金属の酸化還元反応を利用したジルコニア式酸素ポンプ/センサの校正

Abstract

In order to suppress an oxidation of materials during various high temperature processes such as casting, annealing, and sintering, reducing gas atmosphere of H2 and CO is often employed. However, these gases cannot always be used in practical industrial manufacturing because they are dangerous substance. The utilization of zirconia oxygen pump based on the Nernst principle is one of the most promising methods to reduce the oxygen partial pressure of atmospheric gas safely. Oxygen can migrate through the YSZ wall as ions when applying the voltage between the high temperature walls in this facility. Conversely, it can be used as oxygen sensor when the electromotive force between the walls is measured. However the oxygen partial pressure of the processed gas is expected to show temperature dependence due to the dissociation equilibrium of H2O because the oxygen pump cannot remove hydrogen. A small amount of hydrogen and moisture usually exist even in a high purity gas as impurities. In this study, the temperature dependence of Po2 of gas processed by the oxygen pump was experimentally confirmed by the oxidation-reduction of metals such as nickel and iron. The temperature dependence of Po2 corresponded well to that evaluated by standard Gibbs energy for the formation of H2O.