Sintering of Si3N4 under Nitrogen Pressure

A previous study on contract DAAG46-78-C-0017 showed that a sintered Si3N4 dot 15Y2O3 material similar in oxidation resistance to hot-pressed si3N4 could be prepared by minimizing the A12O3 content in the sample while maintaining high densities. This was achieved by using a high surface area SN402 S...

Full description

Saved in:
Bibliographic Details
Main Authors: Galasso,F S, Veltri,R D
Format: Report
Language:English
Subjects:
ALUMINUM OXIDES
CERAMIC MATERIALS
Ceramics, Refractories and Glass
CHEMICAL COMPOSITION
COLD WORKING
DENSITY
Fabrication Metallurgy
HIGH PRESSURE
HIGH TEMPERATURE
ISOSTATIC PRESSING
Mechanics
NITROGEN
OXIDATION RESISTANCE
POWDERS
RUPTURE
SHRINKAGE
SILICON NITRIDES
SINTERING
STRENGTH(GENERAL)
YTTRIUM
Online Access:Request full text
Tags: Add Tag
No Tags, Be the first to tag this record!
Description
Summary:A previous study on contract DAAG46-78-C-0017 showed that a sintered Si3N4 dot 15Y2O3 material similar in oxidation resistance to hot-pressed si3N4 could be prepared by minimizing the A12O3 content in the sample while maintaining high densities. This was achieved by using a high surface area SN402 Si3N4 powder and a high nitrogen overpressure during high temperature (1800C) sintering. In this study attempts were made to reduce the amount of Y2O3 as well as the Al2O3 in the mixtures to improve the oxidation resistance of the samples still further, but it was found that it was more difficult to obtain high densities for these materials than it was for Si3N4 dot 15Y2O3 materials. For that reason, preliminary measurements were made on samples containing 15% Y2O3. Strength measurements on as-pressed bars which were cold isostatic pressed and sintered showed that a Si3N4, dot 15Y2O3, dot 1Al2O3 material with a modulus of rupture as high as 514 MPa (75 ksi) could be prepared. (Author) See also Rept. no. UTRC/R80-914905-6.