US4701427A
Expired / Lapsed
US
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Sintered silicon carbide ceramic body of high electrical resistivity
Assignee: Stemcor Corp
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Filing: 1985-10-17
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Granted: 1987-10-20
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Expires: 2005-10-17
Abstract
Abstract Sintered silicon carbide body having a D.C. electrical resistivity of at least 108 Ohm cm at 25 DEG C., a density of at least 2.95 g/cm3 is formed upon sintering in a nitrogenous atmosphere at a temperature of about 2250 DEG C. or greater, a shaped body composed essentially of carbon or carbon source material in amount sufficient to provide up to 2.5 percent uncombined carbon; from about 0.4 to about 2.0 percent boron carbide; up to 25 percent of temporary binder and a balance of silicon carbide which is predominantly alpha-phase. The shaped body may additionally include other sintering aids such as BN or Al without destruction of desired high electrical resistivity.
Inventors
- 👤 Wolfgang D. G. Boecker
- 👤 Laurence N. Hailey
- 👤 Carl H. McMurtry
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 05:49
CPC Classifications
H; H10; H10W; H10W70/00; H10W70/60; H10W70/67; H10W70/69; H10W70/692; C; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565; H01; H01B; H01B3/00; H01B3/02; H01B3/12
Claims Analysis
Total Claims: 39
Claim 1
Independent Claim
67 words
An electrically insulating ceramic material comprising a sintered body composed essentially of polycrystalline, sintered silicon carbide, having between at least a portion of the silicon carbide grains thereof areas of uncombined carbon which areas contain both boron and nitrogen, and within the grains of silicon carbide, boron nitride precipitates, said sintered body having a D.C. electrical resistivity of 10 9 Ohm cm or greater at 25° C.
Claim 2
Dependent Claim
67 words
An electrically insulating ceramic material comprising a sintered body composed essentially of polycrystalline, sintered silicon carbide, having between at least a portion of the silicon carbide grains thereof areas of uncombined carbon which areas contain both boron and nitrogen, and within the grains of silicon carbide, boron nitride precipitates, said sintered body having a D.C. electrical resistivity of 10 9 Ohm cm or greater at 25° C.
Claim 3
Dependent Claim
65 words
An electricity insulating ceramic material comprising a sintered body composed essentially of: (a) up to 1.0 percent uncombined carbon; (b) 0.3 to 1.0 percent boron; (c) 0.03 to 0.8 percent nitrogen; (d) and a balance of silicon carbide; said sintered body having a density of at least 2.95 g/cm 3 and a D.C. electrical resistivity of at least 10 9 Ohm cm at 25° C.
Claim 4
Dependent Claim
65 words
An electricity insulating ceramic material comprising a sintered body composed essentially of: (a) up to 1.0 percent uncombined carbon; (b) 0.3 to 1.0 percent boron; (c) 0.03 to 0.8 percent nitrogen; (d) and a balance of silicon carbide; said sintered body having a density of at least 2.95 g/cm 3 and a D.C. electrical resistivity of at least 10 9 Ohm cm at 25° C.
Claim 5
Dependent Claim
50 words
A sintered body according to claim 1, further composed essentially of: (a) up to 1.0 percent uncombined carbon., (b) 0.3 to 1.0 percent boron., (c) 0.03 to 0.8 percent nitrogen; (d) and a balance of silicon carbide; said sintered body having a density of at least 2.95 g/cm 3 .
Claim 6
Dependent Claim
16 words
A sintered body according to claim 2 having a thermal conductivity of at least 55 W/mK.
Claim 7
Dependent Claim
15 words
A sintered according to claim 3 having a thermal conductivity of at least 55 W/mK.
Claim 8
Dependent Claim
16 words
A sintered body according to claim 2 additionally composed essentially of up to 0.5 percent oxygen.
Claim 9
Dependent Claim
17 words
A sintered body according to claim 1 having a density of at least 3.0 g/cm 3 .
Claim 10
Dependent Claim
17 words
A sintered body according to claim 4 having a density of at least 3.0 g/cm 3 .
