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Journal Articles

Desorption behavior of Cs from clay minerals by thermal heating in a vacuum; Analyses by thermal desorption spectroscopy and synchrotron radiation X-ray photoelectron spectroscopy

Hirao, Norie; Shimoyama, Iwao; Baba, Yuji; Izumi, Toshinori; Okamoto, Yoshihiro; Yaita, Tsuyoshi; Suzuki, Shinichi

Bunseki Kagaku, 65(5), p.259 - 266, 2016/05

 Times Cited Count:4 Percentile:74.56(Chemistry, Analytical)

After the Fukushima nuclear plant accident, radiocesium was strongly fixed to clay minerals in the soil. Some dry methods with heating are being developed to remove radiocesium from the soil. In this work, we propose a new dry method that combines heat treatment in vacuum and molten salts to reduce the processing temperature in dry methods. Vermiculite saturated with non-radioactive Cs was heated in vacuum, and Cs contents in the vermiculite were compared before and after heating using X-ray photoelectron spectroscopy. Approximately 40% of cesium were removed by heating at 800$$^{circ}$$C for three minutes when only vermiculite was heated. Approximately 70% of cesium were removed by heating at 450$$^{circ}$$C for three minutes when vermiculite was heated with NaCl/CaCl$$_{2}$$ mixed salts. Based on these results, this method is expected to reduce temperature and increase efficiency on dry methods for cesium removal from clay minerals.

Journal Articles

B-C-N hybrid synthesis by high-temperature ion implantation

Uddin, M. N.; Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nath, K. G.; Nagano, Masamitsu*

Applied Surface Science, 241(1-2), p.246 - 249, 2005/01

 Times Cited Count:8 Percentile:60.67(Chemistry, Physical)

Recently, much attention has been given on the synthesis and characterization of graphite-like B-C-N hybrid. Since graphite-like B-C-N hybrid may have semiconducting property, this material is interesting for applications to electronic and luminescent devices. In order to synthesize this material, borazine ion plasma was implanted in graphite at room temperature (RT) and 600 $$^{circ}$$C. An ultrahigh vacuum (UHV) chamber with base pressure $$sim$$10$$^{-7}$$ Pa was used for the experiment. The X-ray photoelectron spectroscopy (XPS) study suggested that B atoms in the deposited films are in a wide variety of atomic environment such as BC3, BN3 and B-C-N hybrid. The ratios of these coordinations strongly depend on the temperature during the ion implantation. It was found that the B-C-N hybrid is predominantly synthesized by the implantation at 600 $$^{circ}$$C where the surface [B]/([B]+[C]+[N]) ratio ranges from 0.1 to 0.35. The results imply that it is possible to control the composition of B-C-N hybrid by changing the fluence of the ion plasma and the temperature of graphite during ion implantation.

Journal Articles

Characterization of interface defects related to negative-bias temperature instability in ultrathin plasma-nitrided SiON/Si$$<$$100$$>$$ systems

Fujieda, Shinji*; Miura, Yoshinao*; Saito, Motofumi*; Teraoka, Yuden; Yoshigoe, Akitaka

Microelectronics Reliability, 45(1), p.57 - 64, 2005/01

 Times Cited Count:11 Percentile:46.22(Engineering, Electrical & Electronic)

To characterize the interface defects that are responsible for the negative-bias temperature instability (NBTI) of a thin plasma-nitrided SiON/Si system, we carried out inerface trap density measurements, electron-spin resonance spectroscopy and synchrotron radiation XPS. The NBTI was shown to occur mainly through the dehydrogenation of the interfacial Si dangling bonds (P$$_{b}$$ defects). Although we suggest that non- P$$_{b}$$ defects are also generated by the negative-bias temperature stress, nitrogen dangling bonds do not seem to be included. The plasma-nitridation process was confirmed to generate sub-oxides at the interface and thus increase the interface trap density. Furthermore, it was found that the nitridation induces another type of P$$_{b1}$$ defect than that at pure-SiO$$_{2}$$/Si interfacec. Such an increase and structural change of the interfacial defects are likely the causes of the nitridation-enhanced NBTI.

