AUGER-ELECTRON SPECTROSCOPY ANALYSIS OF SIC-WHISKER SURFACES AND SIC-WHISKER ALUMINA INTERFACES

Auger Electron Spectroscopy (AES) has been used to examine as-received and oxidized silicon carbide whiskers and their respective whisker/matrix interfaces after fabrication into SiC-whisker-reinforced alumina composites. As-received whisker surfaces exhibited a 2-3 nm-thick near-surface region that was C-rich. Oxygen was detected at the outer surface, but diminished to near zero within 25 nm of the surface. Oxidized whiskers had 60 nm-thick SiO2 surface layers, which was in agreement with the transmission electron microscopy observations. The whisker/matrix interfaces in both composites consisted of thin (<0.5 nm) layers of a C-Si-O noncrystalline material. The thick SiO2 layers on the oxidized whiskers were ejected from the interfaces during hot-pressing. It was concluded that (i) the higher toughness of the composite fabricated with as-received SiC whiskers may be related to the higher C and lower O in its SiCw/Al2O3 interfaces, and (ii) interface composition cannot be reliably predicted using the surface composition of free whiskers prior to fabrication.