Patent US3954483A successfully refreshed from Google Patents.
US3954483A
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US
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Dense polycrystalline silicon carbide
Assignee: General Electric Co
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Filing: 1974-01-08
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Granted: 1976-05-04
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Expires: 1994-01-08
Abstract
Abstract A dense silicon carbide material having improved electrically conducting properties is disclosed which is prepared by forming a homogeneous dispersion of silicon carbide, a sufficient amount of boron nitride, and optionally a boron containing additive and hot pressing the dispersion at a sufficient temperature and pressure whereby a dense substantially nonporous ceramic is formed. The silicon carbide material can be machined by electrical discharge machining or by electrochemical machining.
Inventors
- 👤 Svante Prochazka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 08:06
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565; C04B35/575
Claims Analysis
Total Claims: 9
Claim 1
Independent Claim
71 words
A Method of making a dense silicon carbide ceramic comprising the steps of a. forming a substantially homogeneous dispersion of a submicron powder of silicon carbide and 0.7-3.5% by weight of boron nitride, and b. hot pressing the dispersion in an inert atmosphere at a temperature of about 1,950°-2,050°C. and at a pressure of about 5,000-10,000 psi for a sufficient time to produce a ceramic product of at least 98% density.
Claim 2
Independent Claim
71 words
A Method of making a dense silicon carbide ceramic comprising the steps of a. forming a substantially homogeneous dispersion of a submicron powder of silicon carbide and 0.7-3.5% by weight of boron nitride, and b. hot pressing the dispersion in an inert atmosphere at a temperature of about 1,950°-2,050°C. and at a pressure of about 5,000-10,000 psi for a sufficient time to produce a ceramic product of at least 98% density.
Claim 3
Dependent Claim
28 words
The method of claim 1, wherein said time is about 10-60 minutes and the inert atmosphere is one selected from the group consisting of argon, helium and nitrogen.
Claim 4
Dependent Claim
18 words
The method of claim 2, wherein said homogeneous dispersion additionally contains up to 1% by weight of boron.
Claim 5
Dependent Claim
30 words
The method of claim 3, wherein the inert atmosphere is argon, the temperature is about 1,950° C., the pressure is about 10,000 psi and the time is about 30 minutes.
Claim 6
Dependent Claim
47 words
A dense silicon carbide ceramic consisting essentially of β-silicon carbide and 0.7-3.5% by weight of boron nitride, the ceramic being substantially pore free, having a density of at least 98% of the theoretical density for silicon carbide, and having a maximum resistivity of about 50 ohm centimeters.
Claim 7
Dependent Claim
47 words
A dense silicon carbide ceramic consisting essentially of β-silicon carbide and 0.7-3.5% by weight of boron nitride, the ceramic being substantially pore free, having a density of at least 98% of the theoretical density for silicon carbide, and having a maximum resistivity of about 50 ohm centimeters.
Claim 8
Dependent Claim
22 words
The ceramic of claim 5, containing about 2% by weight of boron nitride and having a resistivity of about 3 ohm centimeters.
Claim 9
Dependent Claim
60 words
The ceramic of claim 5 in which the grain size is abput 2.5 microns, the flexural strength at 25°C. is about 69,000 pounds per square inch and at 1500°C. is about 77,000 pounds per square inch, and the creep rate strain in bending at 1550°C. and 30,000 pounds per square inch is about 4 × 10 - 9 per second.
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) | 1979-05-04 | 1979-11-03 | 1980-05-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1983-05-04 | 1983-11-03 | 1984-05-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1987-05-04 | 1987-11-03 | 1988-05-04 | $7700.00 | Window Closed / Lapsed |