Researcher Database

Researcher Profile and Settings

Master

Affiliation (Master)

  • Faculty of Engineering Applied Chemistry Inorganic Materials Chemistry

Affiliation (Master)

  • Faculty of Engineering Applied Chemistry Inorganic Materials Chemistry

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Profile and Settings

Degree

  • Doctor of Engineering(1996/10 Osaka Prefecture University)
  • Master of Engineering(1992/03 Kyoto University)

Profile and Settings

  • Name (Japanese)

    Tadanaga
  • Name (Kana)

    Kiyoharu
  • Name

    C-7260-2008, 200901002936741291

Alternate Names

Achievement

Research Interests

  • 機能性無機材料   Inorganic Materials Science   

Research Areas

  • Nanotechnology/Materials / Inorganic materials

Research Experience

  • 2013/04 - Today Hokkaido University
  • 2000 - 2013/03 Osaka Prefecture University
  • 1992 - 2000 Osaka Prefecture University School of Engineering

Education

  •        - 1992  Kyoto University
  •        - 1990  Osaka Prefecture University  School of Engineering

Committee Memberships

  • 2021/10 - Today   International Comission on Glass   Member of Coordinating Technical Committee

Awards

  • 2022/03 The Electrochemical Society of Japan Fellow of the Electrochemical Society of Japan
  • 2020/06 Ceramic Society of Japan CerSJ Fellow Awards
  • 2013 The Ceramic Society of Japan Academic Achievements Award in Ceramic Science and Technology
  • 2006 IUMRS-ICA2006 Best Paper Award
  • 2006 国際ガラス委員会(ICG)Professor Vittorio Gottardi Memorial Prize
  • 2003 日本セラミックス協会 21世紀国際交流賞「倉田元治賞」
  • 2000 日本セラミックス協会進歩賞

Published Papers

  • Margherita Cavallo, Melodj Dosa, Ryosuke Nakazato, Natale Gabriele Porcaro, Matteo Signorile, Matthias Quintelier, Joke Hadermann, Silvia Bordiga, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga, Valentina Crocellà, Francesca Bonino
    Journal of CO2 Utilization 83 102804 - 102804 2212-9820 2024/05 [Refereed][Not invited]
  • Shinji Noguchi, Milena Lama, Yuta Fujii, Akira Miura, Kiyoharu Tadanaga
    Advanced Optical Materials 2400287  2024/04/15 [Refereed]
  • Momoka Demura, Masanori Nagao, Chul-Ho Lee, Yosuke Goto, Yusuke Nambu, Maxim Avdeev, Yuji Masubuchi, Takato Mitsudome, Wenhao Sun, Kiyoharu Tadanaga, Akira Miura
    Inorganic Chemistry 2024/03/18 [Refereed]
  • Kotaro Maki, Koki Muraoka, Saori Kawaguchi, Taku Tanimoto, Akira Nakayama, Seiya Yokokura, Toshihiro Shimada, Kiyoharu Tadanaga, Akira Miura
    CrystEngComm 26 (13) 1814 - 1818 2024 
    Hexagonal Ag3YCl6 was found to transform into a monoclinic structure above ∼1.5 GPa.
  • Sakura Niwa, Yuta Fujii, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga, Riku Maniwa, Misaki Fujimoto, Harumi Takada, Masahiro Morooka
    Energy Advances 3 (3) 609 - 613 2024/01 [Refereed][Not invited]
     
    Composite electrodes were prepared by impregnating both sulphur and solid electrolyte solutions into the interior of the porous carbon and drying them, and the composites were applied to all solid-state lithium-sulphur batteries.
  • Hiroaki Ito, Yuki Nakahira, Naoki Ishimatsu, Yosuke Goto, Aichi Yamashita, Yoshikazu Mizuguchi, Chikako Moriyoshi, Takashi Toyao, Ken-ichi Shimizu, Hiroshi Oike, Masanori Enoki, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Bulletin of the Chemical Society of Japan 96 (11) 1262 - 1268 0009-2673 2023/11/15
  • Ryosuke NAKAZATO, Keeko MATSUMOTO, Noboru YAMAGUCHI, Margherita CAVALLO, Valentina CROCELLÀ, Francesca BONINO, Matthias QUINTELIER, Joke HADERMANN, Nataly Carolina ROSERO-NAVARRO, Akira MIURA, Kiyoharu TADANAGA
    Electrochemistry 91 (9) 097003 - 097003 1344-3542 2023/09/26 [Refereed][Not invited]
  • Shunichiro Shiba, Akira Miura, Yuta Fujii, Kiyoharu Tadanaga, Kota Terai, Futoshi Utsuno, Hiroyuki Higuchi
    RSC Advances 13 (33) 22895 - 22900 2023/07 [Refereed][Not invited]
     
    Crystal structure model of lithium oxy-thiophosphates (LPSO) prepared in the present study (a) and Li10GeP2S12 (b). Purple spheres indicate P, yellow spheres indicate S, red spheres indicate O, and green spheres indicate Ge.
  • Noboru Yamaguchi, Ryosuke Nakazato, Keeko Matsumoto, Masako Kakesu, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    JOURNAL OF ASIAN CERAMIC SOCIETIES 11 (3) 406 - 411 2187-0764 2023/07 [Refereed][Not invited]
     
    Electrocatalytic CO2 reduction reaction (CO2RR) has attracted considerable attention as a technology to recycle carbon dioxide (CO2) into raw materials for chemicals using renewable energies. In this study, the electrocatalytic CO2RR activity of Zn-Al layered double hydroxides (LDHs) was studied. Zn-Al LDHs loaded carbon sheets were prepared, and CO2 RR was performed using CO2-saturated KHCO3 electrolyte to confirm the catalytic ability of Zn-Al LDH. Zn-Al LDHs intercalated with CO32- anion were synthesized using the mixture of metal nitrates with the different molar ratio of Zn2+/Al3+ by the co-precipitation process, whose corresponding products were named as Zn2Al1 LDH, Zn3Al1 LDH, and Zn4Al1 LDH, respectively. Except for Zn2Al1 LDH, ZnO was observed to exist as an impurity. The synthesized Zn-Al LDHs exhibited the electrocatalytic CO2RR activity for CO formation. In the case of the Zn2Al1 LDH, the current density of 15 mA cm(-2) was obtained with 77% selectivity for CO and 94% selectivity for (CO + H-2) at - 1.4 V vs. RHE. Furthermore, Zn3Al1 and Zn4Al1 LDHs showed a significant change relating to ZnO impurities in the XRD patterns and SEM images before and after the CO2RR whereas Zn2Al1 LDH did not show it. These results indicate that Zn-Al LDH is promising as a CO2RR electrocatalyst for CO formation.
  • Hayato Sakai, Shigeto Hirai, Masanori Nagao, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Alloys and Compounds 935 167986 - 167986 0925-8388 2023/02 [Refereed]
  • F.A. Vásquez, N.C. Rosero-Navarro, R. Jalem, A. Miura, Y. Goto, Y. Tateyama, J.A. Calderón, K. Tadanaga
    Applied Materials Today 30 101697 - 101697 2352-9407 2023/02 [Refereed]
  • Tong Fang, Hikaru Tokiwa, Akira Miura, Kiyoharu Tadanaga
    Sustainable Energy & Fuels 7 (17) 4297 - 4302 2023 
    A new type of glassy solid electrolyte was prepared by doping tetramethylammonium iodide (TMAI) in Li7P2S8I. TMAI can suppress the large volume change of a Si electrode during cycling.
  • F.A. Vásquez, N.C. Rosero-Navarro, A. Miura, Y. Goto, K. Tadanaga, J.A. Calderón
    Electrochimica Acta, 437 141544  2023/01 [Refereed]
  • Takuto Toide, Nataly Carolina Rosero-Navarro, Akira Miura, Hiromitsu Kozuka, Kiyoharu Tadanaga
    Journal of Sol-Gel Science and Technology 104 (3) 478 - 483 0928-0707 2022/12 [Refereed]
  • Jennifer Laverde, Nataly C. Rosero-Navarro, Akira Miura, Robison Buitrago-Sierra, Kiyoharu Tadanaga, Diana López
    Batteries 8 (6) 58 - 58 2022/06/17 [Refereed]
     
    Li-S batteries are ideal candidates to replace current lithium-ion batteries as next-generation energy storage systems thanks to their high specific capacity and theoretical energy density. Composite electrodes based on carbon microstructures are often used as a host for sulfur. However, sulfur lixiviation, insoluble species formation, and how to maximize the sulfur-carbon contact in looking for improved electrochemical performance are still major challenges. In this study, a nitrogen doped mesoporous carbon is used as a host for sulfur. The S/C composite electrodes are prepared by sulfur melting-diffusion process at 155 °C. The effect of the sulfur melting-diffusion time [sulfur infiltration time] (1–24 h) and sulfur content (10–70%) is investigated by using XRD, SEM, TEM and TGA analyses and correlated with the electrochemical performance in Li-S cells. S/C composite electrode with homogeneous sulfur distribution can be reached with 6 h of sulfur melting-diffusion and 10 wt.% of sulfur content. Li-S cell with this composite shows a high use of sulfur and sufficient electronic conductivity achieving an initial discharge capacity of 983 mA h g−1 and Coulombic efficiency of 99% after 100 cycles.
  • MIURA Akira, CALPA Marcela, ROSERO-NAVARRO Nataly Carolina, TADANAGA Kiyoharu
    Journal of the Japan Society of Powder and Powder Metallurgy 一般社団法人 粉体粉末冶金協会 69 (3) 95 - 98 0532-8799 2022/03/15 
    Sulfide electrolytes are key materials for all-solid-state batteries. However, the synthesis of sulfide electrolytes needs care to avoid moisture and to prevent the loss of sulfur species. In this minireview, we introduce the chronological history, property, and synthesis of sulfide solid electrolytes, especially that using organic solvents. We show our recent achievements in the synthesis mechanism of β-Li3PS4 via solution process by analyzing intermediates.
  • Nataly Carolina Rosero-Navarro, Hazuki Niwa, Akira Miura, Kiyoharu Tadanaga
    Boletín de la Sociedad Española de Cerámica y Vidrio 0366-3175 2021/12 [Refereed][Not invited]
  • Yuki Ohigashi, Amon Higuchi, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Sol-Gel Science and Technology 101 24 - 28 0928-0707 2021/12/01 [Refereed][Not invited]
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga, Atsunori Matsuda
    Solid State Ionics 372 115789 - 115789 0167-2738 2021/12 [Refereed][Not invited]
  • Sara Giraldo, Koki Nakagawa, Ferley A. Vásquez, Yuta Fujii, Yongming Wang, Akira Miura, Jorge A. Calderón, Nataly C. Rosero-Navarro, Kiyoharu Tadanaga
    Batteries 7 (4) 77 - 77 2021/11/11 [Refereed]
     
    All-solid-state batteries (ASSBs) are a promising response to the need for safety and high energy density of large-scale energy storage systems in challenging applications such as electric vehicles and grid integration. ASSBs based on sulfide solid electrolytes (SEs) have attracted much attention because of their high ionic conductivity and wide electrochemical windows of the sulfide SEs. Here, we study the electrochemical performance of ASSBs using composite electrodes prepared via two processes (simple mixture and solution processes) and varying the ionic conductor additive (80Li2S∙20P2S5 and argyrodite-type Li6PS5Cl). The composite electrodes consist of lithium-silicate-coated LiNi1/3Mn1/3Co1/3O2 (NMC), a sulfide SE, and carbon additives. The charge-transfer resistance at the interface of the solid electrolyte and NMC is the main parameter related to the ASSB’s status. This value decreases when the composite electrodes are prepared via a solution process. The lithium silicate coating and the use of a high-Li-ion additive conductor are also important to reduce the interfacial resistance and achieve high initial capacities (140 mAh g−1).
  • Nataly Carolina Rosero-Navarro, Haruna Watanabe, Akira Miura, Kiyoharu Tadanaga
    Journal of the European Ceramic Society 41 (13) 6767 - 6771 0955-2219 2021/10 [Refereed][Not invited]
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Sol-Gel Science and Technology 0928-0707 2021/09/16 [Refereed][Not invited]
  • Shinji Noguchi, Jin Odahara, Hayato Sakai, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Inorganic Chemistry 60 (17) 12753 - 12758 0020-1669 2021/09/06 [Refereed][Not invited]
  • Hiroaki Ito, Kazuki Shitara, Yongming Wang, Kotaro Fujii, Masatomo Yashima, Yosuke Goto, Chikako Moriyoshi, Nataly Carolina Rosero‐Navarro, Akira Miura, Kiyoharu Tadanaga
    Advanced Science 8 (15) 2101413 - 2101413 2198-3844 2021/08 [Refereed]
  • Daiju Kubo, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    Journal of Electrochemical Science and Technology 12 (2) 230 - 236 2093-8551 2021/05/31 [Refereed][Not invited]
  • Marcela Calpa, Hiroshi Nakajima, Shigeo Mori, Yosuke Goto, Yoshikazu Mizuguchi, Chikako Moriyoshi, Yoshihiro Kuroiwa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Inorganic Chemistry 60 (10) 6964 - 6970 0020-1669 2021/05/17 [Refereed][Not invited]
  • Akira Miura, Christopher J. Bartel, Yosuke Goto, Yoshikazu Mizuguchi, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yongming Wang, Toshie Yaguchi, Manabu Shirai, Masanori Nagao, Nataly Carolina Rosero‐Navarro, Kiyoharu Tadanaga, Gerbrand Ceder, Wenhao Sun
    Advanced Materials 2100312 - 2100312 0935-9648 2021/05/05 [Refereed][Not invited]
  • Hiroki ITO, Akira MIURA, Yosuke GOTO, Yoshikazu MIZUGUCHI, Chikako MORIYOSHI, Yoshihiro KUROIWA, Nataly Carolina ROSERO-NAVARRO, Kiyoharu TADANAGA
    Journal of the Ceramic Society of Japan 129 (5) 249 - 253 1882-0743 2021/05/01 [Refereed][Not invited]
  • Yuta Fujii, Hiroaki Ito, Akira Miura, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga, Li Lu
    Functional Materials Letters 14 (03) 2141005 - 2141005 1793-6047 2021/04 [Refereed][Not invited]
     
    We report the fast discharge–charge cycle of micro-sized FePS3 electrode particles in all-solid-state batteries (ASSBs) using sulfide electrolytes at 80C. At a current density of 2.04 mA cm[Formula: see text], corresponding to approximately 1 C, the capacity of the FePS3 electrodes reached [Formula: see text]180 mAh g[Formula: see text] without any electron or lithium-ion conductive additives. Galvanostatic intermittent titration technique (GITT) measurements showed a stable diffusion path of FePS3 represented by the product of the diffusion coefficient and square of the surface area. These electrochemical properties were compared with those of FeS, whose capacity was lower because of its unstable diffusion path.
  • F. A. Vásquez, N. C. Rosero-Navarro, A. Miura, R. Jalem, Y. Goto, M. Nagao, Y. Tateyama, K. Tadanaga, J. A. Calderón
    ACS Applied Materials & Interfaces 13 (12) 14056 - 14067 1944-8244 2021/03/31 [Refereed][Not invited]
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Randy Jalem, Yoshitaka Tateyama, Kiyoharu Tadanaga
    Applied Materials Today 22 100918 - 100918 2352-9407 2021/03 [Refereed][Not invited]
  • Kiyoharu Tadanaga, Nataly Carolina Rosero-Navarro, Akira Miura
    Next Generation Batteries 85 - 92 2021
  • Riku Maniwa, Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Materials Chemistry A 9 (1) 400 - 405 2050-7488 2021 [Refereed][Not invited]
     

    We report the liquid-phase synthesis of sulfide solid electrolytes from Li2S and P2S5 using anisole at 200–300 °C under microwave irradiation, in which β-Li3PS4 and Li7P3S11 were directly precipitated in anisole in 30 min.

