Microstructure design, processing and oxidation/ablation behavior of advanced C/C composites modified by polymer-derived ultra-high temperature ceramics
Coating and Surface Technology
Final Report Abstract
This project explores the modification of Si-based polymers with transition metals in order to archive a preceramic polymer that can be used for coating or matrix modification of composites. Si-based ceramics are used as protective coatings of carbon composites in harsh and oxidative environments. The modified polymer derived ceramics are therefore consolidated and used for oxidation tests. Within this project, two preceramic polymers (Durazane 1800 and SMP-10) were successfully modified with tetrakis(diethylamido)hafnium(IV) (TDEAH), tetrakis(dimethylamido)titanium(IV) (TDMAT), as well as small amounts of borane dimethyl sulfide complex (BMS). The modification occurs due to the reaction of the transition metal amido complexes with the Si-H groups of the polymer and hydroboration of the allyl groups attached to Si of the polymer upon addition of the borane. The crosslinking and high temperature behaviour of the modified preceramic polymers is investigated by FTIR, XRD, SEM, and Raman spectroscopy. Annealing of Si(Hf,Ti)CN samples (modified Durazane 1800) at temperatures above 1700 °C leads to the consumption of carbon through carbothermal reaction. For SiHfTiC(N) (modified SMP-10) the free carbon evolves from amorphous to highly disordered / turbostratic carbon upon annealing at higher temperatures. Furthermore, the amorphous ceramic powders crystallize at higher temperatures and a phase separation in SiC and transition metal carbides occurs. The ceramic powders were consolidated by SPS. Ceramic monoliths based on modified Durazane 1800 showed an inhomogeneous microstructure and were therefore not selected for further oxidation experiments. Six ceramic monoliths based on SMP-10 with different compositions were used for oxidation experiments. The best oxidation resistance was shown by SiC/(Hf0.5Ti0.5)C/C and SiC/(Hf0.5Ti0.5)C/(B)C at 1200 and 1400 °C. A protective oxide layer composed of different beneficial oxides such as SiO2 and HfSiO4 prevents further oxidation of the ceramic bulk samples. Furthermore, 2.5 D C/C composites were used for a polymer infiltration and pyrolysis (PIP) process.
Publications
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Phase evolution and oxidation resistance of Si3N4/HfB2/HfB C N1–– ceramic nanocomposites prepared from tailored preceramic polymers. Ceramics International, 49(21), 34164-34172.
Li, Wei; Widenmeyer, Marc; Ding, Jinxue; Jiang, Tianshu; Feldmann, Laura; Liu, Jiongjie; Molina-Luna, Leopoldo; Weidenkaff, Anke; Riedel, Ralf & Yu, Zhaoju
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Materials design of silicon based ceramic coatings for high temperature oxidation protection. Materials Science and Engineering: R: Reports, 163, 100936.
Liu, Bing; Sun, Jia; Guo, Lingxiang; Shi, Huilun; Feng, Guanghui; Feldmann, Laura; Yin, Xuemin; Riedel, Ralf; Fu, Qiangang & Li, Hejun
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Oxidation behavior of monolithic boron containing SiC/(Hf0.5Ti0.5)C/C composites consolidated by SPS. Journal of the European Ceramic Society, 45(15), 117607.
Feldmann, Laura; Zhang, Yuyu; Zhang, Xuemeng; Sun, Jia & Riedel, Ralf
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Ablation behavior of Hf-Zr-modified silicon-based ceramic coatings prepared by polymer derived ceramics and gaseous silicon infiltration. Chinese Journal of Aeronautics, 39(5), 104010.
GUO, Lingxiang; DONG, Yaojun; WANG, Yuqi; HUANG, Shiwei; FELDMANN, Laura; RIEDEL, Ralf & SUN, Jia
