Sone Yoshitsugu

A TiO2-supported Ru–Ni alloy (Ru–Ni/TiO2) catalyst (atomic ratio of Ru:Ni = 50:50) for the CO2 methanation reaction was prepared by the polygonal barrel-sputtering method. Sputtering was performed with an area ratio of the Ru and Ni targets of 1:1, Ar gas pressure of 0.8 Pa, and AC power of the radiofrequency power supply of 100 W without heating. As a result, the Ru–Ni alloy nanoparticles were highly dispersed on the TiO2 particles used as the support. The particle sizes were distributed between 1 and 5 nm (average size: 2.5 nm), which is similar to the size distribution of a Ru/TiO2 sample prepared by the same method in our previous study. However, the CO2 methanation performance of Ru–Ni/TiO2 is not as high as that of the above-mentioned Ru/TiO2 sample. This might be because of the lower catalytic activity of Ni than Ru.

The lithium-ion secondary cells/batteries are commonly used for the spacecraft, today. 'REIMEI' satellite is also an example using lithium-ion secondary battery. It used 3 Ah-class off-the-shelf lithium-ion secondary cells, which used the spinel LiMnO4 for the positive and graphite for the negative electrode. Seven cells were connected in series, and two series strings were connected in parallel. The satellite was launched in August, 2005, and injected into the low earth polar orbit. Initially, the battery performance was simulated based on the dependency of the cell performance on temperature. Considering the impedance and discharge performance depending on temperature, the end-of-discharge-voltage during the operation had been precisely controlled. Seven years operation of the lithium-ion secondary battery under the micro-gravity conditions have been demonstrated through the REIMEI operation in space.