Roey Ben David, M.Sc. Candidate
Titanium hydride (TiH2) is employed in a variety of industrial applications, including hydrogen storage, Ti powders manufacturing with the aid of hydrogenation-dehydrogenation (HDH) process, and as foaming agent in the synthesis of Al and Al alloys foams. Better understanding of the kinetics of hydrogen desorption from titanium hydride powders may help to optimize the above mentioned technological processes.
In the present work temperature programmed desorption – mass spectrometry (TPD-MS) technique was utilized to study the dehydrogenation kinetics of TiH2 powders under isothermal and non-isothermal conditions. The kinetic parameters of the various dehydrogenation steps were evaluated. The morphology of the powder particles was characterized in the scanning electron microscope (SEM). The effects of pre-oxidation treatment on the dehydrogenation kinetics were correlated with the temperature-induced changes of the powder morphology. It was found that above 750˚C, hydrogen desorption from the thermally decomposed as-received powder is kinetically delayed compared to that from the pre-oxidized samples. The SEM observations suggest that this delay stems from faster surface coarsening and particles sintering in the as-received powder compared to the pre-oxidized one. This difference in dehydrogenation kinetics was attributed to the oxide decomposition in the pre-oxidized sample, followed by the formation of solid solution of oxygen in Ti and concomitant slowing down of diffusion processes.