Adsorption-absorption kinetics of the nitrogen + tantalum system

Abstract

The nitrogen sorption behaviour of tantalum has been studied using both constant pressure and constant volume techniques in the pressure and temperature ranges 10^–9–10^–4 toor and 295–1600°K respectively. Chemisorption at room temperature occurs with an initial sticking probability of 0.33 and ceases at a saturation coverage of about 5 × 10¹⁴ atoms cm^–2, which is independent of pressure in the range 5 × 10^–9–3 × 10^–7 torr. There is evidence for the existence of two binding states. Above about 500°K adsorption and absorption occur simultaneously, the energy barrier to gas entry into the metal from the surface being about 38 kcal (g atom)^–1.