MicroRaman spectroscopy of protective coatings deposited onto C/C–SiC composites

Abstract

MicroRaman spectroscopy has been used in the present work to investigate the structure and composition of pyrolytic carbon (PyC) and SiC protective coatings formed under various chemical vapour deposition conditions. Analysis of spectra obtained during Raman line mapping experiments on samples with graded SixCy layer in the region of about 700–1000 cm−1 allows information to be extracted on different SiC polytypes. It was found that the graded SiC layered sample contained a mixture of 3C–SiC and 6H–SiC polytypes at the film/substrate interface, but for the major part of this layer the 3C–SiC ( β-SiC) phase predominates. For pure PyC films, it was found that the formation of PyC layer begins at 1200°C and the layer formed at this temperature is more uniform with slightly larger crystallite size (∼3 nm) compared to that in the layer formed at 1300°C.

Microstructural Analysis of Novel Preceramic Paper-Derived SiCf/SiC Composites

“…Raman scattering spectroscopy can be used to obtain information on the microstructure of materials using different spectral characteristics, such as position of peak, intensity of peak, full width at half maximum (FWHM) of peak, etc. [31]. Furthermore, with the exception of 2H and 3C-SiC, all SiC polytypes are constructed of a mixture of cubic and hexagonal stacking of SiC double layers, from which specific Raman spectra can be derived [32], information on the presence of different polytypes in the SiC specimens can be obtained [18].…”