US4962069A — Highly densified bodies from preceramic polysilaz…

Claim 1

Independent Claim 166 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 comprising silicon carbide powder, a metal-containing sintering aid, and a preceramic polysilazane, 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.4 weight percent based on the total weight of the silicon carbide powder and the char derived from the preceramic polysilazane 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 2000° C. to obtain a sintered body of silicon carbide with a density greater than 2.4 g/cm 3 .

Claim 2

Independent Claim 166 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 comprising silicon carbide powder, a metal-containing sintering aid, and a preceramic polysilazane, 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.4 weight percent based on the total weight of the silicon carbide powder and the char derived from the preceramic polysilazane 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 2000° C. to obtain a sintered body of silicon carbide with a density greater than 2.4 g/cm 3 .

Claim 3

Dependent Claim 120 words

A method as described in claim 1 wherein the free carbon value of the preceramic polysilazane is determined, prior to forming a handleable green body, by heating a known amount of the preceramic polysilazane under an inert atmosphere to an elevated temperature for a time sufficient to convert the preceramic polysilazane into a stable silicon carbide ceramic char material, determining the ceramic char yield and the silicon and carbon content of the stable silicon carbide ceramic char material, and then calculating the amount of free carbon in the stable silicon carbide ceramic char material per part of the preceramic polysilazane 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.8 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.8 weight percent and wherein the sintered body of silicon carbide has a density greater than 2.7 g/cm 3 .

Claim 6

Dependent Claim 25 words

A method as described in claim 3 wherein the intimate mixture also contains a polysilazane curing agent in an effective amount to cure the polysilazane.

Claim 7

Dependent Claim 25 words

A method as described in claim 4 wherein the intimate mixture also contains a polysilazane curing agent in an effective amount to cure the polysilazane.

Claim 8

Dependent Claim 55 words

A method as described in claim 3 wherein the preceramic polysilazane contains [R 2 SiNH] and [RSi(NU) 1 .5 ] 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 the sintering is carried out without pressure.

Claim 9

Dependent Claim 55 words

A method as described in claim 5 wherein the preceramic polysilazane contains [R 2 SiNH] and [RSi(NH) 1 .5 ] 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 the sintering is carried out without pressure.

Claim 10

Dependent Claim 15 words

A method as described in claim 3 wherein the preceramic polysilazane is a silacyclobutasilazane polymer.

Claim 11

Dependent Claim 15 words

A method as described in claim 4 wherein the preceramic polysilazane is a silacyclobutasilazane polymer.

Claim 12

Dependent Claim 32 words

A method as described in claim 7 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 0.8 and 3.0 weight percent.

Claim 13

Dependent Claim 32 words

A method as described in claim 9 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 0.8 and 3.0 weight percent.

Claim 14

Dependent Claim 32 words

A method as described in claim 11 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 1.5 and 2.5 weight percent.

Claim 15

Dependent Claim 32 words

A method as described in claim 11 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 1.5 and 2.5 weight percent.

Claim 16

Dependent Claim 17 words

A method as described in claim 13 wherein the metal-containing sintering aid is boron or boron carbide.

Claim 17

Dependent Claim 17 words

A method as described in claim 14 wherein the metal-containing sintering aid is boron or boron carbide.

Claim 18

Dependent Claim 39 words

A method as described in claim 15 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 19

Dependent Claim 39 words

A method as described in claim 16 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 20

Dependent Claim 19 words

A method as described in claim 6 wherein the handleable green body is cured prior to the sintering step.

Claim 21

Dependent Claim 19 words

A method as described in claim 10 wherein the handleable green body is cured prior to the sintering step.

Claim 22

Independent Claim 115 words

A method of forming a handleable green body, which method comprises (a) preparing an intimate mixture comprising silicon carbide powder, a metal-containing sintering aid, and a preceramic polysilazane, 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.4 weight percent based on the total weight of the silicon carbide powder and the char derived from the preceramic polysilazane; and (b) forming the intimate mixture into the desired shape under pressure at a temperature less than about 500° C.

Claim 23

Independent Claim 115 words

A method of forming a handleable green body, which method comprises (a) preparing an intimate mixture comprising silicon carbide powder, a metal-containing sintering aid, and a preceramic polysilazane, 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.4 weight percent based on the total weight of the silicon carbide powder and the char derived from the preceramic polysilazane; and (b) forming the intimate mixture into the desired shape under pressure at a temperature less than about 500° C.

