Toughening mechanisms in mullite/zirconia composites

Thesis/Dissertation · Thu Dec 31 23:00:00 EST 1987

OSTI ID:7004729

Srikrishna, K

A study of reaction-sintered mullite/zirconia composites (3Al{sub 2}O{sub 3}{center dot}2SiO{sub 2}-ZrO{sub 2}) was carried out to understand the relationships between processing, microstructure, and mechanical properties. The potential for production of economically attractive and technologically significant high-toughness ceramic composites in the system Al{sub 2}O{sub 3}-SiO{sub 2}-ZrO{sub 2} is the motivation for this study. The microstructure and mechanical properties of reaction-sintered mullite/zirconia composites with TiO{sub 2} added as a sintering aid, were characterized. The composites exhibited a fracture toughness of {approximately}5.5 MPa{radical}m and a flexural strength of {approximately}300 MPa. The microstructure consisted of equiaxed monoclinic ZrO{sub 2} grains uniformly dispersed in a mullite matrix, predominantly at intergranular sites. A small fraction (<20%) of intragranular tetragonal ZrO{sub 2} was also observed. The presence, extent, and evolution of the ZrO{sub 2} phases were found to be a strong function of the amount of TiO{sub 2} added. The reaction-sintering route produced a ZrO{sub 2} which was 80% monoclinic and the fracture toughness of the composites was independent of the tetragonal ZrO{sub 2} content. The mullite matrix in the reaction-sintered composite was determined to have a disordered vacancy structure.

• Research Organization: California Univ., Berkeley, CA (USA)
• OSTI ID: 7004729
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360603* -- Materials-- Properties
CERAMICS
CHALCOGENIDES
COMPOSITE MATERIALS
CRYSTAL STRUCTURE
FABRICATION
FRACTURE PROPERTIES
INORGANIC ION EXCHANGERS
ION EXCHANGE MATERIALS
MATERIALS
MECHANICAL PROPERTIES
MICROSTRUCTURE
MINERALS
MULLITE
OXIDE MINERALS
OXIDES
OXYGEN COMPOUNDS
SINTERING
TRANSITION ELEMENT COMPOUNDS
ZIRCONIUM COMPOUNDS
ZIRCONIUM OXIDES