Solid-State NMR Studies of the Preparation of Si−C−N Ceramics from Polysilylcarbodiimide Polymers

Multinuclear ( 29 Si, 13 C, 1 H) solid-state NMR and FTIR spectroscopy are employed to investigate the thermolysis of polymethylsilylcarbodiimide to the amorphous Si−C−N ceramic between room temperature and 1000 °C. During the present work two samples are examined that differ by the preparation route of the precursor polymer. The spectroscopic techniques are used to evaluate the structural intermediates that occur during the various stages of the thermolysis. With the knowledge of the structural components, reaction schemes are proposed that describe the transformation of the precursor polymers to the amorphous ceramic. The formation of the preceramic network is completed at about 500 °C. Above this temperature, a disintegration of the organic structural components takes place. The amorphous ceramics at 1000 °C thus consist of two major contributions: Si 3 N 4 units and polyaromatic, graphite-like structures. It is interesting to note that even at this temperature the samples contain a considerable amount of hydrogen, partially being located at the boundaries of the graphite-like regions.