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Last Updated :2024/10/27

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Master

Affiliation (Master)

  • Faculty of Engineering　Applied Chemistry　Functional Materials Chemistry

Affiliation (Master)

  • Faculty of Engineering　Applied Chemistry　Functional Materials Chemistry

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Profile and Settings

Degree

  • Dr.Eng., 12/2001, Hokkaido University, Sapporo（Hokkaido University）

Profile and Settings

  • Name (Japanese)

    Fushimi

  • Name (Kana)

    Koji

  • Name

    200901028284650522

Achievement

Research Interests

  • 表面物理化学   腐食科学   電気化学   Surfacial physical chemistry   Corrosion Science   Electrochemistry   

Research Areas

  • Nanotechnology/Materials / Material fabrication and microstructure control

Research Experience

  • 2015/06 - Today Hokkaido University Faculty of Engineering Associate Professor
  • 2010/04 - 2015/05 Hokkaido University Faculty of Engineering Associate Professor
  • 2008/04 - 2010/03 Hokkaido University Faculty of Engineering Associate Professor
  • 2007/04 - 2008/03 Hokkaido University Graduate School of Engineering Assistant Professor
  • 2005/04 - 2007/03 Hokkaido University Graduate School of Engineering Research Associate
  • 1995/04 - 2005/03 Hokkaido University Graduate School of Engineering Research Associate
  • 2002/04 - 2003/07 Max-Planck-Institute for Iron Research, Germany Visiting Researcher
  • 1992/04 - 1995/07 Toyo Seikan Kaisya Dept. R&D, Toyo Seikan Group Researcher

Education

  •        - 1992  Hokkaido University
  •        - 1992  Hokkaido University  Graduate School, Division of Engineering
  •        - 1990  Hokkaido University  School of Engineering  Department of Applied Chemistry
  •        - 1990  Hokkaido University  Faculty of Engineering

Awards

  • 2022/05 Japan Society of Corrosion Engineering The JSCE Award for Scientific Contribution
     金属材料表面のその場観察のための微小電気化学測定法の開発と腐食防食への適用
  • 2018/03 The Iron and Steel Institute of Japan The Best Year's Paper Award, Sawamura Award
     
    受賞者: FUSHIMI KojiHydrogen Permeation into a Carbon Steel Sheet Observed by a Micro-capillary Combined with a Devanathan-Stachurski Cell, ISIJ International, Vol.56(2016), No.3, pp.431-435.
  • 2017/05 公益社団法人腐食防食学会 平成29年度論文賞
     
    受賞者: 河野崇史;石井知洋;梶山浩志;木村光男;伏見公志ステンレス鋼の溶接ヒートティント部の局所電気化学挙動
  • 2002/05 社団法人腐食防食協会 平成14年度進歩賞
     
    受賞者: 伏見公志

Published Papers

  • Sho Kitano, Hiroya Motohashi, Mana Iwai, Koji Fushimi, Yoshitaka Aoki, Hiroki Habazaki
    Applied Surface Science 2024/10
  • Joe Hayashi, Shinichiro Iwamura, Yuta Nakasaka, Mengfei Wang, Sunao Shoji, Yuichi Kitagawa, Koji Fushimi, Shin R. Mukai, Yasuchika Hasegawa
    Chemistry – A European Journal 0947-6539 2024/09/09 
    Triple‐stranded helical lanthanide MOFs with CO2 adsorption properties were investigated. Lanthanide MOFs ([Eu0.1Tb0.9(hfa)3(dpa)]n) are composed of lanthanide luminophores (Eu(III) and/or Tb(III) ions), fluorinated antenna ligands (hfa: hexafluoroacetylacetonate), and polyamide‐type linker ligands (dpa: 4‐(diphenylphosphoryl)‐N‐(4‐(diphenylphosphoryl)phenyl)benzamide). The cylindrical structure was characterized by single‐crystal X‐ray analysis, thermogravimetric analysis, and gas adsorption measurements. The inner surfaces of the cylindrical channels were covered with the fluorine atoms of the hfa ligands. The emission intensity ratio (IEu / ITb) in [Eu0.1Tb0.9(hfa)3(dpa)]n is affected by the CO2 gas adsorption behavior. The change in IEu / ITb value was caused by the intermolecular interactions between the CO2 gas molecules and the fluorinated ligands, resulting in an electronic structural change of the lowest triplet excited state in the photosensitized hfa ligands.
  • Kosaku Nomura, Masatoshi Sakairi, Koji Fushimi
    Corrosion Science 2024/08
  • Xiong Zetao, David Quintero, Sho Kitano, Tomoya Nagao, Mana Iwai, Yoshitaka Aoki, Koji Fushimi, Hiroki Habazaki
    Electrochimica Acta 491 0013-4686 2024/07/01 
    Anodizing is gaining popularity as a binder-free fabrication route for obtaining catalyst materials directly on the current collector without using noble metals, binders, or conductive carbon additives. Here, we fabricate promising highly active electrodes for alkaline water electrolysis by anodizing commercial FeNi and FeNiCo alloys (%wt. Fe range between 22 and 63) in an ethylene glycol-based fluoride electrolyte. Anodizing forms metal fluoride coatings, which are converted to OER active compounds (γ-NiOOH:Fe) during potential cycling in an alkaline aqueous solution (1 mol L−1 (M) KOH at 293 K) as a result of leaching of fluoride ions. The morphology, thickness, and number of active sites are influenced by the amount of Fe in the alloy, and the electrode with the highest electrochemical active surface area (Kovar alloy with a 54 %wt. Fe) shows the largest OER activity enhancement by anodizing. The performance evaluation in practical conditions (7 mol L−1 KOH at 343 K) demonstrated a highly active performance with an OER potential as low as 1.52 V at a current density of 600 mA cm−2 even for electrodes obtained in alloys with a low amount of Fe (78-Permalloy with a 22 %wt. Fe), demonstrating that anodizing is an effective way to develop highly active OER electrodes from commercially available alloys. On the other hand, anodizing is a good fluoridation route for transition metals with good results in the formation of F-enriched precursors that efficiently promote active phase formation during the catalytic process, offering the possibility of obtaining catalysts directly on the current collector in a one-step process, easily implemented in industrial applications.
  • Yuichi Kitagawa, Toranosuke Tomikawa, Kota Aikawa, Shiori Miyazaki, Tomoko Akama, Masato Kobayashi, Mengfei Wang, Sunao Shoji, Koji Fushimi, Kiyoshi Miyata, Yuichi Hirai, Takayuki Nakanishi, Ken Onda, Tetsuya Taketsugu, Yasuchika Hasegawa
    2024/05/29
  • Shota Hosoya, Sunao Shoji, Takayuki Nakanishi, Masato Kobayashi, Mengfei Wang, Koji Fushimi, Tetsuya Taketsugu, Yuichi Kitagawa, Yasuchika Hasegawa
    Inorganic Chemistry 0020-1669 2024/05/21
  • Yuya Mizushiri, Sunao Shoji, Yuichi Kitagawa, Yasuchika Hasegawa, Koji Fushimi
    International Journal of Hydrogen Energy 0360-3199 2024/05
  • Koji Fushimi, Kanta Higa, Akihiro Fujimura, Sunao Shoji, Yuichi Kitagawa, Yasuchika Hasegawa, Hideki Katayama
    Journal of The Electrochemical Society 2024/02/01
  • Fujimura, A., Abe, M., Kawano, A., Iwai, M., Kitano, S., Habazaki, H., Fushimi, K.
    Corrosion Science 227 0010-938X 2024/02
  • Yuki Tsuji, Kota Hirasawa, Sunao Shoji, Yuichi Kitagawa, Yasuchika Hasegawa, Koji Fushimi
    Tetsu-to-Hagane 2024
  • Kazuhisa Azumi, Masatoshi Sakairi, Koji Fushimi, Takashi Sato, Ken Mikami, Masazumi Miura
    Tetsu-to-Hagane 2024
  • Wang, M., Kono, M., Yamaguchi, Y., Islam, J., Shoji, S., Kitagawa, Y., Fushimi, K., Watanabe, S., Matsuba, G., Yamamoto, A., Tanaka, M., Tsuda, M., Tanaka, S., Hasegawa, Y.
    Scientific Reports 14 (1) 2045-2322 2024
  • Quintero, D., Matsuya, H., Iwai, M., Kitano, S., Fushimi, K., Habazaki, H.
    ACS Applied Materials and Interfaces 16 (1) 1944-8252 2024
  • Yasuchika Hasegawa, Yuki Konishi, Masaki Enokido, Sunao Shoji, Mengfei Wang, Koji Fushimi, Yuichi Kitagawa
    Inorganic Chemistry 62 (41) 16794 - 16800 0020-1669 2023/09/21 
    Novel hydrophilic and color-changeable single chameleon luminophores composed of Tb(III)/Sm(III) nona-nuclear clusters [TbxSm9-x(Sal-PEG-n)16(μ-OH)10]+(NO3)− (x = 1, 2, 3, and 9; Sal-PEG-n: salicylate polyethylene glycolmethylester, n = 2 and 4) are reported for water mapping measurements. Their characteristic sandglass structures and aggregates were analyzed using X-ray single crystal analysis and dynamic light scattering (DLS) measurements. The green- and yellow-luminescence of [Tb3Sm6(Sal-PEG-4)16(μ-OH)]+(NO3)− in water were observed at 20 and 50 °C, respectively. The ratio-metric luminescence analysis using green Tb(III) and orange Sm(III) emission bands is a promising candidate for exact temperature distribution measurements in fluid dynamics. The effective temperature-sensing property based on the competitive intramolecular energy transfer processes between Tb(III)-to-ligand and Tb(III)-to-Sm(III) in a non-a-nuclear cluster is explained using temperature-dependent kinetic analyses in the excited state.
  • Akihiro Fujimura, Sunao Shoji, Yuichi Kitagawa, Yasuchika Hasegawa, Takashi Doi, Koji Fushimi
    Electrochimica Acta 463 142843 - 142843 0013-4686 2023/09/20 
    The dissolution behavior of the Fe-Cr alloys in acidic Na2SO4 solutions was investigated using online inductively coupled plasma-optical emission spectrometry (ICP-OES). The dissolution current density of pure Fe measured by spectroscopic analysis shows an anodic Tafel slope of 60 mV decade–1, while the anodic Tafel slope of Fe species in Fe-Cr alloys increases to 120 mV decade–1 with increasing Cr content in the alloy, suggesting that the rate-determining step of the anodic reaction mechanism is dependent on the Cr content. The mass balance on the surface of Fe-6Cr in the active-passive transition indicated that Cr species preferentially dissolved through a salt layer formed on the alloy surface. Some oxidized products that existed in the salt layer in the active region dissolved when the surface changed to the passive state. The anodic reaction mechanism and passivation processes of Fe-Cr alloys, including pure Fe, are discussed quantitatively.
  • Yuichi Kitagawa, Kaori Shima, Takuma Nakai, Marina Kumagai, Shun Omagari, Pedro Paulo Ferreira da Rosa, Sunao Shoji, Koji Fushimi, Yasuchika Hasegawa
    Communications Chemistry 6 (1) 2023/06/22 
    Abstract Luminescent lanthanide complexes containing effective photosensitizers are promising materials for use in displays and sensors. The photosensitizer design strategy has been studied for developing the lanthanide-based luminophores. Herein, we demonstrate a photosensitizer design using dinuclear luminescent lanthanide complex, which exhibits thermally-assisted photosensitized emission. The lanthanide complex comprised Tb(III) ions, six tetramethylheptanedionates, and phosphine oxide bridge containing a phenanthrene frameworks. The phenanthrene ligand and Tb(III) ions are the energy donor (photosensitizer) and acceptor (emission center) parts, respectively. The energy-donating level of the ligand (lowest excited triplet (T1) level = 19,850 cm−1) is lower than the emitting level of the Tb(III) ion (5D4 level = 20,500 cm−1). The long-lived T1 state of the energy-donating ligands promoted an efficient thermally-assisted photosensitized emission of the Tb(III) acceptor (5D4 level), resulting in a pure-green colored emission with a high photosensitized emission quantum yield (73%).
  • Takeshi Matsuda, Shinichi Furuya, Rie Kaneko, Koji Fushimi
    Transaction of the IMF 101 (6) 329 - 337 0020-2967 2023/06 [Refereed]
     
    The corrosion protection behaviour of electrogalvanised steel sheets (EG) by the tetravalent vanadium ion was investigated. Immersion of the bare EG in a NaCl solution revealed that the addition of vanadium(IV) oxide sulphate to the solution led to a transition of the open circuit potential to less noble and the formation of vanadium oxides on the EG surface. The oxide layer included not only vanadium(III) oxides but also a small amount of ZnO, indicating that Zn on the EG surface was oxidised while the vanadium(IV) species was reduced to the vanadium(III) species. The corrosion current density of the EG with the adhering vanadium(III) species was one order of magnitude smaller than that of the bare EG, clearly suggesting that zinc corrosion was reduced by suppressing the reduction reaction of dissolved oxygen. The vanadium(IV) species could be a candidate as a self-healing inhibitor for chromate-free coating technologies by controlling the coupling of Zn oxidation and vanadium(IV) reduction.
  • Takuma Nakai, Kaori Shima, Sunao Shoji, Koji Fushimi, Yasuchika Hasegawa, Yuichi Kitagawa
    Frontiers in Chemistry 11 2023/04/14 
    A novel design strategy of stacked organic fluorophores using dinuclear lanthanide (Ln(III)) complexes is demonstrated for the formation of excimer. The dinuclear Ln(III) complexes are composed of two Ln(III) (Eu(III) or Gd(III)) ions, six hexafluoroacetylacetonate (hfa), and two pyrene-based phosphine oxide ligands. Single-crystal analysis revealed a rigid pyrene-stacked structure via CH-F (pyrene/hfa) intramolecular interactions. The rigid aggregation structures of the two-typed organic ligands around Ln(III) resulted in high thermal stability (decomposition temperature: 340°C). The aggregated ligands exhibited excimer-type green emission from the stacked pyrene-center. The change in the Ln(III) ion promotes effective shifts of excimer emissions (Gd(III):500 nm, Eu(III):490 nm). The organic aggregation system using red-luminescent Eu(III) also provides temperature-sensitive ratiometric emission composed of π-π* and 4f-4f transitions by energy migration between aggregated ligands and Eu(III).
  • K. Fushimi, H. Yanagimoto, S. Nakatsuji, S. Shoji, Y. Kitagawa, Y. Hasegawa, K. Baba
    Journal of The Electrochemical Society 170 (4) 041508 - 041508 0013-4651 2023/04/01 
    A liquid-phase ion gun (LPIG) was used to create a local H2S enriched environment near Cr-containing steel surface in Na2S solutions in attempt to induce sulfide stress cracking on the specimen surface. In a 1.5 mM Na2S solution, anodic polarization of LPIG Pt microelectrode at a potential of 1.90 V vs SHE resulted in that local solution was successfully acidified to below pH 4, a pseudo-sour environment. When Cr-containing steels were potentiostatically polarized under this pseudo-sour environment by LPIG, sulfides were formed on the specimen surface depending on Cr-concentration, specimen potential, and chloride ion in solution. When LPIG was operated on Cr-containing steels subjected to tensile stress using a four-point bending tester, cracks were formed on the steel surface.
  • Koji Fushimi, Tomoya Takano, Yoganandan Govindaraj, Ryosuke Saito, Masatoshi Sakairi
    Electrochimica Acta 441 141776 - 141776 0013-4686 2023/02 
    A miniature pH detection probe which was fabricated from an oxidized tungsten wire electrode and a solid-contact silver-silver chloride electrode was developed and used for monitoring alkalinity of cement pastes. The pH detection probe which was embedded in wet cement paste block showed the stable potential differences assigned to pH 12–14 for at least more than 2 months. Although the potential difference of the probe showed inconsistent values in dry cement paste, the probe recovered to show the correct values after the re-wetting of cement paste. In an accelerated corrosion test of rebar co-embedded in cement paste using a pH detection probe, the probe showed the potential difference shift in acidic direction and illustrated depassivation of steel surface, accumulation of corrosion products in the paste, and crack formation of the paste. It was indicated that the pH detection probe was effective to evaluate not only alkalinity but also the deterioration of reinforced concrete.
  • Sourav Kr. Saha, Tomoya Takano, Koji Fushimi, Masatoshi Sakairi, Ryosuke Saito
    SURFACES AND INTERFACES 36 2468-0230 2023/02 
    The curing behaviour of cement paste and formation of passive film on iron were investigated by electrochemical techniques and X-ray photoelectron spectroscopy (XPS). Open circuit potential of iron was monitored with the newly developed solid-contact-chloride reference electrode in cement paste with pH -13 laid at -0 VSHE for 56 d, indicating iron was kept in passive state. Electrochemical impedance spectroscopy results showed significant increasing trend of film and cement paste resistance with curing time. XPS elucidated formation of ferric hydroxide and ferric oxide was efficient to passivate the iron rather than ferrous products. Iron surface receded from corrosion due to high-alkaline environment of cement paste and formation of passive film.
  • Ryohei Sato, Atsuo Utagawa, Koji Fushimi, Feng Li, Takuya Isono, Kenji Tajima, Toshifumi Satoh, Shin-ichiro Sato, Hiroshi Hirata, Yoshihiro Kikkawa, Takuya Yamamoto
    Polymers 15 (3) 666 - 666 2023/01/28 
    The redox behaviors of macrocyclic molecules with an entirely π-conjugated system are of interest due to their unique optical, electronic, and magnetic properties. In this study, defect-free cyclic P3HT with a degree of polymerization (DPn) from 14 to 43 was synthesized based on our previously established method, and its unique redox behaviors arising from the cyclic topology were investigated. Cyclic voltammetry (CV) showed that the HOMO level of cyclic P3HT decreases from –4.86 eV (14 mer) to –4.89 eV (43 mer), in contrast to the linear counterparts increasing from –4.94 eV (14 mer) to –4.91 eV (43 mer). During the CV measurement, linear P3HT suffered from electro-oxidation at the chain ends, while cyclic P3HT was stable. ESR and UV–Vis–NIR spectroscopy suggested that cyclic P3HT has stronger dicationic properties due to the interactions between the polarons. On the other hand, linear P3HT showed characteristics of polaron pairs with multiple isolated polarons. Moreover, the dicationic properties of cyclic P3HT were more pronounced for the smaller macrocycles.
  • Enokido, M., Sasaki, K., Shoji, S., Wang, M., Fushimi, K., Kitagawa, Y., Hasegawa, Y.
    Journal of Physical Chemistry C 127 (49) 1932-7455 2023
  • Makoto Tsurui, Yuichi Kitagawa, Sunao Shoji, Koji Fushimi, Yasuchika Hasegawa
    Dalton Transactions 52 (3) 796 - 805 1477-9226 2023 
    Three types of Eu(iii) coordination polymers with distorted chiral ligands were prepared for elucidating the relationship between their structural distortions, ligand-to-metal charge transfer, and circularly polarized luminescence properties.
  • Pedro Paulo Ferreira da Rosa, Yuichi Kitagawa, Sunao Shoji, Hironaga Oyama, Keisuke Imaeda, Naofumi Nakayama, Koji Fushimi, Hidehiro Uekusa, Kosei Ueno, Hitoshi Goto, Yasuchika Hasegawa
    Nature Communications 13 (1) 2022/12 
    Abstract Soft-crystals are defined as flexible molecular solids with highly ordered structures and have attracted attention in molecular sensing materials based on external triggers and environments. Here, we show the soft-crystal copolymerization of green-luminescent Tb(III) and yellow-luminescent Dy(III) coordination centers. Soft-crystal polymerization is achieved via transformation of monomeric dinuclear complexes and polymeric structures with respect to coordination number and geometry. The structural transformation is characterized using single-crystal and powder X-ray diffraction. The connected Tb(III) crystal-Dy(III) crystal show photon energy transfer from the Dy(III) centre to the Tb(III) centre under blue light excitation (selective Dy(III) centre excitation: 460 ± 10 nm). The activation energy of the energy transfer is estimated using the temperature-dependent emission lifetimes and emission quantum yields, and time-dependent density functional theory (B3LYP) calculations. Luminescence-conductive polymers, photonic molecular trains, are successfully prepared via soft-crystal polymerization on crystal media with remarkable long-range energy migration.
  • Akihiro Fujimura, Sunao Shoji, Yuichi Kitagawa, Yasuchika Hasegawa, Takashi Doi, Koji Fushimi
    Electrochimica Acta 433 141246 - 141246 0013-4686 2022/11
  • Sunao Shoji, Hideyuki Saito, Yutaka Jitsuyama, Kotono Tomita, Qiang Haoyang, Yukiho Sakurai, Yuhei Okazaki, Kota Aikawa, Yuki Konishi, Kensei Sasaki, Koji Fushimi, Yuichi Kitagawa, Takashi Suzuki, Yasuchika Hasegawa
    Scientific Reports 12 (1) 2022/10/26 
    Abstract The stimulation of photosynthesis is a strategy for achieving sustainable plant production. Red light is useful for plant growth because it is absorbed by chlorophyll pigments, which initiate natural photosynthetic processes. Ultraviolet (UV)-to-red wavelength-converting materials are promising candidates for eco-friendly plant cultures that do not require electric power. In this study, transparent films equipped with a UV-to-red wavelength-converting luminophore, the Eu3+ complex, were prepared on commercially available plastic films for plant growth experiments. The present Eu3+-based films absorb UV light and exhibit strong red luminescence under sunlight. Eu3+-painted films provide significant growth acceleration with size increment and biomass production for vegetal crops and trees in a northern region. The plants cultured with Eu3+-painted films had a 1.2-fold height and 1.4-fold total body biomass than those cultures without the Eu3+ luminophores. The present film can promote the plant production in fields of agriculture and forestry.
  • Yuichi Kitagawa, Ryoma Moriake, Tomoko Akama, Koki Saito, Kota Aikawa, Sunao Shoji, Koji Fushimi, Masato Kobayashi, Tetsuya Taketsugu, Yasuchika Hasegawa
    ChemPlusChem 2192-6506 2022/07/13
  • Makoto Tsurui, Yuichi Kitagawa, Sunao Shoji, Hitomi Ohmagari, Miki Hasegawa, Masayuki Gon, Kazuo Tanaka, Masato Kobayashi, Tetsuya Taketsugu, Koji Fushimi, Yasuchika Hasegawa
    The Journal of Physical Chemistry B 126 (20) 3799 - 3807 1520-6106 2022/05/26
  • Yuichi Kitagawa, Ayu Naito, Kota Aikawa, Kaori Shima, Sunao Shoji, Koji Fushimi, Yasuchika Hasegawa
    CHEMISTRY-A EUROPEAN JOURNAL 28 (16) 0947-6539 2022/02 
    A spin-selective tribo-chemical reaction using a dinuclear lanthanide complex is demonstrated for the first time. The dinuclear complex is composed of two Eu-III ions, hexafluoroacetylacetonato ligands, and anthracene-based phosphine oxide bridges. Single-crystal analysis revealed a face-to-face-type anthracene dimer structure in the dinuclear Eu-III complex. Mechanical stimulus on the dinuclear Eu-III complex induced selective formation of oxidized anthracene. The tribo-chemical reaction is based on a characteristic energy-transfer pathway for the selective formation of an excited triplet state.
  • Kitagawa, Y., Naito, A., Aikawa, K., Shima, K., Shoji, S., Fushimi, K., Hasegawa, Y.
    Chemistry (Weinheim an der Bergstrasse, Germany) 28 (16) 1521-3765 2022
  • Fushimi, K.
    Zairyo/Journal of the Society of Materials Science, Japan 71 (6) 1880-7488 2022
  • Koji Fushimi, Haruka Okuyama, Kai Ohshimizu, Sunao Shoji, Yuichi Kitagawa, Yasuchika Hasegawa
    Tetsu-to-Hagane 107 (12) 1011 - 1019 0021-1575 2021/12
  • Teng Zhang, Yuichi Kitagawa, Ryoma Moriake, Pedro Paulo Ferreira da Rosa, Md Jahidul Islam, Tomoki Yoneda, Yasuhide Inokuma, Koji Fushimi, Yasuchika Hasegawa
    CHEMISTRY-A EUROPEAN JOURNAL 0947-6539 2021/09 
    In this study, we have demonstrated a two-legged, upright molecular design method for monochromatic and bright red luminescent Ln(III)-silica nanomaterials. A novel Eu-III-silica hybrid nanoparticle was developed by using a doubly binding TPPO-Si(OEt)(3) (TPPO: triphenyl phosphine oxide) linker. The TPPO-Si(OEt)(3) was confirmed by H-1, P-31, Si-29 NMR spectroscopy and single-crystal X-ray analysis. Luminescent Eu(hfa)(3) and Eu(tfc)(3) moieties (hfa: hexafluoroacetylacetonate, tfc: 3-(trifluoromethylhydroxymethylene)camphorate) were fixed onto TPPO-Si(OEt)(3)-modified silica nanoparticles, producing Eu(hfa)(3)(TPPO-Si)(2)-SiO2 and Eu(tfc)(3)(TPPO-Si)(2)-SiO2, respectively. Eu(hfa)(3)(TPPO-Si)(2)-SiO2 exhibited the higher intrinsic luminescence quantum yield (93 %) and longer emission lifetime (0.98 ms), which is much larger than those of previously reported Eu-III-based hybrid materials. Eu(tfc)(3)(TPPO-Si)(2)-SiO2 showed an extra-large intrinsic emission quantum yield (54 %), although the emission quantum yield for the precursor Eu(tfc)(3)(TPPO-Si(OEt)(3))(2) was found to be 39 %. These results confirmed that the TPPO-Si(OEt)(3) linker is a promising candidate for development of Eu-III-based luminescent materials.
  • Yuichi Kitagawa, Kenji Matsuda, Pedro Paulo Ferreira da Rosa, Koji Fushimi, Yasuchika Hasegawa
    Chemical Communications 57 (65) 8047 - 8050 1359-7345 2021/08/21 
    A long-lived near-infrared Nd(iii) emission is demonstrated using a Tb(iii) donor. The observed emission lifetime of 290 μs at 1057 nm for a Tb(iii)-Nd(iii) dinuclear complex is attributed to the long-lived Tb(iii) donor and the appropriate spacing between the lanthanide ions. This design strategy leads to novel lanthanide photophysics.
  • Joe Hayashi, Sunao Shoji, Yuichi Kitagawa, Koji Fushimi, Yasuchika Hasegawa
    Materials Letters 297 0167-577X 2021/08/15 
    A novel lanthanide coordination polymer composed of Eu(III) ion, low-vibrational frequency hfa (hfa: hexafluoroacetylacetonato), and phosphine oxide ligand with amide groups (dpba: N,N'-(ethane-1,2-diyl)bis(4-(diphenylphosphoryl)benzamide)), Eu-dpba is reported. A lanthanide coordination polymer with alkyl groups (dph: 1,6-bis(diphenylphosphoryl)hexane), Eu-dph is also prepared, as a reference sample. Eu-dpba showed phase transition behavior at 128 °C, although alkyl-bridged Eu-dph showed no phase transition behavior by differential scanning calorimeter measurements. The smooth surface on the Eu-dpba after heat treatment was observed using scanning electron microscope. The photophysical properties were estimated using the emission spectra and the emission lifetimes. We found that the emission quantum yield of Eu-dpba with heat treatment is the same as that of Eu-dpba without heat treatment.
  • Akihiro Fujimura, Yuichi Kitagawa, Yasuchika Hasegawa, Takashi Doi, Koji Fushimi
    Journal of The Electrochemical Society 168 (5) 0013-4651 2021/05/01 
    Electrochemical ellipso-microscopy was combined with the channel flow triple electrode method to evaluate the active-passive transition behavior of Fe-6 mass% Cr in acidic sodium sulfate solutions under the control of mass-transport reaction. During potentiodynamic polarization of the Fe-6 mass% Cr specimen electrode (SE), the SE surface was monitored by ellipso-microscopy and generated Fe(II) and Cr(III) species from the SE were detected at two detector electrodes arranged downstream in parallel. Forced convection of the electrolyte solution affected the mass-transport process of Cr(III) species on the SE surface in the latter half of the active region. In addition, the electrolyte solution flow resulted in enhancement of the passivation process and Cr enrichment on the passive surface. The effects of the electrolyte solution flow on active-passive transition and improvement of the passive film resistance are discussed.
  • Yasuchika Hasegawa, Natsumi Sato, Joe Hayashi, Yuichi Kitagawa, Koji Fushimi
    ChemistrySelect 6 (12) 2812 - 2816 2021/03/26 
    Luminescent EuIII coordination polymer with amorphous transformation and thermo-sensing abilities under higher temperature, [Eu(hfa)3(tppa)n]m (hfa: hexafluoroacetylacetonate, tppa: tri-diphenylphosphoryl-4,4,4-triphenylamine) is reported. The glass transition and decomposition temperatures are found to be 142 °C and 270 °C, respectively. The intrinsic emission quantum yield Φ4f−4f of [Eu(hfa)3(tppa)n]m was estimated to be 69 % in solid state. [Eu(hfa)3(tppa)n]m shows effective decrease in the emission lifetime upon increasing the temperature from 320 to 400 K. The temperature-depended emission lifetime is caused by the back energy transfer from emitting level of EuIII ion (5D0) to the LLCT band (tppa ligand to hfa ligand) in [Eu(hfa)3(tppa)n]m. Thermo-sensitive lanthanide luminophore with stable glass formation in higher temperature (>100 °C) is useful for surface temperature detection in the field of high-speed wind tunnel experiments such as aircraft and automobile designs.
  • Yuichi Kitagawa, Ayu Naito, Koji Fushimi, Yasuchika Hasegawa
    Chemistry - A European Journal 27 (7) 2279 - 2283 0947-6539 2021/02/01 
    A tribo-excited chemical reaction using a stacked lanthanide coordination polymer is demonstrated for the first time. The polymer is composed of a EuIII ion, hexafluoroacetylacetonato ligands, and an anthracene-based phosphine oxide bridge. The tightly stacked structure with hydrogen bonding was characterized by X-ray crystal structure analysis. The mechanical stimulus leads to tribo-excited oxidation in the EuIII coordination polymer. Electron ionization mass spectroscopy and photo-spectroscopic analysis reveal that the chemical product afforded by tribo-oxidation is different from that obtained by photo-oxidation.
  • Yuichi Kitagawa, Ayu Naito, Koji Fushimi, Yasuchika Hasegawa
    RSC Advances 11 (12) 6604 - 6606 2021/02/01 
    Pure sky-blue fluorescence (FWHM: 50 nm) from lutetium-based coordination polymer with diphenyl-anthracene derivative is demonstrated for the first time. The observed high color purity is based on the tightly packed crystal structure of the coordination polymer with multiple CH-F interactions.
  • Pedro Paulo Ferreira Da Rosa, Shiori Miyazaki, Haruna Sakamoto, Yuichi Kitagawa, Kiyoshi Miyata, Tomoko Akama, Masato Kobayashi, Koji Fushimi, Ken Onda, Tetsuya Taketsugu, Yasuchika Hasegawa
    Journal of Physical Chemistry A 125 (1) 209 - 217 1089-5639 2021/01/14 
    Photophysical properties of europium (Eu(III)) complexes are affected by ligand-to-metal charge transfer (LMCT) states. Two luminescent Eu(III) complexes with three tetramethylheptadionates (tmh) and pyridine (py), [Eu(tmh)3(py)1] (seven-coordinated monocapped-octahedral structure) and [Eu(tmh)3(py)2] (eight-coordinated square antiprismatic structure), were synthesized for geometrical-induced LMCT level control. Distances between Eu(III) and oxygen atoms of tmh ligands were estimated using single-crystal X-ray analyses. The contribution percentages of π-4f mixing in HOMO and LUMO at the optimized structure in the ground state were calculated using DFT (LC-BLYP). The Eu-O distances and their π-4f mixed orbitals affect the energy level of LMCT states in Eu(III) complexes. The LMCT energy level of an eight-coordinated Eu(III) complex was higher than that of a seven-coordinated Eu(III) complex. The energy transfer processes between LMCT and Eu(III) ion were investigated using temperature-dependent and time-resolved emission lifetime measurements of 5D0 → 7FJ transitions of Eu(III) ions. In this study, the LMCT-dependent energy transfer processes of seven- and eight-coordinated Eu(III) complexes are demonstrated for the first time.
  • Yuichi Kitagawa, Marina Kumagai, Pedro Paulo Ferreira da Rosa, Koji Fushimi, Yasuchika Hasegawa
    Chemistry - A European Journal 27 (1) 264 - 269 0947-6539 2021/01/04 
    A design for an effective molecular luminescent thermometer based on long-range electronic coupling in lanthanide coordination polymers is proposed. The coordination polymers are composed of lanthanide ions EuIII and GdIII, three anionic ligands (hexafluoroacetylacetonate), and a chrysene-based phosphine oxide bridges (6,12-bis(diphenylphosphoryl)chrysene). The zig-zag orientation of the single polymer chains induces the formation of packed coordination structures containing multiple sites for CH-F intermolecular interactions, resulting in thermal stability above 350 °C. The electronic coupling is controlled by changing the concentration of the GdIII ion in the EuIII-GdIII polymer. The emission quantum yield and the maximum relative temperature sensitivity (Sm) of emission lifetimes for the EuIII-GdIII polymer (Eu:Gd=1:1, Φtot=52 %, Sm=3.73 % K−1) were higher than those for the pure EuIII coordination polymer (Φtot=36 %, Sm=2.70 % K−1), respectively. Enhanced temperature sensing properties are caused by control of long-range electronic coupling based on phosphine oxide with chrysene framework.
  • Fushimi Koji, Ishii Nozomi, Nakajima Ayako, Kitagawa Yuichi, Hasegawa Yasuchika, Matsuo Yasutaka
    ISIJ International 61 (4) 1112 - 1119 0915-1559 2021 
    Microelectrodes for hydrogen permeation measurements were fabricated by photolithography. Although the application of a positive-type photoresist coating was effective for the formation of a circle-shaped pattern with a diameter of several tens of micrometers on an iron surface, the coating had poor adhesion to the iron surface and poor durability in an H2SO4 solution. However, the addition of a silica coating derived from tetraethoxysilane (TEOS) on the iron surface as an inner layer resulted in improvement of durability as well as resistance of the coating. Furthermore, the introduction of a layer derived from a mixture of TEOS and glycidyl 3-trimethoxysilylpropyl ether (GPTMS) between the inner layer derived from TEOS and the photoresist coating resulted in long durability showing a large impedance of more than 109 Ω cm2 for 4×105 s in an H2SO4 solution. Cathodic polarization of the microelectrode on the iron surface revealed that the hydrogen evolution reaction (HER) rate is dependent on the plane orientation of the surface. HER rate on an SCM435 steel surface also strongly depended on the microstructure and hardness of the local surface.
  • Yamamoto Yudai, Kitagawa Yuichi, Hasegawa Yasuchika, Fushimi Koji
    ISIJ International 61 (4) 1064 - 1070 0915-1559 2021 
    The electrochemical hydrogen penetration measurement technique, to which a sinusoidal perturbation method was applied, was modified using a signal containing multiple frequency components. The technique was successfully applied to measurement of the hydrogen diffusion coefficient in a ferric sheet specimen. A series of numerical calculations for the technique, in which the constituent frequencies of the signal were selected from the measurement result, also provided the same diffusion coefficient and verified the validity of the technique. The use of this technique enables rapid determination of the hydrogen diffusion coefficient in a specimen.
  • Yudai Yamamoto, Andrei Ionut Mardare, Jan Philipp Kollender, Cezarina Cela Mardare, Dominik Recktenwald, Koji Fushimi, Achim Walter Hassel
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 168 (1) 011503 - 011503 0013-4651 2021/01 
    An aluminium-samarium binary library with a varying Sm concentration between 4 to 14 at.% was produced using a thermal co-evaporation technique. Morphological and crystallographic characterization of the parent metal alloys revealed compositionally dependent surface structure and atomic arrangements. Grains resembling pure Al on the surface slowly disappeared with increasing Sm content and above 8 at.% Sm nucleation of the AlSm2 intermetallic phase was observed. Scanning droplet cell microscopy was used for a comprehensive electrochemical characterization along the Al-Sm compositional gradient. Anodic oxide formation under high field conditions was discussed for alloys below the compositional threshold of 8 at.% Sm. Above this threshold a continuous increase of Sm dissolution during anodization with increasing Sm concentration was proven by inductively coupled plasma optical emission spectroscopy. Coulometry followed by EIS allowed mapping of the oxide formation factors and oxide electrical permittivity as material constants for single Al-Sm alloys. A small increase of both material constants for alloys below the compositional threshold described the Sm contribution to the anodization process. An apparent enhancement of their values at alloys above the threshold was directly attributed to the increased Sm dissolution rates reaching values of 2 ng cm(-2) s(-1) at 12 at.% Sm.
  • Yuichi Kitagawa, Satoshi Wada, M. D.Jahidul Islam, Kenichiro Saita, Masayuki Gon, Koji Fushimi, Kazuo Tanaka, Satoshi Maeda, Yasuchika Hasegawa
    Communications Chemistry 3 (1) 2020/12/01 
    Artificial light plays an essential role in information technologies such as optical telecommunications, data storage, security features, and the display of information. Here, we show a chiral lanthanide lumino-glass with extra-large circularly polarized luminescence (CPL) for advanced photonic security device applications. The chiral lanthanide glass is composed of a europium complex with the chiral (+)-3-(trifluoroacetyl)camphor ligand and the achiral glass promoter tris(2,6-dimethoxyphenyl)phosphine oxide ligand. The glass phase transition behavior of the Eu(III) complex is characterized using differential scanning calorimetry. The transparent amorphous glass shows CPL with extra-large dissymmetry factor of gCPL = 1.2. The brightness of the lumino-glass is one thousand times larger than that of Eu(III) luminophores embedded in polymer films of the same thickness at a Eu(III) concentration of 1 mM. The application of the chiral lanthanide lumino-glass in an advanced security paint is demonstrated.
  • Koji Fushimi
    Communications Chemistry 3 (1) 2399-3669 2020/12/01 [Refereed][Not invited]
     