Journal Articles

Structure of sub-monolayered silicon carbide films

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Nath, K. G.

Applied Surface Science, 237(1-4), p.176 - 180, 2004/10

 Times Cited Count:6 Percentile:64.23(Chemistry, Physical)

no abstracts in English

Journal Articles

Energetic deuterium and helium irradiation effects on chemical structure of CVD diamond

Sasaki, Masayoshi*; Morimoto, Yasutomi*; Kimura, Hiromi*; Takahashi, Koji; Sakamoto, Keishi; Imai, Tsuyoshi; Okuno, Kenji*

Journal of Nuclear Materials, 329-333(Part1), p.899 - 903, 2004/08

A CVD diamond has been the reference material of a torus widow for a rf heating system in a fusion reactor. Since the window is in the circumstance of tritium, helium and radio activated dust, it is important to elucidate the effect of ions on chemical structure of the diamond, existing states of tritium and tritium inventory. Polycrystalline CVD diamond disks($$phi$$=10.0mm, t=0.21mm) used in this study are the same grade as rf windows. After sputtering the surface with 1.0 keV Ar$$^{+}$$ to remove oxygen impurity, the sample was irradiated with deuterium (D$$_{2}$$$$^{+}$$) or helium ions (He$$^{+}$$) at an angle of 0 degrees to the surface normal. The irradiation energies of deuterium and helium are 0.25 keV D$$^{+}$$ and 0.45 keV He$$^{+}$$, respectively. The structural change of the irradiated sample was measured by X-ray Photoelectron Spectroscopy (XPS) technique. The C1s peak shift toward lower binding energy side was observed when deuterium ions irradiated. This result indicates that the diamond changes to amorphous carbon due to formation of C-D bond.

Journal Articles

Energetic deuterium and helium irradiation effects on chemical structure of CVD diamond

Sasaki, Masayoshi*; Morimoto, Yasutomi*; Kimura, Hiromi*; Takahashi, Koji; Sakamoto, Keishi; Imai, Tsuyoshi; Okuno, Kenji*

Journal of Nuclear Materials, 329-333(1), p.899 - 903, 2004/08

 Times Cited Count:4 Percentile:68.1(Materials Science, Multidisciplinary)

no abstracts in English

Journal Articles

Electronic structures of ultra-thin silicon carbides deposited on graphite

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao; Nath, K. G.

Applied Surface Science, 234(1-4), p.246 - 250, 2004/07

 Times Cited Count:8 Percentile:56.91(Chemistry, Physical)

no abstracts in English

Journal Articles

Study of the oxidation for Si nanostructures using synchrotron radiation photoemission spectroscopy

Nath, K. G.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji

Applied Surface Science, 234(1-4), p.234 - 239, 2004/07

 Times Cited Count:6 Percentile:64.23(Chemistry, Physical)

Here we report oxidization properties of Si nanostructures grown on graphite. Si 1s X-ray photoemission spectra using synchrotron radiation are used in order to understand the oxidization pathways. Several Si films, such as 0.4, 2, 5.5 & Aring; were grown on highly oriented pyrolitic graphite (HOPG). In the case of a 0.4 & Aring; Si on HOPG, where different types of Si nanostructures in the form of nanoclusters are present, oxygen reactivity is nearly zero. In contrast, the thick film (5.5 & Aring;), where a bulk-type phase is present, shows a higher degree of reactivity. The results are discussed on the basis of nanostructure geometry, number of constituting Si atoms and cluster size.

Journal Articles

Analyses of hydrogen isotope distributions in the outer target tile used in the W-shaped divertor of JT-60U

Oya, Yasuhisa*; Morimoto, Yasutomi*; Oyaizu, Makoto*; Hirohata, Yuko*; Yagyu, Junichi; Miyo, Yasuhiko; Goto, Yoshitaka*; Sugiyama, Kazuyoshi*; Okuno, Kenji*; Miya, Naoyuki; et al.

