Process for producing silicon nitride based articles of high fracture toughness and strength
- Marlboro, MA
- Acton, MA
A process for producing a silicon nitride-based article of improved fracture toughness and strength. The process involves densifying to at least 98% of theoretical density a mixture including (a) a bimodal silicon nitride powder blend consisting essentially of about 10-30% by weight of a first silicon nitride powder of an average particle size of about 0.2 .mu.m and a surface area of about 8-12 m.sup.2 /g, and about 70-90% by weight of a second silicon nitride powder of an average particle size of about 0.4-0.6 .mu.m and a surface area of about 2-4 m.sup.2 /g, (b) about 10-50 percent by volume, based on the volume of the densified article, of refractory whiskers or fibers having an aspect ratio of about 3-150 and having an equivalent diameter selected to produce in the densified article an equivalent diameter ratio of the whiskers or fibers to grains of silicon nitride of greater than 1.0, and (c) an effective amount of a suitable oxide densification aid. Optionally, the mixture may be blended with a binder and injection molded to form a green body, which then may be densified by, for example, hot isostatic pressing.
- Research Organization:
- LOCKHEED MARTIN ENRGY SYST INC
- DOE Contract Number:
- AC05-84OR21400
- Assignee:
- GTE Laboratories Incorporated (Waltham, MA)
- Patent Number(s):
- US 5047186
- OSTI ID:
- 867976
- Country of Publication:
- United States
- Language:
- English
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Process for producing silicon nitride based articles of high fracture toughness and strength
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10-30
10-50
2-4
3-150
4-0
70-90
8-12
98
amount
article
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aspect
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average
average particle
based
bimodal
binder
blend
blended
consisting
consisting essentially
densification
densified
densifying
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diameter
diameter ratio
effective
effective amount
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essentially
example
fibers
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grains
green
hot
hot isostatic
improved
improved fracture
including
injection
injection molded
involves
isostatic
isostatic pressing
mixture
mixture including
molded
nitride
nitride base
nitride powder
nitride-based
nitride-based article
optionally
oxide
particle
particle size
percent
powder
pressing
process
process involves
produce
producing
producing silicon
ratio
refractory
selected
silicon
silicon nitride
silicon nitride-
silicon nitride-based
size
strength
suitable
surface
theoretical
theoretical density
toughness
volume
weight
whiskers