Silicon nitride sintered body with region varying microstructure

Details Silicon nitride sintered body with region varying microstructure Silicon nitride sintered body with region varying microstructure

1998-12-28

2000-10-24

Mai, Ngoclan

Compositions: ceramic

Ceramic compositions

Refractory

264683, C04B 35584

Patent

active

061367389

ABSTRACT:
A silicon nitride sintered body is obtained by mixing 2.about.16 wt % of Yb.sub.2 O.sub.3 as a sintering additive with Si.sub.3 N.sub.4 powders including unavoidable impuirities, pressing the mixed powder into a desired form, and gas-pressure sintering the thusly pressed form, whereby an inner region of the sintered body has a fine microstructure, and an outer region thereof has a mixed microstructure in which elongated grains and fine grains co-exist and a method for manufacturing a silicon nitride sintered body, includes the steps of: adding and mixing 2.about.16 wt % of Yb.sub.2 O.sub.3 powder as a sintering additive into a silicon nitride (Si.sub.3 N.sub.4) powder; ball-milling the mixed powder to obtain a slurry; drying and classifying the slurry; press-forming the resultant powder in a die uniaxially and isostatically; and gas-pressure sintering the resultant compact body at a temperature in the range of 1800.about.2000.degree. C., whereby an inner region of the resultant sintered body has a fine microstructure, and an outer region of the resultant sintered body has a mixed microstructure in which elongated grains and fine grains co-exist.

REFERENCES:
patent: 4628039 (1986-12-01), Mizutani et al.
patent: 4806510 (1989-02-01), Kanai et al.
patent: 5545597 (1996-08-01), Yeckley
patent: 5648028 (1997-07-01), Miyake et al.
patent: 5921725 (1999-07-01), Kashiwagi et al.

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