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131.
Hidenori Hiramatsu Takayoshi Katase Yoshihiro Ishimaru Akira Tsukamoto Toshio Kamiya Keiichi Tanabe Hideo Hosono 《Materials Science and Engineering: B》2012,177(7):515-519
Relationships between microstructure and transport properties of bicrystal grain boundary (BGB) junctions were studied in cobalt-doped BaFe2As2 (BaFe2As2:Co) epitaxial films grown on [0 0 1]-tilt bicrystal substrates of MgO and (La, Sr)(Al, Ta)O3 with misorientation angles θGB = 3–45°. The θGB of BaFe2As2:Co BGBs were exactly transferred from those of the bicrystal substrates. No segregation of impurities was detected at the BGB junction interfaces, and the chemical compositions of the BGBs were uniform and the same as those in the bulk film regions. A transition from a strongly-coupled GB behavior to a weak-link behavior was observed in current density–voltage characteristics under self-field around θGB ~ 9°. The critical current density decreased from (1.2–1.6) × 106 A/cm2 of the intragrain transport to (0.7–1.1) × 105 A/cm2 of θGB = 45° because supercurrent becomes more governed by Josephson current with increasing θGB. 相似文献
132.
Masami Tsubota Satoshi Hino Hironobu Fujii Chie Oomatsu Masashi Yamana Takayuki Ichikawa Yoshitsugu Kojima 《International Journal of Hydrogen Energy》2010
The possibility of using ammonia as a hydrogen carrier is examined for the reaction between magnesium ammine complex MgCl2(NH3)6 and lithium hydride LiH. Sample was milled at low temperature of −40 °C to avoid decomposition of MgCl2(NH3)6 during the milling. The effects of milling time, milling speed (revolutions per minute), and catalysts on hydrogen storage properties were investigated by thermogravimetry, thermal desorption mass spectroscopy, and X-ray diffraction experiments. Experimental results indicated that a milled composite of Mg(NH3)6Cl2 and catalyzed-LiH desorbed the ∼100% H2 gas even at 125 °C in a closed system. The reverse reaction also proceeded by separately cooling MgCl2 at lower temperature than 100 °C and heating LiNH2 at 300 °C in the closed system. 相似文献
133.
Yuichi Yamasaki Harumi Asami Takashi Isoshima Itaru Kamiya Masahiko Hara 《Science and Technology of Advanced Materials》2013,14(6):519-522
A single chromophore detection using video-microscopy is one of the latest methodologies to reveal unique characteristics, which could not be obtained from ensemble measurements. Among many kinds of subjects, dynamic optical properties observed in colloidal semiconductor nanoparticles are attractive and important not only for the basis of photo-physics but also for application studies, e.g. biological labeling, electronic devices. In this study, fluorescence video-microscopy was performed on cadmium selenide (CdSe) quantum dots (QDs) spin-coated on a glass substrate. From single CdSe QDs detection, emissions at wavelengths separated over 60 nm were observed for the first time. This spectral feature was attributed to the existence of double-emissive relaxation processes in CdSe QDs. Photoluminescence intermittency was also observed both from relaxation processes. Fluorescence video-microscopy, which was advanced in biology, can be applicable for the real-time monitoring of dynamic properties in semiconductor photo-physics. 相似文献
134.
Huaiyu Shao Junko Matsuda Hai-Wen Li Etsuo Akiba Ankur Jain Takayuki Ichikawa Yoshitsugu Kojima 《International Journal of Hydrogen Energy》2013
Ball milled Mg–Co alloys with body-centered cubic structure (BCC) may absorb hydrogen at 258 K with a hydrogen capacity around 3 mass%. The phase and morphology evolution process of Mg50Co50 alloys ball milled for 0.5 h–400 h was studied by X-ray diffraction and scanning electron microscope. The formation mechanism of the Mg50Co50 alloys was clarified. Mg50Co50 alloys ball milled for various durations were found to present different hydrogen storage properties which could result from the phase and morphology difference in these samples. 相似文献
135.
