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Journal Articles

Oxygen reduction activity and interfacial structures of La$$_{0.8}$$Sr$$_{0.2}$$CoO$$_{3}$$ at initial electrochemical process in an alkaline solution

Matsuzaki, Akira*; Hirayama, Masaaki*; Oguchi, Shoya*; Komo, Mamoru*; Ikezawa, Atsunori*; Suzuki, Kota*; Tamura, Kazuhisa; Arai, Hajime*; Kanno, Ryoji*

Electrochemistry (Internet), 90(10), p.107001_1 - 107001_8, 2022/10

 Times Cited Count:0 Percentile:0.01(Electrochemistry)

Oxygen reduction and evolution reactions (ORR and OER) of perovskite-type La$$_{0.8}$$Sr$$_{0.2}$$CoO$$_{3}$$ were characterized using two-dimensional model electrodes with different reaction planes. Synthesized by pulsed laser deposition, these thin and flat electrodes can reveal the reaction plane dependence of the ORR activity. From steady-state polarization measurements in KOH (aq.), the ORR activity was the highest on the (001) film during the first ORR/OER cycle, and it decreased significantly during the second cycle. In-situ synchrotron X-ray diffraction clarified crystal structure changes in the bulk and surface regions of La$$_{0.8}$$Sr$$_{0.2}$$CoO$$_{3}$$, and these changes are associated with forming oxygen defects during the initial electrochemical process. Furthermore, the La$$_{0.8}$$Sr$$_{0.2}$$CoO$$_{3}$$ surface partially decomposed upon reacting. Therefore, the interfacial structures formed in the electrochemical reaction field is important for enhancing ORR and OER activities.

Journal Articles

Thermally altered subsurface material of asteroid (162173) Ryugu

Kitazato, Kohei*; Milliken, R. E.*; Iwata, Takahiro*; Abe, Masanao*; Otake, Makiko*; Matsuura, Shuji*; Takagi, Yasuhiko*; Nakamura, Tomoki*; Hiroi, Takahiro*; Matsuoka, Moe*; et al.

Nature Astronomy (Internet), 5(3), p.246 - 250, 2021/03

 Times Cited Count:30 Percentile:96.87(Astronomy & Astrophysics)

Here we report observations of Ryugu's subsurface material by the Near-Infrared Spectrometer (NIRS3) on the Hayabusa2 spacecraft. Reflectance spectra of excavated material exhibit a hydroxyl (OH) absorption feature that is slightly stronger and peak-shifted compared with that observed for the surface, indicating that space weathering and/or radiative heating have caused subtle spectral changes in the uppermost surface. However, the strength and shape of the OH feature still suggests that the subsurface material experienced heating above 300 $$^{circ}$$C, similar to the surface. In contrast, thermophysical modeling indicates that radiative heating does not increase the temperature above 200 $$^{circ}$$C at the estimated excavation depth of 1 m, even if the semimajor axis is reduced to 0.344 au. This supports the hypothesis that primary thermal alteration occurred due to radiogenic and/or impact heating on Ryugu's parent body.

Journal Articles

Conductance of a long rectangular channel; Pressure dependence

Ogiwara, Norio; Hikichi, Yusuke*; Kamiya, Junichiro; Kinsho, Michikazu; Yoshida, Hajime*; Arai, Kenta*

Journal of the Vacuum Society of Japan, 60(12), p.475 - 480, 2017/12

Journal Articles

Lithium intercalation and structural changes at the LiCoO$$_{2}$$ surface under high voltage battery operation

Taminato, So*; Hirayama, Masaaki*; Suzuki, Kota*; Tamura, Kazuhisa; Minato, Taketoshi*; Arai, Hajime*; Uchimoto, Yoshiharu*; Ogumi, Zempachi*; Kanno, Ryoji*

Journal of Power Sources, 307, p.599 - 603, 2016/03

 Times Cited Count:31 Percentile:72.1(Chemistry, Physical)

