Effect of matrix liquid phase on interphase formation in SiC fibre-reinforced Si2N2O-Al2O3-CaO composites

Autor:	Robert F. Speyer, Hyun-Ho Shin, Y. Berta
Rok vydání:	1995
Předmět:	Aluminium oxides Materials science Mechanical Engineering chemistry.chemical_element Fracture mechanics Hot pressing Microstructure chemistry Mechanics of Materials Phase (matter) General Materials Science Interphase Composite material Carbon Eutectic system
Zdroj:	Journal of Materials Science. 30:5621-5631
ISSN:	1573-4803 0022-2461
DOI:	10.1007/bf00356695
Popis:	Matrix compositions based on Si2N2O, with Al2O3 and CaO additions, were used to hot press Nicalon SiC fibre-reinforced composites at 1600 °C. With both CaO and Al2O3 additions, eutectic melting formed an appreciable volume of liquid phase during hot pressing, which remained as a stable glassy phase in the cooled composites. This liquid phase fostered formation of ∼240 nm thick carbon-rich interphases between the fibres and the matrix. These interphases showed relatively low interfacial shear strength and resulted in composites which showed non-catastrophic, notch-independent fracture. Matrices using either Al2O3 or CaO did not form adequate liquid phase to form coarse interphases, and fracture was catastrophic in nature. Post-heat treatment of the composites at 1000 °C showed peripheral oxidation (removal of the carbon content of the interphase) indicating limited protection afforded when glassy phase was present in the matrix. Controlled cooling in the hot press did not cause the liquid regions to devitrify.
Databáze:	OpenAIRE
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