Phase control during synthesis of nanocrystalline ultrahigh temperature tantalum‐hafnium diboride powders
Phase control during synthesis of nanocrystalline ultrahigh temperature tantalum‐hafnium diboride powders
复制标题
纳米晶超高温二硼化钽铪粉末合成过程中的相控制
DOI：
10.1111/jace.15783
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发表时间：
2018
影响因子：
3.9
通讯作者：
Cheng, Zhe
中科院分区：
文献类型：
--
作者：
Foroughi, Paniz;Rabiei Baboukani, Amin;Franco Hernandez, Alexander;Wang, Chunlei;Cheng, Zhe
Ta1−xhfxb2材料对各种航空航天应用具有吸引力。本研究采用2种低成本的方法合成了纳米晶ta0.5 hf0.5 b2固溶体及其复合粉体。第一个是基于密切混合的钽-铪-硼氧化物(s)和碳的碳的碳热还原反应（CTR），碳是从TaCl5， HfCl4， B2O3和蔗糖作为前体的水溶液处理中得到的。使用该方法时，由于ta2o5和hfo2彼此的溶解度较低，以及这两种氧化物与碳（以及B2O3）的反应性不同，总是单独形成TaB2（‐富）相和hfb2相。由于硼化物之间的相互扩散缓慢，这些硼化物倾向于保持相分离。然而，铜“催化剂”的加入明显地加速了内部扩散和固溶体的形成。第二种方法是基于碱金属还原反应，将tacl5和hfcl4与硼氢化钠（NaBH4）直接反应。该方法通过避免在CTR - based工艺中观察到的氧化物的形成和相关的单个硼化物的相分离，在更低的温度（例如700°C）下一步产生单相ta0.5 hf0.5 b2固溶体纳米粉末。
Ta1−xHfxB2material is attractive for various aerospace applications. In this study, 2 low‐cost approaches were adopted to synthesize nanocrystalline Ta0.5Hf0.5B2solid solution and related composite powders. The first was based on carbothermal reduction reaction (CTR) of intimately mixed tantalum‐hafnium‐boron oxide(s) and carbon obtained from aqueous solution processing of TaCl5, HfCl4, B2O3, and sucrose as precursors. It was found that when using this method, due to the low solubility of each other for Ta2O5and HfO2and the difference in reactivity of those 2 oxides with carbon (as well as B2O3), individual TaB2(‐rich) and HfB2phases always form separately. Those borides tend to remain phase separated due to the slow inter‐diffusion between them. However, it was observed that addition of copper “catalyst” noticeably accelerates the inter‐diffusion and the solid solution formation. The second approach was based on alkali metal reduction reaction, in which TaCl5and HfCl4are directly reacted with sodium borohydride (NaBH4). This method yields a single phase Ta0.5Hf0.5B2solid solution nanopowders in one step at much lower temperatures (e.g., 700°C) by avoiding the oxides formation and the associated phase separation of individual borides as observed in the CTR‐based process.
影响因子：
5.2
作者：
Zhe Cheng;Paniz Foroughi;A. Behrens
通讯作者：
Zhe Cheng;Paniz Foroughi;A. Behrens
影响因子：
2.7
作者：
BATES, SE;BUHRO, WE;KELTON, KF
通讯作者：
KELTON, KF