Sorption of Nitrogen at Low Pressures by Titanium

Abstract

The sorption kinetics of nitrogen at pressures of 1×10−5 to 1×10−3 Torr on titanium foil was studied ill the range 600 °–800 °C, by using an ultrahigh vacuum microbalance. In the similar way to oxygen, the rate law of nitrogen 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. The linear rate law was obeyed for shorter times as the nitrogen pressure and the reaction temperature increased. In the initial linear part, the sorption rate was proportional to the nitrogen pressure at each temperature, which showed the linear sorption to be controlled by the rate of arrival. The sticking probability and pumping speed per unit area (cm2) for nitrogen were constant with change of nitrogen pressure, e.g., at 800 °C, 0.0045 for sticking probability and 0.098 (liter sec−1) for pumping speed. The transtion in the sorption rate laws and critical pressure of nitrogen for the transition are discussed on the basis of a diffusion theory.