    © 2020, The Author(s). Photosensitizer design to allow effective use of low-energy light is important for developing photofunctional materials. Herein, we describe a rational photosensitizer design for effective use of low-energy light. The developed photosensitizer is a stacked nanocarbon based on a rigid polyaromatic framework, which allows efficient energy transfer from the low-energy T1 level to the energy acceptor. We prepared an Eu(III) complex consisting of a luminescent center (Eu(III)) and stacked-coronene photosensitizer. The brightness of photosensitized Eu(III) excited using low-energy light (450 nm) is more than five times higher than the maximum brightness of previously reported Eu(III) complexes.
  • Yasuchika Hasegawa, Katsumasa Koide, Makoto Tsurui, Yuichi Kitagawa, Takayuki Nakanishi, Yoshihiro Doi, Yukio Hinatsu, Koji Fushimi
    ChemPhysChem 21 (17) 2019 - 2024 1439-4235 2020/09/02 
    Semiconductor nanomaterials with efficient polarized-light control in the blue region of the visible spectrum are promising candidates for modern and future photo-information technology, display devices, and optical sensing applications. New-type semiconductor Eu(OCN)2 nanocrystals with circularly polarized absorption (CD: circular dichroism) and emission (CPL: circularly polarized luminescence) under an applied magnetic field are demonstrated here for the first time. The effective CD signal at 1.6 T was observed at approximately 440 nm. The dissymmetry factor of CPL under 100 K, gM-CPL, was estimated to be 0.01. These characteristic circularly polarized absorption and emission phenomena of Eu(OCN)2 nanocrystals should be caused by combination between the “Faraday A and C terms” of the magnetic moment in the excited state. Polarized-light control using Eu(OCN)2 nanocrystals in the blue-light region of the electromagnetic spectrum is a large first step into a new world of photo-functional semiconductor nanomaterials.
  • Koji Fushimi
    ChemPhysChem 1439-4235 2020/09/02
  • Koji Fushimi
    ChemPlusChem 85 (9) 1989 - 1993 2192-6506 2020/09 
    A luminescent EuIII coordination polymer with O2-sensing units under air, EuIII-hcpt (hcpt: 2,3,6,7,10,11-hexakis(4-carboxy-phenyl)triphenylene), is reported. The hexadentate carboxylic acids in hcpt ligands play an important role in the formation of tight-packed three-dimensional networks in EuIII-hcpt, giving hyper thermo-stable structures (decomposition temperature=420 °C). The three-dimensional porous network promotes bright luminescence (4f–4f emission quantum yield=70 %). The emission lifetime of EuIII-hcpt under vacuum (0.86 ms) was twice as large as that under O2 (0.48 ms, 1 atom:101.3 kPa). The Arrhenius analysis of the emission decay profile indicates that the back energy transfer (BEnT) from the emitting level of the europium(III) ion to the excited T1 state of the hcpt ligand should be activated at room temperature. The gradual decrease of emission lifetime is caused by the BEnT process in EuIII-hcpt. Finally, an advanced pressure-sensitive luminophore is demonstrated.
  • Koji Fushimi
    Chemical Physics Letters 749 0009-2614 2020/06 
    Aggregation-induced emission (AIE) of a Eu(III) complex using ligand-to-metal charge transfer band is demonstrated. The Eu(III) complex comprises three anionic 2,2,6,6-tetramethyl-3,5-heptanedionate (tmh) ligands and one large π-conjugated neutral dipyrido[3,2-f:2′,3′-h]quinoxaline (dpq) ligand. Crystalline H-aggregates of the Eu(III) complex were characterized by X-ray crystal structure analysis. H-aggregation-induced emission (H-AIE) properties were evaluated using emission spectra, emission lifetime, and quantum yields. The energy transfer efficiency of the H-aggregate in the solid state is five times larger than that of the isolated Eu(III) complex in solution.
  • Koji Fushimi
    Electrochimica Acta 346 136237 - 136237 0013-4686 2020/06
  • Makoto Tsurui, Yuichi Kitagawa, Koji Fushimi, Masayuki Gon, Kazuo Tanaka, Yasuchika Hasegawa
    Dalton transactions (Cambridge, England : 2003) 49 (16) 5352 - 5361 1477-9226 2020/04/07 [Refereed][Not invited]
     
    Luminescent Eu(iii) complexes with point-chiral phosphine oxide ligands, [Eu(hfa)3((R,R)-B2QPO)] (hfa: hexafluoroacetylacetonato, B2QPO: 2,3-bis(tert-butylmethylphosphine oxide)quinoxaline) and [Eu(hfa)3((R)-B3QPO)] (B3QPO: 2-tert-butylmethylphosphine oxide-3-(di-tert-butylphosphineoxide)quinoxaline), are reported for the investigation of the electronic strain effect on the coordination sphere. Single crystal X-ray crystallography reveals the strong structural strain of the hfa ligands in [Eu(hfa)3((R,R)-B2QPO)]. The emission quantum yields of [Eu(hfa)3((R,R)-B2QPO)] in solution (55%) and solid (63%) are comparable to those of previously reported bright luminescent Eu(iii) complexes. The chiroptical properties of [Eu(hfa)3((R,R)-B2QPO)] and [Eu(hfa)3((R)-B3QPO)] were characterized using circular dichroism (CD) and circularly polarized luminescence (CPL) spectra. The dissymmetry factor of [Eu(hfa)3((R,R)-B2QPO)] was estimated to be 0.08. The chiroptical phenomena of the Eu(iii) complexes are closely related to their structural (geometry) and electronic (LMCT: ligand-to-metal charge transfer) strains.
  • Yuichi Kitagawa, Marina Kumagai, P P Ferreira da Rosa, Koji Fushimi, Yasuchika Hasegawa
    Dalton transactions (Cambridge, England : 2003) 49 (10) 3098 - 3101 1477-9234 2020/03/09 [Refereed][Not invited]
     
    Herein, the π-f orbital interaction depending on the coordination geometry in the Eu(iii) complex is demonstrated. Thermal analysis and computational calculations showed the phase transition of the Eu(iii) complex based on the change in the coordination geometry. A red-shifted LMCT band and radiative rate changes associated with the phase transition were found in the Eu(iii) complex.
  • Yuichi Kitagawa, Marina Kumagai, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    Inorganic chemistry 59 (9) 5865 - 5871 1520-510X 2020/03/06 [Refereed][Not invited]
     
    Luminescent Eu(III) complexes with a ligand-to-metal charge transfer (LMCT) state were demonstrated for the development of a molecular thermometer. The Eu(III) complex was composed of three anionic ligands (hfa: hexafluoroacetylacetonate) and a phosphine oxide derivative containing a chrysene framework (diphenylphosphorylchrysene (DPCO)). The chrysene framework induced a rigid coordination structure via intermolecular interactions, resulting in a high thermal stability (decomposition point: 280 °C). The Eu(III) complex also exhibited an extremely high molar absorption coefficient (490000 cm-1 M-1), high intrinsic emission quantum yields (73%), and temperature-dependent energy migration between ligands and Eu(III) ion. The characteristic energy migration system was explained by the presence of the LMCT state based on π-f orbital interactions.
  • Yuichi Kitagawa, Marina Kumagai, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    Dalton transactions (Cambridge, England : 2003) 49 (8) 2431 - 2436 1477-9234 2020/02/25 [Refereed][Not invited]
     
    Herein the aggregation-induced emission (AIE) of a Tb(iii) complex is reported for the first time. The Tb(iii) complex is composed of three anionic ligands (acac: acetylacetonate) and one large hetero-π-conjugated neutral ligand (dpq: dipyrido[3,2-f:2',3'-h]quinoxaline). The formation of a crystalline J-aggregate of the Tb(iii) complex (CJ-Tb(iii)) was characterized by X-ray crystal structure analysis and absorption spectra. A crystalline H-aggregate (CH-Tb(iii)) was also prepared using the ligand steric effect (tmh: 2,2,6,6-tetramethyl-3,5-heptanedionate). The emission and AIE properties of CJ-Tb(iii) were evaluated using emission spectra, lifetime, and quantum yields, whereas CH-Tb(iii) did not emit photons. Density functional theory calculations predict that the AIE originates from the modulation of ligand-to-ligand charge transfer bands through J-aggregation.
  • Koji Fushimi
    Biomacromolecules 21 (2) 581 - 588 1526-4602 2020/02/10 [Refereed][Not invited]
     
    Nanofibrillated bacterial cellulose (NFBC) is produced by culturing a cellulose-producing bacterium under agitated aerobic conditions in a carboxymethylcellulose (CMC)-supplemented medium. Detailed structural analyses revealed that NFBC fiber widths varied with the degree of substitution of the CMC used, and zeta potential values decreased with the increment of CMC concentration in the medium. Transmission electron microscopy observation after immunostaining demonstrated that CMC molecules were present on the NFBC microfibril surfaces. We tested NFBC for utility as a binder for a display device that uses electrochromic (EC) material. Introduction of a quaternary ammonium group into the EC molecules enhanced their interactions with the negatively charged NFBC microfibrils. A casting process homogeneously adsorbed the EC molecules onto the surface of a transparent electrode with NFBC. A homogeneous color change was successfully observed upon applying an electric field, suggesting that NFBC could be used as a binder material for uniform surface adsorption.
  • Yasuchika Hasegawa, Takafumi Matsui, Yuichi Kitagawa, Takayuki Nakanishi, Tomohiro Seki, Hajime Ito, Yuta Nakasaka, Takao Masuda, Koji Fushimi
    Chemistry - A European Journal 25 (53) 12308 - 12315 0947-6539 2019/09/20 [Refereed][Not invited]
     
    © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Oxygen-sensitive and near-infrared (NIR) luminescent YbIII coordination polymers incorporating ligands based on pyrene derivatives were synthesized: YbIII–TBAPy and YbIII–TIAPy (TBAPy: 1,3,6,8-tetrakis(p-benzoate)pyrene; TIAPy: 1,3,6,8-tetrakis(3,5-isophthalic acid)pyrene). The coordination structures of these materials have been characterized by means of electrospray ionization mass spectrometry, X-ray diffraction analysis, and thermogravimetric analysis. Moreover, the porous structure of YbIII–TIAPy has been evaluated by measuring its N2 adsorption isotherm. The NIR luminescence properties of YbIII–TBAPy and YbIII–TIAPy have been examined by acquiring emission spectra and determining emission lifetimes under air or argon and in vacuo. YbIII–TIAPy exhibited high thermal stability (with a decomposition temperature of 400 °C), intense luminescence (with an emission quantum yield under argon of 6.6 %), and effective oxygen-sensing characteristics. These results suggest that NIR luminescent YbIII coordination polymers prepared using pyrene derivatives could have applications in novel thermo-stable oxygen sensors.
  • Koji Fushimi
    Zairyo-to-Kankyo 0917-0480 2019/05/10
  • Takeshi Matsuda, Kiran B. Kashi, Koji Fushimi, Victoria J. Gelling
    Corrosion Science Elsevier {BV} 148 188 - 197 0010-938X 2019/03 [Refereed][Not invited]
  • Toru Koizuka, Yuichi Kitagawa, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    Inorganica Chimica Acta 486 240 - 244 0020-1693 2019/02/24 [Refereed][Not invited]
     
    © 2018 Elsevier B.V. Novel luminescent tetranuclear Eu(III) complex [Eu(btfa)3(salbn)]4 (btfa: benzoyltrifluoroacetonate, salbn: N,N’-bis(salicylidene)-1,4-butanediamine) with characteristic cavity space is reported. The Eu(III) complex excited at 480 nm exhibits the highest photosensitized emission quantum yield (36%) reported for similar previously reported tetranuclear Eu(III) complexes. The Eu(III) complex with salbn and btfa also showed the spectral change under addition of K+ and Zn2+ ions. In this study, we demonstrated metal ions sensor ability of a highly luminescent Eu(III) complex.
  • Koji Fushimi, Misako Jin, Yuichi Kitagawa, Takayuki Nakanishi, Yasuchika Hasegawa
    Tetsu-To-Hagane/Journal of the Iron and Steel Institute of Japan 一般社団法人 日本鉄鋼協会 105 (1) 64 - 68 0021-1575 2019/01 [Refereed][Not invited]
     
    © 2019 Iron and Steel Institute of Japan. All Rights Reserved. Synopsis: A micro-capillary technique was applied to a Devanathan-Stachurski electrochemical cell for local measurement of hydrogen permeation into a steel sheet. An electrolyte-flowing design for the hydrogen entry side of the Devanathan-Stachurski cell successfully allowed the detection of hydrogen permeation response on hydrogen exit side electrode in a micro-capillary cell with a diameter of 250 μm. Phase shift of the detected permeation current from a sinusoidal perturbation of the electrolyte flow rate in the hydrogen entry cell was strongly dependent on the metallographic structure of the steel sheet. A local structure, in which two single grains form grain boundaries, led to hydrogen permeation more frequently than did a local structure of single grains. The results suggested that the diffusion coefficient of the boundaries was at least two-times larger than that of the grains.
  • Koji Fushimi, Ryogo Nakagawa, Yuichi Kitagawa, Yasuchika Hasegawa
    Journal of The Electrochemical Society 2019 [Refereed][Not invited]
  • Hajime Ito, Yuichi Hirai, Pedro Paulo Ferreira da Rosa, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Tomohiro Seki, Hajime Ito, Yasuchika Hasegawa
    Inorganic Chemistry 57 (23) 14653 - 14659 0020-1669 2018/12/03 [Refereed][Not invited]
  • Yamamoto, Masanori, Kitagawa, Yuichi, Nakanishi, Takayuki, Fushimi, Koji, Hasegawa, Yasuchika
    CHEMISTRY-A EUROPEAN JOURNAL 24 (67) 17719 - 17726 0947-6539 2018/12 [Refereed][Not invited]
     
    A luminescent Tb-III complex with a hexafluoroacetylacetone (hfa) ligand shows a characteristic back energy transfer (BEnT), which leads to high temperature sensitivity and potential application as a thermosensitive paint. Ligand-assisted BEnT was observed when a phosphine oxide ligand was introduced into Tb(hfa)(3) complex, which was shown to affect the activation energy (Delta E-a) and frequency factor (A) in the BEnT process between Tb-III ion and hfa ligands. According to temperature-dependent emission-lifetime measurements of mononuclear Tb(hfa)(3) complexes with monodentate phosphine oxides and polynuclear Tb(hfa)(3) complexes with bidentate phosphine oxides, the Delta E-a and A values of polynuclear Tb-III complexes were smaller than those of mononuclear Tb-III complexes. Phosphorescence spectra and lifetimes of each Gd(hfa)(3) complex revealed that excited states of hfa ligands in Tb(III)complexes differed from those of the polynuclear Tb-III complexes and mononuclear Tb-III complexes. The differences in the Delta E-a and A values between polynuclear and mononuclear Tb-III complexes were caused by the formation of different excited states, such as delocalization of the excited state in the polynuclear Tb-III complexes and localization of excited states in the mononuclear Tb-III complexes. In particular, small Delta E-a and A values of polynuclear Tb-III complexes provided high, effective activation of the BEnT at low temperature, which resulted in high-sensitive temperature-dependent phosphor materials over a wide temperature range.
  • Wada, Satoshi, Kitagawa, Yuichi, Nakanishi, Takayuki, Gon, Masayuki, Tanaka, Kazuo, Fushimi, Koji, Chujo, Yoshiki, Hasegawa, Yasuchika
    SCIENTIFIC REPORTS 8 2045-2322 2018/11 [Refereed][Not invited]
     
    3A novel mechanism for chiroptical activity inversion based on the electronic structure of metal complexes without Lambda- or Delta-type structure change was demonstrated spectroscopically and theoretically. To demonstrate the mechanism, a europium (Eu(III)) complex with chiral (+)-3-(trifluoroacetyl) camphor (+tfc) and achiral triphenylphosphine oxide (tppo) was prepared. The steric and electronic structures of the Eu(III) complex were adjusted by additional achiral tppo and coordinating acetone molecules, and were characterised by H-1 NMR, photoluminescence, and emission lifetime measurements. The optical activity of the Eu(III) complex in solution was evaluated by circularly polarized luminescence (CPL) measurements. CPL sign inversion, which was independent of Lambda- or Delta-type structure changes from the spectroscopic viewpoint, and a drastic CPL intensity enhancement were observed depending on the external achiral molecules around Eu(III) ion. These phenomena provide the first clarification of optical activity change associated with electronic structure rather than chiral coordination structure-type (Lambda or Delta) under external environments.
  • Yuichi Kitagawa, Ryuto Yachi, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    ChemistrySelect 3 (39) 10905 - 10908 2365-6549 2018/10/24 [Refereed][Not invited]
     
    © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim An asymmetric donor–acceptor–donor (D–A–D) type organic luminophore is reported for solvent and temperature sensors. The electronic absorption and luminescence properties of the luminophore were assessed from its electronic absorption and luminescence spectra, which depended on the external environment. The D–A–D luminophore showed environment-sensitive charge transfer fluorescence based on structural transformation through excited singlet states. Characteristic D–A–D phosphorescence was also observed at 494 nm, which was shorter than that of the D–A–D fluorescence (502 nm). In this study, the novel photophysical properties of a D–A–D-type luminophore induced by its asymmetric electronic structure are described.
  • Hasegawa, Y., Miura, Y., Kitagawa, Y., Wada, S., Nakanishi, T., Fushimi, K., Seki, T., Ito, H., Iwasa, T., Taketsugu, T., Gon, M., Tanaka, K., Chujo, Y., Hattori, S., Karasawa, M., Ishii, K.
    Chemical Communications 54 (76) 10695 - 10697 1364-548X 2018/09/28 [Refereed][Not invited]
  • Shun Omagari, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Koji Fushimi, Hajime Ito, Andries Meijerink, Yasuchika Hasegawa
    Journal of Luminescence 201 170 - 175 0022-2313 2018/09 [Refereed][Not invited]
     
    © 2018 Elsevier B.V. In luminescent lanthanide (Ln(III)) complexes, the yield and the lifetime of triplet excited state of organic ligands are crucial factors that affect the ligands-to-Ln(III) energy transfer efficiency. Such factors are dependent on spin-orbit coupling induced by the Ln(III) ions that mixes different multiplicity states through heavy atom and paramagnetic effects. We investigated the role of these effects on the energy transfer efficiency in synthesized nonanuclear Yb-Gd / Yb-Lu clusters ([Ln9(µ-OH)10(butyl salicylate)16]NO3, Ln9 = YbnGd9-n or YbnLu9-n, n = 0, 1, 3, 7, and 9). Based on the intensity of the fluorescence and phosphorescence of the ligands, the spin-orbit coupling strength was in the order of Yb(III) > Gd(III) > Lu(III). Various photophysical processes affecting the energy transfer efficiency in YbnGd9-n and YbnLu9-n clusters are discussed from the perspective of spin-orbit coupling and give insight in how to optimize energy transfer efficiencies.
  • Fushimi, K., Neelakantan, L., Eggeler, G., Hassel, A.W.
    Physica Status Solidi (A) Applications and Materials Science 215 (15) 1862-6319 2018/08/08 [Refereed][Not invited]
  • Toru Koizuka, Kei Yanagisawa, Yuichi Hirai, Yuichi Kitagawa, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    Inorganic Chemistry 57 (12) 7097 - 7103 1520-510X 2018/06/18 [Refereed][Not invited]
     
    Three types of red luminescent Eu(III) complexes with Schiff base and hfa ligands (hfa: hexafluoroacetylacetonate), mononuclear [Eu(hfa)2(OAc)(salen)2] (OAc: acetate anion, salen: N,N′-bis(salicylidene)ethylenediamine), brick-type [Eu2(hfa)4(OAc)2(salbn)2] (salbn: N,N′-bis(salicylidene)-1,4-butanediamine), and polynuclear [Eu(hfa)2(OAc)(salhen)]n (salhen: N,N′-bis(salicylidene)-1,6-hexanediamine) are reported for white light-emitting diode (LED) devices. Among these complexes, brick-type [Eu2(hfa)4(OAc)2(salbn)2] excited by blue light (460 nm) exhibits the photosensitized quantum yield (φπ-π∗ = 47%) and remarkably high efficiency of sensitization (ηsens = 96%). The efficiency of sensitization is caused by the excited state based on ligand-ligand interaction between the Schiff base and hfa ligands in Eu(III) complexes. To fabricate LED devices, the red luminescent [Eu2(hfa)4(OAc)2(salbn)2] was mounted on an InGaN blue LED chip.
  • Pedro Paulo Ferreira da Rosa, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    European Journal of Inorganic Chemistry 2018 (19) 2031 - 2037 1099-0682 2018/05/24 [Refereed][Not invited]
     
    Seven-coordinate TbIII complexes with strong luminescence and thermosensing properties are reported. Mononuclear [Tb(tmh)3(PEB)] [tmh: 2,2,6,6-tetramethyl-3,5-heptanedione, PEB: (diphenylphosphoryl)ethynyl]benzene and dinuclear [Tb2(tmh)6(m-BPEB)] [m-BPEB: 1,3-bis(diphenylphosphoryl)ethynyl]benzene were characterized by single-crystal X-ray analysis. The quantum yields of [Tb(tmh)3(PEB)] and [Tb2(tmh)6(m-BPEB)] were estimated to be 71 and 39 %, respectively. Thermosensing properties are evaluated by temperature-dependent emission lifetime measurements (Arrhenius analysis), which are affected by the presence of ligand-to-ligand charge transfer (LLCT) bands. The LLCT bands are confirmed by DFT calculations.
  • Yasuchika Hasegawa, Shiori Natori, Jun Fukudome, Takashi Nagase, Takashi Kobayashi, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Hiroyoshi Naito
    Journal of Physical Chemistry C 122 (17) 9599 - 9605 1932-7447 2018/05/03 [Refereed][Not invited]
     
    © Copyright 2018 American Chemical Society. Lanthanide coordination polymers with charge combination parts, hole and electron transport units, [Eu(ntfa)3(dppcz)]n and [Eu3(ntfa)9(tpcz)2]n [ntfa = 3-(2-naphthoyl)-1,1,1-trifluoroacetonate, dppcz = 3,6-bis(diphenylphosphoryl)-9-phenylcarbazole), tpcz = 3,6-bis(diphenylphosphoryl)-9-[4-(diphenylphosphoryl)phenyl]carbazole], are reported as an emitting material for organic electroluminescent (EL) devices. The intrinsic emission quantum yields φ4f-4f of [Eu(ntfa)3(dppcz)]n and [Eu3(ntfa)9(tpcz)2]n in the solid state were calculated to be 32% and 45%, respectively. The photosensitized energy-transfer efficiencies ηsens from organic ntfa ligands to luminescent Eu(III) ions in [Eu(ntfa)3(dppcz)]n and [Eu3(ntfa)9(tpcz)2]n were found to be 84% and 39%, respectively. The energy-transfer efficiency ηsens from ntfa to Eu(III) ion is dependent on the network structure in Eu(III) coordination polymers in the solid state. The ηsens values and characteristic structures of Eu(III) coordination polymers are directly linked to maximum luminances and current efficiencies in solid EL devices, respectively. The luminance of an EL device containing [Eu(ntfa)3(dppcz)]n was estimated to be 188 cd/m2 at 15 V, which is greater than that of previously reported EL devices with Eu(III) complexes.
  • Yuichi Kitagawa, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    ChemistrySelect 3 (9) 2646 - 2648 2365-6549 2018/03/07 [Refereed][Not invited]
     