  • Nataly Carolina Rosero-Navarro, Ryunosuke Kajiura, Akira Miura, Kiyoharu Tadanaga
    ACS Applied Energy Materials 3 (11) 11260 - 11268 2574-0962 2020/11/23 [Refereed]
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kota Terai, Futoshi Utsuno, Kiyoharu Tadanaga
    Chemistry of Materials 32 (22) 9627 - 9632 0897-4756 2020/11/05 [Refereed][Not invited]
  • Akira MIURA, Sho ISHIYAMA, Daiju KUBO, Nataly Carolina ROSERO-NAVARRO, Kiyoharu TADANAGA
    Journal of the Ceramic Society of Japan 128 (7) 336 - 339 1882-0743 2020/07/01 [Refereed][Not invited]
  • Nataly Carolina Rosero-Navarro, Ryunosuke Kajiura, Randy Jalem, Yoshitaka Tateyama, Akira Miura, Kiyoharu Tadanaga
    ACS Applied Energy Materials 3 (6) 5533 - 5541 2574-0962 2020/05/27 [Refereed][Not invited]
  • Daiju Kubo, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    Frontiers in Materials 7 117  2020/04/30 [Refereed][Not invited]
     
    © Copyright © 2020 Kubo, Tadanaga, Hayashi and Tatsumisago. Layered double hydroxides (LDHs) are promising solid electrolytes for all solid-state alkaline fuel cells (AFCs) because of inorganic clay-like materials. However, LDHs were usually obtained as powder, and the formation of thin membranes as a separator of a fuel cell is rather difficult. In this study, a glass paper, non-woven fabric of fine glass fibers with more than 90% porosity, was used as a support for Mg-Al LDH powder, and self-standing, thin membranes for all solid-state AFCs were fabricated. Crystals of Mg-Al LDH were deposited in the inside of the glass paper by repeated immersion in Mg-Al LDH-dispersed solution and drying. Thickness of the obtained Mg-Al LDH thin membrane was about 150 μm, and LDH layer showed c-axis orientation because of the plate-like structure. The H2-O2 fuel cell using the Mg-Al LDH thin membrane as an electrolyte showed open circuit voltage of more than 0.9 V, indicating that the Mg-Al LDH thin membrane is dense and has high gas barrier property. The H2-O2 fuel cell using the Mg-Al LDH thin membrane showed higher power density compared with that using pelletized Mg-Al LDH powder as the electrolyte. The glass paper is proved to be very effective support for making thin Mg-Al LDH electrolyte membrane.
  • Fujii, Yuta, Akira, Miura, Misaki, Kobayashi, Rosero-Navarro, Nataly Carolina, Li, Minchan, Sun, Jianguo, Kotobuki, Masatoshi, Lu, Li, Tadanaga, Kiyoharu
    Journal of Power Sources 449 (15) 227576 - 227576 2020/02 [Refereed][Not invited]
  • Akira Miura, Hiroaki Ito, Christopher J. Bartel, Wenhao Sun, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga, Hiroko Nakata, Kazuhiko Maeda, Gerbrand Ceder
    Materials Horizons 7 (5) 1310 - 1316 2051-6347 2020 [Refereed][Not invited]
     

    By altering the thermodynamic landscape, metathesis enables the rapid and selective synthesis of MgCr2S4 thiospinel, a compelling Mg-cathode material that is laborious to make via traditional ceramic synthesis routes.

  • Nagao, Masanori, Miura, Akira, Urushihara, Daisuke, Maruyama, Yuki, Goto, Yosuke, Mizuguchi, Yoshikazu, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Wang, Yongming, Watauchi, Satoshi, Asaka, Toru, Takano, Yoshihiro, Tadanaga, Kiyoharu, Tanaka, Isao
    Frontiers in Chemistry - 2020 [Refereed][Not invited]
  • W. I, U. WITHANAGE, Nobuhiro Kumada, Takahiro Takei, Sayaka YANAGIDA, Kiyoharu Tadanaga, Akira Miura, Nataly Carolina Rosero-Navarro, Masaki Azuma
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 128 (1) 46 - 50 1882-0743 2020/01/01 [Refereed][Not invited]
  • Ishiyama Sho, Rosero-Navarro Nataly Carolina, Miura Akira, Tadanaga Kiyoharu
    MATERIALS RESEARCH BULLETIN 119 0025-5408 2019/11 [Refereed][Not invited]
  • Kubo Daiju, Igarashi Kohei, Ishiyama Sho, Rosero Navarro, Nataly Carolina, Miura Akira, Higuchi Mikio, Tadanaga Kiyoharu
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 127 (11) 788 - 792 1882-0743 2019/11 [Refereed][Not invited]
  • Yuta Fujii, Daniel Ramirez, Nataly Carolina Rosero-Navarro, Domingo Jullian, Akira Miura, Franklin Jaramillo, Kiyoharu Tadanaga
    ACS Applied Energy Materials American Chemical Society ({ACS}) 2019/08 [Refereed][Not invited]
  • Nagao, Masanori, Miura, Akira, Matsumoto, Ryo, Maruyama, Yuki, Watauchi, Satoshi, Takano, Yoshihiko, Tadanaga, Kiyoharu, Tanaka, Isao
    Solid State Communications 296 17 - 20 2019/07 [Refereed][Not invited]
  • Iwai, Yu, Ikka, Takuya, Miura, Akira, Rosero-Navarro, N. C, Iwamura, Shinichiroh, Ogino, Isao, Mukai, Shin R, Tadanaga, Kiyoharu
    CHEMISTRY LETTERS 48 (7) 696 - 699 0366-7022 2019/07 [Refereed][Not invited]
  • Jin Odahara, Wenhao Sun, Akira Miura, Nataly Carolina Rosero-Navarro, Masanori Nagao, Isao Tanaka, Gerbrand Ceder, Kiyoharu Tadanaga
    ACS Materials Letters American Chemical Society ({ACS}) 64  2019/07 [Refereed][Not invited]
  • Ito, Hiroaki, Miura, Akira, Goto, Yosuke, Mizuguchi, Yoshikazu, Moriyoshi,Chikako, Kuroiwa, Yoshihiro, Azuma, Masaki, Liu, Jinjia, Wen, Xiao-Dong, Nishioka,Shunta, Maeda, Kazuhiko, Masubuchi, Yuji, Rosero-Navarro, Nataly Carolina, Tadanaga, Kiyoharu
    Dalton Transactions 48 (32) 12272 - 12278 1477-9226 2019/06 [Refereed][Not invited]
     
    An extremely large displacement of the indium site in In-S-6 octahedra in LnOInS(2) (Ln = La, Ce, and Pr) was found in synchrotron X-ray diffraction. LaOInS2 with off-center indium in In-S-6 octahedra exhibited a wider optical band gap than CeOInS2 and PrOInS2 with on-center indium. Therefore, the electronic structure of LnOInS(2) is governed by the indium site with an extremely large displacement. All LnOInS(2) produced H-2 gas under visible light irradiation in the presence of sacrificial electron donors.
  • Sogabe,Ryota, Goto, Yosuke, Abe, Tomohiro, Moriyoshi, Chikako, Kuroiwa, Yoshihiro, Miura, Akira, Tadanaga, Kiyoharu, Mizuguchi, Yoshikazu
    Solid State Communications 295 43 - 49 2019/06 [Refereed][Not invited]
  • Lyn Marie, Z. De Juan-Corpuz, Mai Thanh Nguyen, Ryan D. Corpuz, Tetsu Yonezawa, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga, Tomoharu Tokunaga, Soorathep Kheawhom
    ACS Applied Nano Materials American Chemical Society ({ACS}) 2019/06 [Refereed][Not invited]
  • Yu Iwai, Akira Miura, Nataly Carolina Rosero-Navarro, Mikio Higuchi, Kiyoharu Tadanaga
    Journal of Asian Ceramic Societies Informa {UK} Limited 1  2019/04 [Refereed][Not invited]
  • Akira Miura, Nataly Carolina Rosero-Navarro, Atsushi Sakuda, Kiyoharu Tadanaga, Nguyen H. H. Phuc, Atsunori Matsuda, Nobuya Machida, Akitoshi Hayashi, Masahiro Tatsumisago
    Nature Reviews Chemistry Springer Nature 3 (3) 189 - 198 2019/03 [Refereed][Not invited]
     
    Solid sulfide electrolytes are key materials in all-solid-state lithium batteries because of their high lithium-ion conductivity and deformability, which enable the lithium-ion path to be connected between the material’s grain boundaries under pressure near room temperature. However, sulfur species are moisture-sensitive and exhibit high vapour pressures; therefore, syntheses of sulfide electrolytes need to be carefully designed. Liquid-phase reactions can be performed at low temperatures in controlled atmospheres, opening up the prospect of scalable processes for the preparation of sulfide electrolytes. Here, we review liquid-phase syntheses for the preparation of sulfide-based solid electrolytes and composites of electrolytes and electrodes, and we compare the charge–discharge performances of the all-solid-state lithium batteries using these components.
  • Calpa, Marcela, Rosero-Navarro, Nataly Carolina, Miura, Akira, Tadanaga, Kiyoharu
    ELECTROCHIMICA ACTA 296 473- - 480 2019/02 [Refereed][Not invited]
  • Ionic conductivity of Pyrochlore-type Silver Tantalate and Fluorite-type Silver Niobate
    W. I, U. WITHANAGE, Nobuhiro Kumada, Takahiro Takei, Sayaka YANAGIDA, Kiyoharu Tadanaga, Akira Miura, Nataly Carolina, Rosero-Navarro, Masaki Azuma
    J. Ceram. Soc. Jpn. in press 2019 [Refereed][Not invited]
  • Rosero-Navarro, Nataly Carolina, Miura, Akira, Tadanaga, Kiyoharu
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 89 (1) 303 - 309 2019/01 [Refereed][Not invited]
  • George V Alexander, Nataly Carolina, Rosero Navarro, Akira Miura, Kiyoharu Tadanaga, Ramaswamy Murugan
    Journal of Materials Chemistry A Royal Society of Chemistry ({RSC}) 6 21018 - 21028 2018/10 [Refereed][Not invited]
  • Fujii Y, Miura A, Rosero-Navarro N.C, Mizuguchi Y, Moriyoshi C, Kuroiwa Y, Higuchi M, Tadanaga K
    Journal of The Electrochemical Society 165 A2948  2018/09 [Refereed][Not invited]
  • Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Journal of Power Sources 396 33 - 40 0378-7753 2018/08/31 [Refereed][Not invited]
     
    All-solid-state lithium batteries based on sulfide solid electrolytes are potential candidates for large-scale energy storage applications. Here, composite cathode with high content of an active material was prepared by a liquid phase process assisted by a dispersant agent to produce a better electrode and electrolyte interface. Li6PS5Cl sulfide electrolyte derived from a solution containing dispersant showed an argyrodite crystal phase with a better distribution of particle size and higher conductivity compared with those without dispersant. Regular distribution of Li6PS5Cl particles in nanometric scale with a spherical shape below 500 nm and conductivity of 0.6 × 10−3 S cm−1 (ρ = 1.40 g cm−3) at room temperature were obtained. Composite cathode was prepared by the dispersion of LiNi1/3Mn1/3Co1/3O2 particles and carbon additive in the Li6PS5Cl-solution containing dispersant agent and subsequent drying at 180 °C. Bulk-type all-solid-state battery fabricated with the composite cathode containing 89 wt% of the active material showed an initial discharge capacity of 110 mA h g−1 at 25 °C and maintained 95% discharge capacity after 15 cycles.
  • Synthesis of Bi2(O,F)S2 superconductors by NaF treatment
    Takahashi N, Nagao M, Miura A, Watauchi S, Tadanaga K, Takano Y, Tanaka I
    J. Ceram. Soc. Jpn. 126 (7) 591 - 593 2018/07 [Refereed][Not invited]
  • Suto Y, Fujii Y, Miura A, Rosero-Navarro N.C, Higuchi M, Tadanaga K
    J. Ceram. Soc. Jpn. 126 (7) 568 - 572 2018/07 [Refereed][Not invited]
  • Synthesis, crystal structure and optical absorption of NaInS2-xSex
    Takahashi N, Ito H, Miura A, Rosero-Navarro N.C, Goto Y, Mizuguchi Y, Moriyoshi C, Kuroiwa Y, Nagao M, Watauchi S, Tanaka I, Tadanaga K
    J. Alloy. Compounds 750 409 - 423 2018/06 [Refereed][Not invited]
  • Moe Narita, Mikio Higuchi, Takayo Ogawa, Satoshi Wada, Akira Miura, Kiyoharu Tadanaga
    Optical Materials 80 57 - 61 0925-3467 2018/06/01 [Refereed][Not invited]
     
    Yb:CaYAlO4 single crystals were grown by the floating zone method and their spectral properties were investigated. Void formation was effectively suppressed by using a feed rod of Y-rich composition with the aid of a double zone-pass technique. For the oxygen excess composition of Yb:Ca0.9925Y1.0075AlO4.00375, a void-free crystal was obtained by performing only the double zone-pass. On the other hand, for cation-deficient type of Yb:Ca0.9925Y1.005AlO4, void-free crystal could not be obtained by performing the double zone-pass. The void formation is attributable to the constitutional supercooling caused by segregation of main constituents of Y and Ca, and the congruent composition may exist in the Y-rich region with existence of interstitial excess oxide ions. The absorption cross section for σ-polarization was slightly larger than that for π-polarization, which is reasonable on the basis of the crystal structure of CaYAlO4.
  • Akira Miura, Masanori Nagao, Yosuke Goto, Yoshikazu Mizuguchi, Tatsuma D. Matsuda, Yuji Aoki, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yoshihiko Takano, Satoshi Watauchi, Isao Tanaka, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga
    Inorganic Chemistry 57 (9) 5364 - 5370 1520-510X 2018/05/07 [Refereed][Not invited]
     
    Ce1-xPrxOBiS2 powders and Ce0.5Pr0.5OBiS2 single crystals were synthesized and their structure and superconductive properties were examined by X-ray diffraction, X-ray absorption, electronic resistivity, and magnetization. While PrOBiS2 was found to be in a monoclinic phase with one-dimensional Bi-S zigzag chains showing no superconductive transition above 0.1 K, CeOBiS2 was in a tetragonal phase with two-dimensional Bi-S planes showing zero resistivity below 1.3 K. In the range x = 0.3-0.9 in Ce1-xPrxOBiS2, both monoclinic and tetragonal phases were formed together with zero resistivity up to a maximum temperature of 2.2 K. A Ce0.5Pr0.5OBiS2 single crystal, which showed both zero resistivity and a decrease in magnetization at ∼2.4 K, presented a tetragonal structure. Short Bi-S bonding in flat two-dimensional Bi-S planes and mixed Ce3+/Ce4+ were characteristic features of the Ce0.5Pr0.5OBiS2 single crystal, which presumably triggered its superconductivity.
  • Daniel Ramirez, Yusaku Suto, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga, Franklin Jaramillo
    Inorganic Chemistry 57 (7) 4181 - 4188 1520-510X 2018/04/02 [Refereed][Not invited]
     
    Organic-inorganic hybrid perovskite materials have recently been investigated in a variety of applications, including solar cells, light emitting devices (LEDs), and lasers because of their impressive semiconductor properties. Nevertheless, the perovskite structure has the ability to host extrinsic elements, making its application in the battery field possible. During the present study, we fabricated and investigated the electrochemical properties of three-dimensional (3D) methylammonium lead mixed-halide CH3NH3PbI3-xBrx and two-dimensional (2D) propylammonium-methlylammonium lead bromide (CH3NH3)2(CH3(CH2)2NH3)2Pb3Br10 hybrid perovskite thin films as electrode materials for Li-ion batteries. These electrodes were obtained by solution processing at 100 °C. CH3NH3PbBr3 achieved high discharge/charge capacities of ∼500 mA h g-1 /160 mA h g-1 that could account also for other processes taking place during the Li intercalation. It was also found that bromine plays an important role for lithium intercalation, while the new 2D (CH3NH3)2(CH3(CH2)2NH3)2Pb3Br10 with a layered structure allowed reversibility of the lithium insertion-extraction of 100% with capacities of ∼375 mA h g-1 in the form of a thin film. Results suggest that tuning the composition of these materials can be used to improve intercalation capacities, while modification from 3D to 2D layered structures contributes to improving lithium extraction. The mechanism of the lithium insertion-extraction may consist of an intercalation mechanism in the hybrid material accompanying the alloying-dealloying process of the LixPb intermetallic compounds. This work contributes to revealing the relevance of both composition and structure of potential hybrid perovskite materials as future thin film electrode materials with high capacity and compositional versatility.
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    Inorganic Chemistry Frontiers Royal Society of Chemistry ({RSC}) 5 (2) 501 - 508 2052-1553 2018/02/01 [Refereed][Not invited]
     
    Sulfide solid electrolytes in the Li2S-P2S5 system were synthesized by a liquid phase process under ultrasonic irradiation, and heat treatments at low temperatures. Crystal phase, structure, morphology and ionic conductivity of the sulfide electrolytes were examined after solvent removal at 180 °C and two different heat treatment temperatures, 220 °C and 250 °C. The study revealed that the ionic conductivities of the xLi2S·(100 - x)P2S5 sulfide electrolytes, in compositions with 70 ≤ x ≤ 75 mol%, are largely influenced by the local structure. The heat treatment at 220 °C was found to be an adequate temperature to promote crystallization of the high ionic conductive Li7P3S11 phase. Higher temperatures for heat treatment such as 250 °C lead to the formation of P2S6 4- (hypo-thiodiphosphate) units in the local structure of the sulfide electrolytes leading to a reduction of ionic conductivity. The formation and distribution of PS4 3- (ortho-thiophosphate), P2S7 4- (pyro-thiophosphate) and P2S6 4- units in the local structure were found to be key factors in achieving higher ionic conductivity (up to 10-3-10-4 S cm-1 at room temperature).
  • Jin Odahara, Akira Miura, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga
    Inorganic Chemistry 57 (1) 24 - 27 1520-510X 2018/01/02 [Refereed][Not invited]
     
    An intense exothermic and explosive reaction between Ba(OH)2, NbCl5, and NaNH2 produced barium niobium perovskite oxynitride in seconds. The addition of hexane reduced the risk of explosion during mixing of the starting materials, and subsequent heat treatment at 498 K in hexane allowed control of this exothermic reaction, leading to formation of the perovskite oxynitride with fewer impurities. The synthesis of barium tantalum perovskite oxynitride under similar reaction conditions was successful.
  • Shunjiro Chida, Akira Miura, Nataly Carolina Rosero-Navarro, Mikio Higuchi, Nguyen H. H. Phuc, Hiroyuki Muto, Atsunori Matsuda, Kiyoharu Tadanaga
    CERAMICS INTERNATIONAL 44 (1) 742 - 746 0272-8842 2018/01 [Refereed][Not invited]
     
