High strength three-dimensional silica fiber reinforced silicon nitride-based composites via polyhydridomethylsilazane pyrolysis

Three-dimensional silica fiber reinforced silicon nitride-based composites were fabricated through polyhydridomethylsilazane pyrolysis at 500-600 degrees C in flowing anhydrous ammonia atmosphere. The characteristics of the precursor-derived product, the mechanical properties and microstructures of the composites were investigated by FT-IR, elemental analysis, XRD, flexural strength and SEM. The polymer-derived product was a low-carbon near ceramic material with an empirical formula of Si1.0N1.38C0.01O0.04H0.78. Due to the low viscosity and high ceramic yield of the precursor, the as-received composites exhibited a relatively high density of 1.73 g/cm(3) after four infiltration-pyrolysis cycles. The composites were amorphous, showing a high flexural strength of 114.5 MPa and a non-brittle failure behavior. It was the controlled fiber/matrix interface that ensured the reinforcement ability of the silica fibers and the high strength of the composites. (C) 2006 Elsevier Ltd and Techna Group S.r.1. All rights reserved.