Proton Irradiation and Hydrogen Diffusion in Quasicrystals

Abstract

Ti-Zr-Ni quasicrystals are new candidates for hydrogen storage applications due to their capability of loading a large amount of hydrogen at reasonable temperature and hydrogen pressure. The technical applications, however, have been limited because of the presence of a thick oxygen layer, which must be eliminated prior to introducing hydrogen into a sample. To effectively remove the oxygen barrier and to enhance the capability of hydrogen absorption, we irradiated Ti39.5Zr39.5Ni21 quasicrystal ingots by using a proton beam at energy of 20 MeV, 15 mA for 30 minutes. The proton-beam-treated samples were exposed to a hydrogen pressure of 650 psi at 200 degrees C and the results were analyzed by monitoring the pressure change of the chamber. The main concerns were a careful measurement of the weight gain after hydrogenation and an estimate of the peak shifts in X-ray diffraction. An absorption of hydrogen was observed for the proton-beam-irradiated samples while little hydrogen loading was noticed for unirradiated ones. Our results demonstrate that proton irradiation may be used as a new technique that can effectively eliminate the oxygen barrier and enhance the rates of hydrogen diffusion. However, more systematic investigations regarding the role of the proton are required before applying the technique for practical applications.