    Lithium-ion conductive Li6PS5Br is prepared using ultrasonication of Li2S, P2S5 and LiBr in ethyl propionate-ethanol solution and subsequent heating at 453 K. The main phase of the synthesized product is Li6PS5Br and its lithium ion conductivity is 3.4 x 10(-5) S cm(-1) at room temperature. The cathode composite of LiCo1/3Ni1/3Mn1/3O2, Li6PS5Br and vapor grown carbon fiber (VGCF) is prepared via ultrasonication of the Li6PS5Br precursor solution containing LiCo1/3Ni1/3Mn1/3O2 and VGCF, and the all-solid-state lithium battery using this cathode composite is fabricated. The cell exhibits the discharge capacity of 109 mAh g(-1) for the first cycle and its capacity of 87 mAh g(-1) after 10 cycles.
  • Yoshikazu Mizuguchi, Kazuhisa Hoshi, Yosuke Goto, Akira Miura, Kiyoharu Tadanaga, Chikako Moriyoshi, Yoshihiro Kuroiwa
    Journal of the Physical Society of Japan 87 (2) 023704  1347-4073 2018 [Refereed][Not invited]
     
    In order to understand the mechanisms behind the emergence of superconductivity by the chemical pressure effect in REO0.5F0.5BiS2 (RE = La, Ce, Pr, and Nd), where bulk superconductivity is induced by the substitutions with a smaller-radius RE, we performed synchrotron powder X-ray diffraction, and analyzed the crystal structure and anisotropic displacement parameters. With the decrease of the RE3+ ionic radius, the in-plane disorder of the S1 sites significantly decreased, very similar to the trend observed in the Se-substituted systems: LaO0.5F0.5BiS2−xSex and Eu0.5La0.5FBiS2−xSex. Therefore, the emergence of bulk superconductivity upon the suppression of the in-plane disorder at the chalcogen sites is a universal scenario for the BiCh2-based superconductors. In addition, we indicated that the amplitude of vibration along the c-axis of the in-plane chalcogen sites may be related to the Tc in the BiCh2-based superconductors.
  • Yudai Hijikata, Tomohiro Abe, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yosuke Goto, Akira Miura, Kiyoharu Tadanaga, Yongming Wang, Osuke Miura, Yoshikazu Mizuguchi
    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN 86 (12) 124802  0031-9015 2017/12 [Refereed][Not invited]
     
    We have synthesized a new layered oxychalcogenide La2O2Bi3AgS6. From synchrotron X-ray diffraction and Rietveld refinement, the crystal structure of La2O2Bi3AgS6 was refined using a model of the P4/nmm space group with a = 4.0644(1) angstrom' and c = 19.412(1) angstrom, which is similar to the related compound LaOBiPbS3, while the interlayer bonds (M2-S1 bonds) are apparently shorter in La2O2Bi3AgS6. The tunneling electron microscopy (TEM) image confirmed the lattice constant derived from Rietveld refinement (c similar to 20 angstrom). The electrical resistivity and Seebeck coefficient suggested that the electronic states of La2O2Bi3AgS6 are more metallic than those of LaOBiS2 and LaOBiPbS3. The insertion of a rock-salt-type chalcogenide into the van der Waals gap of BiS2-based layered compounds, such as LaOBiS2, will be a useful strategy for designing new layered functional materials in the layered chalcogenide family.
  • Anongsack Paseuth, Yasuki Kido, Shinya Imamura, Kazuo Yamagata, Akira Miura, Kiyoharu Tadanaga
    Journal of the Ceramic Society of Japan 125 (12) 913 - 918 1348-6535 2017/12/01 [Refereed][Not invited]
     
    Al-rich cubic (c-) AlxTi1-xN (x μ 0.8) coating comprising self-organised c-Al(Ti)N/c-Ti(Al)N nanolamellae was prepared in a previous study by low-pressure chemical vapour deposition (LP-CVD) using an AlCl3-TiCl4-NH3-Ar-H2 precursor system. In the present study, we investigated the effects of isothermal annealing at 800 to 1200°C for 1 to 10 h on the crystal structure, microstructure, and hardness of the coating, and compared them to those of a monolithic c-AlxTi1-xN (x μ 0.6) coatings prepared by arc-evaporated physical vapour deposition (PVD). The X-ray diffraction patterns indicated high phase stability of the former coating up to 1200°C after 1 h. High-resolution transmission electron microscopy revealed that the nanolamellae in c-AlxTi1-xN (x μ 0.8) coating remained stable after post-annealing at 900°C for 5 h. The spontaneously formed coherent nanostructure suppressed diffusion in this coating, and the spinodal decomposition and hexagonal phase formation were thus shifted to higher temperatures. Consequently, age hardening in LP-CVD c-AlxTi1-xN (x μ 0.8) helped to maintain its hardness at up to 1100°C after 10 h. The improved thermal stability and hardness at elevated temperature of the Al-rich c-AlxTi1-xN coating by LP-CVD led to a significant improvement in the cutting tool life, by factors of 2 and 10 compared to state-of-the-art CVD-and PVD-coated inserts, respectively. These improvements in thermal stability and elevated hardness in c-AlxTi1-xN (x μ 0.8) coating prepared via LP-CVD process could remarkably enhance tool life for dry and high-speed cutting applications.
  • Akira Miura, Tsukasa Hokimoto, Masanori Nagao, Takashi Yanase, Toshihiro Shimada, Kiyoharu Tadanaga
    ACS omega 2 (8) 5271 - 5282 2017/08/31 [Refereed][Not invited]
     
    The relationship of liquidus temperatures among six binary and four ternary phases in a Ag-Al-Sn-Zn system was analyzed by means of statistical modeling. Four statistical models to predict changes in the liquidus temperatures in Ag-Al-Sn-Zn were proposed on the basis of different hypotheses derived from macroscopic and microscopic standpoints. The results of interpolation tests to evaluate the prediction accuracies of the ternary liquidus temperatures suggested that the multivariate regression model based on binary liquidus temperatures, interactive binary liquidus temperatures, and products of atomic ratios was found to be the most effective among the four models. It was numerically shown that the prediction accuracies of the liquidus temperatures in local ternary systems of Ag-Al-Sn-Zn can be improved further by using the models identified in their neighboring systems. Finally, the possibility to extract the general trend and the abnormal combination of elements for the prediction of liquidus temperatures was discussed on the basis of the statistical framework we considered.
  • Saki Toyoda, Mikio Higuchi, Youichi Tsubota, Junichi H. Kaneko, Kiyoharu Tadanaga
    OPTICAL MATERIALS 70 180 - 183 0925-3467 2017/08 [Refereed][Not invited]
     
    Translucent LiCaBO3:Ce thin plates were prepared by liquid phase sintering using LiBO2 as a sintering aid, and their fluorescent and scintillation properties were investigated to examine the possibility to use as neutron scintillator. Since the initial part of the directionally solidified specimen contained a second phase of Ca3B2O6, LiCaBO3 may melt incongruently, and simple melt growth of LiCaBO3:Ce is consequently difficult. Translucent thin plates 300 mu m in thickness were successfully fabricated from LiCaBO3:Ce sintered compacts. Although strong fluorescence with the peak wavelength of 390 nm was observed in photoluminescence measurement, scintillation light yield and detection efficiency by alpha-particle irradiation were rather poor. The diffuse reflectance spectrum of LiCaBO3:Ce revealed existence of an absorption band other than Ce3+ bands in the ultraviolet region. The band may corresponds to defect levels, which interrupt the energy transfer from the conduction band of the host to the 5d level of Ce3+ resulting in the degradation of the scintillation performance. (C) 2017 Elsevier B.V. All rights reserved.
  • Akira Miura, Takayoshi Oshima, Kazuhiko Maeda, Yoshikazu Mizuguchi, Chikako Moriyoshi, Yoshihiro Kuroiwa, Yu Meng, Xiao-Dong Wen, Masanori Nagao, Mikio Higuchia, Kiyoharu Tadanaga
    JOURNAL OF MATERIALS CHEMISTRY A 5 (27) 14270 - 14277 2050-7488 2017/07 [Refereed][Not invited]
     
    Indium oxychalcogenides would be attractive semiconductors considering the practical use of indium oxides and sulfides such as indium-tin oxides (ITO) and copper-indium-gallium diselenides (CIGS). In this work, a novel layered indium oxysulfide, LaOInS2, was synthesized by a metathesis reaction between LaOCl and NaInS2. Synchrotron X-ray diffraction showed that LaOInS2 consisted of alternately stacked rocksalt-type In-S and PbO-type La-O layers. The InS6 octahedron had split In sites with abnormally large anisotropic atomic displacement factors. LaOInS2 was found to be a direct semiconductor. Density functional theory calculations exhibited well-dispersed bands composed of In 5s/5p and S 3p/O 2p orbitals with a band gap of similar to 2.4 eV, which was close to the experimental value estimated by optical absorption (2.64 eV). Under visible light irradiation this visible-light absorption, LaOInS2 exhibited photocatalytic activity for H-2 and O-2 evolution from water with the aid of Pt and IrO2 cocatalysts, respectively.
  • Yuta Fujii, Akira Miura, Nataly Carolina Rosero-Navarro, Mikio Higuchi, Kiyoharu Tadanaga
    ELECTROCHIMICA ACTA 241 370 - 374 0013-4686 2017/07 [Refereed][Not invited]
     
    In bulk-type all-solid-state lithium batteries with sulfide-based solid electrolytes, composite electrodes, in which an active material, a solid electrolyte, and a conductive additive are mixed, have been used to enhance lithium-ion diffusion and electronic conductivity. However, the addition of electrolytes and electron-conductive additives to the composite electrodes decreases the amount of active materials in the batteries. In the present study, FePS3 was employed as the electrode in an all-solid-state lithium secondary battery, without mixing the solid electrolytes and conductive additives. The all-solid-state cell using the FePS3 electrode exhibited reversible charge-discharge behavior for more than 30 cycles under a constant current density of 0.13 mA cm (2) at room temperature. The discharge capacity of the cell was 107 mAh g (1) at the 30th cycle. This behavior was comparable to that of a cell with an electrode including a solid electrolyte and/or a conductive additive, indicating that the FePS3 electrode had sufficient paths of lithium ions and of electron conduction. These results suggest that FePS3 is an attractive iron-based electrode for an all-solid-state battery using a sulfide-based solid electrolyte. (C) 2017 Elsevier Ltd. All rights reserved.
  • Akira Miura, Satoshi Ishii, Masanori Nagao, Ryo Matsumoto, Yoshihiko Takano, Satoshi Watauchi, Isao Tanaka, Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga
    Journal of Asian Ceramic Societies 5 (2) 183 - 185 2187-0764 2017/06/01 [Refereed][Not invited]
     
    LaO0.5F0.5BiS2 nanosheets were produced by ultrasonification. A slightly reddish colloidal suspension was obtained by ultrasonification of LaO0.5F0.5BiS2 powder in ethanol. Transmission electron microscope (TEM) images of the dried suspension indicated the nanosheet morphology of LaO0.5F0.5BiS2, and the electron diffraction spots indicated 4-fold symmetry. The thickness of the sheets was 2–6 nm, which corresponded to 2–4 unit cells of the c-axis of LaO0.5F0.5BiS2.
  • Nataly Carolina Rosero-Navarro, Taiki Kinoshita, Akira Miura, Mikio Higuchi, Kiyoharu Tadanaga
    IONICS 23 (6) 1619 - 1624 0947-7047 2017/06 [Refereed][Not invited]
     
    All-solid-state batteries with cathode composites containing high concentration of active materials are required to achieve higher energy densities. Here, a composite cathode containing up to 89 wt% of high-voltage cathode active material (LiNi1/3Mn1/3Co1/3O2) was prepared by covering this with a solution-derived solid electrolyte (argyrodite, Li6PS5Cl) and the incorporation of different content binder (ethyl cellulose). All-solid-state batteries were fabricated using 80Li(2)Sa (TM) 20P(2)S(5) (mol%) glass and indium metal as a solid electrolyte and anode, respectively. The all-solid-state battery with a composite cathode containing 0.5 wt% of ethyl cellulose showed an initial discharge capacity of 45 mAhg(-1) at 25 A degrees C and maintained 91.7% of the discharge capacity after ten cycles, around 30% higher than that obtained for the battery with the composite cathode without a binder.
  • Mirza H. K. Rubel, Takahiro Takei, Nobuhiro Kumada, M. Mozahar Ali, Akira Miura, Kiyoharu Tadanaga, Kengo Oka, Masaki Azuma, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa
    INORGANIC CHEMISTRY 56 (6) 3174 - 3181 0020-1669 2017/03 [Refereed][Not invited]
     
    We have synthesized a new superconducting perovskite bismuth oxide by a facile hydrothermal route at 220 degrees C. The choice of starting materials, their mixing ratios, and the hydrothermal reaction temperature was crucial for obtaining products with superior superconducting properties. The structure of the powder sample was investigated using laboratory X-ray diffraction, high -resolution synchrotron X-ray diffraction (SXRD) data, and electron diffraction (ED) patterns [transmission electron microscopy (TEM) analysis]. The refinement of SXRD data confirmed a simple perovskitetype structure with a cubic cell of a = 4.27864(2) angstrom [space group Pm3m (No. 221)]. Elemental analysis detected magnesium in the final products, and a refinement based on SXRD and inductively coupled plasma data yielded an ideal undistorted simple cubic perovskite-type structure, with the chemical composition (Ba0.62K0.38)(Bi0.92Mg0.08)O-3. ED patterns also confirmed the simple cubic perovskite structure; the cube -shaped microstructures and compositional homogeneity on the nanoscale were verified by scanning electron microscopy and TEM analyses, respectively. The fabricated compound exhibited a large shielding volume fraction of about 98% with a maximum T-c(mag) of similar to 30 K, which was supported by the measured bismuth valence as well. Its electrical resistivity dropped at similar to 21 K, and zero resistivity was observed below 7 K The compound underwent thermal decomposition above 400 degrees C. Finally, the calculated band structure showed a metallic behavior for this hydrothermally synthesized bismuth oxide.
  • Masahiro Tatsumisago, Ryohei Takano, Masashi Nose, Kenji Nagao, Atsutaka Kato, Atsushi Sakuda, Kiyoharu Tadanaga, Akitoshi Hayashi
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 (6) 433 - 437 1882-0743 2017 [Refereed][Not invited]
     
    Low-melting oxide glasses are promising as electrolytes for all-solid-state lithium rechargeable batteries. Glasses in the pseudobinary system Li3BO3-Li2SO4 were prepared by a mechanochemical technique. Raman spectra revealed that the glasses contained no macroanions which form networks but consisted only of Li+ ions and two discrete ortho-oxoanions, BO33+ and SO42-. The density and molar volume increased and elastic moduli decreased with an increase in the Li2SO4 content in the glasses. The heat treatment of the Li3BO3-Li2SO4 glasses at around 300 degrees C brought about the crystallization to form ion conducting glass-ceramics. Electrical conductivities of the glasses and glass-ceramics in this system were maximized with the mixing of Li3BO3 and Li2SO4. The conductivities were higher in the glass-ceramics of the compositions with small amounts of Li2SO4, ranging from 3 x 10(-6) to 1 x 10(-5) S cm(-1) at room temperature, compared to the corresponding glasses. This conductivity enhancement by the heat treatment is probably due to the precipitation of solid solutions with a high temperature Li3BO3 phase. (C) 2017 The Ceramic Society of Japan. All rights reserved.
  • Nataly Carolina Rosero-Navarro, Akira Miura, Mikio Higuchi, Kiyoharu Tadanaga
    JOURNAL OF ELECTRONIC MATERIALS 46 (1) 497 - 501 0361-5235 2017/01 [Refereed][Not invited]
     
    Simultaneous effect of Al2O3 and Li3BO3 additions on sintering behavior and Li-ion conductivity of Li7-xLa2.95Ca0.05ZrTaO12 (LLCZT) garnet electrolyte sintered at 900 degrees C (10 h) is evaluated. The crystal phase and microstructure of the different composites were evaluated by x-ray diffraction and scanning electron microscopy (SEM), respectively. Electrical properties of the composites with high relative densities (95%) were examined by impedance spectroscopy. The cubic phase was formed for LLCZT sintered with 0-0.21 mol of Al2O3 and 0.70 mol-0.80 mol of Li3BO3. The excess of Al2O3 (0.22 mol) led to the formation of secondary phases. SEM observation revealed the good interconnection between LLCZT grains and the distribution of the glassy phase formed by Li3BO3 and Al2O3. Effective combination of 0.21 mol of Al2O3 and 0.80 mol of Li3BO3 produced denser material with high relative density of 95% and high Li-ion conduction of 1 x 10(-4) S/cm at 32 degrees C.
  • Marcela Calpa, Nataly Carolina Rosero-Navarro, Akira Miura, Kiyoharu Tadanaga
    RSC ADVANCES 7 (73) 46499 - 46504 2046-2069 2017 [Refereed][Not invited]
     
