Yoshinori Tsushio

Hydrogen desorption properties of the quaternary alloy system Mg2−XM1XNi1−YM2Y

Abstract The effect of substitutions for Mg and Ni in the Mg 2 Ni alloy on hydrogenation properties was studied. In the case of substitution for Mg only, the desorption equilibrium pressure remained constant while the unit cell volume changed. But in the quaternary alloy system obtained from Mg 2 Ni by simultaneous substitutions for Mg and Ni, the cell volume correlated with the hydrogen pressure. This is because hydrogen has a tendency to enter interstitial sites in the quaternary Mg 2 Ni based alloys, the same behavior as found in the case of AB 5 . Therefore, the hydrogenation properties of Mg 2 Ni will be improved by tailoring the effect of cell volume using suitable substitution elements.

Energy distribution of hydrogen sites for MgNi0.86M10.03 (M1=Cr, Fe, Co, Mn) alloys desorbing hydrogen at low temperature

The energy distribution of hydrogen sites for MgNi0.86M10.03 (M1=Cr, Fe, Co, Mn) alloys prepared by the ball milling technique was investigated. From the results of DSC, TG analysis and the calculation of the enthalpy of hydrogenation, we derived that the Cr and Fe-substituted alloys have a broad energy distribution and the averaged enthalpy of hydrogenation is about −82 kJ mol−1 H2−1. Because of the broad distribution, the hydride of larger enthalpy decomposes at low temperature. However, the Co and Mn-substituted alloys have sharp energy distributions though the averaged value of hydrogenation is about −67 kJ mol−1 H2−1. Therefore, these alloys do not desorb hydrogen at low temperature. In order to develop Mg-based alloys that desorb hydrogen at low temperature, the dependence of substitution element on the energy distribution should be considered and substitution elements that make the energy distribution broad must be selected.

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.

Lowering Combustion Temperature of Carbon Particles on Pt-supported Ceria Series Oxides

ディーゼル車の排出ガスに含まれるカーボン微粒子を低減する手段として触媒担持ウォールフロー型ハニカムがあり，これにたい積したカーボン微粒子を効率良く酸化除去するために，Pt担持酸化物の検討を行った。その結果，カーボン微粒子の燃焼開始温度は同等だったが，燃焼開始後については，Pt担持Ce複合酸化物（Pt/Ce0.7Zr0.3O2およびPt/Ce0.9Pr0.1O2）を用いた場合にPt担持CeO2（Pt/CeO2）に比べ，より低温でカーボン微粒子が燃焼した。1073 K大気エージング後では，特にPt/Ce0.9Pr0.1O2において最も低温でカーボン微粒子が燃焼した。Pt/Ce0.9Pr0.1O2については，低温において担体からのO2の放出量が最も多く，またPt表面において吸着するCOの気相O2による酸化反応が進みやすい状態にあることが明らかになり，これらの特性がカーボン微粒子の燃焼特性を高めたと推定した。

Hydrogenation properties of Mg1−xM1xCu2 (M1=La and Nd) with larger interstitial sites than MgCu2

Abstract The hydrogenation properties of C15 compounds are controlled by crystal structure, the size of the interstitial hole being an especially important factor. Its effect on the hydrogenation properties of MgCu 2 substituted with rare earth elements of various radii is discussed and the limit in controlling the crystal structure by conventional substitution is explained.

Mazda’s LNT

The new shape ceria-based support material for a lean Nitrogen oxide (NOx) trap catalyst (LNT) was developed by Mazda. It has a unique shape that each fine particle of raw material is formed into hollow sphere. Samples of platinum loaded powder catalysts were obtained with either the hollow sphere ceria-based material or two kinds of the conventional shape one and their catalytic activities were evaluated with the synthetic gas. The characterisation results indicate that the hollow sphere ceria-based material had high thermal stability [1].

Mazda-LNT. Katalytische Eigenschaften des neu geformten Traegermaterials

Die Reduktion von NOx wird am effizientesten durch die Reduzierung der NOx-Emissionen waehrend der fetten Betriebsphase gefoerdert. Einer der Schluesselfaktoren ist das Beguenstigen dieser Reaktion zur Erhoehung der thermischen Bestaendigkeit des Traegermaterials, auf welchem die Edelmetalle und NOx-Speichermaterialien aufgebracht sind. Mazda hat dazu ein neu geformtes Traegermaterial auf Ceroxid-Basis fuer einen Stickoxid-Speicherkatalysator entwickelt und seine katalytischen Eigenschaften untersucht. Es besitzt eine einzigartige Form, durch die jeder feine Partikel des Ausgangsstoffes zu einer Hohlkugel geformt wird. Drei Proben platinbeladener Pulverkatalysatoren auf Ceroxid-Basis wurden vorbereitet: eine mit dem neuen Hohlkugelmaterial und zwei Proben mit herkoemmlicher Form. Ihre katalytischen Eigenschaften wurden dann mit synthetischem Gas ausgewertet. Die Analyseergebnisse zeigten, dass das Hohlkugelmaterial auf Ceroxid-Basis eine hohe thermische Bestaendigkeit aufweist. Die Katalysatorleistung wurde an einem Pt-Katalysator untersucht.

Hydrogenation Properties of Mg-Co and Its Related Alloys

Novel Mg-Co binary alloys with BCC (body-centered cubic) structure have been successfully synthesized by means of mechanical alloying technique. The formation of BCC structure was confirmed by X-ray diffraction and transmission electron microscopy. Mg-Co alloys were found in the range of Co concentration between 37 and 80 atomic %. All the Mg-Co alloys synthesized absorbed hydrogen below 373K. The maximum hydrogen capacity of these alloys reaches 2.7 mass %. However, desorption of hydrogen at 373 K has not been observed yet. Mg- Co-X (X = B and Ni) ternary alloys with BCC structure have also been synthesized. The lattice parameter of both alloys is lower than that of Mg-Co binary alloys, meanwhile the maximum hydrogen content of both alloys also decreased.