Single-Source-Precursor Synthesis of Hafnium-Containing Ultrahigh-Temperature Ceramic Nanocomposites (UHTC-NCs)

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• 作者：Jia Yuan ; Stefania Hapis ; Hergen Breitzke ; Yeping Xu ; Claudia Fasel ; Hans-Joachim Kleebe ; Gerd Buntkowsky ; Ralf Riedel ; Emanuel Ionescu
• 刊名：Inorganic Chemistry
• 出版年：2014
• 出版时间：October 6, 2014
• 年：2014
• 卷：53
• 期：19
• 页码：10443-10455
• 全文大小：757K
• ISSN：1520-510X

文摘

Amorphous SiHfBCN ceramics were prepared from a commercial polysilazane (HTT 1800, AZ-EM), which was modified upon reactions with Hf(NEt₂)₄ and BH₃路SMe₂, and subsequently cross-linked and pyrolyzed. The prepared materials were investigated with respect to their chemical and phase composition, by means of spectroscopy techniques (Fourier transform infrared (FTIR), Raman, magic-angle spinning nuclear magnetic resonance (MAS NMR)), as well as X-ray diffraction (XRD) and transmission electron microscopy (TEM). Annealing experiments of the SiHfBCN samples in an inert gas atmosphere (Ar, N₂) at temperatures in the range of 1300鈥?700 掳C showed the conversion of the amorphous materials into nanostructured UHTC-NCs. Depending on the annealing atmosphere, HfC/HfB₂/SiC (annealing in argon) and HfN/Si₃N₄/SiBCN (annealing in nitrogen) nanocomposites were obtained. The results emphasize that the conversion of the single-phase SiHfBCN into UHTC-NCs is thermodynamically controlled, thus allowing for a knowledge-based preparative path toward nanostructured ultrahigh-temperature stable materials with adjusted compositions.