PHOTOEMISSION AND X-RAY-ABSORPTION STUDY OF BORON-CARBIDE AND ITS SURFACE THERMAL-STABILITY

We present a photoemission and x-ray-absorption study on boron carbide which identifies the spectroscopic features of this material, discuss ing them in connection with current structural models. A study on the surface thermal stability is also performed, revealing that despite th e high melting point of boron carbide (similar to 2600 K), significant surface modifications occur in the material at about 1800 K. At this temperature the surface becomes covered with a graphite layer formed f rom bulk segregation of carbon, leaving boron-rich boron carbide burie d beneath the graphitic surface.