INTERMEDIATE-RANGE ORDER IN POLYMER-ROUTE Si-C-O FIBERS BY HIGH-ENERGY X-RAY DIFFRACTION AND REVERSE MONTE CARLO MODELLING

The atomic scale structure of polymer-derived Si-C-O ceramics fibers has been investigated by X-ray diffraction using high-energy synchrotron radiation at SPring-8 and reverse Monte Carlo (RMC) modelling. In the amorphous/microcrystalline Si-C-O fibers (NL400, heat-treated at 1000 similar to 1400 degrees C) the Si-atom prefers tetrahedral bonding to carbon and/or oxygen atoms, which leads to an inhomogeneous complex structure of SiC and Si-C-O domains and excess carbon region. By the RMC modelling, the basic structures of the Si-C-O fibers are the three-dimensionally connected SiC4-xOx (x = 0, 1, 2, 3, and 4) tetrahedral random-network structure which is the successive assembly of the SiC4-xOx tetrahedral unit which share elements (corners and edges) and the excess carbon atoms which are interconnected and distributed widely in the network cages.