Claim 24

Dependent Claim 119 words

A method as described in claim 21 wherein the free carbon value of the preceramic polysilazane is determined, prior to preparing the intimate mixture, by heating a known amount of the preceramic polysilazane under an inert atmosphere to an elevated temperature for a time sufficient to convert the preceramic polysilazane into a stable silicon carbide ceramic char material, determining the ceramic char yield and the silicon and carbon content of the stable silicon carbide ceramic char material, and then calculating the amount of free carbon in the stable silicon carbide ceramic char material per part of the preceramic polysilazane 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 51 words

A method as described in claim 21 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.8 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 26

Dependent Claim 31 words

A method as described in claim 22 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.8 weight percent.

Claim 27

Dependent Claim 25 words

A method as described in claim 23 wherein the intimate mixture also contains a polysilazane curing agent in an effective amount to cure the polysilazane.

Claim 28

Dependent Claim 25 words

A method as described in claim 24 wherein the intimate mixture also contains a polysilazane curing agent in an effective amount to cure the polysilazane.

Claim 29

Dependent Claim 46 words

A method as described in claim 23 wherein the preceramic polysilazane contains [R 2 SiNH] and [RSi(NH) 1 .5 ] 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 46 words

A method as described in claim 25 wherein the preceramic polysilazane contains [R 2 SiNH] and [RSi(NH) 1 .5 ] 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 31

Dependent Claim 15 words

A method as described in claim 23 wherein the preceramic polysilazane is a silacyclobutasilazane polymer.

Claim 32

Dependent Claim 15 words

A method as described in claim 24 wherein the preceramic polysilazane is a silacyclobutasilazane polymer.

Claim 33

Dependent Claim 32 words

A method as described in claim 25 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 1.5 and 2.5 weight percent.

Claim 34

Dependent Claim 32 words

A method as described in claim 27 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 1.5 and 2.5 weight percent.

Claim 35

Dependent Claim 17 words

A method as described in claim 31 wherein the metal-containing sintering aid is boron or boron carbide.

Claim 36

Dependent Claim 17 words

A method as described in claim 32 wherein the metal-containing sintering aid is boron or boron carbide.

Claim 37

Dependent Claim 14 words

A method as described in claim 26 wherein the handleable green body is cured.

Claim 38

Dependent Claim 14 words

A method as described in claim 30 wherein the handleable green body is cured.

Claim 39

Dependent Claim 82 words

A uniform mixture comprising silicon carbide powder, a metal-containing sintering aid, and a preceramic polysilazane, 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.4 weight percent based on the total weight of the silicon carbide powder and the char derived from the preceramic polysilazane.

Claim 40

Dependent Claim 82 words

A uniform mixture comprising silicon carbide powder, a metal-containing sintering aid, and a preceramic polysilazane, 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 polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.4 weight percent based on the total weight of the silicon carbide powder and the char derived from the preceramic polysilazane.

Claim 41

Dependent Claim 52 words

A uniform mixture as described in claim 37 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is greater than 0.8 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 42

Dependent Claim 23 words

A uniform mixture as described in claim 38 which also contains a polysilazane curing agent in an effective amount to cure the polysilazane.

Claim 43

Dependent Claim 47 words

A uniform mixture as described in claim 38 wherein the preceramic polysilazane contains [R 2 SiNH] and [RSi(NH) 1 .5 ] 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 47 words

A uniform mixture as described in claim 39 wherein the preceramic polysilazane contains [R 2 SiNH] and [RSi(NH) 1 .5 ] 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 45

Dependent Claim 16 words

A uniform mixture as described in claim 38 wherein the preceramic polysilazane is a silacyclobutasilazane polymer.

Claim 46

Dependent Claim 16 words

A uniform mixture as described in claim 39 wherein the preceramic polysilazane is a silacyclobutasilazane polymer.

Claim 47

Dependent Claim 33 words

A uniform mixture as described in claim 38 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 1.5 and 2.5 weight percent.

Claim 48

Dependent Claim 33 words

A uniform mixture as described in claim 41 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 1.5 and 2.5 weight percent.

Claim 49

Dependent Claim 33 words

A uniform mixture as described in claim 43 wherein the preceramic polysilazane is present at such a level that the free carbon value of the mixture is between 1.5 and 2.5 weight percent.

Claim 50

Dependent Claim 18 words

A uniform mixture as described in claim 45 wherein the metal-containing sintering aid is boron or boron carbide.

Claim 51

Dependent Claim 18 words

A uniform mixture as described in claim 46 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)	1993-10-08	1994-04-09	1994-10-09	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-10-08	1998-04-09	1998-10-09	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-10-08	2002-04-09	2002-10-09	$7700.00	Window Closed / Lapsed

Highly densified bodies from preceramic polysilazanes filled with silicon carbide powders

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