Metallic niobium powder reduced by atmospheric magnesium gas with niobium pentoxide powder

Abstract

It was tried to find the optimal condition to prepare the metallic niobium powder with minimal oxygen content by atmospheric magnesium-gas reduction of niobium pentoxide (Nb2O5) powder at 10731223 K, which are industrially moderate and low temperature ranges until maximally 80 h inside the chamber held under the argon circumstances of 110 kPa. Magnesium oxide of the by-product of the reduction, was dissolved and removed fully by dissolving in a 10% aqueous hydrochloric acid solution. The particle size of the niobium powder reduced for 20 h was slightly increased within the range of 2003600 nm according to increase of reduction temperatures. And such fine particles were further coarsened to near 1 µm by increase of reduction times until 80 h at 1173 K, which is thought to be the most suitable for magnesium-gas reduction to be applied in industry. The reduction time satisfied for a maximal reduction effect was found to be 60 hours as the oxygen content was then minimally saturated to about 0.42 wt.%. Furthermore, the hydrogen contamination due to acid leaching of 0.28 wt.% was fully removed by dehydrogenation, which was a heat treatment performed under vacuum at 827 K for 2 h; this resulted in the formation of metallic niobium powder.