Oxidation behavior of monolithic boron containing SiC/(Hf_0.5Ti_0.5)C/C composites consolidated by SPS

In the present study, the mechanical properties and the oxidation behavior of a SiC/(Hf_0.5Ti_0.5)C/C composite with and without boron addition are investigated. For the preparation of the monoliths, preceramic polymers are synthesized by single-source-precursor, and subsequently pyrolyzed. The resulting ceramic powders are consolidated by spark plasma sintering at 2200 °C to obtain dense pellets. The chemical modification of the single-source-precursor with a small amount of boron (about 0.16 wt%) leads to ceramic pellets with a more homogeneous microstructure. The hardness and the elastic modulus of dense SiC/(Hf_0.5Ti_0.5)C/C composites were found to be 27 and 336 GPa, respectively. The boron containing SiC/(Hf_0.5Ti_0.5)C/(B)C samples exhibited a hardness of 24 GPa and an elastic modulus of 299 GPa. Furthermore, the oxidation behavior was investigated via simultaneous thermal analysis up to 1500 °C for 20 h. The boron containing (Hf,Ti)C/SiC monoliths show about 20 % lower oxidation rates upon oxidation at 1400 °C.