US4354991A — Dense sintered silicon carbide ceramic

Claim 1

Independent Claim 88 words

A process for producing a dense sintered silicon carbide ceramic having high strength and a flexural strength of at least 25 kg/mm 2 at room temperature at 1400° C. which comprises: molding a mixture of an oxygen-containing aluminum compound which can be converted into aluminum oxide by heating in a non-oxidative atmosphere at a ratio of 0.5 to 35 wt.% as Al 2 O 3 with the remaining ceramic material substantially being silicon carbide; and pressureless sintering said mixture in a non-oxidative atmosphere at 1900° to 2300° C.

Claim 2

Dependent Claim 88 words

A process for producing a dense sintered silicon carbide ceramic having high strength and a flexural strength of at least 25 kg/mm 2 at room temperature at 1400° C. which comprises: molding a mixture of an oxygen-containing aluminum compound which can be converted into aluminum oxide by heating in a non-oxidative atmosphere at a ratio of 0.5 to 35 wt.% as Al 2 O 3 with the remaining ceramic material substantially being silicon carbide; and pressureless sintering said mixture in a non-oxidative atmosphere at 1900° to 2300° C.

Claim 3

Dependent Claim 27 words

The process according to claim 1 wherein said oxygen-containing aluminum compound is incorporated at a ratio of 2 to 20 wt.% as Al 2 O 3 .

Claim 4

Dependent Claim 16 words

The process according to claim 2 wherein aluminum oxide is used as said oxygen-containing aluminum compound.

Claim 5

Dependent Claim 83 words

The process according to claim 1 wherein a mixture of said oxygen-containing aluminum compound at a ratio of 6 to 35 wt.% and silicon carbide having a specific surface area of at least 10 m 2 /g and a purity of at least 95% at substantial residual portion is molded and treated by said pressureless sintering to obtain the product having a flexural strength of at least 35 kg/mm 2 at room temperature and 1400° C. and a density of at least 3.0.

Claim 6

Dependent Claim 83 words

The process according to claim 1 wherein a mixture of said aluminum oxide source at a ratio of 0.5 to 6 wt.% and silicon carbide having a specific surface area of at least 15 m 2 /g and a purity of at least 98% at substantial residual portion is molded and treated by said pressureless sintering to obtain the product having a flexural strength of at least 40 kg/mm 2 at room temperature and 1400° C. and a density of at least 3.0.

Claim 7

Dependent Claim 52 words

The process according to claim 1 wherein β-silicon carbide having a specific surface area of at least 10 m 2 /g and a purity of at least 98% is used to obtain a sintered silicon carbide having a flexural strength of at least 40 kg/mm 2 at room temperature and 1400° C.

Claim 8

Dependent Claim 27 words

The process according to claim 6 wherein said oxygen-containing aluminum compound is incorporated at a ratio of 2 to 20 wt.% as Al 2 O 3 .

Claim 9

Dependent Claim 97 words

A process for producing a sintered silicon carbide ceramic having high strength and a flexural strength of at least 25 kg/mm 2 at room temperature and 1400° C., which comprises: molding a mixture of an oxygen-containing aluminum compound which can be converted into aluminum oxide by heating in a non-oxidative atmosphere at a ratio of 0.5 to 35 wt.% as Al 2 O 3 with silicon carbide being the substantial remaining material of the ceramic mixture; and sintering said molded product at a temperature of 1900° to 2300° C. in a non-oxidative atmosphere containing an aluminum component.

Claim 10

Dependent Claim 97 words

A process for producing a sintered silicon carbide ceramic having high strength and a flexural strength of at least 25 kg/mm 2 at room temperature and 1400° C., which comprises: molding a mixture of an oxygen-containing aluminum compound which can be converted into aluminum oxide by heating in a non-oxidative atmosphere at a ratio of 0.5 to 35 wt.% as Al 2 O 3 with silicon carbide being the substantial remaining material of the ceramic mixture; and sintering said molded product at a temperature of 1900° to 2300° C. in a non-oxidative atmosphere containing an aluminum component.

