Raman study of Hi-Nicalon-fiber-reinforced celsian composites: I, distribution and nanostructure of different phases

Hi-Nicalon-fiber-reinforced celsian-matrix composites were characterized by Raman spectroscopy and imaging, using several laser wavelengths. Composite 1 was reinforced by as-received fibers while coatings of p-BN and SiC protected the fibers in composite 2. The matrix contained traces of the hexagonal phase of celsian, which was concentrated in the neighborhood of fibers in composite 1. Some free silicon was evident in the coating of composite 2 which might have involved a IBN C SiC --> BNC + Si) "reaction" at the p-BN/SiC interface. Careful analysis of C-C peaks revealed no abnormal degradation of the fiber core in the composites.