US4643858A
Expired / Lapsed
US
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Process for preparation of sintered silicon nitride body
Assignee: Kyocera Corp
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Filing: 1985-03-05
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Granted: 1987-02-17
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Expires: 2005-03-05
Abstract
Abstract In preparing a sintered silicon nitride body by hot isostatic pressing, if a green molded body of silicon nitride and a sintering aid is coated with a compound of high melting point cyrstalline powder (sintering aids of silicon nitride), said crystalline compound works as a pressure media on HIP treatment and is present in the surface of the sintered body. By the presence of this crystal, hot isostatic pressing of this dual density compact mentioned above results surface compression stress, which results not only the strength at room temperature but also the strength at high temperatures is highly improved.
Inventors
- 👤 Michitaka Mizutani
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 14:58
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/622; C04B35/64; C04B35/645; C04B35/6455
Claims Analysis
Total Claims: 20
Claim 1
Independent Claim
135 words
A process for the preparation of a sintered silicon nitride body, which comprises the steps of (i) molding a silicon nitride powder into a predetermined shape to obtain a green molded body, (ii) reacting by heating a mixture of silicon nitride and an oxide of an element of the group IIIa of the Periodic Table to prepare a compound of the N-melilite type crystal structure and dispersing said compund in a liquid medium to form a slurry, (iii) coating the slurry formed at the step (ii) on the surface of the green molded body obtained at the step (i), (iv) preliminarily sintering the coated molded body obtained at the step (iii) in an inert atmosphere, and (v) subjecting the preliminarily sintered body obtained at the step (iv) to hot isostatic pressing in an inert atmosphere.
Claim 2
Dependent Claim
135 words
A process for the preparation of a sintered silicon nitride body, which comprises the steps of (i) molding a silicon nitride powder into a predetermined shape to obtain a green molded body, (ii) reacting by heating a mixture of silicon nitride and an oxide of an element of the group IIIa of the Periodic Table to prepare a compound of the N-melilite type crystal structure and dispersing said compund in a liquid medium to form a slurry, (iii) coating the slurry formed at the step (ii) on the surface of the green molded body obtained at the step (i), (iv) preliminarily sintering the coated molded body obtained at the step (iii) in an inert atmosphere, and (v) subjecting the preliminarily sintered body obtained at the step (iv) to hot isostatic pressing in an inert atmosphere.
Claim 3
Dependent Claim
135 words
A process for the preparation of a sintered silicon nitride body, which comprises the steps of (i) molding a silicon nitride powder into a predetermined shape to obtain a green molded body, (ii) reacting by heating a mixture of alumina and an oxide of an element of the group IIIa of the Periodic Table to prepare a compound of the composite oxide type crystal structure and dispersing said compound in a liquid medium to form a slurry, (iii) coating the slurry formed at the step (ii) on the surface of the green molded body obtained at the step (i), (iv) preliminary sintering the coated molded body obtained at the step (iii) in an inert atmosphere, and (v) subjecting the preliminarily sintered body obtained at the step (iv) to hot isostatic pressing in an inert atmosphere.
Claim 4
Dependent Claim
135 words
A process for the preparation of a sintered silicon nitride body, which comprises the steps of (i) molding a silicon nitride powder into a predetermined shape to obtain a green molded body, (ii) reacting by heating a mixture of alumina and an oxide of an element of the group IIIa of the Periodic Table to prepare a compound of the composite oxide type crystal structure and dispersing said compound in a liquid medium to form a slurry, (iii) coating the slurry formed at the step (ii) on the surface of the green molded body obtained at the step (i), (iv) preliminary sintering the coated molded body obtained at the step (iii) in an inert atmosphere, and (v) subjecting the preliminarily sintered body obtained at the step (iv) to hot isostatic pressing in an inert atmosphere.
Claim 5
Dependent Claim
48 words
The process according to claim 1 wherein the oxide of an element of the group IIIa of the Periodic Table is selected from the group consisting of Y 2 O 3 , La 2 O 3 , Yb 2 O 3 , and Sm 2 O 3 .
Claim 6
Dependent Claim
43 words
The process according to claim 1 wherein the silicon nitride (Si 3 N 4 ) and the oxide of the element of group IIIa of the Periodic Table (R 2 O 3 ) are mixed at a molar ratio from 1:3 to 3:1.
Claim 7
Dependent Claim
40 words
The process according to claim 4 wherein the silicon nitride (Si 3 N 4 ) and the oxide of the element of group IIIa of the Period Table (R 2 O 3 ) are mixed at approximately an equimolar ratio.
Claim 8
Dependent Claim
33 words
The process according to claim 1 wherein the heating of the mixture is at a heating temperature higher than 1400° C., and wherein the compound has a melting point higher than 1600° C.
Claim 9
Dependent Claim
42 words
The process according to claim 1 wherein the amount, as solids, of the coating of slurry formed on the surface of the green molded body at step (iii) is 0.01 to 0.5 part by weight of the silicon nitride green molded body.
Claim 10
Dependent Claim
30 words
The process according to claim 1 wherein the (iv) preliminarily sintering is carried out at a temperature of 1500° to 1800° C. for a period of 0.5 to 5 hours.
Claim 11
Dependent Claim
12 words
The process according to claim 1 wherein the inert atmosphere is nitrogen.
Claim 12
Dependent Claim
12 words
The process acording to claim 1 wherein the inert atmosphere is argon.
Claim 13
Dependent Claim
48 words
The process according to claim 2 wherein the oxide of an element of the group IIIa of the Periodic Table is selected from the group consisting of Y 2 O 3 , La 2 O 3 , Yb 2 O 3 , and Sm 2 O 3 .
Claim 14
Dependent Claim
37 words
The process according to claim 2 wherein the alumina and the oxide of the element of group IIIa of the Periodic Table (R 2 O 3 ) are mixed at a molar ratio from 1:3 to 3:1.
Claim 15
Dependent Claim
34 words
The process according to claim 12 wherein the alumina and the oxide of the element of group IIIa of the Period Table (R 2 O 3 ) are mixed at approximately an equimolar ratio.
Claim 16
Dependent Claim
22 words
The process according to claim 2 wherein the heating of the mixture is at a heating temperature of 1300° to 1800° C.
Claim 17
Dependent Claim
42 words
The process according to claim 2 wherein the amount, as solids, of the coating of slurry formed on the surface of the green molded body of step (iii) is 0.01 to 0.5 part by weight of the silicon nitride green molded body.
Claim 18
Dependent Claim
30 words
The process according to claim 2 wherein the (iv) preliminarily sintering is carried out at a temperature of 1500° to 1800° C. for a period of 0.5 to 5 hours.
Claim 19
Dependent Claim
12 words
The process according to claim 2 wherein the inert atmosphere is nitrogen.
Claim 20
Dependent Claim
12 words
The process according to claim 2 wherein the inert atmosphere is argon.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1990-02-16 | 1990-08-18 | 1991-02-17 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-02-16 | 1994-08-18 | 1995-02-17 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-02-16 | 1998-08-18 | 1999-02-17 | $7700.00 | Window Closed / Lapsed |