Influence of Exposure to Air and Mechanical Dispersion upon Thermal Stability and Decomposition Temperature of β-MgH2 Phase, a Component of Composites Derived by Different Methods
V.D. Dobrovolsky, O.G. Ershova, O.Y. Khyzhun and Y.M. Solonin
Pages 106-113 (8)
Influence of mechanical dispersion and exposure to air on hydrogen-sorption properties and thermal stability
of β-MgH2 synthesized by two different methods, namely through direct hydriding in gaseous medium and by reactive
mechanical alloying, is studied employing thermodesorption spectroscopy and X-ray photoelectron spectroscopy. It is
established that the temperature of the beginning of desorption of the β-MgH2 phase of the composite synthesized through
direct hydriding in gaseous medium depends upon exposure to air after its synthesis. Exposure of the sample to air for 20
min (for more than 5 h) increases the temperature of decomposition of the β-MgH2 phase from 360 to 375 oC (from 360 to
440 oC). Following dispersion of the composite in the ball mill decreases the decomposition temperature of the hydride
phase from 440 to 340 oC. Exposure of the dispersed composite to air for 5 h and even for several days does not increase
the decomposition temperature of the MgH2 phase. Significant role of the surface state in increase of the decomposition
temperature (and thermal stability) due to exposure to air of MgH2 hydride derived by hydriding of magnesium powder in
gaseous medium is revealed. It is found that dispersion of the hydride in the ball mill reduces the temperature of
decomposition of the MgH2 phase.
Hydrides, thermal stability, thermodesorption spectroscopy, X-ray photoelectron spectroscopy.
Frantsevych Institute for Problems of Materials Science, National Academy of Sciences of Ukraine, 3 Krzhyzhanivsky Street, UA-03142 Kyiv, Ukraine.