Plastic and nonmetallic article shaping or treating: processes – Outside of mold sintering or vitrifying of shaped inorganic... – Producing silicon nitride containing product
Patent
1995-06-02
1998-02-24
Czaja, Donald E.
Plastic and nonmetallic article shaping or treating: processes
Outside of mold sintering or vitrifying of shaped inorganic...
Producing silicon nitride containing product
264 5, 264 12, 264676, 501 971, 501 972, 501 981, 501 982, C04B 3500
Patent
active
057209197
ABSTRACT:
A method of making a shaped part of sintered silicon nitride is disclosed which includes preparing a mixture of Si.sub.3 N.sub.4 having a BET specific surface area in the range of from 2 to 15 m.sup.2 /g, having an O.sub.2 content of <1.5% by weight, a .beta.-form content of <2% by volume with finely divided Y.sub.2 O.sub.3, Al.sub.2 O.sub.3 or HfO.sub.2 and/or ZrO.sub.2, the total additive content being in the range of from 6 to 13% by weight, based on the total weight of the mixture, then mixing and milling mixture in a liquid dispersion medium, drying and agglomerating the suspension so produced, subsequently pressing, injection molding or redispersing and casting the agglomerated material obtained to make shaped parts, and finally sintering the shaped parts at temperatures between 1725.degree. and 1850.degree. C. under nitrogen for a period of up to 2 hours. The shaped parts produced according to the method have high mechanical strength and include at least 87% by weight Si.sub.3 N.sub.4 in the crystalline phases of the .alpha.- and/or .beta.-form, up to 13% by weight of an additive combination of Al.sub.2 O.sub.3 and Y.sub.2 O.sub.3, the Y.sub.2 O.sub.3 /Al.sub.2 O.sub.3 weight ratio being in the range of from 1.1 to 3.4, and additionally from 0 to 1.0% by weight of HfO.sub.2 and/or ZrO2. The shaped parts have a density of greater than 98% of the theoretically possible density and a bending strength of .gtoreq.850 MPa at room temperature and .gtoreq.800 MPa at a temperature of 1000.degree. C.
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Boberski Cornelia
Hamminger Rainer
Kruner Hartmut
Riedel Gunter
Colaianni Michael P.
Czaja Donald E.
Hoechst Aktiengesellschaft
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