An epitaxial-film model electrode of LiCoO$$_{2}$$(104) was fabricated on SrRuO$$_{3}$$(100)/Nb:SrTiO$$_{3}$$(100) using pulsed laser deposition. The 50 nm thick LiCoO$$_{2}$$(104) film exhibited lithium (de-)intercalation activity with a first discharge capacity of 119 mAh g$$^{-1}$$ between 3.0 and 4.4 V, followed by a gradual capacity fading with subsequent charge-discharge cycles. In contrast, a 3.2 nm thick Li$$_{3}$$PO$$_{4}$$-coated film exhibited a higher intercalation capacity of 148 mAh g$$^{-1}$$ with superior cycle retention than the uncoated film. In situ surface X-ray diffraction measurements revealed a small lattice change at the coated surface during the (de-)intercalation processes compared to the uncoated surface. The surface modification of LiCoO$$_{2}$$ by the Li$$_{3}$$PO$$_{4}$$ coating could lead to improvement of the structural stability at the surface region during lithium (de-)intercalation at high voltage.

Journal Articles

C-face interface defects in 4H-SiC MOSFETs studied by electrically detected magnetic resonance

Umeda, Takahide*; Okamoto, Mitsuo*; Arai, Ryo*; Sato, Yoshihiro*; Kosugi, Ryoji*; Harada, Shinsuke*; Okumura, Hajime*; Makino, Takahiro; Oshima, Takeshi

Materials Science Forum, 778-780, p.414 - 417, 2014/02

 Times Cited Count:2 Percentile:72.87

Interface defects of Metal-Oxide-Semiconductors (MOSFETs) fabricated on Carbone (C) face 4H-SiC were investigated by Electrically Detected Magnet Resistance (EDMR). Gate oxide of the MOSFETs was formed by either wet-oxidation and H$$_{2}$$ annealing or dry-oxidation. The values of channel mobility for MOSFETS with wet gate oxide and dry gate oxide are less than 1 and 90 cm$$^{2}$$/Vs, respectively. By EDMR measurement under low temperature (less than 20 K), EDMR signals related to C were detected. The peak height of the signals increased with increasing $$gamma$$-ray doses, and the channel mobility decreased. From this result, it is assumed that hydrogen atoms passivating C dangling bonds are released by $$gamma$$-rays and the channel mobility decreases with increasing the C related defects.

Journal Articles

Measurement of expiratory alcohol by QMS gas analyzer

Arai, Takashi; Hiratsuka, Hajime; Hasegawa, Koichi; Hatano, Toshihisa; Nemoto, Masahiro; Abe, Tetsuya

Heisei-18-Nendo Nagoya Daigaku Sogo Gijutsu Kenkyukai Sochi Gijutsu Kenkyukai Hokokushu, p.76 - 79, 2007/03

Recently, the accident because of drunken driving is taken up in the topic of news, and the concern is had at the amount of the drinking and the drinking time etc. of the inside of the body. It is said that there is a correlation in the alcoholic density included in an alcoholic amount and the expiration in blood so far, and is reported on the equipment that measures an alcoholic density of the expiration based on this. We also are executing the breath analysis as an example of applying QMS (four pile polar mass spectrometer) gas analyzer "Gravimas". This time, an alcoholic density in the expiration was measured, the performance of this device to alcoholic detection was examined, and the change at the time of an alcoholic density in the expiration high sensitivity was measured. These results suggest the utility of the breath analysis that uses QMS.

Journal Articles

Development of breath gas and skin excretion gas analysis technology using quadrupole mass spectrometer

Hiratsuka, Hajime; Abe, Tetsuya; Nemoto, Masahiro; Hasegawa, Koichi; Arai, Takashi; Hatano, Toshihisa

Heisei-18-Nendo Kiki, Bunseki Gijutsu Kenkyukai Hokoku, p.163 - 166, 2006/09

JP, H16-234010   Licensable Patent Information Database   Patent publication (In Japanese)

no abstracts in English

Journal Articles

Development of a electrical balance separating from atmosphere

Hasegawa, Koichi; Abe, Tetsuya; Nemoto, Masahiro; Hiratsuka, Hajime; Arai, Takashi; Hatano, Toshihisa

Heisei-18-Nendo Kiki, Bunseki Gijutsu Kenkyukai Hokoku, p.169 - 172, 2006/09

JP, H16-304402   Licensable Patent Information Database   Patent publication (In Japanese)

no abstracts in English

Journal Articles

Development of breath gas analysis technology using quadrupole mass spectrometer

Hiratsuka, Hajime; Arai, Takashi; Hasegawa, Koichi; Nemoto, Masahiro; Abe, Tetsuya