    A solid electrolyte with a small particle size, good mechanical properties and high ionic conductivity is required to achieve high energy and power density in the all-solid-state battery. Here, we report an instantaneous preparation of high lithium-ion conducting sulfide solid electrolyte Li7P3S11 by a simple procedure involving a liquid phase process under ultrasonic irradiation and low thermal treatment at 220 degrees C. A short reaction time of 30 min was enough to produce the formation of PS43- units. Subsequent drying and heating processes led to the precipitation of the Li7P3S11 phase with a particle size below 500 nm, achieving high ionic conductivity of 1.0 x 10(-3) S cm(-1) at 22 degrees C and a low activation energy of 12.8 kJ mol(-1).
  • Nataly Carolina Rosero-Navarro, Taira Yamashita, Akira Miura, Mikio Higuchi, Kiyoharu Tadanaga
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 100 (1) 276 - 285 0002-7820 2017/01 [Refereed][Not invited]
     
    Lithium ion conductors with garnet-type structure are promising candidates for applications in all solid-state lithium ion batteries, because these materials present a high chemical stability against Li metal and a rather high Li+ conductivity (10(-3)-10(-4)S/cm). Producing densified Li-ion conductors by lowering sintering temperature is an important issue, which can achieve high Li conductivity in garnet oxide by preventing the evaporation of lithium and a good Li-ion conduction in grain boundary between garnet oxides. In this study, we concentrate on the use of sintering additives to enhance densification and microstructure of Li7La3ZrNbO12 at sintering temperature of 900 degrees C. Glasses in the LiO2-B2O3-SiO2-CaO-Al2O3 (LBSCA) and BaO-B2O3-SiO2-CaO-Al2O3 (BBSCA) system with low softening temperature (<700 degrees C) were used to modify the grain-boundary resistance during sintering process. Lithium compounds with low melting point (<850 degrees C) such as LiF, Li2CO3, and LiOH were also studied to improve the rearrangement of grains during the initial and middle stages of sintering. Among these sintering additives, LBSCA and BBSCA were proved to be better sintering additives at reducing the porosity of the pellets and improving connectivity between the grains. Glass additives produced relative densities of 85-92%, whereas those of lithium compounds were 62-77%. Li7La3ZrNbO12 sintered with 4 wt% of LBSCA at 900 degrees C for 10h achieved a rather high relative density of 85% and total Li-ion conductivity of 0.8x10(-4)S/cm at room temperature (30 degrees C).
  • Anongsack Paseuth, Kazuo Yamagata, Akira Miura, Mikio Higuchi, Kiyoharu Tadanaga
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 100 (1) 343 - 353 0002-7820 2017/01 [Refereed][Not invited]
     
    Metastable c-AlxT1-xN is an important and well-established hard coating in the tool industry. To improve the mechanical and thermal properties, Al-rich c-AlxTi1-xN coatings with controllable preferred crystal orientations were fabricated via low-pressure chemical vapor deposition (LP-CVD) in an industrial plant, using an AlCl3-TiCl4-NH3-Ar-H-2 precursor system. The c-AlxTi1-xN coatings with (100)- and (111)-preferred orientations and average x values of 0.82 and 0.73, respectively, comprised c-Al(Ti)N/c-Ti(Al)N nanolamellae with average compositions of c-Al0.9Ti0.1N/c-Al0.6Ti0.4N and c-Al0.80Ti0.20N/c-Al0.50Ti0.50N; the average lamellar periods were 7.7 and 4.5 nm, respectively. High-resolution transmission electron microscopy indicated that the c-Al(Ti)N/c-Ti(Al)N nanolamellae were modulated along the < 100 > direction, implying coherent spinodal decomposition of c-AlxTi1-xN in the as-deposited state. The hardness of the c-AlxTi1-xN coatings varied from 33 to 36 GPa, depending on the (100)- or (111)-preferred orientation. Residual stress measurements in the as-deposited state showed tensile stress values of 1.8 and 4.6 GPa for the (100)- and (111)-oriented c-AlxT1-xN coatings, respectively. This stress may be generated by the difference in the thermal expansion coefficient of the c-AlxT1-xN coating and the carbide substrate and by coherency stress in the c-Al(Ti)N/c-Ti(Al)N nanolamellae. In situ high-temperature X-Ray diffraction results revealed high thermal stability up to 1000 degrees C.
  • Kiyoharu Tadanaga, Jun-ichiro Oi, Mikio Higuchi
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 79 (2) 303 - 307 0928-0707 2016/08 [Refereed][Not invited]
     
    Zn-Al layered double hydroxide (LDH) thin films intercalated with Eosin Y were prepared by the sol-gel method with hot water treatment. Sol-gel derived amorphous Al2O3-ZnO thin films were immersed in hot water containing Eosin Y. Extended interlayer spacing, in comparison with the Zn-Al LDH with carbonate anions, was observed after immersion in distilled water containing 5 mM Eosin Y at 100 A degrees C for 30 min, indicating that crystals of Zn-Al LDH intercalated with Eosin Y were precipitated on the precursor film. Intercalated Eosin Y was confirmed to have high thermal durability compared with Eosin Y adsorbed on the LDH surface. A cell consisting of the heat-treated thin film of Zn-Al LDH intercalated with Eosin Y on fluorine-doped tin oxide (FTO)-coated glass, triiodide/iodide electrolyte, and Pt-loaded FTO glass was confirmed to work as a solar cell under visible light irradiation. Zn-Al layered double hydroxide thin films intercalated with Eosin Y were prepared by the sol-gel method with hot water treatment. Intercalated Eosin Y is confirmed to have high thermal durability. [GRAPHICS]
  • Akira Miura, Carolina Rosero-Navarro, Yuji Masubuchi, Mikio Higuchi, Shinichi Kikkawa, Kiyoharu Tadanaga
    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION 55 (28) 7963 - 7967 1433-7851 2016/07 [Refereed][Not invited]
     
    The catalytic activity of manganese oxynitrides in the oxygen reduction reaction (ORR) was investigated in alkaline solutions to clarify the effect of the incorporated nitrogen atoms on the ORR activity. These oxynitrides, with rock-saltlike structures with different nitrogen contents, were synthesized by reacting MnO, Mn2O3, or MnO2 with molten NaNH2 at 240-280 degrees C. The anion contents and the Mn valence states were determined by combustion analysis, powder X-ray diffraction, and X-ray absorption near-edge structure analysis. An increase in the nitrogen content of rock-salt-based manganese oxynitrides increases the valence of the manganese ions and reinforces the catalytic activity for the ORR in 1m KOH solution. Nearly single-electron occupancy of the antibonding e(g) states and highly covalent Mn-N bonding thus enhance the ORR activity of nitrogen-rich manganese oxynitrides.
  • Yuta Fujii, Yusaku Suto, Akira Miura, Mikio Higuchi, Kiyoharu Tadanaga
    CHEMISTRY LETTERS 45 (6) 652 - 654 0366-7022 2016/06 [Refereed][Not invited]
     
    An all-solid-state lithium secondary battery using a NiPS3 electrode and a 80Li(2)S center dot 20P(2)S(5) glass solid electrolyte was fabricated, and the charge-discharge cycle performance of the corresponding all-solid-state cell was investigated. This all solid-state cell exhibited a stable reversible capacity of about 80 mAh g(-1) after 30 cycles with a current density of 64 mu A cm(-2) at room temperature. This suggests that NiPS3 has a potential as an electrode active material in all-solid-state lithium secondary batteries using Li2S-P2S5 solid electrolytes.
  • Y. Mizuguchi, A. Miura, A. Nishida, O. Miura, K. Tadanaga, N. Kumada, C. H. Lee, E. Magome, C. Moriyoshi, Y. Kuroiwa
    JOURNAL OF APPLIED PHYSICS 119 (15) 155103  0021-8979 2016/04 [Refereed][Not invited]
     
    We examined the crystal structure of the new thermoelectric material LaOBiS2-xSex, whose thermoelectric performance is enhanced by Se substitution, by using powder synchrotron X-ray diffraction and Rietveld refinement. The emergence of metallic conductivity and enhancement of the thermoelectric power factor of LaOBiS2-xSex can be explained with the higher in-plane chemical pressure caused by the increase of Se concentration at the in-plane Ch1 site (Ch = S, Se). High-temperature X-ray diffraction measurements for optimally substituted LaOBiSSe revealed anomalously large atomic displacement parameters (U-iso) for Bi and Ch atoms in the BiCh(2) conduction layers. The anisotropic analysis of the atomic displacement parameters (U-11 and U-33) for the in-plane Bi and Ch1 sites suggested that Bi atoms exhibit large atomic displacement along the c-axis direction above 300 K, which could be the origin of the low thermal conductivity in LaOBiSSe. The large Bi vibration along the c-axis direction could be related to in-plane rattling, which is a new strategy for attaining low thermal conductivity and phonon-glass-electron-crystal states. Published by AIP Publishing.
  • Takuya Matsuyama, Ryohei Takano, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    SOLID STATE IONICS 285 122 - 125 0167-2738 2016/02 [Refereed][Not invited]
     
    Amorphous TiS4 (a-TiS4) thin film electrode was deposited on the garnet-type Li7La3Zr2O12 (LLZ) solid electrolyte pellet sintered at 1230 degrees C by the pulsed laser deposition method. The a-TiS4 electrode was dense and its thickness was ca. 400 nm and good contacts between the electrode and the electrolyte were obtained. All-solid-state cells of Li/LLZ/a-TiS4 operated as a lithium secondary battery at 25 degrees C, and showed reversible capacity of about 500 mAh per gram of a-TiS4 at 0.010 mA cm(-2) and good cycle performance for 15 cycles. Interfacial resistance between a-TiS4 electrode and LIZ electrolyte was almost constant during charge-discharge cycling. A pelletized LLZ was prepared with Li3BO3 at a lower sintering temperature of 900 degrees C, and the obtained LLZ-Li3BO3 pellet with the conductivity of 1.0 x 10(-4) S cm(-1) at 25 degrees C was applied to all-solid-state cells. The cells with LLZ-Li3BO3 and a-TiS4 also operated as a lithium secondary battery. The reversible capacity of the cells using LLZ-Li3BO3 was about 480 mAh per gram of a-TiS4 at a current density of 0.020 mA cm(-2). (C) 2015 Elsevier B.V. All rights reserved.
  • N. C. Rosero-Navarro, T. Yamashita, A. Miura, M. Higuchi, K. Tadanaga
    SOLID STATE IONICS 285 6 - 12 0167-2738 2016/02 [Refereed][Not invited]
     
    Li7La3(Zr-2 (-) Nb-x(x))O-12 (LLZNbO, x = 0-1.5) was prepared using sol-gel process at low temperatures. Additives (LiBO2 and Li3BO3) were used to improve the sintering of the ceramic electrolyte at low temperatures. XRD patterns of the calcined powder displayed the formation of cubic garnet phase between 600 and 700 degrees C in composition with higher Nb content (LLZNbO, x >= 0.5). The density of composites with additives sintered at 900 degrees C achieves 90%. In composites sintered with LiBO2, the presence of La2Zr2O7 was detected, whereas single cubic phase was obtained for the composites sintered with Li3BO3. The ion conductivity attained was 7 x 10(-5) S/cm at 30 degrees C using 6.5 wt% Li3BO3 (900 degrees C), representing enhancement by more than two orders of magnitude compared to the material without additives. Improvements of Li ion conductivity can be interpreted by the enhanced relative density as the result of the rearrangement of particles produced by adequate concentration of the additive. (C) 2015 Elsevier B.V. All rights reserved.
  • Akira Miura, Yoshikazu Mizuguchi, Takahiro Takei, Nobuhiro Kumada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, Kiyoharu Tadanaga
    SOLID STATE COMMUNICATIONS 227 19 - 22 0038-1098 2016/01 [Refereed][Not invited]
     
    The band gaps of isostructural Bi2OS2 and LaOBiS2 were examined using optical absorption and discussed with the band structures calculated based on the crystal structures determined, using synchrotron X-ray diffraction. The Bi 6p and S 3p orbitals in the Bi-S plane were computationally predicted to constitute the bands near the Fermi level. The optical reflectance spectra of Bi2OS2 and LaOBiS2 showed optical band gaps of similar to 1.0 eV, which were close to the computationally calculated direct band gaps of similar to 0.8 eV. Our results show that Bi2OS2 and LaOBiS2 are semiconductors containing direct band gaps of 0.8-1.0 eV, and they are suggested to be candidates for optoelectronic materials in the near-infrared region without highly toxic elements. (C) 2015 Elsevier Ltd. All rights reserved.
  • Mirza H. K. Rubel, Takahiro Takei, Nobuhiro Kumada, M. Mozahar Ali, Akira Miura, Kiyoharu Tadanaga, Kengo Oka, Masaki Azuma, Masatomo Yashima, Kotaro Fujii, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, James R. Hester, Maxim Aydeev
    CHEMISTRY OF MATERIALS 28 (2) 459 - 465 0897-4756 2016/01 [Refereed][Not invited]
     
    Double-perovskite Bi oxides are a new series of superconducting materials, and their crystal structure and superconducting properties are under investigation. In this paper, we describe the synthesis and characterization of a new double-perovskite material that has an increased superconductive transition temperature of 31.5 K. The structure of the material was examined using powder neutron diffraction (ND), synchrotron X-ray diffraction (SXRD), and transmission electron microscopy (TEM). Rietveld refinement of the sample based on ND and SXRD data confirmed an A-site-ordered (K-1.00)(Ba-1.00)(3)(Bi0.89Na0.11)(4)O-12 double-perovskite-type structure with the space group Im (3) over barm (No. 229). This structural analysis revealed the incorporation of Na with Bi in the structure and a bent bond between (Na, Bi)-O-(Na, Bi). TEM analyses also confirmed a cubic double-perovskite structure. This hydrothermally synthesized compound exhibited a large shielding volume fraction, exceeding 100%, with onset of superconductivity at similar to 31.5 K. Its electrical resistivity dropped near onset at similar to 28 K, and zero resistivity was confirmed below 13 K. The calculated band structure revealed that the metallicity of the compound and the flatness of the conduction bands near the Fermi level (E-F) are important for the appearance of superconductivity.
  • Akira Miura, Yoshikazu Mizuguchi, Tsuyoshi Sugawara, Yongming Wang, Takahiro Takei, Nobuhiro Kumada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, Osuke Miura, Kiyoharu Tadanaga
    INORGANIC CHEMISTRY 54 (21) 10462 - 10467 0020-1669 2015/11 [Refereed][Not invited]
     
    The relationship between the structure and superconductivity of Bi4O4S3 powders synthesized by heating under ambient and high pressures was investigated using synchrotron X-ray diffraction, Raman spectroscopy, and transmission electron microscopy (TEM) observation. The Bi4O4S3 powders synthesized under ambient pressure exhibited a strong superconductivity (diamagnetic) signal and zero resistivity below similar to 4.5 K, while the Bi4O4S3 powder synthesized by the high-pressure method exhibited a low-intensity signal down to 2 K. Further annealing of the latter Bi4O4S3 powder under ambient pressure led to the development of a strong signal and zero resistivity. The crystal structures of all Bi4O4S3 phases consisted of Bi4O4Bi2S4 blocks including a Bi-S layer and anion(s) sandwiched between Bi4O4Bi2S4 blocks, but minor structural differences were detected. A comparison of the structures of the superconductive and nonsuperconductive Bi4O4S3 samples suggested that the superconductive Bi4O4S3 phases had slightly smaller lattice parameters. The average structures of the superconductive Bi4O4S3 phases were characterized by a slightly shorter and less bent BiS plane. Raman spectroscopy detected vibration of the S-O bonds, which can be attributed to sandwiched anion(s) such as SO42-. TEM observation showed stacking faults in the superconductive Bi4O4S3 phases, which indicated local fluctuation of the average structures. The observed superconductivity of Bi4O4S3 was discussed based on impurity phases, enhanced hybridization of the px and py orbitals of the Bi-S plane within Bi4O4Bi2S4 blocks, local fluctuation of the average structures, compositional deviation related to suspicious anion(s) sandwiched between Bi4O4Bi2S4 blocks, and the possibility of suppression of the charge-density-wave state by enriched carrier concentrations.
  • Yoshikazu Mizuguchi, Akira Miura, Joe Kajitani, Takafumi Hiroi, Osuke Miura, Kiyoharu Tadanaga, Nobuhiro Kumada, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa
    SCIENTIFIC REPORTS 5 14968  2045-2322 2015/10 [Refereed][Not invited]
     
    BiCh(2)-based compounds (Ch: S, Se) are a new series of layered superconductors, and the mechanisms for the emergence of superconductivity in these materials have not yet been elucidated. In this study, we investigate the relationship between crystal structure and superconducting properties of the BiCh(2)-based superconductor family, specifically, optimally doped Ce1-xNdxO0.5F0.5BiS2 and LaO0.5F0.5Bi(S1-ySey)(2). We use powder synchrotron X-ray diffraction to determine the crystal structures. We show that the structure parameter essential for the emergence of bulk superconductivity in both systems is the in-plane chemical pressure, rather than Bi-Ch bond lengths or in-plane Ch-Bi-Ch bond angle. Furthermore, we show that the superconducting transition temperature for all REO(0.5)F(0.5)BiCh(2) superconductors can be determined from the in-plane chemical pressure.
  • So Yubuchi, Shingo Teragawa, Keigo Aso, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF POWER SOURCES 293 941 - 945 0378-7753 2015/10 [Refereed][Not invited]
     