    The photophysical properties of lanthanide(III) complexes depend on the magnitude of orbital mixing between the lanthanide(III) and ligands. Herein, an estimation method of orbital mixing in lanthanide(III) complexes is reported using LnCl3⋅nH2O (Ln=Pr, Gd, Tb) and Ln(tfa)3(H2O)2 (tfa: trifluoroacetylacetonate, Ln=Pr, Gd, and Tb) for the first time. The electronic state properties were assessed from the electronic absorption and magnetic circular dichroism (MCD) spectra. The MCD spectra revealed the energy levels of the spin-allowed and spin-forbidden 4 f–5d transitions of the Tb(III) complex that is hidden by the intense π–π* transition of the ligands. This energy gap corresponds to the exchange splitting energy between the 5d and 4fn−1 electrons, which provides information regarding the orbital mixing between the Tb(III) ion and the ligands.
  • Koji Fushimi, Ryogo Nakagawa
    Corrosion Reviews 36 (1) 3 - 15 0334-6005 2018/02/23 [Refereed][Not invited]
     
    Microelectrochemical approaches using a microcapillary cell (MCC), scanning electrochemical microscopy (SECM), and in situ ellipsomicroscopy for studying heterogeneous passive or corroding surfaces of materials are reviewed. An MCC can be used to investigate the localized behavior of a site of interest on a material by various electrochemical methods, including electrochemical impedance spectroscopy. SECM has often been used for imaging corroding surfaces or passive films on materials. Moreover, the use of a liquid-phase ion gun, a mode of SECM that forms a local aggressive environment at the solution/material interphase, can reveal the depassivation mechanism and kinetics of the surface of a material. The heterogeneous growth or degradation of a thin passive film on a material has been monitored using in situ ellipsomicroscopy, and a depassivation site has been successfully found before a film breakdown is initiated. These microelectrochemical methods are useful for monitoring the heterogeneous distribution of a passive film and for investigating the heterogeneity of the passivity of materials.
  • Kei Yanagisawa, Yuichi Kitagawa, Takayuki Nakanishi, Tomohiro Seki, Koji Fushimi, Hajime Ito, Yasuchika Hasegawa
    Chemistry - A European Journal 24 (8) 1956 - 1961 1521-3765 2018/02/06 [Refereed][Not invited]
     
    Temperature-dependent luminescence of a dinuclear EuIII/TbIII complex with a seven-coordinate structure is demonstrated. The dinuclear complex is composed of two lanthanide ions, six tetramethylheptanedionate ligands, and a bidentate phosphine oxide linker ligand. The dinuclear structure of the complex was characterized by single-crystal XRD. Intrinsic 4f–4f emission quantum yields of the dinuclear EuIII and TbIII complexes were 66 and 61 %, respectively. The luminescence color of the dinuclear EuIII/TbIII complex changed from red to green with increasing temperature. The thermosensing range based on the ratio of luminescence intensity (AEu/ATb) was 100–450 K. The temperature-dependent luminescence is due to the presence of a ligand-to-metal charge-transfer state.
  • Shun Omagari, Takayuki Nakanishi, Yuichi Hirai, Yuichi Kitagawa, Tomohiro Seki, Koji Fushimi, Hajime Ito, Yasuchika Hasegawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY (5) 561 - 567 1434-1948 2018/02 [Refereed][Not invited]
     
    Phonons are important in energy transfer for compensating the energy mismatch between a donor and an acceptor. In inorganic hosts doped with lanthanides, phonon-assisted energy transfer can lead to quenching by a direct transfer of the energy to the phonon mode of the acceptor lanthanide. We demonstrate that this also applies to lanthanide coordination polymers and is the reason for the weak concentration quenching in this type of material. [YbxGd1-x(hfa)(3)dpbp](n) [x = 0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1; hfa: hexafluoroacetylacetonate, dpbp: 4,4'-bis(diphenylphosphoryl)biphenyl] coordination polymers have been synthesized and their photophysical properties investigated. The single-exponential emission lifetimes of Yb3+ gradually decreased with increasing concentration of Yb3+. Qualitative agreement was achieved between the experimental and theoretical lifetimes by using the phonon-assisted energy-transfer-induced quenching model, which indicates that the origin of the concentration quenching in the coordination polymers is phonon-assisted energy transfer.
  • Ohtsuka, T., Fushimi, K.
    Encyclopedia of Interfacial Chemistry: Surface Science and Electrochemistry 2018
  • Koji Fushimi
    SpringerBriefs in Molecular Science 2191-5407 2018
  • Masanori Yamamoto, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    Bulletin of the Chemical Society of Japan 91 (1) 6 - 11 1348-0634 2018 [Refereed][Not invited]
     
    Lanthanide (Ln3+) complexes composed of luminescent Eu3+ complex and joint metal blocks (Al3+, Zn2+ and Pd2+ complexes) are reported. The Eu3+ complexes [Eu(hfa)3- (dppy)2PdCl2]n (Eu-Pd), [Eu(hfa)3(dppy)2ZnCl2]n (Eu-Zn) and [Eu(hfa)3(dppy)4AlCl3]n (Eu-Al) (hfa: hexafluoroacetylacetonato, dppy: 4-pyridyldiphenylphosphine oxide) were synthesized by the complexation of [Eu(hfa)3(H2O)2] with [MCln-(dppy)m] (M = Pd2+, Zn2+ and Al3+). These predicted structures were estimated using single-crystal X-ray structural analyses and DFT calculations. Photophysical properties of these complexes were evaluated based on the emission lifetimes and emission quantum yields. The emission quantum yields are dependent on the moiety of the joint metal blocks. Eu-Al complex shows the largest emission quantum yield (Φff = 72%). In contrast, the emission quantum yield of Eu-Pd is found to be 1.3%. The structures and photophysical properties of Eu3+ complexes linked with joint metal blocks are demonstrated.
  • Yuichi Kitagawa, Fumiya Suzue, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    Dalton Transactions 47 (21) 7327 - 7332 1477-9234 2018 [Refereed][Not invited]
     
    A luminescent Eu(iii) complex with a large electronically isolated aromatic ring system, Eu(hfa)3(DPPTO)2 (where hfa denotes hexafluoroacetylacetonate and DPPTO denotes 2-diphenylphosphoryltriphenylene), is reported. The light-harvesting efficiency of the Eu(iii) complex was assessed from electronic absorption spectra. Luminescence properties were evaluated from luminescence spectra, excitation spectra, luminescence quantum yields, and luminescence lifetimes. A remarkably brilliant luminescence was observed because of the strong light absorption and the high luminescence quantum yield of the Eu(iii) complex. Density functional theory calculations indicated an electronic separation between the energy-donating large π-conjugated orbital and the energy-accepting Eu(iii) orbital. These findings demonstrate that novel Eu(iii) photophysics can be induced by large electronically isolated aromatic ring systems.
  • Yudai Yamamoto, Yuichi Kitagawa, Yasuchika Hasegawa, Koji Fushimi
    Journal of The Electrochemical Society 165 (13) S900 - S906 0013-4651 2018 [Refereed][Not invited]
     
    Hydrogen penetration into iron sheets from a borate buffer solution (pH 8.4) was investigated using a modified Devanathan-Stachurski cell with flow paths. A sinusoidal perturbation method was applied to evaluate the hydrogen-diffusion coefficient D and its dependence on specimen thickness, polarization potential, and electrolyte flow rate. A fast Fourier transform (FFT) technique was employed to achieve automated derivation of the diffusion coefficient with precision and rapid screening of the experimental conditions. The obtained value of D increased with an increase in the specimen thickness or with an increase in the overpotential of the hydrogen evolution reaction, indicating the effect of a surface barrier layer-like oxide film on the hydrogen-entry side. On the other hand, D is not dependent on the electrolyte flow rate in the entry-side cell. From the viewpoint of hydrogen penetration, the properties of the barrier layer are almost immune to the flow rate, though it is affected by the polarization potential. The sinusoidal perturbation method combined with FFT allows the time-dependent evaluation of the hydrogen-penetration behavior in specimens with temporal changes, such as oxide-film formation and corrosion. (c) 2018 The Electrochemical Society.
  • Koji Fushimi, Satoshi Nakatsuji, Jun-Seob Lee, Yuichi Kitagawa, Takayuki Nakanishi, Yasuchika Hasegawa, Kazuhiko Baba, Shiro Tsuri
    Journal of The Electrochemical Society The Electrochemical Society 165 (10) C618 - C623 0013-4651 2018 [Refereed][Not invited]
  • Toru Koizuka, Masanori Yamamoto, Yuichi Kitagawa, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 90 (12) 1287 - 1292 0009-2673 2017/12 [Refereed][Not invited]
     
    Thermostable mononuclear Eu(III) complexes with a pi-expanded system, [Eu(btfa)(3)(DPEPO)] and [Eu(ntfa)(3)(DPEPO)] (DPEPO: bis[2-(diphenylphosphino) phenyl] ether oxide, btfa: benzoyltrifluoroacetonate, ntfa: 3-(2-naphthoyl)-1,1,1-trifluoro-acetonate), are reported. Decomposition temperature (dp) of [Eu(btfa)(3)(DPEPO)] and that of [Eu(ntfa) 3(DPEPO)] are estimated to be 320 degrees C and 318 degrees C, respectively. These values are higher than that of the previous [Eu(hfa)(3)(DPEPO)] (hfa: hexa-fluoroacetylacetonate, dp = 228 degrees C). The photosensitized emission quantum yield Phi(pi-pi*) and photosensitized energy transfer efficiency eta(sens) of [Eu(ntfa)(3)(DPEPO)] (eta(pi-pi*) = 45%, eta(sens) = 77%) are larger than those of [Eu(btfa)(3)(DPEPO)] (Phi(pi-pi*) = 38%, eta(sens) = 55%). The thermostable Eu(III) complex with a p-expanded system is expected to be useful for fabrication of LED devices.
  • Yuichi Hirai, Pedro Paulo Ferreira da Rosa, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Yasuchika Hasegawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 90 (3) 322 - 326 0009-2673 2017/03 [Refereed][Not invited]
     
    The glass-transition properties and temperature-sensitive luminescence of lanthanide (Ln(III)) coordination compounds are reported. The glass formability was systematically provided by incorporation of bent-angled phosphine oxide (2,5-bis(diphenylphosphorylethynyl)thiophene: dpet, 2,7-bis(diphenylphosphorylethynyl) naphthalene: dpen, 1,3-bis(diphenylphosphorylethynyl) benzene: m-dpeb) ligands with thienyl, naphthyl, phenyl cores, and ethynyl groups. The glass-transition points were clearly identified for all Ln(III) coordination compounds (T-g = 65-87 degrees C). The Tb(III)/Eu(III) mixed coordination glass [Tb,Eu(hfa)(3)(m-dpeb)](3) (hfa: hexafluoroacetylacetonate) also showed green, yellow, orange, and red photoluminescence depending on temperature.
  • Time-dependent measurement of hydrogen penetration in ferric metal materials
    Yudai Yamamoto, Yuichi Kitagawa, Takayuki Nakanishi, Yasuchika Hasegawa, Koji Fushimi
    EUROCORR 2017 - The Annual Congress of the European Federation of Corrosion, 20th International Corrosion Congress and Process Safety Congress 2017 2017 
    Hydrogen diffusion in metal sheet has conventionally been investigated using a double electrochemical cell, so-called Devanathan-Stachurski (DS) cell. The authors reported that, when a flow-rate of electrolyte in an entry side cell is sinusoidally perturbed, an entry side current and an exit side current flow with sinusoidal waveforms and the latter shows a latency of phase shift θ depending on the alternation frequency, specimen thickness and hydrogen diffusion coefficient DH in the sheet. In this study, the emphasis was put on a time-dependence of θ. Utilization of fast-Fourier-transform enabled the evaluation of θ in real-time. Hydrogen penetration measurement under potentiostatic polarization with sinusoidal flow-rate perturbation was applied to a ferric metal sheet. Under a standard ambient condition, the value of θ showed a circadian change, which was similar to the change in temperature of the experimental system. However, an Arrhenius-type analysis for the thermo-response of θ resulted in abnormally large values of activation energy and maximal diffusion coefficient, suggesting that the value of θ is dependent on not only temperature but also other parameters.
  • Self-healing ability of pH sensitive microcapsules on aluminum alloy
    Takeshi Matuda, Kiran B. Kashi, Koji Fushimi, Victoria J. Gelling
    EUROCORR 2017 - The Annual Congress of the European Federation of Corrosion, 20th International Corrosion Congress and Process Safety Congress 2017 2017 
    The self-healing ability of pH sensitive microcapsules (pH-MC) on an aluminum alloy was investigated. Nitrate salts including magnesium nitrate and aluminum nitrate were encapsulated in pH-MC by water-in-oil emulsion polymerization. In separate experiments, magnesium nitrate was encapsulated as a corrosion inhibitor for the aluminum alloy, and aluminum nitrate was chosen to investigate the release property due its amphoteric nature. Immersion tests demonstrated that the pH-MC was sensitive to acidic and basic environments and was inactive in a neutral environment. Scribe creep of an epoxy coating on the aluminum alloy was improved by adding pH-MC containing magnesium nitrate to the coating matrix.
  • Non-uniform distribution of passive film formed on carbon steel
    Koji Fushimi, Ryogo Nakagawa, Yuichi Kitagawa, Takayuki Nakanishi, Yasuchika Hasegawa
    EUROCORR 2017 - The Annual Congress of the European Federation of Corrosion, 20th International Corrosion Congress and Process Safety Congress 2017 2017 
    Passive film of S45C carbon steel formed in pH 8.4 boric acid-borate buffer solution was investigated by using scanning electrochemical microscopy (SECM). Passivity-maintaining current of the carbon steel was about 3 times as large as that of pure iron. Current of electron-transfer reaction (ETR) of redox mediator through the passive film was strongly dependent on metallographic structure of the carbon steel. For example, the passive film formed on perlite eutectic phase in the carbon steel allowed larger ETR current than that formed on primary phase ferrite. Raman spectroscopy revealed that the surface of carbon steel was covered with non-uniform magnetite and amorphous carbon. It was suggested that cementite in the perlite affected not only the formation of oxide but also the semi-conductive property of the film.
  • Hirai, Yuichi, Nakanishi, Takayuki, Kitagawa, Yuichi, Fushimi, Koji, Seki, Tomohiro, Ito, Hajime, Hasegawa, Yasuchika
    Angewandte Chemie-International Edition 56 (25) 7171 - 7175 1433-7851 2017 [Refereed][Not invited]
  • Takabatake, Y., Kitagawa, Y., Nakanishi, T., Hasegawa, Y., Fushimi, K.
    Journal of the Electrochemical Society 164 (7) C349 - C355 2017 [Refereed][Not invited]
  • Kitagawa, Yuichi, Ohno, Ryohsuke, Nakanishi, Takayuki, Fushimi, Koji, Hasegawa, Yasuchika
    Photochemical & Photobiological Sciences 16 (5) 683 - 689 1474-905X 2017 [Refereed][Not invited]
  • Lee, Jun-Seob, Kawano, Takashi, Ishii, Tomohiro, Kitagawa, Yuichi, Nakanishi, Takayuki, Hasegawa, Yasuchika, Fushimi, Koji
    Journal of the Electrochemical Society 164 (2) C1 - C7 0013-4651 2017 [Refereed][Not invited]
  • Yanagisawa, Kei, Kitagawa, Yuichi, Nakanishi, Takayuki, Akama, Tomoko, Kobayashi, Masato, Seki, Tomohiro, Fushimi, Koji, Ito, Hajime, Taketsugu, Tetsuya, Hasegawa, Yasuchika
    European Journal of Inorganic Chemistry (32) 3843 - 3848 1434-1948 2017 [Refereed][Not invited]
     
    Luminescent mononuclear seven-coordinate Eu-III complexes, with monocapped-octahedral (point group: C-3v), monocapped-trigonal-prismatic (C-2v), and pentagonal-bipyramidal (D-5h) coordination structures, are reported. The complexes each consist of a Eu-III ion, three tetramethylheptanedionates, and a phosphine oxide derivative. Controlling steric hindrance by means of introducing methyl groups into the phosphine oxide ligands resulted in the formation of three types of coordination polyhedral structures. The coordination geometrical structures of the Eu-III complexes were evaluated by single-crystal X-ray diffraction analysis and shape-factor calculations. The radiative rate constant of the Eu-III complex with a monocapped-octahedral structure was larger than those with monocapped-trigonal-prismatic and pentagonal-bipyramidal structures. Characteristic photophysical properties of the seven-coordinate Eu-III complexes are discussed with TD-DFT calculations and Arrhenius analysis of the ligand-to-metal charge transfer.
  • Kitagawa, Yuichi, Yachi, Ryuto, Nakanishi, Takayuki, Fushimi, Koji, Hasegawa, Yasuchika
    Journal of Physical Chemistry a 121 (24) 4613 - 4618 1089-5639 2017 [Refereed][Not invited]
  • Hasegawa, Yasuchika, Tateno, Shiori, Yamamoto, Masanori, Nakanishi, Takayuki, Kitagawa, Yuichi, Seki, Tomohiro, Ito, Hajime, Fushimi, Koji
    Chemistry-a European Journal 23 (11) 2666 - 2672 0947-6539 2017 [Refereed][Not invited]
  • Koiso, Naoyuki, Kitagawa, Yuichi, Nakanishi, Takayuki, Fushimi, Koji, Hasegawa, Yasuchika
    Inorganic Chemistry 56 (10) 5741 - 5747 0020-1669 2017 [Refereed][Not invited]
  • Jun-Seob Lee, Yuichi Kitagawa, Takayuki Nakanishi, Yasuchika Hasegawa, Koji Fushimi
    ELECTROCHIMICA ACTA 220 304 - 311 0013-4686 2016/12 [Refereed][Not invited]
     
    The passivity of type 316L stainless steel was studied in a pH 8.4 boric acid-borate buffer solution containing hydrogen sulfide ions (HS-) by using a local anion-generating system. During potentiostatic polarization of the stainless steel at a primary passive potential of 0.4V(SSE) and at a secondary passive potential of 0.9 V-SSE in solutions with and without HS-, the current density flowing for passive film formation was increased by the presence of HS- at both potentials, while 15 Hz impedance at 0.9 V-SSE in the solution with HS- was larger than that in the solution without HS-. It was thought that the presence of HS- in the solution during film formation made the film less resistive and affected the film capacitance depending on the polarization potential. X-ray photoelectron spectroscopy (XPS) showed an increase in metal cation and oxygen anion vacancies in the passive film formed at the primary passive state in the solution containing HS-. Auger electron spectroscopy (AES) and Raman spectroscopy revealed that a sulfide layer was deposited on the stainless steel surface that was oxidized at the secondary passive state in the solution containing HS-. It is thought that application of a high potential changes the passivity of the stainless steel surface in the solution containing HS-. (C) 2016 Elsevier Ltd. All rights reserved.
  • Toshiaki Ohtsuka, Koji Fushimi
    ELECTROCHEMISTRY 84 (11) 826 - 832 1344-3542 2016/11 [Refereed][Not invited]
     
    In-situ optical detection of the passive oxide films on iron and titanium was reviewed. The optical techniques such as ellipsometry (i.e., reflection of polarized light), Raman spectroscopy, and potential modulation reflectance (PMR) have been successfully applied to the detection in thickness, composition, and semiconducting property, respectively, of the thin passive oxides under the in-situ condition. The growth mechanism of the passive oxide has been discussed from the precise measurement of thickness as a function of potential and time by a three parameter ellipsometry. From the in-situ Raman spectra, the composition of the passive oxide has been estimated to be Fe3O4-gamma-Fe2O3 for iron and anatase TiO2 for titanium. From PMR, the Mott-Schottky type plot could be drawn in the passive oxide on iron, which indicates that the formation of the space charge layer can be optically seen. From the PMR spectra, one has evaluated light-absorption edge that may correspond to a band-gap energy between the valence and conduction band. (C) The Electrochemical Society of Japan, All rights reserved.
  • Yuichi Hirai, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Tomohiro Seki, Hajime Ito, Yasuchika Hasegawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 (39) 12059 - 12062 1433-7851 2016/09 [Refereed][Not invited]
     
    Novel Eu-III coordination polymers [Eu(hfa)(3)(dpt)](n)(dpt: 2,5-bis(diphenylphosphoryl)thiophene) and [Eu(hfa)(3)(dpedot)](n) (dpedot: 2,5-bis(diphenylphosphoryl)ethylenedioxythiophene) with hydrogen-bonded zipper structures are reported. The coordination polymers are composed of Eu-III ions, hexafluoroacetylacetonato ligands, and thiophene-based phosphine oxide bridges. The zig-zag orientation of single polymer chains induced the formation of densely packed coordination structures with multiple intermolecular interactions, resulting in thermal stability above 300 degrees C. They exhibit a high intrinsic emission quantum yield (ca. 80%) due to their asymmetrical and low-vibrational coordination structures around Eu-III ions. Furthermore, the characteristic alternative orientation of substituents also contributes to the dramatically high ligand-to-metal energy transfer efficiencies of up to 80% in the solid state.
  • Satoshi Wada, Yuichi Kitagawa, Takayuki Nakanishi, Koji Fushimi, Yasuhiro Morisaki, Koji Fujita, Katsuaki Konishi, Katsuhisa Tanaka, Yoshiki Chujo, Yasuchika Hasegawa
    NPG Asia Materials 8 (3) 1884-4057 2016/03/25 [Refereed][Not invited]
     
    The chiral nonanuclear Tb(III) clusters [Tb9(sal-(R)-Bt)16(μ-OH)10]+[NO3]. (Tb-(R)-Bt: sal-(R)-Bt=(R)-2-butyl salicylate) and [Tb9 (sal-(S)-Bt)16(μ-OH)10]+[NO3]. (Tb-(S)-Bt: sal-(S)-Bt=(S)-2-butyl salicylate) were found to exhibit a unique magneto-optical property: the Faraday effect. The clusters were composed of 9 Tb(III) ions bridged by 10 μ-OHs and 16 chiral salicylic acid esters. The Faraday rotation angle of Tb-(R)-Bt was greater than that of Tb-(S)-Bt, indicating that the Faraday effect was affected by the chirality of the Tb(III) clusters. The chiroptical properties of the Tb(III) clusters were estimated using circular dichroism and circularly polarized luminescence. In this study, a new finding concerning chiral magneto-optical properties was investigated.
  • Yuichi Kitagawa, Satoshi Wada, Kei Yanagisawa, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    CHEMPHYSCHEM 17 (6) 845 - 849 1439-4235 2016/03 [Refereed][Not invited]
     
    Magneto optical devices based on the Faraday effects of lanthanide ion have attracted much attention. Recently, large Faraday effects were found in nano-sized multinuclear lanthanide complexes. In this study, the Faraday rotation intensities were estimated for lanthanide nitrates [Ln(III)(NO3)(3)nH(2)O: Ln=Pr, Nd, Sm, Eu, Tb, Dy, Ho, Er, Tm) and Eu-III complexes with -diketone ligands, using magnetic circular dichroism. Eu ions exhibit the largest Faraday rotation intensity for (F0D1)-F-7-D-5 transitions, and high-symmetry fields around the Eu ions induce larger Faraday effects. The molecular design for the enhancement of Faraday effects in lanthanide complexes is discussed.
  • Yasuchika Hasegawa, Takeshi Sugawara, Takayuki Nakanishi, Yuichi Kitagawa, Makoto Takada, Akitsugu Niwa, Hiroyoshi Naito, Koji Fushimi
    CHEMPLUSCHEM 81 (2) 187 - 193 2192-6506 2016/02 [Refereed][Not invited]
     
    Luminescent thin films composed of thermostable lanthanide coordination polymers on glass electrodes were prepared using a novel combination of micelle reactions and electrochemical deposition techniques. The micelle-encapsulated luminescent polymers were obtained by the polymerization of [Eu(hfa)(3)] (hfa=hexafluoroacetylacetonate) with bridging phosphine oxide ligands in micelles using a redox-active ferrocenyl-containing surfactant in water. Films were electrochemically deposited on indium tin oxide coated glass electrodes by potentiostatic polarization of micelle-encapsulated Eu-III coordination polymers. The luminescence properties of the electrochemically deposited films were characterized by measuring their emission spectra, emission lifetimes and emission quantum yields.
  • Y. Kitagawa, R. Ohno, T. Nakanishi, K. Fushimia, Y. Hasegawa
    PHYSICAL CHEMISTRY CHEMICAL PHYSICS 18 (45) 31012 - 31016 1463-9076 2016 [Refereed][Not invited]
     
    Visible luminescence europium(III) complexes with large pi-conjugated systems were theoretically and experimentally studied. A strategy for extending the pi-conjugation of a ligand for use with europium(III) ions was found on the basis of fragment molecular orbital and density functional theory calculations. Using this method, a novel europium complex was designed and synthesized. Its excited state properties were assessed from the luminescence spectrum, excitation spectrum, luminescence lifetime, and luminescence quantum yield. In this study, the novel photophysics induced by the combination of visible luminescent europium(III) ions and large pi-conjugated systems are described.
  • Takabatake, Y., Kitagawa, Y., Nakanishi, T., Hasegawa, Y., Fushimi, K.
    Journal of the Electrochemical Society 163 (14) C815 - C822 2016 [Refereed][Not invited]
  • Fushimi, K., Kurauchi, K., Nakanishi, T., Hasegawa, Y., Ueda, M., Ohtsuka, T.
    2016 [Refereed][Not invited]
  • Yamamoto, Yudai, Kitagawa, Yuichi, Nakanishi, Takayuki, Hasegawa, Yasuchika, Fushimi, Koji
    Isij International 56 (3) 472 - 477 0915-1559 2016 [Refereed][Not invited]
     
    Numerical calculation for the diffusion problem of hydrogen absorbed in a steel sheet during hydrogen permeation measurement using a double electrochemical cell was carried out. The finite element method (FEM) was applied to obtain the concentration distribution of hydrogen expressed by one- or two-dimensional Fick's laws in the sheet, assuming that hydrogen concentration at the hydrogen entry interface was perturbed sinusoidally and both the hydrogen entry and exit reactions were in a mass-transport controlled process. From a comparison with experimental results reported previously, in which a phase shift from entry current to exit current waves observed on a single grain of the specimen sheet was at least two-times larger than that on two grains, it was estimated that the diffusion coefficient at a grain boundary located between two grains was five orders in magnitude larger than that on a single grain.
  • Nakajima, Ayako, Nakanishi, Takayuki, Kitagawa, Yuichi, Seki, Tomohiro, Ito, Hajime, Fushimi, Koji, Hasegawa, Yasuchika
    Scientific Reports 6 2045-2322 2016 [Refereed][Not invited]
  • Ayako Nakajima, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Yasuchika Hasegawa
    SENSORS AND MATERIALS 28 (8) 845 - 850 0914-4935 2016 [Refereed][Not invited]
     
    A novel thermosensitive luminescent lanthanide coordination compound was successfully synthesized. The coordination compound consists of Eu, Tb, and two photosensitized organic ligands [hexafluoroacetylacetone (hfa) and tris(p-carboxyphenyl) phosphine oxide (TPO)]. The Eu/Tb mixed coordination compound shows different luminescent colors depending on the temperature (green luminescence at 300 K and yellow luminescence at 450 K). In this study, emission spectra were measured at 300, 350, 400, and 400 K, and the ratio of (Eu/Tb) luminescence intensity at each temperature was estimated. The temperature-dependent luminescence is caused by the two differentially photosensitized organic ligands, hfa and TPO. These results may lead to the development of novel thermosensing devices using lanthanide luminescence.
  • Fushimi, Koji, Jin, Misako, Kitagawa, Yuichi, Nakanishi, Takayuki, Hasegawa, Yasuchika
    Isij International 56 (3) 431 - 435 0915-1559 2016 [Refereed][Not invited]
  • Omagari, Shun, Nakanishi, Takayuki, Kitagawa, Yuichi, Seki, Tomohiro, Fushimi, Koji, Ito, Hajime, Meijerink, Andries, Hasegawa, Yasuchika
    Scientific Reports 6 2045-2322 2016 [Refereed][Not invited]
  • Akira Kawashima, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fushimi, Yasuchika Hasegawa
    PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE 213 (1) 178 - 182 1862-6300 2016/01 [Refereed][Not invited]
     
    Effective photoswitchable europium sulfide nanocrystals with gold nanoparticles using dithiol (DDT: 1,10-decanedithiol) joint molecules, EuS-Au nanosystems, are demonstrated. The TEM image indicates the formation of EuS-Au nanosystems composed of cube-shaped EuS nanocrystals and spherical Au nanoparticles. Under visible-light irradiation, a drastic change of absorption band of EuS-Au nanosystems at around 600 nm was observed. The Faraday effects of EuS-Au nanosystems were estimated using magnetic circular dichroism (MCD) measurements. The effective change of the MCD spectra of EuS-Au nanosystems under visible-light irradiation was successfully observed at around 670 nm for the first time. The effective reversible changes in MCD spectra with the alternative irradiation cycles of visible light (>440 nm) and dark are also presented. The decrease rate of rotation angle at 670 nm of EuS-Au nanosystems is larger than that of absorbance. These results indicate that the effective change of MCD spectra of EuS-Au nanosystems would be dominated not only by a drastic change of absorption band related to enhanced LSPR of Au nanoparticles but also by specific interaction between EuS and Au in nanosystem under irradiation. (C) 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
  • Yamamoto, M., Nakanishi, T., Kitagawa, Y., Fushimi, K., Hasegawa, Y.
    Materials Letters 167 183 - 187 0167-577X 2016 [Refereed][Not invited]
     
    A structural design of new luminescent lanthanide coordination polymers composed of Eu3+ complex and Zn2+ complexes are introduced. The Eu3+ coordination polymer [Eu(hfa)(3)(dppy)(2)ZnCI2](n), (Eu-Zn) (hfa: hexafluoroacetylacetonato, dppy: 4-pyridyldiphenylphosphane oxide) were synthesized by the complexation of Eu(hfa)(3)(H2O)(2) with ZnCl2(dppy)(2). The structure was characterized using XRD and TG-DTA. The photophysical properties were estimated using the emission spectra, the emission lifetimes, and the emission quantum yields. The emission quantum yields are larger then that of precursor Eu (hfa)(3)(H2O)(2). The emission quantum yield of Eu-Zn was found to be 59%. The preparations, structures and photophysical properties of Eu-Zn are demonstrated as a new luminescent Eu3+ coordination polymer for the first time. (C) 2015 Elsevier B.V. All rights reserved.
  • Hiromitsu Onodera, Yuichi Kitagawa, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    JOURNAL OF MATERIALS CHEMISTRY C 4 (1) 75 - 81 2050-7526 2016 [Refereed][Not invited]
     
