Synthesis and pyrolysis of polysilazane precursors containing linear-cyclic structures for Si/N/C-based ceramics

A new kind of polysilazane precursor containing linear-cyclic structure was synthesized from the de-lithium chloride condensation reaction of hexameth yleyelotrisilazane lithium salts (D-3(NLi)) and 1,3-dichlorotetraorganoclis ilazanes [(ClR1R2Si)(2)NH]. Pyrolyses of these precursors and some comparab le linear polysilazanes were carried out at 900 degreesC in nitrogen. The r esults indicated that the existence of linear-cyclic structure in precursor s provided relatively crosslinked or branched structures, which were helpfu l for improving ceramic yields. The precursor containing a linear-cyclic st ructure as well as reactive vinyl groups gave the highest pyrolytic yields. (C) 2001 John Wiley & Sons, Inc.