Synthesis, pyrolysis of a novel liquid SiBCN ceramic precursor and its application in ceramic matrix composites

SiBCN ceramic precursor, polyborosilazane, was synthesized through a novel method which used sodium borohydride as boron source. Vinyl silazane with Si-CI was converted to vinyl silazane with Si-H structure, followed by hydroboration reaction and subsequent high-temperature reaction to form soluble polyborosilazane liquid. The process of precursor-to-ceramic conversion was almost completed before 800 degrees C and the cross-linked polyborosilazane precursor exhibited higher ceramic yield 75.6% at 1200 degrees C. The SiBCN ceramic annealed at 1400 degrees C contained B-N, Si-N and Si-C bonds with smooth and dense surface and still retained principally amorphous structure up to 1600 degrees C. In addition, the viscosity of the polyborosilazane was 65 mPa.s, which can efficiently prepare ceramic matrix composite by means of precursor infiltration and pyrolysis (PIP). The density of as-obtained ceramic matrix composite (CMC) was 1.82 g/cm(3), and the average bending strength, bending modulus and tensile strength were 265.2 MPa, 37.5 GPa and 158.6 MPa, respectively. (C) 2016 Elsevier Ltd. All rights reserved.