Indentation analysis of elastic and plastic deformation of precursor-derived Si–C–N ceramics

Elastic and plastic deformation behavior of precursor-derived Si–C–N ceramics at room temperature under contact loading was investigated using nano- and microindentation experiments. The observed behavior showed striking similarities to that of anomalous silicate glasses and amorphous carbon based films. The elastic deformation was controlled by the overall rigidity of the material microstructure, that evolved with the increase in the network connectivity due to progressive dehydrogenation in the amorphous materials, and the formation and organization of turbostratic graphite and nanocrystalline SiC in the phase-separated materials. The plastic deformation of the amorphous materials displayed anomalous densification inducing appreciable strain hardening, which reduced with progressive phase separation in the materials. The contrasting evolution of elastic and plastic deformation work quantities in amorphous and phase-separated materials indicate that the plastic deformation in former materials was volume deformation-controlled whereas that in the latter materials was interface deformation-controlled.