ИСТИНА

Magnesium hydride (MgH2) is a material with the high mass percent of the hydrogen (about 7%) and is friendly for environment. Therefore it can be used for save and compact storage of the hydrogen and convenient for needs of hydrogen energy. The main disadvantage of MgH2 for the practical application is a high temperature (more than 2500C) of the hydride decomposition. Now in the literature presents a lot works focusing on improving of kinetic and stability of the magnesium hydride [1, 2]. At this work the samples of partly desorbed MgH2 were studied at low temperature using by neutron diffraction method. The samples were prepared from powder of MgH2 by partial desorption of hydrogen at high temperature (up to 4000C). The X-ray analysis shown, that obtained samples contain a mixture of Mg and MgH2 phases in the different rate. The structure was studied for the MgH2 samples with Mg > MgH2 phases rate. The samples after low-temperature treatment became unstable and decomposed at the room temperature spontaneously. This behaviour may be attributed to ordering and disordering of the hydrogen atoms in the metal matrix of magnesium hydride at different temperatures. The neutron diffraction experiment was performed at low and room temperatures and hydrogen distribution inside of the samples was obtained for both cases. Comparison of the neutron data at both temperatures can give a proposition of the stability decreasing for the quenched samples. Diffusion of disordered hydrogen atoms is easier than ordered in hydride phase. Quenching of the sample may change a point of the equilibrium between coexisting phases and assists a phase transition in the direction to decreasing of the stability quenched samples after heating up to the room temperature.