Effect of powder surface modifications on the properties of silicon nitride ceramics
- GTE Labs., Inc., Waltham, MA (United States)
The effect of surface oxygen concentration of silicon nitride powders on the properties of resulting ceramics was studied. A high-purity silicon nitride powder was treated physically and chemically to modify its surface oxygen content. The resulting powders were hot-pressed into dense ceramics using 6 wt% yttria as a sintering aid. Strength and oxidation resistance of these ceramics were measured and correlated with the powder and ceramic compositions as well as the resulting intergranular phases. Results show that the phases developed in yttria-containing silicon nitride ceramics vary with slight changes in the initial powder oxygen content, as predicted, and that strength can be correlated to initial oxygen concentration. The mechanical strength vs oxygen content curve has a definite maximum; i.e., there is a small oxygen concentration range at which optimum ceramic strength is realized. Best results are obtained when the oxygen content is increased by thermal oxidation; other techniques such as chemical oxidation or addition of silica are not as effective, particularly in attaining high strength at elevated temperatures.
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 6077942
- Journal Information:
- Journal of the American Ceramic Society; (United States), Journal Name: Journal of the American Ceramic Society; (United States) Vol. 76:9; ISSN 0002-7820; ISSN JACTAW
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360203* -- Ceramics
Cermets
& Refractories-- Mechanical Properties
360205 -- Ceramics
Cermets
& Refractories-- Corrosion & Erosion
CORROSION PRODUCTS
ELEMENTS
FABRICATION
MECHANICAL PROPERTIES
METALLURGICAL EFFECTS
METALS
NITRIDES
NITROGEN COMPOUNDS
PNICTIDES
POWDERS
SILICON COMPOUNDS
SILICON NITRIDES
SINTERING
TENSILE PROPERTIES
TRANSITION ELEMENTS
YTTRIUM