Method of producing silicon-nitride-based sintered body
AssigneeNgk Spark Plug Co., Ltd.
InventorsTomohisa Kito, Katsuhisa Yabuta, Masakazu Watanabe
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Abstract
Silicon-nitride-based sintered body is produced by a primary sintering; applying a paste-like coating, in which a surface-homogenizing agent is at least one kind of inorganic constituents selected from the group consisting of C, Bn, AlN and Si.sub.3 N.sub.4 provided that C is present at least 5% by weight of the inorganic constituents, on a primary sintered body; and subsequently performing a secondary sintering under a pressure higher than that at the primary sintering.
Claims20
A method of producing a silicon-nitride-based sintered body comprising a primary sintering, and a secondary sintering under a pressure higher than that of the primary sintering, said method further comprising:
- applying a coating of a powdery surface-homogenizing agent in a paste form, in which the surface-homogenizing agent is at least two kinds of inorganic constituents selected from the group consisting of C, BN, AlN, and Si.sub.3 N.sub.4, provided that C is present in at least 5% by weight of the inorganic constituents, on a primary silicon-nitride-based sintered body;
- and subsequently performing a secondary sintering,
- wherein said primary sintering is performed until the relative density reaches a value of no less than 90% of theoretical density and said secondary sintering is performed under a gas pressure of no less than 10 atm and until the relative density reaches a value of no less than 97% of theoretical density.
A method of producing a silicon-nitride-based sintered body comprising a primary sintering and a secondary sintering under a pressure higher than that of the primary sintering, said method further comprising:
- applying a coating of a powdery surface-homogenizing agent comprising a mixture of carbon and boron nitride in a paste form, provided that C is present in at least 5% by weight of the surface-homogenizing agent, on a primary silicon-nitride-based sintered body;
- and subsequently performing a secondary sintering,
- wherein said primary sintering is performed until the relative density reaches a value of no less than 90% of theoretical density and said secondary sintering is performed under a gas pressure of no less than 10 atm and until the relative density reaches a value of no less than 97% of theoretical density.
Dependencies are inferred from the claim text.