Raman Study of the Chemical and Thermal Degradation of As-Received and Sol-Gel Embedded Nicalon and Hi-Nicalon SiC Fibres 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 out in order to understand the fibre evolution during the synthesis of composites and their use in combustion environments. Assignments are discussed and a description of the fibre structure on the nanoscale is proposed. 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°C for Hi-Nicalon bands is consistent with a better thermal stability.