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Journal Articles

Detecting halfmetallic electronic structures of spintronic materials in a magnetic field

Fujiwara, Hidenori*; Umetsu, Rie*; Kuroda, Fumiaki*; Miyawaki, Jun*; Kashiuchi, Toshiyuki*; Nishimoto, Kohei*; Nagai, Kodai*; Sekiyama, Akira*; Irizawa, Akinori*; Takeda, Yukiharu; et al.

Scientific Reports (Internet), 11(1), p.18654_1 - 18654_9, 2021/09

 Times Cited Count:0

Journal Articles

Effect of water for the oxygen adsorption on surface of PtCo catalysts

Cui, Y.-T.*; Harada, Yoshihisa*; Niwa, Hideharu*; Oshima, Masaharu*; Hatanaka, Tatsuya*; Nakamura, Naoki*; Ando, Masaki*; Yoshida, Toshihiko*; Ishii, Kenji*; Matsumura, Daiju

NanotechJapan Bulletin (Internet), 11(4), 6 Pages, 2018/08

no abstracts in English

Journal Articles

Electronic structure and magnetic properties of the half-metallic ferrimagnet Mn$$_{2}$$VAl probed by soft X-ray spectroscopies

Nagai, Kodai*; Fujiwara, Hidenori*; Aratani, Hidekazu*; Fujioka, Shuhei*; Yomosa, Hiroshi*; Nakatani, Yasuhiro*; Kiss, Takayuki*; Sekiyama, Akira*; Kuroda, Fumiaki*; Fujii, Hitoshi*; et al.

Physical Review B, 97(3), p.035143_1 - 035143_8, 2018/01

AA2017-0644.pdf:1.01MB

 Times Cited Count:13 Percentile:63.24(Materials Science, Multidisciplinary)

We have studied the electronic structure of ferrimagnetic Mn$$_{2}$$VAl single crystals by means of soft X-ray absorption spectroscopy (XAS), X-ray absorption magnetic circular dichroism (XMCD), and resonant soft X-ray inelastic scattering (RIXS). We have successfully observed the XMCD signals for all the constituent elements. The Mn L$$_{2,3}$$ XAS and XMCD spectra are reproduced by spectral simulations based on density-functional theory, indicating the itinerant character of the Mn 3$$d$$ states. On the other hand, the V 3$$d$$ electrons are rather localized since the ionic model can qualitatively explain the V L$$_{2,3}$$ XAS and XMCD spectra. This picture is consistent with local $$dd$$ excitations revealed by the V L$$_{3}$$ RIXS.

Journal Articles

Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex, 2; Neutron scattering instruments

Nakajima, Kenji; Kawakita, Yukinobu; Ito, Shinichi*; Abe, Jun*; Aizawa, Kazuya; Aoki, Hiroyuki; Endo, Hitoshi*; Fujita, Masaki*; Funakoshi, Kenichi*; Gong, W.*; et al.

Quantum Beam Science (Internet), 1(3), p.9_1 - 9_59, 2017/12

The neutron instruments suite, installed at the spallation neutron source of the Materials and Life Science Experimental Facility (MLF) at the Japan Proton Accelerator Research Complex (J-PARC), is reviewed. MLF has 23 neutron beam ports and 21 instruments are in operation for user programs or are under commissioning. A unique and challenging instrumental suite in MLF has been realized via combination of a high-performance neutron source, optimized for neutron scattering, and unique instruments using cutting-edge technologies. All instruments are/will serve in world-leading investigations in a broad range of fields, from fundamental physics to industrial applications. In this review, overviews, characteristic features, and typical applications of the individual instruments are mentioned.

Journal Articles

Observation of momentum-dependent charge excitations in hole-doped cuprates using resonant inelastic X-ray scattering at the oxygen $$K$$ edge

Ishii, Kenji*; Toyama, Takami*; Asano, Shun*; Sato, Kentaro*; Fujita, Masaki*; Wakimoto, Shuichi; Tsutsui, Kenji*; Sota, Shigetoshi*; Miyawaki, Jun*; Niwa, Hideharu*; et al.

