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 prot ected the fibers in composite 2. The matrix contained traces of the hexagon al phase of celsian, which was concentrated in the neighborhood of fibers i n 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 degradati on of the fiber core in the composites.