Efficacy of a ZrB2–SiC matrix in protecting C fibres from oxidation in novel UHTCMC materials

A series of high-density ceramic composites with carbon fibre content between 40 and 65% and ultra-refractory ceramic matrix was produced by slurry infiltration and hot pressing. The matrix consisted of ZrB2–10 vol% SiC or ZrB2–40 vol% SiC ceramic mixtures. Water–based and polymer–based routes were tested to analyse the effects on microstructure, mechanical properties and oxidation resistance at 1650 °C in air. Changing the process and/or the processing parameters was found to affect the final composition, the amount of residual porosity, the matrix/fibre adhesion. Composites with nearly fully dense matrix and optimized infiltration of fibre preforms were found to possess the highest strength (240 MPa) and oxidation resistance. Composites with a weak interface and higher porosity in the matrix showed higher toughness (up to 12 MPa m0.5) but were more prone to oxidation and erosion.