Microstructure and hydrogen storage properties of as-cast and rapidly solidified Ti-rich Ti-V alloys
(1. Department of Materials Science and Engineering, Norwegian University of Science and Technology,
NO-7491, Trondheim, Norway;
2. Institute for Energy Technology, P.O. Box 40, NO-2027, Kjeller, Norway;
3. Statoil Research Centre, Rotvoll, N-7005, Trondheim, Norway;
4. University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa)
NO-7491, Trondheim, Norway;
2. Institute for Energy Technology, P.O. Box 40, NO-2027, Kjeller, Norway;
3. Statoil Research Centre, Rotvoll, N-7005, Trondheim, Norway;
4. University of the Western Cape, Private Bag X17, Bellville, 7535, South Africa)
Abstract: The goal of the present work was to optimize the phase-structural composition and microstructure of binary Ti0.8-0.9V0.2-0.1 alloys with respect to their hydrogen sorption properties. Application of these alloys is for hydrogen absorption from gaseous mixtures containing substantial amounts of carbon monoxide (CO) at high temperatures. Irrespective of alloy composition, both α(HCP) and β(BCC) phases in Ti0.8-0.9V0.2-0.1 formed single phase FCC hydrides upon hydrogenation in pure H2. An in situ synchrotron X-ray diffraction study showed that only the β-phase transformed to the corresponding hydride when the alloy was hydrogenated in a mixture of H2+10%CO. Rapid solidification (RS) of the alloy resulted in refined grain sizes both in the Ti0.8V0.2 and Ti0.9V0.1 alloys. Furthermore, RS was found to increase the β-phase fraction in Ti0.9V0.1, being twice larger than that of the as-cast alloy. Ti0.9V0.1 had a platelike microstructure as observed by scanning electron microscopy (SEM), the plates were about 300 nm thick. The microstructure refinement resulted in a faster kinetics of H desorption as observed by temperature desorption spectroscopy (TDS).
Key words: hydrogen storage; Ti-V alloys; rapid solidification; synchrotron X-ray diffraction; carbon monoxide