Characterization of polymer-derived ceramers subjected to wet-etching and the evolution of the carbon phase during thermal conversion

Abstract

The present work is focused on revealing the structural, textural and electrochemical characteristics of the carbon phases developed during the pyrolysis of commercial preceramic precursors in the presence of cobalt. At intermediate pyrolysis temperature, Cobalt is capable of forming labile carbides into the preceramic polymer network that, upon decomposition, lead to the formation of ordered carbonaceous structures during the thermal conversion. Etching with HF removes the undesirable SiO2-like phase allowing, for the first time, to detect the presence of Co-carbon nano-onions (Co@CNO) in silicon oxycarbide ceramers. These ordered Co@CNO were formed at pyrolysis temperatures ranged between 700 and 800 °C but a further increase of the temperature induces a significant disorder into the carbon phase and incorporation of the C in the ceramic structure, as deduced from the spectroscopic characterization of these materials.