The H−Mg (Hydrogen-Magnesium) system

Titanium hydride and hydrogen concentration in acid‐etched commercially pure titanium and titanium alloy implants: a comparative analysis of five implant systems

“…Hydrogen solubility is limited in the hexagonal close packed (hcp) structure of a-Ti. At low concentration, H is accommodated at the octahedral interstitial sites and the balance is accommodated in the tetrahedral sites (San Martin & Manchester 1987). Above 20 ppm however, hydrogen precipitates into TiH (Livanov et al 1965) and the a-phase coexists with a non-stoichiometricdeficient dihydride, the d-TiH 2 À x phase (Dantzer 1983).…”

Recent advances on the thermal destabilization of Mg-based hydrogen storage materials

“…Upon the application of hydrogen pressure to Mg, the hydrogen atoms initially occupy the tetrahedral interstitial sites within its lattice, forming a tetragonal a-phase with a hydrogen concentration of up to 0.4 wt%. 7 At higher pressures, the nucleation of the b-phase is energetically favorable and the a-phase is converted into hexagonal structure b-MgH 2 . During this process, the hexagonal close-packed (hcp) lattice of Mg expands by approximately 30% (Table 2), and this phase further transitions to the metastable g-MgH 2 phase under higher compressive stress (70-80 bar).…”

Effect of Hydrogen on Corrosion and Stress Corrosion Cracking of AZ91 Alloy in Aqueous Solutions

“…With an increase in applied cathodic or anodic potential, the hydrogen generation rate accelerates as a consequence of cathodic polarization or the negative difference effect (NDE) . Thermodynamically, hydride formation is favorable at a potential less than -2.3 V/SHE in aqueous solutions [22,23], and magnesium hydride is widely used as a hydrogen storage material [24][25][26][27]. Thus, it is inevitable that hydrogen produced by corrosion either directly reacts with magnesium to form corrosion product, as detected using time-of-flight secondary ion mass spectroscopy (ToF-SIMS) [28], X-ray photoelectron spectroscopy (XPS) [29], and X-ray diffraction (XRD) [30,31], or diffuses into magnesium and its alloys [32][33][34][35][36].…”