Oxidation mechanisms of mullite/ZrO{sub 2}/SiC-platelet composites

Conference · Sat Dec 31 04:00:00 EST 1994

OSTI ID:96596

Zangvil, A; Xu, Y; Fu, G ^[1]

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1. Univ. of Illinois, Urbana, IL (United States)

Reinforcement of ceramics with SiC whiskers or platelets has been receiving more and more attention because of the ability of these reinforcements to increase the fracture toughness and strength of composite materials. The stability of SiC whiskers or platelets within the ceramic matrix as well as in the environment is extremely important for high temperature applications. Alumina and mullite have been selected as oxide matrix materials for their excellent high-temperature stability and low oxygen permeabilities. Very comprehensive work has been performed on the oxidation of SiC-reinforced alumina and mullite matrix composites and mullite/zirconia matrix composites. Two oxidation modes were proposed in the literature. Mode I is defined as the case where oxygen can react with the whole SiC particle before it diffuses further into the matrix, resulting in a clear boundary between a layer with completely oxidized SiC particles and the underlying composite with unoxidized SiC particles, as shown in Fig. 1a. Mode II is the case where oxygen can deeply penetrate into the matrix before SiC particles in the outer region are completely oxidized, leaving a long range of partially oxidized SiC particles behind, as shown in Fig. 1b. Mode I was found in mullite/SiC-whisker and mullite/Mg-PSA/SiC-whisker composites while mode II was observed in mullite/Y-PSZ/SiC-whisker composites. These cases were qualitatively interpreted on the basis of the relationship between oxygen diffusivities in the matrix and in the oxide layer.

• DOE Contract Number: FG02-91ER45439
• OSTI ID: 96596
• Report Number(s): CONF-940416--
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
DIFFUSION
FRACTURE PROPERTIES
HOT PRESSING
MATHEMATICAL MODELS
MICROSTRUCTURE
MULLITE
OXIDATION
SILICON CARBIDES
WHISKERS
ZIRCONIUM OXIDES