ИСТИНА

Magnesium hydride (MgH2) contents a high mass percent of hydrogen (about 7%) and may be used as material for storage of hydrogen. But slow kinetic of hydride formation and high temperature of hydrogen removal limit MgH2 for practical use. At present time treatment of the magnesium surface by milling and doping with catalysts allows to improve kinetic of magnesium hydrogenation and discharging [1]. At present work the structure of the partly vacuum extracted samples of MgH2 was studied using by neutron diffraction method. The samples were prepared by vacuum extracted technique at high temperature (up to 4000C) of the MgH2 powder. Extraction of hydrogen was performed partially and obtained samples consist of the mixture of Mg and MgH2 phases in different proportion. The structure was studied for extracted sample and for extracted and quenched at low temperature sample with Mg > MgH2 phases rate. Extracted sample demonstrated a high stability, while extracted and quenched sample became unstable and decomposed after short time. Neutron diffraction experiment allows determining of hydrogen atoms distribution in Mg and MgH2 phases of the both samples. Explanation of different behaviour of the studied samples was proposed. It based on the difference of the shape of equilibrium curve before and after critical point in direction to hydrogen concentration. This equilibrium curve separates a border between disordered and ordered phases in the phase diagram of the metal-hydrogen system. In each part of the curve diffusion of hydrogen atoms is diverse, so this assists to phase transition and leads to decreasing of the stability quenched samples after heating up to room temperature.