    Acid-protected Eu(III) coordination nanoparticles composed of Eu(III) complexes, joint ligands, terminate ligands and a protection layer are reported. The prepared acid-protected Eu(III) coordination nanoparticles [Eu(hfa)(3)(dpbp)(x)(SDPO)(y)](n)-PS and Eu(III) coordination nanoparticles [Eu(hfa)(3)(dpbp)(x)(SDPO)(y)](n) were characterized using ESI-mass spectrometry (ESI-MS), X-ray diffraction (XRD), scanning electron microscopy (SEM), dynamic light scattering (DLS) measurements, and thermogravimetric analysis (TGA). [Eu(hfa)(3)(dpbp)(x)(SDPO)(y)](n)-PS shows an effective acid-resistance property based on the polystyrene layer on its nanoparticle surface. The emission intensity is retained under 3000 s in an acidic condition (pH = 0.92). In this study, acidprotected Eu(III) coordination nanoparticles are demonstrated.
  • Hiromitsu Onodera, Ayako Nakajima, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    JOURNAL OF ALLOYS AND COMPOUNDS 648 651 - 657 0925-8388 2015/11 [Refereed][Not invited]
     
    The thermostable Eu(III)-doped nanorod aggregates composed of luminescent Eu(III) complexes and diphenylphosphinic acids (DPP) are reported. Prepared Eu(III)-nanorod aggregates [Eu(hfa)(x)(TPPO)(y)(DPP)(z)](n) (hfa: hexafluoroacetylacetionate, TPPO: triphenylphosphine oxide), Eu(III)-nanoparticle aggregates [Eu(hfa) x(DPP) y] n, and standard Eu(III)-nanoparticles [Eu(DPP)(x)](n) were characterized using X-ray diffraction (XRD) and transmission electron microscopy (TEM) measurements. The decomposition temperatures of [Eu(hfa)(x)(DPP)(y)](n) and [Eu(hfa)(x)(TPPO)(y)(DPP)(z)](n) for thermogravimetric analysis (TGA) were found to be over > 500 degrees C. Photosensitized luminescence was successfully observed for Eu(III)-nanorod and Eu(III)-nanoparticle aggregates excited at the specific pi-pi* transition band for organic hfa ligands (lambda = 340 nm), which is similar to the inter-ligand charge transfer (ILCT) band in the solid-state, were successfully observed. The photosensitized energy transfer efficiency of Eu(III)-nanorod aggregates of [Eu(hfa)(x)(TPPO)(y)(DPP)(z)](n) was estimated to be 91%. In this study, thermostable Eu(III)-nanorod aggregate luminophore composed of Eu(III) complexes and DPP joint compounds are demonstrated. (C) 2015 Elsevier B.V. All rights reserved.
  • Kei Yanagisawa, Takayuki Nakanishi, Yuichi Kitagawa, Tomohiro Seki, Tomoko Akama, Masato Kobayashi, Tetsuya Taketsugu, Hajime Ito, Koji Fushimi, Yasuchika Hasegawa
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2015 (28) 4769 - 4774 1434-1948 2015/10 [Refereed][Not invited]
     
    Enhanced luminescence properties of mononuclear lanthanide complexes with asymmetric seven-coordination structures are reported for the first time. The lanthanide complexes are composed of a lanthanide ion (Eu-III or Tb-III), three tetramethyl heptanedionato ligands, and one triphenylphosphine oxide ligand. The coordination geometries of the lanthanide complexes have been evaluated by using single-crystal X-ray analyses and shape-measurement calculations. The complexes are categorized to be seven-coordinate monocapped octahedral structures (point group C-3v). The seven-coordinate lanthanide complexes show high intrinsic emission quantum yields, extra-large radiative rate constants, and unexpected small nonradiative rate constants. The brilliant luminescence properties have been elucidated in terms of the asymmetric coordination geometry and small vibrational quanta related to thermal relaxation.
  • Akira Kawashima, Takayuki Nakanishi, Yuichi Kitagawa, Koji Fujita, Katsuhisa Tanaka, Koji Fushimi, Mohammad A. Malik, Paul O'Brien, Yasuchika Hasegawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 88 (10) 1453 - 1458 0009-2673 2015/10 [Refereed][Not invited]
     
    Novel terbium nanoparticles (TbX: terbium oxide (Tb2O3), terbium fluoride (TbF3), and terbium oxyfluoride (TbOF)) have been prepared and their magneto-optical properties reported. The TbX nanoparticles were synthesized by the thermolysis of Tb(III) complexes, used as single-source precursors, in oleylamine. The temperature used for the decomposition was estimated from using the thermogravimetric analysis (TGA) measurements. The as-prepared TbX nanoparticles were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), energy-dispersive X-ray spectrometry (EDS), and X-ray photoelectron spectroscopy (XPS). Large Faraday rotations were observed from poly(methyl methacrylate) (PMMA) thin films containing TbX nanoparticles under magnetic field (15000 Oe). TbX nanoparticles with magneto-optical properties have been prepared for the first time.
  • Yasuchika Hasegawa, Nao Sato, Yuichi Hirai, Takayuki Nakanishi, Yuichi Kitagawa, Atsushi Kobayashi, Masako Kato, Tomohiro Seki, Hajime Ito, Koji Fushimi
    JOURNAL OF PHYSICAL CHEMISTRY A 119 (20) 4825 - 4833 1089-5639 2015/05 [Refereed][Not invited]
     
    Enhanced luminescence of a lanthanide complex with dynamic polarization of the excited state and molecular motion is introduced. The luminescent lanthanide complex is composed of one Eu(hfa)(3) (hfa, hexafluoroacetylacetonate) and two phosphine oxide ligands with ruthenocenyl units Rc, [Eu(hfa)(3)(RcPO)(2)] (RcPO = diphenylphosphorylruthenocene). The ruthenocenyl units in the phosphine oxide ligands play an important role of switching for dynamic molecular polarization and motion in liquid media. The oxidation states of the ruthenocenyl unit (Rc(1+)/Rc(1+)) are controlled by potentiostatic polarization. Eu(III) complexes attached with bidentate phosphine oxide ligands containing ruthenocenyl units, [Eu(hfa)(3)(RcBPO)] (RcBPO = 1,1'-bis(diphenylphosphoryl)ruthenocene), and with bidentate phosphine oxide ligands, [Eu(hfa)(3)(BIPHEPO)] (BIPHEPO =1,1'-biphenyl-2,2'-diylbis(diphenylphosphine oxide), were also prepared as references. The coordination structures and electrochemical properties were analyzed using single crystal X-ray analysis, cyclic voltammetry, and absorption spectroscopy measurements. The luminescence properties were estimated using an optoelectrochemical cell. Under potentiostatic polarization, a significant enhancement of luminescence was successfully observed for [Eu(hfa)(3)(RcPO)(2)], while no spectral change was observed for [Eu(hfa)(3)(RcBPO)]. In this study, the remarkable enhanced luminescence phenomena of Eu(III) complex based on the dynamic molecular motion under potentiostatic polarization have been performed.
  • Shun Omagari, Takayuki Nakanishi, Tomohiro Seki, Yuichi Kitagawa, Yumie Takahata, Koji Fushimi, Hajime Ito, Yasuchika Hasegawa
    JOURNAL OF PHYSICAL CHEMISTRY A 119 (10) 1943 - 1947 1089-5639 2015/03 [Refereed][Not invited]
     
    The photophysical properties of the novel nonanuclear Tb(III) clusters Tb-L1 and Tb-L2 involving the ligands methyl 4-methylsalicylate (L1) and methyl 5-methylsalicylate (L2) are reported. The position of the methyl group has an effect on their photophysical properties. The prepared nonanuclear Tb(III) clusters were identified by fast atom bombardment mass spectrometry and powder X-ray diffraction. Characteristic photophysical properties, including photoluminescence spectra, emission lifetimes, and emission quantum yields, were determined. The emission quantum yield of Tb-L1 (Phi(pi pi)* = 31%) was found to be 13 times larger than that of Tb-L2 (Phi(pi pi)* = 2.4%). The photophysical characterization and DFT calculations reveal the effect of the methyl group on the electronic structure of methylsalicylate ligand. In this study, the photophysical properties of the nonanuclear Tb(III) clusters are discussed in relation to the methyl group on the aromatic ring of the methylsalicylate ligand.
  • Hydrodynamic effect of entry side cell on hydrogen permeation into steel sheet
    K. Fushimi, M. Jin, Y. Yamamoto, Y. Kitagawa, T. Nakanishi, Y. Hasegawa
    European Corrosion Congress, EUROCORR 2015 1 548 - 551 2015 
    Devanathan-Stachurski (DS) double electrochemical cell for measurement of hydrogen-permeation into a steel sheet was extended to an electrolyte-flowing design. Increase in flow rate of electrolyte in a hydrogen-entry side cell induced an increase in hydrogen-evolution current at the entry side electrode and a decrease in hydrogen-detection current at the hydrogen-exit side electrode. Hydrogen-permeation was actualized by a sinusoidal perturbation of the entry-flow rate. The hydrogen-permeation response, i.e., phase shift of the detection current from the evolution current, was proportional to the square root of flow rate frequency and was dependent on the sheet thickness.
  • H. Habazaki, M. Uemura, K. Fushimi, E. Tsuji, Y. Aoki, S. Nagata
    Journal of The Surface Finishing Society Japan 一般社団法人 表面技術協会 66 (12) 670 - 672 0915-1869 2015 [Refereed][Not invited]
  • Hirai, Y., Nakanishi, T., Kitagawa, Y., Fushimi, K., Seki, T., Ito, H., Fueno, H., Tanaka, K., Satoh, T., Hasegawa, Y.
    Inorganic Chemistry 54 (9) 4364 - 4370 2015 [Refereed][Not invited]
  • Takashi Kawano, Tomohiro Ishii, Hiroshi Kajiyama, Mitsuo Kimura, Koji Fushimi
    Zairyo to Kankyo/ Corrosion Engineering 公益社団法人 腐食防食学会 64 (12) 552 - 557 1881-9664 2015 [Refereed][Not invited]
     
    Deterioration mechanism of corrosion resistance at heat-tinted zone of stainless steel weldment was studied. Local electrochemical measurements with micro capillary cell and surface analyses at small regions were conducted to correlate local variation in corrosion behavior and surface structure. Depletion of the Cr content at the substrate surface and formation of an Fe rich oxide layer on the surface were confirmed, although their distances from the welding bead were not identical. It was also revealed that the corrosion behaviors at the area with the Cr depletion and the area with the Fe rich oxide layer were different. The Cr depletion led to lowering of pitting potential due to the activation of substrate steel whereas the Fe rich oxide layer led to preferential rusting in the cyclic corrosion test due to deterioration of the surface protective layer.
  • Jun-Seob Lee, Yuichi Kitagawa, Takayuki Nakanishi, Yasuchika Hasegawa, Koji Fushimi
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 162 (14) C685 - C692 0013-4651 2015 [Refereed][Not invited]
     
    The effect of hydrogen sulfide ions (HS-) on the passivity of type 316L stainless steel was investigated in pH 8.4 boric acid-borate buffer solution. Galvanostatic polarization of a silver microelectrode covered with Ag2S generated both OH- and HS- above the stainless steel surface. During potentiostatic polarization of the stainless steel, the passivity-maintaining current density increased with increase in the concentration of HS- in the vicinity of the surface. The impedance of the stainless steel at a constant frequency decreased during polarization in the presence of HS-, while it was sustained after dilution of HS-. Electrochemical impedance spectroscopy (EIS), Mott-Schottky (M-S) analysis and scanning electrochemical microscopy (SECM) showed that a defective and n-type semiconductive passive film was formed in the solution containing HS-. Auger electron spectroscopy (AES) revealed that metal cations and oxygen vacancies in the passive film on the stainless steel increased when it was formed in a HS- -conoining solution. The series of changes in passive film properties is thought to be due to adsorption of HS- on the film surface during the polarization. (C) The Author(s) 2015. Published by ECS. This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License (CC BY, http://creativecommons.org/licensestby/4.0/), which permits unrestricted reuse of the work in any medium, provided the original work is properly cited. All rights reserved.
  • Mari Miyano, Takayuki Nakanishi, Satoshi Wada, Yuichi Kitagawa, Akira Kawashima, Koji Fushimi, Yasuhiro Morisaki, Yoshiki Chujo, Yasuchika Hasegawa
    JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY 28 (2) 255 - 260 0914-9244 2015 [Refereed][Not invited]
     
    Active surface of luminescent silicon nanoparticles was terminated by the photochemical reaction of chiral molecules, (S)- or (R)-5-allyl-2-oxabicyclo[3,3,0]oct-8-ene ((S) - or (R) - AOBE) under UV light. The particle size and shapes were characterized using Transmission Electron Microscope (TEM). The average particle size was found to be 5.7 nm. Circular dichroism (CD) signals with large dissymmetry factors from silicon nanoparticles terminated with (S) - and (R) - AOBE were observed at around 300 nm and 500 nm, which were much larger than those of (S)- and (R)-AOBE molecules. The silicon nanoparticles covered with (S)- or (R)-AOBE provided red luminescence based on the indirect electronic transition. Effective circular polarized luminescence (CPL) was not observed from indirect transition band.
  • Hiromitsu Onodera, Ayako Nakajima, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    e-Journal of Surface Science and Nanotechnology 13 219 - 222 1348-0391 2015 [Refereed][Not invited]
     
    The luminescent nanoparticles with Eu(III) ions are reported. Standard nanoparticles are prepared by the reaction of europium chloride with dpp (diphenylphospinic acid) joint ligands. The size-controlled nanoparticles are synthesized by the reaction of Eu(hfa)< inf> 3< /inf> (H< inf> 2< /inf> O)< inf> 2< /inf> (hfa: hexafluoroacetylacetonate) with bidentate dpbp ligands (dpbp: 4,4′-bis(diphenylphosphoryl)biphenyl) and monodentate ligands (TPPO: triphenylphosphine oxide). Their particle sizes were characterized using TEM and dynamic light scattering (DLS) measurements. Their luminescence properties were estimated by the emission spectra and lifetimes.
  • Onodera Hiromitsu, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 87 (12) 1386 - 1390 0009-2673 2014/12 [Refereed][Not invited]
     
    Strong luminescent nanoparticles composed of lanthanoid coordination polymers using micelle reaction techniques, lanthanoid coordination nanoparticles, are reported. Size of the nanoparticles estimated using dynamic light-scattering measurements were found to be approximately 66 urn. Lanthanoid coordination nanoparticles were characterized using ESI-MS spectrometry, XRD measurements, and thermogravimetric analyses (TGA). Emission properties of lanthanoid coordination nanoparticles were estimated using emission spectra and emission lifetimes. These results indicate that nanoparticles composed of lanthanoid coordination polymers show effective luminescent properties and thermal stability such as bulk powders of lanthanoid coordination polymers.
  • Jun-Seob Lee, Koji Fushimi, Takayuki Nakanishi, Yasuchika Hasegawa, Yong-Soo Park
    CORROSION SCIENCE 89 111 - 117 0010-938X 2014/12 [Refereed][Not invited]
     
    Corrosion behaviour of super duplex stainless steel (SDSS) in acidic chloride solution was investigated electrochemically. Potentiostatic polarisations of SDSS at -0.377 and -0.447 V-SHE resulted in selective dissolution of gamma- and alpha-phases, respectively, and were utilized for fabricating single-phase electrodes. Potentiodynamic polarisation curve of SDSS could be calculated from those of single-phase electrodes. The higher corrosion current density and less noble corrosion potential of alpha-phase characterised by galvanic connection with gamma-phase indicated that alpha- and gamma-phases were functioned as the anode and the cathode, respectively, in the corrosion of SDSS. (C) 2014 Elsevier Ltd. All rights reserved.
  • K. Fushimi, K. Kurauchi, Y. Yamamoto, T. Nakanishi, Y. Hasegawa, T. Ohtsuka
    ELECTROCHIMICA ACTA 144 56 - 63 0013-4686 2014/10 [Refereed][Not invited]
     
    The surface of polycrystalline titanium polarised anodically in 0.05 mol dm(-3) sulphuric acid was monitored using an ellipso-microscope. During dynamic polarisation, a patch-like bright image was seen on an ellipso-microscopic view, and the brightness and image changed with increase in potential. The change in the brightness and image mainly corresponded to growth of an anodic oxide film on the surface. An in situ monitoring using the ellipso-microscope revealed that the film formation rate was dependent on the crystallographic orientation of the substrate. Breakdown of the film induced in a solution containing bromide ions was also monitored using the microscope. Prior to the pitting propagation, the surface was partially changed with flow of a large anodic current. AES measurement revealed that the formation of bromo-oxide resulted in localised film degradation followed by pitting corrosion. (C) 2014 Elsevier Ltd. All rights reserved.
  • Yuichi Hirai, Takayuki Nakanishi, Kohei Miyata, Koji Fushimi, Yasuchika Hasegawa
    MATERIALS LETTERS 130 91 - 93 0167-577X 2014/09 [Refereed][Not invited]
     
    Thermo-stable lanthanide coordination polymers [Tb,Eu(hfa)(3)(dpbp)](n) composed of Tb(III) ion, Eu(III) ion, bidentate phosphine oxide (dpbp: 4,4'-bis(diphenylphosphoryl)biphenyl), and low-vibrational frequency hexafiuoroacetylacetonate (hfa) ligand are reported. The lanthanide coordination polymers [Tb,Eu(hfa)(3)(dpbp)](n) (Tb/Eu=1, 10, 250, 500, and 750) are characterized by XRD, emission spectra and emission lifetime measurements. The energy transfer efficiencies among lanthanide ions are estimated using the emission lifetimes of solid-state coordination polymers. Characteristic emission properties of lanthanide coordination polymers composed of Tb(III) ions and a small amount of Eu(III) ions (Tb/Eu=750) have been observed for the first time. The energy transfer between lanthanide ions in coordination polymers is described in terms of solid-state materials. (C) 2014 Elsevier B.V. All rights reserved.
  • Takayuki Nakanishi, Yuki Suzuki, Yoshihiro Doi, Tomohiro Seki, Hitoshi Koizumi, Koji Fushimi, Koji Fujita, Yukio Hinatsu, Hajime Ito, Katsuhisa Tanaka, Yasuchika Hasegawa
    INORGANIC CHEMISTRY 53 (14) 7635 - 7641 0020-1669 2014/07 [Refereed][Not invited]
     
    The effective magneto optical properties of novel nonanuclear Tb(III) complexes with Tb-O lattice (specifically, [Tb-9(sal-R)(16)(mu-OH)(10)]+NO3-, where sal-R = alkyl salicylate (R = -CH3 (Me), -C2H5 (Et), -C3H7 (Pr), or -C4H9 (Bu)) are reported. The geometrical structures of these nonanudear Tb(III) complexes were characterized using X-ray single-crystal analysis and shape-measure calculation. Optical Faraday rotation was observed in nonanuclear Tb(III) complexes in the visible region. The Verdet constant per Tb(III) ion of the Tb-9(sal-Me) complex is 150 times larger than that of general Tb(III) oxide glass. To understand their large Faraday rotation, electron paramagnetic resonance measurements of Gd(III) complexes were carried out. In this Report, the magneto optical relation to the coordination geometry of Tb ions is discussed.
  • K. Fushimi, M. Jin, T. Nakanishi, Y. Hasegawa, T. Kawano, M. Kimura
    ECS ELECTROCHEMISTRY LETTERS 3 (6) C21 - C23 2162-8726 2014 [Refereed][Not invited]
     
    The Devanathan-Stachurski electrochemical cell for measurement of hydrogen-permeation into a steel sheet was extended to an electrolyte-flowing design. Increase in flow rate of the entry cell induces increase in hydrogen-evolution current at the entry electrode but decrease in hydrogen-permeation current at the hydrogen-exit electrode. Hydrogen-permeation is actualized by a sinusoidal perturbation of the entry-flow rate. The hydrogen-permeation response, i.e., phase shift of the detection current from the evolution current, was proportional to the square root of flow rate frequency and was dependent on sheet thickness. The sinusoidal perturbation of entry-flow rate is a new factor influencing hydrogen-permeation into the sheet. (C) 2014 The Electrochemical Society. All rights reserved.
  • Yasuchika Hasegawa, Tomoki Ohkubo, Takayuki Nakanishi, Atsushi Kobayashi, Masako Kato, Tomohiro Seki, Hajime Ito, Koji Fushimi
    EUROPEAN JOURNAL OF INORGANIC CHEMISTRY 2013 (34) 5911 - 5918 1434-1948 2013/12 [Refereed][Not invited]
     
    The effect of ligand polarization on the formation of strongly luminescent lanthanide complexes with asymmetric structures is described for the first time. The lanthanide complexes are composed of Eu-III ions, three hexafluoroacetylacetonate (hfa) ligands, and two monodentate phosphine oxide ligands, namely, triphenylphosphine oxide (TPPO), p-tolyldiphenylphosphine oxide (TPPO-Me), tri-p-tolylphosphine oxide (TPPO-3Me) or o-phenoxyphenyldiphenylphosphine oxide (TPPO-OPh). The luminescence properties of the Eu-III complexes are characterized by their emission quantum yields, emission lifetimes, and their radiative (k(r)) and nonradiative (k(nr)) rate constants. The Eu-III complex with TPPO-OPh ligands offers a markedly high emission quantum yield (72% in [D-6]acetone, 85% in the solid state) owing to enhancement of the electric dipole transition and suppression of vibrational relaxation, which are directly related to k(r) and k(nr). The coordination geometries of the Eu-III complexes are categorized by shape-measure calculations. The Eu-III complexes exhibit characteristic square-antiprismatic or trigonal-dodecahedral structures, depending on the ligand polarization. Strongly luminescent Eu(hfa)(3)(TPPO-OPh)(2) has an asymmetric dodecahedron structure. The formation of distorted dodecahedral structures with low vibrational frequencies for the enhancement of luminescence is elucidated in terms of the ligand polarization of the monodentate phosphine oxide ligands in the Eu-III complexes.
  • K. Fushimi, K. Yanagisawa, T. Nakanishi, Y. Hasegawa, T. Kawano, M. Kimura
    ELECTROCHIMICA ACTA 114 83 - 87 0013-4686 2013/12 [Refereed][Not invited]
     
    Corrosion behavior of high-purity dual-phase carbon steel composed of only ferrite and martensite phases in 0.1 M sulfuric acid was investigated by both macro- and micro-electrochemical methods. The dual-phase steel corrodes non-uniformly due to galvanic coupling between its microstructures as well as self-corrosion of each phase. Hydrogen evolution reaction on galvanic-coupled martensite accelerates iron dissolution reaction of ferrite, though the corrosion rate of martensite was three-times larger than that of ferrite due to the self-corrosion in the acid. Totally, ferrite phases corrode selectively and the degree of selective corrosion was about two-times larger than martensite phases. (C) 2013 Elsevier Ltd. All rights reserved.
  • K. Fushimi, Y. Takabatake, T. Nakanishi, Y. Hasegawa
    ELECTROCHIMICA ACTA 113 741 - 747 0013-4686 2013/12 [Refereed][Not invited]
     
    Two micro-electrode techniques, scanning electrochemical microscopy (SECM) and the micro-capillary cell (MCC) technique, were used to investigate corrosion behaviour of a polycrystalline iron surface in acidic sulphate media. Local corrosion reactivity was found to be strongly dependent on crystallographic orientation of the surface as well as measurement conditions. Results obtained by using microelectrode techniques are expected to reveal all aspects of corrosion behaviour of the surfaces of polycrystalline materials including iron. (C) 2013 Elsevier Ltd. All rights reserved.
  • Akira Kawashima, Takayuki Nakanishi, Tamaki Shibayama, Seiichi Watanabe, Koji Fujita, Katsuhisa Tanaka, Hitoshi Koizumi, Koji Fushimi, Yasuchika Hasegawa
    CHEMISTRY-A EUROPEAN JOURNAL 19 (43) 14438 - 14445 0947-6539 2013/10 [Refereed][Not invited]
     
    Remarkable magneto-optical properties of a new isolator material, that is, europium sulfide nanocrystals with gold (EuS-Au nanosystem), has been demonstrated for a future photo-information technology. Attachment of gold particles that exhibit surface plasmon resonance leads to amplification of the magneto-optical properties of the EuS nanocrystals. To construct the EuS-Au nanosystems, cubic EuS and spherical Au nanocrystals have been joined by a variety of organic linkers, that is, 1,2-ethanedithiol (EDT), 1,6-hexanedithiol (HDT), 1,10-decanedithiol (DDT), 1,4-bisethanethionaphthalene (NpEDT), or 1,4-bisdecanethionaphthalene (NpDDT). Formation of these systems was observed by XRD, TEM, and absorption spectra measurements. The magneto-optical properties of the EuS-Au nanosystem have been characterized by using Faraday rotation spectroscopy. The Faraday rotation angle of the EuS-Au nanosystem is dependent on the Au particle size and interparticle distance between EuS and Au nanocrystals. Enhancement of the Faraday rotation of EuS-Au nanosystems was observed. The spin configuration in the excited state of the EuS-Au nanosystem was also investigated using photo-assisted electron paramagnetic resonance.
  • Akira Kawashima, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    MOLECULAR CRYSTALS AND LIQUID CRYSTALS 579 (1) 69 - 76 1542-1406 2013/09 [Refereed][Not invited]
     
    Novel photo-functional naphthalenedithiol (NpDDT) as a linker molecule for formation of EuS nanocrystal assembles (EuS nano-assembles) has been reported. NpDDT is synthesized by the reaction of 1,4-dihydroxynaphthalene with 1,10-decanedithiol in benzene at 80 degrees C for 1hour. Formation of EuS nano-assembles with NpDDT is observed by TEM measurement. Photophysical properties of EuS nano-assembles with NpDDT are characterized using the emission spectra and the emission quantum yields. The emission quantum yields of naphthalene units in NpDDT are depended on the aggregation size of EuS nano-assembles. Novel luminescent NpDDT has been reported as an effective linker material for formation and observation of semiconductor EuS nano-assembles for the first time.
  • Takayuki Nakanishi, Masashi Maeda, Akira Kawashima, Shogo Kamiya, Koji Fushimi, Koji Fujita, Katsuhisa Tanaka, Yasuchika Hasegawa
    Journal of Alloys and Compounds 562 123 - 127 0925-8388 2013/06/15 [Refereed][Not invited]
     
    Novel magneto-optical silica glass with semiconductor EuS nanocrystals (NCs) has been reported. The silica glass with EuS NCs is synthesized by the hydrolysis reaction with a ligand exchange process (from NH2-group to OH-group). The silica framework around EuS NCs provides thermo-stable structure under 500 °C. The glass material also shows effective magneto-optical properties, Faraday rotation, in the visible region (400-700 nm). The positive peak of Faraday rotation spectrum is blue-shifted in comparison with traditional EuS NCs in PMMA polymer. The effective peak-shift of Faraday rotation is caused by ligand change on EuS NCs surface (Nephelauxetic effect). The EuS-silica nanoglass composite with thermally stable structure would have potential applications as an optical isolator with a high-power laser. © 2013 Elsevier B.V. All rights reserved.
  • Yasuchika Hasegawa, Masashi Maeda, Takayuki Nakanishi, Yoshihiro Doi, Yukio Hinatsu, Koji Fujita, Katsuhisa Tanaka, Hitoshi Koizumi, Koji Fushimi
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 135 (7) 2659 - 2666 0002-7863 2013/02 [Refereed][Not invited]
     
    Novel EuS nanocrystals containing paramagnetic Mn(II), Co(II), or Fe(II) ions have been reported as advanced semiconductor materials with effective optical rotation under a magnetic field, Faraday rotation. EuS nanocrystals with transition-metal ions, EuS:M nanocrystals, were prepared by the reduction of the Eu(III) dithiocarbamate complex tetraphenylphosphonium tetrakis(diethyldithiocarbamate)europium(III) with transition-metal complexes at 300 degrees C. The EuS:M nanocrystals thus prepared were characterized using X-ray diffraction (XRD), transmission electron microscopy (TEM), inductively coupled plasma atomic emission spectroanalysis (ICP-AES), and a superconducting quantum interference device (SQUID) magnetometer. Enhanced Faraday rotations of the EuS:M nanocrystals were observed around 550 nm, and their enhanced spin polarization was estimated using electron paramagnetic resonance (EPR) measurements. In this report, the magneto-optical relationship between the Faraday rotation efficiency and spin polarization is discussed.
  • Kohei Miyata, Yuji Konno, Takayuki Nakanishi, Atsushi Kobayashi, Masako Kato, Koji Fushimi, Yasuchika Hasegawa
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 52 (25) 6413 - 6416 1433-7851 2013 [Refereed][Not invited]
  • Takatoshi Shimada, Koji Fushimi, Achim Walter Hassel, Hidetaka Konno
    CORROSION REVIEWS 30 (5-6) 199 - 207 0334-6005 2012/12 [Refereed][Not invited]
     
    The rupture behavior of an anodized aluminum surface was investigated in a borate buffer solution using an in situ micro-indentation test, in which transients of the indentation load and flowing current were monitored during loading and unloading of a sapphire indenter. A pair of anodic current peaks emerged during both downward and upward drives of the indenter due to rupture and repair of an anodic oxide film. The total area of film ruptured during both drives, as well as the area of radial cracks, increased with an increase in film thickness and with a decrease in electric field applied while an area of circular cracks was almost constant. It was suggested that the film-rupture owing to radial cracks formation was enhanced by tensile stress accumulated in the anodic oxide film by thickening of the oxide film and lowering of the electrostriction.
  • Yasuchika Hasegawa, Mina Kumagai, Akira Kawashima, Takayuki Nakanishi, Koji Fujita, Katsuhisa Tanaka, Koji Fushimi
    JOURNAL OF PHYSICAL CHEMISTRY C 116 (36) 19590 - 19596 1932-7447 2012/09 [Refereed][Not invited]
     
    Novel magneto-optical thin films composed of europium sulfide (EuS) nanoparticles on a glass electrode exhibit large magneto-optical efficiency and a wide energy gap. EuS nanoparticle thin films are prepared by the electrochemical reduction of a single-source precursor, a Eu(III) dithiocarbamate complex (tetraphenylphosphonum tetrakis(diethyldithiocarbamate) europium(III)). The EuS nanoparticle thin films were prepared on indium-tin oxide (ITO)-coated glass electrodes and characterized by electrochemical analysis, scanning electron microscopy, energy-dispersive X-ray spectroscopy, transmission electron microscopy, laser scanning microscopy, and absorption spectroscopy. Faraday rotation spectra for estimation of the magneto-optical efficiency have clear positive and negative peaks, which are attributed to the 4f-5d transitions of the EuS thin films. The positive and negative peaks of the Faraday rotation spectrum are 525 and 680 nm, which are directly related to the energy gap of the EuS nanoparticle thin film (2.4 eV). That spectrum indicates that the EuS nanoparticle thin films are blue shifted in comparison with 7 nm diameter EuS nanoparticles (2.2 eV). The Verdet constant of the thin film was 11 mdeg/cm Oe at 525 nm, which is approximately 10 times larger than that of previously reported EuS nanoparticles.
  • Koji FUSHIMI, Harunori WATANABE, Takayuki NAKANISHI, Yasuchika HASEGAWA
    J. Surf. Finish. Soc. Jpn 表面技術協会 63 (6) 375 - 380 0915-1869 2012/06 [Refereed][Not invited]
     
