Poly(borosilazanes) as precursors of SiBCN glasses: synthesis and high temperature properties

Poly(borosilazanes) with Si/B molar ratios of 3 and 9 were synthesized, via hydroboration, from vinyl-substituted cyclotrisilazane, [CH2CH(CH3)SiNH]3, and borane-trimethylamine adduct, (CH3)3N:BH3. The poly(borosilazanes) were pyrolyzed up to 1000 °C under nitrogen atmosphere, resulting in amorphous silicon boron carbonitride glasses (SiBCN). An almost complete retention of the B content was observed in these products. The high temperature behavior of SiBCN glasses was studied by X-ray diffraction and infrared spectroscopy. The glasses containing the larger amounts of boron remained amorphous to higher temperatures when compared with the parent B-free SiCN glass, which, at 1500 °C, crystallizes in SiC. At 2000 °C, the ceramic product derived from SiBCN was characterized as BN/SiC composite.