US4855262A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Method of manufacturing silicon nitride composition reinforced with silicon carbide whiskers having silicon oxide coating
Assignee: Battelle Memorial Institute Inc
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Filing: 1988-02-12
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Granted: 1989-08-08
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Expires: 2008-02-12
Abstract
Abstract Reinforcing Si3N4 ceramics with preoxidized SiC whiskers improves flexural strength and WEIBULL modulus over that of comparable bulk Si3N4 ceramics or Si3N4 ceramics reinforced with neat SiC whiskers. Hot isostatic pressing further improves the physical properties of said ceramics.
Inventors
- 👤 Dominique Richon
- 👤 Olivier de Pous
- 👤 Pierre Fontaine
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 05:54
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64; C04B35/645; C04B35/6455; C04B35/515; C04B35/58; C04B35/584; C04B35/593; C04B35/71; C04B35/78; C04B35/80; Y; Y10; Y10T; Y10T428/00; Y10T428/29; Y10T428/2913; Y10T428/2918; Y10T428/2933; Y10T428/2938; Y10T428/294; Y10T428/2942; Y10T428/2949
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
92 words
A method for the preparation of a silicon nitride pulverulent composition comprising the steps of: Division Application of RICHON et al -- S.N. 124,597 (i) oxidizing SiC whiskers by heat treatment; (ii) ball milling α-Si 3 N 4 powder with a sintering aid in the presence of a dispersing phase solvent carrier; (iii) admixing said SiC whiskers by slow rotation on rolls without balls so as not to break the fibers and using a high proportion of the dispersing phase; and (iv) evaporating the solvent under rotation and granulating the remaining solid.
Claim 2
Independent Claim
92 words
A method for the preparation of a silicon nitride pulverulent composition comprising the steps of: Division Application of RICHON et al -- S.N. 124,597 (i) oxidizing SiC whiskers by heat treatment; (ii) ball milling α-Si 3 N 4 powder with a sintering aid in the presence of a dispersing phase solvent carrier; (iii) admixing said SiC whiskers by slow rotation on rolls without balls so as not to break the fibers and using a high proportion of the dispersing phase; and (iv) evaporating the solvent under rotation and granulating the remaining solid.
Claim 3
Dependent Claim
25 words
The method of claim 1, wherein said heat treatment comprises heating said SiC whiskers in air at from 950°-1050° C. for 1 to 3 hours.
Claim 4
Dependent Claim
56 words
A method according to claim 1 for making a sintered silicon nitride article comprising the further steps of: (i) isostatically molding said granulated solid into a green body at a pressure of from 2000-4000 bar; and (ii) sintering said green body at from 1750°-1800° C. under nitrogen for a period of from 5 to 30 minutes.
Claim 5
Dependent Claim
21 words
The method of claim 1, wherein heat-pretreatment of the SiC whiskers includes heating 0.1-5 hrs in air at about 1000° C.
Claim 6
Dependent Claim
20 words
The method of claim 1, which comprises using, as a dispersing phase solvent carrier, a mixture of tert.butanol and petroleum-ether.
Claim 7
Dependent Claim
18 words
The method of claim 1, which comprises using in step (ii) 5-12% by weight of the sintering aid.
Claim 8
Dependent Claim
18 words
The method of claim 1, which comprises effecting the granulation of step (iv) on a 500 μm grating.
Claim 9
Dependent Claim
40 words
The method of claim 1, wherein the ball-milling step (ii) is effected by using Si 3 N 4 balls and rotating at about 80-150 rpm, while the admixing step (iii) is effected by rotating at 30-40 rpm for 1-6 hrs.
Claim 10
Independent Claim
98 words
A method of preparing a silicon nitride pulverulent composition comprising the steps of: (i) heating SiC whishers at a temperature of from 950°-1050° C. for a period of time sufficient to provide a thin layer of SiO 2 on said whiskers; (ii) ball milling α-Si 3 N 4 powder with a sintering aid in the presence of a dispersing phase solvent carrier; (iii) homogeneously blending said heat-treated whiskers with the α-Si 3 N 4 powder, sintering aid and solvent mixture under conditions which avoid breaking the whiskers; and (iv) drying and sizing the blend to form a powder.
Claim 11
Independent Claim
98 words
A method of preparing a silicon nitride pulverulent composition comprising the steps of: (i) heating SiC whishers at a temperature of from 950°-1050° C. for a period of time sufficient to provide a thin layer of SiO 2 on said whiskers; (ii) ball milling α-Si 3 N 4 powder with a sintering aid in the presence of a dispersing phase solvent carrier; (iii) homogeneously blending said heat-treated whiskers with the α-Si 3 N 4 powder, sintering aid and solvent mixture under conditions which avoid breaking the whiskers; and (iv) drying and sizing the blend to form a powder.
Claim 12
Dependent Claim
27 words
The process of claim 3, comprising an additional stage consisting of: (3) Subjecting the sintered article to hot isostatic pressing (HIP) at 1650° C. under 2000 bar.
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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) | 1992-08-07 | 1993-02-06 | 1993-08-08 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-08-07 | 1997-02-06 | 1997-08-08 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-08-07 | 2001-02-06 | 2001-08-08 | $7700.00 | Window Closed / Lapsed |