Tessui Nakagawa Takayuki Ichikawa Keiji Shimoda Masami Tsubota Hiroki Miyaoka Shigehito Isobe Tetsuo Honma Shinji Michimura Fumitoshi Iga Somei Ohnuki Yoshitsugu Kojima 《International Journal of Hydrogen Energy》2013
The mixtures of scandium hydride ScH2 and metal boride MBn, which is MgB2 or CaB6, were hydrogenated by mechanical milling under hydrogen pressure at room temperature. ScH2–MgB2 and ScH2–CaB6 desorbed 3.4 and 2.3 mass% of H2, respectively, with peaks below 300 °C. The results of synchrotron radiation X-ray powder diffraction and X-ray absorption spectroscopy at the Sc K-edge indicated that ScB2 was produced by milling. Fourier-transform infrared spectroscopy suggested that hydrogen was stored as B–H bonds in the as-milled samples. Nuclear magnetic resonance spectroscopy clarified the presence of metal borohydrides M(BH4)2 (M = Mg and Ca) in the as-milled ScH2–MBn mixtures. These results indicate that M(BH4)2 is synthesized by milling the ScH2–MBn mixtures under hydrogen pressure at room temperature, and hydrogen was desorbed from M(BH4)2. The by-products of M(BH4)2 are MgH2 in the M = Mg case, which was observed by transmission electron microscopy, and ScB2 in both cases. 相似文献
136.
Toru Kimura Hiroki Miyaoka Takayuki Ichikawa Yoshitsugu Kojima 《International Journal of Hydrogen Energy》2013
Hydrogen absorption of magnesium (Mg) catalyzed by 1 mol% niobium oxide (Nb2O5) was demonstrated under the low temperature condition even at −50 °C. The kinetic and thermodynamic properties were examined for MgH2 with and without Nb2O5. By considering the remarkable absorption features at such low temperature, the essential hydrogen absorption properties were investigated under accurate isothermal conditions. As the results, the activation energy of hydrogen absorption for the catalyzed Mg was evaluated to be 38 kJ/mol, which was significantly smaller than that of MgH2 without the catalyst. The kinetic improvement was also found on the hydrogen desorption process. On the other hand, thermodynamic properties were not changed by the catalyst as a matter of course. Therefore, the Nb2O5 addition mainly affects the reaction rates between Mg and hydrogen and shows the excellent catalytic effects. 相似文献
137.
Kiyoshi Yoshida Kaname Kizu Haruyuki Murakami Koji Kamiya Atsushi Honda Yoshihiro Ohnishi Masato Furukawa Shuji Asakawa Masaya Kuramochi Kenichi Kurihara 《Fusion Engineering and Design》2013,88(9-10):1499-1504
The modifying of the JT-60U magnet system to the superconducting coils is progressing as a satellite facility for ITER by both parties of Japanese government and European commission in the Broader Approach agreement. The magnet system requires current supplies of 25.7 kA for 18 TF coils and of 20 kA for 4 CS modules and 6 EF coils. The magnet system generates an average heat load of 3.2 kW at 4 K to the cryogenic system. The feeder components connected to the power supply provide current supply. The cooling pipes connected to the cryogenic system provide coolant supply. The instrumentation of the JT-60SA magnet system is used for its operation. 相似文献
138.
139.
Takayuki Tokoroyama Makoto Kamiya Noritsugu Umehara Chao Wang Dongfeng Diao 《Lubrication Science》2012,24(3):129-139
The influence of ultraviolet (UV) irradiation on low frictional performance of CNx coatings with 100 nm thickness having nitrogen contents of 9%, 14% and 19% deposited on Si(100) substrate by ion beam mixing was investigated in N2 atmosphere environment. Three UV lights of 254, 312 and 365 nm were used to irradiate the surface of CNx / Si(100) for 60 min. The changes of N / C ratio and atomic binding energy in the coating were analysed using Auger electron spectroscopy and X‐ray photoelectron spectroscopy, respectively. The friction coefficient of Si3N4 ball sliding against CNx was measured by a pin‐on‐disc tribometer, and wear tracks were analysed by the transmission electron microscope image. The results showed that UV irradiation on CNx coating can decrease the critical frictional cycles for low friction coefficient and that the mechanism is due to the formation of graphite‐like structure in the topmost CNx coating. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
140.