US4888376A
Expired / Lapsed
US
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Curable organopolysiloxanes filled with silicon carbide powders and highly densified sintered bodies therefrom
Assignee: Dow Silicones Corp
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Filing: 1988-09-26
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Granted: 1989-12-19
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Expires: 2008-09-26
Abstract
Abstract The preparation of highly densified ceramic bodies by sintering certain curable organopolysiloxanes filled with silicon carbide powders, metal-containing sintering aids, and organopolysiloxane curing agents described. Such highly densified ceramic bodies can be prepared by either a pressure-less or a hot press sintering process. The compositions of this invention can be formed into desired shapes and then sintered to form ceramic, shaped bodies with high densities. One advantage of the present invention is that the green bodies have relative high strengths and thus can be easily handled and, if desired, machined before sintering. The curable organopolysiloxanes useful in this invention must yield a ceramic char which contains free or excess carbon in addition to carbon in the form of silicon carbide upon pyrolysis to elevated temperatures.
Inventors
- 👤 William H. Atwell
- 👤 Gary T. Burns
- 👤 Chandan K. Saha
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-04 00:19
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565; C04B35/575; C04B35/571
Claims Analysis
Total Claims: 53
Claim 1
Independent Claim
190 words
A method of preparing a sintered body of silicon carbide, said method comprising (a) forming a handleable green body by (i) blending components consisting essentially of silicon carbide powder, a metal-containing sintering aid, an organopolysiloxane curing agent, and a preceramic organopolysiloxane to a uniform mixture, where the metal containing sintering aid is present at 0.1 to 3.0 weight percent of the metal based on the weight of silicon carbide powder, where the organopolysiloxane curing agent is present in an effective amount to cure, and where the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.2 weight percent based on the total weight of the silicon carbide powder and the stable ceramic char derived from the preceramic organopolysiloxane, and (ii) then forming the uniform mixture into the desired shape under pressure at a temperature less than about 500° C. to obtain a handleable green body; and (b) sintering the handleable green body in an inert atmosphere at a temperature greater than 1900° C. to obtain a sintered body of silicon carbide with a density greater than 2.4 g/cm 3 .
Claim 2
Independent Claim
190 words
A method of preparing a sintered body of silicon carbide, said method comprising (a) forming a handleable green body by (i) blending components consisting essentially of silicon carbide powder, a metal-containing sintering aid, an organopolysiloxane curing agent, and a preceramic organopolysiloxane to a uniform mixture, where the metal containing sintering aid is present at 0.1 to 3.0 weight percent of the metal based on the weight of silicon carbide powder, where the organopolysiloxane curing agent is present in an effective amount to cure, and where the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.2 weight percent based on the total weight of the silicon carbide powder and the stable ceramic char derived from the preceramic organopolysiloxane, and (ii) then forming the uniform mixture into the desired shape under pressure at a temperature less than about 500° C. to obtain a handleable green body; and (b) sintering the handleable green body in an inert atmosphere at a temperature greater than 1900° C. to obtain a sintered body of silicon carbide with a density greater than 2.4 g/cm 3 .
Claim 3
Dependent Claim
125 words
A method as described in claim 1 wherein the free carbon value of the preceramic organopolysiloxane is determined, prior to forming a handleable green body, by heating a known amount of the preceramic organopolysiloxane containing an effective amount of an organopolysiloxane curing agent under an inert atmosphere to an elevated temperature for a time sufficient to convert the preceramic organopolysiloxane into a stable ceramic char material, determining the stable ceramic char yield and the silicon and carbon content of the stable ceramic char material, and then calculating the amount of free carbon in the stable ceramic char material per part of the preceramic organopolysiloxane and wherein the metal-containing sintering aid is selected from the group consisting of boron, boron containing compounds, aluminum, and aluminum-containing compounds.
Claim 4
Dependent Claim
67 words
A method as described in claim 1 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.5 weight percent, wherein the sintered body of silicon carbide has a density greater than 2.7 g/cm 3 , and wherein the metal-containing sintering aid is selected from the group consisting of boron, boron-containing compounds, aluminum, and aluminum-containing compounds.
Claim 5
Dependent Claim
48 words
A method as described in claim 2 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.5 weight percent and wherein the sintered body of silicon carbide has a density greater than 2.7 g/cm 3 .
