Kinetics of hydrogen absorption by titanium, tantalum, tungsten, iron and palladium films with and without oxygen preabsorption at 300 K

Abstract

The hydrogen absorption rates of titanium, tantalum, tungsten, iron and palladium films 15–20 nm thick were measured at room temperature and hydrogen pressures between 10 −9 and 10 −4 mbar using the volumetric method. Films with clean surfaces absorb gas amounts in the concentration ranges corresponding to hydride formation for titanium and tantalum and equivalent to about one monolayer of hydrogen for tungsten, iron and palladium with reaction probabilities in the range 1–10 −4. The reaction rates are strongly reduced if the film surface is coated with oxygen at thicknesses equivalent to several monolayers. Iron and palladium films precoated with oxygen show an H 2O partial pressure peak which indicates that the oxygen sorption layer is reduced by the formation of H 2O during exposure to hydrogen.