US4929573A — Highly densified bodies from organopolysiloxanes …

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.

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

Highly densified bodies from organopolysiloxanes filled with silicon carbide powders

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