Hydrogen diffusion in titanium‐hydride observed by the diffraction‐enhanced X‐ray imaging method

Abstract

AbstractThe X‐ray refraction imaging technique was applied to the quantitative study of hydrogen diffusion in titanium‐hydride. Diffusivity and activation energy of hydrogen diffusion were determined by direct observation of the hydride. The hydride was formed on the surface of titanium by electrolytic‐charging at 31, 63 and 98 °C. The specimens were cut into 1 mm thick slices for cross‐sectional observations. The hydride layer was observed using the diffraction‐enhanced X‐ray imaging (DEI) method. Boundaries between titanium and the hydride were observed as thick black or white lines parallel to the specimen surface in the DEI images similar to previously reported results. Hydride distribution caused by hydrogen diffusion from the surface was calculated using an assumed hydrogen diffusivity value and from the solution of the appropriate diffusion equation. The results were converted to the intensity profiles of refraction images of the hydride using the measured rocking curve from an analyzer. The calculated intensity profiles were compared to those obtained from the experimental results and the fitted diffusivity was determined by trial and error. The activation energy of hydrogen in titanium‐hydride thus obtained, 0.55 ± 0.07 eV, showed good agreement with the widely accepted value obtained by the internal friction. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)