Thermally Durable Glass-Ceramic Matrix Composites
Abstract
The thrust of this program was to develop thermally durable ceramic matrix composites (CMCs) with enhanced thermostructural properties. Two approaches were investigated (1) BSG-doped, SiC whisker toughened MAS CMC's, and (2) Mica-interface CMCs. BSG-MAS CMCs have an MAS cordierite glass-ceramic matrix, and contain a borosilicate glass phase that protect in situ carbon interfaces from oxidation, as well as SiC whisker matrix addition that reduces microcracking upon mechanical loading. These materials were demonstrated in long-term tensile stress rupture to have increased levels of thermal durability, both at high and intermediate temperatures. BSG dopants were dominant at elevated temperatures, boron-modifying the in situ carbon layer and providing a viscous film protection of interfacial carbon layers present with the use of Nicalon fibers. SiC whisker matrix toughening was dominate at intermediate temperatures, reducing matrix microcracking and resulting in reduced pathways for environmental ingress into oxidatively unstable interfacial regions of the composite microstructure. Mica-interface CMCs replace interfacial carbon with an inherently oxidation resistant sheet-silicate mica. These Nicalon MAS glass-ceramic CMCs were shown to be free of oxidation embrittlement at intermediate temperatures. However, the sol-gel mica coatings were nonuniform, and showed evidence of environmental reactivity at elevated temperature.
Document Details
- Document Type
- Technical Report
- Publication Date
- Nov 14, 1997
- Accession Number
- ADB264406
Entities
People
- D. C. Lasen
- H. T. Godard
- J. M. Toms
- K. Chyung
- R. L. Stewart
- S. B. Dawes