    Flowing-type micro-droplet cells (f-MDC) were applied to the anodic polarization of titanium surface in sodium-chloride-containing ethylene glycol solution. Anodic current attributable to removal of the surface oxide and the dissolving substrate flowed locally at the area limited with f-MDC, forming a hole on the surface. The hole shape and morphology were dependent on the applied voltage, polarization time, flowing volume rate, and the capillary employed for the f-MDC. Suitable conditions for polarization to obtain an ordered hole with f-MDC were discussed.
  • Kohei Miyata, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY 235 35 - 39 1010-6030 2012/05 [Refereed][Not invited]
     
    Solvent-dependent luminescence of Eu(III) complexes composed of oxo-linked bidentate phosphine oxide ligands, 4,5-bis(diphenylphosphoryl)-9,9-dimethylxanthene (xantpo). 4,5-bis(di-tert-butylphosphoryl)-9,9-dimethylxanthene (tBu-xantpo) and low-vibrational frequency hexafluoroacetylacetonato (hfa) ligands is reported. The Eu(III) complexes. Eu(hfa)(2)(xantpo)(2) and Eu(hfa)(3)(tBu-xantpo), exhibit eight-coordinated square antiprism and trigonal dodecahedron structure, respectively. Their emission quantum yield, emission lifetime, and radiative and non-radiative rate constant are characterized using acetone, acetone-d(6), toluene, chloroform, and DMF. The relationship between photophysical properties and coordination structures of eight-coordinated Eu(III) complexes is discussed for the first time. (C) 2012 Elsevier B.V. All rights reserved.
  • Masahiro Seo, Koji Fushimi, Yoshitaka Aoki, Hiroki Habazaki, Masayuki Inaba, Mitsutoshi Yokomizo, Takazumi Hayakawa, Takenori Nakayama
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 671 7 - 15 1572-6657 2012/04 [Refereed][Not invited]
     
    In situ X-ray absorption spectroscopy (XAS) using a synchrotron radiation was applied to identify the Pb species adsorbed on Ni surface in acidic perchlorate solution containing 10(-4) M Pb2+ with relation to the Pb-induced stress corrosion cracking (Pb-SCC) of Ni-base alloys used as tubing materials of steam generators in nuclear power plants. The periodical emersion method under potentiostatic polarization, using the Ni plate with large specific surface area (surface roughness, S-r = 78.3) as a working electrode, was developed to detect sensitively the sub-monolayer coverage of Pb on Ni. The Pb L-III absorption spectra in a scanning XAS mode were measured by monitoring the Pb L alpha fluorescence line. The Pb L-III absorption near-edge structure (XANES) at the potential more positive than -0.245 V (SHE) corresponding to the equilibrium potential of Pb-electrodeposition in 10(-4) M Pb2+ solution has revealed that the Pb species adsorbed on the Ni surface are metallic, providing the clear evidence of underpotential deposition (UPD) of Pb on the Ni surface. Moreover, the extended X-ray absorption fine structure (EXAFS) analysis was performed with a two-shell fit involving Pb-Ni and Pb-Pb interactions assuming that the Ni (1 1 1) plane is mainly exposed to the solution. The EXAFS results were convincingly explained in terms of the Pb-UPD model which represents the coexistence of the surface alloy phase and the adlayer with the same p(2 x 2) structure in the narrow potential range of -0.185 V (SHE) to -0.245 V (SHE). (C) 2012 Elsevier B.V. All rights reserved.
  • Kohei Miyata, Tadashi Ohba, Atsushi Kobayashi, Masako Kato, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    CHEMPLUSCHEM 77 (4) 277 - 280 2192-6506 2012/04 [Refereed][Not invited]
  • SECM OBSERVATION OF POLYCRYSTALLINE IRON CORRODING IN SULPHURIC ACID SOLUTION
    K. Fushimi, K. Matsushita, H. Tachikawa, Y. Hasegawa
    Proceedings of 18th International Corrosion Congress (CD-ROM) 377  2011/11 [Refereed][Not invited]
  • Koji Fushimi, Ken-ichiro Matsushita, Yasuchika Hasegawa
    ELECTROCHIMICA ACTA 56 (26) 9602 - 9608 0013-4686 2011/11 [Refereed][Not invited]
     
    Electrochemical interaction of coaxial double microelectrodes, in which a ring microelectrode was surrounded by another ring microelectrode, was investigated. Mass-transfer reactions that occurred on both inner and outer microelectrodes interfered with each other and showed a "shielding" effect depending on potentials and geometries of microelectrodes. Application of the inner microelectrode of the double microelectrodes for a probing tip of a scanning electrochemical microscope (SECM) revealed that the shielding effect by the outer microelectrode affected the electrochemistry on the inner microelectrode in the vicinity of the substrate surface. The effect was intensified above the insulator but attenuated above the conductor as the microelectrodes approached in feedback mode of the SECM. Approach to a critical interelectrode distance also intensified the shielding effect in the substrate generation/tip collection mode. An SECM line-scan using a platinum/epoxy resin-model substrate was carried out to investigate the shielding effect on current sensitivity and lateral resolution of an SECM image. (C) 2011 Elsevier Ltd. All rights reserved.
  • Masatoshi Sakairi, Yoshihito Goto, Tatsuya Kikuchi, Koji Fushimi
    J. Surf. Finish. Soc. Jpn 一般社団法人 表面技術協会 62 (10) 511 - 515 0915-1869 2011/10 [Refereed][Not invited]
     
    A solution flow type microdroplet cell was applied to form a local copper line on a non-conductive substrate such as epoxy resin. During copper deposition, a copper rod was mounted in the epoxy resin as an electric feeding point. Such a copper line, which can be formed on the epoxy resin on flat and curved surfaces, can be removed from the epoxy resin, suggesting that this technique is applicable to form metal microstructures. The influence of the stage moving speed and applied current on the copper line thickness, shape, and conductivity were also investigated.
  • K. Fushimi, A. Ono, K. Matsushita, H. Kumagai, H. Konno
    APPLIED SURFACE SCIENCE 257 (19) 8289 - 8294 0169-4332 2011/07 [Refereed][Not invited]
     
    A simple heat treatment was used to fabricate carbonaceous layer-coated electrodes: micro-ring electrodes and conductive stainless steel. Substrates of sharpened quartz capillaries or type-316 stainless steel plates were put in an alumina boat with powder of petroleum pitch A240F separately and heated at 1073-1273 K in a flow of nitrogen or argon. By this treatment, both of the substrates were coated with a uniform carbonaceous layer of several hundred nano-meters in thickness. The electric conductivity of the layer was improved by increases in temperature and period of the heating. The quartz glass-capillary covered with the conductive layer was modified to a needle-type microelectrode by coating with an insulating polymer and baring the tip. At least a dozen carbon micro-ring electrodes with an outer radius of about 1 mu m were successfully prepared by the simple heat treatment. On the other hand, the carbonaceous layer formed on type-316 stainless steel showed relatively poor conductivity due to the formation of oxides in the layer. However, the conductivity was improved by electroplating of nickel on the substrate before the heating. The carbonaceous layer-coated stainless steel showed good corrosion resistance in sulphuric acid. (C) 2011 Elsevier B. V. All rights reserved.
  • M. Tauseef Tanvir, T. Fujii, Y. Aoki, K. Fushimi, H. Habazaki
    APPLIED SURFACE SCIENCE 257 (19) 8295 - 8300 0169-4332 2011/07 [Refereed][Not invited]
     
    For electrolytic capacitor application of the single-phase Ti alloys containing supersaturated silicon, which form anodic oxide films with superior dielectric properties, porous Ti-7 at% Si columnar films, as well as Ti columnar films, have been prepared by oblique angle magnetron sputtering on to aluminum substrate with a concave cell structure to enhance the surface area and hence capacitance. The deposited films of both Ti and Ti-7 at% Si have isolated columnar morphology with each column revealing nanogranular texture. The distances between columns are similar to 500 nm, corresponding to the cell size of the textured substrate and the gaps between columns are 100-200 nm. When the porous Ti-7 at% Si film is anodized at a constant current density in ammonium pentaborate electrolyte, the growth of a uniform amorphous oxide film continues to similar to 35 V, while it is limited to less than 6 V on the porous Ti film. The maximum voltage of the growth of uniform amorphous oxide films on the Ti-7 at% Si films is similar for both the flat and porous columnar films, suggesting little influence of surface roughness on the amorphous-to-crystalline transition of growing anodic oxide under the high electric field. Due to the suppression of crystallization to sufficiently high voltages, the anodic oxide films formed on the porous Ti-7 at% Si film shows markedly improved dielectric properties, in comparison with those on the porous Ti film. (C) 2011 Elsevier B. V. All rights reserved.
  • Shuji Hashizume, Toshiya Nakayama, Masatoshi Sakairi, Koji Fushimi
    Zairyo to Kankyo/ Corrosion Engineering 60 (4) 196 - 201 0917-0480 2011 [Refereed][Not invited]
     
    Low Carbon-13%Cr martensitic stainless steels have been widely used for line pipe application because of their high strength and excellent corrosion resistance in corrosive conditions. Recently, both laboratory and field experiences related to cracking near fusion line of these steels weld joints in hot acid environments have been published. In this paper, SCC (Stress Corrosion Cracking) mechanism near fusion line of low C..13..Cr welded joints is discussed. Especially, initiation process is focused. Mainly electrochemical measurement using solution flow type micro-droplet cell and surface analysis of weld joints are conducted. In the evaluation of electrochemical behavior of low C-13%Cr welded joints with and without PWHT (Post Welded Heat Treatment) by the use of a solution flow type micro-droplet cell, PWHT leads to more noble and stable potential in HAZ (Heat Affected Zone) compared to as-welded condition. In the HAZ portion of the as-welded joint, Cr depleted layer was detected under welding scale with the use of GDS (Glow Discharge Spectrometer). PWHT was confirmed to eliminate Cr depleted layer under welding scale. This can be an initiation of SCC near girth welded joint in hot acid environment. Finally, mechanism of SCC initiation near fusion line of as-welded joint was proposed. Localized corrosionwould start at Cr depleted layer under welding oxide scale. This dissolution was also accelerated by a galvanic effect due to a large cathode area of base metal.
  • Takatoshi Shimada, Koji Fushimi
    Zairyo to Kankyo/ Corrosion Engineering 腐食防食協会 60 (1) 28 - 38 0917-0480 2011 [Refereed][Not invited]
     
    A micro-indentation test was developed to investigate mechano- electochemical properties of metal surfaces. In solution environment, the contact of an indenter with an iron passive surface causes depassivation of the surface when the surface deforms plastically. The scale of the depassivation is dependent on hardness and deformation area of the substrate iron. Repassivation following depassivation is affected by not only electrode potential of the specimen and solution conditions (pH and electric conductivity of the solution) but also dislocation in the substrate iron. Furthermore, the micro-indentation test is useful as a rupture technique of the passive film in order to examine the corrosion resistance of stainless steels. It enables to control the deformation area of metal surfaces at an intentional site in a micrometer-order and to serve an in-situ measurement of electrochemical responses. This technique is suitable for consideration of the mechanism and kinetics of depassivation-repassivation behavior of the surface depending on fine metal structures.
  • T. Murata, Y. Goto, M. Sakairi, K. Fushimi, T. Kikuchi
    PITS AND PORES 4: NEW MATERIALS AND APPLICATIONS - IN MEMORY OF ULRICH GOSELE 33 (16) 57 - 63 1938-5862 2011 [Refereed][Not invited]
     
    A novel solution flow-type micro droplet cell with co-axial dual capillary tubes (Sf-MDC) was applied to form porous type aluminum anodic oxide film locally. This technique makes it possible to form porous type anodic oxide film on aluminum locally. When the droplet cell remains stationary, the oxide film was growing both vertically and laterally. The growth rate in the lateral direction can be controlled by moving the droplet cell. By moving the droplet cell, a porous type anodic oxide film line was successfully formed. The thickness of the oxide film increases with decreasing scanning speed of the cell. The oxide film growth rate was greatly affected by specimen temperature.
  • Heterogeneous dissolution of polycrystalline pure iron in sulphuric acid solution
    K. Fushimi, K. Matsushita, K. Miyamoto, Y. Hasegawa
    Proceedings of EUROCORR 2011 (CD-ROM) 4747  2011 [Refereed][Not invited]
  • 走査型電気化学顕微鏡の腐食への適用
    伏見公志
    材料科学会腐食防食部門委員会資料 50 (4) 23 - 29 2011 [Not refereed][Not invited]
  • フロー型微小液滴セルによる素材の耐食性評価
    伏見公志
    軽金属学会：研究部会報告書No. 55アルミニウム合金化成処理材・塗装材の耐食性に及ぼす微量添加元素の影響 106 - 108 2011 [Not refereed][Not invited]
  • Koji Fushimi, Takatoshi Shimada, Hiroki Habazaki, Hidetaka Konno, Masahiro Seo
    ELECTROCHIMICA ACTA 56 (4) 1773 - 1780 0013-4686 2011/01 [Refereed][Not invited]
     
    Depassivation-repassivation of iron surfaces in boric-borate solutions were investigated by using the micro-indentation test. A pair of current peaks due to repair of the passive film following rupture of the film were observed during a series of indenter drives, i.e., loading and unloading of the indenter. The shape of the current peak depended on environmental conditions (conductivity and pH of the solution) and substrate conditions (mechanical processing history, alloyed element) as well as indentation conditions (repetition, maximum depth, and maximum load). Plastic deformation of the surface was accompanied by surface depassivation, while no depassivation occurred during the elastic deformation, indicating that the passive film on iron has a ductile property. The solution conditions did not affect the scale of depassivation but affected the rate of repassivation. Dislocations in the substrate made surface depassivation difficult but enhanced reactivity during the repassivation. The test also revealed that type-312L stainless steel has high corrosion resistance in a concentrated NaCl solution. (C) 2010 Elsevier Ltd. All rights reserved.
  • Fushimi K, Matsushita K, Tachikawa H, Hasegawa Y
    18th International Corrosion Congress 2011 2 1223 - 1230 2011 [Refereed][Not invited]
  • Koji Fushimi, Kazunari Miyamoto, Hidetaka Konno
    ELECTROCHIMICA ACTA 55 (24) 7322 - 7327 0013-4686 2010/10 [Refereed][Not invited]
     
    Anisotropic corrosion behaviour of a single grain of pure iron in 0.05 mol dm(-3) sulphuric acid (pH 1) was investigated by a simple polarization technique Both corrosion potential and corrosion current were found to be dependent on crystallographic orientation of the iron grain. A high corrosion current flowed on a grain showing a relatively noble corrosion potential. although both cathodic and anodic Tafel slopes were independent of the orientation It was shown that cathodic hydrogen evolution reaction (HER) governed the corrosion reaction on the iron grain. Covalent bonding of Fe and H and coverage of H on Fe seem to play important roles in the HER and anisotropic corrosion behaviour of pure iron (C) 2010 Elsevier Ltd All rights reserved
  • Takashi Fujii, Yoshitaka Aoki, Koji Fushimi, Takeshi Makino, Shoji Ono, Hiroki Habazaki
    NANOTECHNOLOGY 21 (39) 0957-4484 2010/10 [Refereed][Not invited]
     
    Nanopillar films of Al-Nb alloys have been fabricated on substrates with a regular concave cell structure by oblique angle physical vapor deposition. The concave cell structure of the substrate increases the shadow region for the flux of depositing atoms, assisting the formation of an isolated nanopillar on each cell. Depending upon the alloy composition and deposition angle, the pillar shape changes from horn-like nanopillars through triangular nanoprisms to nanoplates. The Al-Nb alloy nanoplate films with wide gaps between plates are of interest as electrodes for capacitor applications. The dielectric oxide film formed on the nanoplate film showed a capacitance more than ten times larger than that on the respective flat film, due to the enlarged surface area.
  • Atsushi Naganuma, Koji Fushimi, Kazuhisa Azumi, Hiroki Habazaki, Hidetaka Konno
    CORROSION SCIENCE 52 (4) 1179 - 1186 0010-938X 2010/04 [Refereed][Not invited]
     
    Crevice corrosion of iron was evaluated using the multichannel electrode method in which 10 individual working electrodes (WEs) of pure iron were embedded in resin, placed in an artificial crevice in the range from 0.5 mm to 2.0 mm, and immersed in 0.51 mol dm(-3) NaCl solution. The WEs were connected to an electronic circuit which allowed galvanic coupling between them and measurement of their individual coupling current or open circuit potential. Time-transient of the spatial distribution of coupling current and open circuit potential showed sequential transition of the coupling current on WEs at the middle position of the crevice from cathode to anode. The WE near the opening of the crevice initially showed a large anodic current, then a decreasing the anodic current corresponding to the current transition of other WEs, and finally a large cathodic current coupled with the other anodic WEs in the crevice. The transition of coupling current was explained by the change in pH and concentration of dissolved oxygen in the crevice. Thickness of the gap of the artificial crevice affected the transition behavior of coupling current distribution. For example, slower current transition with smaller coupling current was found in the case of a narrower gap. Such properties were related to the introduction and consumption of dissolved oxygen in the crevice solution and the circulation of gap solution from/to the outside of the crevice. (C) 2010 Elsevier Ltd. All rights reserved.
  • Hidetaka Konno, Teruhiko Ito, Mariko Ushiro, Koji Fushimi, Kazuhisa Azumi
    JOURNAL OF POWER SOURCES 195 (6) 1739 - 1746 0378-7753 2010/03 [Refereed][Not invited]
     
    The B/C/N composites were synthesized by a very simple method. that is, carbonization at HTT = 800-1200 degrees C of the precursor prepared by drying a solution mixture of polyacrylamide and boric acid, followed by boiling in water to remove borate by-products The amount of insoluble B species in I lie composite increased linearly from 4 8 to 18.6 mass% with raising HTT The XRD and FT-IR revealed that turbostratic h-BN started to form at around 1000 degrees C as a by-product. By XPS. major B and N components in I lie compost le were B-N bond. C-B-O type B. pyridinic N. pyrrolic N, and quaternary N A fraction for B-N bond including h-BN in the total B or N components increased with raising HTT and it exceeded 50 at % between 900 and 1000 C. It Was Suggested that in the composites formed at HTT > 1000 degrees C the amounts of h-BN increased, leading to reduction in other B and N components. The S(BET) was almost unchanged up to 1000 C. 410-420 m(2) g(-1). Large and broad redox peaks arisen from plural reactions appeared in the cyclic voltammogram (CV) measured in 1 mol dm(-3) H(2)SO(4) for the composites formed at HTT <= 1000 degrees C. These peaks disappeared in 1 mol dm(-3) solutions of Na(2)SO(4) and Li(2)SO(4). By comparing CV with that for C/N composite formed from PAA by the MgO template method, the pseudo-capacitance owing to reactions of B-N and C-B-O components with protons Was found to be added to commonly observed pseudo-capacitance for nitrogen-cloped carbons The capacitances foi tile composites foinied at 850-950 degrees C exceeded 300 Fg(-1) at 2 mV s(-1) in the acid electrolyte and the retention at 50 mV s(-1) was 78-80% The shape of CV in the neutral electrolytes was trapezoid and the Current density increased with lowering potential, suggesting adsorption and desorption of Na(+) and Li(+) ions This was considered to be due to doped nitrogen indicating the development of pseudo-capacitance the capacitance per S(BET) was 0.33-074 F m(-2) and 017-032 F m(-2). larger for lower HTT, it, the acid and neutral electrolytes, respectively. (C) 2009 Elsevier B.V. All rights reserved.
  • Masatoshi Sakairi, Yoshihito Goto, Koji Fushimi, Tatsuya Kikuchi, Hideaki Takahashi
    ELECTROCHEMISTRY 78 (2) 118 - 121 1344-3542 2010/02 [Refereed][Not invited]
     
    A new method for mask-less fabrication of metal micro-rods is described. The developed solution flow type droplet cell micro fabrication technique was applied to form Cu micro-rods. The use of an inner capillary tube as a mold during electrodeposition, makes it possible to form Cu micro-rods of about 15 mm length and about 100 mu m diameter. The length is controlled by the deposition time. From X-ray analysis and surface observations, the formed Cu micro-rod is polycrystalline and the crystals are very fine. The cross section of the micro-rod was almost circular and the diameter was almost the same throughout its length. This technique also makes it possible to form straight metal structures as well as branched and layered micro-rods. This layered micro-rod fabrication technique can be applied to form resistance controlled micro wires.
  • Masatoshi Sakairi, Yoshihito Goto, Koji Fushimi, Tatsuya Kikuchi, Hideaki Takahashi
    ELECTROCHEMISTRY 電気化学会 78 (2) 118 - 121 1344-3542 2010/02 [Refereed][Not invited]
     
    A new method for mask-less fabrication of metal micro-rods is described. The developed solution flow type droplet cell micro fabrication technique was applied to form Cu micro-rods. The use of an inner capillary tube as a mold during electrodeposition, makes it possible to form Cu micro-rods of about 15 mm length and about 100 mu m diameter. The length is controlled by the deposition time. From X-ray analysis and surface observations, the formed Cu micro-rod is polycrystalline and the crystals are very fine. The cross section of the micro-rod was almost circular and the diameter was almost the same throughout its length. This technique also makes it possible to form straight metal structures as well as branched and layered micro-rods. This layered micro-rod fabrication technique can be applied to form resistance controlled micro wires.
  • Takatoshi Yamamoto, Koji Fushimi, Seiji Miura, Hidetaka Konno
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 157 (7) C231 - C237 0013-4651 2010 [Refereed][Not invited]
     
    The influence of substrate dislocations on the passivation behavior of pure iron in a pH 8.4 borate buffer solution was investigated. Cold-rolling was employed to induce dislocation in the annealed substrate. The dislocation density on the cold-rolled substrate depended on the reduction ratio (Red) and was maximum at Red = 60%. The electric charge consumed in the passivation and the passivity-maintaining current increased with an increase in the dislocation density. Electrochemical impedance spectroscopy revealed that the dislocation exposed to the iron surface increased the donor density in the passive film and reduced the charge-transfer resistance for the film aging. It was also demonstrated by radio frequency-glow discharge optical emission spectroscopy that a thick passive film formed on the cold-rolled iron compared with that on annealed iron. These results suggest that substrate dislocations enhance the reactions at the substrate/film interface, resulting in the formation of a highly defective passive film. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3425607] All rights reserved.
  • K. Fushimi, H. Kondo, H. Konno
    CORROSION (GENERAL) - 216TH ECS MEETING 25 (37) 111 - 117 1938-5862 2010 [Refereed][Not invited]
     
    Anodic dissolution behaviour of titanium in ethylene glycol solution containing chloride salt was examined using a rotating disk electrode. A potential-independent dissolution current flowed depending on the rotation speed, species and concentration of chloride salts. The current controlled by the mass transfer process could flow in concentrated chloride solutions, but decreased with increase in chloride concentration. A smaller current flowed in solution with a high concentration of titanium species, indicating that the diffusion-controlling species are titanium species, not chloride ions. Electrochemical impedance spectroscopy revealed that a titanium chloride salt layer was formed between the titanium substrate and diffusion layer during the mass transfer-controlling anodic dissolution of titanium.
  • T. Yamamoto, K. Fushimi, S. Miura, H. Konno
    OXIDE FILMS 25 (40) 3 - 15 1938-5862 2010 [Refereed][Not invited]
     
    The influence of substrate dislocations on passivation behavior of a pure iron in pH 8.4 borate buffer solution was investigated. Cold rolling was employed to induce dislocation in the annealed substrate. The dislocation density on the cold rolled substrate depended on the reduction ratio (Red) and was maximum at Red = 60%. The electric charge consumed in the passivation and the passivity-maintaining current increased with increase in the dislocation density. EIS revealed that the dislocation exposed to the iron surface increased donor density in the passive film and reduced charge transfer resistance for the film aging. It was also demonstrated by rf-GDOES that a thick passive film formed on the cold rolled iron compared with that on annealed iron. These results suggest that substrate dislocations enhance the reactions at the substrate/film interface, resulting in the formation of the highly defective passive film.
  • Takatoshi Yamamoto, Koji Fushimi, Hiroki Habazaki, Hidetaka Konno
    ELECTROCHIMICA ACTA 55 (3) 1232 - 1238 0013-4686 2010/01 [Refereed][Not invited]
     
    Depassivation-repassivation behavior on a pure iron surface in borate buffer solution was examined under potentiostatic control by a micro-indentation test. Current peaks emerge during both downward and upward drives of the indenter due to depassivation which is caused by plastic deformation of the substrate but not elastic deformation and repassivation. The total electric charge of the current peaks is proportional to the maximum load. The total electric charge also increases with increase in intermission time of the indentation, indicating that the passive film is ruptured even during stress relaxation. It is estimated from the electric charge balance that 82% and 18% of the film rupture occurs during the downward drive and intermission, respectively, and that no rupture occurs during the upward drive. Furthermore, the film-ruptured area is estimated to be 80% of the plastic deformed surface area. The partial retainment of the passive film on iron suggests that the ductility of the passive film is higher than that of the substrate. (c) 2009 Elsevier Ltd. All rights reserved.
  • Masatoshi Sakairi, Takuya Murata, Tatsuya Kikuchi, Koji Fushimi
    ISIJ INTERNATIONAL 50 (10) 1466 - 1470 0915-1559 2010 [Refereed][Not invited]
     
    A solution resistance reduced solution flow type micro-droplet cell with co-axial dual capillary tubes was developed. A Pt counter electrode wire, 50 mu m diameter, inserted in the inner capillary tube, successfully reduced solution resistance between the working and counter electrodes. The potentio-dynamic polarization measurements showed the electrochemical performance of developed droplet cell to be very similar to that of traditional macro sized electrochemical cells. The developed droplet cell was applied to obtain line profiles of a current at a constant potential across the surface of for cross-sections of model metal interfaces. The current changed at the model interface between deposited nickel and substrate, and the spatial resolution of the developed droplet cell was reduced with increasing scanning speed of the cell. The results reported in this paper suggest that this technique would be able to measure differences in corrosion resistance in welded metal components and base metals.
  • K. Fushimi, M. Sakairi, H. Habazaki
    J. Surf. Finish. Soc. Jpn 一般社団法人 表面技術協会 59 (12) 863 - 868 0915-1869 2009/12 [Refereed][Not invited]
  • Koji Fushimi, Hirofumi Kondo, Hidetaka Konno
    ELECTROCHIMICA ACTA 55 (1) 258 - 264 0013-4686 2009/12 [Refereed][Not invited]
     
    Anodic dissolution behavior of titanium in chloride-containing ethylene glycol was examined using a rotating disk electrode. A potential-independent dissolution current flowed depending on the rotation speed, species and concentration of chloride salts. In solutions with lower concentrations of chloride, a potential-independent current was controlled not only by the mass transfer process but also by the charge transfer, and the kinetic-controlling current depends on solution conductivity. In concentrated chloride solutions, the current was controlled only by mass transfer process and decreased with increase in chloride concentration. A smaller current also flowed in a solution with a high concentration of titanium species. These results indicated that the diffusion-controlling species are titanium species, not chloride ions. Electrochemical impedance spectroscopy revealed that a titanium chloride salt layer, which maintains titanium species at a high concentration, accumulates a low charge (similar to 0.1 mu F cm(-2)) and becomes thicker with increase in applied potential, is formed between the titanium substrate and diffusion layer during the mass transfer-controlling dissolution. (C) 2009 Elsevier Ltd. All rights reserved.
  • Y. Oikawa, T. Minami, H. Mayama, K. Tsujii, K. Fushimi, Y. Aoki, P. Skeldon, G. E. Thompson, H. Habazaki
    ACTA MATERIALIA 57 (13) 3941 - 3946 1359-6454 2009/08 [Refereed][Not invited]
     
    Porous anodic niobium oxide with a pore size of similar to 10 nm was formed at 10 V in glycerol electrolyte containing 0.6 mol dm(3) K(2)HPO(4) and 0.2 mol dm(-3) K(3)PO(4) at 433 K. After prolonged anodizing for 5.4 ks, niobium oxide microcones develop on the surface. X-ray diffraction patterns of the anodized specimens revealed that the initially formed anodic oxide is amorphous, but an amorphous-to-crystal-line transition occurs during anodizing. As a consequence of the preferential chemiccal dissolution of the initially formed amorphous oxide, due to different solubility of the amorphous and crystalline oxides, crystalline oxide microcones appear on the film surface after prolonged anodizing. The surface is superhydrophilic. After coating with fluorinated alkylsilane, the surface becomes superhydrophobic with a contact angle of 158 degrees for water. The surface is also oil repellent, with a contact angle as high as 140 degrees for salad oil. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
  • Takatoshi Yamamoto, Koji Fushimi, Masahiro Seo, Shiro Tsuri, Tetsuo Adachi, Hiroki Habazaki
    CORROSION SCIENCE 51 (7) 1545 - 1553 0010-938X 2009/07 [Refereed][Not invited]
     
    Repassivation behavior of type-312L stainless steel containing 6% of molybdenum was examined in NaCl solution using in situ micro-indentation technique, together with type-304 and 316L stainless steels. High stability of the passive film formed on the type-312L stainless steel was also examined by depth profiling analysis of passive films using glow discharge optical emission spectroscopy (GDOES). In 0.9 mol dm(-3) NaCl solution at 296 K the type-304 and 316L stainless steels are passive only up to 0.3 V (SHE), above which pitting corrosion occurs. In contrast, no pitting corrosion occurs on type-312L stainless steel. Despite the significant difference of the pitting corrosion resistance, the repassivation kinetics of the three stainless steels, examined by micro-indentation at 0.3 V (SHE), is similar. The presence of molybdenum in the stainless steel does not influence the repassivation kinetics. The charge required to repassivate the ruptured type-312L stainless steel surface increases approximately linearly with the potential, even though the passivity-maintaining current increased markedly at potentials close to the transpassive region. Repassivation occurs without accompanying significant dissolution of steel, regardless of the stability of passive state. Depth profiling analyses of the passive films on the type-312L stainless steels formed at several potentials revealed that molybdenum species enrich in the outer layer of the passive film, below which chromium-enriched layer is present. The permeation of chloride ions may be impeded by the outer layer containing molybdate, enhancing the resistance against the localized corrosion of the type-312L stainless steel. (C) 2008 Elsevier Ltd. All rights reserved.
  • M. Uemura, T. Yamamoto, K. Fushimi, Y. Aoki, K. Shimizu, H. Habazaki
    CORROSION SCIENCE 51 (7) 1554 - 1559 0010-938X 2009/07 [Refereed][Not invited]
     