Physical Review B, 96(11), p.115148_1 - 115148_8, 2017/09

AA2017-0402.pdf:0.81MB

 Times Cited Count:20 Percentile:75.96(Materials Science, Multidisciplinary)

Journal Articles

Wetting induced oxidation of Pt-based nano catalysts revealed by ${{it in situ}}$ high energy resolution X-ray absorption spectroscopy

Cui, Y.-T.*; Harada, Yoshihisa*; Niwa, Hideharu*; Hatanaka, Tatsuya*; Nakamura, Naoki*; Ando, Masaki*; Yoshida, Toshihiko*; Ishii, Kenji*; Matsumura, Daiju; Oji, Hiroshi*; et al.

Scientific Reports (Internet), 7(1), p.1482_1 - 1482_8, 2017/05

 Times Cited Count:11 Percentile:43.66(Multidisciplinary Sciences)

Journal Articles

Electronic structure of Pt and Pt-Co nanoparticles with O$$_{2}$$ and O$$_{2}$$/H$$_{2}$$O adsorption revealed by in situ XAFS and hard X-ray photoelectron spectroscopy

Cui, Y.*; Harada, Yoshihisa*; Hatanaka, Tatsuya*; Nakamura, Naoki*; Ando, Masaki*; Yoshida, Toshihiko*; Ikenaga, Eiji*; Ishii, Kenji*; Matsumura, Daiju; Li, R.*; et al.

ECS Transactions, 72(8), p.131 - 136, 2016/10

 Times Cited Count:1 Percentile:54.63

Journal Articles

Resonant inelastic X-ray scattering study of entangled spin-orbital excitations in superconducting PrFeAsO$$_{0.7}$$

Nomura, Takuji*; Harada, Yoshihisa*; Niwa, Hideharu*; Ishii, Kenji*; Ishikado, Motoyuki*; Shamoto, Shinichi; Jarrige, I.*

Physical Review B, 94(3), p.035134_1 - 035134_9, 2016/07

 Times Cited Count:9 Percentile:49.94(Materials Science, Multidisciplinary)

Low-energy electron excitation spectra were measured on a single crystal of a typical iron-based superconductor PrFeAsO$$_{0.7}$$ using resonant inelastic X-ray scattering (RIXS) at the Fe-$$L_{3}$$ edge.

Journal Articles

Precise determination of precipitation yield of uranyl nitrate with $$N$$-alkylated 2-pyrrolidone derivatives

Takao, Koichiro*; Kawata, Yoshihisa*; Nogami, Masanobu*; Harada, Masayuki*; Morita, Yasuji; Nishimura, Kenji*; Ikeda, Yasuhisa*

Journal of Nuclear Science and Technology, 52(2), p.294 - 298, 2015/02

 Times Cited Count:2 Percentile:22.25(Nuclear Science & Technology)

Yields of precipitated UO$$_{2}$$(NO$$_{3}$$)$$_{2}$$(NRP)$$_{2}$$ (NRP = $$N$$-alkylated 2-pyrrolidone) were precisely determined by considering reduction of the solution volume through the precipitation, which can be estimated from difference in acid concentrations of the liquid phases before and after the precipitation. The studied NRPs were $$N$$-$$n$$-butyl (NBP) and $$N$$-$$n$$-propyl (NProP) derivatives. In both systems, the precipitation yields precisely determined were always higher than those simply calculated from the ratio of uranium concentrations before and after the precipitation. However, the differences between them are in the range of 0.6% - 2.6%. If such a difference is practically negligible, the volume reduction through the precipitation does not have to be taken into account for simplicity of the analytical manipulation.

Journal Articles

Spin and orbital magnetic moments of Fe in the $$n$$-type ferromagnetic semiconductor (In,Fe)As

Kobayashi, Masaki*; Anh, L. D.*; Hai, P. N.*; Takeda, Yukiharu; Sakamoto, Shoya*; Kadono, Toshiharu*; Okane, Tetsuo; Saito, Yuji; Yamagami, Hiroshi; Harada, Yoshihisa*; et al.

