Effect of Ti additive and preparation procedure on the temperature and decomposition kinetics of the MgH2 phase in the synthesized mechanicals alloys

Abstract

The mechanical alloy Mg + 10 wt.% Ti and two mechanical alloys MgH2 + 10 wt.% Ti were synthesized by a reactive mechanical alloying (RMA) method, but in different ways. The influence of doping and the preparation procedure of mechanical alloys (MAs) on thehydrogen sorption properties, temperature and decomposition kinetics of their MgH2 phase was investigated by isobaric thermodesorption spectroscopy at a constant hydrogen pressure of 0.1 MPa. The desorption kinetics of the milled MgH2 + 10 wt.% Ti are faster than in the case of the ball milled Mg + 10 wt.% Ti. It was found that the manner of obtaining a mechanical alloys by reactive milling of MgH2 +10 wt. % Ti powder mixture rather than Mg +10 wt. % Ti powder mixture  to improve the kinetic characteristics. The role of Ti as an alloying element in improving the hydrogen desorption kinetics of МAs obtained by various preparation procedures was studied. The stabilizing effect of Ti on the nanocrystalline structure and growth of the crystallites (grains) of the MgH2 phase during the cycling was also evaluated. It has been established the practical absence of the influence of Ti additive and the manner of obtaining MAs on the its thermodynamic stability.