    Thin passive films formed on highly corrosion-resistant type-312L stainless steel, containing 20 mass% chromium and 6 mass% molybdenum, in 2 mol dm(-3) HCl solution at 293 K have been analyzed by glow discharge optical emission spectroscopy (GDOES). The stainless steel does not suffer pitting corrosion even in this aggressive solution, showing a wide passive potential region. The depth profiles obtained clearly show a two-layer structure of the air-formed and passive films: an outer iron-rich layer and an inner layer highly enriched in chromium. Alloy-constituting molybdenum is deficient in the inner layer of the passive films and is enriched in the outer layer, particularly at the active dissolution potential. The molybdenum species in the outer layer may retard the active dissolution of stainless steel, promoting the formation of stable passive films highly enriched in chromium. Chloride ions are present only at the outermost part of the passive films, not penetrating into the interior part. (C) 2008 Elsevier Ltd. All rights reserved.
  • M. Nakajima, Y. Miura, K. Fushimi, H. Habazaki
    CORROSION SCIENCE 51 (7) 1534 - 1539 0010-938X 2009/07 [Refereed][Not invited]
     
    Spark anodizing of titanium, Ti-6Al-4V and Ti-15V-3Al-3Cr-3Sn in alkaline aluminate electrolyte produces highly crystalline anodic films consisting mainly of Al(2)TiO(5) with alpha- and gamma-Al(2)O(3) as minor oxide phases, irrespective Of Substrate composition. However, the apparent efficiency for film formation decreases in the following order: Ti-6Al-4V, titanium and Ti-15V-3Al-3Cr-3Sn. A large amount of aluminium species are incorporated from the electrolyte, probably by plasma-chemical reaction, and become distributed throughout the film thickness. This distribution indicates that the electrolyte penetrates near to the film/substrate interface through the discharge channels. Thus, the outwardly migrating aluminium ions under a high electric field can be present even in the inner part of the anodic films. Voids are developed at the film/substrate interface. particularly on the vanadium-containing alloys, reducing the adhesion of the anodic film to the substrate. (C) 2008 Elsevier Ltd. All rights reserved.
  • T. Fujii, Y. Aoki, K. Fushimi, T. Makino, S. Ono, H. Habazaki
    J. Surf. Finish. Soc. Jpn 60 (3) 166 - 169 2009/03 [Refereed][Not invited]
  • Koji Fushimi, Shunsuke Yamamoto, Hidetaka Konno, Hiroki Habazaki
    CHEMPHYSCHEM 10 (2) 420 - 426 1439-4235 2009/02 [Refereed][Not invited]
     
    Convective mass transfer in a flowing-electrolyte-type droplet cell (f-DC) is investigated for quantitative analysis of an electrode process and precise electrofabrication of microstructures using this device. The limiting current in the f-DC was expressed theoretically and its practical equation is investigated experimentally by cyclic voltammetry in solutions containing a redox mediator. The limiting-current equation in the f-DC derived experimentally could be expressed as a sum of hydrodynamic and stagnant terms. The current derived from the latter term of the f-DC is ten times larger than that in a conventional stagnant cell, thus indicating that the convective mass transfer in the cell would be changed dramatically at a small volumetric flow rate.
  • 坂入正敏, 村田拓哉, 菊地竜也, 伏見公志
    防錆管理 日本防錆技術協会 53 (10) 361 - 366 0520-6340 2009 [Refereed][Not invited]
  • M. Ushiro, A. Yoneda, N. Iwasa, K. Fushimi, H. Konno
    TANSO 炭素材料学会 238 (238) 121 - 125 0371-5345 2009 [Refereed][Not invited]
     
    KAPTON films with and without adding small amounts of metallic compounds (0.1~2 at% as metal) were carbonized at 800~1200°C for 1 h in nitrogen and capacitance was measured in sulfate solutions by cyclic voltammetry. Nitrogen containing carbons derived from the film without additives had low specific surface area (SBET < 90 m2g−1) and the capacitance (CT) was lower than 35 F g−1. The capacitance normalized by SBET (CSP), however, reached as high as 0.77 F m−2, and decreased with decreasing nitrogen content (WN), indicating pseudocapacitance due to nitrogen. The correlation between CSP and a proportion of particular nitrogen species on the surface was not observed. Except for silicone, the addition of compounds of Fe(II), Co(II), Ni(II) and Ti(IV) increased SBET:SBET increased with increasing amount of additives. The CSP value for the products at 850°C varied depending on the additives, and the products were grouped under a) nitrogen containing carbons mainly showing pseudocapacitance due to nitrogen, b) iron containing carbons showing redox peaks, and c) carbons having relatively high SBET (around 400 m2g−1) and mainly showing the electric double layer capacitance.
  • T. Ito, M. Ushiro, K. Fushimi, K. Azumi, H. Konno
    TANSO 炭素材料学会 239 (239) 156 - 161 0371-5345 2009 [Refereed][Not invited]
     
    Hydrothermally synthesized glucose-borate complexes (mole ratio 1/1 and 1/2) were carbonized at 800–1200°C for 1 h in argon, followed by boiling in water to remove borate byproducts. Formed boron-containing carbons (B-carbons) contained 1–3.4 mass% boron and, by XPS, boron was present mainly as a form of C-B-O bonding and not as the substituted boron. The specific surface area by N2 adsorption, SBET, was 850–1360 m2 g−1, and decreased with raising heat treatment temperature. The 1/2 complex provided larger SBET than the 1/1 complex. Pore width was less than 3 nm except for the products at 1200°C. The cyclic voltammograms (CVs) at 2 mV s−1 in 1 mol dm−3 Na2SO4 were rectangular and the specific capacitance normalized by SBET, CA, was 0.05–0.1 F m−2, indicating the electric double layer capacitance. In 1 mol dm−3 H2SO4, CVs showed broad redox peaks in a potential range of 0–0.6 V vs. SCE and CA was 0.13–0.2 F m−2:the pseudocapacitance is attributed to more than two types of oxygen-containing functional groups and one of them might be =B-OH type. The electrode capacitance, CM in F g−1, in the H2SO4 solution was more than twice of the CM in the Na2SO4 solution. It may be mainly due to the difference between Na+ and H+ ions, though a certain level of pseudo-capacitance is contributing to CM. Carbons derived from a mixture of poly (vinyl alcohol) and boric acid were SBET<50 m2 g−1, suggesting that the large SBET of B-carbon is owing to the thermal decomposition behavior of glucose-borate complexes, which is different from the pore formation mechanism of the MgO template method reported.
  • Effect of PWHT on Electrochemical Behavior of Low C-13%Cr Weld Joints with the Use of a Solution Flow Type Micro-droplet Cell
    S. Hashizume, T. Nakayama, M. Sakairi, K. Fushimi
    Proc. of NACE2009 09089  2009 [Refereed][Not invited]
  • S. Saito, T. Kasashima, K. Fushimi, H. Konno
    TANSO 炭素材料学会 240 (240) 207 - 212 0371-5345 2009 [Refereed][Not invited]
     
    Si/C/O composites were formed by carbonization of Kapton type polyimide films containing 0–10 at% Si. About 24 mass% of Si was present in the composite derived from the polyimide containing 7 at% Si at 1350°C and, by 29Si MAS NMR, they were mainly Si(O)4 type components around −110 ppm with unidentifiable components in a range of −100 to −20 ppm. This composite showed the best performance of Li+ ion insertion/extraction: the coulomb efficiency was nearly 100% except for the 1st cycle and the extraction capacities were 648 mA h g−1 after 10 cycles at 50 mA g−1 and 393 mA h g−1 after 50 cycles at 500 mA g−1, and the latter was increased to ca. 470 mA h g−1 by preliminary cycles at low current densities. After 10 cycles at 50 mA g−1 the components around −110 ppm almost disappeared from the NMR spectrum and a broad and noisy band was observed in a range of −100 to −50 ppm. Since sub-micrometer fused silica particles did not react as the composites performed, the components around −110 ppm are not necessarily silica. The mechanism of reversible insertion/extraction of Li+ ion for the composites was not completely clarified, but the results by cyclic voltammetry and MAS NMR left room for doubt about an alloying/dealloying mechanism between Si and Li.
  • Hashizume, S., Nakayama, T., Sakairi, M., Fushimi, K.
    NACE - International Corrosion Conference Series 2009 [Refereed][Not invited]
  • H. Habazaki, Y. Oikawa, K. Fushimi, Y. Aoki, K. Shimizu, R. Skeldon, G. E. Thompson
    ELECTROCHIMICA ACTA 54 (3) 946 - 951 0013-4686 2009/01 [Refereed][Not invited]
     
    Niobium has been anodized at a constant current density to 10 V with a current decay in 0.8 mol dm(-3) K(2)HPO(4)-glycerol electrolyte containing 0.08-0.65 mass% water at 433 K to develop porous anodic oxide films. The film growth rate is markedly increased when the water content is reduced to 0.08 mass%; a 28 mu m-thick porous film is developed in this electrolyte by anodizing for 3.6 ks, while the thickness is 4.6 and 2.6 mu m in the electrolytes containing 0.16 and 0.65 mass% water respectively. For all the electrolytes, the film thickness changes approximately linearly with the charge passed during anodizing, indicating that chemical dissolution of the developing oxide is negligible. SIMS depth profiling analysis was carried for anodic films formed in electrolyte containing similar to 0.4 mass% water with and without enrichment of H(2) (18)O. Findings disclose that water in the electrolyte is a predominant source of oxygen in the anodic oxide films. The anodic films formed in the electrolyte containing 0.65 mass% water are practically free from phosphorus species. Reduction in water content increased the incorporation of phosphorus species. (c) 2008 Elsevier Ltd. All rights reserved.
  • Masatoshi Sakairi, Fumihito Sato, Yoshihito Gotou, Koji Fushimi, Tatsuya Kikuchi, Hideaki Takahashi
    ELECTROCHIMICA ACTA 54 (2) 616 - 622 0013-4686 2008/12 [Refereed][Not invited]
     
    A new method for maskless fabrication of metallic patterns or structures on metals is described. A solution flow type droplet cell, with co-axial dual capillaries was applied to form fine metal structures such as strips and rods. This type of droplet cell enables movement of the cell during formation. Nickel fine patterns with a width of about 200 mu m were formed on a Cu substrate. The width of the formed pattern does not change with the scanning speed of the cell, but the thickness of the formed pattern changes with the speed. Two different deposition modes were examined to form metal rods, one is a mold free deposition mode and the other is a mold assisted deposition mode. Both modes enable the formation of Ni rods. however, reproducibility of mold free deposition mode was not good. The mold assisted deposition mode has far better the reproducibility, because of the use of the inside wall of the 100 mu m diameter inner tube as the mold. It is possible to form nickel micro-rods, about 100 mu m in diameter and 12 mm long with relatively smooth surfaces by the mold assisted deposition mode. (c) 2008 Elsevier Ltd. All rights reserved.
  • H. Habazaki, T. Ogasawara, K. Fushimi, K. Shimizu, S. Nagata, T. Izumi, R. Skeldon, G. E. Thompson
    ELECTROCHIMICA ACTA 53 (28) 8203 - 8210 0013-4686 2008/11 [Refereed][Not invited]
     
    The present work demonstrates effective inhibition of field crystallization of amorphous anodic niobium oxide by incorporation of silicon species from substrate. The field crystallization, detrimental for capacitor application of niobium, occurs during anodizing of magnetron sputtered niobium at 100V in 0.1 mol dm(-3) ammonium pentaborate electrolyte at 333 K, while amorphous structure of the anodic oxide is totally retained during anodizing of magnetron sputtered Nb-12 at%Si. Even after prior thermal treatment in air, which accelerates field crystallization of anodic oxide on niobium, no crystallization occurs on the Nb-12 at%Si. Through examination of the crystallization behaviours of anodic films formed on a thin Nb-12 at%Si layer superimposed on a niobium layer as well as, on a thin niobium layer superimposed on an Nb-12 at%Si layer, it has been confirmed that air-formed oxide or thermal oxide becomes a nucleation site for crystallization. Modification of the air-formed or thermal oxide by incorporation of silicon species inhibits the nucleation of crystalline oxide. The modification, however, does not influence the growth of crystalline oxide. The growth is suppressed by continuous incorporation of silicon species into anodic film from the substrate during anodizing. (C) 2008 Elsevier Ltd. All rights reserved.
  • Masahiro Seo, Koji Fushimi, Hiroki Habazaki, Takenori Nakayama
    CORROSION SCIENCE 50 (11) 3139 - 3146 0010-938X 2008/11 [Refereed][Not invited]
     
    The effect of Pb(2+) on polarization behavior of nickel has been investigated in 0.1 M NaClO(4) + 10(-2) M HClO(4) + x M PbO solutions (x = 0, 10(-5), 10(-4), 10(-3)) at room temperature. The cyclic voltammogram has suggested that Pb(2+) degrades the stability of the passive film on Ni. The corrosion potential of Ni shifted to the more noble direction and the anodic current peak of Ni dissolution decreased with increasing Pb(2+) concentration in solution, indicating that Pb(2+) suppresses significantly the anodic dissolution. The under-potential deposition (UPD) of lead on Ni in the potential range more noble than -0.215 V (SHE) corresponding to the equilibrium potential of the Pb(2+) (10(-3) M)/Pb electrode was confirmed by XPS and GDOES analyses. The anodic Tafel slope, b(+), of Ni dissolution changed from b(+) = 40 mV decade(-1) in the absence of Pb(2+) to b(+) = 17 mV decade(-1) in the presence of 10(-4) or 10(-3) M Pb(2+), which was ascribed to the increase in active sites of Ni surface emerged as a result of electrodesorption of Pb adatoms. The roles of Pb adatoms in active dissolution and active/passive transition of Ni were discussed from the above results, (C) 2008 Elsevier Ltd. All rights reserved.
  • Kirsten Agnes Lill, Koji Fushimi, Masahiro Seo, Achim Walter Hassel
    JOURNAL OF APPLIED ELECTROCHEMISTRY 38 (10) 1339 - 1345 0021-891X 2008/10 [Refereed][Not invited]
     
    A technique named reactivity imaging is introduced. It combines optical imaging of a polycrystalline material with orientation imaging by electron back scattering diffraction (EBSD) for a determination of the crystallographic orientation map and scanning electrochemical microscopy (SECM) for a visualization of the local reactivity. Dissolving metal ions from the substrate are directly detected by the scanning Pt tip of the SECM to measure the amount of locally dissolving material. A ferritic light weight steel (alloy Fe7.5Al7Cr) with a strong anisotropic dissolution behaviour was investigated as an example. This steel shows good passivation behaviour both, in air and through anodisation. In the passive state investigated here, the difference in dissolution rate between various crystallographic orientations is only marginal. Grain boundaries on the other hand showed a higher activity as compared to the grains themselves, which is attributed to the electronic tunnelling in the grain boundaries. The results demonstrate that the rate determining step responsible for the anisotropic dissolution does not result from a deficiency in passivation but from the active dissolution kinetics.
  • M. Tauseef Tanvir, K. Fushimi, Y. Aoki, H. Habazaki
    MATERIALS TRANSACTIONS 49 (6) 1320 - 1326 1345-9678 2008/06 [Refereed][Not invited]
     
    Niobium films with isolated columnar morphology have been prepared by oblique angle magnetron sputtering for capacitor application. Anodizing of the deposited mobium to form dielectric mobium oxide reduces the surface roughness, since the gaps between the neighboring columns are filled with the oxide due to large Pilling-Bedworth ratio for Nb/Nb2O5. To increase the gaps between neighboring columns, the influences of the angle of mobium flux to substrate and substrate surface roughness on the columnar morphology of the deposited films have been investigated using scanning electron microscopy and the electrochemical measurements. The deposition on the textured rough substrate surface and at higher angle of the mobium flux from normal to the substrate surface fabricates the mobium films with higher surface roughness.
  • K. Nagahara, T. Kikuchi, K. Fushimi, M. Sakairi, H. Takahashi, T. Izumi
    J. Surf. Finish. Soc. Jpn 一般社団法人 表面技術協会 59 (5) 326 - 332 0915-1869 2008/05 [Refereed][Not invited]
     
    Cathodic polarization of niobium specimens that have been anodized galvanostatically up to Ea=100V, and then potentiostatically at Ea=100V has been investigated in a neutral borate solution. During potetiostatic cathodic polarization below Ec=−2.36V (vs. RHE) in both aerated and deaerated solutions, the cathodic current increased rapidly initially, and then increased gradually until it reached a steady value. Hydrogen gas evolution was observed during cathodic polarization below Ec=−2.36V with no formation of blisters and pits, suggesting that H+ reduction occurs mainly at the film surface. GD-OES spectra revealed that hydrogen species are enriched in the niobium substrate near the interface between anodic oxide films and the substrate at potentials below Ec=−2.36V, and that the trend is pronounced at lower potentials. Chemical shift was observed on Nb 3d and O 1s peaks in XPS spectra for the specimen at Ec=−3.36V, suggesting the formation of Nb2O3(OH)2.
    Mechanism for the reaction during cathodic polarization in a neutral solution is discussed in terms of the proton reduction at the interfaces both between oxide films / solutions and between oxide films / substrates.
  • Koji Fushimi, Hiroki Habazaki
    ELECTROCHIMICA ACTA 53 (8) 3371 - 3376 0013-4686 2008/03 [Refereed][Not invited]
     
    Anodic dissolution behavior of titanium in NaCl-containing ethylene glycol has been examined to obtain electropolished titanium surface. During anodic polarization in 1 mol dm(-3) NaCl ethylene glycol solution at 293 K, the titanium electrode covered with oxide dissolves with gas evolution at potentials higher than 10 V (Ag/AgCl) while it is in passive state at potentials lower than 5 V. However, after removal of the oxide layer by pre-polarization at gas-evolving potentials, no gas evolution is observed, and the titanium electrode shows a limiting dissolution current as tetravalent species at potentials higher than 5 V, producing a smooth surface. The polarization of the rotating disk titanium electrode reveals that the kinetics of the mass transfer reaction for electropolishing of titanium is controlled by titanium species dissolved into the solution, not by chloride ions or water containing in the solution. Repetition of dynamic polarization gives a well-electropolished surface. (C) 2007 Elsevier Ltd. All rights reserved.
  • Koji Fushimi, Atsushi Naganuma, Kazuhisa Azumi, Yuuzo Kawahara
    CORROSION SCIENCE 50 (3) 903 - 911 0010-938X 2008/03 [Refereed][Not invited]
     
    Galvanic corrosion of carbon steel welded with type-309 stainless steel in NaCl Solution was tentatively evaluated with a newly developed multi-channel electrode technique in which the welded specimen was divided into nine working electrodes (WEs), reconstructed in resin, and connected individually to an imaginary ground level of an electric circuit via relay switches. This allows the WEs to join a galvanic couple and simultaneous measurement of participating current or open circuit potential of each WE. WEs were immersed together in 5.1 x 10(2) mol dm(-3) or 2.1 x 10(-4) mol dm(-3) NaCl solutions, and spatial distribution of participating currents and open circuit potentials were monitored as a function of immersion time. The WE of the weldment acted as a cathode throughout the immersion period, while the other WEs of base steel became anodes or cathodes depending on their location, immersion time and concentration of the electrolyte solution. The ability of zinc-rich paint to protect the welded specimen as sacrificial anode was also investigated. (C) 2007 Elsevier Ltd. All rights reserved.
  • Kiriu, M., Fushimi, K., Konno, H., Habazaki, H.
    Electrochemistry 76 (3) 2008
  • Y. Oikawa, K. Fushimi, Y. Aoki, H. Habazaki
    ECS Transactions 16 (3) 345 - 351 1938-5862 2008 [Refereed][Not invited]
     
    Porous anodic films have been developed on niobium at constant formation voltages between 5 and 50 V in glycerol electrolyte containing 0.8 mol dm -3 dibasic potassium phosphate at 433 K. Except at the formation voltage of 5 V, at which the current density is approximately constant during anodizing, the current shows the minimum and then maximum. After the current maximum, the current density decreases gradually, which follows the Cottrell equation. Thus, diffusion of some species in the pores should control the growth rate of the anodic films. The porous films developed are practically Nb 2O5 with a small amount of carbon contamination. Incorporation of phosphorus species, which often occurs in aqueous electrolytes, is negligible at all the formation voltages in the present electrolyte. Based on the results obtained, the growth process of the porous anodic films on niobium in this hot organic electrolyte is discussed. © The Electrochemical Society.
  • Hashizume, S., Nakayama, T., Sakairi, M., Fushimi, K.
    NACE - International Corrosion Conference Series 081021 - 0810216 2008 [Refereed][Not invited]
  • M. Seo, N. Kikuchi, K. Fushimi, H. Habazaki, T. Narita, T. Nakayama
    ECS Transactions 16 (52) 109 - 116 1938-5862 2008 [Refereed][Not invited]
     
    The anodic behavior of nickel has been investigated in deaerated acidic perchlorate solution containing 10-4 M Pb2+ at room temperature. The addition of Pb2+ in solution shifted the corrosion potential or the potential of anodic current peak to the more noble direction and suppressed the anodic dissolution of nickel. The Tafel slope of anodic dissolution decreased from 37 mV decade-1 to 13 mV decade -1 due to the addition of Pb2+. The uderpotential deposition (UPD) of Pb on nickel was discussed with relation to the effect of Pb2+ on anodic behavior of nickel. ©The Electrochemical Society.
  • K. Fushimi, K. Takakura, H. Habazaki, H. Konno, K. Azumi, S. Tsuri
    ECS Transactions 16 (52) 291 - 296 1938-5862 2008 [Refereed][Not invited]
     
    The combination of the potentiometric pH measurement and potentiostatic polarization was carried out for the type-312L and 316L austenitic stainless steels during decreasing pH by dropping hydrochloric acid in sodium chloride solution. The acidification changed the surface condition of the austenitic stainless steels. The significant acidity of the solution induced a rapid increase in the anodic current passing through the steel at a critical pH, pHdepass. The value of pHdepass was increased by elevating the solution temperature or concentrating the chloride ions in solution. In the potential - pHdepass diagram, the surface condition could be classified into four domains immunity, active, passive and transpassive/pitting states. The boundary between the active and passive states was strongly dependent on solution pH but independent of potential, indicating that the depassivation of the steel surface proceeded with a chemical reaction participating protons rather than the electrochemical one. ©The Electrochemical Society.
  • T. Yamamoto, K. Fushimi, H. Habazaki, H. Konno, S. Miura
    ECS Transactions 16 (52) 133 - 140 1938-5862 2008 [Refereed][Not invited]
     
    The effects of grain orientation and cold-rolling on the depassivation-repassivation behavior of polycrystalline irons were examined in pH8.4 borate buffer solution using in-situ micro-indentation technique. The depassivation rate on the passive iron surface during the downward drive of the indenter (penetration of an indenter tip into iron surface) depended on the grain orientation the highest rate was obtained on {100} surface, on which a possible main slip plane of {110} was normal to the surface. In contrast, the total electric charge required for repassivation during the downward and subsequent upward drives was not influenced by the grain orientation. The electric charge for repassivation was strongly influenced by the rolling reduction that changed the dislocation density at the specimen surface. There was a linear correlation between the electric charge normalized by residual dent area and the square root of the dislocation density. ©The Electrochemical Society.
  • M. Sakairi, T. Nakayama, T. Kikuchi, S. Hashizume, K. Fushimi
    ECS Transactions 16 (52) 281 - 290 1938-5862 2008 [Refereed][Not invited]
     
    Low Carbon- 13 mass% Cr martensitic stainless steels have been widely used for line pipe application because of their high strength and excellent corrosion resistance in corrosive conditions. Newly developed solution flow type micro-droplet cell was applied to investigate electrochemical behavior of heat affected zone (HAZ) of 13 mass% Cr stainless steel. This technique makes it possible to measure electrochemical behavior of very narrow area of HAZ. Effects of solution pH and stress on corrosion potentials, and current at constant potential for HAZ portion of welded joints were focused. The corrosion potentials at HAZ and base metal show almost same tendency, however, current change shows clear difference of corrosion resistance at HAZ and base metal. ©The Electrochemical Society.
  • 環境・表面処理と微小電気化学の接点
    伏見公志
    表面技術協会北海道支部：2008年夏季セミナー資料 11 - 15 2008 [Not refereed][Not invited]
  • H. Habazaki, M. Yamasaki, T. Ogasawara, K. Fushimi, H. Konno, K. Shimizu, T. Izumi, R. Matsuoka, P. Skeldon, G. E. Thompson
    THIN SOLID FILMS 516 (6) 991 - 998 0040-6090 2008/01 [Refereed][Not invited]
     
    Thermal treatment of anodized niobium and oxygen-containing niobium has been carried out to elucidate the thermal degradation mechanism of niobium, capacitors and to clarify the influence of oxygen dissolved in niobium. on thermal degradation. The capacitance and leakage current of the anodized specimens increase with thermal treatment above 423 K in air, although the oxygen content in the substrate has no significant effect up to 523 K. At increased temperatures, the changes in capacitance and leakage current are suppressed with increasing oxygen content. The anodic film formed on the Nb-50 at.% O substrate thickens significantly during thermal treatment at 623 K in air, while only a slight reduction of the thickness is evident for those on the niobium and Nb-20 at.% O substrates. In contrast, vacuum thermal treatment at 623 K causes thinning of the anodic film on niobium, with evidently no change in the film thickness on the Nb-50 at.% 0 substrate. These are interpreted in terms of oxygen diffusion from the anodic film to the substrate as well as thermal oxide growth. (C) 2007 Elsevier B.V. All rights reserved.
  • Koji Fushimi, Shunsuke Yamamoto, Ryota Ozaki, Hiroki Habazaki
    ELECTROCHIMICA ACTA 53 (5) 2529 - 2537 0013-4686 2008/01 [Refereed][Not invited]
     
    The scanning-droplet-cell (SDC), recently used for studying electrochemistry of electrodes in micro-areas, was modified to a flowing electrolyte type one (f-SDC), in which fresh electrolyte was continuously supplied oil the surface to be examined. The f-SDC with a coaxial double capillary structure could avoid the contamination of electrolyte by species dissolved front the measuring electrode surface. In the present study, the f-SDC technique was applied successfully to obtain profiles of the corrosion potential for the cross-sections of aluminium-alloy brazing sheets, used for the heat exchanger of the automobile. The brazing sheets consist of an Al-Zn alloy sacrificial anode layer, an Al-Mn-Cu core layer and an Al-Si brazing filler. The profiles of the corrosion potential, important to evaluate the corrosion protection performance of the sacrificial anode, revealed that the potential gradient arising from the sacrificial anode to the core layer is mainly controlled by zinc, which diffuses from the former layer to the latter during the cladding treatment and the post-heat treatment. (c) 2007 Elsevier Ltd. All rights reserved.
  • H. Habazaki, Y. Oikawa, K. Fushimi, K. Shimizu, S. Nagata, P. Skeldon, G. E. Thompson
    ELECTROCHIMICA ACTA 53 (4) 1775 - 1781 0013-4686 2007/12 [Refereed][Not invited]
     
    Porous anodic films, with pore size of similar to 10 nm, have been developed by anodizing of magnetron sputtered Ti-25 at. % Si alloy at constant formation voltages in glycerol electrolyte containing dibasic potassium phosphate at 433 K. The films, of amorphous structure, contain titanium and silicon species, as units of TiO(2) and SiO(2), throughout the film thicknesses, with negligible amounts of phosphorus species. The silicon is enriched in the film relative to the composition of the alloy, the level of enrichment suggesting that anion migration is increased in comparison with amorphous film growth at ambient temperature. In contrast to the behaviour of the alloy, essentially barrier films were formed on commercially pure titanium in the glycerol electrolyte, when a main anodic reaction was generation of oxygen, which was probably promoted by the development of anatase. (c) 2007 Elsevier Ltd. All rights reserved.
  • M. Tauseef Tanvir, K. Fushimi, K. Shimizu, S. Nagatac, P. Skeldon, G. E. Thompson, H. Habazaki
    ELECTROCHIMICA ACTA 52 (24) 6834 - 6840 0013-4686 2007/08 [Refereed][Not invited]
     
    Amorphous anodic titania, stabilised by incorporation of silicon species, is shown to grow to high voltages on sputter-deposited, single-phase Ti-Si alloys during anodizing at a constant current density in ammonium pentaborate electrolyte. The films comprise two main layers, with silicon species confined to the inner layers. An amorphous-to-crystalline transition occurs at similar to 60V on the Ti-6 at.% Si alloy, while the transition is suppressed to voltages above 140 V on alloys with 12 and 26 at.% silicon. The crystalline oxide, nucleated at a depth of similar to 40% of the film thickness, is associated with the presence of a precursor of crystalline oxide in the pre-existing air-formed oxide. The modified structure of the air-formed oxide due to increased incorporation of silicon species suppresses the amorphous-to-crystalline transition until the onset of dielectric breakdown. The transport numbers of cations and anions during growth of the anodic oxides are independent of the concentration of silicon species in the inner layer, despite the marked change in the field strength. (c) 2007 Elsevier Ltd. All rights reserved.
  • H. Habazaki, T. Onodera, K. Fushimi, H. Konno, K. Toyotake
    SURFACE & COATINGS TECHNOLOGY 201 (21) 8730 - 8737 0257-8972 2007/08 [Refereed][Not invited]
     
    Spark anodizing of a bcc solid solution Ti-15% V-3% Al-3% Cr-3% Sn alloy has been performed in an alkaline electrolyte containing aluminate and phosphate using dc-biased ac anodizing to form a wear-resistant coating on the alloy. The coating consists mainly of Al2TiO5, with rutile and gamma-Al2O3 being present as minor oxide phases. Depth profiles of the coating, examined by glow discharge optical emission spectroscopy, have revealed that aluminium species, highly enriched in the coating, distribute uniformly in the coating, while phosphorus species, incorporated from the electrolyte, are located mainly in the inner part of the coating near the coating/alloy interface. The location of the phosphorus species should be associated with the porous nature of the coating, allowing access of the electrolyte directly to the inner parts of the coating. The porosity of the coating is reduced by anodizing to high voltages. The marked improvement of the wear resistance by the coating has been demonstrated from a pin-on-disc wear test. (c) 2006 Elsevier B.V. All rights reserved.
  • Koji Fushimi, Takatoshi Yamamoto, Kazuhisa Azumi, Masahiro Seo, Hiroki Habazaki
    ELECTROCHIMICA ACTA 52 (24) 6901 - 6910 0013-4686 2007/08 [Refereed][Not invited]
     
