A new borazine-type single source precursor for Si/B/N/C ceramics

The new borazine derivative [ B{CH(CH3)(SiCl3)} NH](3) (TSEB) was prepared by reacting Cl3Si - CH(CH3) - BCl2 (TSDE) with hexamethyldisilazane (hmds) at ambient conditions. TSEB was characterized by infrared spectroscopy (IR), nuclear magnetic resonance (NMR), and by mass spectrometry (MS). The specially designed molecule serves as a single source precursor for the synthesis of a highly durable Si/B/N/ C ceramic material via the well known 'polymer route'. Pursuing this philosophy, polymerization of TSEB with methylamine as the cross-linking reagent has lead to a highly homogeneous pre-ceramic polymer, which was further characterized by spectroscopic methods. Subsequent thermal degradation of the as-obtained polyborocarbosilazane was monitored by means of DTA/TG/MS up to 1400 degrees C. The resulting amorphous silicon boron carbonitride of the approximate elemental composition Si3B3N5C4 exhibits an outstanding thermal durability at 2000 degrees C under inert conditions and is also stable in pure oxygen up to at least 1300 degrees C. The ceramic material still contains borazine rings from the TSEB precursor molecule embedded in the covalent Si/B/N/ C network, acting as rigid structural units which reinforce the ceramic material on an atomic scale