    A Li6PS5Cl solid electrolyte was successfully prepared by dissolution-reprecipitation process via ethanol solution. An ionic conductivity of the Li6PS5Cl solid electrolyte from the homogeneous ethanol solution was 1.4 x 10(-5) S cm(-1) at room temperature. LiCoO2 particles were coated with the Li6PS5Cl electrolyte via ethanol solution to form favorable electrode-electrolyte interface with a large contact areas. An all-solid-state cell using the electrolyte-coated LiCoO2 operated as a rechargeable battery and showed the initial discharge capacity of 45 rnAh g(-1) at 25 degrees C. (C) 2015 Elsevier B.V. All rights reserved.
  • Atsuhiko Onuma, Jun Kawaji, Shuichi Suzuki, Makoto Morishima, Yoshiyuki Takamori, Naoki Asano, Kiyoharu Tadanaga
    SOLID STATE IONICS 277 72 - 76 0167-2738 2015/09 [Refereed][Not invited]
     
    To improve the proton conductivities of a polymer electrolyte membrane which is composed of multi-block copolymers, in low humidity conditions, the effect of adding hydrated titanium oxide into a membrane was investigated. Membranes containing hydrated titanium oxide were prepared by using tetraethoxy titanium. Membranes containing hydrated titanium oxide showed higher proton conductivity than the membrane not containing the additives regardless of humidity. This result showed that adding hydrated titanium oxide improved proton conductivity. By contrast, all the polymer electrolyte membranes showed almost the same water content rate. The content rates of hydrated titanium oxide in membranes were lower than 3 wt%. Thus, adding hydrated titanium oxide was not considered to affect the water content rate of membranes. This result showed that proton conductivity was improved by adding hydrated titanium oxide without increasing water content rate. From the scanning transmission electron microscope observation, micro-phase-separated structures were observed clearly in membranes containing hydrated titanium oxide. It seemed that hydrated titanium oxide enhanced the hydrophilic sengments aggregation during the film-forming process. Probably, the well-defined hydrophilic domains functioned as proton paths and enhanced the proton conductivity of the membrane. (C) 2015 Elsevier B.V. All rights reserved.
  • Akira Miura, Kiyoharu Tadanaga, Eisuke Magome, Chikako Moriyoshi, Yoshihiro Kuroiwa, Takei Takahiro, Nobuhiro Kumada
    JOURNAL OF SOLID STATE CHEMISTRY 229 272 - 277 0022-4596 2015/09 [Refereed][Not invited]
     
    Crystallographic and electronic structures of Nb-, Mo-, Ta-, and W-based layered oxides, oxynitrides, and nitrides were analyzed to elucidate the structural relationship between layered oxides and nitrides consisting of octahedral and trigonal-prismatic layers. The electron density, as derived by synchrotron X-ray analysis of LiNbO2 and Ta5-x(O,N)(6), showed orbital overlaps between Nb-Nb and Ta-Ta metals in the trigonal layers. Computational calculations based on DFT exhibited that these overlaps stabilized these structures by lowering the hybridization states composed of the d(xy), d(x2-y2), and d(z2) orbitals below the Fermi level. Crystal structures and formation energies suggest that tuning the Fermi level through the substitutions and vacancies of the cation/anion sites determines the structural preferences of the coordination. The properties and syntheses of these compounds are briefly described. This study enhances the understanding of layered oxides, oxynitrides, and nitrides to further the development of new synthetic approaches, compounds, and applications. (C) 2015 Elsevier Inc. All rights reserved.
  • Mirza H. K. Rubel, Takahiro Takei, Nobuhiro Kumada, M. M. Ali, Akira Miura, Kiyoharu Tadanaga, K. Oka, M. Azuma, E. Magomae, C. Moriyoshi, Y. Kuroiwa
    JOURNAL OF ALLOYS AND COMPOUNDS 634 208 - 214 0925-8388 2015/06 [Refereed][Not invited]
     
    A new type of bismuth-oxide-based superconductor was prepared by a hydrothermal reaction at 240 degrees C. The synchrotron X-ray powder diffraction pattern reveals a simple perovskite-type structure with a cubic cell of a = 4.28877(1) angstrom with space group Pm-(3) over barm. The chemical composition of this cubic perovskite oxide was formulated as (Ba0.82K0.18)(Bi0.53Pb0.47)O-3 after structural refinement using synchrotron X-ray powder diffraction and chemical analysis data. The cubic microstructure and compositional homogeneity were confirmed by scanning electron microscopy analysis. This compound exhibited a diamagnetic signal with a shielding volume fraction of similar to 64% with an onset of approximately 22.8 K. Its resistivity started to drop at similar to 15 K, and zero resistivity was observed below 4 K. The thermal decomposition of this simple perovskite structure started above 600 degrees C. Finally, the calculated band structure also exhibited metallic behavior at ambient conditions. (C) 2015 Elsevier B.V. All rights reserved.
  • Kiyoharu Tadanaga, Akihiro Yamaguchi, Akitoshi Hayashi, Masahiro Tatsumisago, Jadra Mosa, Mario Aparicio
    Journal of Asian Ceramic Societies 3 (1) 88 - 91 2187-0764 2015/03/01 [Refereed][Not invited]
     
    Spinel Li4Ti5O12 thin films were prepared by a mist CVD process, using an aqueous solution of lithium nitrate and a water-soluble titanium lactate complex as the source of Li and Ti, respectively. In this process, mist particles ultrasonically atomized from a source aqueous solution were transferred by nitrogen gas to a heating substrate to prepare thin films. Scanning electron microscopy observation showed that thin films obtained by this process were dense and smooth, and thin films with a thickness of about 500nm were obtained. In the X-ray diffraction analysis, formation of Li4Ti5O12 spinel phase was confirmed in the obtained thin film sintered at 700°C for 4h. The cell with the thin films as an electrode exhibited a capacity of about 110mAhg-1, and the cell showed good cycling performance during 10 cycles.
  • Naoya Hirata, Kiyoharu Tadanaga, Masahiro Tatsumisago
    MATERIALS RESEARCH BULLETIN 62 1 - 4 0025-5408 2015/02 [Refereed][Not invited]
     
    Zn-Cr layered double hydroxides (LDHs) intercalated with inorganic anions (CO32-, Cl-, SO42- and NO3-) were synthesized by the co-precipitation method and the anion exchange process. The photocatalytic activity of the LDHs was studied by O-2 evolution from aqueous solution of AgNO3 as a sacrificial agent. All the prepared LDHs showed photocatalytic activity under either UV and/or visible light irradiation. Besides, the interlayer anions affected the photocatalytic activity of the LDHs. After irradiation, Ag particles were formed on the LDHs by accepting the electrons generated during the photocatalytic reaction. (C) 2014 Elsevier Ltd. All rights reserved.
  • Kiyoharu Tadanaga, Kohei Igarashi, Takashi Kubota, Akira Miura, Mikio Higuchi
    ECS Transactions 69 (17) 385 - 389 1938-6737 2015 [Refereed][Not invited]
     
    Layered double hydroxides (LDHs) intercalated with CO3 2- show high hydroxide ion conductivity of the order of 10-3 S cm-1 under 80% relative humidity. In the present study, (Ni, Mn)-Al LDHs and (Ni, Mn)-Fe LDHs intercalated with CO32- were prepared. The conductivity of (Ni, Mn)-Al LDH and (Ni, Mn)-Fe LDH was higher than that of Ni-Al LDH or Ni-Fe LDH. These LDHs were applied to the catalyst layer in an alkaline fuel cell for the improvement of the oxygen reduction reaction (ORR) at the triple phase boundary (TPB) in the catalyst layer. The addition of LDHs to the catalyst layer increased the current for ORR, indicating that hydroxide ion conducting LDHs introduced OH- conducting paths and increased TPB region within the catalyst layer. Above all, the addition of (Ni, Mn)-Fe LDH to the catalyst layer more effectively increased the reduction current for ORR than the addition of (Ni, Mn)-Al LDHs or Ni-Fe LDH. H2-O2 fuel cells with Ni-Al or Mg-Al LDHs as an electrolyte and MnO2 as the cathode catalyst were fabricated. The H2-O2 fuel cells were confirmed to be operated.
  • Rie Makiura, Shingo Teragawa, Kohei Tsuchiyama, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    DALTON TRANSACTIONS 44 (34) 15279 - 15285 1477-9226 2015 [Refereed][Not invited]
     
    Surface modification of inorganic objects with metal-organic frameworks (MOFs) - organic-inorganic hybrid framework materials with infinite networks - opens wide windows for potential applications. In order to derive a target property, the key is the ability to fine tune the degree of modification. Solution-based step-by-step growth techniques provide excellent control of layer thickness which can be varied with the number of deposition cycles. Such techniques with MOFs have been mainly applied to flat substrates, but not to particle surfaces before. Here, we present the facile surface modification of inorganic particles with a framework compound under operationally simple ambient conditions. A solution-based sequential technique involving the alternate immersion of LiCoO2 (LCO) - a positive electrode material for a lithium ion battery - into FeCl2 center dot 4H(2)O and K-3[Fe(CN)(6)] solutions results in the formation of Prussian blue (PB) nanolayers on the surface of the LCO particles (PBNL@LCO). The PB growth is finely controlled by the number of immersion cycles. An electrochemical cell with PBNL@LCO as a positive electrode material exhibits a discharge capacity close to the specific capacity of LCO. The results open a new direction for creating suitable interfacial conditions between electrode materials and electrolytes in secondary battery materials.
  • Kiyoharu Tadanaga, Hiromi Egawa, Akitoshi Hayashi, Masahiro Tatsumisago, Jadra Mosa, Mario Aparicio, Alicia Duran
    JOURNAL OF POWER SOURCES 273 844 - 847 0378-7753 2015/01 [Refereed][Not invited]
     
    Thin films of garnet-type Al-doped Li7La3Zr2O12 (LLZ) are prepared by the sol-gel process. Thin films are prepared on MgO substrates by a dip-coating process using a precursor sol from Zr-alkoxide and Li, La and Al nitrates. After the dip-coating, the dried films are calcined at 450 degrees C to get precursor films. When the precursor films are heat-treated at 900 degrees C in an alumina crucible, La2Zr2O7 is mainly obtained. With coexistence of Li2CO3 powders in the crucible during the heat-treatment at 900 degrees C, thin film of polycrystalline cubic LLZ is obtained. Addition of an ionic surfactant, lithium dodecylsulfate, improves the quality of the thin films, and the thin film heat-treated at 900 degrees C with coexistence of Li2CO3 powders in the crucible shows the ionic conductivity of 2.4 x 10(-6) S cm(-1) at 25 degrees C. (C) 2014 Elsevier B.V. All rights reserved.
  • J. Mosa, M. Aparicio, K. Tadanaga, A. Hayashi, M. Tatsumisago
    ELECTROCHIMICA ACTA 149 293 - 299 0013-4686 2014/12 [Refereed][Not invited]
     
    Rechargeable thin-film batteries have recently become the topic of widespread research for use as efficient energy storage devices. Spinel Li4Ti5O12 has been considered as one of the most prospective anode materials for Li-ion batteries because of its excellent reversibility and long cycle life. We report here the sol-gel synthesis and coating preparation of spinel thin-film Li4Ti5O12 electrodes for Li-ion microbatteries using lithium ethoxide produced in situ that reacts with titanium alkoxide to produce the precursor solution without particle precipitation. This synthesis procedure reduces the thermal treatment to obtain a pure phase at only 700 degrees C and 15 minutes. The physical and structural characterization of the 300 nm Li4Ti5O12 coatings shows a very homogeneous distribution of elements and a pure spinel phase. Galvanostatic discharge-charge tests indicate maximum discharge capacities of 152 mA h g(-1) when the material is treated at 700 degrees C for 15 minutes. (C) 2014 Elsevier Ltd. All rights reserved.
  • Masahiro Tatsumisago, Ryohei Takano, Kiyoharu Tadanaga, Akitoshi Hayashi
    JOURNAL OF POWER SOURCES 270 603 - 607 0378-7753 2014/12 [Refereed][Not invited]
     
    Newly designed oxide glass ceramic electrolyte of Li2.9B0.9S0.1O3.1 with high Li+ ion conductivity and low melting property was prepared by mechanical milling and subsequent heat treatment at 290 degrees C. This material showed 1.4 x 10(-5) S cm(-1) at room temperature and excellent deformation properties to obtain powder-compressed pellets with low interfacial resistance like in the case of sulfide solid electrolytes. The glass-ceramic exhibited favorable mechanical properties to form favorable solid-solid contacts in solid-state batteries by pressing without high temperature heat treatments. All-solid-state In/LiCoO2 cells using these oxide glass-ceramic electrolytes operated as secondary batteries at room temperature. (C) 2014 Elsevier B.V. All rights reserved.
  • Aki Ueda, Mikio Higuchi, Daiki Yamada, Sho Namiki, Takayo Ogawa, Satoshi Wada, Kiyoharu Tadanaga
    JOURNAL OF CRYSTAL GROWTH 404 152 - 156 0022-0248 2014/10 [Refereed][Not invited]
     
    Cr,Nd:CaYAlO4 single crystals were grown by the floating zone method and their spectroscopic properties were investigated. Many voids were observed in the crystals grown with a stoichiometric feed rod even at a relatively low growth rate of 2.5 mm/h, while a void-free crystal was grown at the same growth rate using a feed rod the composition of which was Y-rich to Ca. These results indicate that voids were attributable to constitutional supercooling due to the segregation of main constituents caused by the difference in congruent and stoichiometric compositions. The as-grown crystals were deep red and showed strong absorption in the wavelength region of 320-600 nm. The absorption cross section for sigma-polarization at 430 nm, where Cr,Nd:YAG has the maximum absorption, is about 1160 x 10(-20) cm(2), which is 165 times as large as that of Cr,Nd:YAG. By pumping at 400 nm, which is a pad of the absorption band of Cr3+ Cr,Nd:CaYAlO4 showed fluorescence bands around 900 am and 1080 nm by Nd3+ indicating energy transfer from Cr3+ to Nd3+ in the crystal. Cr,Nd:CaYAlO4 single crystals are therefore one of the promising gain media for solar-pumped solid state laser systems. (C) 2014 Elsevier B.V. All rights reserved.
  • Yuji Arishige, Daiju Kubo, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    SOLID STATE IONICS 262 238 - 240 0167-2738 2014/09 [Refereed][Not invited]
     
    This paper reports a novel electrochemical oxygen separation process using a hydroxide ion conductor as an electrolyte. In this study, we used Ni-Fe layered double hydroxide (LDH) intercalated with CO32- (Ni-Fe CO32- LDH) as a hydroxide ion conductive material. Ni-Fe CO32- LDH was prepared using the co-precipitation method. Electrodes using Pt/C as a catalyst and Ni-Fe CO32- LDH as an ionomer were prepared and a membrane reactor for oxygen separation using Ni-Fe CO32- LDH as an electrolyte was fabricated. The electrochemical oxygen product flow was confirmed to be proportional to the external current density, and thus the membrane functioned at 50 degrees C under 70% of relative humidity and an electrical potential gradient. (C) 2013 Elsevier B.V. All rights reserved.
  • Kiyoharu Tadanaga, Akihiro Yamaguchi, Atsushi Sakuda, Akitoshi Hayashi, Masahiro Tatsumisago, Alicia Duran, Mario Aparacio
    MATERIALS RESEARCH BULLETIN 53 196 - 198 0025-5408 2014/05 [Refereed][Not invited]
     
    LiMn2O4 cathode thin films for thin film lithium secondary batteries were prepared by using so-called the "mist CVD process", employing an aqueous solution of lithium acetate and manganese acetate, as the source of Li and Mn, respectively. The aqueous solution of starting materials was ultrasonically atomized to form mist particles, and mists were transferred by nitrogen gas to silica glass substrate to form thin films. FE-SEM observation revealed that thin films obtained by this process were dense and smooth, and thin films with a thickness of about 750 nm were obtained. The electrochemical cell with the thin films obtained by sintering at 700 degrees C exhibited a capacity of about 80 mAh/g, and the cell showed good cycling performance during 10 cycles. (C) 2014 Elsevier Ltd. All rights reserved.
  • Ryohei Takano, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    SOLID STATE IONICS 255 104 - 107 0167-2738 2014/02 [Refereed][Not invited]
     
    Al-doped Li2La3Zr2O12 (LLZ) was prepared by a sol-gel process using lithium nitrate, lanthanum nitrate hexahydrate, zirconium propoxide and aluminum tri-sec-butoxide as starting materials. Single phase of cubic LLZ was obtained by a heat treatment at 700 degrees C, which is lower than that in the solid state reaction process. The LLZ powders were sintered at 900 degrees C using LiBO2 or Li3BO3 to form composite solid electrolyte. In the composite sintered with LiBO2, La2Zr2O7 was formed as an impurity phase. On the other hand, in the composite sintered with Li3BO3, single phase of cubic LLZ was obtained. The composite of Al-doped LLZ and Li3BO3 sintered at 900 degrees C showed the total electrical conductivity of 1.9 x 10(-5) S cm(-1), while Al-doped LLZ pellet without additives showed 1.6 x 10(-6) S cm(-1). (C) 2013 Elsevier B.V. All rights reserved.
  • Shingo Teragawa, Keigo Aso, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF POWER SOURCES 248 939 - 942 0378-7753 2014/02 [Refereed][Not invited]
     