Claim 6
Dependent Claim
54 words
A method as described in claim 4 wherein the preceramic organopolysiloxane contains [RSiO 1 .5 ] and [R 2 SiO] units where each R is independently selected from the group consisting of hydrogen, alkyl radicals containing 1 to 20 carbon atoms, phenyl radicals, and vinyl radicals and wherein sintering is carried out without pressure.
Claim 7
Dependent Claim
32 words
A method as described in claim 5 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is between 0.5 and 3.0 weight percent.
Claim 8
Dependent Claim
32 words
A method as described in claim 6 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is between 1.0 and 2.0 weight percent.
Claim 9
Dependent Claim
55 words
A method as described in claim 5 wherein the preceramic organopolysiloxane is described by the unit formula [PhSiO 1 .5 ][MeSiO 1 .5 ][PhViSiO] where there are 10 to 90 mole percent [PhSiO 1 .5 ] units, 0 to 50 mole percent [MeSiO 1 .5 ] units, and 10 to 90 mole percent [PhViSiO] units.
Claim 10
Dependent Claim
38 words
A method as described in claim 8 wherein there are 20 to 30 mole percent [PhSiO 1 .5 ] units, 30 to 50 mole percent [MeSiO 1 .5 ] units, and 30 to 50 mole percent [PhViSiO] units.
Claim 11
Dependent Claim
17 words
A method as described in claim 9 wherein the metal-containing sintering aid is boron or boron carbide.
Claim 12
Dependent Claim
39 words
A method as described in claim 4 wherein the handleable green body is sintered at a temperature of 2000° to 2200° C. to obtain a sintered body of silicon carbide with a density greater than 2.9 g/cm 3 .
Claim 13
Dependent Claim
39 words
A method as described in claim 9 wherein the handleable green body is sintered at a temperature of 2000° to 2200° C. to obtain a sintered body of silicon carbide with a density greater than 2.9 g/cm 3 .
Claim 14
Dependent Claim
19 words
A method as described in claim 3 wherein the handleable green body is cured prior to the sintering step.
Claim 15
Dependent Claim
19 words
A method as described in claim 4 wherein the handleable green body is cured prior to the sintering step.
Claim 16
Dependent Claim
19 words
A method as described in claim 9 wherein the handleable green body is cured prior to the sintering step.
Claim 17
Dependent Claim
32 words
A method as described in claim 14 wherein the organopolysiloxane curing agent is an organic peroxide which is present at 0.1 to 5.0 weight percent based on the weight of the organopolysiloxane.
Claim 18
Dependent Claim
32 words
A method as described in claim 15 wherein the organopolysiloxane curing agent is an organic peroxide which is present at 0.1 to 5.0 weight percent based on the weight of the organopolysiloxane.
Claim 19
Dependent Claim
45 words
A method as described in claim 14 wherein the organopolysiloxane contains both vinyl radicals and hydrogen atoms attached to silicon and wherein the organopolysiloxane curing agent is a platinum-containing catalyst which is present at 1.0 to 1000 ppm based on the weight of the organopolysiloxane.
Claim 20
Dependent Claim
45 words
A method as described in claim 15 wherein the organopolysiloxane contains both vinyl radicals and hydrogen atoms attached to silicon and wherein the organopolysiloxane curing agent is a platinum-containing catalyst which is present at 1.0 to 1000 ppm based on the weight of the organopolysiloxane.
Claim 21
Independent Claim
139 words
A method of forming a handleable green body, which method comprises (a) blending components consisting essentially of silicon carbide powder, a metal-containing sintering aid, an organopolysiloxane curing agent, and a preceramic organopolysiloxane to a uniform mixture, where the metal containing sintering aid is present at 0.1 to 3.0 weight percent of the metal based on the weight of silicon carbide powder, where the organopolysiloxane curing agent is present in an effective amount to cure, and where the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.2 weight percent based on the total weight of the silicon carbide powder and the stable ceramic char derived from the preceramic organopolysiloxane; and (b) forming the uniform mixture into the desired shape under pressure at a temperature less than about 500° C.
Claim 22
Independent Claim
139 words
A method of forming a handleable green body, which method comprises (a) blending components consisting essentially of silicon carbide powder, a metal-containing sintering aid, an organopolysiloxane curing agent, and a preceramic organopolysiloxane to a uniform mixture, where the metal containing sintering aid is present at 0.1 to 3.0 weight percent of the metal based on the weight of silicon carbide powder, where the organopolysiloxane curing agent is present in an effective amount to cure, and where the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.2 weight percent based on the total weight of the silicon carbide powder and the stable ceramic char derived from the preceramic organopolysiloxane; and (b) forming the uniform mixture into the desired shape under pressure at a temperature less than about 500° C.