    During in situ micro-indentation of passive iron in pH 8.4 borate solution, a couple of anodic current peaks emerged; the first peak during loading and the second peak during unloading. The current transients, associated with rupture and repair of the passive film, were influenced by the indentation conditions. For instance, the current peak height, the cur-rent peak area and the time required for complete repassivation are strongly dependent on indentation rate. A numerical model was proposed to correlate the current transient during loading with mechanical deformation of the passive surface. The comparison between the current transient measured experimentally and that estimated from the load transient suggested that the ruptured area of passive film was about 10% of the surface area deformed by the contact with the indenter. (c) 2007 Published by Elsevier Ltd.
  • Takatoshi Yamamoto, Koji Fushimi, Masahiro Seo, Shiro Tsuri, Tetsuo Adachi, Hiroki Habazaki
    ELECTROCHEMISTRY COMMUNICATIONS 9 (7) 1672 - 1676 1388-2481 2007/07 [Refereed][Not invited]
     
    Micro-indentation test was performed for passive iron surface in deaerated pH 8.4 borate solution to correlate the passive film breakdown with mechanical deformation of substrate. Loading and unloading of a conical micro-indenter to the passive surface were repeated 10 times at an identical position. Elastic-plastic deformation occurred during the first indentation, while elastic deformation is predominant during the second and following indentations. The anodic current appears at the commencement of the first loading, with the maximum current generated at the maximum load. A more obvious current peak appears when the indenter just lost the contact with the iron surface during the first unloading. The current peaks observed during the subsequent indentations decreased markedly compared with the first indentation. Thus, the passive film breakdown by elastic deformation of iron substrate is less significant compared with that by plastic deformation under the present conditions. There is a linear correlation between the electric charge required for repassivation of the ruptured passive film and the work for plastic deformation. (C) 2007 Elsevier B.V. All rights reserved.
  • H. Habazaki, K. Fushimi, K. Shimizu, P. Skeldon, G. E. Thompson
    ELECTROCHEMISTRY COMMUNICATIONS 9 (5) 1222 - 1227 1388-2481 2007/05 [Refereed][Not invited]
     
    The rapid inward migration of fluoride ions in growing anodic titanium oxide under a high electric field has been elucidated by anodizing a Ti-12 at% silicon alloy, where film growth proceeds at nearly 100% efficiency in selected electrolytes. Further, incorporated silicon species in the anodic film are immobile, acting as marker species. The migration rate of fluoride ions is determined precisely by three-stage anodizing, consisting of initial anodic film formation at a constant current density to 50 V in ammonium pentaborate electrolyte, subsequent incorporation of fluoride ions by reanodizing to 55 V in ammonium fluoride electrolyte and, finally, anodizing again in ammonium pentaborate electrolyte at high current efficiency. The resultant films were analyzed by glow discharge optical emission spectroscopy to reveal the depth distribution of fluoride ions and the location of the silicon marker species. The fluoride ions migrate inward at twice the rate of O2- ions. Consequently, anodizing of titanium in fluoride-containing electrolytes develops a fluoride-rich layer that separates the alloy substrate from the anodic oxide, with eventual detachment of the film from the substrate. (c) 2007 Elsevier B.V. All rights reserved.
  • Koji Fushimi, Kirsten A. Lill, Hiroki Habazaki
    ELECTROCHIMICA ACTA 52 (12) 4246 - 4253 0013-4686 2007/03 [Refereed][Not invited]
     
    Corrosion behavior of Fe-3 at.% Si alloy in 0.01 mold m(-3) HCl solution was investigated by using scanning electrochemical microscopy (SECM) as well as general electrochemistry. The rate of corrosion coupled with hydrogen evolution was initially 0.44 A m(-2) but decreased significantly with time. Localized hydrogen evolution on the specimen surface was probed by an SECM system in which a force sensor was mounted to determine the probe height from the specimen surface. SECM images revealed that hydrogen evolution took place heterogeneously on the specimen surface depending on crystallographic orientation of substrate single grains in the initial stage and then became relatively homogeneous. Finally, a heterogeneous hydrogen distribution corresponding to the appearance of localized corrosion sites was observed. (c) 2006 Elsevier Ltd. All rights reserved.
  • Repassivation Current Transient from Iron Surface during Downward Micro-indentation in pH 8.4 Borate Solution
    K. Fushimi, T. Yamamoto, M. Seo, H. Habazaki
    Proceedings of EUROCORR 2007 (CD-ROM) 1227  2007 [Refereed][Not invited]
  • Investigations on the local electrochemical behavior of welded stainless steels with solution flow type micro-droplet cell
    T. Nakayama, M. Sakairi, K. Fushimi, S. Hashizume
    Proceedings of EUROCORR 2007 (CD-ROM) 1130  2007 [Refereed][Not invited]
  • Koji Fushimi, Martin Stratmann, Achim Walter Hassel
    ELECTROCHIMICA ACTA 52 (3) 1290 - 1295 0013-4686 2006/11 [Refereed][Not invited]
     
    The electropolishing of NiTi shape memory alloys was surveyed electrochemically. Anodic polarization of NiTi up to 8 V was performed in various aqueous and methanolic H2SO4 solutions. The passivity could be overcome in methanolic solutions with 0.1 mol dm(-3) <= C-H2SO4 <= 7 mol dm(-3). The dissolution kinetics was studied in dependence of the polarization potential, the H2SO4-concentration, the water concentration and the temperature. For lower concentrations of sulfuric acids (C-H2SO4 <= 0.3 mol dm(-3))electropolishing conditions were not observed for potentials up to 8 V. The dissolution remained under Ohmic control. In the concentration range from I to 7 mol dm(-3) a potential independent limiting current was registered depending linearly on the logarithm of concentration. The best results were obtained with a 3 mol dm(-3) methanolic sulfuric acid at 263 K which yielded an electropolishing current of 500 A m(-2) at a potential of 8 V. Surface roughness as well as current efficiency showed an optimum under these conditions. (c) 2006 Elsevier Ltd. All rights reserved.
  • H. Habazaki, K. Fushimi, H. Konno, K. Shimizu, K. Asami, P. Skeldon, G.E. Thompson
    J. Surf. Finish. Soc. Jpn The Surface Finishing Society of Japan 57 (9) 676 - 678 0915-1869 2006/09 [Refereed][Not invited]
  • K. Fushimi, A. Naganuma, K. Azumi, M. Seo
    J. Surf. Finish. Soc. Jpn 一般社団法人 表面技術協会 57 (8) 592 - 596 0915-1869 2006/08 [Refereed][Not invited]
     
    Fabrication of the micro-disk electrode probe, which is convenient for micro-electrochemistry of localized surfaces or in small amounts of solution, has required special equipment or technical skills. In order to fabricate a micro-disk electrode probe simply, nickel electroless plating in a glass pipette was applied. After activation of the inside of a glass pipette heated and pulled off, nickel electroless-plating solution was successively introduced to deposit nickel in the pipette. Polishing the tip of the pipette and/or electroplating Ni, Cu or Pt obtained a disk surface with a diameter less than a few tens of micrometers. Cyclic voltammetry of the disk electrode showed a sigmoid curve and gave a limiting current which was identical with the theoretical value as a micro-disk electrode, indicating that this method was promising for fabrication of micro-disk electrodes. The electroless-plating micro-disk electrode was employed as a probe for scanning electrochemical microscopy to demonstrate its performance.
  • Koji Fushimi, Ken-ichi Takase, Masahiro Seo
    Passivation of Metals and Semiconductors, and Properties of Thin Oxide Layers 451 - 456 2006 [Refereed][Not invited]
     
    This chapter presents a study in which microindentation in solution is performed to a polycrystalline iron surface kept at passive state to measure the current transients in the order of 10-9 A. A polycrystalline iron plate with a purity of above 99.99% is used, which is mechanically polished with a diamond paste and ultrasonically cleaned in ethanol. A conical diamond indenter with an including angle of c.a. 110° is employed for microindentation. For the indentation in solution, the diamond indenter attached to a force sensor is normally moved downward and upward with a piezoelectric-driving system to the passive iron surface kept at constant potential. The increase in potential accelerates the peak currents during the micro-indentation, due to electrochemical effect. The influences of sulfate ions in solution on the current peaks are also investigated and it is stressed that the mechanical and electrochemical interactions, i.e., mechano-electrochemical effects worked for repassivation at the ruptured sites of passive film during indentation. © 2006 Elsevier B.V. All rights reserved.
  • Effect of GGBS on Membrane Potential of Pastes
    Y. Elakneswaran, T. Nawa, K. Kurumisawa, K. Fushimi
    RILEM Proceedings PRO 46, Concrete Durability and Service Life Planning (ConcreateLife’06) 405 - 414 2006 [Refereed][Not invited]
  • Surface Charge of Hardened Cement Paste Determined by Membrane Potential
    Yogarajah Elakneswaran, Toyoharu Nawa, Kiyofumi Kurumisawa, Koji Fushimi
    Cement Science and Concrete Technology 60 111 - 117 2006 [Refereed][Not invited]
  • K Fushimi, K Takase, K Azumi, M Seo
    ELECTROCHIMICA ACTA 51 (7) 1255 - 1263 0013-4686 2006/01 [Refereed][Not invited]
     
    Micro-indentation test of passive iron electrode in deaerated pH 8.4 borate buffer solution was carried out to investigate the rupture and repair of passive film. During driving a conical diamond micro-indenter with a load of 0.1 N order downward to the electrode and driving upward from the electrode, a couple of anodic current peaks were observed. The first current peak spiked during loading was responsible for partial exposure of iron substrate to the solution due to rupture of the passive film when the indenter tip contacted. The second peak emerged during unloading when elastic deformation recovered, which was ascribed to repair at the ruptured sites. The second peak current was larger than the first one. Both peaks were sensitively influenced by electrode potential or concentration of sulfate ions containing in solution. The model for a series of rupture and repair processes of the passive film by micro-indentation was proposed to discuss the current transients. (C) 2005 Elsevier Ltd. All rights reserved.
  • K. Fushimi, K. Takase, K. Azumi, M. Seo
    ECS Transactions 1 (4) 367 - 378 1938-5862 2005 [Refereed][Not invited]
     
    Micro-indentation test of passive iron surface in pH 8.4 borate buffer solution was carried out to analyze current transients corresponding to the rupture and repair of passive film. During driving a conical diamond micro-indenter downward to the passive surface and driving upward from the surface, a couple of anodic current peaks were observed. The first current peak spiked during loading was responsible for partial exposure of iron substrate to the solution due to rupture of the passive film when the indenter tip deformed the substrate and penetrated. The second peak emerged during unloading when elastic deformation of the substrate recovered, which was ascribed to repair at the ruptured sites. The second peak current was larger than the first one. Both peaks were sensitively influenced by electrode potential or concentration of sulfate ions containing in solution. The model for a series of rupture and repair processes of the passive film by micro-indentation was proposed to discuss the current transients. copyright The Electrochemical Society.
  • K Fushimi, K Ammi, M Seo
    ELECTROCHEMISTRY COMMUNICATIONS 6 (9) 959 - 963 1388-2481 2004/09 [Refereed][Not invited]
     
    Voltammetry of a microelectrode that vibrated ultrasonically in a lateral direction showed some unique electrochemical phenomena coupled with hydrodynamics. Vibration of the microelectrode increased the current flowing through the microelectrode at definite frequencies. At the definite frequencies, the approach of the vibrating microelectrode to an insulator surface also increased the current with decreasing distance in the vicinity of the insulator, phenomena that were ascribed to deformation of the diffusion layer on the electrode due to motion of the solution. (C) 2004 Elsevier B.V. All rights reserved.
  • Fushimi, K.
    Zairyo to Kankyo/ Corrosion Engineering 53 (3) 121 - 122+i 2004 [Refereed][Not invited]
  • F Falkenberg, K Fushimi, M Seo
    CORROSION SCIENCE 45 (11) 2657 - 2670 0010-938X 2003/11 [Refereed][Not invited]
     
    A new method allowing simultaneous measurements of anodic currents and small mass changes during initiation and early growth of a single localised corrosion site was discussed. An electrochemical quartz crystal microbalance (EQCM) was combined with a liquid-phase ion gun consisting of an Ag/AgCl microelectrode which produces chloride ions, causing local breakdown of passive film and pit growth. The method was applied to copper thin films polarised anodically at 0.6 or 0.8 V (SHE) in pH 8.4 borate buffer solution. It was found from comparison between coulometry and gravimetry that copper dissolves as Cu2+ during the pit growth. The shape of the pit was almost circular and the average pit current density, i(p) = 25 A cm(-2) was evaluated from the kinetics of 2D pit growth. (C) 2003 Elsevier Ltd. All rights reserved.
  • Passive Film Formed on Shape Memory NiTi Alloy in Sulfuric Acid
    K. Fushimi, A. W. Hassel, M. Stratmann
    Proceedings of 13th Asian-Pacific Corrosion Control (CD-ROM) L-06  2003 [Refereed][Not invited]
  • K Fushimi, T Yamamuro, M Seo
    CORROSION SCIENCE 44 (3) 611 - 623 0010-938X 2002/03 [Refereed][Not invited]
     
    A galvanic coupling with a single crystal magnetite accelerated the corrosion of a carbon steel in sulfate solutions. A scanning electrochemical microscopic investigation revealed that the hydrogen generation on the magnetite as well as the reduction of the magnetite itself was contributed to a galvanic corrosion of the carbon steel. The estimated current efficiency for the hydrogen generation on the magnetite was about 50% in pH 5.8 sulfate solution. Moreover, the distribution of hydrogen generated above the magnetite surface was observed with the probe current image. (C) 2002 Elsevier Science Ltd. All rights reserved.
  • K. FUSHIMI, M. SEO
    Materia Japan 公益社団法人 日本金属学会 41 (12) 856 - 857 1340-2625 2002 [Refereed][Not invited]
  • Susceptibility to Local Breakdown of Passive Film Formed on Iron
    K. Fushimi, M. Seo
    Proceedings of the International Symposium "Corrosion and Corrosion Protection", ed. by J. D. Sinclair, E. Kalman, M. W. Kendig, W. Plieth, W. H. Smyrl, Electrochemical Society PV2001 (22) 325 - 332 2002 [Refereed][Not invited]
  • K Fushimi, M Seo
    ISIJ INTERNATIONAL 42 (12) 1326 - 1333 0915-1559 2002 [Refereed][Not invited]
     
    Scanning electrochemical microscopy (SECM) is powerful to investigate non-homogeneity of surface reaction in solution. It is useful for evaluating the distribution of electrochemical reactions taking place on the electrode surface such as corrosion reaction, redox reaction on passive film and so on. The heterogeneous electrochemical reaction on polycrystalline iron, titanium and single crystal magnetite electrode surfaces were discussed. SECM can be also employed for inducing locally a certain surface electrochemical reaction on the specimen by operating a probe electrode as liquid-phase ion gun (LPIG). The application of LPIG to the passive film formed on iron for inducing the local film breakdown has revealed the details of its local breakdown process.
  • K Fushimi, M Seo
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 148 (11) B450 - B456 0013-4651 2001/11 [Refereed][Not invited]
     
    A small amount of Cl- could be locally generated from a liquid-phase ion gun (LPIG), which consists of a silver microelectrode covered with silver chloride, by cathodic polarization. The LPIG was employed to induce the local breakdown of the passive films formed on iron in deaerated borate solutions. The concentration of Cl- generated locally on the passivated iron surface was estimated to be about 1 mol dm(-3) from the measurement of the potential difference between the narrow space enriched with Cl- and bulk solution. The induction period, t(BD), was required for initiation of local breakdown. A longer induction period was needed for initiation of local breakdown of the thicker passive films with the lower electric field. The structural changes of passive films due to Cl- before initiation of local breakdown are discussed. Moreover, the induction period depended on the substrate grain orientation, which is explained in terms of difference in thickness or defect structure of passive films on substrate grains. (C) 2001 The Electrochemical Society.
  • 伏見公志
    腐食防食シンポジウム資料 134th 29 - 37 2001/09/28 [Not refereed][Not invited]
  • K Fushimi, M Seo
    ELECTROCHIMICA ACTA 47 (1-2) 121 - 127 0013-4686 2001/09 [Refereed][Not invited]
     
    The dissolution of iron as ferrous or ferric ion from a polycrystalline iron electrode during anodic polarization in pH 2.3 sulfate solution was evaluated by using scanning electrochemical microscopy (SECM). A graphite reinforcement carbon (GRC) microelectrode was employed as a probe electrode of SECM to detect ferrous or ferric ions dissolved from the iron electrode in the active-dissolution, passive or trans-passive region. The probe current above the iron electrode surface subjected to active-dissolution showed the dissolution distribution of ferrous ion, depending on the substrate grains. It was found that the active-dissolution rate of iron as ferrous ions from the grain on which the thicker film was formed in the passive region, was lower than that from the grain on which the thinner film was formed in the passive region. (C) 2001 Elsevier Science Ltd. All rights reserved.
  • K Fushimi, T Okawa, M Seo
    ELECTROCHEMISTRY 68 (12) 950 - 954 1344-3542 2000/12 [Refereed][Not invited]
     
    A scanning electrochemical microscopic (SECM) observation of oxygen evolution on a polycrystalline titanium electrode during anodic oxidation in 0.1 mol dm(-3) H2SO4 was attempted to evaluate the heterogeneity of the electrode surface. The micro probe electrode, which was scanned above the titanium electrode surface, could detect oxygen evolved in parallel with the formation of anodic oxide film. The probe current image corresponding to the distribution of oxygen evolution was in good agreement with the conventional probe current image measured in pH 8.4 berate solution containing K4Fe(CN)(6), indicating that the oxygen evolution took place preferentially on the substrate grain covered with the thinner oxide film. It is shown that the SECM measurement of oxygen detection is useful for in-situ evaluation of the heterogeneity of anodic oxide film on the metal electrode during anodic oxidation.
  • K Fushimi, T Okawa, M Seo
    ELECTROCHEMISTRY 公益社団法人 電気化学会 68 (12) 950 - 954 1344-3542 2000/12 [Refereed][Not invited]
     
    A scanning electrochemical microscopic (SECM) observation of oxygen evolution on a polycrystalline titanium electrode during anodic oxidation in 0.1 mol dm(-3) H2SO4 was attempted to evaluate the heterogeneity of the electrode surface. The micro probe electrode, which was scanned above the titanium electrode surface, could detect oxygen evolved in parallel with the formation of anodic oxide film. The probe current image corresponding to the distribution of oxygen evolution was in good agreement with the conventional probe current image measured in pH 8.4 berate solution containing K4Fe(CN)(6), indicating that the oxygen evolution took place preferentially on the substrate grain covered with the thinner oxide film. It is shown that the SECM measurement of oxygen detection is useful for in-situ evaluation of the heterogeneity of anodic oxide film on the metal electrode during anodic oxidation.
  • K Fushimi, T Okawa, K Azumi, M Seo
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 147 (2) 524 - 529 0013-4651 2000/02 [Refereed][Not invited]
     
    A scanning electrochemical microscope (SECM) was applied to study anodic oxide film grown on a polycrystalline titanium electrode in deaerated pH 8.4 borate solution. The probe current images of SECM could detect the heterogeneous growth of anodic oxide film, depending on the substrate crystal grains. This heterogeneity increased with increasing the film formation potential at the potential higher than 3 V (SHE). The study of the dependence of film thickness on the substrate grain has been also supported with Raman microprobe spectroscopy. (C) 2000 The Electrochemical Society. S0013-4651(99)06-131-5. All rights reserved.
  • K Fushimi, K Azumi, M Seo
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 147 (2) 552 - 557 0013-4651 2000/02 [Refereed][Not invited]
     
    A silver/silver chloride microelectrode was developed as a liquid-phase ion gun for investigation of precursor processes of pitting corrosion. This electrode was set as a probe electrode of a scanning electrochemical microscope and used to induce a local breakdown of passive film on iron. A small amount of chloride ions generated by cathodic polarization of the silver/silver chloride microelectrode has succeeded in inducing the local breakdown of the passive film formed on iron in deaerated pH 6.5 berate solution. Moreover, the microelectrode could detect ferric ions dissolved from the film at the initial stage of the film breakdown. (C) 2000 The Electrochemical Society. S0013-4651(99)05-038-7. All rights reserved.
  • K Fushimi, M Seo
    LOCALIZED IN-SITU METHODS FOR INVESTIGATING ELECTROCHEMICAL INTERFACES 99 (28) 362 - 369 2000 [Refereed][Not invited]
     
    Amount of Cl- ions needed for initiating the local breakdown of passive film on iron electrode was investigated by a liquid-phase ion-gun which was a microelectrode consisting of a silver/silver chloride. The small amount of Cl- ions generated by a cathodic polarization of the silver/silver chloride microelectrode has succeeded in inducing the local breakdown of the passive film formed on iron in deaerated borate solution. The less amount of Cl- ions was needed for initiating the local breakdown of the thinner or more defective film, the film with the higher electric field or in the lower pH berate solution.
  • AW Hassel, K Fushimi, T Okawa, M Seo
    LOCALIZED IN-SITU METHODS FOR INVESTIGATING ELECTROCHEMICAL INTERFACES 99 (28) 166 - 174 2000 [Refereed][Not invited]
     
    An improved type of the scanning droplet cell (SDC) was constructed with a tip size of 100 mu m. It was used to form a 2 x 3 pattern of 100 mu m oxide spots on a single grain of a polycrystalline titanium specimen. The crystallographic orientation of the grain was determined by a scanning micro Laue method to be near-XXXO with an angle of 12 degrees between mean axis and surface normal. The distance between these spots was 100 mu m or less. All oxide spots had different oxide thicknesses resulting from the different polarisation potentials (3 to 8 V-(Ag/AgCl)) The inhomogeneity of the surface reactivity was then evaluated by using a SECM. Size, share and position of the pattern could be clearly monitored with SECM current images. Differences in the reactivity due to the differences in oxide thickness could be determined as well.
  • AW Hassel, K Fushimi, M Seo
    ELECTROCHEMISTRY COMMUNICATIONS 1 (5) 180 - 183 1388-2481 1999/05 [Refereed][Not invited]
     
    A miniaturised Ag \ AgCl reference electrode is described which can be easily set up. Its elechochemical behaviour was proven by micropolarisation curves, electrochemical impedance spectroscopy and potential transients. A saturated potassium chloride solution was used which was solidified by adding agar. The electrode is as small as 800 mu m in diameter and 5 mm in length, with further potential for down-sizing. A modified version includes an agar salt bridge in the same capillary. After an induction period of 6 h the potential becomes stable within 1 mV for more than 6 weeks. The electrode shows a slightly different reference potential, which is discussed in terms of the production process. (C) 1999 Elsevier Science S.A. All rights reserved.
  • K Fushimi, K Azumi, M Seo
    ISIJ INTERNATIONAL 39 (4) 346 - 351 0915-1559 1999 [Refereed][Not invited]
     
    Scanning electrochemical microscopy (SECM) was applied to evaluate the heterogeneity of a passive film formed on a pure iron electrode in deaerated pH 8.4 berate solution. A probe current image of SECM was measured with a tip-generation/substrate-collection (TG/SC) mode in deaerated pH 8.4 berate solution containing 0.03 mol dm(-3) Fe(CN)(6)(4-) as a mediator. The difference in thickness of passive films formed on two iron plates at different potentials could be evaluated from the probe current image. The probe current image of the passivated iron surface with distinctive crystal grains was composed of the patch patterns, the shapes of which coincided completely with the shapes of the substrate crystal grains. The probe current flowed above the grain surface oriented to {100} plane was less than that above the grain surface oriented to {110} or {111} plane. The grain orientation dependence of probe current was ascribed to the difference in thickness of passive films formed on the crystal grains.
  • K Fushimi, K Azumi, M Seo
    PROCEEDINGS OF THE SYMPOSIUM ON CRITICAL FACTORS IN LOCALIZED CORROSION III 98 (17) 626 - 634 1999 [Refereed][Not invited]
     
    An ion gun in liquid phase for the investigation of precursor processes of pitting corrosion was realized by using a silver/silver chloride microelectrode, It was used to induce a local breakdown of the passive film on iron. This electrode was set as a probe electrode of a scanning electrochemical microscope (SECM). A small amount of chloride ions was generated by cathodic polarization of the silver/silver chloride microelectrode and induced the local breakdown of the passive film formed on iron in deaerated pH 6.5 borate buffer solution. Moreover. the microelectrode could detect ferric ions dissolved at the initial stage of film breakdown.
  • 瀬尾真浩, 伏見公志
    腐食防食シンポジウム資料 122nd 59 - 66 1999 [Not refereed][Not invited]
  • 走査電気化学顕微鏡による腐食表面の不均一性評価
    瀬尾眞浩, 伏見公志
    材料科学会腐食防食部門委員会資料 37 (3) 40 - 50 1998 [Not refereed][Not invited]
  • 走査電気化学顕微鏡による電極表面反応の解析
    瀬尾眞浩, 伏見公志
    日本金属学会第IV総合分科企画シンポジウム 表面・界面の新しい解析法 17 - 20 1997 [Not refereed][Not invited]
  • Koji Fushimi, Masahiro Seo
    Zairyo to Kankyo/ Corrosion Engineering 46 (12) 797 - 803 0917-0480 1997 [Refereed][Not invited]
     
    A scanning electrochemical microscope (SECM) was used to evaluate heterogeneity of passive films formed on iron in deaerated pH 8. 4 borate solution. The probe current image and specimen current image for the specimen electrode, which consists of two iron plates embedded into epoxy resin, were measured with a tip-generation/substrate-collection (TG/SC) mode in deaerated pH 8.4 borate solution containing [Fe(CN)6]4- as a mediator. The distinctions between epoxy resin and each iron plate were more clear in the probe current image than in the specimen current image. Moreover, the difference in thickness of passive film between two iron plates was distinguishable in the probe current image. The lateral resolution of the probe current image was about 40 μm which was two times as much as the diameter (20 μm) of the probe electrode.
  • 走査電気化学顕微鏡を用いた局部腐食前駆過程の追跡
    伏見公志
    表面科学 17 (11) 703  1996 [Not refereed][Not invited]
  • 半導体電極特性を利用した不働態皮膜の不均一性評価の可能性
    瀬尾眞浩, 伏見公志, W. H. Smyrl
    腐食防食協会：「半導体電極」の腐食防食技術への応用 74 - 85 1996 [Not refereed][Not invited]
  • M SEO, K FUSHIMI, H TAKAHASHI, K AOTSUKA
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 368 (1-2) 257 - 264 0022-0728 1994/04 [Refereed][Not invited]
     
    Electroluminescence (EL) from p-type Si during anodic oxidation under galvanostatic conditions in ethylene glycol solutions of KNO3 with and without different concentrations of chloride ions was measured to investigate the relation between the EL behavior and the defective structure of the silica film formed on Si by anodic oxidation. The measured broad EL spectra had two peaks at 370 nm and 670 nm. The EL peak intensity of the 670 nm peak, rather than that of the 370 nm peak, was enhanced significantly by the addition of chloride ions to the solution, from which it is deduced that the EL source of 670 nm is associated with point defects which are increased by the incorporation of chloride ions in the film. Comparison between the film thickness measured with ellipsometry and the total electric charge required for anodic oxidation revealed that the current efficiency for film growth is only 1% and the majority of the anodic current is electronic, due to electrons injected into the conduction band of the silica film from solution. The relation between EL peak intensities and electrode potential suggested that the EL is operative in an impact ionization-electron avalanche mechanism, where electrons accelerated by a high electric field (2 x 10(7) V cm-1) in the film come into collision with the EL source. The origin of the EL peaks of 670 nm and 370 nm is discussed on the basis of the EL mechanism using an electronic band model of the Si/SiO2/solution system. The breakdown of the silica film due to chloride ions was accompanied by abrupt decreases in the EL peak intensities as well as a rapid potential drop, indicating that EL can be used to monitor breakdown of the film.