    Electrode solid electrolyte composite materials for all-solid-state lithium batteries were prepared by coating of the Li2S-P2S5 solid electrolyte onto LiCoO2 particles using a N-methylformamide (NMF) solution of 80Li(2)S-20P(2)S(5) (mol%) solid electrolyte. SEM and EDX analysis showed that the Li2S P2S5 solid electrolyte was uniformly coated on LiCoO2 particles. The all-solid-state cell using the LiCoO2 particles coated with the solid electrolyte showed higher charge discharge capacity than the cells using uncoated LiCoO2 particles. (C) 2013 Elsevier B.V. All rights reserved.
  • Kazushi Shimamoto, Kiyoharu Tadanaga, Masahiro Tatsumisago
    JOURNAL OF POWER SOURCES 248 396 - 399 0378-7753 2014/02 [Refereed][Not invited]
     
    Electrode electrolyte composites of MnO2 active material, acetylene black (AB), and SiO2 Nafion solid electrolyte were prepared using the sot gel process to form good solid solid interfaces. The composites were obtained by the addition of MnO2 and AB into a sol of hydrolyzed tetraethoxysilane with Nafion, and successive solidification of the precursor sol. Scanning electron microscope and energy dispersive X-ray spectroscopy measurements show that good solid solid interface is formed between electrodes and solid electrolytes in the composites. All-solid-state hybrid capacitors were fabricated using the composites or the hand-grinding mixture of MnO2, AB and SiO2 Nafion powder as positive electrodes, activated carbon powder as a negative electrode, and phosphosilicate gel as a solid electrolyte. The allsolid-state hybrid capacitors using the composites exhibit larger capacitances and better rate performance than the capacitors using the electrode prepared by hand-mixing of powders. Specific discharge capacitances of the capacitor with the composite are 85 F g(-1) for the one with the composite electrode and 48 F g(-1) for the one with the hand-mixed electrode, at 1 mA cm-2. Moreover, the all-solid-state capacitors using the composite electrode can be operated at temperatures between -30 degrees C and 60 degrees C. (C) 2013 Elsevier B.V. All rights reserved.
  • Shingo Teragawa, Keigo Aso, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF MATERIALS CHEMISTRY A 2 (14) 5095 - 5099 2050-7488 2014 [Refereed][Not invited]
     
    A Li3PS4 solid electrolyte was directly synthesized from Li2S and P2S5 by a liquid-phase reaction using N-methylformamide (NMF) and n-hexane as reaction media. After the reaction of Li2S and P2S5, a yellow NMF solution was obtained. The NMF solution was dried at 180 degrees C for 3 hours under vacuum to remove NMF and to obtain a powder. A crystalline phase of the obtained powder from the NMF solution was attributed to Li3PS4 crystals, and the ionic conductivity of the obtained powder was 2.3 x 10(-6) S cm(-1) at 25 degrees C. Electrode-electrolyte composite materials for all-solid-state lithium batteries were prepared by coating the Li3PS4 solid electrolyte onto LiCoO2 particles using the NMF solution. SEM and EDX analysis showed that LiCoO2 particles were uniformly coated with the Li3PS4 solid electrolyte. An all-solid-state cell using the LiCoO2 particles coated with the Li3PS4 solid electrolyte as a positive electrode operated as a secondary battery.
  • J. Mosa, J. F. Velez, J. J. Reinosa, M. Aparicio, A. Yamaguchi, K. Tadanaga, M. Tatsumisago
    JOURNAL OF POWER SOURCES 244 482 - 487 0378-7753 2013/12 [Refereed][Not invited]
     
    Spinel Li4Ti5O12 has been considered as one of the most prospective anode materials for Li-ion microbatteries. Homogeneous, transparent and crack-free Li4Ti5O12 coatings with thickness around 110 nm have been prepared by dipping gold-coated quartz substrates in sols prepared using titanium isopropoxide and lithium acetate. The influence of the thermal treatment on the phase composition, structure and electrochemical behavior was studied. Rutile TiO2 (considered as an impurity in this study) is only detected in the coatings treated at 700 degrees C. XPS and TOF-SIMS depth profiles show a homogeneous distribution, with a Li increase and Ti reduction at the surface. Electrochemical characterization of samples treated at 600 degrees C presents a redox reaction around 1.55 V indicating that the film is simple phase of Li4Ti5O12. The shift to slightly lower voltage in samples treated at 700 degrees C is a consequence of Rutile impurities. Larger capacity and good reversibility in the sample heat-treated at 600 degrees C can be attributed to high crystallinity of Li4Ti5O12 and phase purity. RBS analysis specifies a composition close to Li4Ti5O12 in the case of the pristine and charged samples, and Li7Ti5O12 for the discharged sample. Surface XPS study confirms the presence of an outermost layer containing LiF and Li2CO3. (C) 2012 Elsevier B.V. All rights reserved.
  • Shingo Teragawa, Keigo Aso, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    CHEMISTRY LETTERS 42 (11) 1435 - 1437 0366-7022 2013/11 [Refereed][Not invited]
     
    Li2S-P2S5 solid electrolyte (SE) powders were successfully reprecipitated from a liquid phase. Powders of 80Li(2)S center dot 20P(2)S(5) (mol %) SE originally prepared by mechanical milling were dissolved in N-methylformamide (NMF) and a homogeneous solution was obtained. The NMF solution was dried at 150 degrees C for 3 h under vacuum to obtain precipitates. The main structural unit in the obtained powder was PS43-. The crystalline phase of the powders was confirmed to be Li3PS4, and ionic conductivity was 2.6 x 10(-6) cm(-1).
  • Kiyoharu Tadanaga, Koji Morita, Keisuke Mori, Masahiro Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 68 (2) 341 - 345 0928-0707 2013/11 [Refereed][Not invited]
     
    Silica nanoparticles with high concentration were prepared by the sol-gel process based on the Stober method using tetraethoxysilane as a starting material. It was found that silica sol with about 4 wt% in concentration and with a diameter of about 10 nm was obtained by controlling the reaction conditions in the Stober process. By removing the solvent under a reduced pressure, the particle concentration was increased up to 15 wt% without aggregation.
  • Kiyoharu Tadanaga
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 121 (1417) 819 - 824 1882-0743 2013/09 [Refereed][Not invited]
     
    Surface morphology of materials brings various new properties to the surface, and thus, the control of the surface morphology is very important. In this paper, surface morphology control of sol-gel derived films using several processes has been reviewed. Hot water treatment (bottom up process), combination of UV-irradiation and chemical etching (top down process), and micropattern formation using a hydrophobic-hydrophilic patterned surface were reported. (C)2013 The Ceramic Society of Japan. All rights reserved.
  • Kiyoharu Tadanaga, Ryohei Takano, Takahiro Ichinose, Shigeo Mori, Akitoshi Hayashi, Masahiro Tatsumisago
    ELECTROCHEMISTRY COMMUNICATIONS 33 51 - 54 1388-2481 2013/08 [Refereed][Not invited]
     
    Highly lithium ion conductive composites with Al-doped Li7La3Zr2O12 (LLZ) and amorphous Li3BO3 were prepared from sol-gel derived precursor powders of LLZ and Li3BO3. Precursor LLZ powders with cubic phase were obtained by a heat treatment of the precursor dried gel at 600 degrees C. Pellets of the mixture of the obtained LLZ and Li3BO3 were first held at 700 degrees C, and then successively sintered at 900 degrees C. Density of the sintered pellet with Li3BO3 was larger than that of the pellet without Li3BO3. From the TEM observation, the pellets were found to consist of cubic LLZ and amorphous Li3BO3. Total electrical conductivity of the obtained LLZ-Li3BO3 composite was 1 x 10(-4) Scm(-1) at 30 degrees C. (c) 2013 Elsevier B.V. All rights reserved.
  • Daiju Kubo, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    Journal of Materials Chemistry A 1 (23) 6804 - 6809 2050-7488 2013/06/21 [Refereed][Not invited]
     
    This paper reports the application of Ni-Fe layered double hydroxides (LDHs) intercalated with CO32- (Ni-Fe CO3 2- LDH) to a catalyst layer of a rechargeable metal-air battery using an alkaline electrolyte. Ni-Fe CO32- LDH is found to play multifunctional roles in the catalyst layer as a mixed conductor with hydroxide ions and electrons, and also as an electrocatalyst. The air electrode with Ni-Fe CO32- LDH shows superior performance to all electrodes with other LDHs, indicating that Ni-Fe CO32- LDH forms more favorable triple-phase boundary regions in the catalyst layer of the air electrode. The Ni-Fe CO32- LDH addition to the catalyst layer of the reversible air electrode using α-MnO2 also improves the performance of a rechargeable zinc-air battery. The reversible air electrode with α-MnO2 shows good cycle stability during 40 cycles, indicating that Ni-Fe LDH as an ionomer remains stable in the reversible air electrode after cycles. There must be a limited influence of CO2 on Ni-Fe CO32- LDH which can exist stably in air. Consequently, these results demonstrate that Ni-Fe CO3 2- LDHs are promising materials for use as multifunctional ionomers with high durability. They are widely applicable to rechargeable metal-air batteries using alkaline electrolytes. © 2013 The Royal Society of Chemistry.
  • Satoshi Urano, Rie Tomita, Kiyoharu Tadanaga
    JOURNAL OF POLYMER SCIENCE PART A-POLYMER CHEMISTRY 51 (3) 653 - 663 0887-624X 2013/02 [Refereed][Not invited]
     
    Poly(methylsilsesquioxane) (PMSQ) was synthesized using a two-step process consisting of hydrolysis of methyl trimethoxysilane (MTMS) with aluminum chelate catalyst and successive condensation reactions conducted at elevated temperatures. Results of nuclear magnetic resonance and Fourier transform infrared measurements show that all terminal functional groups were Si-OH in PMSQ. Results show further that PMSQ has both a cage structure and a network structure, and a cage/network ratio is represented by a height ratio of -64.5/-66.6 ppm. PMSQ of different molecular weight but the same Si-OH concentration is obtainable by varying the condensation reaction conditions such as the concentration, temperature, amount of aluminum chelate catalyst, and the solvent solubility parameter. A difference of the cage/network ratio occurs. A different cage/network ratio is dependent on the different reactivities of the intramolecular and intermolecular reactions. The relations of molecular structure of the obtained PMSQ molecular structure were characterized along with functions of storage stability, film hardness, and weather resistance. PMSQ designed with a larger cage/network ratio is necessary to obtain PMSQ with good storage stability and a coating film having good weather resistance. PMSQ designed with a smaller cage/network ratio should be prepared to obtain a coating film with high hardness. (C) 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 653-663
  • Kazushi Shimamoto, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Electrochimica Acta 109 651 - 655 0013-4686 2013 [Refereed][Not invited]
     
    MnO2/carbon nanotube (CNT) composite was prepared by a solution process. In the obtained MnO2-CNTcomposite, MnO2particles were well-dispersed on CNTs. The specific capacitance of the MnO2-CNT com-posite in an aqueous electrolyte was higher than that of MnO2and CNT. All-solid-state electrochemicalcapacitors (ECs) were fabricated using the MnO2-CNT composite as a positive electrode, activated carbonpowder as a negative electrode, and phosphosilicate gel as an electrolyte. The obtained all-solid-state ECsoperated at the temperature range between -30°C and 100°C. The specific discharge capacitance andthe rate ability of the capacitors were improved by elevating temperature. In addition, the fabricatedall-solid-state ECs exhibited excellent cycle performance at the temperature range between -30°C and100°C for 20,000 cycles. These results indicate that all-solid-state ECs using MnO2are promising energystorage devices with excellent stability and high reliability at the wide range of temperatures. © 2013 Elsevier Ltd. All rights reserved.
  • Daiju Kubo, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF POWER SOURCES 222 493 - 497 0378-7753 2013/01 [Refereed][Not invited]
     
    This paper reports on the application of hydroxide ion conducting layered double hydroxides (LDHs) to the catalyst layer in an alkaline fuel cell for the improvement of the oxygen reduction reaction (ORR) at the triple phase boundary (TPB) in the catalyst layer. Ni-Al LDH intercalated with CO32- (Ni-Al CO32- LDH) and Mg-Al CO32- LDH were used in this study. Ni-Al CO32- LDH showed higher ionic conductivity than Mg-Al CO32- LDH under R.H. of 80%. The catalyst layers with and without hydroxide ion conducting LDHs was prepared, and a half-cell using the prepared catalyst layers was fabricated. The addition of LDHs to the catalyst layer increased the reduction current for ORR, indicating that hydroxide ion conducting LDHs introduced OH- conducting paths and increased TPB region within the catalyst layer. Above all, the addition of Ni-Al CO32- LDH to the catalyst layer more effectively increased the reduction current for ORR than the addition of Mg-Al CO32- LDH. The performance of the alkaline-type direct ethanol fuel cell was also improved. These experimental results indicate that high hydroxide ion conducting Ni-Al CO32- LDH effectively increased TPB region within the catalyst layer. (C) 2012 Elsevier B.V. All rights reserved.
  • Hiroaki Ishida, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    Journal of Sol-Gel Science and Technology 65 (1) 41 - 45 0928-0707 2013/01 [Refereed][Not invited]
     
    Lithium silicate particles were prepared by the sol-gel process based on the Stöber method using tetraethoxysilane and lithium ethoxide as starting materials lithium dodecyl sulfate (LDS) was used as a surfactant. Lithium ion concentration of the obtained particles increased with an increase of Li/Si ratios from 1 to 4. Scanning electron microscope images showed that the obtained particles were rather monodispersed with diameter of 100-300 nm, and the particle size was not influenced by the amount of added LDS but the Li/Si ratios. Fourier-transform infrared spectra of the particles showed that the intensity of the peaks due to CO3 2- increased with an increase of the Li/Si ratios. X-ray diffraction patterns and 29Si magic-angle spinning-nuclear magnetic resonance spectra of the particles indicated that Q3 and Q2 units were present as amorphous state in the particles prepared with Li/Si ratios of 1 and 2, respectively. In the case of Li/Si ratios of more than 3, lithium metasilicate crystals formed, and Q1 and Q2 units were dominant. © 2012 Springer Science+Business Media, LLC.
  • Atsushi Sakuda, Naoyuki Nakamoto, Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of Materials Chemistry 22 (30) 15247 - 15254 1364-5501 2012/08/14 [Refereed][Not invited]
     
    LiCoO< inf> 2< /inf> particles were coated with cobalt and nickel sulfides by thermal decomposition of their respective diethyldithiocarbamato complexes. All-solid-state lithium secondary batteries were fabricated using the coated LiCoO< inf> 2< /inf> positive electrode and a Li< inf> 2< /inf> S-P< inf> 2< /inf> S < inf> 5< /inf> solid electrolyte. The coatings reduced the interfacial resistance between LiCoO< inf> 2< /inf> and the Li< inf> 2< /inf> S-P< inf> 2< /inf> S< inf> 5< /inf> solid electrolyte of the all-solid-state batteries after the first charge, resulting in an improved cell performance. The all-solid-state cell with NiS-coated LiCoO< inf> 2< /inf> was charged and discharged at a high rate of 10 C. The coatings reduced deterioration of the interface between LiCoO< inf> 2< /inf> and the Li< inf> 2< /inf> S-P< inf> 2< /inf> S< inf> 5< /inf> solid electrolyte, indicating that they function as an effective buffer layer at the interface. © The Royal Society of Chemistry 2012.
  • Atsuko Shinomiya, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    PHYSICS AND CHEMISTRY OF GLASSES-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART B 53 (3) 128 - 131 1753-3562 2012/06 [Refereed][Not invited]
     
    Glasses in the system Eu2O3-BaO-B2O3 were prepared by a mechanochemical process using B2O3, BaO, and Eu2O3 as starting materials. X-ray diffraction patterns indicate that amorphous 99.5(0.2BaO.0.8B2O3).0.5Eu(2)O(3) (mol%) powder was obtained using a planetary ball mill. From infrared and Raman spectra, the structural units observed in the milled glass with milling times longer than 5 h were the same as ones in the melt quenched glass. In photoluminescence measurements, the milled 99.5(0.2BaO.0.8B2O3).0.5Eu(2)O(3) glasses showed red emission due to Eu3+ ions. By heating the milled glass in air at temperatures higher than the crystallization temperature, 99.5(0.2BaO.0.8B2O3).0.5Eu(2)O(3) glass-ceramic was also prepared. The glass-ceramic showed broad emission in the range 380-450 nm from Eu2+ ions. Crystallization of the milled glass induced reduction of Eu3+ to Eu2+ in air.
  • Daiju Kubo, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF ELECTROANALYTICAL CHEMISTRY 671 102 - 105 1572-6657 2012/04 [Refereed][Not invited]
     
