Nanodomain growth in amorphous Si-C-N

Polymer-derived amorphous Si-C-N ceramics are phase separated into amorphous nanodomains after thermolysis. These nanodomains are expected to have a crucial importance for the extraordinary high temperature stability of these materials. We investigated nanodomain growth during isothermal annealing at 1400 degrees C using small angle X-ray scattering. The as-thermolyzed sample shows a domain radius of about 5 angstrom as determined from Guinier plots. During annealing, fast nanodomain growth up to 9 angstrom is observed for times up to 30h while for longer annealing times up to 165 h the growth considerably slows down, resulting in a domain size of 11 angstrom. The experimental data can be fitted by a model based on diffusion controlled domain growth and simultaneous slow-down of diffusion due to structural relaxation. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim