Influence of Trace Impurities on Oxygen Activity for High Purity Nitrogen Gas Processed by Zirconia Oxygen Pump

Abstract

Oxygen activity (a(sub O2)) of high purity nitrogen gas was controlled and monitored by a zirconia oxygen pump and sensors operated at 600 C. It was confirmed that the oxygen pump and sensors can control the a(sub O2) at 600 C precisely. Solid metal samples of copper, nickel and iron were actually oxidized under the processed gas when the indicated value of the a(sub O2) is higher than the equilibrium oxygen activity for formation of the metal oxides. When the indicated value of a(sub O2) is lower than the equilibrium oxygen activity for formation of the oxides, the samples were reduced. The processed gas showed a temperature reliance induced from the gas phase equilibrium between the H2 and H2O gases, which were contained in the source gas as an impurity.