent Claim
27 words
The article of claim 8 wherein said step of hot isostatically pressing comprises: isostatically pressing said body at 10.3-206 MPa (1.5-30 KSI) for 1 to 8 hours.
Claim 12
Dependent Claim
52 words
The article of claim 1 made by the steps of: mixing by weight 0.7-8.6% strontium carbonate 1.9-12.0% yttrium oxide and the balance silicon nitride; forming a shaped green-body of said mixture; sintering said green body to form a sintered body; and hot isostatically pressing said sintered body to form the densified article.
Claim 13
Dependent Claim
66 words
The article of claim 11 wherein said step of sitnering comprises the steps of: burying in a crucible said green body in a mixture of powders of silicon nitride, yttrium oxide, aluminum oxide and boron nitride; and heating said green body in an inert atmosphere at temperatures in the range of 1800°-1900° C. at pressures of 0.7 -2.1 MPa (100-300 psi) for 2 to 6 hours.
Claim 14
Dependent Claim
27 words
The article of claim 11 wherein said step of hot isostatically pressing comprises: isostatically pressing said body at 10.3-206.7 MPa (1.5-30 KSI) for 1 to 8 hours.
Claim 15
Dependent Claim
29 words
A silicon nitride based green body consisting essentially of a mixture of 0.7-8.6% strontium carbonate by weight, 1.9-12.0% yttrium oxide and the balance silicon nitride plus an organic binder.
Claim 16
Dependent Claim
29 words
A silicon nitride based green body consisting essentially of a mixture of 0.7-8.6% strontium carbonate by weight, 1.9-12.0% yttrium oxide and the balance silicon nitride plus an organic binder.
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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) | 1992-09-25 | 1993-03-27 | 1993-09-26 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-09-25 | 1997-03-27 | 1997-09-26 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-09-25 | 2001-03-27 | 2001-09-26 | $7700.00 | Window Closed / Lapsed |