Selective hydrogenation of Ti–Zr–Ni alloys

Abstract

We prepared series of Ti–Zr–Ni samples by melt-spinning and subsequent thermal treatment at 700 °C for 2 h in dynamic 10 −5 mbar vacuum in order to obtain mixture of crystalline C14 Laves and α, β-(Ti, Zr) phases. These samples were exposed to hydrogen gas at 300 °C and 50 bar for 1000 min. The mass% of H was obtained gravimetrically and volumetrically. When approximately 1% of air was present in the Sievert device we found relatively narrow area in Ti–Zr–Ni phase diagram, so-called zero-zone, where hydrogen amounts in crystalline samples varied between 0 and 0.8 mass%. Surprisingly, icosahedral quasicrystalline (i-QC) samples showed no selective hydrogenation and absorbed more than 1.5 mass% H in the interval of compositions, where the i-phase is formed. XPS analysis revealed that the oxide layer thickness is similar after melt-spinning and thermal treatment for both type of samples, i.e. from inside and outside of the zero-zone. However, after hydrogenation the zero-zone samples had 5-times thicker surface oxide layer. In order to find, whether this is correlated to different electronic structure, DOS near E F was examined by 1H NMR. In parallel, thermal desorption of hydrogen was performed in order to reveal, if H-bonding sites are correlated to different hydrogenation behaviour of various samples.