Claim 11
Dependent Claim
20 words
A sintered body according to claim 2 composed essentially of not more than 0.6 percent nitrogen and 0.8 percent boron.
Claim 12
Dependent Claim
20 words
A sintered body according to claim 3 composed essentially of not more than 0.6 percent nitrogen and 0.8 percent boron.
Claim 13
Dependent Claim
39 words
A sintered body according to claim 3 having between 0.03 and 0.45 percent nitrogen and between 0.50 and 0.85 percent boron; said sintered body having a D.C. electrical resistivity of at least 10 10 Ohm cm at 25° C.
Claim 14
Dependent Claim
17 words
A sintered body according to claim 1 wherein said silicon carbide consists essentially of alpha-type silicon carbide.
Claim 15
Dependent Claim
17 words
A sintered body according to claim 2 wherein said silicon carbide consists essentially of alpha-type silicon carbide.
Claim 16
Dependent Claim
36 words
A sintered body according to claim 1 having a density of at least 3.10 g/cm 3 , an electrical resistivlty of at least 10 11 Ohm cm and a thermal conductivity of at least 65 W/mK.
Claim 17
Dependent Claim
36 words
A sintered body according to claim 2 having a density of at least 3.10 g/cm 3 , an electrical resistivity of at least 10 11 Ohm cm and a thermal conductivity of at least 65 W/mK.
Claim 18
Dependent Claim
20 words
A sintered body according to claim 1 produced by pressureless sintering at a temperature of about 2250° C. or greater.
Claim 19
Dependent Claim
20 words
A sintered body according to claim 2 produced by pressureless sintering at a temperature of about 2250° C. or greater.
Claim 20
Dependent Claim
21 words
A sintered body according to claim 1 produced by pressureless sintering at a temperature of between about 2275° and 2300° C.
Claim 21
Dependent Claim
21 words
A sintered body according to claim 2 produced by pressureless sintering at a temperature of between about 2275° and 2300° C.
Claim 22
Dependent Claim
33 words
A sintered body according to claim 1 having at 10 MHz and 25° C., a dielectric constant of not more than about 25 and a dissipation factor of not more than about 0.2.
Claim 23
Dependent Claim
33 words
A sintered body according to claim 2 having at 10 MHz and 25° C., a dielectric constant of not more than about 25 and a dissipation factor of not more than about 0.2.
Claim 24
Dependent Claim
103 words
A sintered body according to claim 1 produced by pressureless sintering in a nitrogenous atmosphere, at a temperature of about 2250° C. or greater, a shaped body having a density before sintering of at least about 1.45 g/cm 3 , the shaped body composed essentially of: (a) carbon or carbon source material in amount sufficient to provide upon in situ decomposition up to 2.5 percent uncombined carbon; (b) from about 0.4 to about 2.0 percent boron carbide calculated as B 4 C; (c) a balance of silicon carbide which is predominately alpha-phase; and, in addition, (d) up to 25 percent of temporary binder.
Claim 25
Dependent Claim
104 words
A sintered body according to claim 2 produced by pressureless sintering in a nitrogenous atmosphere, at a temperature of about 2250° C. or greater, a shaped body having a density before sintering of at least about 1.45 g/cm 3 , the shaped body composed essentially of: (a) carbon or carbon source material in amount sufficient to provide upon in situ decomposition up to 2.5 percent uncombined carbon; (b) from about 0.4 to about 2.0 percent boron carbide calculated as B 4 C; and (c) a balance of silicon carbide which is predominately alpha-phase; and, in addition, (d) up to 25 percent of temporary binder.
Claim 26
Dependent Claim
17 words
A sintered body according to claim 22 wherein sintering is conducted between about 2275° and 2350° C.
Claim 27
Dependent Claim
24 words
A sintered body according to claim 1 having at 10 8 or more Hz and 25° C. a dielectric constant of less than 15.
Claim 28
Dependent Claim
24 words
A sintered body according to claim 2 having at 10 8 or more Hz and 25° C. a dielectric constant of less than 15.
