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In this study, surface damaged W monoblocks (melting and cracking) by a pulsed plasma gun and an e-beam devices were exposed to cyclic heat loads (simulating normal heat loads and slow transients) and pulsed heat loads (simulating ELMs) to observe the effects of surface damage on surface erosion and heat removal capability. Heat load tests simulating the normal heat load (10 MW/m2, 10 sec, 300 cycles) and the slow transient (~20 MW/m2, 10 sec, 300 cycles) were performed by the e-beam. The surface morphology changes after the heat load tests were observed using laser scanning microscopy and FE-SEM. After e-beam irradiation of ~20 MW/m2, the longitudinal cracks crossing over entire monoblocks appeared on the surfaces of all monoblocks. Recrystallization and additional crack formation were also observed on the surface. However, there was no significant change of heat removal capability. In the additional pulsed heat load test, the energy fluence of 0.042-0.30MJ/m2was applied with pulse numbers of 103and 104.The surface morphology changes after laser irradiation were observed using laser scanning microscope. After laser irradiation, the grain ejection occurred above a certain energy fluence (~25 % of melting threshold).

Lightweight metallic foams are an attractive material having excellent energy absorption and acoustic damping. The density of magnesium is the smallest among structural metallic materials, and is about two third of the density of aluminum. It is, however, difficult to produce magnesium foams by conventional process because of their chemical activity. This paper provides a novel manufacturing process of magnesium foams. Accumulative diffusion-bonding process can produce a magnesium matrix composite (preform) containing titanium hydride (TiH2) particles as a blowing agent. Foaming tests of three magnesium alloys, AZ31, AZ91 and ZA146, revealed that low solidus temperature is effective to produce fine cell morphology. Chemical composition is significantly important to optimize the cell morphology of magnesium foams.

Using commercial AZ31 magnesium alloy sheets, we produced a foamable preform sheet containing titanium hydride (TiH2) powder through diffusion-bonding and hot-rolling of four cycles. Heating the preform sheets in Ar atmosphere, we obtained closed-cell magnesium alloy foams with various porosities. The foamed specimen at 883 K showed the maximum porosities of 77%.

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We observed the significant improvement of the figure of merit (FOM) of the longitudinal magneto-optical Kerr effect in Au/Co/Au multilayered nano rectangular patch array, in which local-mode surface plasmons were resonantly excited by the light irradiation. To demonstrate the advantage of the plasmon excitation, we compared the FOMs in both Au/Co/Au and bare Co nanostructure. Our results clearly show that the incorporation of plasmonic Au structure to magnetic Co layer is effective not only to increase rotation angle in the longitudinal magneto-optical Kerr effect but also to improve the FOM through the highly reflectance of Au.

A high-repetition nanosecond pulsed glow discharge plasma at a gas pressure of 1 kPa was generated using a SiC-MOSFET inverter power supply for diamond-like carbon (DLC) film preparation. At a high repetition frequency above 50 kHz, the period of the nanosecond voltage pulse became shorter than the decay time of the afterglow plasma, and many ions and radicals remained in the gap space. The deposition rate was 0.1 um/min, which was 5 times higher than that of a conventional plasma CVD process. An increase in hardness to 13 GPa and a decrease in hydrogen content in the DLC film were confirmed by increasing the repetition frequency to 200 kHz.

A new technology for obtaining nanostructure on silicon surface for potential applications to optical devices is represented. Scanning electron microscope analysis indicated a grown nanostructure of dense forest consisting of long cylindrical needle cones with a length of approximately 300 nm and a mutual distance of approximately 200 nm. Raman spectroscopy and spectrophotometry showed a good crystallinity and photon trapping, and reduced light reflectance after helium plasma exposure. The present technique consists of a simple maskless process that circumvents the use of chemical etching liquid, and utilizes soft ion bombardment on silicon substrate, keeping a good crystallinity.

The inactivation of Bacillus atrophaeusspores by a dielectric barrier discharge (DBD) plasma in atmospheric humid air was investigated in order to develop a low-temperature, low-cost, and high-speed plasma sterilization technique. The biological indicators covered with a Tyvek sheet were set just outside the DBD plasma region, where air temperature and humidity as a discharge gas were precisely controlled by an environmental test chamber. The results show that the inactivation of B. atrophaeusspores was found to be dependent strongly on humidity, and was completed within 15 min at a relative humidity of 90% and a temperature of 30 °C. The treatment time for sterilization is shorter than those of conventional sterilization methods using ethylene oxide gas and dry heat treatment. The inactivation rates depend on not only relative humidity but also temperature, so that water content in air could determine the generation of reactive species such as hydroxyl radicals that are effective for the inactivation of B. atrophaeusspores.