Influence of ion irradiation effects on the hydriding behavior of nanocrystalline Mg-Ni films

Mg-Ni films were grown on a silicon substrate using two magnetron sputter deposition sources and simultaneous Ar ion irradiation. X-ray diffraction microstructure and phase composition, EDX elemental composition and atomic force microscopy surface topography analysis showed that under low-energy Ar ion irradiation (bias voltages from 0 to -120 V), the Mg₂Ni phase was dominant and on the contrary with the increase of ion energy (bias voltages from -120 to -200 V), the MgNi₂ phase appeared. The Mg content changed from 63 at% down to 42 at% in films grown under bias voltages of 0 and -200 V, respectively. During hydrogenation at 8 bar, 270 °C for 3 h, films with a dominant phase of Mg₂Ni were transformed into Mg₂NiH₄. Hydrogen in MgNi₂ films was mainly in interstitials and tended to form bubbles.