Dai-17-Kai Bunshi Kagaku Kenkyusho Gijutsu Kenkyukai Hokokushu (CD-ROM), 4 Pages, 2006/03

JP, H16-258288   Patent publication (In Japanese)

no abstracts in English

Journal Articles

Hydrogen retention in divertor tiles used in JT-60 for hydrogen discharge period

Hirohata, Yuko*; Shibahara, Takahiro*; Tanabe, Tetsuo*; Arai, Takashi; Goto, Yoshitaka*; Oya, Yasuhisa*; Yoshida, Hajime*; Morimoto, Yasutomi*; Yagyu, Junichi; Masaki, Kei; et al.

Journal of Nuclear Materials, 337-339, p.609 - 613, 2005/03

 Times Cited Count:13 Percentile:65.49(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Relationship between the current direction in the inversion layer and the electrical characteristics of metal-oxide-semiconductor field effect transistors on 3C-SiC

Oshima, Takeshi; Lee, K. K.; Ishida, Yuki*; Kojima, Kazutoshi*; Tanaka, Yasunori*; Takahashi, Tetsuo*; Yoshikawa, Masahito; Okumura, Hajime*; Arai, Kazuo*; Kamiya, Tomihiro

Materials Science Forum, 457-460(Part2), p.1405 - 1408, 2004/06

The electrical characteristics of cubic silicon carbide (3C-SiC) Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) with the current direction in the inversion layer perpendicular to [-110] ([-110]-perpendicular MOSFETs) were compared to those of 3C-SiC MOSFETs with the current direction in the inversion layer parallel to [-110] ([-110]-parallel MOSFETs). The threshold voltage (V$$_{T}$$) for both MOSFETs shows -0.5 V although enhancement type MOSFETs were designed. The values of channel mobility which was estimated from linear region of drain current (I$$_{D}$$) - drain voltage (V$$_{D}$$) curves are 230 cm$$^{2}$$/Vs for [-110]-perpendicular MOSFETs and 215 cm$$^{2}$$/Vs for [-110]-parallel MOSFETs, indicating no significant difference between both MOSFETs. The value of I$$_{D}$$ for [-110]-perpendicular MOSFETs is of order of 10-8 A at V$$_{D}$$ = 10V and gate voltage (V$$_{G}$$) of -2V. However, for [-110]-parallel MOSFETs, I$$_{D}$$ shows of order of -10-6 A at V$$_{D}$$ = 10V and V$$_{G}$$ = -2V.

Journal Articles

The Electrical characteristics of metal-oxide-semiconductor field effect transistors fabricated on cubic silicon carbide

Oshima, Takeshi; Lee, K. K.; Ishida, Yuki*; Kojima, Kazutoshi*; Tanaka, Yasunori*; Takahashi, Tetsuo*; Yoshikawa, Masahito; Okumura, Hajime*; Arai, Kazuo*; Kamiya, Tomihiro

Japanese Journal of Applied Physics, Part 2, 42(6B), p.L625 - L627, 2003/06

 Times Cited Count:39 Percentile:77.47(Physics, Applied)

The n-channel Metal-Oxide-Semiconductor Field Effect Transistors (MOSFETs) were fabricated on cubic silicon carbide (3C-SiC) epitaxial layers grown on 3C-SiC substrates. The gate oxide of the MOSFETs was formed using pyrogenic oxidation at 1100$$^{circ}$$C. The 3C-SiC MOSFETs showed enhancement type behaviors after annealing at 200$$^{circ}$$C for 30 min in argon atmosphere. The maximum value of the effective channel mobility of the 3C-SiC MOSFETs was 260 cm$$^{2}$$/Vs. The leakage current of gate oxide was of a few tens of nA/cm$$^{2}$$ at an electric field range below 8.5 MV/cm, and breakdown began around 8.5 MV/cm.

