Effect of 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 w/o yttria as 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.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-84OR21400
- OSTI ID:
- 5274985
- Report Number(s):
- CONF-920448-5; ON: DE92013848
- 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
CHALCOGENIDES
CHEMICAL REACTIONS
ELEMENTS
FABRICATION
FLEXURAL STRENGTH
FRACTURE PROPERTIES
HOT PRESSING
MATERIALS WORKING
MECHANICAL PROPERTIES
NITRIDES
NITROGEN COMPOUNDS
NONMETALS
OXIDATION
OXIDES
OXYGEN
OXYGEN COMPOUNDS
PNICTIDES
POWDERS
PRESSING
SILICON COMPOUNDS
SILICON NITRIDES
SINTERING
STRAIN RATE
TEMPERATURE RANGE
TEMPERATURE RANGE 1000-4000 K
TRANSITION ELEMENT COMPOUNDS
YTTRIUM COMPOUNDS
YTTRIUM OXIDES