    Ionic conductivities of Ni/Al layered double hydroxides (Ni-Al LDHs) intercalated with CO32-, Cl- and OH- were evaluated in the temperature range of 25-80 degrees C under 65-95% relative humidity. X-ray diffraction and Fourier transform infrared measurements confirmed the formation of Ni-Al LDHs intercalated with CO32-, Cl- and OH-. In the AC conductivity measurements, Ni-Al LDH intercalated with CO32- (Ni-Al CO32- LDH) showed the highest ionic conductivity among them. The ionic conductivity of Ni-Al CO32- LDH was 1.3 x 10(-2) S cm(-1) at 80 degrees C under 80% relative humidity. The electromotive force for the water vapor concentration cell using Ni-Al CO32- LDH showed similar behavior with that using anion exchange membrane, indicating that Ni-Al CO32- LDH is a hydroxide ion conductor. Pelletized Ni-Al CO32- LDH was confirmed to work as the electrolyte of alkaline-type direct ethanol fuel cell. (C) 2012 Elsevier B.V. All rights reserved.
  • Kiyoharu Tadanaga, Akira Miyata, Daisuke Ando, Naoko Yamaguchi, Masahiro Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 62 (1) 111 - 116 0928-0707 2012/04 [Refereed][Not invited]
     
    Using hot water treatment of sol-gel derived precursor gel films, Co-Al and Ni-Al layered double hydroxide (LDH) thin films were prepared. The precursor gel films of Al2O3-CoO or Al2O3-NiO were prepared from cobalt or nickel nitrates and aluminum tri-sec-butoxide using the sol-gel method. Then, the precursor gel films were immersed in a NaOH aqueous solution of 100 A degrees C. Nanocrystallites of Co-Al and Ni-Al LDH were precipitated with the hot water treatment with NaOH solution. The largest amounts of nanocrystals were obtained with a solution of pH = 10 for Co-Al LDH, and with that of pH = 9 for Ni-Al LDH. X-ray diffraction measurements confirmed that this process formed CO3 (2-) intercalated LDHs. Both Co-Al and Ni-Al LDH thin films were confirmed to work as electrodes for electrochemical devices by cyclic voltammogram measurements.
  • Kiyoharu Tadanaga, Yoshihiro Furukawa, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 159 (4) B368 - B370 0013-4651 2012 [Refereed][Not invited]
     
    Mg-Al layered double hydroxides (LDHs) intercalated with carbonate anions were prepared by the co-precipitation process with Mg/Al = 2, 3 and 4, and the effect of Mg/Al ratio on the ionic conductivity was examined. It is shown that the Mg/Al ratio influences ionic conductivities of Mg-Al CO32- LDH. The conductivity of Mg-Al CO32- LDH with Mg/Al = 2 and 3 exhibited almost the same ionic conductivity of about 1 x 10(-3) S cm(-1) at room temperature under 80% relative humidity, while that of LDH with Mg/Al = 4 was lower by one order of magnitude. Thermal analyses showed that Mg-Al CO32- LDH with Mg/Al = 2 or 3 keeps interlayer water molecules at higher temperatures compared with Mg/Al = 4, suggesting that the interlayer water molecules are strongly held in the interlayer. The strongly held interlayer water molecules are assumed to contribute the high ionic conductivity in Mg-Al CO32- LDH with Mg/Al = 2 and 3. The alkaline type direct ethanol fuel cells using Mg/Al CO32- LDHs as hydroxide conducting electrolyte were confirmed to operate, and larger power was obtained in Mg-Al CO32- LDH with smaller Mg/Al ratio. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.007204jes] All rights reserved.
  • Kiyoharu Tadanaga
    2ND ASEAN - APCTP WORKSHOP ON ADVANCED MATERIALS SCIENCE AND NANOTECHNOLOGY (AMSN 2010) 1455 29 - 32 0094-243X 2012 [Refereed][Not invited]
     
    Inorganic materials with high ionic conductivity must have big advantages for the thermal and long term stability when the materials are used as the electrolyte of fuel cells. In the present paper, novel ionic conductive inorganic materials for polymer electrolyte fuel cells (PEFCs) and all solid state alkaline fuel cells (AFCs) that have been developed by our group have been reviewed. PEFCs which can operate in temperature range from 100 to 200 degrees C are intensively studied because of some advantages such as reduction of CO poisoning of Pt catalyst and acceleration of electrode reactions. We showed that the fuel cells using the composite membranes prepared from phosphosilicate gel powder and polyimide precursor can operate in the temperature range from 30 to 180 degrees C. We also found that the inorganic-organic hybrid membranes with acid-base pairs from 3-aminopropyltriethoxysilane and H2SO4 or H3PO4 show high proton conductivity under dry atmosphere, and the membranes are thermally stable at intermediate temperatures. On the other hand, because the use of noble platinum is the serious problem for the commercialization of PEFCs and because oxidation reactions are usually faster than those of acid-type fuel cells, alkaline type fuel cells, in which a non-platinum catalyst can be used, are attractive. Recently, we have proposed an alkaline-type direct ethanol fuel cell (DEFC) using a natural clay electrolyte with non-platinum catalysts. So-called hydrotalcite clay, Mg-Al layered double hydroxide intercalated with CO32-(Mg-Al CO32- LDH), has been proved to be a hydroxide ion conductor. An alkaline-type DEFC using Mg-Al CO32-LDH as the electrolyte and aqueous solution of ethanol and potassium hydroxide as a source of fuel exhibited excellent electrochemical performance.
  • 忠永 清治, 辰巳砂 昌弘
    電気化学および工業物理化学 : denki kagaku The Electrochemical Society of Japan 79 (8) 630 - 633 1344-3542 2011/08/05
  • Akitoshi Hayashi, Hideki Morishima, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Solid State Ionics 192 (1) 126 - 129 0167-2738 2011/06/16 [Refereed][Not invited]
     
    Glassy solid electrolytes were prepared by combining the 50Li 2SO4•50Li3BO3 (mol%) ionic glass and the 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([EMI]BF 4) ionic liquid. High-energy ball milling was carried out for the mixture of the inorganic ionic glass and the organic ionic liquid. The ambient temperature conductivity of the glass electrolyte with 10 mol% [EMI]BF 4 was 10-4 S cm-1, which was three orders of magnitude higher than that of the 50Li2SO4•50Li 3BO3 glass. The addition of [EMI]BF4 to the ionic glass decreased glass transition temperature (Tg) of the glass and the decrease of Tg is closely related to the enhancement of conductivity of the glass. Morphology and local structure of the glass electrolyte was characterized. The dissolution of an ionic liquid in an ionic glass with Li+ ion conductivity is a novel way to developing glass electrolytes for all-solid-state lithium secondary batteries. © 2010 Elsevier B.V. All rights reserved.
  • Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Solid State Ionics 192 (1) 304 - 307 0167-2738 2011/06/16 [Refereed][Not invited]
     
    To improve the electrochemical performance of an all-solid-state In/80Li2S2·0P2S5 (electrolyte)/LiMn 2O4 cell, a lithium-titanate thin film was used to coat LiMn2O4. The interfacial resistance between LiMn 2O4 and the electrolyte (measured after initial charging) decreased when the LiMn2O4 particles were coated with lithium-titanate. A cell with lithium-titanate-coated LiMn2O 4 had a higher capacity than a cell with noncoated LiMn 2O4 for current densities in the range 0.064 to 2.6 mA cm- 2. Additionally, a cell with coated LiMn2O4 retained 96% of the 10th-cycle reversible capacity at a current density of 0.064 mA cm- 2 after 50 cycles. © 2010 Elsevier B.V. All rights reserved.
  • Yoshihiro Furukawa, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    SOLID STATE IONICS 192 (1) 185 - 187 0167-2738 2011/06 [Refereed][Not invited]
     
    This study demonstrates that humidity, temperature, and the interlayer anions influence ionic conductivities of Mg-Al layered double hydroxides (LDHs) intercalated with inorganic anions. Results show that Mg-Al LDH intercalated with Br(-) exhibited the highest ionic conductivity among Mg-Al LDHs intercalated with CO(3)(2-), Cl(-), Br(-), NO(3)(-) and SO(4)(2-). Its ionic conductivity was 1.1 x 10(-2) S cm(-1) at 80 degrees C under 80% relative humidity. The electromotive force for the hydroxide ion concentration cell using Mg-Al CO(3)(2-) LDH showed the same behavior with that using an anion exchange membrane, indicating that Mg-Al CO(3)(2-) LDH can be a hydroxide ion conductor. (C) 2010 Elsevier B.V. All rights reserved.
  • Kenji Takahashi, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 119 (1387) 173 - 179 1882-0743 2011/03 [Refereed][Not invited]
     
    Polyorganosilsesquioxanes (RSiO3/2) (R: organic group) particles with different organic groups such as alkyl and aryl groups were prepared using a two-step acid-base catalyzed sol-gel process. Spherical particles were formed at room temperature using the two-step acid-base catalyzed sol-gel process in which trifunctional organoalkoxysilanes with R = methyl, n-propyl, n-butyl, phenyl, and benzyl were used as starting materials. Polyorganosilsesquioxanes with longer alkyl groups or phenethyl group prepared by the two-step acid-base catalyzed sol-gel process were oily material at room temperature. Polyorganosilsesquioxanes with shorter alkyl or aryl groups exhibited the glass transition. In contrast, polyorganosilsesquioxanes with longer alkyl groups showed no glass transition behavior. The occurrence of glass transition phenomena of polyorganosilsesquioxanes was concluded to be strongly dependent on the chain length of organic substituents. (C) 2011 The Ceramic Society of Japan. All rights reserved.
  • George Hasegawa, Mami Aoki, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada, Kiyoharu Tadanaga
    JOURNAL OF MATERIALS CHEMISTRY 21 (7) 2060 - 2063 0959-9428 2011 [Refereed][Not invited]
     
    Macro/meso/microporous carbon monoliths doped with sulfur have been prepared from sulfonated poly(divinylbenzene) networks followed by the activation with CO2 resulted in the activated carbon monoliths with high surface area of 2400 m(2) g(-1). The monolithic electrode of the activated carbon shows remarkably high specific capacitance (175 F g(-1) at 5 mV s(-1) and 206 F g(-1) at 0.5 A g(-1)).
  • George Hasegawa, Mami Aoki, Kazuyoshi Kanamori, Kazuki Nakanishi, Teiichi Hanada, Kiyoharu Tadanaga
    Materials Research Society Symposium Proceedings 1304 38 - 43 0272-9172 2011 [Not refereed][Not invited]
     
    Macro/meso/microporous carbon monoliths doped with sulfur have been prepared from sulfonated polydivinylbenzene networks followed by the activation with CO 2 resulted in the activated carbon monoliths with high surface area of 2400 m 2 g -1. The monolithic electrode of the activated carbon shows remarkably high specific capacitance (175 F g -1 at 5 mV s -1 and 206 F g -1 at 0.5 A g -1). © 2011 Materials Research Society.
  • Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Electrochimica Acta 55 (28) 8821 - 8828 0013-4686 2010/12/01 [Refereed][Not invited]
     
    LiNi1/3Co1/3Mn1/3O2 was applied as a promising material to the all-solid-state lithium cells using the 80Li2S·19P2S5·1P 2O5 (mol%) solid electrolyte. The cell showed the first discharge capacity of 115 mAh g-1 at the current density of 0.064 mA cm-2 and retained the reversible capacity of 110 mAh g-1 after 10 cycles. The interfacial resistance was observed in the impedance spectrum of the all-solid-state cell charged to 4.4 V (vs. Li) and the transition metal elements were detected on the solid electrolyte in the vicinity of LiNi1/3Co1/3Mn1/3O2 by the TEM observations with EDX analyses. The electrochemical performance was improved by the coating of LiNi1/3Co1/3Mn1/3O2 particles with Li4Ti5O12 film. The interfacial resistance was decreased and the discharge capacity was increased from 63 to 83 mAh g-1 at 1.3 mA cm-2 by the coating. The electrochemical performance of LiNi1/3Co1/3Mn1/3O2 was compared with that of LiCoO2, LiMn2O4 and LiNiO2 in the all-solid-state cells. The rate capability of LiNi 1/3Co1/3Mn1/3O2 was lower than that of LiCoO2. However, the reversible capacity of LiNi 1/3Co1/3Mn1/3O2 at 0.064 mA cm -2 was larger than that of LiCoO2, LiMn2O 4 and LiNiO2. © 2010 Elsevier Ltd All rights reserved.
  • Yusuke Uraoka, Kiyoharu Tadanaga, Masahiro Tatsumisago
    CHEMISTRY OF MATERIALS 22 (22) 6125 - 6129 0897-4756 2010/11 [Refereed][Not invited]
     
    Porous methylsilsesquioxane thin films were prepared using the sol gel process, with tris(ethylenediamine)cobalt(III) chloride (Co(en)(3)Cl(3)) as a photobase generator and polypropylene glycol (PPG) as a template. The generation of amines was confirmed for more than 2 min of ultraviolet (UV) irradiation. The prepared film with the UV irradiation and subsequent heat treatment showed a low refractive index of n = 1.35. Subsequent field-emission scanning electron microscopy (FE-SEM) observations confirmed that shrinkage of the film with the heat treatment was suppressed in the film with UV irradiation. The photogenerated amines from Co(en)(3)Cl(3) worked as a catalyst for the condensation reaction in the gel films during the initial stage of heat treatment. A porous structure was obtained using the thermal decomposition of PPG without collapse of the gel network.
  • Kiyoharu Tadanaga, Yoshihiro Furukawa, Akitoshi Hayashi, Masahiro Tatsumisago
    ADVANCED MATERIALS 22 (39) 4401 - + 0935-9648 2010/10 [Refereed][Not invited]
     
    An alkaline-type direct ethanol fuel cell (DEFC) using a natural clay electrolyte with nonplatinum catalysts is proposed. So-called hydrotalcite clay, Mg-Al layered double hydroxide intercalated with CO(3)(2-), is shown to be a hydroxide ion conductor. An alkaline-type DEFC using this natural clay as the electrolyte and aqueous solution of ethanol and potassium hydroxide as a source of fuel exhibits excellent electrochemical performance from room temperature to 80 degrees C.
  • Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of Materials Research 25 (8) 1548 - 1553 0884-2914 2010/08 [Refereed][Not invited]
     
    All-solid-state Li-In/Li4Ti5O12 cells using Li2S-P2S5 solid electrolytes were assembled to investigate their electrochemical properties in the wide voltage range of 0-3 V (versus Li). The Li/Li4Ti5O12 cells using 1 M LiPF6 in ethylene carbonate and diethyl carbonate were fabricated for comparison with the all-solid-state cells. The capacity of the all-solid-state cell using the 70Li2S·27P 2S5·3P2O5 (mol%) solid electrolyte decreased with an increase in the current density as well as the cell using the liquid electrolyte. However, the allsolid-state cell was charged and discharged even at a high current density of 10 m A/cm2. The all-solid-state cell was cycled at 1.3 mA/cm2 and retained 90% of the first reversible capacity of about 120 mAh/g after 500 cycles. The all-solid-state cell cycling at 100 °C showed the small overpotential and reversible capacity of about 120 mAh/g at 13 mA/cm2. © 2010 Materials Research Society.
  • T. Sugahara, A. Hayashi, K. Tadanaga, M. Tatsumisago
    SOLID STATE IONICS 181 (3-4) 190 - 192 0167-2738 2010/02 [Refereed][Not invited]
     
    Proton conducting ionic glasses which consist of only isolated ions were successfully prepared from only CsHSO4 and the mixture of CsHSO4 and CsH2PO4 by melt-quenching technique. The 50CsHSO(4)center dot 50CsH(2)PO(4) glass showed the conductivity of 4.2 x 10(-6)S cm(-1) at room temperature. The 50CsHSO(4)center dot 50CsH(2)PO(4) glass exhibited much higher ionic conductivity than CsHSO4 and Cs-2(HSO4)(H2PO4) crystals in a relatively wide temperature range of ambient to 90 degrees C under dry Ar atmosphere, indicating that vitrification of CsHSO4-based solid acids is effective in enhancing their conductivity. (C) 2009 Elsevier B.V. All rights reserved.
  • Kiyoharu Tadanaga, Yoshinobu Yamashita, Akitoshi Hayashi, Masahiro Tatsumisago
    SOLID STATE IONICS 181 (3-4) 187 - 189 0167-2738 2010/02 [Refereed][Not invited]
     
    Glass formation in the systems CsHSO4-MHSO4 (M = Na, K, and Rb) was examined by the melt quenching technique using a twin roller, and thermal and ionic conducting properties of the glasses were investigated. To avoid the dehydration reaction, the melts were quenched immediately after the confirmation of complete melting. In the CsHSO4-NaHSO4 system, glasses were obtained at the composition of x = 50, 60 and 70 in xCsHSO(4) (100 - x)NaHSO4 (mol%). However, vitrification was not observed in the CsHSO4-KHSO4 and CsHSO4-RbHSO4 systems. The FT-IR spectra of the glasses obtained by the quenching of molten CsHSO4 and NaHSO4 showed that these glasses consist of isolated HSO4- units, and the glasses were confirmed to be "ionic glass" which consist of only isolated ionic species. From the DSC measurements, the 70CsHSO(4)center dot 30NaHSO(4) ionic glass was found to have the glass transition temperature of 17 degrees C, and crystallization temperature of 58 degrees C. The ionic conductivity of the 70CsHSO(4)center dot 30NaHSO(4) glass is in the order of 10(-5) S cm(-1) at room temperature, which is higher than that of CsHSO4 low-temperature phase. After heating above the crystallization temperature, the ionic conductivity rapidly decreased. These results suggest that vitrified solid acids have advantages in proton conduction compared with the low-temperature phase of solid acids. (C) 2009 Elsevier B.V. All rights reserved.
  • J. Macan, K. Tadanaga, M. Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 53 (1) 31 - 37 0928-0707 2010/01 [Refereed][Not invited]
     
