Hydrogen is the first element in the periodic table; it is the smallest element with only one electron. When hydrogen shares its electron with other elements, various functions and properties of materials emerge and a hydrogen bond is established, which influences the formation and function of biological materials. Neutrons enable us to accurately observe the hydrogen nucleus and are a powerful tool for conducting research on the functions and properties of hydrogen. Our group is expanding from its basic research on the state of hydrogen in matter to research on improving the characteristics of hydrogen storage materials in collaboration with other universities and research institutions.
Hydrogen storage materials, which are indispensable if we are to realize a hydrogen energy-oriented society, must enable the safe storage and easy extraction of hydrogen. Observing and understanding the state of hydrogen in material will lead to the production of high-performance hydrogen storage materials. Our main goal is to use the characteristics of neutrons to help us understand the mechanism of hydrogen absorption and release in hydrogen storage materials. Metals such as vanadium and titanium can store and release hydrogen, so hydrogen storage alloys are made of a combination of these elements. An absorbed hydrogen atom is pushed into a gap (absorption site) between the atoms that compose the hydrogen storage alloy. It then moves from one absorption site to another, with a diffusion constant similar to that of water molecules. Repeated hydrogen absorption and desorption disturbs the atomic arrangement of the alloy, which degrades the absorption-and-release property. In storage materials composed of much lighter elements, the crystal structure may change into an amorphous structure. To clarify the relationship of the storage material’s structure with the absorption-and-desorption property, it is essential to understand the disturbed structure by focusing on the position of hydrogen. Our research group is studying how hydrogen absorption and desorption occurs in hydrogen storage materials by using regular crystal structural analysis and also by incorporating methods of structural analysis used for glass and liquids.
We developed and built the High-Intensity Total Diffractometer (NOVA) to observe the position of hydrogen in matter. Not only can it be used to observe the position of hydrogen in crystal materials, it can also be used to observe the atomic arrangement in the amorphous phase and the liquid phase. NOVA can also be used to observe various structural changes that occur during hydrogen absorption and release processes. We are developing other devices and analytic methods to observe the positions of hydrogen atoms.
|OTOMO, Toshiya||Professor||Neutron scattering and disordered structure analysis|
|IKEDA, Kazutaka||Assoc. Professor||Synthesis of hydrogen storage materials and structure analysis|
|HONDA, Takashi||Assistant Professor|
|KANEKO, Naokatsu||Engineer||Sample environments|
|OHSHITA, Hidetoshi||Engineer||Development of neutron detector system|
|SEYA, Tomohiro||Technical Associate||DAQ electronics of sample environments|
High Intensity Total Diffractometer