We have studied a novel high-temperature solder for mounting the power semiconductor devices used in the inverters of hybrid and fuel-cell vehicles. The melting point of well-known lead-free solders such as Sn-based alloys is around 220 °C, which is too low to allow their use with high-temperature compound power semiconductor devices such as those based on GaN and SiC. To overcome the brittleness of Bi, we have developed a new Bi-based solder that consists of Bi with CuAlMn particles, the melting point of which is 270 °C. The CuAlMn particles are prepared by a gas-atomizing method, and are then mixed with molten Bi. Mechanical property measurements revealed that the tensile strength of the fabricated solder was almost two times greater than that of pure Bi. Consequently, joint samples were fabricated using metal plates and their reliabilities were determined by subjecting them to a thermal cycling test. After almost 2000 cycles of -40/200 °C test, neither intermetallic compounds nor cracks were observed at the Cu interface of a sample in which the CTE (Coefficient of Thermal Expansion) was matched. On the other hand, brittle Bi₃Ni was observed in the Ni interface sample. In addition, although those joint samples using Sn-Cu solder peeled off during the -40/250 °C test, no degradation was observed for those samples using the developed solders. In conclusion, the developed solder seems to offer the qualities needed for use with high-temperature power semiconductor devices.

In order to investigate the feasibility of using Plasma Assisted Catalysis (PAC) for exhaust aftertreatment of the diesel engine and lean-burn gasoline engine, the application of PAC to NOx reduction by HC (HC-SCR) was studied using a simulated oxidizing exhaust gas. First, the effects of non-thermal plasma were studied, and the effect of the distance between the plasma reactor and the catalyst reactor and the dominating gas composition of NOx reduction were measured. Then, an appropriate catalyst for PAC was developed; the catalyst properties dominating NOx reduction and improvement of the NOx reduction performance by an additional element were investigated. Finally, on the basis of these results, a 3-stage catalyst, the combination of catalysts with different temperature windows for NOx reduction, was developed. The following results were obtained:
(1) NO₂ and CH₃CHO generated by the plasma resulted in significant reduction of NOx on γ -alumina.
(2) γ -alumina with a large amount of solid acid showed high NOx conversion. In addition, indium loading on γ -alumina improved the NOx reduction activity and suppressed the degradation of the activity under steady-state temperature conditions.
(3) A high NOx conversion as well as high HC and CO conversions were achieved by the 3-stage catalyst with PAC under transient temperature conditions, which simulated the actual engine operating conditions.

Phosphorescent organic light-emitting diodes (OLEDs) have the great advantage of highly-efficient emission compared with conventional fluorescent OLEDs. Pt(II) porphyrins are among the most promising saturated red phosphorescent dyes, yet tuning of their properties by making structural modifications has only been attempted on a modest scale, despite the large structural-diversity of synthetic porphyrins. Here we demonstrate enhancement of the external quantum efficiency of red phosphorescent OLEDs by using a novel facially-encumbered and sterically-bulky meso-aryl-substituted Pt(II) porphyrin. This molecule has a spherical shape ("doubly decamethylene-strapped" Pt(II) porphyrin) although conventional Pt(II) porphyrin is flat in shape. We assume that the red phosphorescent emission increases in line with the decrease in the number of non-radiative decay pathways by restricting the rotational freedom of the meso-aryl substituents in the Pt(II) porphyrins. There is a trend whereby the triplet excited-state lifetimes become longer with increasing external quantum efficiencies (QEs) in OLEDs that include Pt(II) porphyrins. This finding suggests that one can obtain higher external QE values in red phosphorescent OLEDs by restricting the rotational freedom of the meso-aryl substituents of the Pt(II) porphyrins, and this concept may serve as a guide to the molecular design of highly-emissive materials.