Processing and properties of SiC whisker reinforced Si sub 3 N sub 4 ceramic matrix composites

Miscellaneous · Tue Jan 01 00:00:00 EST 1991

OSTI ID:7039537

Nunn, S D

Silicon carbide whiskers reinforced silicon nitride ceramic matrix composites were pressureless sintered to high density by liquid phase sintering. Important processing parameters included: whisker dispersion by ultrasonic shear homogenization, particle refinement by attrition milling, pressure slip casting to obtain high greed densities, and sintering in a protective powder bed to limit decomposition. Composites with a {beta}20-Si{sub 3}N{sub 4} solid solution matrix containing 20 vol.% SiC whiskers were sintered to 98-100% theoretical density; composites having a Si{sub 3}N{sub 4} matrix containing YAG sintering aid were sintered to 98% of the theoretical density with 20 vol.% SiC whiskers, and 94% density with 30 vol.% SiC whiskers. Analysis of the pressureless sintered composites revealed orientation of the SiC whiskers and the Si{sub 3}N{sub 4} matrix grains. The mechanical properties of hot pressed Si{sub 3}N{sub 4} composites reinforced with 20 vol.% SiC whiskers were shown to depend on the characteristics of the intergranular phase. Variations in the properties of the composites were analyzed in terms of the amount and morphology of the secondary phase, and the development of internal residual stresses due to the thermal expansion mismatch between the sintering aid phase at the grain boundaries.

• Research Organization: Michigan Univ., Ann Arbor, MI (United States)
• OSTI ID: 7039537
• Resource Relation: Other Information: Thesis (Ph.D.)
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
MECHANICAL PROPERTIES
SINTERING
SILICON CARBIDES
SILICON NITRIDES
DENSITY
FRAGMENTATION
HOT PRESSING
MATRIX MATERIALS
QUANTITY RATIO
SOLID SOLUTIONS
WHISKERS
CARBIDES
CARBON COMPOUNDS
CRYSTALS
DISPERSIONS
FABRICATION
MATERIALS
MATERIALS WORKING
MIXTURES
MONOCRYSTALS
NITRIDES
NITROGEN COMPOUNDS
PHYSICAL PROPERTIES
PNICTIDES
PRESSING
SILICON COMPOUNDS
SOLUTIONS
360601* - Other Materials- Preparation & Manufacture
360603 - Materials- Properties