TitlePreparation of High Purity Niobium by Electron Beam Melting and
Author(s)Yong Hwan Kim
Publication/PublisherProc. Conf. Electron Beam Melting and Refining,
State of the Art 1994, Barkish Materials Corp. NJ, USA, (1994) pp. 141-155.
AbstractPhysical properties of niobium are deteriorated by interstitial
impurities such as oxygen and nitrogen. The removal of these gaseous impurities
were studied by electron beam (EB) melting and solid state external gettering
with Ti, Y and Zr. The buttons and ingots were repeatedly remelted and refined
by EB furnace (max.140kW). Subsequently, the external gettering for oxygen and
nitrogen was carried out by wrapping samples with active metal foils and
annealing in evacuated quartz ampoules over 1273K. The purity of refined niobium
was characterized by its hardness, specific resistivity, internal friction and
residual resistivity ratio (RRR=r273/r4.2). The results of these measurements
were compared with conventional gas analysis. Niobium was purified to the RRR of
100 through EB melting and 700 through external gettering.