Nanometric Si/C/N Powders : EXAFS Study at the Silicon K Edge

Abstract
Preceramic nanosized Si/C/N powders with a variable C/N ratio have been investigated by X-ray absorption spectroscopy at the silicon K edge. By combining XANES and EXAFS analysis results, we have proposed a model for the local structure of the as-prepared powders. This structural amorphous model has been tested through multiple scattering calculations using the FEFF code calculations. The evolution during the pyrolysis process is followed, specially for intermediate C/N values for which a delay in the crystallisation temperature occurs. Before the formation of very small crystallites, one can observe a reorganisation of the short range atomic structure.