Single-source-precursor synthesis and high-temperature evolution of a boron-containing SiC/HfC ceramic nano/micro composite |
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Authors: | Qingbo Wen Zhaoju Yu Ralf Riedel Emanuel Ionescu |
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Affiliation: | 1. College of Materials, Key Laboratory of High Performance Ceramic Fibers, Ministry of Education, Xiamen University, Xiamen 361005, China;2. Technische Universität Darmstadt, Institut für Materialwissenschaft, Otto-Berndt-Straße 3, D-64287 Darmstadt, Germany;3. College of Materials, Fujian Key Laboratory of Advanced Materials (Xiamen University), Xiamen 361005, China |
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Abstract: | A boron-containing SiHfC(N,O) amorphous ceramic was synthesized upon pyrolysis of a single-source-precursor at 1000 °C in Ar atmosphere. The high-temperature microstructural evolution of the ceramic at high temperatures was studied using X-ray powder diffraction, Raman spectroscopy, solid-state nuclear magnetic resonance spectroscopy and transmission electron microscopy. The results show that the ceramic consists of an SiHfC(N,O)-based amorphous matrix and finely dispersed sp2-hybridized boron-containing carbon (i.e. ByC). High temperature annealing of ByC/SiHfC(N,O) leads to the precipitation of HfCxN1-x nanoparticles as well as to β-SiC crystallization. After annealing at temperatures beyond 1900 °C, HfB2 formation was observed. The incorporation of boron into SiHfC(N,O) leads to an increase of its sintering activity, consequently providing dense materials possessing improved mechanical properties as compared to those of boron-free SiC/HfC. Thus, hardness and elastic modulus values up to 25.7 ± 5.3 and 344.7 ± 43.0 GPa, respectively, were measured for the dense monolithic SiC/HfCxN1-x/HfB2/C ceramic nano/micro composite. |
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Keywords: | Polymer-derived ceramic nanocomposites Silicon carbide Hafnium carbide High-temperature UHTCs |
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