Preparing ZrH₂ powder by magnesiothermic reduction in hydrogen

Abstract

High-purity zirconium metal has been of rising significance to the nuclear and energy industry. However, zirconium exhibits a strong chemical affinity to oxygen, which causes high-purity zirconium metal to be difficult to produce cost-effectively. Powder metallurgy for preparing zirconium metal can achieve near net forming of zirconium metal. Zirconium powder can be prepared by deoxidation of zirconium hydride powder. In this study, an efficient process was proposed to prepare high-purity ZrH₂ using magnesium powder as reducing agent in hydrogen atmosphere. A specific investigation was conducted on the effect of hydrogen on the magnesiothermic reduction and deoxidation of ZrO₂. As indicated from the results, the oxygen content of the reduced powder in Ar was over three times that in H₂ atmosphere at 750 °C for 240 min. Moreover, a passive oxide layer, with a thickness of ~2.76 nm in H₂ and of ~8.51 nm in argon, was formed on the edge of the reduced powder. In accordance with thermodynamic calculation, hydrogen was found to be capable of destabilizing Zr-O solution. An ultra-high pure zirconium hydride powder containing <350×10⁻⁶ oxygen and particle size of <100 µm was prepared as assisted by hydrogen.

摘要

锆金属在核工业及能源领域发挥着重要的作用, 但锆氧之间具有很强的亲和力, 使锆金属难以 经济有效地生产, 粉末冶金方法制备锆金属可以实现锆金属的近净成形制备, 锆粉可通过氢化锆粉脱 氧制备而成。本文提出了一种在氢气辅助下镁还原制备高纯ZrH2粉末的新工艺, 并分析了氢元素的强 化脱氧作用。在750 ℃、240 min 条件下Ar 和H2气氛中镁还原制备的ZrH₂粉末氧含量分别为3.05 wt% 和1.03 wt%。对氢还原后的粉末进行脱氧, 获得平均粒度为89.01 μm、氧含量为0.0047 wt%的氢化锆 粉末。透射电镜测试结果表明, 与氩气气氛还原粉末相比, 氢气条件下的粉末表面钝化层厚度从8.51 nm减小到2.76 nm。热力学计算表明, H元素可以使Zr 金属发生相变, 降低Zr-O 固溶体的稳定性, 提 高镁的脱氧能力。