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.

Keywords

hydrogen / magnesiothermic reduction / zirconium / powder

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