首页|(162989)Synthesis and ceramisation of organometallic precursors for Ta_4HfC_5 and TaHfC_2 ultra-fine powders through a facile one-pot reaction
(162989)Synthesis and ceramisation of organometallic precursors for Ta_4HfC_5 and TaHfC_2 ultra-fine powders through a facile one-pot reaction
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NSTL
Elsevier
Ultra-fine Ta_4HfC_5 and TaHfC_2 powders were prepared through the pyrolysis of a precursor synthesised by using a facile one-pot reaction. HfCl_4, TaCl_5, and phenolic resins were used as the sources of hafnium (Hf), tantalum (Ta), and carbon (C), respectively. The as-synthesised precursors were further utilised to prepare Ta_4HfC_5- and TaHfC_2-modified carbon/carbon (C/C-Ta_4HfC_5 and C/C-TaHfC_2) composites through precursor infiltration and pyrolysis. The transformation of Ta_4HfC_5 and TaHfC_2 precursors into ultra-fine ceramic powders and anti-ablation performance of the C/C-Ta_4HfC_5 and C/C-TaHfC_2 composites were investigated. The carbothermal reduction of Ta_2O_5 and Hf_6Ta_2O_(17) and the solid solution reaction between HfC and TaC occur successively during the pyrolysis of Ta_4HfC_5 precursors. HfC and TaC undergo a sufficient solid solution reaction at 1800 °C to form the Ta_4HfC_5 solid solution with a particle size of 200-300 nm. The pyrolysis products of TaHfC_2 precursors acquired at 1400-1600 °C are composed of TaC, HfC and TaHfC_2. High-temperature pyrolysis promotes the solid solution reaction between TaC and HfC. The TaHfC_2 solid solution with a particle size of 100-150 nm is formed at 1800 °C. The introduction of TaHfC_2 and Ta_4HfC_5 solid solutions into the C/C composite substantially enhances their anti-ablation performance. The linear ablation rates of C/C-Ta_4HfC_5 and C/C-TaHfC_2 are 11.04 and 16.97 um/s, respectively, which are considerably lower than that of the C/C composite. The good anti-ablation performance of the C/C-Ta_4HfC_5 and C/C-TaHfC_2 composites can be attributed to the formation of the Ta_2O_5 and Hf_6Ta_2O_(17).
NSTL
Elsevier
