Fabrication, phase transformation studies and characterization of SiC-AlN-Al sub 2 OC ceramics

Technical Report · Sun Jan 12 04:00:00 EST 1992

DOI:https://doi.org/10.2172/5932831· OSTI ID:5932831

Virkar, A V

SiC and AlN are two of the important high temperature structural ceramics. AlN and the 2H polytype of SiC are isostructural. Prior work has shown that they form an extension solid solution at temperatures {ge} 2000{degrees}C. At lower temperatures, the solid solution can undergo phase separation. Additionally, Al{sub 2}OC is also isostructural and can form extensive solid solutions with SiC and AlN. The formation of solid solutions in such refractory materials as well as the tendency to undergo diffusional phase transformations suggests that a potential exists to improve properties through alloying. The principal objective of the proposed work is to examine phase relations, phase transformations, the resulting precipitate morphologies and their influence on mechanical properties of SiC-AlN-Al{sub 2}OC ceramics. Formation of modulated structures have been documented in SiC-AlN ceramics in our work. It has been shown that modulations occur along directions other than the (0001) direction and this results in the formation of a tweed type of a microstructure. In the AlN-Al{sub 2}OC system, the occurrence of cellular precipitates as well as coherent, disc-shaped precipitates has been observed. During the past year, work has progressed in the following areas: (1) Phase separation in SiC-AlN system: The effect of coherency strain energy on the precipitate morphology. (2) High temperature creep of SiC-AlN ceramics containing modulated structures and SiC-Al{sub 2}OC ceramics. (3) Fabrication and characterization of damage-resistant SiC-AlN ceramics. Three manuscripts have been submitted for publication.

• Research Organization: Utah Univ., Salt Lake City, UT (United States). Dept. of Materials Science and Engineering
• Sponsoring Organization: DOE; USDOE, Washington, DC (United States)
• DOE Contract Number: FG02-87ER45286
• OSTI ID: 5932831
• Report Number(s): DOE/ER/45286-5; ON: DE92007540
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360201* -- Ceramics
Cermets
& Refractories-- Preparation & Fabrication
360202 -- Ceramics
Cermets
& Refractories-- Structure & Phase Studies
ALUMINIUM COMPOUNDS
ALUMINIUM NITRIDES
CARBIDES
CARBON COMPOUNDS
CREEP
CRYSTAL STRUCTURE
DOCUMENT TYPES
FABRICATION
HOT PRESSING
MATERIALS WORKING
MECHANICAL PROPERTIES
MICROSTRUCTURE
MORPHOLOGY
NITRIDES
NITROGEN COMPOUNDS
PHASE TRANSFORMATIONS
PNICTIDES
PRESSING
PROGRESS REPORT
SILICON CARBIDES
SILICON COMPOUNDS