No abstract

A new intermetallic compound, MnGa2Sb2, has been synthesized by direct reaction from Mn and GaSb at 6 GPa and 500°C for 30 min using a belt-type high pressure apparatus. The compound crystallizes into an orthorhombic structure with the space group Iba2 (No. 45). The structure was refined by the Rietveld analysis of the powder X-ray diffraction data and the lattice constant was determined to be a = 1.180(7) nm, b = 0.5968(2) nm, c = 0.5858(2) nm. The structure consists of -Mn-MnMn-linear chains parallel to the c-axis. The compound exhibits metallic conductivity and itinerant-electron ferromagnetic behavior with the Curie temperature of 310 K.

Abstract:The polymer electrolyte fuel cell (PEFC) is an attractive power generation method from the perspective of environmental protection. Carbon is usually used as a catalyst support in PEFC, but it is oxidized under high electrical potential conditions. Ti 4 O 7 is expected as a new catalyst support because of its high electrical conductivity and chemical resistivity. Though Ti 4 O 7 as a catalyst support must have a high specific surface area for a high performance, it is difficult to synthesize nanostructured Ti 4 O 7 . In this research, Ti 4 O 7 nanoparticles with a size of about 60 nm were synthesized by carbothermal reduction of TiO 2 nanoparticles with polyvinylpyrrolidone (carbon source) using 2.45 GHz microwave irradiation. The experiment condition was at 950 • C for 30 min and the samples synthesized by conventional heating showed a grain growth. The findings of this study suggest that microwave processing can drastically reduce the total processing time for the synthesis of nanostructured Ti 4 O 7 .

Ecodesigns for nano-sized noble metal particles were investigated by a new liquid-solid (metal oxide-alcohol) system. We have reduced noble metal oxides as low-emission starting materials by ultrasound and tried to fabricate various noble metal nanoparticles (Ag, Au, Pt, Pd) at room temperature, Noble metal oxides were investigated during decomposition. These reductions are ecologically clean, because many noble metal oxides are not toxic, and during decomposition, O 2 is evolved. By choosing suitable conditions, it is reasonable to expect that this simple sonochemical process can be extended to obtain nano-sized metal particles.

The structure and magnetic properties of FeAl 2 O 4 synthesized by microwave magnetic field (H-field) irradiation were investigated to reveal the effect of the H-field on the crystal structure and the magnetic characteristics of an antiferromagnetic material. The role of the H-field was investigated using a singlemode cavity, which can spatially separate the maximum points of the alternating electric field (E-field) and H-field in the cavity. In H-field irradiation, the crystallite diameter decreased compared to that in conventional heating. In conventional heating, the crystallite diameter did not change with increasing quenching speed. Thus, it is suggested that a decrease in crystallite diameter occurs during H-field irradiation. Furthermore, magnetization after H-field irradiation was greater than that after conventional heating. It is considered that magnetic clusters appear when Fe 3+ partially replaces Al 3+ in the octahedral sites in the grain boundaries, which were formed as a result of decreasing crystallite diameter.