Toughened {beta}-SiC composites with alumina-coated {alpha}-SiC platelets
- Lawrence Berkeley Lab., CA (United States). Materials Science Division
Composites of {alpha}-silicon carbide platelets in {beta}-silicon carbide are prepared by applying alumina coatings on platelets via aqueous solutions. SiC as both matrix and strengthening phase provides matching CTE and chemical compatibility for high temperature applications. The alumina coating prevents physical interaction between the {alpha} and {beta} SiC, enhances densification during sintering, and provides a weak interface which promotes fracture toughness through crack deflection and platelet pullout. With additives of Al, B, and C, nearly full density of the composites is obtained at 1,650 C and 50 MPa for 0.5 hr. Fracture toughness of >7 MPa{radical}m and bend strengths of >700 MPa, are achieved for composites containing 20 vol.% platelets. The properties` dependence on processing conditions requires detailed microstructural analyses involving electron microscopies and spectroscopies (SEM, HR-TEM, AES, and EELS). Major foci of these analyses are the alumina/platelet interface, the role of sintering additives, and possible interfacial layers at the matrix SiC grain boundaries.
- OSTI ID:
- 62969
- Report Number(s):
- CONF-941016--; ISBN 0-87339-247-7
- Country of Publication:
- United States
- Language:
- English
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