Physica Scripta, T108, p.57 - 62, 2004/00

no abstracts in English

Journal Articles

Characterization of B-C-N hybrid prepared by ion implantation

Shimoyama, Iwao; Baba, Yuji; Sekiguchi, Tetsuhiro; Nath, K. G.; Sasaki, Masayoshi*; Okuno, Kenji*

Journal of Vacuum Science and Technology A, 21(6), p.1843 - 1848, 2003/11

 Times Cited Count:6 Percentile:70.17(Materials Science, Coatings & Films)

Ion implantation method is applied to synthesize B-C-N hybrids and their electronic structures are characterized by X-ray photoelectron spectroscopy. A boron nitride film is deposited on a graphite target by borazine plasma implantation. At the interface between the BN film and the graphite, variety of bonding combinations including B-N, B-C, and C-N are observed. This proved that B-C-N hybrids is formed by this method.

Journal Articles

Chemical-state analysis for low-dimensional Si and Ge films on graphite

Nath, K. G.; Shimoyama, Iwao; Sekiguchi, Tetsuhiro; Baba, Yuji

Journal of Applied Physics, 94(7), p.4583 - 4588, 2003/10

 Times Cited Count:15 Percentile:45.62(Physics, Applied)

no abstracts in English

Journal Articles

X-ray photoelectron spectroscopy study on change of chemical state of diamond window by ion implantation

Morimoto, Yasutomi*; Sasaki, Masayoshi*; Kimura, Hiromi*; Sakamoto, Keishi; Imai, Tsuyoshi; Okuno, Kenji*

Fusion Engineering and Design, 66-68, p.651 - 656, 2003/09

 Times Cited Count:3 Percentile:72.62(Nuclear Science & Technology)

no abstracts in English

Journal Articles

XPS study of Pb(II) adsorption on $$gamma$$-Al$$_{2}$$O$$_{3}$$ surface at high pH conditions

Yoshida, Takahiro; Yamaguchi, Tetsuji; Iida, Yoshihisa; Nakayama, Shinichi

Journal of Nuclear Science and Technology, 40(9), p.672 - 678, 2003/09

 Times Cited Count:29 Percentile:12.23(Nuclear Science & Technology)

Pb(II) adsorption on $$gamma$$-Al$$_{2}$$O$$_{3}$$ at high pH condition (11 $$<$$ pH $$<$$ 13) was studied in NaNO$$_{3}$$ solutions. With increasing pH from 11, Pb(II) uptake by $$gamma$$-Al$$_{2}$$O$$_{3}$$ was decreased regardless to sodium concentration (0.1 and 1.0 M). XPS spectra showed binding energy of adsorbed Pb (4f) had no dependence on pH and adsorption density and was higher than that of orthorhombic yellow PbO and Pb(NO$$_{3}$$)$$_{2}$$. Molecular orbital (MO) calculation revealed lowest unoccupied molecular orbital (LUMO) energy of Pb(OH)$$_{3}$$$$^{-}$$ was about 6 eV higher than that of Pb(OH)$$_{2}$$, and suggested chemical reactivity of Pb(OH)$$_{3}$$$$^{-}$$ with deprotonated surface hydroxyl ligand [$$equiv$$AlO$$^{-}$$] was expected to be less than that of Pb(OH)$$_{2}$$. Although Pb(II) is adsorbed on $$gamma$$-Al$$_{2}$$O$$_{3}$$ as inner-sphere surface complex, bonding between Pb(II) and $$gamma$$-Al$$_{2}$$O$$_{3}$$ shows less covalent nature.

Journal Articles

Characterization of air-exposed surface $$beta$$-FeSi$$_{2}$$ fabricated by ion beam sputter deposition method

Saito, Takeru; Yamamoto, Hiroyuki; Yamaguchi, Kenji; Nakanoya, Takamitsu; Hojo, Kiichi; Haraguchi, Masaharu*; Imamura, Motoyasu*; Matsubayashi, Nobuyuki*; Tanaka, Tomoaki*; Shimada, Hiromichi*

Nuclear Instruments and Methods in Physics Research B, 206, p.321 - 325, 2003/05

 Times Cited Count:6 Percentile:55.15(Instruments & Instrumentation)

no abstracts in English

Journal Articles

Analyses of erosion and re-deposition layers on graphite tiles used in the W-shaped divertor region of JT-60U