Journal Articles

Insulation resistance measurement for the toroidal field coils of JT-60

Nishiyama, Tomokazu; Arai, Takashi; Miyo, Yasuhiko; Hiratsuka, Hajime; Honda, Masao; Miya, Naoyuki

Heisei-14-Nendo Tokyo Daigaku Sogo Gijutsu Kenkyukai Gijutsu Hokokushu, p.2_28 - 2_30, 2003/03

no abstracts in English

Journal Articles

Wall conditioning and experience of the carbon-based first wall in JT-60U

Masaki, Kei; Yagyu, Junichi; Arai, Takashi; Kaminaga, Atsushi; Kodama, Kozo; Miya, Naoyuki; Ando, Toshiro; Hiratsuka, Hajime; Saido, Masahiro

Fusion Science and Technology (JT-60 Special Issue), 42(2-3), p.386 - 395, 2002/09

 Times Cited Count:9 Percentile:51.57(Nuclear Science & Technology)

The wall conditioning of JT-60U consists of the 300$$^{circ}$$C baking, He-TDC, He-GDC, tokamak discharge cleaning and boronization. Using these methods, total pressure of the vacuum vessel reached finally 10$$^{-6}$$ $$sim$$ 10$$^{-5}$$ Pa. The oxygen impurity was decreased to $$sim$$0.5%. The experience with the carbon-based first wall showed that taper shaping is effective to reduce the local heat concentration to the tile edges. The observed poloidal asymmetric deposition of carbon on the divertor region implies that the carbon impurity produced in the outer divertor contributes to the deposition on the inner divertor. In 1992 and 1993, the B$$_{4}$$C converted CFC tiles were installed in the outer divertor to reduce chemical sputtering of CFC tiles and oxygen impurity. The reduction was successfully demonstrated with the B$$_{4}$$C converted CFC tiles. In order to understand the tritium behavior in JT-60U, tritium in the first wall and the exhaust gas were measured. The estimated tritium inventory in the first wall was $$sim$$50% of the generated tritium.

Journal Articles

Status and subjects of thermal-hydraulic analysis for next-generation LWRs with passive safety systems

Aritomi, Masanori*; Onuki, Akira; Arai, Kenji*; *; Yonomoto, Taisuke; Araya, Fumimasa; Akimoto, Hajime

Nihon Genshiryoku Gakkai-Shi, 41(7), p.738 - 757, 1999/00

 Times Cited Count:0 Percentile:0.01(Nuclear Science & Technology)

no abstracts in English

Journal Articles

Effects of plasma behavior on in-vessel components in JT-60 operation

Hiratsuka, Hajime; ; ; Arai, Takashi; Masaki, Kei; Neyatani, Yuzuru; Yagyu, Junichi; Kaminaga, Atsushi; Saido, Masahiro

Fusion Technology 1996, 0, 4 Pages, 1996/00

no abstracts in English

Journal Articles

Development and operation of first wall in JT-60U high-power heated discharges

Masaki, Kei; ; Arai, Takashi; Hiratsuka, Hajime; Yagyu, Junichi; Saido, Masahiro; Ogiwara, Norio; Higashijima, Satoru

16th IEEE/NPSS Symp. on Fusion Engineering (SOFE '95), p.638 - 641, 1995/00

no abstracts in English

Journal Articles

Initial boronization of JT-60U tokamak using decaborane

Saido, Masahiro; Ogiwara, Norio; Shimada, Michiya; Arai, Takashi; Hiratsuka, Hajime; ; Shimizu, Masatsugu; Ninomiya, Hiromasa; Nakamura, Hiroo; *; et al.

Japanese Journal of Applied Physics, 32(7), p.3276 - 3281, 1993/07

 Times Cited Count:54 Percentile:90.75(Physics, Applied)

no abstracts in English

Journal Articles

A Boronization system in the JT-60U tokamak; Application of a new method using a less hazardous substance

Saido, Masahiro; Hiratsuka, Hajime; Arai, Takashi; Neyatani, Yuzuru; Shimada, Michiya;

Fusion Engineering and Design, 22, p.271 - 275, 1993/00

 Times Cited Count:31 Percentile:96.57(Nuclear Science & Technology)

no abstracts in English

Journal Articles

JT-60 operation results after its modification for higher plasma current with single null open divertor

; Horiike, Hiroshi; Neyatani, Yuzuru; Matsukawa, Makoto; Ando, Toshiro; Yoshino, Ryuji; Arai, Takashi; Ninomiya, Hiromasa; Yamamoto, Masahiro; ; et al.

Proc. of the 14th Symp. on Fusion Engineering,Vol. 1, p.177 - 180, 1992/00

no abstracts in English

26 (Records 1-20 displayed on this page)