O.G. Ershova

Influence of Titanium and Iron Additives to Magnesium on Hydrogen-Sorption Properties, Thermal Stability, and Kinetics of Hydrogen Desorption from MgH2 Phase of Mechanical Alloy

We report on studies of the process of cyclic hydriding–dehydriding (eight cycles) of a mechanical alloy synthesized in a ball mill by grinding powder mixture Mg + 10 wt.% TiH2 + 10 wt.% Fe in argon medium. Hydrogen-sorption properties and thermal stability of the mechanical alloy are studied employing thermodesorption spectroscopy at hydrogen pressure of 0.1 MPa. Hydrogen capacity of the mechanical alloy is determined to be 4.9 wt.%, and onset temperature of hydrogen desorption from the alloy under this study equals 220°C. Kinetics of the process of hydrogen desorption from the hydride phases of the mechanical alloy is examined. The present studies have revealed that mechanical treatment of the magnesium powder in Ar medium with both Fe and Ti additives causes a greater effect on improving the kinetics of hydrogen desorption from hydride phase MgH2 of the alloy and decreasing its thermal stability in comparison with that caused by mechanical treatment of the same powder with either Fe or Ti additives in hydrogen medium.

Thermal Stability And H-Desorption Properties Of Mg3Mnni2HX Prepared By Reactive Mechanical Alloying Of Powders Mg, Mn, Ni In H2-Atmosphere

In the present paper, Mg3MnNi2Hx hydride has been synthesized using the reactive mechanical alloying (RMA) process, i.e. employing a simple one-stage technology instead of the complicated four-stage route used in [1] for synthesis of the same hydride (the milling powder of pure Mg, Ni and Mn metals and of Mg2Ni alloy in argon atmosphere followed by their pressing, sintering and hydriding from the gaseous phase). The Mg3MnNi2Hx hydride derived by the RMA method was studied by thermodesorption spectroscopy. Similarly to Mg3MnNi2Hx hydride derived in [1], the hydride obtained in the present paper reveals decreased thermal stability and close hydrogenation capacity (1.35 wt%).

Analysis of the Interrelation of the Thermal Stability of Hydrides of the Intermetallic Compounds of Composition AB2 with the Nature of Their Chemical Bonds Character Me–H

Charge state of Zr atoms in ZrV2 intermetallic compound and its hydride ZrV2H4 has been studied using the X-ray absorption spectroscopy (XAS) method. Thermal stability of the hydride has been investigated employing the thermodesorption spectroscopy (TDS) method. It has been established the positive charge on Zr ions in ZrV2H4 hydride (i.e., the “transfer” of electronic charge from Zr atoms during formation of the hydride), and this fact indicates the presence of ionic component of metal-hydrogen bonds in the hydride. The conclusion about the existence of correlation between observed increasing thermal stability of ZrV2H4 hydride and ionic component of its metal-hydrogen bonds has been made.

Thermal Stability And Hydrogen Sorption Properties Of The Mgh2 Hydride Derived By The Reactive Milling Of The Mg + 10 Wt% Ti Mixture

Thermal stability and hydrogen sorption properties of the MgH2 phase derived by the reactive milling of the Mg + 10 wt% Ti mixture was studied by the thermodesorption spectroscopy method during the first five cycles of hydrogen sorption-desorption. The addition of Ti decreases decomposition temperature of MgH2by 115 K, if we conclude about decomposition temperature taking into account peaks of speed of a hydrogen release on the desorption spectra derived during the first cycle of heating-cooling in hydrogen atmosphere of the Mg + 10 wt% Ti mechanical alloy. During the second cycle of dehydriding-hydriding, the decomposition temperature of the MgH2 phase of the Mg + 10 wt% Ti composite decreases additionally by 35 K, and the temperature does not change for three following sorption-desorption cycles. It has been established the influence of the method of synthesis of the hydride phase MgH2upon location sites of hydrogen in the phase, and, consequently, upon its decomposition temperature. The addition of titanium to magnesium increases the effect of the above influence and promotes increasing the process of dispersion of magnesium and the MgH2 hydride synthesized due to the reactive milling. Additionally, the addition of titanium promotes decreasing the quantity of oxygen-containing structures, catalytic poisons preventing dissociative hydrogen chemosorption, adsorbed on the surface of MgH2 particles.