RAMAN-STUDY OF THE CHEMICAL AND THERMAL-DEGRADATION OF AS-RECEIVED AND SOL-GEL EMBEDDED NICALON AND HI-NICALON SIC FIBERS USED IN CERAMIC-MATRIX COMPOSITES

Raman microprobe analysis of Nicalon NLM 202 and Hi-Nicalon fibres as a function of thermal treatments in various atmospheres was carried ou t in order to understand the fibre evolution during the synthesis of c omposites and their use in combustion environments. Assignments are di scussed and a description of the fibre structure on the nanoscale is p roposed. A comparison is made between surface and core evolution of as -received fibres and of fibres used in the sol-gel route. The plateau observed between 1200 and 1600 degrees C for Hi-Nicalon bands is consi stent with a better thermal stability. (C) 1997 by John Wiley & Sons, Ltd.