Processing and properties of C/Si-B-C-N fiber-reinforced ceramic matrix composites prepared by precursor impregnation and pyrolysis

The fabrication of C/Si-B-C-N fiber reinforced ceramic matrix composites (FRCs) is reported. The processing basically involves three individual steps: (i) vacuum-assisted infiltration of a liquid two-component Si-B-C-N precursor into stacked woven carbon fiber fabrics, (ii) stepwise thermal cross-linking and (iii) thermal transformation of the polymer matrix composite into a ceramic matrix composite. Repeated polymer infiltration/pyrolysis cycles resulted in FRCs with 89% relative density. The average bending strength of the FRCs was 255 MPa and considerable fiber pull-out was observed throughout the fractured surfaces. The composite retained its strengths upon bending even at 1500 degrees C in argon and there was no evidence for brittle fracture. The flexural creep strain of the composite at 1400 degrees C was 0.55%. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.