Hydrogenation of MgNi<SUB>2</SUB> by Atomic Hydrogen at Elevated Temperatures

Abstract

Hydrogenation of MgNi 2 by atomic hydrogen was examined at elevated temperatures. Mg 2 Ni powder was compacted into a disk and heated in vacuum at 773 K for outgassing. During this heat treatment, Mg 2 Ni was transformed into MgNi 2 by evaporation of Mg. This specimen was hydrogenated at 573, 673 and 773 K by hydrogen gas of 30 Pa and atoms produced by rf-discharge. No significant hydrogenation took place by hydrogen gas. On the other hand, the specimen was hydrogenated by the exposure to atoms at 773 K up to [H]/[M] = 0.14 within 25 ks. New peaks appeared in the diffraction pattern of Cu Kα X-rays at 2θ = 34.0, 42.0, 48.9 and 86.6 • . This observation indicated that the hydride formed was in a cubic structure.

Diagnostics of low-pressure hydrogen discharge created in a 13.56 MHz RF plasma reactor

“…The measurement of the reflection coefficient and its dependence with experimental parameters is a recurrent issue in many plasma applications, ranging from microelectronics to fusion, as evidenced by the high number of papers dealing with this subject over decades (Wood and Wise 1962, Cartry et al 2000, Rousseau et al 2001, Lopaev and Smirnov 2004, Macko et al 2004, Kurunczi et al 2005, Bousquet et al 2007, Guerra 2007, Mozetic and Cvelbar 2007, Rutigliano and Cacciatore 2011, Jacq et al 2013, Samuell and Corr 2014, Sode et al 2014, Marinov et al 2014a. Finally, hydrogen plasma characterization is of interest not only because of the atomic surface loss issue, but because hydrogen gas is often used for plasma processing such as hydrogenation (Hatano and Watanabe 2002), the treatment of Si wafers for creating subsurface defects in layers (Ghica et al 2010), chemical vapor deposition of diamonds (Hassouni et al 1996), functional materials or polycrystallization of amorphous Si, and the creation of positive Fonash 1993, Cielaszyk et al 1995) or negative ions in ionsources (Iordanova et al 2011, Kalache et al 2004, Ahmad et al 2013.…”

Improved Hydrogen Storage Properties and Air Stability of Metal Hydrides by Constructing Heterophase Composites

“…It is generally assumed that the MgNi 2 is difficult to hydrogenate. , The hydrogenation reaction requires a temperature over 700 °C and a hydrogen pressure over 2 GPa, which cannot be reached in this experiment. Isothermal hydrogen adsorption and desorption of MgNi 2 in Figure S16 also proved this point.…”