Observation of Si in SiC composite fibers: A micro-Raman investigation

The chemical composition and microstructure of SiC composite fibers were studied by spatially resolved Raman spectroscopy. The spectra display a strong peak in the outer SiC layer identified as a Si signature and thus provide direct evidence of the presence of excess Si in the fiber composites. The Si crystallite size as well as the stress in the Si were estimated. Excess silicon has been previously suggested as the cause of the unusual creep and the anomalous thermal expansion behavior of these composites at high temperatures.