Silicon carbide sintered body and process for production thereof

Claim 2

A process for producing a silicon carbide sintered body, which comprises the steps of: (a) mixing a starting material in powder form composed of 3.5 to 10% by weight, calculated as elemental aluminum, of aluminum nitride, 0.2 to 5% by weight, calculated as elemental chromium, of chromium carbide, and the balance being silicon carbide; and (b) sintering the mixed powder into an integrated molded article.

Claim 3

The process of claim 1 wherein the sintering is carried out at a temperature of 1850° to 2050° C.

Claim 4

The process of claim 1, wherein the mixed powder is molded under pressure before sintering.

Claim 5

The process of claim 1 wherein the mixed powder is sintered under pressure.

Claim 6

A process for producing a silicon carbide sintered body, which comprises the steps of: (a) mixing a starting material in powder form composed of 0.2 to 5% by weight, calculated as elemental aluminum, of aluminum nitride, 0.2 to 5% by weight, calculated as elemental rare earth, of at least one rare earth compound, and 0.2 to 10% by weight, calculated as elemental chromium, of chromium carbide, and the balance of silicon carbide; and (b) sintering the mixed powder into an integrated molded article.

Claim 7

A process for producing a silicon carbide sintered body, which comprises the steps of: (a) mixing a starting material in powder form composed of 0.2 to 5% by weight, calculated as elemental aluminum, of aluminum nitride, 0.2 to 5% by weight, calculated as elemental rare earth, of at least one rare earth compound, and 0.2 to 10% by weight, calculated as elemental chromium, of chromium carbide, and the balance of silicon carbide; and (b) sintering the mixed powder into an integrated molded article.

Claim 8

The process of claim 5, wherein the starting powder contains 0.2 to 3% by weight, calculated as elemental aluminum, of the aluminum nitride, 0.2 to 2% by weight, calculated as elemental rare earth, of the rare earth compound, and 0.4 to 5% by weight, calculated as elemental chromium, of the chromium carbide.

Claim 9

The process of claim 5 wherein the sintering is carried out at a temperature of 1850° to 2050° C.

Claim 10

The process of claim 5, wherein the mixed powder is molded under pressure before sintering.

Claim 11

The process of claim 5 wherein the mixed powder is sintered under pressure.

Claim 12

A silicon carbide sintered body composed of 3.5 to 10% by weight, calculated as elemental aluminum, of aluminum nitride, 0.2 to 5% by weight, calculated as elemental chromium, of chromium carbide, and the balance being silicon carbide, wherein said silicon carbide is present in the sintered body as particles of the alpha-type crystal structure which are substantially spherical and have an average particle diameter of 0.5 to 2 micrometers, and particles which contain chromium as a main component and aluminum and silicon when analyzed by an x-ray microanalyzer and show a high luminance under a metallurgical microscope are present in the cystal grain boundary containing the aluminum and chromium components.

Claim 13

A silicon carbide sintered body composed of 3.5 to 10% by weight, calculated as elemental aluminum, of aluminum nitride, 0.2 to 5% by weight, calculated as elemental chromium, of chromium carbide, and the balance being silicon carbide, wherein said silicon carbide is present in the sintered body as particles of the alpha-type crystal structure which are substantially spherical and have an average particle diameter of 0.5 to 2 micrometers, and particles which contain chromium as a main component and aluminum and silicon when analyzed by an x-ray microanalyzer and show a high luminance under a metallurgical microscope are present in the cystal grain boundary containing the aluminum and chromium components.

Claim 14

A silicon carbide sintered body composed of 0.2 to 5% by weight, calculated as elemental aluminum, of aluminum nitride, 0.2 to 5% by weight, calculated as elemental rare earth, of a rare earth compound, 0.2 to 10% by weight, calculated as elemental chromium, of chromium carbide, and the balance being silicon carbide, wherein said silicon carbide is present in the sintered body as particles of the alpha-type crystal structure which are substantially spherical and have an average diameter of 0.5 to 2 micrometers, and particles which contain chromium as a main component and aluminum and silicon when analyzed by an X-ray microanalyzer and show a high luminance under a metallurgical microscope are present in the crystal grain boundary containing the aluminum, rare earth and chromium components.

Claim 15

A silicon carbide sintered body composed of 0.2 to 5% by weight, calculated as elemental aluminum, of aluminum nitride, 0.2 to 5% by weight, calculated as elemental rare earth, of a rare earth compound, 0.2 to 10% by weight, calculated as elemental chromium, of chromium carbide, and the balance being silicon carbide, wherein said silicon carbide is present in the sintered body as particles of the alpha-type crystal structure which are substantially spherical and have an average diameter of 0.5 to 2 micrometers, and particles which contain chromium as a main component and aluminum and silicon when analyzed by an X-ray microanalyzer and show a high luminance under a metallurgical microscope are present in the crystal grain boundary containing the aluminum, rare earth and chromium components.

Claim 16

A silicon carbide sintered body composed of silicon carbide, 0.2 to 5% by weight, as Al based on the entire sintered body, of aluminum nitride, 0.2 to 10% by weight, as Cr based on the entire sintered body, of chromium carbide (Cr 2 C 3 ) and 0.2 to 5% by weight, as elemental rare earth based on the entire sintered body, of a rare earth compound, wherein said silicon carbide is present in the sintered body as particles of the alpha-type crystal structure which are substantially spherical and have an average particle diameter of 0.5 to 2 micrometers, and particles which contain chromium as a main component and aluminum and silicon when analyzed by an X-ray microanalyzer and show a high luminance under a reflecton-type metal microscope are present in the crystal grain boundary containing the aluminum, rare earth and chromium components.

Claim 17

A silicon carbide sintered body composed of silicon carbide, 0.2 to 5% by weight, as Al based on the entire sintered body, of aluminum nitride, 0.2 to 10% by weight, as Cr based on the entire sintered body, of chromium carbide (Cr 2 C 3 ) and 0.2 to 5% by weight, as elemental rare earth based on the entire sintered body, of a rare earth compound, wherein said silicon carbide is present in the sintered body as particles of the alpha-type crystal structure which are substantially spherical and have an average particle diameter of 0.5 to 2 micrometers, and particles which contain chromium as a main component and aluminum and silicon when analyzed by an X-ray microanalyzer and show a high luminance under a reflecton-type metal microscope are present in the crystal grain boundary containing the aluminum, rare earth and chromium components.

Claim 18

A process for producing a silicon carbide sintered body, which comprises the steps of: (a) mixing a starting material in powder form composed of 3 to 6% by weight, calculated as elemental aluminum, of aluminum nitride, 0.4 to 3.5 by weight, calculated as elemental chromium, of chromium carbide, and the balance being silicon carbide; and (b) sintering the mixed powder into an integrated molded article.

Claim 19

A process for producing a silicon carbide sintered body, which comprises the steps of: (a) mixing a starting material in powder form composed of 3 to 6% by weight, calculated as elemental aluminum, of aluminum nitride, 0.4 to 3.5 by weight, calculated as elemental chromium, of chromium carbide, and the balance being silicon carbide; and (b) sintering the mixed powder into an integrated molded article.