Thermal Resistance and the Kinetics of Hydrogen Desorption from Hydrides of the Mg–Al–Ni–Ti Mechanical Alloy

Abstract

With the aim to decrease temperature and improve the kinetics of decomposition of the MgH2 stoichiometric hydride, we study the possibility of its complex alloying with 3 at.% Al + 3 at.% Ni + 7 at.% Ti performed with the help of mechanochemical synthesis. It is shown that, as a result of the addition of Al, Ni, and Ti to magnesium, the thermal resistance of the MgH2 hydride phase of the mechanical alloy obtained by the reactive mechanical alloying decreases and, hence, the temperature of the onset of hydrogen desorption decreases from 320°C (for MgH2 without Al, Ni, and Ti) to 280°C. We do not detect any decrease in the equilibrium temperature of the onset of hydrogen desorption under its constant pressure of 1 bar in a reactor, which may serve as an indication of the loss of thermodynamic stability of MgH2 as a result of mechanical alloying. It is shown that the kinetics of hydrogen desorption of the MgH2 phase of the mechanical alloy is mainly improved by alloying with Ni and Ti, whereas the contribution of Al is negligible.