Synthesis of Advanced Ceramics in the Systems Si-B-N and Si-B-N-C Employing Novel Precursor Compounds

Abstract

The reaction of Cl₃Si-NH-Si(CH₃)₃ with BCl₃ yields the novel compounds Cl₃Si-NH-BCl₂ and (Cl₃SiNH)₂-BCl. The ammonolysis of these monomeric precursors in liquid ammonia gives rise to highly crosslinked borosilicon imides. Pyrolysis of the polymeric imides in a stream of ammonia at 1250°C yields amorphous borosilicon nitrides with formal compositions of Si₃B₃N₇ and Si₆B₃N_u respectively. MAS-NMR, DTA/TG, SEM and TEM investigations reveal that the resulting materials are single phase. p]The reaction of the novel precursors with primary amines yields meltable and soluble polymers suitable for producing fibers or coatings. Subsequent pyrolysis in NH₃ leads also to amorphous borosilicon nitride. The physical and chemical properties of the new materials will be discussed.