Nanocrystalline HfB₂ powders were successfully synthesized by molten salt synthesis technique at 1373 K using B and HfO₂ as precursors within KCl/NaCl molten salts. The results showed that the as-synthesized powders exhibited an irregular polyhedral morphology with the average particle size of 155 nm and possessed a single-crystalline structure. From a fundamental aspect, we demonstrated the molten-salt assisted formation mechanism that the molten salts could accelerate the diffusion rate of the reactants and improve the chemical reaction rate of the reactants in the system to induce the synthesis of the high-purity nanocrystalline powders. Thermogravimetric analysis showed that the oxidation of the as-synthesized HfB₂ powders at 773–1073 K in air was the weight gain process and the corresponding oxidation behavior followed parabolic kinetics governed by the diffusion of oxygen in the oxide layer.

中文翻译：

---

纳米晶HfB 2粉末的熔盐合成，形成机理和氧化行为

以硼和HfO ₂为前驱体，在KCl / NaCl熔盐中，通过熔融盐合成技术，在1373 K下成功合成了纳米晶HfB ₂粉末。结果表明，所合成的粉末表现出不规则的多面体形态，平均粒径为155nm，并且具有单晶结构。从一个基本的方面，我们证明了熔融盐辅助的形成机理，即熔融盐可以加速反应物的扩散速度，并提高反应物在系统中的化学反应速度，从而诱导高纯度纳米晶体粉末的合成。热重分析表明，合成后的HfB ₂的氧化 粉末在空气中在773–1073 K处是增重过程，相应的氧化行为遵循抛物线动力学，受氧在氧化物层中的扩散控制。