MISC

Books etc

  • Electrochemistry for Corrosion Fundamentals
    Toshiaki Ohtsuka, Atsushi Nishikata, Masatoshi Sakairi, Koji Fushimi (Joint work6. Micro-electrochemical Approach for Corrosion Study)
    Springer 2018
  • 機器分析化学
    伏見 公志 (Joint work13 腐食現象への走査型電気化学顕微鏡でのアプローチ)
    朝倉書店 2004

Presentations

  • Luminescence properties of lanthanide coordinantion polymers with 3-D network structures  [Not invited]
    Kohei Miyata, Takayuki Nakanishi, Atsushi Kobayashi, Masako Kato, Koji Fushimi, Yasuchika Hasegawa
    Challenges in Advanced Chemistry of Asia, 2012 HU-NU-SNU-NIMS/MANA Joint Symposium  2012/12  Sapporo, Japan
  • EuS Nano-assembles Attached with Naphthalenedithiols  [Not invited]
    Akira Kawashima, Takayuki Nakanishi, Koji Fushimi, Yasuchika Hasegawa
    Challenges in Advanced Chemistry of Asia, 2012 HU-NU-SNU-NIMS/MANA Joint Symposium  2012/12  Sapporo, Japan
  • Active and Passive State of Iron in Sulfuric Acid Measured by a Micro-capillary-cell  [Not invited]
    Yu Takabatake, Koji Fushimi, Takayuki Nakanishi, Yasuchika Hasegawa
    Challenges in Advanced Chemistry of Asia, 2012 HU-NU-SNU-NIMS/MANA Joint Symposium  2012/12  Sapporo, Japan
  • Formation of area and thickness controlled porous type aluminum anodic oxide films by Sf-MDC  [Not invited]
    M. Sakairi, T. Yamaguchi, T. Murata, K. Fushimi
    PRiME2012  2012/10  Honolulu, USA
  • Stability of Passive State of Iron Single Grains in Sulphuric Acid Measured by a Micro-capillary-cell  [Not invited]
    Y. Takabatake, K. Fushimi, T. Nakanishi, Y. Hasegawa
    63nd Annual Meeting of the International Society of Electrochemistry  2012/08  Prague, Czech Republic
  • Growth and Breakdown of Anodic Oxide Film on Titanium Observed by Ellipsometric Microscopy  [Not invited]
    K. Fushimi, K. Kurauchi, T. Nakanishi, Y. Hasegawa, T. Ohtsuka
    63nd Annual Meeting of the International Society of Electrochemistry  2012/08  Prague, Czech Republic
  • Grain-dependent Passivity of Iron in Sulphuric Acid Using Micro-capillary Cell  [Not invited]
    Y. Takabatake, K. Fushimi, T. Nakanishi, Y. Hasegawa
    9th International Symposium on Electrochemical Micro & Nanosystem Technology  2012/08  Linz, Austria
  • Micro-electrode techniques for corrosion analyses  [Invited]
    K. Fushimi, Y. Takabatake, T. Nakanishi, Y. Hasegawa
    9th International Symposium on Electrochemical Micro & Nanosystem Technology  2012/08  Linz, Austria
  • Magneto-optical properties of Tb(III) clusters  [Not invited]
    Y. Suzuki, Y. Doi, Y. Hinatsu, H. Ito, T. Nakanishi, K. Fushimi, Y. Hasegawa
    19th International SPACC symposium, The society of pure and applied coordination chemistry (SPACC)  2012/08  Sapporo, Japan
  • Luminescent Eu(III) complex with asymmetric coordination structure by monodentate phosphine oxide  [Not invited]
    T. Ohkubo, T. Nakanishi, K. Fushimi, Y. Hasegawa
    19th International SPACC symposium, The society of pure and applied coordination chemistry (SPACC)  2012/08  Sapporo, Japan

Association Memberships

  • 日本鉄鋼協会   表面技術協会   JAPAN SOCIETY OF CORROSION ENGINEERING   電気化学会   The Electrochemical Society   The International Society of Electrochemistry   

Research Projects

  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2022/04 -2026/03 
    Author : 宮本 浩一郎, 伏見 公志, 吉信 達夫
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2022/04 -2025/03 
    Author : 伏見 公志, 坂入 正敏, 宮本 浩一郎
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2021/07 -2023/03 
    Author : 伏見 公志
     
    ４角度偏光子を搭載した偏光カメラを検出器とするPSAR型エリプソメーターを作製した。試料は各種鏡面金属であり、温度湿度制御した光学窓付き試料室内に設置した。単色光源としてレーザーを用いた。ポーララーザー（グランテーラープリズム）にて直線偏光とした単色光を試料表面に照射し、表面膜により楕円化した反射偏光の偏光状態（偏光度Ψおよび位相差Δ）を観察できるように設計した。画像データとして得た偏光状態を行列式（L_out = R(-a)AR(a)SR(-p)PR(p)L_in）に代入し、試料表面の水膜厚さ分布像を高速で、すなわち環境条件変化とほぼ同時に取得することを目的とした。なお、L_inおよびL_outは入射および検出した光のストークスベクトル、R, P, A, Sはそれぞれ回転子、偏光子、検光子および試料のミュラー行列、pとaは偏光子と検光子の回転角度である。カラー偏光カメラにおいてa＝0, 45, 90, 135°が設定されていることから、機械的な回転光学素子を使わないで、反射偏光のΨとΔを試料表面（素地、薄膜、環境）の光学定数と薄膜の厚さの関数として求めることができるようにした。従来型のイメージングエリプソメトリーは単色光源であったために、ΨとΔの関係から膜厚を求める解析の際に不都合があったが、本研究では３波長（445、532、633 nm）の同時使用により、膜厚の解析の精度を大幅に向上させた。
    本年度は上述を実現するためのリアルタイムイメージングエリプソメーターの開発とSiO2薄膜試料を用いた校正を重点的に実施した。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 2018/04 -2021/03 
    Author : HASEGAWA Yasuchika
     
    In this study, preparations and three-dimensional structural control of luminescent lanthanide coordination nanoparticles have been demonstrated for creation of new molecular materials. Mono-nuclear lanthanide complexes were attached using surface-modified linker ligands on the nanoparticles. Eu(III) complexes fixed on the CaS and SiO2 nanoparrticles show bright red-luminescence. Lanthanide coordination polymers were also fixed on the nanoparticles. The three-dimensional structural control of luminescent lanthanide coordination polymers successfully promoted increase of their emission quantum yields.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2015/04 -2017/03 
    Author : Fushimi Koji
     
    Scanning photo-electrochemical apparatus was developed for a new surface treatment. In sulfuric acid, UV-light beam was irradiated on polycrystalline titanium and photo-electrochemical electric charge; photo-electrochemical current integrated by irradiation time was controlled. In-situ ellipso-microscopy and micro Raman spectroscopy revealed that local UV-light irradiation induced dehydration of hydroxide film and then crystallization of amorphous oxide to anatase. Photo-electrochemical polarization with feedback controlling of UV-light irradiation successfully served more homogeneous surface than simple polarization.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2013/04 -2016/03 
    Author : Fushimi Koji, HOMMA Takayuki, SAITO Mikiko, LEE Jun-Seob, TAKABATAKE Yu, YANAGISAWA Kei, JIN Misako, YAMAMOTO Yudai
     
    A 16x16ch Au multielectrode array with a diameter of 10 um and an inter-electrode distance of 100 um was fabricated. Electrochemical measurements using a made-to-order 64 ch multichannel potentiostat revealed that all microelectrodes operated as an individual microelectrode, although their properties varied widely. Polarization of 8x8ch microelectrodes in the array showed an interference of diffusion layer formed on the microelectrodes. The interference was also successfully simulated with a FEM numerical modeling of three-dimensional diffusion problem. The degree of interference during the dynamic polarization of the array could be normalized by the geometry of microelectrode diameter and inter-electrode distance.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2013/04 -2015/03 
    Author : FUSHIMI Koji
     
    In order to identify the initiation site of local corrosion, a visualization method of passive film with an excellent time resolution was developed. A heterogeneous formation of passive film on titanium during potentiodynamic anodic polarization in sulfuric acid, depending on substrate crystallographic orientation, and an initiation process of local breakdown of passive film in the acid containing with bromide ions were successfully observed by using the developed method. Furthermore, an ultra-violet light irradiation during the anodic polarization resulted the thinning of anodic oxide film and heterogeneous degradation of the film. In the initial period, however, the irradiation led to increase in charge transfer resistance through the film and to improve the corrosion resistance.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2011/04 -2015/03 
    Author : HASEGAWA Yasuchika, FUSHIMI Koji
     
    EuS nanocrystals containing paramagnetic Mn(II), Co(II), or Fe(II) ions have been prepared as advanced semiconductor materials with effective optical rotation under a magnetic field, Faraday rotation. Enhanced Faraday rotations of the EuS:M nanocrystals were observed around 550 nm, and their enhanced spin polarization was estimated using electron paramagnetic resonance (EPR) measurements. Thin films composed of EuS nano particle aggregates on a glass electrode exhibited large magneto optical efficiency and a wide energy gap. The Verdet constant of the thin film was approximately 10 times larger than that of previously reported EuS nanoparticles. Remarkable magneto-optical properties of EuS nanocrystals linked with gold (EuS-Au nanosystem) have been demonstrated. The Faraday rotation angle of the EuS-Au nanosystem is dependent on the Au particle size and interparticle distance between EuS and Au nanocrystals. Enhancement of the Faraday rotation of EuS-Au nanosystems was observed.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2011 -2012 
    Author : FUSHIMI Koji
     
    Conventionally, mechanism and kinetics of localized interfacial reaction such as local corrosion have not been so cleared because of a lack of methods to investigate an initiation process of the reaction. A state-of-art micro-electrochemical method, which enables to investigate real-time changes in surface morphology as well as products due to localized electrochemical interfacial reaction, is developed and tentatively apPlied to analyze the initiation of local corrosion in this study. An ellipso- microscope, that is combination of null-type ellipsometer and CCD camera micro- imaging, is applied to titanium surface anodized in sulfulic acid and successfully revealed an anisotropic growth of oxide film depending on the substrate and localized degradation of the film in bromide ion-containing solution. Furthermore, a micro- capillary cell technique with 50 pm diameter sample combined with a long-distance optical microscope was developed and apPlied to potentio-dynamic and - static polarizations and electrochemical impedance spectroscopy of iron in sulfuric acid. It revealed that the passivation of the surface and stability of the passive film were strongly depended on crystallographic orientation of the substrate. Combinations of microelectrochemistry and optical microscopy might take a new turn of the research for the initiation of localized interfacial reaction caused by non-uniformity in the scale of surface microstructures.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2009 -2011 
    Author : FUSHIMI Koji, KONNO Hidetaka, HASEGAWA Yasuchika
     
    New micro-electrochemical techniques developed were applied to investigate the mechanism and kinetics of heterogeneous reaction of the interface between practical materials and environment. Though a probe nano-electrode was successfully developed by using LIGA, the development of a scanning electrochemical nano-scope could not be completed because of the difficulty of probe alignment. However, the application of a coaxial double microelectrode to SECM probe was successfully attained the improvement of sensitivity and lateral resolution of SECM image. Application of this SECM and amicro-electrochemical cell technique to in situ observation of polycrystalline iron surface corroding in acidic sulphate media revealed that iron corroded heterogeneously depending on crystallographic orientation which affected the hydrogen evolution reactivity. The stability of passive state on iron was also strongly dependent on the substrate orientation.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 2007 -2010 
    Author : HABAZAKI Hiroki, FUSHIMI Koji, AOKI Yoshitaka
     
    Plasma electrolytic oxidation (PEO) is an attractive process to form ceramics coatings on light metals, including magnesium, aluminum and titanium, in aqueous electrolytes at ambient temperature. The present study discloses the excellent healing properties of discharge channels in alkaline silicate electrolyte. Further, novel two-step PEO process is developed to form wear-resistant and highly adherent ceramics coating on β-Ti alloy with high mechanical strength and cold workability.
  • 日本学術振興会：科学研究費助成事業 萌芽研究
    Date (from‐to) : 2007 -2008 
    Author : 幅崎 浩樹, 伏見 公志
     
    グロー放電発光分光法(GDOES)がナノ薄膜の迅速分析法として有効であることを示し, 高分解能デプスプロファイルを得るための手法を確立する研究を推進した。まず, 耐海水ステンレス鋼であるSUS312L鋼を用いて, 異なる粒径のアルミナ研磨液を用いて試料を鏡面研磨した。その表面粗さを原子間力顕微鏡(AFM)を用いて計測し, GDOES分析における深さ分解能との相関関係を調べた。研磨条件によりステンレス鋼上に生成する大気酸化皮膜の厚さや組成が変化する可能性があるので, 深さ分解能の評価としてその皮膜直下に存在する銅濃縮層を指標として用いた。GDOESプロファイル上の界面濃縮層の銅のピークの半値幅は表面粗さの対数に対して直線的に変化し, 表面粗さの分解能の影響がきわめて大きいことを明らかにした。同じ鏡面研磨でも表面粗さをできるだけ低減することがナノ薄膜の分析において, 高い深さ分解能を得る上で重要であることを示した。 また, 従来のX線光電子分光法やオージェ電子分光法などの表面分析法では, 感度が低く, 塩化物イオン含有水溶液中で生成した不動態皮膜中の塩化物イオンをGDOESを用いることで検出できた。塩化物イオンは不動態皮膜中の鉄リッチな皮膜外層にのみ存在しており, クロムリッチな皮膜内層には達していないことを示すことができた。 以上のように, ステンレス鋼の不動態皮膜や大気酸化皮膜のような厚さ2-3nm程度の表面酸化皮膜でも, 十分に表面を平滑にした試料を用いることで, 高分解能, 高感度で分析できる手法を確立できた。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2006 -2008 
    Author : KONNO Hidetaka, AZUMI Kazuhisa, USHIMI Kouji
     
    高容量・高効率な電気エネルギー貯蔵用カーボンハイブリッドを,環境負荷がなるべく少ない方法(原料・装置などが低コスト, 廃棄物の利用, プロセスが単純あるいは簡易で特殊な装置を必要としない)で合成することを目的とした。リチウムイオン二次電池およびリチウムハイブリッドキャパシターに利用可能なケイ素/炭素/酸素からなる材料および電気化学キャパシターに利用可能な高い電気容量を持つホウ素/炭素/窒素からなる材料を創製することができた。
  • 低コスト炭素化物被覆処理
    Date (from‐to) : 2008
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2006 -2007 
    Author : AZUMI Kazuhisa, UEDA Mikito, FUSHIMI Koji
     
    Magnesium alloy has superior properties such as very light weight and high strength, and natural resource of magnesium is abound. Despite of these excellent nature, very low corrosion resistance hinders them from wide usage in practical applications. This study has aimed to find out the surface finishing method to provide enough corrosion resistivity to magnesium alloys. We developed chemical conversion technique using sodium stannate bath and potentiostatic anodic polarization method. In this technique anodic polarization of magnesium alloy during immersion in the chemical conversion bath causes dissolution of magnesium surface continuously and uniformly, and thus supplies magnesium ions enough to form dense and uniform conversion film. Form optimization of process condition, AD91D alloy was immersed in the bath with various bath composition, temperature, anodic voltage, and immersion time, and surface observation using optical microscope and scanning electron microscope, and corrosion test were applied for evaluation of the coating film. As a result, following optimized condition was obtained; bath temperature 80℃, anodic potential-1.1 V (Ag/AgCl), NaOH concentration 0.125 mol dm^<-3>. From SEM observation of the conversion film deposited in the optimized condition, the film was composed of small particles in μm scale in closely contact to each other, and the gap between these particles is also filled with smaller particles. Such structure enables low density of structural defects in the film and thus high corrosion resistivity. Forced dissolution process of magnesium alloy also suppresses the non-uniform dissolution of the surface depending on composition such as Mg-rich α phase and Al-rich β phases and thus non-uniform deposition on these different phases. This technique is, therefore, expected to be applicable to the coating treatment of magnesium alloy with various shape.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2004 -2006 
    Author : HABAZAKI Hiroki, FUSHIMI Koji, KONNO Hidetaka
     
    1.Formation of self-organized porous anodic oxide We have successfully developed self-organized porous anodic oxide films on Ti-Si alloys in hot glycerol solution containing dibasic phosphate. The key issue for the formation of the porous films is suppression of the crystallization of anodic oxide, which induces gas evolution during anodic film growth. The similar porous films are also developed on niobium and aluminum substrates. The cell size of the porous films on aluminum is dependent upon the formation voltage, similar to those formed in acid aqueous solutions. 2.Formation of barrier-type anodic oxide with excellent dielectric properties Incorporation of foreign species from substrate suppresses effectively the development of crystalline anodic oxide on titanium. By increasing alloying element content, the structure of the air-formed film present before anodizing is modified, such that growth of amorphous oxide continues to higher formation voltages. The compositional dependence of the dielectric properties of anodic oxides formed on a range of titanium alloys has been examined systematically. 3.Hard coating of titanium alloys by spark anodizing Spark anodizing of titanium, Ti-6Al-4V and Ti-15V-3Al-3Cr-3Sn has been performed in alkarine electrolyte containing aluminate and phosphate. Highly crystalline Al2TiO5-based oxide coatings,〜20μm thick, have been developed by dc-biased ac anodizing to high voltages. Regardless of the materials used, the coatings with hardnes of 〜6GPa have been obtained. The coatings have porosity, associated with discharge channel. From optical measurements during spark anodizing, the temperature at the discharge region has been estimated to be 4500〜5000℃. Such high temperature allows us to develop the highly crystalline coatings with high concentration of electrolyte species even in an aqueous solution at ambient temperature.
  • 日本学術振興会：科学研究費助成事業 若手研究(B)
    Date (from‐to) : 2004 -2005 
    Author : 伏見 公志
     
    前年度の研究実績(プローブを超音波振動させることにより、試料表面に近接した際のプローブ-試料表面間のシアフォースを検知できるようにし、試料表面とプローブの間の距離制御に応用した)によりその機能が向上した走査電気化学顕微鏡(SECM)に、パルス電源および電流検出回路を組み入れた。この改良は、試料電極とプローブ電極間にメガHz帯域の電圧波形を入力し、流れる過渡電流の計測を目的としている。これにより、オンタイムで約30MHzまでの矩形波パルスに伴う電流検出(電流検出時間分解能:10ns、感度10μA)が可能となった。 ヘキサシアノ鉄(II)酸カリウム水溶液中、直径10μmの白金微小ディスク電極とモデル試料(エポキシ樹脂に埋め込んだ白金ディスク電極)間に振幅1〜5V、幅100ns、デューディ比10〜1000の矩形波パルスを印加し、パルスに伴う過渡電流を解析した結果、過渡電流の初期に流れる電流は、プローブと試料それぞれの電極表面上に形成する電気二重層の充電に消費され、その時定数は両電極間の液抵抗と二重層容量の積で表されることを確認した。また、過渡電流後半の電流は、充電完了後のファラディック電流に対応し、プローブ-試料電極間距離に応じて流れることを観察した。すなわち、充電電流とファラディック電流はプローブ直下の試料表面上で最も迅速に流れ始め、プローブ直下以外の周辺部には遅れて流れる。また、両電流はモデル試料表面の電気特性に依存し、導電体(白金)と絶縁体(エポキシ樹脂)の区別を可能とするものである。しかし、これらの電流を実際にSECMの結像信号として用いたときの電流像の面分解能は、従来法(直流の定常ファラディック電流)による面分解能に著しく劣るものであった。この理由は、プローブ-試料電極間の時定数が面分解能に影響するためであり、面分解能の向上にはより短い幅でオーバーシュートのないきれいな形状のパルスを入力すること、出力される電流を高感度に検出することが要求された。本装置の仕様を大きく上回る計測技術の導入により改善される可能性はあるが、本研究の範囲内では実施不可能であった。 なお、以上の研究成果は第56回国際電気化学会(Busan,Sep.2006)にで報告した。
  • マイクロインデンテーション法による不働態表面のメカノエレクトロケミストリ
    Date (from‐to) : 2003
  • Mechano-electrochemistry of passive surface by micro-indentation method
    Date (from‐to) : 2003
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2001 -2002 
    Author : SEO Masahiro, FUSHIMI Koji
     
    Nano-indentation and nao-scratching tests in solution were performed for in-situ evaluation of the mechano-electrochemical properties of passive single crystal iron and polycrystalline titanium surfaces electrochemically controlled in pH 8.4 borate solution. The hardness and friction coefficient of passive metal surfaces in solution could be determined from the load-depth curves measured with nano-indentation tests and from the lateral force curves measured with nano-scratching test, respectively. The hardness of the passive iron (110) surface was larger than that of the passive iron (100) surface, while the friction coefficient of the (110) surface was less than that of the (100) surface. The chromate treatment increased the hardness of both iron (110) and (100) surfaces. The hardness and friction coefficient of the titanium surface obtained with nano-indentation and nano-scratching under the electrochemical control at 5 V were significantly larger than those of the titanium surface obtained with nano-indentation and nano-scratching in air after anodic oxidation at the same condition. The large values of hardness and friction coefficient in solution were attributed to high repassivation rate at the ruptured sites of anodic oxide film under the electrochemical control at 5 V.
  • 局部的電気化学反応の解析と応用
    Date (from‐to) : 2001
  • Analysis and application of localized electrochemical reactions
    Date (from‐to) : 2001
  • 微小電極の新規作製法の開発とその工学的応用
    Date (from‐to) : 2000
  • Fubrication and application of microelectrode technique
    Date (from‐to) : 2000
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 1998 -1999 
    Author : SEO Masahiro, FUSHIMI Koji, AZUMI Kazuhisa
     
    The combinational use of scanning electrochemical microscopy (SECM) and other micro-electrochemical techniques, such as local electrochemical impedance method (LEIM), scanning droplet cell (SDC) and liquid-phase ion gun, was attempted to evaluate the heterogeneity of electrochemical reaction at the metal and solution interface in a scale of several μm to several ten μm. Furthermore, the performance of SECM was improved to obtain the more precise probe current images. The following results were obtained. 1. Micro-disk platinum electrode for SECM was combined with micro-platinum black electrodes for LEIM. A platinum foil embedded into epoxy resin was used as a model specimen electrode. Both SECM and LEIM images could distinguish clearly between the platinum foil and epoxy resin although the lateral resolution of LEIM was several ten times as much as that of SECM. 2. SDC, in which a droplet of electrolyte solution can be scanned over the specimen electrode surface, was combined with SECM. The voltammetry and impedance spectra of a polycrystalline gold electrode measured with SDC have revealed that all grains have a (111) orientation but different azimuth angles. SDC was also applied to form locally anodic oxide films on titanium electrode surface. The local formation of anodic oxide film could be evaluated by SECM. 3. A micro silver electrode covered with silver chloride was employed as a probe electrode of SECM. A small mount of chloride ions could be generated locally with a cathodic polarization of the microelectrode, which was named "liquid-phase ion gun". The use of liquid-phase ion gun succeeded in inducing the local breakdown of passive film on iron electrode. The critical amount of chloride ions needed for initiating the local breakdown depended on the film formation conditions, the electric field in film, and pH of solution. 4. The probe current image of titanium electrode in sulfuric acid solution was measured by detecting oxygen which evolved from the electrode in parallel with film formation during anodic polarization. This probe current image coincided with the probe current image obtained with the conventional SECM measurement in which the redox system of ferrocyanide ions was employed as a mediator. Comparison between the probe current images and optical micrograph has indicated that the heterogeneity of oxygen evolution depends on the crystallographic orientation of the substrate titanium and the oxygen evolution takes place preferentially on the thinner passive film or the film with the higher donor density.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 1998 -1999 
    Author : AZUMI Kazuhisa, FUSHIMI Koji, SEO Masahiro
     
    Titanium is one of the candidates for overpacking material of glass log containing high level radioactive waste produced in power plants. The overpacking material has to protect its contents over 1000 years from environment such as underground water containing chemical composition dissolved from bentonite clay and high temperature up to 100 degree due to heat production of nuclear fission reaction. In this study Ti specimens were immersed in deaerated water in contact with bentonite powder, borate buffer solution, or carbonate solution, and obtained following results. (1) Oxide layer grows on Ti mechanically polished even in deaerated aqueous solution. (2) Electric barrier property degraded during long term immersion. (3) Immersion potential became unstable after long term immersion. (4) Dissolution traces of general corrosion were observed after 20 weeks immersion. (5) Initiation of localized corrosion was observed in aqueous solution in contact with bentonite powder. (6) Corrosion traces and degradation of the film was more obvious at 80 degree than 25 degree. From impedance results, the corrosion rate and degradation of the oxide film were mostly affected by the presence of sulfate ion. From impedance results and AFM observation the anodic oxide film formed on Ti in the solutions containing sulfate ion such as bentonite contact solution has porous structure and electric defects at high density, resulting in more susceptible to the degradation and corrosion. In the present study crevices with a few tenth nm in depth were observed on Ti after 20 weeks immersion. Therefore, it is important to evaluate the possibility that the crevice grows to more serious localized corrosion.
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (A)
    Date (from‐to) : 1997 -1999 
    Author : SEO Masahiro, FUSHIMI Koji, AZUMI Kazuhisa
     
    Nanoindentation tests were performed for the single crystal iron (100) surfaces electrochemically controlled in pH 8.4 borate solution to measure the load-depth curves from which the mechanical properties such as hardness and elastic modulus of the iron surfaces were evaluted to obtain the fundamental knowledge for estabilshment of mechano-electrochemistry. The hardness of the iron surfaces was fluctuated depending on the position of nano-surface area. The average value of hardness, however, took a minimum at 0.25 V in the passive potential region. At the potential above 0.25 v, the average hardness increased linearly with increasing the potential, I.e., the thickness of passive film. The hardness of film itself could be separated from that of the substrate iron by using the linear relation between average hardness and film thickness. Moreover, the nanoindentation tests were performed for the single crystal iron (100) and (110) surfaces passivated at 1.0 V in pH 8.4 borate solution to investigate the depedence of hardness on crystal orientation of the surface. However, no significant differences in hardness was observed between single crystal iron (100) and (110) surfaces. The hardness of the polycrystalline titanium surfaces subjected to anodic oxidation in various electrolyte solutions was measured as a function of formation potential of anodic oxide film. The hardness increased with increasing the film formation potential up to 8 V. The hardness decreased rapidly above 8 V at which the local breakdown of the film would take place. Moreover, the largest hardness was observed for the titanium surfaces subjected to anodic oxidation in sulfuric acid. The stresses generated in the anodic oxide film on titanium were measured by a laser-beam deflection method to investigate the relation between stress in the film and hardness. The largest compressive stresses were generated in anodic oxide film on titanium in sulfuric acid. Therfore, it is found that there is a good correlation between compressive stress and hardness. The partial release of the compressive stresses were observed at the potential above 8 V at which the local breakdown of anodic oxide film took place. The rapid decrease in hardness at the potential above 8 V was ascribed to the partial release of compressive stress ue to local breakdown of anodic oxide film.
  • 日本学術振興会：科学研究費助成事業 奨励研究(A)
    Date (from‐to) : 1997 -1998 
    Author : 伏見 公志
     
    鉄など金属材料の局部腐食は,最も危険な腐食形態である。しかし,局部腐食の反応機構,特に前駆過程には不明な点が多い。本研究は,溶液環境中で金属表面を覆う不働態皮膜に対して,攻撃性アニオンを打ち込むことのできる"液中イオン銃"を開発し,局部腐食前駆過程の解析に適用した。 1. 液中イオン銃には,直径180μmの銀線をガラス管に封入し,先端をディスク状に研磨した後,塩化銀を被覆した微小電極を用いた。液中イオン銃の電極チップからの塩化物イオンの発生は,カソード分極により行った。塩化物イオンの発生効率は,ほぼ100%であり,カソード電気量に比例することを確認した。また,塩化物イオンの発生後には,液中イオン銃の電極チップは,不働態皮膜から溶出する鉄(III)イオン等の検出にも有用であることを確認した。 2. 被測定物である金属試料の電極電位を制御しながら,液中イオン銃を作動させるために,当研究室で開発した走査電気化学顕微鏡を応用した。すなわち,コンピュータにより制御された走査ステージに液中イオン銃を取り付け試料電極との距離を制御し,バイポテンショスタットを用いて試料電極および液中イオン銃の電位の制御と電流の検出を行った。 3. 鏡面研磨した鉄試料表面に,pH6.5のホウ酸塩水溶液中,一定電位E_aでアノード分極することにより不働態皮膜を作成した。引き続き,試料電位をE_aに保持したまま,試料電極表面の上方75μmに配置した液中イオン銃を塩化物イオンを生成する電位-0.1V_に電位規制した結果,数十秒の誘導時間の後,鉄試料に流れるアノード電流が急激に増加し,イオン銃直下の不働態皮膜は局部的に破壊した。一方,アノード電流の増加する間,イオン銃に流れるカソード電流は塩化物イオンの生成電流よりも,異常に増加した。この異常電流は,鉄(III)イオンの還元反応に起因するものであり,皮膜が局部的に破壊される前に塩化物イオンにより,不働態皮膜から鉄(III)イオンが溶出するものと示唆された。皮膜破壊後,試料アノード電流は定常値となり,腐食サイトの窪みは深くなった。一方,イオン銃のカソード電流は,ほとんど零になった。すなわち,皮膜破壊部から鉄(II)イオンが溶出する反応機構で局部腐食が進展することを確認した。これらの局部腐食発生過程は,皮膜作成電位E_aにより異なった。
  • Japan Society for the Promotion of Science：Grants-in-Aid for Scientific Research
    Date (from‐to) : 1996 -1997 
    Author : SEO Masahiro, FUJIMOTO Eiji, FUSHIMI Koji, TAKAHASHI Hideaki
     
    A scanning electrochemical microscope (SECM) was successfully constructed to evaluate the heterogeneity of passive films. A cross section of Pt wire with a diameter of 10mum sealed into glass tube was used as a scanning probe electrode. A commercial type of potentiostat was improved to a bipotentiostat which is capable of controlling independently the potentials of probe and specimen electrodes. The constructed SECM has a lateral resolution of 20mum, wich is two times as much as a diameter of probe electrode. Two iron plates embedded in epoxy resin were anodically polarized at different potentials in pH8.4 borate solution to form passive films with different thickness. Afterward, in pH8.4 borate solution containing Fe (CN) _6^<4->, the probe electrode was polarized at the potentioal at which Fe (CN) _6^<4-> can be oxidized to Fe (CN) _6^<3->, whereas the two iron plates were polarized at the potetial at which Fe (CN) _6^<3-> can be reduced to Fe (CN) _6^<4->. The difference in thickness between passive films on two iron plates could be distinguished from the probe current image. The heterogeneity of passive film formed on polycrystalline iron electrode with distinct grains was also examined in the same manner. The probe current image depended on the grain orientation and the probe current increased in the order of grain orientation, {100}, {111}, and {110}. This difference in probe current results from the difference in thickness of passive films. An electropolished titanium specimen was anodically oxidized in pH 8.4 borate solution to form the passive film. The heterogeneity of the passive film was evaluated using the SECM.It is found from the probe current image that the heterogeneity of the passive film increases with increasing anodic potential for film formation above 4 V_. This heterogeneity corresponds to the shape of each substrate grain, suggesting that the passive film on each substrate grain differs in thickness and defective structure. A scanning photoelectrochemical microscope (SPECM) is being developed by attaching an optical fiber to the probe electrode of SECM.SPECM would be useful to evaluate the difference in defective structures of the passive films.
  • 日本学術振興会：科学研究費助成事業 奨励研究(A)
    Date (from‐to) : 1996 -1996 
    Author : 伏見 公志
     
    1.鉄および炭素鋼などの金属表面の電極特性を微小領域毎に評価する走査プローブ顕微鏡の構築を試みた。プローブは、試料表面近傍に配置した2本の微小電極であり、微小電極間に交流正弦電圧を印加し、同期する電流応答(マイクロインピーダンス)を計測する設計とした。微小電極には、先端径を100μm程度に絞ったガラス管内に0.5mmφの白金線を挿入したものを作製した。プローブ電極は、位置決め分解能0.1μmのXY軸およびZ軸ステージをオートマイクロエンコーダにより走査した。また、試料表面観察用にCRT上で250倍の光学顕微鏡を取り付けた。 2.プローブと試料の電極間距離は、再現性良く制御する必要があった。まず、光学顕微鏡による制御法を検討したが、プローブが破壊するなどして、操作性および再現性に優れなかった。そこで、プローブ電極に別途直径10μmの微小ディスク電極を取り付け、酸化還元体を含む溶液中において定電位分極した際の限界電流を指標とする電極間距離制御法を導入した。微小電極上の拡散層の厚さ以内にプローブが試料に接近すると、限界電流は再現性良く試料の伝導性により変化した(絶縁体試料の場合、減少し、導電体試料場合には増加した)。この方法により、定量的に電極間距離の基準点を定めることが可能となった。 3.原理上、マイクロインピーダンスは2つの微小電極間に存在する溶液の抵抗と容量に依存し、面分解能はプローブをより微小とすることにより向上することが予想された。本研究では、研究室に既存していたポテンショスタット、ファンクションジェネレーターおよびロックインアンプにより、先端径100μmの自作電極を用いて、濃度の異なる水酸化ナトリウム水溶液のマイクロインピーダンスを試験測定したが、重畳印加電圧を数100mVとしても、溶液濃度に依存するマイクロインピーダンスの有意差を測定することができなかった。原因としては、微小電極自身の内部インピーダンスが大きいためにノイズレベルが高いこと、およびポテンショスタットの周波数応答性が悪いことが考えられた。微小電極の改善とともにポテンショスタットの改良あるいは新規導入を検討する必要があることが明らかとなった。
  • 走査型電気化学顕微鏡による界面構造の解析と創製
    Date (from‐to) : 1996
  • Analysis and fabrication of interface structure by scanning electrochemical microscopy
    Date (from‐to) : 1996

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