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

Abstract

ABSTRACTThe 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 Si6B3Nu respectively. MAS-NMR, DTA/TG, SEM and TEM investigations reveal that the resulting materials are single phase.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.