Conversion of N-methylpolyborosilzane to amorphous siliconboroncarbonitride

The amorphous ceramic 'SiBN3C' has been synthesized starting from 1,1-dichl oro-N-(trichlorosilyl)-boranamine (TADB) with N-methylpolyborosilazane as a polymeric intermediate. On heating the ceramic up to 1900 degrees C no mic rostructural changes occur. The thermal conversion of the preceramic polyme r was investigated by thermal analysis, infrared spectroscopy and nuclear m agnetic resonance spectroscopy. Surprisingly, the pyrolysis proceeds in thr ee clearly divided steps which can he assigned to completion of the polycon densation (200-350 degrees C), fragmentation (580-620 degrees C) and elimin ation of residual hydrogen (1000-1300 degrees C).