Claim 23
Dependent Claim
115 words
A method as described in claim 20 wherein the free carbon value of the preceramic organopolysiloxane is determined, prior to preparing the uniform mixture, by heating a known amount of the preceramic organopolysiloxane under an inert atmosphere to an elevated temperature for a time sufficient to convert the preceramic organopolysiloxane into a stable ceramic char material, determining the stable ceramic char yield and the silicon and carbon content of the stable ceramic char material, and then calculating the amount of free carbon in the stable ceramic char material per part of the preceramic organopolysiloxane and wherein the metal-containing sintering aid is selected from the group consisting of boron, boron containing compounds, aluminum, and aluminum-containing compounds.
Claim 24
Dependent Claim
51 words
A method as described in claim 20 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.5 weight percent and wherein the metal-containing sintering aid is selected from the group consisting of boron, boron-containing compounds, aluminum, and aluminum-containing compounds.
Claim 25
Dependent Claim
31 words
A method as described in claim 21 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.5 weight percent.
Claim 26
Dependent Claim
46 words
A method as described in claim 23 wherein the preceramic organopolysiloxane contains [RSiO 1 .5 ] and [R 2 SiO] units where each R is independently selected from the group consisting of hydrogen, alkyl radicals containing 1 to 20 carbon atoms, phenyl radicals, and vinyl radicals.
Claim 27
Dependent Claim
32 words
A method as described in claim 24 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is between 0.5 and 3.0 weight percent.
Claim 28
Dependent Claim
32 words
A method as described in claim 25 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is between 1.0 and 2.0 weight percent.
Claim 29
Dependent Claim
30 words
A method as described in claim 26 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is about 1.5 weight percent.
Claim 30
Dependent Claim
55 words
A method as described in claim 24 wherein the preceramic organopolysiloxane is described by the unit formula [PhSiO 1 .5 ][MeSiO 1 .5 ][PhViSiO] where there are 10 to 90 mole percent [PhSiO 1 .5 ] units, 0 to 50 mole percent [MeSiO 1 .5 ] units, and 10 to 90 mole percent [PhViSiO] units.
Claim 31
Dependent Claim
38 words
A method as described in claim 28 wherein there are 20 to 30 mole percent [PhSiO 1 .5 ] units, 30 to 50 mole percent [MeSiO 1 .5 ] units, and 30 to 50 mole percent [PhViSiO] units.
Claim 32
Dependent Claim
17 words
A method as described in claim 28 wherein the metal-containing sintering aid is boron or boron carbide.
Claim 33
Dependent Claim
20 words
A method as described in claim 20 wherein the handleable green body formed thereby is subsequently cured prior to sintering.
Claim 34
Dependent Claim
20 words
A method as described in claim 21 wherein the handleable green body formed thereby is subsequently cured prior to sintering.
Claim 35
Dependent Claim
20 words
A method as described in claim 29 wherein the handleable green body formed thereby is subsequently cured prior to sintering.
Claim 36
Dependent Claim
32 words
A method as described in claim 32 wherein the organopolysiloxane curing agent is an organic peroxide which is present at 0.1 to 5.0 weight percent based on the weight of the organopolysiloxane.
Claim 37
Dependent Claim
32 words
A method as described in claim 33 wherein the organopolysiloxane curing agent is an organic peroxide which is present at 0.1 to 5.0 weight percent based on the weight of the organopolysiloxane.
Claim 38
Dependent Claim
45 words
A method as described in claim 32 wherein the organopolysiloxane contains both vinyl radicals and hydrogen atoms attached to silicon and wherein the organopolysiloxane curing agent is a platinum-containing catalyst which is present at 1.0 to 1000 ppm based on the weight of the organopolysiloxane.
Claim 39
Dependent Claim
45 words
A method as described in claim 33 wherein the organopolysiloxane contains both vinyl radicals and hydrogen atoms attached to silicon and wherein the organopolysiloxane curing agent is a platinum-containing catalyst which is present at 1.0 to 1000 ppm based on the weight of the organopolysiloxane.