Claim 11

Dependent Claim 41 words

The process according to claim 8 wherein said atmosphere around said silicon carbide molded product is formed by aluminum powder and/or aluminum compound powder or a molded product of said powder or a sintered product obtained by sintering said molded product.

Claim 12

Dependent Claim 34 words

The process according to claim 9 wherein said aluminum compound powder is one or more of alumina, aluminum nitride, aluminum carbide, aluminum silicon carbide (Al 4 SiC 4 ), aluminum boride and aluminum phosphide.

Claim 13

Dependent Claim 39 words

The process according to claim 9 wherein said aluminum powder and/or aluminum compound powder or a molded product of said powder or a sintered product obtained by sintering said molded product contains 2 to 40 wt.% of aluminum component.

Claim 14

Dependent Claim 22 words

The process according to claim 8 wherein said oxygen-containing aluminum compound at least a portion of alumina (Al 2 O 3 ).

Claim 15

Dependent Claim 16 words

The process according to claim 8 wherein said atmosphere comprises aluminum, silicon and/or carbon as components.

Claim 16

Dependent Claim 13 words

The process according to claim 8 wherein said atmosphere comprises an inert gas.

Claim 17

Dependent Claim 103 words

A process for producing a sintered silicon carbide having high strength and a flexural strength of at least 25 kg/mm 2 at room temperature and 1400° C., which comprises: molding a mixture of an oxygen-containing aluminum compound which can be converted into aluminum oxide by heating in a nonoxidative atmosphere at a ratio of 0.5 to 35 wt.% as Al 2 O 3 in silicon carbide having a specific surface area of at least 10 m 2 /g and a purity of at least 95%; and pressureless sintering said molded product in an atmosphere comprising an aluminum component at 1900° to 2300° C.

Claim 18

Dependent Claim 103 words

A process for producing a sintered silicon carbide having high strength and a flexural strength of at least 25 kg/mm 2 at room temperature and 1400° C., which comprises: molding a mixture of an oxygen-containing aluminum compound which can be converted into aluminum oxide by heating in a nonoxidative atmosphere at a ratio of 0.5 to 35 wt.% as Al 2 O 3 in silicon carbide having a specific surface area of at least 10 m 2 /g and a purity of at least 95%; and pressureless sintering said molded product in an atmosphere comprising an aluminum component at 1900° to 2300° C.

Claim 19

Dependent Claim 58 words

The process according to claim 15 wherein a mixture of an oxygen-containing aluminum compound at a ratio of 2 to 20 wt.% as Al 2 O 3 and silicon carbide at the residual portion is sintered to obtain a sintered product having a flexural strength of at least 35 kg/mm 2 at a room temperature and 1400° C.

Claim 20

Dependent Claim 16 words

The process according to claim 16 wherein aluminum oxide is used as said oxygen-containing aluminum compound.

Claim 21

Dependent Claim 15 words

The process according to claim 15 wherein β-silicon carbide is used as said silicon carbide.

Claim 22

Dependent Claim 39 words

The process according to claim 15 wherein said atmosphere comprising an aluminum component is formed by aluminum powder and/or an aluminum compound or a molded product of said powder or a sintered product obtained by sintering said molded product.

Claim 23

Dependent Claim 39 words

The process according to claim 1, wherein said mixture of an oxygen-containing aluminum compound and silicon carbide is such that a material is formed having a micro structure characterized by an intertwined fine prismatic or plate-like silicon carbide component.

Claim 24

Dependent Claim 21 words

The process according to claim 1, wherein said silicon carbide has a surface area of at least 5 m 2 /g.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1985-10-18	1986-04-19	1986-10-19	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1989-10-18	1990-04-19	1990-10-19	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	1993-10-18	1994-04-19	1994-10-19	$7700.00	Window Closed / Lapsed

Dense sintered silicon carbide ceramic

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