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US 4,734,234 AGranted
Preparation of very strong and very heat-stable ceramic moldings of silicon nitride
AssigneeBASF SE
InventorHans-Josef Sterzel
Life of this patent
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Abstract
Pore-free, compact moldings of silicon nitride are produced by a method in which amorphous silicon nitride powder is compressed in a first stage at from 1200.degree. to 1350.degree. C. and from 50 to 600 kp/cm.sup.2 to give a glassy molding, and the silicon nitride is converted in a second stage to crystalline silicon nitride at from 1400.degree. to 1800.degree. C. without the use of pressure.
Claims4
A process for the production of compact, pore-free moldings of silicon nitride by sintering amorphous silicon nitride powder which comprises:
- compressing amorphous silicon nitride powder in the absence of sintering assistants in a first stage at from 1200.degree. to 1350.degree. C. and from 50 to 600 kp/cm.sup.2 to give a compact glassy molding;
- and converting the compact glassy molding in a second stage to crystalline silicon nitride at a temperature of from 1400.degree. to 1800.degree. C. without the use of pressure.
Dependencies are inferred from the claim text.