Goto, Yoshitaka*; Yagyu, Junichi; Masaki, Kei; Kizu, Kaname; Kaminaga, Atsushi; Kodama, Kozo; Arai, Takashi; Tanabe, Tetsuo*; Miya, Naoyuki

Journal of Nuclear Materials, 313-316, p.370 - 376, 2003/03

 Times Cited Count:45 Percentile:5.81

Erosion and re-deposition were studied for graphite tiles from W-shaped divertor region of JT-60U in Jun. 1997 - Oct. 1998 periods in which more than 3000 D-D discharges were made with all-carbon wall with boronizations and inner-private flux pumping. On the outer divertor targets, erosion was dominant: maximum erosion depth of around 20 micrometers was measured, while on the inner targets, re-deposition was dominant: columnar structure layers and laminar/columnar-layered structures of maximum thickness around 60 micrometers were found. Through XPS analysis, compositions of the re-deposition layers at a around mid point on the inner target were 94 - 95 at% C, 3 - 4 at% B, and less than 0.6 at% O, Fe, Cr, and Ni. Boron is mainly bound to Carbon. No continuous deposition layers on the dome top/outer wing, while deposition layers were found on the inner wing. Observed in/out asymmetry is attributable to in/out asymmetry of plasma particle conditions in the divertor region.

Journal Articles

Element-specific and site-specific ion desorption from adsorbed molecules by deep core-level photoexcitation at the $$K$$-edges

Baba, Yuji

Low Temperature Physics, 29(3), p.228 - 242, 2003/03

 Times Cited Count:51 Percentile:47.06(Physics, Applied)

no abstracts in English

Journal Articles

Analysis technology of nuclear fusion materials by XPS

Yagyu, Junichi; Goto, Yoshitaka*; Arai, Takashi; Miya, Naoyuki; Morimoto, Yasutomi*; Okuno, Kenji*; Oya, Yasuhisa*; Hirohata, Yuko*; Tanabe, Tetsuo*

Heisei-15-Nendo Kiki, Bunseki Gijutsu Kenkyukai Hokoku, p.105 - 108, 2003/00

no abstracts in English

Journal Articles

Chemical modification of a poly(ethylene terephthalate) surface by the selective alkylation of acid salts

Li, J.; Maekawa, Yasunari; Yamaki, Tetsuya; Yoshida, Masaru

Macromolecular Chemistry and Physics, 203(17), p.2470 - 2474, 2002/12

 Times Cited Count:12 Percentile:57.01(Polymer Science)

Chemical modification of the hydrophilic surface of poly(ethylene terephthalate) (PET) was examined by the selective alkylation of the acid salt on the surface using acylbromides as an electrophile with catalytic potassium fluoride. The hydrophobicity of the PET surface increased as the alkylation reaction of the hydrolyzed surface proceeded. The chemical incorporation of the alkylation reagents was confirmed by the fluorine peaks in X-ray photoelectron spectroscopy (XPS) from the fluorinated reagents. Exponential increases were observed in the emission and excitation intensities of fluorescence spectra during the reaction of the surface with a fluorescent reagent. This indicated the esterification of carboxylic acids on the surface without deterioration of the reactions even at the later stages. The relation between changes in contact angles and the fluorescence spectra revealed that the hydrophobicity of a surface was quickly restored at the beginning of a reaction.

Journal Articles

Local structure of the silicon implanted in a graphite single crystal

Baba, Yuji; Shimoyama, Iwao; Sekiguchi, Tetsuhiro

Hyomen Kagaku, 23(7), p.417 - 422, 2002/07

no abstracts in English

Journal Articles

Local electronic and geometric structures of silicon atoms implanted in graphite

Baba, Yuji; Sekiguchi, Tetsuhiro; Shimoyama, Iwao

Nuclear Instruments and Methods in Physics Research B, 194(1), p.41 - 46, 2002/07

 Times Cited Count:4 Percentile:68.61

no abstracts in English

68 (Records 1-20 displayed on this page)