Preparation and high-temperature performance of HfC-based nanocomposites derived from precursor with Hf-(O,N) bonds |
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| Affiliation: | 1. School of Material Science and Engineering, China University of Mining and Technology, Xuzhou City 221116, PR China;2. Institute of Materials, Ningbo University of Technology, Ningbo City 315016, PR China;1. Université Bordeaux, LCTS, UMR5801, F-33600 Pessac, France;2. CEA, DAM, Le Ripault, F-37260 Monts, France;1. School of Materials Science and Engineering, Pusan National University, Busan 609-735, Republic of Korea;2. Division of Powder/Ceramics Research, Korea Institute of Materials Science, Changwon 641-831, Republic of Korea;3. School of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450001, China |
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| Abstract: | A novel precursor was synthesized by reacting hafnium chloride with dicyandiamide and dimethylformamide. The precursor was characterized via FT-IR and NMR, as well as TG. Subsequently, the precursor was annealed in Ar over a range of temperatures from 1000 °C to 2000 °C, and the microstructural evolution of the ceramics was investigated by XRD, XPS, and TEM. The results show that the carbothermal reduction of the precursor starts at 1150 °C and the ceramic yields at 1500 °C reach 44.6 wt%. The obtained powders exhibit a uniform distribution and are composed of N-doped HfC and graphite. The N-doped structure postponed the oxidation of the HfC(N) ceramics. The HfC(N) ceramics were first oxidized to yield HfO2, carbon, and nitrogen, and then the carbon was oxidized with the evolution of CO2. The presented synthesis method is believed to be applicable to the preparation of other high-performance ceramics. |
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| Keywords: | Ultrahigh-temperature ceramics Precursor HfC Nanocomposites |
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