Oxidation Resistance and Microstructural Analysis of Polymer-Derived (Hf_xTa_1−x)C/SiC Ceramic Nanocomposites

N.-C. Petry, N. Thor, J. Bernauer, A.S. Ulrich, E. Ionescu, R. Riedel, A. Pundt, M.C. Galetz, M. Lepple

Adv. Eng. Mater. 26 (2024), 2302023, DOI: 10.1002/adem.202302023

petry2024

EPMA oxygen maps of cross sections of (Hf_xTa_1−x)C/SiC c–f) and SiC a,b) polymer-derived monoliths after exposure at 1200 °C (a,c,e) and 1400 °C (b,d,f) for 50 h in synthetic air.

Reprinted from Adv. Eng. Mater. with permission from Wiley according to the Creative Commons license.

The oxidation behavior of polymer-derived (Hf_xTa_1−x)C/SiC nanocomposites at 1200 °C and 1400 °C for up to 100 h is investigated in this work. Overall, the chemical modification of the polycarbosilane-based precursor with Hf and Ta leads to an improved oxidation behavior due to an increased densification. Shifting the Hf/Ta ratio from (Hf_0.2Ta_0.8)C/SiC to (Hf_0.7Ta_0.3)C/SiC results in an improved oxidation behavior due to Hf₆Ta₂O₁₇ formation and the reduction of Ta₂O₅ formation, which reduces cracking of the samples. The formation and microstructure of SiO₂ as well as the internal oxidation of (Hf_xTa_1−x)C precipitates is explained by thermodynamic and kinetic considerations.