US3811928A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Silicon nitride ceramics
Assignee: United Kingdom Atomic Energy Authority
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Filing: 1971-10-15
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Granted: 1974-05-21
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Expires: 1991-10-15
Abstract
Abstract Shaped ceramic objects of silicon nitride are protected from oxidation by a coating comprising silica and boric oxide. The coating may be formed by heating a shaped mixture of silicon nitride and boron nitride in air to convert part to silica and boric oxide and causing a silica/boric oxide glass to flux and protect the object from further oxidation. The boron may be incorporated during oxidation but is preferably added to the silicon before nitriding.
Inventors
- 👤 J Henney
- 👤 J Jones
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 21:29
CPC Classifications
C; C04; C04B; C04B41/00; C04B41/45; C04B41/50; C04B41/5022; C03; C03C; C03C1/00; C04B35/00; C04B35/515; C04B35/58; C04B35/583; C04B35/584; C04B35/591
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
29 words
A ceramic shaped object as claimed in claim 1, comprising up to 10 percent of one or more of Fe, Mg, Al, Al2O3, MgO, CaO, BaO, ZnO and ZrO2.
Claim 2
Dependent Claim
78 words
A ceramic shaped object consisting essentially of a matrix of Si3N4, in which there is incorporated BN in an amount of from 1 percent to 20 percent of boron by weight on the weight of the silicon, protected from oxidation by a gas-impermeable surface layer comprising SiO2 and B2O3, wherein the surface layer constitutes from 1 percent to 5 percent of the weight of the article and contains from 1 percent to 20 percent by weight of B2O3.
Claim 3
Dependent Claim
29 words
A ceramic shaped object as claimed in claim 3, comprising up to 10 percent of one or more of Fe, Mg, Al, Al2O3, MgO, CaO, BaO, ZnO and ZrO2.
Claim 4
Dependent Claim
59 words
A ceramic shaped object consisting essentially of a mixture of Si3N4 and BN protected from oxidation and bonded throughout by means of a glass comprising SiO2 and B2O3, wherein a. the weight of boron is from 1 percent to 20 percent of the weight of the silicon, and b. the weight ratio of (SiO2/B2O3):(Si3N4/BN) is from 50:50 to 5:95.
Claim 5
Dependent Claim
29 words
A ceramic shaped object as claimed in claim 5, comprising up to 10 percent of one or more of Fe, Mg, Al, Al2O3, MgO, CaO, BaO, ZnO and ZrO2.
Claim 6
Dependent Claim
51 words
A ceramic shaped object consisting essentially of Si3N4 protected from oxidation and bonded throughout by means of a glass comprising SiO2 and B2O3, wherein a. the weight ratio of (SiO2/B2O3):Si3N4 is from 50:50 to 5:95, and b. the said glass contains from 1 percent to 20 percent by weight of B2O3.
Claim 7
Dependent Claim
29 words
A ceramic shaped object as claimed in claim 7, comprising up to 10 percent of one or more of Fe, Mg, Al, Al2O3, MgO, CaO, BaO, ZnO and ZrO2.
References Cited (Backward Citations)
No citation records indexed.
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1977-05-20 | 1977-11-19 | 1978-05-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1981-05-20 | 1981-11-19 | 1982-05-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1985-05-20 | 1985-11-19 | 1986-05-21 | $7700.00 | Window Closed / Lapsed |