Applied Physics Letters, 105(3), p.032403_1 - 032403_4, 2014/07

AA2015-0418.pdf:0.82MB

 Times Cited Count:1 Percentile:5.16(Physics, Applied)

Journal Articles

Unveiling the impurity band induced ferromagnetism in the magnetic semiconductor (Ga,Mn)As

Kobayashi, Masaki*; Muneta, Iriya*; Takeda, Yukiharu; Harada, Yoshihisa*; Fujimori, Atsushi*; Krempask$'y$, J.*; Schmitt, T.*; Oya, Shinobu*; Tanaka, Masaaki*; Oshima, Masaharu*; et al.

Physical Review B, 89(20), p.205204_1 - 205204_8, 2014/05

 Times Cited Count:65 Percentile:93.14(Materials Science, Multidisciplinary)

Journal Articles

Stability of polyvinylpolypyrrolidone against $$gamma$$-ray irradiation in HNO$$_{3}$$ media

Nogami, Masanobu*; Sugiyama, Yuichi*; Kawasaki, Takeshi*; Harada, Masayuki*; Kawata, Yoshihisa*; Morita, Yasuji; Kikuchi, Toshiaki*; Ikeda, Yasuhisa*

Journal of Radioanalytical and Nuclear Chemistry, 296(1), p.423 - 427, 2013/04

 Times Cited Count:5 Percentile:43.78(Chemistry, Analytical)

Stability of polyvinylpolypyrrolidone (PVPP), a resin with adsorption selectivity to U(VI) in nitric acid media, against $$gamma$$-ray irradiation has been examined using HNO$$_{3}$$ solutions of various concentrations. As the result, no clear decrease in the capacity was observed for any samples. Or rather, it was found that the capacity increased by approximately 50% for the PVPP slurry irradiated in 6 M HNO$$_{3}$$. The infrared spectroscopic study indicates that PVPP degrades by $$gamma$$-ray irradiation in HNO$$_{3}$$ from the cleavage of the pyrrolidone ring by the addition of oxygen atom originating from HNO$$_{3}$$, followed by the formation of chain monoamides with multiple coordinative atoms by the continuous addition of oxygen, finally leading to the generation of primary-amine type anion exchange resin. It is also indicated that all generated functional groups possess adsorptivity to U(VI) in 3 M HNO$$_{3}$$.

Journal Articles

Probing carbon edge exposure of iron phthalocyanine-based oxygen reduction catalysts by soft X-ray absorption spectroscopy

Niwa, Hideharu*; Saito, Makoto*; Kobayashi, Masaki*; Harada, Yoshihisa*; Oshima, Masaharu*; Moriya, Shogo*; Matsubayashi, Katsuyuki*; Nabae, Yuta*; Kuroki, Shigeki*; Ikeda, Takashi; et al.

Journal of Power Sources, 223, p.30 - 35, 2013/02

 Times Cited Count:17 Percentile:54.86(Chemistry, Physical)

To design non-platinum, inexpensive, but high performance carbon-based cathode catalysts for polymer electrolyte fuel cells, it is important to elucidate the active site for oxygen reduction reaction (ORR). However, it is difficult to directly identify the active site by applying conventional structural or electronic probes to such complex systems. Here, we used C 1${it s}$ X-ray absorption spectroscopy (XAS) to observe electronic structure of carbon in iron phthalocyanine-based catalysts, and found a signature of edge exposure below the $$pi^{ast}$$ edge, whose intensity is well correlated with the ORR activity. These results demonstrate that C 1${it s}$ XAS can be used to characterize the ORR activity of carbon-based cathode catalysts in terms of the edge exposure.

