QUANTITATIVE-ANALYSIS OF NICALON FIBERS IN TEM BY EDXS AND EELS

The global and local chemical composition of Nicalon fibres present in as- fabricated and annealed SiC-C-SiC composites are analysed by Analytical Transmission Electron Microscopy. EDXS, EELS, HREM and electron diffraction are used to characterise the fibre, which consists of different nanophases containing carbon, oxygen and silicon. Special attention is paid to the quantitative analysis of carbon and oxygen; different data treatment in EDXS and EELS are evaluated and compared. The limitations of the analysis techniques are discussed. The global composition of the core and the periphery of the fibre in the as-fabricated composite is determined to be: 57.5 wt% Si, 29 wt% C, 13.5 wt% O (38.6at% Si, 45.5at% C, 15.9at% O) and 53 wt% Si, 32 wt% C, 15 wt% O (34.4at% Si, 48.5at% C, 17.1at% C), respectively. After annealing in atmospheres with different oxygen partial pressures, the global oxygen content in the (fibre changes. The fibre constituents are silicon carbide nanocrystals, graphite units and an amorphous silicon oxycarbide phase.