Microscopic mechanisms of oxidation in SiC-whisker-reinforced mullite/ZrO{sub 2} matrix composites

Journal Article · Fri Oct 01 04:00:00 EDT 1999 · Journal of the American Ceramic Society

OSTI ID:20000445

Lin, C C; Zangvil, A; Ruh, R

The oxidation of SiC whiskers, contained in alkoxide-derived mullite-based matrices and exposed in air at 1000--1350 C for up to 1000 h, has been studied by analytical TEM, high-resolution SEM, and XRD. Silicon carbide whiskers were effectively protected from oxidation when embedded in a pure mullite matrix, but oxidized considerably when embedded in mullite/ZrO{sub 2} matrices. The oxidation mechanisms varied with matrix composition and exposure temperature. At 1350 C the amorphous layer first crystallized as cristobalite, then gradually incorporated alumina. At later times, the mullite portion of the mullite/ZrO{sub 2} matrix dissolved extensively into the layer. Also, the zirconia particles reacted with silica to form zircon. At 1200 C less extensive interdiffusion and chemical reaction occurred, and the silica layer devitrified into cristobalite and quartz. At 1000 C no interdiffusion or chemical reaction was seen, and the silica layer tended to devitrify into quartz. The thickness of the oxide layer around a SiC whisker in a particular matrix depended on the morphology and composition of grains abutting it or adjacent to it.

• Research Organization: National Chiao Tung Univ., Hsinchu (TW)
• Sponsoring Organization: US Department of Energy
• OSTI ID: 20000445
• Journal Information: Journal of the American Ceramic Society, Journal Name: Journal of the American Ceramic Society Journal Issue: 10 Vol. 82; ISSN 0002-7820; ISSN JACTAW
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
COMPOSITE MATERIALS
CONCENTRATION RATIO
MICROSCOPY
MULLITE
OXIDATION
SILICON CARBIDES
TEMPERATURE RANGE 1000-4000 K
X-RAY DIFFRACTION
ZIRCONIUM OXIDES