Journal Articles

Study on the oxygen adsorption property of nitrogen-containing metal-free carbon-based cathode catalysts for oxygen reduction reaction

Kiuchi, Hisao*; Niwa, Hideharu*; Kobayashi, Masaki*; Harada, Yoshihisa*; Oshima, Masaharu*; Chokai, Masayuki*; Nabae, Yuta*; Kuroki, Shigeki*; Kakimoto, Masaaki*; Ikeda, Takashi; et al.

Electrochimica Acta, 82(1), p.291 - 295, 2012/10

 Times Cited Count:12 Percentile:34.28(Electrochemistry)

We study the characteristics of oxygen adsorption on metal-free carbon-based cathode catalysts derived from nitrogen-containing polyamide (PA) and nitrogen-free phenolic resin (PhRs). Electrochemical analysis and Raman spectroscopy showed higher 2-electron oxygen reduction reaction (ORR) activity and more defect sites in PA than PhRs. The increase in the amount of adsorbed oxygen in PA was also identified by oxygen adsorption isotherms. ${it In-situ}$ X-ray photoelectron spectroscopy reveals that graphite-like nitrogen contributes to oxygen adsorption and C=O components are dominant in PA. These experimental results indicate that the adsorbed C=O components near the graphite-like nitrogen can be assigned as active sites for 2-electron ORR.

Journal Articles

Stability of pyrrolidone derivatives against $$gamma$$-ray irradiation

Nogami, Masanobu*; Sugiyama, Yuichi*; Kawasaki, Takeshi*; Harada, Masayuki*; Kawata, Yoshihisa*; Morita, Yasuji; Kikuchi, Toshiaki*; Ikeda, Yasuhisa*

Science China; Chemistry, 55(9), p.1739 - 1745, 2012/09

 Times Cited Count:4 Percentile:21.58(Chemistry, Multidisciplinary)

Stability of N-alkylated pyrrolidone derivatives (NRPs) against radiation was examined by irradiation tests with $$^{60}$$Co $$gamma$$-ray. We have been developed a novel reprocessing system using NRPs which have precipitation ability to haxa- and tetravalent actinides in nitric acid media. Degradation rates of NRPs are evaluated by irradiation in 3M nitric acid solutions and mechanism of degradation are discussed in the present paper.

Journal Articles

A Beam intensity monitor for the evaluation beamline for soft X-ray optical elements

Imazono, Takashi; Moriya, Naoji*; Harada, Yoshihisa*; Sano, Kazuo*; Koike, Masato

AIP Conference Proceedings 1465, p.38 - 42, 2012/07

 Times Cited Count:0 Percentile:0.13

Journal Articles

Indirect contribution of transition metal towards oxygen reduction reaction activity in iron phthalocyanine-based carbon catalysts for polymer electrolyte fuel cells

Kobayashi, Masaki*; Niwa, Hideharu*; Saito, Makoto*; Harada, Yoshihisa*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Electrochimica Acta, 74, p.254 - 259, 2012/07

 Times Cited Count:48 Percentile:82.87(Electrochemistry)

The electronic structure of the residual metal atoms in FePc-based carbon catalysts, prepared by pyrolyzing a mixture of FePc and phenolic resin polymer at 800$$^{circ}$$C, before and after acid washing have been investigated using XAFS spectroscopy to clarify the role of Fe in the ORR activity. The decomposition analyses for the XAFS spectra reveal that the composition ratio of each Fe component is unaltered by the acid washing, indicating that the residual Fe components were removed by the acid washing irrespective of their chemical states. Because the oxygen reduction potential was approximately unchanged by the acid washing, the residual Fe itself does not seem to contribute directly to the ORR activity. The residual Fe can act as a catalyst to accelerate the growth of the sp$$^{2}$$ carbon network during pyrolysis. The results imply that light elements are components of the ORR active sites in the FePc-based carbon catalysts.

