Shinichi Tanioka

Influence of elemental diffusion on low temperature formation of MgH2 in TiMn1.3T0.2Mg (T = 3d-transition elements)

Abstract In order to examine the influence of the elemental diffusion from the host compound into the Mg region on low temperature formation of MgH 2 , we have investigated the hydriding properties and the microstructures of the composite materials TiMn 1.3 T 0.2 Mg (T = V, Cr, Mn, Fe, Co, Ni and Cu). MgH 2 is formed at 353 K in all composite materials. Of all the substitutions, the amount of MgH 2 is the largest in the case of the Cu substitution, which originates from the existence of the MgMg 2 Cu eutectic formed by Cu diffusion from the host compound TiMn 1.3 Cu 0.2 into the Mg region during the liquid phase sintering. In addition, the hydrogen capacity of TiMn 1.3 Cu 0.2 Mg (that is TiMn 1.3 Cu 0.1 (Mg+Mg 2 Cu) after the sintering) easily saturates in comparison with TiMn 1.5 (Mg+Mg 2 Cu) without Cu diffusion. It is concluded that Cu diffusion promotes the mobility of hydrogen atoms at the complex interface between the host compound and the Mg region.

FORMATION MECHANISM OF MGH2 AT LOW TEMPERATURES IN TI0.6ZR0.4MN0.8CRCU0.2-(MG+MG2CU)

Abstract We have investigated the hydriding properties and the microstructures of the composite materials Ti 0.6 Zr 0.4 Mn 0.8 CrCu 0.2 -(Mg + Mg 2 Cu) produced by liquid-phase sintering. The hydrogen capacities of the composite materials are larger than that of the host compound (Ti Mn-based compound), indicating that MgH 2 is formed at 353 K. The amount of MgH 2 is proportional to that of the Mg Mg 2 Cu eutectic phases in the composite material. Observations of the microstructure for the etched composite materials using scanning electron microscopy reveal that MgH 2 is formed near the interface between the host compound or Mg 2 Cu and the Mg region. Furthermore, MgH 2 is formed easily in the Mg region far from the host compound. This simply suggests that hydrogen diffuses from the host compound into the Mg region along or through the Mg 2 Cu phase.

Low temperature formation of MgH2 in Ti0.6Zr0.4Mn0.8CrCu0.2/Mg

Abstract We have investigated the hydriding properties and microstructures of the new composite material Ti 0.6 Zr 0.4 Mn 0.8 CrCu 0.2 /Mg which contains elemental Mg as a binder. The hydriding properties of the host compound are improved owing to the Mg reduction effect in the process of heat treatment. In addition, we observed that in the process of heat treatment the Cu in the host compound Ti 0.6 Zr 0.4 Mn 0.8 CrCu 0.2 diffuses into the Mg region and Mg 2 Cu is formed. After hydriding and dehydriding cycles, hydrogen in the host compound diffuses into the Mg region through the Mg 2 Cu phase. Consequently, MgH 2 is formed even at temperatures below 373 K under hydrogen pressures of less than 1 MPa.