US4004934A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Sintered dense silicon carbide
Assignee: General Electric Co
•
Filing: 1976-04-22
•
Granted: 1977-01-25
•
Expires: 1996-04-22
Abstract
Abstract A method of making a dense silicon carbide ceramic is disclosed involving the steps of homogeneously dispersing silicon carbide with a sufficient amount of a boron containing additive and a carbonaceous additive, forming the powder mixture into a shaped green body and then sintering the body in a controlled atmosphere and in the absence of external pressure at a temperature of about 1900°-2100° C. such that density of the body is at least 85% of the theoretical density of silicon carbide. The complex shaped silicon carbide product formed thereby is also disclosed.
Inventors
- 👤 Svante Prochazka
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-31 14:32
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/622; C04B35/64; C04B35/515; C04B35/56; C04B35/565
Claims Analysis
Total Claims: 30
Claim 1
Independent Claim
122 words
A method of making a pre-shaped dense sintered silicon carbide ceramic article comprising the steps of: a. forming a homogeneous dispersion of a submicron powder of 1. β-silicon carbide, 2. a boron containing compound in an amount equivalent to about 0.3-3.0% by weight of boron based on said silicon carbide, and 3. an elemental carbon source selected from the group consisting of elemental carbon and a carbonaceous additive in an amount equivalent to 0.1-1.0% by weight of elemental carbon based on said silicon carbide, b. shaping the homogeneous dispersion into a green body substantially of the form of said desired final pre-shaped sintered article and of dimensions larger than those of said desired sintered article by the amount of sintering shrinkage, and
Claim 2
Independent Claim
122 words
A method of making a pre-shaped dense sintered silicon carbide ceramic article comprising the steps of: a. forming a homogeneous dispersion of a submicron powder of 1. β-silicon carbide, 2. a boron containing compound in an amount equivalent to about 0.3-3.0% by weight of boron based on said silicon carbide, and 3. an elemental carbon source selected from the group consisting of elemental carbon and a carbonaceous additive in an amount equivalent to 0.1-1.0% by weight of elemental carbon based on said silicon carbide, b. shaping the homogeneous dispersion into a green body substantially of the form of said desired final pre-shaped sintered article and of dimensions larger than those of said desired sintered article by the amount of sintering shrinkage, and
Claim 3
Dependent Claim
59 words
c. sintering the green body in an inert atmosphere chemically-inert with respect to silicon carbide at atmospheric pressure or below atmospheric pressure at a temperature of about 1900° -2100° C until the ceramic article has a density of at least 85% of theoretical, said carbonaceous additive being pyrolyzable to produce said elemental carbon at a temperature below sintering temperature.
Claim 4
Dependent Claim
59 words
c. sintering the green body in an inert atmosphere chemically-inert with respect to silicon carbide at atmospheric pressure or below atmospheric pressure at a temperature of about 1900° -2100° C until the ceramic article has a density of at least 85% of theoretical, said carbonaceous additive being pyrolyzable to produce said elemental carbon at a temperature below sintering temperature.
Claim 5
Dependent Claim
12 words
The method of claim 1 wherein said boron compound is elemental boron.
Claim 6
Dependent Claim
12 words
The method of claim 1 wherein said boron compound is boron carbide.
Claim 7
Dependent Claim
14 words
The method of claim 1 wherein said green body is formed by slip casting.
Claim 8
Dependent Claim
23 words
The method of claim 1 wherein said atmosphere is a member selected from the group consisting of argon, helium, nitrogen and mixtures thereof.
Claim 9
Dependent Claim
10 words
The method of claim 1 wherein said atmosphere is nitrogen.
Claim 10
Dependent Claim
26 words
The method of claim 1 wherein prior to sintering, the green body is subjected to a prefiring step and the prefired body is machined to shape.
Claim 11
Independent Claim
179 words
A method of making a pre-shaped dense sintered silicon carbide ceramic article comprising the steps of: a. forming a substantially homogeneous first dispersion of a submicron powder of β-silicon carbide, a boron containing additive in an amount equivalent to about 0.3-3.0% by weight of boron based on said silicon carbide, b. incorporating in said first dispersion a carbonaceous additive in an amount equivalent to 0.1-1.0% by weight of elemental carbon after pyrolysis based on said silicon carbide, to form a second dispersion, c. pyrolyzing said second dispersion at a temperature which decomposes the carbonaceous additive to elemental carbon. d. shaping the resulting pyrolyzed dispersion into a green body substantially in the form of said desired pre-shaped sintered article and of dimensions larger than those of said desired sintered article by the amount of sintering shrinkage, and e. sintering the green body in an inert atmosphere chemically inert with respect to silicon carbide at atmospheric pressure or below atmospheric pressure at a temperature of about 1900°-2100° C until the ceramic article has a density of at least 85% of theoretical.
