Effect of surface modifications on the properties of silicon nitride ceramics

Conference · Mon Jun 01 04:00:00 EDT 1992

OSTI ID:10148272

Natansohn, S; Pasto, A E; Rourke, W J ^[1]

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1. 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: USDOE, Washington, DC (United States)
• DOE Contract Number: AC05-84OR21400
• OSTI ID: 10148272
• Report Number(s): CONF-920448--5; ON: DE92013848
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360203
360205
CORROSION AND EROSION
FABRICATION
FLEXURAL STRENGTH
FRACTURE PROPERTIES
HOT PRESSING
MECHANICAL PROPERTIES
OXIDATION
OXYGEN
POWDERS
SILICON NITRIDES
SINTERING
STRAIN RATE
TEMPERATURE RANGE 1000-4000 K
YTTRIUM OXIDES