Microstructure evolution of precursors-derived SiCN ceramics upon thermal treatment between 1000 and 1400 °C

The microstructure evolution of different precursors-derived SiCN ceramics upon exposure at temperatures ranging between 1000 and 1400 °C has been investigated by means of transmission electron microscopy (TEM), electron energy-loss spectroscopy (EELS), X-ray energy dispersive spectroscopy (XEDS), Raman spectroscopy and Neutron scattering. The results of the present study indicate that these materials remain structurally amorphous and can, therefore, be considered stable against devitrification within this temperature range. However, the amorphous microstructure of these ceramics does undergo a short-range rearrangement. It is important to note that SiCN precursors with very similar chemical composition but different starting precursor architecture result in very similar amorphous network structures after exposure to 1400 °C. The presence of few localized crystalline regions, composed of Si3N4 crystals or turbostratic carbon features is explained in terms of gas-phase reactions occurring at residual closed pores between 1000 and 1400 °C.