US4462816A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method for making sintered silicon nitride articles
Assignee: Osram Sylvania Inc
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Filing: 1983-06-08
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Granted: 1984-07-31
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Expires: 2003-06-08
Abstract
Abstract In the manufacture of sintered silicon nitride articles by hot isostatic pressing, multiple silicon nitride parts are encapsulated within a single capsule for the pressing operation. Suitable spacers placed between the parts ease separation thereof after sintering.
Inventors
- 👤 Robert W. Wolfe
- 👤 Joseph J. Cleveland
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 22:51
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64; C04B35/645; C04B35/6455; C04B35/515; C04B35/58; C04B35/584; C04B35/593
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
126 words
In the process of making a sintered silicon nitride article by pressing a preform from silicon nitride powder and then isostatically pressing the preform at high temperature and high pressure to make the sintered silicon nitride article, the improvement which comprises the steps of assembling a plurality of such preforms in a stack with spacers separating the preforms from each other, the spacers comprising material that is inert with respect to the silicon nitride preforms and having a melting point above the isostatic pressing temperature, enclosing the stack in a sealed glass capsule, hot isostatically pressing the glass capsule, removing the glass from around the stack, and then separating the sintered silicon nitride articles from each other, the separating step being eased because of the spacers.
Claim 2
Dependent Claim
126 words
In the process of making a sintered silicon nitride article by pressing a preform from silicon nitride powder and then isostatically pressing the preform at high temperature and high pressure to make the sintered silicon nitride article, the improvement which comprises the steps of assembling a plurality of such preforms in a stack with spacers separating the preforms from each other, the spacers comprising material that is inert with respect to the silicon nitride preforms and having a melting point above the isostatic pressing temperature, enclosing the stack in a sealed glass capsule, hot isostatically pressing the glass capsule, removing the glass from around the stack, and then separating the sintered silicon nitride articles from each other, the separating step being eased because of the spacers.
Claim 3
Dependent Claim
18 words
The process of claim 1 wherein the spacers have the same shape as the preforms but are thinner.
Claim 4
Dependent Claim
36 words
The process of claim 1 wherein the preforms are made by pressing the silicon nitride powder in a die and the spacers are made by pressing the spacer material in powder form in the same die.
Claim 5
Dependent Claim
10 words
The process of claim 1 wherein the spacer boron nitride.
Claim 6
Dependent Claim
15 words
The process of claim 1 wherein the spacer material comprises spinel coated with boron nitride.
Claim 7
Dependent Claim
15 words
The process of claim 1 wherein the spacer material comprises alumina coated with boron nitride.
Claim 8
Dependent Claim
15 words
The process of claim 1 wherein the spacer material comprises magnesia coated with boron nitride.
Claim 9
Dependent Claim
15 words
The process of claim 1 wherein the spacer material comprises zirconia coated with boron nitride.
Claim 10
Dependent Claim
17 words
The process of claim 1 wherein the spacer material comprises a rare earth oxide coated with zirconia.
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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) | 1987-07-31 | 1988-01-30 | 1988-07-31 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-07-31 | 1992-01-30 | 1992-07-31 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-07-31 | 1996-01-30 | 1996-07-31 | $7700.00 | Window Closed / Lapsed |