Institute of Materials Structure Science, KEK, Japan
Title: Structural study of advanced hydrogen storage materials by high intensity neutron total diffractometer (NOVA)
Kazutaka IKEDA received his Ph.D. from Tohoku University in 2006. During his Ph.D. and postdoctoral studies at Institute for Materials Research, Tohoku University, he was also a research fellow for young scientists of the Japan Society for the Promotion of Science. After serving as an assistant professor at the same institute, he moved to Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK) as a research associate professor. His current research interests include material design of hydrogen storage materials and structural study by comprehensive use of multi-probes such as high intensity neutrons and synchrotron light.
A high intensity neutron total diffractometer, NOVA, at J-PARC can observe crystalline structure as well as amorphous and liquid structure in a short time, and clarify the structural changes during hydrogen absorption and desorption reactions of the hydrogen storage materials. Aluminum trihydride (AlH3, alane) is one of the potential candidates for hydrogen storage materials because of high gravimetric and volumetric hydrogen densities (10 mass% and 149 kgH2/m3) and a simple hydrogen desorption reaction (AlH3 -> Al + 3/2H2) at 370-470 K. We investigated the structures of AlD3/AlH3 before the hydrogen desorption reaction by high intensity neutron (NOVA)/X-ray diffraction (BL02B2 at SPring-8) measurements. The presence of chi-Al2O3 on the surface may prevent the deuterium/hydrogen desorption reaction of AlD3/AlH3 to Al at room temperature. This is consistent with in-situ microscopic observations combined with thermal and surface analyses that primary AlH3 particles of size 100-1000 nm were covered by an oxide layer of thickness 3-5 nm. Also, the local structures of amorphous phase during the thermal decomposition reaction from LiAl(ND2)4 to Li3AlN2 and AlN accompanying ammonia desorption were investigated by PDF (atomic Pair Distribution Function) analysis. Some of recent results for structural study of promising hydrogen storage materials on NOVA will be presented.