Investigation of SiCO glasses synthesized with extensive ball milling

A new approach in the synthesis of silicon oxycarbide glasses (SiCO) has been investigated using mechanical alloying (MA). Crystalline silicon (Si), silica (SiO2) and graphite (C) were blended in order to obtain the three following compositions: M1 - stoichiometric SiCxO2(1-x), M2 - SiCxO2(1-x) + excess of C, M3 - SiCxO2(1-x) + excess of Si, and subsequently ball-milled during 130 h, i.e. with an energy transfer of 200.8 kJ g(-1). The integral crystallinity of the resulting powders was examined by X-ray diffraction (XRD) while transmission electron microscopy (TEM) was utilized to assess local crystallinity. In addition, the samples were characterized by Si-29 magic angle spinning nuclear magnetic resonance (Si-29 MAS-NMR) in order to determine whether a SiCO-like structure has been generated. According to MAS-NMR, the composition M1 and M2 does not show any amorphous silicon oxycarbide characteristic, but the composition M3 appears to be mainly an amorphous SiCO glass. The amorphization mechanism of the composition M3 was, therefore, investigated using XRD, high-resolution TEM and electron energy-loss spectroscopy. (C) 2002 Elsevier Science B.V. All rights reserved.