Investigations into the structural evolution of amorphous Si-C-N ceramics from precursors

The transformation of polysilazanes and polysilylcarbodiimides into amorpho us Si-C-N ceramics is investigated by solid state nuclear magnetic resonanc e, infrared and mass spectroscopy. A detailed description of the ceramizati on mechanisms and the phase formation during the polymer-ceramic transforma tion is derived from these studies. The structure of the obtained amorphous ceramic solids is characterized by means of X-ray and neutron small angle scattering. The obtained results reveal essential relations between the arc hitecture of the preceramic compounds and the corresponding amorphous stage s. The experimental data are combined with calculations based on the CALPHA D approach in order to provide a quantitative description for the thermoche mistry of the polymer systems and for the formation of the ceramic phases t hat evolve from the precursors.