US4351787A
Expired / Lapsed
US
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Process for sintering reaction bonded silicon nitride
Assignee: Fiat SpA
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Filing: 1978-12-18
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Granted: 1982-09-28
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Expires: 1998-12-18
Abstract
Abstract Sintered silicon nitride articles are prepared from a silicon nitride compact by forming a silicon powder containing one or more sintering additives for silicon nitride into a compact having at density of at least 1.3 g/cm3, said additives being present in the powder in an amount such as to ensure an additive content of from 0.5 to 20 wt. % in the silicon nitride compact, nitriding the silicon compact by heating under nitrogen gas blanket at a temperature not exceeding 1500 DEG C., to convert said silicon into reaction bonded silicon nitride, and sintering the reaction bonded silicon nitride compact by heating in a nitrogen gas atmosphere at a temperature of at least 1500 DEG C.
Inventors
- 👤 PierCarlo Martinengo
- 👤 Angelo Giachello
- 👤 Giuseppe Tommasini
- 👤 Paul Popper
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 11:16
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/591; C04B35/593; C04B35/5935; C04B35/622; C04B35/64; B; B22; B22F; B22F3/00; B22F3/10; B22F2003/1042
Claims Analysis
Total Claims: 14
Claim 1
Independent Claim
166 words
A process for increasing the density of a reaction bonded silicon nitride article, which comprises the steps of: forming a silicon powder compact consisting essentially of silicon powder and one or more sintering additives for silicon nitride, the compact having a density of at least 1.3 g/cm 3 , said additives being present in the silicon powder in an amount such as to ensure an additive content of from 0.5 to 20 wt.% in the silicon nitride compact wherein the sintering additives are selected from the group consisting of MgO, Y 2 O 3 , CeO 2 and mixtures thereof with Fe; nitriding the silicon compact by heating under nitrogen gas blanket at a temperature not exceeding 1500° C., to convert said silicon into reaction bonded silicon nitride, and sintering the reaction bonded silicon nitride compact by heating in a nitrogen gas atmosphere at a temperature of at least 1500° C., said sintering being in the substantial absence of mechanical pressure, whereby said density is increased.
Claim 2
Dependent Claim
166 words
A process for increasing the density of a reaction bonded silicon nitride article, which comprises the steps of: forming a silicon powder compact consisting essentially of silicon powder and one or more sintering additives for silicon nitride, the compact having a density of at least 1.3 g/cm 3 , said additives being present in the silicon powder in an amount such as to ensure an additive content of from 0.5 to 20 wt.% in the silicon nitride compact wherein the sintering additives are selected from the group consisting of MgO, Y 2 O 3 , CeO 2 and mixtures thereof with Fe; nitriding the silicon compact by heating under nitrogen gas blanket at a temperature not exceeding 1500° C., to convert said silicon into reaction bonded silicon nitride, and sintering the reaction bonded silicon nitride compact by heating in a nitrogen gas atmosphere at a temperature of at least 1500° C., said sintering being in the substantial absence of mechanical pressure, whereby said density is increased.
Claim 3
Dependent Claim
15 words
The process of claim 1, wherein the silicon powder contains MgO as a sintering additive.
Claim 4
Dependent Claim
19 words
The process of claim 1, wherein the silicon powder contains MgO and Y 2 O 3 as sintering additives.
Claim 5
Dependent Claim
18 words
The process of claim 1, wherein the silicon nitride compact contains from 1 to 15 wt.% of additives.
Claim 6
Dependent Claim
18 words
The process of claim 1, wherein the silicon powder has a particle size of from 0.1 to 44μ.
Claim 7
Dependent Claim
19 words
The process of claim 1, wherein the silicon compact has a density of at least 1.5 g/cm 3 .
Claim 8
Dependent Claim
19 words
The process of claim 1, wherein the nitriding step is carried out at a temperature not exceeding 1450° C.
Claim 9
Dependent Claim
20 words
The process of claim 1, wherein the silicon nitride compact has a density of at least 2.2 g/cm 3 .
Claim 10
Dependent Claim
21 words
The process of claim 1, wherein the sintering is carried out at a temperature of from 1500° C. to 2000° C.
Claim 11
Dependent Claim
31 words
The process of claim 1, wherein said one or more sintering additives for silicon nitride are present in an amount of from 3 to 10 wt.% in the silicon nitride compact.
Claim 12
Dependent Claim
30 words
The process according to claim 10, wherein nitriding is conducted at a temperature not exceeding 1450° C. and sintering is conducted at a temperature of 1500° C. to 2000° C.
Claim 13
Dependent Claim
39 words
The process according to claim 11, wherein said reaction bonded silicon nitride has a density of 2.5 to 2.6 g/cm 3 and said sintered reaction bonded silicon nitride compact has a density of at least 2.85 g/cm 3 .
Claim 14
Dependent Claim
31 words
The process of claim 1, wherein the sintering is carried out while the nitrided silicon compact is embedded in a protective powder comprising Si 3 N 4 , BN and MgO.
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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) | 1985-09-27 | 1986-03-29 | 1986-09-28 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1989-09-27 | 1990-03-29 | 1990-09-28 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1993-09-27 | 1994-03-29 | 1994-09-28 | $7700.00 | Window Closed / Lapsed |