Claim 12
Independent Claim
179 words
A method of making a pre-shaped dense sintered silicon carbide ceramic article comprising the steps of: a. forming a substantially homogeneous first dispersion of a submicron powder of β-silicon carbide, a boron containing additive in an amount equivalent to about 0.3-3.0% by weight of boron based on said silicon carbide, b. incorporating in said first dispersion a carbonaceous additive in an amount equivalent to 0.1-1.0% by weight of elemental carbon after pyrolysis based on said silicon carbide, to form a second dispersion, c. pyrolyzing said second dispersion at a temperature which decomposes the carbonaceous additive to elemental carbon. d. shaping the resulting pyrolyzed dispersion into a green body substantially in the form of said desired pre-shaped sintered article and of dimensions larger than those of said desired sintered article by the amount of sintering shrinkage, and e. sintering the green body in an inert atmosphere chemically inert with respect to silicon carbide at atmospheric pressure or below atmospheric pressure at a temperature of about 1900°-2100° C until the ceramic article has a density of at least 85% of theoretical.
Claim 13
Dependent Claim
12 words
The method of claim 8 wherein said boron additive is elemental boron.
Claim 14
Dependent Claim
12 words
The method of claim 8 wherein said boron additive is boron carbide.
Claim 15
Dependent Claim
52 words
The method of claim 8 wherein said first dispersion is formed by the steps comprising forming a silica gel in a solution containing sugar and boric acid, dehydrating the gel to form a finely divided mixture and heating the mixture in an inert atmosphere to form a boron doped silicon carbide powder.
Claim 16
Dependent Claim
14 words
The method of claim 8 wherein said carbonaceous additive is a phenolformaldehyde condensate resin.
Claim 17
Dependent Claim
11 words
The method of claim 8 wherein said carbonaceous additive is polyphenylene.
Claim 18
Dependent Claim
11 words
The method of claim 8 wherein said carbonaceous additive is polymethylphenylene.
Claim 19
Dependent Claim
14 words
The method of claim 8 wherein said green body is formed by slip casting.
Claim 20
Dependent Claim
48 words
A pre-shaped sintered ceramic article consisting essentially of silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, the sintered ceramic article having a density of at least 85% of theoretical.
Claim 21
Dependent Claim
48 words
A pre-shaped sintered ceramic article consisting essentially of silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, the sintered ceramic article having a density of at least 85% of theoretical.
Claim 22
Dependent Claim
24 words
The pre-shaped sintered ceramic article according to claim 16 wherein said elemental carbon is present in an amount of 0.1 to 1.0% by weight.
Claim 23
Dependent Claim
54 words
A pre-shaped sintered ceramic article consisting essentially of β-silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, the sintered ceramic article having a density of at least 85% of theoretical and a fine grained uniform microstructure.
Claim 24
Dependent Claim
54 words
A pre-shaped sintered ceramic article consisting essentially of β-silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, the sintered ceramic article having a density of at least 85% of theoretical and a fine grained uniform microstructure.
Claim 25
Dependent Claim
22 words
The pre-shaped sintered ceramic article according to claim 18 wherein said elemental carbon is present in an amount of 0.1-1.0% by weight.
Claim 26
Dependent Claim
15 words
The pre-shaped sintered ceramic article of claim 18, wherein said article has a complex shape.
Claim 27
Dependent Claim
16 words
The pre-shaped sintered ceramic article of claim 18, wherein said article is a gas turbine blade.
Claim 28
Dependent Claim
59 words
A pre-shaped sintered silicon carbide ceramic article consisting essentially of β-silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, said ceramic article having a density of at least 95% of theoretical and a uniform grain size of less than 10 microns.
Claim 29
Dependent Claim
59 words
A pre-shaped sintered silicon carbide ceramic article consisting essentially of β-silicon carbide, about 0.3-3.0% by weight of boron based on said silicon carbide, and up to 1.0% by weight of elemental carbon based on said silicon carbide, said ceramic article having a density of at least 95% of theoretical and a uniform grain size of less than 10 microns.
Claim 30
Dependent Claim
22 words
The pre-shaped sintered ceramic article according to claim 22 wherein said elemental carbon is present in an amount of 0.1-1.0% by weight.
References Cited (Backward Citations)
US2636825A
Cited
US2637091A
Cited
US2908553A
Cited
US2916460A
Cited
US3079273A
Cited
US3065088A
Cited
US3175918A
Cited
US3459566A
Cited
US3765300A
Cited
US3649342A
Cited
US3808012A
Cited
US3852099A
Cited
US3853566A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1980-01-25 | 1980-07-26 | 1981-01-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1984-01-25 | 1984-07-26 | 1985-01-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1988-01-25 | 1988-07-26 | 1989-01-25 | $7700.00 | Window Closed / Lapsed |