Claim 29
Dependent Claim
22 words
A sintered body according to claim 1 having at 10 6 Hz and 25° C. a dissipation factor of less than 0.2.
Claim 30
Dependent Claim
22 words
A sintered body according to claim 2 having at 10hu 6 Hz and 25° C. a dissipation factor of less than 0.2.
Claim 31
Dependent Claim
24 words
A sintered body according to claim 1 having at 10 8 or more Hz and 25° C. a dissipation factor of less than 0.1.
Claim 32
Dependent Claim
24 words
A sintered body according to claim 2 having at 10 8 or more Hz and 25° C. a dissipation factor of less than 0.1.
Claim 33
Dependent Claim
163 words
A process for the production of a silicon carbide ceramic body having a D.C. electrical resistivity of at least 10 8 Ohm cm at 25° C., comprising: (a) forming a shaped body having a density, before sintering, of at least about 1.45 g/cm 3 , the shaped body composed essentially of: (i) carbon or carbon source material in amount sufficient to provide upon in situ decomposition up to 2.5 percent uncombined carbon; (ii) from about 0.4 to about 2.0 percent boron carbide calculated as B 4 C. (iii) a balance of silicon carbide which is predominately alpha-phase; and, in addition, (iv) up to 25 percent of temporary binder, and (b) sintering said shaped body under substantially pressureless conditions in a nitrogenous atmosphere at a temperature of about 2250° C. or greater, for a time sufficient to produce a sintered body having a density of at least 2.95 g/cm 3 and an electrical resistivity of at least 10 8 Ohm cm at 25° C.
Claim 34
Dependent Claim
163 words
A process for the production of a silicon carbide ceramic body having a D.C. electrical resistivity of at least 10 8 Ohm cm at 25° C., comprising: (a) forming a shaped body having a density, before sintering, of at least about 1.45 g/cm 3 , the shaped body composed essentially of: (i) carbon or carbon source material in amount sufficient to provide upon in situ decomposition up to 2.5 percent uncombined carbon; (ii) from about 0.4 to about 2.0 percent boron carbide calculated as B 4 C. (iii) a balance of silicon carbide which is predominately alpha-phase; and, in addition, (iv) up to 25 percent of temporary binder, and (b) sintering said shaped body under substantially pressureless conditions in a nitrogenous atmosphere at a temperature of about 2250° C. or greater, for a time sufficient to produce a sintered body having a density of at least 2.95 g/cm 3 and an electrical resistivity of at least 10 8 Ohm cm at 25° C.
Claim 35
Dependent Claim
39 words
The process of claim 31 wherein the shaped body is composed essentially of up to 2 percent uncombined carbon; from about 0.5 to 1.5 percent boron carbide; sintering said shaped body at between about 2275° C. and 2350° C.
Claim 36
Dependent Claim
24 words
The process of claim 32 wherein flowing nitrogen is introduced during the sintering process in an amount of at least 50 percent by volume.
Claim 37
Dependent Claim
59 words
The process of claim 31 wherein the shaped body is composed essentially of about 1 percent uncombined carbon derived from carbon source material; about 1 percent boron carbide; sintering said shaped body at a temperature and for a time sufficient to produce a sintered body having an electrical resistivity of at least 10 10 Ohm cm at 25° C.
Claim 38
Dependent Claim
36 words
An electrically insulating ceramic material comprising a sintered boyd composed essentially of polycrystalline, pressureless sintered slicon carbide, said sintered body having a D.C. electrically resistivity of at least about 10 10 Ohm cm at 25° C.
Claim 39
Dependent Claim
36 words
An electrically insulating ceramic material comprising a sintered boyd composed essentially of polycrystalline, pressureless sintered slicon carbide, said sintered body having a D.C. electrically resistivity of at least about 10 10 Ohm cm at 25° C.
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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) | 1990-10-19 | 1991-04-20 | 1991-10-20 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1994-10-19 | 1995-04-20 | 1995-10-20 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1998-10-19 | 1999-04-20 | 1999-10-20 | $7700.00 | Window Closed / Lapsed |