Journal Articles

Development of advanced reprocessing system based on precipitation method using pyrrolidone derivatives as precipitants; Overall evaluation of system

Ikeda, Yasuhisa*; Kawasaki, Takeshi*; Harada, Masayuki*; Nogami, Masanobu*; Kawata, Yoshihisa*; Kim, S.-Y.*; Morita, Yasuji; Chikazawa, Takahiro*; Someya, Hiroshi*; Kikuchi, Toshiaki*

Proceedings of International Conference on Toward and Over the Fukushima Daiichi Accident (GLOBAL 2011) (CD-ROM), 5 Pages, 2011/12

An advanced reprocessing system for spent FBR fuels based on two precipitation processes using pyrrolidone derivatives as precipitants has been developed. Experimental results of precipitation behavior of U, Pu and other elements, the heat- and radiation-resistance of precipitants, the thermal decomposition properties of precipitates showed that N-n-butyl-2-pyrrolidone and N-neopentyl-2-pyrrolidone are the appropriate precipitants for the first and second precipitation steps, respectively. From the engineering investigation, We confirmed that the precipitation and the filtration can be done efficiently using the engineering scale equipment and that the fuel pellets are directly prepared by the calcination of the precipitates. On the basis of these results, we evaluated that the proposed system is expected to be one of candidates of the future reprocessing systems for spent FBR fuels.

Journal Articles

Role of residual transition-metal atoms in oxygen reduction reaction in cobalt phthalocyanine-based carbon cathode catalysts for polymer electrolyte fuel cell

Kobayashi, Masaki*; Niwa, Hideharu*; Harada, Yoshihisa*; Horiba, Koji*; Oshima, Masaharu*; Ofuchi, Hironori*; Terakura, Kiyoyuki*; Ikeda, Takashi; Koshigoe, Yuka*; Ozaki, Junichi*; et al.

Journal of Power Sources, 196(20), p.8346 - 8351, 2011/10

 Times Cited Count:32 Percentile:70.76(Chemistry, Physical)

The electronic structure of Co atoms in CoPc-based carbon catalysts, which were prepared by pyrolyzing a mixture of CoPc and phenol resin polymer up to 1000$$^circ$$C, has been investigated using XAFS analysis and HXPES. The Co K XAFS spectra show that most of the Co atoms are in the metallic state and small quantities of oxidized Co components are present in the samples even after acid washing to remove Co atoms. Based on the difference in probing depth between XAFS and HXPES, it was found that after acid washing, the surface region with the aggregated Co clusters is primarily composed of metallic Co. Since the electrochemical properties remain almost unchanged even after the acid washing process, the residual metallic and oxidized Co atoms themselves will hardly contribute to the ORR activity of the CoPc-based carbon cathode catalysts, implying that the active sites of the CoPc-based catalysts primarily consist of light elements such as C and N.

Journal Articles

Precipitation ability to U(IV) and stability of 1,3-dimethyl-2-imidazolidone for selective precipitation of U(VI) in nitric acid media

Nogami, Masanobu*; Harada, Masayuki*; Sugiyama, Yuichi*; Kawasaki, Takeshi*; Kawata, Yoshihisa*; Morita, Yasuji; Kikuchi, Toshiaki*; Ikeda, Yasuhisa*

Progress in Nuclear Energy, 53(7), p.948 - 951, 2011/09

 Times Cited Count:3 Percentile:28.8(Nuclear Science & Technology)

The precipitation ability of 1,3-dimethyl-2-imidazolidone (DMI) to U(VI) and U(IV) was examined using nitric acid solutions. While DMI precipitated U(VI) from 3 M nitric acid, no precipitate was observed in the solution containing 0.15 M U(IV) and 3 M nitric acid by adding DMI at the ratio of [DMI]/[U(IV)]=5. This indicates that the selectivity of DMI to U(VI) than U(IV). In spite of the excellent selectivity to U(VI), DMI has a disadvantage on the stability in nitric acid, because gradual acid hydrolysis of DMI is inevitable due to the nature of the chemical structure. Experiments on the stability of DMI in $$gamma$$-ray irradiation and heating in nitric acid solutions showed that the stability is strongly affected by the concentration of nitric acid and that DMI may be applicable in nitric acid solutions up to ca. 2 M.

45 (Records 1-20 displayed on this page)