The microstructure and chemical composition of iron phosphate conversion coatings were investigated by surface/cross-sectional observation using FE-SEM/STEM and chemical state analysis using XPS. As a result, it was suggested that the conversion reaction progressed while the surface oxide on the base material remained, and the fine particles of coatings components were deposited and agglomerated to cover the material surface. The upper layer of coatings was mainly composed of iron phosphate, while the interface between the coatings and base material was deposited iron oxide. The proportion of iron phosphate and iron oxide was almost equal at the initial stage, and the amount of iron phosphate increased as the coating thickness.

In recently years, hydrogen production by water electrolysis using renewable energy is promoted from a carbon-neutral perspective. However, hydrogen is difficult to store and transport, and low volumetric energy density. Therefore, ammonia obtained by the Haber-Bosch process is attracting much attention as an energy carrier because of its easy liquefaction and handling. Ammonia is toxic, but it can be detected easily if ammonia leaks outside owing to its characteristic smell. Thus, a direct ammonia fuel cells (DAFCs) that use ammonia as fuel is promising candidate as a new power generation system. Generally, Pt is used as anode catalyst for ammonia oxidation reaction in DAFC. But it is desired to develop an alternative catalyst for DAFC anode due to the price escalation of Pt, limitation of Pt reserves and the problems of inactivation caused by N_ads poisoning on Pt. Therefore, Pt-Mo alloy catalyst was prepared by RF-magnetron sputtering and the ammonia oxidation activity was investigated in this study. Pt-Mo alloy catalysts showed higher ammonia oxidation activity than Pt one. Especially, Pt-44.0at％Mo indicated 31.4 mA cm⁻² and it is the highest activity among Pt-Mo alloys. And then, Pt-44.0at％Mo is promising candidate for anode catalyst of DAFC.

Cu fine-particle paste is a promising material to form a low-cost interconnect for flexible electronics devices. It has been reported that Cu particles can be sintered at low temperature (well below the half of the melting point) through two-step heat treatment processes of oxidation and reduction. However, the mechanism of the low temperature sintering is not clear yet. In this study, we investigated the oxidation sintering process of Cu fine particles by thermal gravimetric analysis (TGA) in the temperature range of 200-300℃, X-ray diffraction (XRD), and microstructural observation. It was found from TGA that the oxidation process was initially rate-controlled by surface reaction and then by Cu diffusion at grain boundaries of Cu₂O. Transmission electron microscopy observation revealed the formation of a core (Cu)-shell (Cu₂O) structure during the oxidation process. The adjacent Cu₂O shells were bonded to each other resulting in a cross-linked structure. The subsequent reduction process led to the formation of a porous structure by oxygen removal, but the cross-linked structure was maintained, which would make the low-temperature sintered Cu body as robust as solidified solder and sintered Ag paste.

Friction stir welding (FSW) was performed under the two welding conditions (rotation speed-traveling speed) of 150 rpm-100 mm/min and 200 rpm-400 mm/min using 6 mass％Ni-0.63 mass％C steels. The slightly lower peak welding temperature and significantly higher cooling rate was obtained under the condition of 200 rpm-400 mm/min. Texture analysis for retained austenite and martensite revealed that the parent austenite had simple shear texture, which lead to the formation of {110}<111> texture in transformed martensite. Moreover, material flow behavior as a function of distance from the top surface in the stir zone was analyzed based on textures obtained by EBSD measurement. A concentric material flow, which has smaller radius as the far from the tool shoulder, was formed under the condition of 150 rpm-100 mm/min. On the other hand, a heterogeneous material flow with the center shifted to the retreating side was formed under the condition of 200 rpm-400 mm/min. In addition, a different vertical component of material flow was predicted to occur under each welding conditions.

A large step on the initial magnetization curve has been widely observed in Nd-Fe-B hot-deformed magnets. This behavior has been considered as that the first- and latter-half parts of the initial magnetization curve correspond to the magnetization reversals of multi- and single-domain grains, respectively. In this study, the detailed magnetic domain structure of a Nd-Fe-B hot-deformed magnet has been studied for the initial magnetization and demagnetization processes by using a soft X-ray magnetic circular dichroism (XMCD) microscopy. The observed magnetization reversal behavior for the initial magnetization process is quite different from that previously considered. The multi-domain states move from grains to grains through the gradual displacement of domain wall passing through many grains, and then the massive domain wall displacement takes place. The latter part of domain wall displacement is similar with that found in the demagnetization process near the coercivity. Moreover, we found that there are several strong pinning sites which are identical for both the initial magnetization and the demagnetization processes.