Claim 40
Dependent Claim
103 words
A uniform mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, a preceramic organopolysiloxane, and an organopolysiloxane curing agent, where the metal-containing sintering aid is present at 0.1 to 3.0 weight percent of the metal based on the weight of silicon carbide powder, where the organopolysiloxane curing agent is present in an effective amount to cure, and where the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.2 weight percent based on the total weight of the silicon carbide powder and the stable ceramic char derived from the preceramic organopolysiloxane.
Claim 41
Dependent Claim
103 words
A uniform mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, a preceramic organopolysiloxane, and an organopolysiloxane curing agent, where the metal-containing sintering aid is present at 0.1 to 3.0 weight percent of the metal based on the weight of silicon carbide powder, where the organopolysiloxane curing agent is present in an effective amount to cure, and where the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.2 weight percent based on the total weight of the silicon carbide powder and the stable ceramic char derived from the preceramic organopolysiloxane.
Claim 42
Dependent Claim
52 words
A uniform mixture as described in claim 38 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is greater than 0.5 weight percent and wherein the metal-containing sintering aid is selected from the group consisting of boron, boron-containing compounds, aluminum, and aluminum-containing compounds.
Claim 43
Dependent Claim
47 words
A uniform mixture as described in claim 39 wherein the preceramic organopolysiloxane contains [RSiO 1 .5 ] and [R 2 SiO] units where each R is independently selected from the group consisting of hydrogen, alkyl radicals containing 1 to 20 carbon atoms, phenyl radicals, and vinyl radicals.
Claim 44
Dependent Claim
33 words
A uniform mixture as described in claim 40 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is between 0.5 and 3.0 weight percent.
Claim 45
Dependent Claim
33 words
A uniform mixture as described in claim 41 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is between 1.0 and 2.0 weight percent.
Claim 46
Dependent Claim
31 words
A uniform mixture as described in claim 42 wherein the preceramic organopolysiloxane is present at such a level that the free carbon value of the mixture is about 1.5 weight percent.
Claim 47
Dependent Claim
56 words
A uniform mixture as described in claim 41 wherein the preceramic organopolysiloxane is described by the unit formula [PhSiO 1 .5 ][MeSiO 1 .5 ][PhViSiO] where there are 10 to 90 mole percent [PhSiO 1 .5 ] units, 0 to 50 mole percent [MeSiO 1 .5 ] units, and 10 to 90 mole percent [PhViSiO] units.
Claim 48
Dependent Claim
39 words
A uniform mixture as described in claim 44 wherein there are 20 to 30 mole percent [PhSiO 1 .5 ] units, 30 to 50 mole percent [MeSiO 1 .5 ] units, and 30 to 50 mole percent [PhViSiO] units.
Claim 49
Dependent Claim
18 words
A uniform mixture as described in claim 41 wherein the metal-containing sintering aid is boron or boron carbide.
Claim 50
Dependent Claim
33 words
A uniform mixture as described in claim 39 wherein the organopolysiloxane curing agent is an organic peroxide which is present at 0.1 to 5.0 weight percent based on the weight of the organopolysiloxane.
Claim 51
Dependent Claim
33 words
A uniform mixture as described in claim 45 wherein the organopolysiloxane curing agent is an organic peroxide which is present at 0.1 to 5.0 weight percent based on the weight of the organopolysiloxane.
Claim 52
Dependent Claim
46 words
A uniform mixture as described in claim 39 wherein the organopolysiloxane contains both vinyl radicals and hydrogen atoms attached to silicon and wherein the organopolysiloxane curing agent is a platinum-containing catalyst which is present at 1.0 to 1000 ppm based on the weight of the organopolysiloxane.
Claim 53
Dependent Claim
46 words
A uniform mixture as described in claim 45 wherein the organopolysiloxane contains both vinyl radicals and hydrogen atoms attached to silicon and wherein the organopolysiloxane curing agent is a platinum-containing catalyst which is present at 1.0 to 1000 ppm based on the weight of the organopolysiloxane.
References Cited (Backward Citations)
US3108985A
Cited
US3090691A
Cited
US3485904A
Cited
US4004934A
Cited
US4041117A
Cited
US4122139A
Cited
US4081284A
Cited
US4289720A
Cited
JPS54134744A
Cited
US4269753A
Cited
US4269757A
Cited
US4255316A
Cited
CA1180189A
Cited
DE3500962A1
Cited
JPH0616869A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1992-12-18 | 1993-06-19 | 1993-12-19 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-12-18 | 1997-06-19 | 1997-12-19 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-12-18 | 2001-06-19 | 2001-12-19 | $7700.00 | Window Closed / Lapsed |