Hydrogen absorption characteristics and Mössbauer spectroscopic study of Ti0.67Nb0.33−xFex (x = 0.00, 0.13, 0.20) alloys

The present study deals with the preparation and hydrogen absorption studies on Ti0.67Nb0.33−xFex (x = 0.00, 0.13, 0.20) alloys. From X-ray diffraction results it is inferred that the three alloys are bcc phase and get converted to fcc phase upon hydrogenation. Ti0.67Nb0.13Fe0.20 alloy showed maximum hydrogen storage capacity (2.62 wt%) with fastest kinetics among the studied compositions. The hydrogenation kinetics of Ti0.67Nb0.13Fe0.20 alloy was studied in detail over the temperature range from 298 K to 473 K. Two different types of rate equations were required to fit the kinetic data, indicating two different rate determining steps (rds) during the progress of hydriding reaction. The activation energies for the two rate determining steps have been calculated from hydrogen absorption kinetics study at different temperatures. 57Fe Mössbauer spectroscopic study of Fe substituted alloys and their corresponding hydrides show the effect of hydrogenation on the electronic structure of the alloys in terms of electronic charge distribution and volume expansion.