Method of manufacturing a sintered material based on silicon nitride, and material obtained by the method

Claim 3

A method according to claim 1, wherein the initial mixture of silicon aluminum and yttrium oxide powders is prepared by suspending the powders in a solvent, then concentrating the suspension by centrifuging, and then drying it.

Claim 4

A method according to claim 2, wherein the mixture of powders suspended in the solvent is crushed using alumina balls.

Claim 5

A method according to claim 1, wherein the initial nitriding is performed in the presence of a gas which is rich in nitrogen and to which a small quantity of carbon oxide has been added.

Claim 6

A method according to claim 4, wherein the carbon oxide is obtained by performing the nitriding in a graphite furnace.

Claim 7

A method according to claim 1, wherein the initial nitriding is performed by heating the mixture of powders to a temperature in the range of 1300° C. to 1450° C. for a period of six hours.

Claim 8

A method according to claim 1, wherein the mixture of nitrided powders is crushed until the average particle size is less than 1 micron.

Claim 9

A method according to claim 7, wherein the crushing takes place in an aqueous medium using steel balls.

Claim 10

A silicon nitride based sintered material of specific mass greater than 95% of the theretical specific mass obtained by natural sintering in the presence of a small quantity of yttrium oxide according to the method comprising the steps of: mixing silicon powder with relatively small quantities of aluminum powder and yttrium oxide powder; substantially totally nitriding the mixture of powders; re-crushing the nitrided mixture of powders; shaping the re-crushed powders; and sintering the shaped re-crushed powders in a nitrogen atmosphere; and wherein said material consists essentially of a crystaline phase having crystal parameters close to those of beta silicon nitride, and a vitreous phase rich in yttrium oxide, the combination of the two phases consisting essentially of a mixture of silicon nitride and aluminum nitride with 90% to 100% by weight silicon nitride, and 0% to 10% aluminum nitride, together with 1% to 10% yttrium oxide by weight relative to the total weight of the nitrides.

Claim 11

A silicon nitride based sintered material of specific mass greater than 95% of the theretical specific mass obtained by natural sintering in the presence of a small quantity of yttrium oxide according to the method comprising the steps of: mixing silicon powder with relatively small quantities of aluminum powder and yttrium oxide powder; substantially totally nitriding the mixture of powders; re-crushing the nitrided mixture of powders; shaping the re-crushed powders; and sintering the shaped re-crushed powders in a nitrogen atmosphere; and wherein said material consists essentially of a crystaline phase having crystal parameters close to those of beta silicon nitride, and a vitreous phase rich in yttrium oxide, the combination of the two phases consisting essentially of a mixture of silicon nitride and aluminum nitride with 90% to 100% by weight silicon nitride, and 0% to 10% aluminum nitride, together with 1% to 10% yttrium oxide by weight relative to the total weight of the nitrides.