Method of sintering articles of silicon nitride

Claim 2

In a method of pressureless sintering of silicon nitride (Si 3 N 4 ) wherein a formed powder compact is heated under an inert atmosphere without hot pressing to form a sintered article, the improvement comprising: grinding silicon nitride in an attritor mill using grinding bodies 1 to 3 mm in size of a material selected from the group consisting of a zirconium oxide material or silicate of aluminum, zirconium, beryllium, yttrium, and a combination thereof, to form a powder having an average particle size of 0.2 to 0.5 micrometers and a surface area of 10.5 to 35 square meters per gram; forming the powder compact using the ground powder; and heating the powder compact to a temperature in the range of 1700° C. to 1900° C. to sinter the compact into the sintered article.

Claim 3

The method of claim 1 wherein the grinding bodies are of zirconium oxide material.

Claim 4

The method of claim 1 wherein said grinding is carried out until the Si 3 N 4 has taken up to 10 weight-percent of said oxide grinding body material.

Claim 5

The method of claim 1 wherein the powder compact is heated to a temperature which is in a range of from in excess of 1750° C. up to 1900° C.

Claim 6

The method of claim 1 wherein the sintering temperature is from about 1850° C. to about 1900° C.

Claim 7

In a method of pressureless sintering of silicon nitride (Si 3 N 4 ) wherein a formed powder compact is heated under an inert atmosphere without hot pressing to form a sintered article, the improvement comprising: grinding silicon nitride in an attritor mill using grinding bodies of silicon nitride of 1 to 3 mm in size to form a powder having an average particle size of 0.2 to 0.05 micrometers and a surface area of 10.5 to 35 square meters per gram wherein there is added in an amount of up to 10 weight-percent of the total weight of the additive and the Si 3 N 4 employed as a grinding material, at least one of an oxide or silicate of aluminum, magnesium, beryllium and zirconium; forming the powder compact using the ground powder; and heating the powder compact to a temperature in the range of 1700° C. to 1900° C. to sinter the compact into the sintered article.

Claim 8

In a method of pressureless sintering of silicon nitride (Si 3 N 4 ) wherein a formed powder compact is heated under an inert atmosphere without hot pressing to form a sintered article, the improvement comprising: grinding silicon nitride in an attritor mill using grinding bodies of silicon nitride of 1 to 3 mm in size to form a powder having an average particle size of 0.2 to 0.05 micrometers and a surface area of 10.5 to 35 square meters per gram wherein there is added in an amount of up to 10 weight-percent of the total weight of the additive and the Si 3 N 4 employed as a grinding material, at least one of an oxide or silicate of aluminum, magnesium, beryllium and zirconium; forming the powder compact using the ground powder; and heating the powder compact to a temperature in the range of 1700° C. to 1900° C. to sinter the compact into the sintered article.

Claim 9

The method of claim 6 wherein the sintering temperature is from about 1850° C. to about 1900° C.

Claim 10

In a method of pressureless sintering of silicon nitride (Si 3 N 4 ) wherein a formed powder compact is heated under an inert atmosphere without hot pressing to form a sintered article, the improvement comprising: grinding silicon nitride in an attritor mill using grinding bodies of 1 to 3 mm in size of a material selected from the group consisting of an oxide or a silicate of aluminum, zirconium, beryllium, yttrium, and a combination thereof, to form a powder having an average particle size of 0.2 to 0.05 micrometers and a surface area of 10.5 to 35 square meters per gram; forming the powder compact using the ground powder; and heating the powder compact to a temperature in the range of 1700° C. to 1900° C. to sinter the compact into the sintered article, the sintered article having a lower limit value K IC of 4.3 MN/m 3/2 .

Claim 11

In a method of pressureless sintering of silicon nitride (Si 3 N 4 ) wherein a formed powder compact is heated under an inert atmosphere without hot pressing to form a sintered article, the improvement comprising: grinding silicon nitride in an attritor mill using grinding bodies of 1 to 3 mm in size of a material selected from the group consisting of an oxide or a silicate of aluminum, zirconium, beryllium, yttrium, and a combination thereof, to form a powder having an average particle size of 0.2 to 0.05 micrometers and a surface area of 10.5 to 35 square meters per gram; forming the powder compact using the ground powder; and heating the powder compact to a temperature in the range of 1700° C. to 1900° C. to sinter the compact into the sintered article, the sintered article having a lower limit value K IC of 4.3 MN/m 3/2 .

Claim 12

In a method of pressureless sintering of silicon nitride (Si 3 N 4 ) wherein a formed powder compact is heated under an inert atmosphere without hot pressing to form a sintered article, the improvement comprising: grinding silicon nitride in an attritor mill using grinding bodies of 1 to 3 mm in size and of a material of oxide or silicate of magnesium to form a powder having an average particle size of 0.2 to 0.05 micrometers and a surface area of 10.5 to 35 square meters per gram; forming the powder compact using the ground powder; and heating the powder compact to a temperature in the range of 1700° C. to 1900° C. to sinter the compact into the sintered article.

Claim 13

In a method of pressureless sintering of silicon nitride (Si 3 N 4 ) wherein a formed powder compact is heated under an inert atmosphere without hot pressing to form a sintered article, the improvement comprising: grinding silicon nitride in an attritor mill using grinding bodies of 1 to 3 mm in size and of a material of oxide or silicate of magnesium to form a powder having an average particle size of 0.2 to 0.05 micrometers and a surface area of 10.5 to 35 square meters per gram; forming the powder compact using the ground powder; and heating the powder compact to a temperature in the range of 1700° C. to 1900° C. to sinter the compact into the sintered article.