Patent US4929573A successfully refreshed from Google Patents.
US4929573A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Highly densified bodies from organopolysiloxanes filled with silicon carbide powders
Assignee: Dow Silicones Corp
•
Filing: 1988-09-26
•
Granted: 1990-05-29
•
Expires: 2008-09-26
Abstract
Abstract The preparation of highly densified ceramic bodies by the sintering of certain organopolysiloxanes filled with silicon carbide powders, and metal-containing sintering aids is described. Such highly densified ceramic bodies can be prepared by either a pressureless sintering process 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 handles and, if desired, machined before sintered. The 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 08:31
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/515; C04B35/56; C04B35/565; C04B35/575; C04B35/571
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
168 words
A method of preparing a sintered body of silicon carbide, said method comprising (a) forming a handleable green body by (i) preparing an intimate mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, and a preceramic organopolysiloxane, 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 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 char derived from the preceramic organopolysiloxane and (ii) then forming the intimate 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
168 words
A method of preparing a sintered body of silicon carbide, said method comprising (a) forming a handleable green body by (i) preparing an intimate mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, and a preceramic organopolysiloxane, 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 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 char derived from the preceramic organopolysiloxane and (ii) then forming the intimate 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
114 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 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 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
68 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 and 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
52 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
48 words
A method as described in claim 5 wherein the preceramic organopolysiloxane is described by the unit formula [PhSiO.sub.1.5 ]MeSiO.sub.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
61 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 and 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 11
Dependent Claim
17 words
A method as described in claim 8 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
21 words
A method as described in claim 12 wherein the handleable green body is sintered at a temperature of about 2150° C.
Claim 15
Independent Claim
117 words
A method of forming a handleable green body, which method comprises (a) preparing an intimate mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, and a preceramic organopolysiloxane, 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 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 char derived from the preceramic organopolysiloxane: and (b) forming the intimate mixture into the desired shape under pressure at a temperature less than about 500° C.
Claim 16
Independent Claim
117 words
A method of forming a handleable green body, which method comprises (a) preparing an intimate mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, and a preceramic organopolysiloxane, 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 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 char derived from the preceramic organopolysiloxane: and (b) forming the intimate mixture into the desired shape under pressure at a temperature less than about 500° C.
Claim 17
Dependent Claim
113 words
A method as described in claim 14 wherein the free carbon value of the preceramic organopolysiloxane is determined, prior to preparing the intimate 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 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 18
Dependent Claim
51 words
A method as described in claim 14 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 19
Dependent Claim
31 words
A method as described in claim 15 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 20
Dependent Claim
44 words
A method as described in claim 17 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 21
Dependent Claim
32 words
A method as described in claim 18 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 22
Dependent Claim
32 words
A method as described in claim 19 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 23
Dependent Claim
51 words
A method as described in claim 19 wherein the preceramic organopolysiloxane is described by the unit formula [PhSiO.sub.1.5 ][MeSiO.sub.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 24
Dependent Claim
38 words
A method as described in claim 21 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 25
Dependent Claim
17 words
A method as described in claim 21 wherein the metal-containing sintering aid is boron or boron carbide.
Claim 26
Dependent Claim
84 words
A uniform mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, and a preceramic organopolysiloxane, 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 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 char derived from the preceramic organopolysiloxane.
Claim 27
Dependent Claim
84 words
A uniform mixture consisting essentially of silicon carbide powder, a metal-containing sintering aid, and a preceramic organopolysiloxane, 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 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 char derived from the preceramic organopolysiloxane.
Claim 28
Dependent Claim
52 words
A uniform mixture as described in claim 24 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 29
Dependent Claim
47 words
A uniform mixture as described in claim 25 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 30
Dependent Claim
33 words
A uniform mixture as described in claim 26 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 31
Dependent Claim
33 words
A uniform mixture as described in claim 27 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 32
Dependent Claim
52 words
A uniform mixture as described in claim 27 wherein the preceramic organopolysiloxane is described by the unit formula [PhSiO.sub.1.5 ][MeSiOi.sub.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 33
Dependent Claim
39 words
A uniform mixture as described in claim 29 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 34
Dependent Claim
18 words
A uniform mixture as described in claim 29 wherein the metal-containing sintering aid is boron or boron carbide.
References Cited (Backward Citations)
US3108985A
Cited
US3090691A
Cited
US3485904A
Cited
US4004934A
Cited
US4041117A
Cited
US4122139A
Cited
US4081284A
Cited
US4289720A
Cited
US4269753A
Cited
US4269757A
Cited
US4255316A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-05-28 | 1993-11-27 | 1994-05-29 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-05-28 | 1997-11-27 | 1998-05-29 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-05-28 | 2001-11-27 | 2002-05-29 | $7700.00 | Window Closed / Lapsed |