Sorption kinetics of oxygen at very low pressures by zirconium

Abstract

The sorption rate of oxygen by zirconium at very low pressures of 4×10 −6 to 4×10 −4 torr has been investigated in the temperature range 500–850°C using a microbalance. The rate law of sorption was separable into two types, i.e., the linear rate law in the initial period and the parabolic rate law in the latter period. In the initial linear sorption, the rate was exactly proportional to the oxygen pressure at each temperature. The data of sorption kinetics of zirconium were rearranged from the viewpoint of vacuum technology, i.e., sticking probability and pumping speed in bulk gettering. The transition in the rate law of sorption is discussed on the bases of Wagner's model which involves simultaneous scale formation and oxygen dissolution into the metal bulk.