    Alkyl-modified phenylsilsesquioxane (PhSSQ) particles were prepared from phenyltriethoxysilane by two-step acid-base catalysed sol-gel process, using alkyltriethoxysilanes of varying chain length (methyl, ethyl, pentyl and octyl), in order to control the softening temperature and thermal stability of the resulting particles. Resulting particles were characterized by scanning electron microscopy, X-ray diffraction analysis, gel permeation chromatography and Fourier-transform infrared spectroscopy, while the thermal properties were investigated by differential scanning calorimetry and thermogravimetric analysis. Increased chain length presents steric hindrance to condensation of phenyltriethoxysilane, leading to decreased softening temperature and thermal stability, while copolymerization with methyltrialkoxysilane leads to increase of softening temperature without influencing the thermal stability. Copolymerization with alkyltrialkoxysilanes is therefore a feasible method to control the softening temperature of PhSSQ particles. By their properties the modified PhSSQ could be grouped in short-chain modified (methyl and ethyl) and long-chain modified (pentyl and octyl) ones.
  • M. Aoki, K. Tadanaga, M. Tatsumisago
    ELECTROCHEMICAL AND SOLID STATE LETTERS 13 (4) A52 - A54 1099-0062 2010 [Refereed][Not invited]
     
    An all-solid-state electric double-layer capacitor was fabricated with an inorganic-organic hybrid membrane from 3-glycidoxypropyltrimethoxysilane, tetraethoxysilane, and orthophosphoric acid as an electrolyte, and activated carbon fiber cloth as polarized electrodes. The electrochemical properties of the capacitor were studied in a temperature range from room temperature to 100 degrees C. The specific capacitance of the capacitor was 41 F/g at 100 degrees C with 12% relative humidity, and the capacitor showed good cycle performance. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3305323] All rights reserved.
  • Hirokazu Kitaura, Kenji Takahashi, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of the Ceramic Society of Japan 118 (1376) 326 - 328 1348-6535 2010 [Refereed][Not invited]
     
    Needle-like α-Fe2O3 particles with the length of 2 μm and the width of 250nm were prepared by thermal decomposition of β-FeOOH and the electrochemical performances in the all-solid-state cells were examined. The cell using needle-like particles with acetylene black as a conductive additive showed the first discharge capacity of about 700 mAhg -1 at the current density of 0.064mA cm-2. The lithium ion and electron conduction path of the electrode was improved by using vapor grown carbon fiber as a conductive additive. The needle-like α-Fe 2O3 particles were compared with α-Fe 2O3 spherical particles the suitability for the active material of all-solid-state batteries was investigated. ©2010 The Ceramic Society of Japan. All rights reserved.
  • Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of the Electrochemical Society 157 (4) A407 - A411 0013-4651 2010 [Refereed][Not invited]
     
    All-solid-state In/ LiMn2 O4 cells with the 80 Li2 S20 P2 S5 (mol %) solid electrolyte were assembled. Cycle and rate performances were evaluated. The cell showed the first discharge capacity of 55 mAh g-1 at a current density of 0.064 mA cm-2 and retained the reversible capacity of 47 mAh g-1 after 100 cycles. The capacity decreased with increase in the current density, and the overpotential at the beginning of discharge was observed. The discharge capacity was about 23 mAh g-1 at a current density of 2.6 mA cm -2. To identify the cause of the overpotential, impedance measurements were carried out, and resistance components were analyzed by changing the state of charge and by evaluating an all-solid-state Li 1-x Mn2 O4 symmetric cell. The interfacial resistance between the LiMn2 O4 electrode and the solid electrolyte was identified after the charge process. The transmission electron microscopy observation and energy-dispersive X-ray analysis, showed that Mn slightly diffused from LiMn2 O4 to the solid electrolyte at the interface. © 2010 The Electrochemical Society.
  • Kiyoharu Tadanaga, Naoko Yamaguchi, Masahiro Tatsumisago
    RESEARCH ON CHEMICAL INTERMEDIATES 35 (8-9) 949 - 956 0922-6168 2009/11 [Refereed][Not invited]
     
    We prepared Zn-Al layered double hydroxide (LDH) thin films intercalated with sulfonated 1,3',3'-trimethyl-6-nitrospiro[2H-chromene-2,2'-indoline] anions (SP-SO(3) (-)) by immersion of sol-gel derived amorphous Al(2)O(3)-ZnO thin films in hot water containing SP-SO(3)H. Extended interlayer spacing, in comparison to the Zn-Al LDH with carbonate anions, was observed after immersion in distilled water containing SP-SO(3)H at 60 A degrees C for 30 min, indicating that we formed Zn-Al LDH films with SP-SO(3) (-) directly on glass substrates. The merocyanine form of SP-SO(3) (-) was shown by UV spectra to have stabilized in the hydroxide layers of LDH.
  • Akitoshi Hayashi, Hideyuki Morimoto, Miyuki Nakai, Kiyoharu Tadanaga, Masahiro Tatsumisago
    GLASS TECHNOLOGY-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART A 50 (5) 273 - 276 1753-3546 2009/10 [Refereed][Not invited]
     
    Glasses in the system SnO-B2O3-V2O5 were prepared using a planetary ball mill apparatus. Amorphous 45SnO(center dot)45B(2)O(3 center dot)10V(2)O(5) (mol%) powder was obtained by ball milling 50 h at a rotation speed of 370 rpm. The glass transition was observed at about 440 degrees C by differential thermal analysis. Electrochemical cells using a conventional liquid electrolyte (1 M LiPF6 in EC-DEC) were assembled. The cell With the 45SnO(center dot)45B(2)O(3 center dot)10V(2)O(5) glass as a working electrode exhibited an initial capacity of 610 mAh g(-1), which was smaller than the capacity of the cell using a 50SnO(center dot)50B(2)O(3) electrode (710 mAh g(-1)). Oil the other hand, the glass With V2O5 retained a larger capacity of 330 mAh g(-1) than the glass without V2O5 (180 mAh g(-1)) after 20 cycles. The addition Of V2O5 played an important role in enhancing the cycle performance of cells using SnO-based glass electrodes.
  • Per Martin Rorvik, Kiyoharu Tadanaga, Masahiro Tatsumisago, Tor Grande, Mari-Ann Einarsrud
    JOURNAL OF THE EUROPEAN CERAMIC SOCIETY 29 (12) 2575 - 2579 0955-2219 2009/09 [Refereed][Not invited]
     
    Nanotubes of ferroelectric lead titanate (PbTiO3) have been made by a template-assisted method. An equimolar Pb-Ti sol was dropped onto porous alumina membranes and penetrated into the channels of the template. Single-phase PbTiO3 perovskite nanotubes were obtained by annealing at 700 degrees C for 6 h. The nanotubes had diameters of 200-400 nm with a wall thickness of approximately 20 nm. Excess PbO or annealing in a Pb-containing atmosphere was not necessary in order to achieve single-phase PbTiO3 nanotubes. The influence of the heating procedure and the sol concentration is discussed. (C) 2009 Elsevier Ltd. All rights reserved.
  • Akitoshi Hayashi, Daisuke Furusawa, Keiichi Minami, Kiyoharu Tadanaga, Masahiro Tatsumisago
    GLASS TECHNOLOGY-EUROPEAN JOURNAL OF GLASS SCIENCE AND TECHNOLOGY PART A 50 (4) 217 - 220 1753-3546 2009/08 [Refereed][Not invited]
     
    A new type of solid electrolyte was mechanochemically prepared from lithium pyroborate glass as a Li+ ion conductor, and 1-ethyl-3-methyl-imidazolium tetrafluoroborate ([EMI]BF4) as an ionic liquid. It was revealed from FT-IR and B-11 MAS-NMR measurements that [EMI](+) cations and BF4- anions were not decomposed by high energy ball milling, and were still present in the prepared (100-x)(0.67Li(2)O center dot 0.33B(2)O(3))center dot x[EMI]BF4 (mol%) glasses. DSC analysis suggests that glass transition temperatures were decreased by the addition of [EMI]BF4 to the lithium borate glass. The ambient temperature conductivity of the glass containing 10 mol%, [EMI]BF4 was 10(-4) S cm(-1), Which isoform orders of magnitude higher than that of 67Li(2)O.33B(2)O(3) (mol%) glass, The activation energy for conduction was decreased by the addition of [EMI]BF4. The dissolution of ail ionic liquid in glass is a novel Way to enhance the conductivity of glass electrolytes.
  • Akitoshi Hayashi, Daisuke Furusawa, Keiichi Minami, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Glass Technology: European Journal of Glass Science and Technology Part A 50 217 - 220 0017-1050 2009/08/01 [Not refereed][Not invited]
     
    A new type of solid electrolyte was mechanochemically prepared from lithium pyroborate glass as a Li+ ion conductor, and l-ethyl-3-methyl- imidazolium tetrafluoroborate ([EMI]BF4) as an ionic liquid. It was revealed from FT-IR and 11B MAS-NMR measurements that [EMI] + cations and BF4- anions were not decomposed by high energy ball milling, and were still present in the prepared (100-x)(0-67Li2O.0-33B2O3).\[EMI]BF4, (mol%) glasses. DSC analysis suggests that glass transition temperatures were decreased by the addition Of [EMI]BF4 to the lithium borate glass. The ambient temperature conductivity of the glass containing 10 mol% [EMI]BF4 was 10-4 S cm'1, which is four orders of magnitude higher than that of 67Li2O.33B2O3 (mol%) glass. The activation energy for conduction was decreased by the addition Of [EMI]BF4. The dissolution of an ionic liquid in glass is a novel way to enhance the conductivity of glass electrolytes.
  • Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of Power Sources 189 (1) 145 - 148 0378-7753 2009/04/01 [Refereed][Not invited]
     
    The all-solid-state Li-In/Li4Ti5O12 cell using the 80Li2S·20P2S5 (mol%) solid electrolyte was assembled to investigate rate performances. It was difficult to obtain the stable performance at the charge current density of 3.8 mA cm-2 in the all-solid-state cell. In order to improve the rate performance, the pulverized Li4Ti5O12 particles were applied to the all-solid-state cell, which retained the reversible capacity of about 90 mAh g-1 at 3.8 mA cm-2. The 70Li2S·27P2S5·3P2O5 glass-ceramic, which exhibits the higher lithium ion conductivity than the 80Li2S·20P2S5 solid electrolyte, was also used. The Li-In/70Li2S·27P2S5·3P2O5 glass-ceramic/pulverized Li4Ti5O12 cell was charged at a current density higher than 3.8 mA cm-2 and showed the reversible capacity of about 30 mAh g-1 even at 10 mA cm-2 at room temperature. © 2008 Elsevier B.V. All rights reserved.
  • Atsushi Sakuda, Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of Power Sources 189 (1) 527 - 530 0378-7753 2009/04/01 [Refereed][Not invited]
     
    All-solid-state lithium secondary batteries using LiCoO2 active materials coated with Li2SiO3 and SiO2 oxide films and Li2S-P2S5 solid electrolytes were fabricated and their electrochemical performance was investigated. The electrochemical performace of the all-solid-state cells at a high voltage region was highly improved by using oxide-coated LiCoO2. The oxide coatings are effective in suppressing the formation of an interfacial resistance between LiCoO2 and the solid electrolyte at a high cutoff voltage of 4.6 V (vs. Li). As a result, charge-discharge capacities and cycle performance at the cutoff voltage were improved. The cell with Li2SiO3-coated LiCoO2 showed a large initial discharge capacity of 130 mAh g-1 and a good capacity retention of 110 mAh g-1 after 50th cycles at the cutoff voltage of 4.6 V (vs. Li). © 2008 Elsevier B.V. All rights reserved.
  • Teruaki Tezuka, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 156 (1) B174 - B177 0013-4651 2009 [Refereed][Not invited]
     
    Proton conductive inorganic-organic hybrid membranes were prepared from 3-(2-aminoethylaminopropyl)triethoxysilane (AEAPTES) and H(2)SO(4) by the sol-gel method. Differential thermal analysis-thermogravimetry measurements revealed that the resulting membranes were thermally stable up to 300 degrees C. From the IR spectra, formation of acid-base pairs by protonation of the amino groups with H(2)SO(4) was confirmed. X-ray diffraction patterns of the membranes showed diffraction peaks corresponding to d-spacings of hexagonal structure, probably indicating that stacking of rodlike polysiloxanes with the acid-base pairs extruded outside. The conductivity of the membrane with the molar ratio of H(2)SO(4)/AEAPTES=2.0 was 1x10(-3) S cm(-1) at 150 degrees C under dry Ar atmosphere.
  • Atsushi Sakuda, Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of the Electrochemical Society 156 (1) A27 - A32 0013-4651 2009 [Refereed][Not invited]
     
    Effects of modification of the electrode/electrolyte interface with Li 2O-SiO2 thin films on impedance profiles and rate capabilities of all-solid-state In80 Li2S20 P2S 5 glass ceramic/ LiCoO2 cells were investigated. Large resistance was observed at the LiCoO2 -electrode/sulfide-electrolyte interface in all-solid-state cells. The interfacial resistance was decreased by 0.06 wt % oxide coatings on LiCo O2 the effective coatings were a lithium-ion conductive Li2Si O3 glassy film and an insulative SiO 2 film. The Li2Si O3 coating film decreased the interfacial resistance more effectively when the coating amounts increased from 0.06 to 0.6 wt % (film thickness was ca. 10 nm). However, 0.6 wt % of SiO 2 coating exhibited higher interfacial resistance than noncoating because the thick SiO2 coating film acted as a high-resistance layer. Temperature dependence of the interfacial resistance suggests that the resistance decrease was achieved mainly by an increase of pre-exponential factor rather than by a decrease of activation energy for ion conduction at the interface. At room temperature, all-solid-state cells with Li2Si O3 -coated LiCoO2 were discharged even under the high current density, 6.4 mA cm-2. © 2008 The Electrochemical Society.
  • Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of the Electrochemical Society 156 (2) A114 - A119 0013-4651 2009 [Refereed][Not invited]
     
    All-solid-state Li-In Li4 Ti5 O12 cells using the 80 Li2 S20 P2 S5 solid electrolyte were assembled to investigate their rate performances and impedance behaviors. Furthermore, Li Li4 Ti5 O12 cells using 1 mol dm-3 LiP F6 dissolved in ethylene carbonate and diethyl carbonate were fabricated for comparison to the all-solid-state cells. In the all-solid-state cells, resistance attributable to the lithium-ion transfer from the solid electrolyte to Li4 Ti5 O12 spinel phase was observed during the lithium insertion into Li4 Ti5 O12 spinel phase during the discharge process. Results clarified that the cells using the solid electrolyte showed higher resistance and larger activation energy for this lithium-ion transfer than the cells using the liquid electrolyte. Resistance was not observed in the charge process. The all-solid-state cell showed the average charge voltage of 1.9 V (vs Li) and reversible capacity of ∼80 mAh g-1 at the charge current density of 1.3 mA cm-2 and the discharge current density of 0.064 mA cm-2. © 2008 The Electrochemical Society.
  • Kiyoharu Tadanaga, Yoshiki Michiwaki, Teruaki Tezuka, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF MEMBRANE SCIENCE 324 (1-2) 188 - 191 0376-7388 2008/10 [Not refereed][Not invited]
     
    Proton-conductive composite membranes were prepared from phosphosilicate gel powders and a commercially available polyimide precursor. The conductivity of a composite membrane containing 75 wt.% of gel powder was about 2.5 x 10(-3) S cm(-1) at 180 degrees C under more than 0.4%RH. However, under dry N(2) atmosphere at 180 degrees C, the conductivity decreased with time because of the formation of Si(5)O(PO(4))(6) crystals. The open circuit voltage (OCV) of a fuel cell in which the phosphosilicate gel-polyimide composite sheet was used as electrolyte and Pt-loaded carbon paper sheets were used as electrodes in the membrane electrode assembly. was about 0.85 V at 80 degrees C with a flow of hydrogen and air, and the OCV decreased to about 0.70 V at temperatures higher than 100 degrees C. At 180 degrees C under 2%RH, the cell OCV was 0.67 V; power density of about 14 mW cm(-2) was obtained with current density of 40 mA cm(-2). Consequently, the fuel cell using the composite sheet as an electrolyte was verified to operate at temperatures from room temperature to 180 degrees C. (C) 2008 Elsevier B.V. All rights reserved.
  • Teruaki Tezuka, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    SOLID STATE IONICS 179 (21-26) 1151 - 1154 0167-2738 2008/09 [Not refereed][Not invited]
     
    Proton conductive inorganic-organic hybrid membranes with acid-base pairs have been prepared from 3-aminopropyltriethoxysilane and phosphoric acid by the sol-gel method. The self-standing membranes obtained are represented as poly(3-aminopropylsilsesquioxane)-H(3)PO(4) (PAPS-H(3)PO(4)) membranes. Infrared absorption spectra of the PAPS-H(3)PO(4) films showed that amino groups of PAPS were protonated by phosphoric acid, indicating the formation of acid-base pairs. X-ray diffraction patterns of the PAPS-H(3)PO(4) membranes showed diffraction peaks attributed to hexagonal structure, which is probably formed by stacking of rodlike polysiloxane with the acid-base pairs extruded outside. The conductivities of the PAPS-H(3)PO(4) membranes with a molar ratio Of H(3)PO(4)/APTES = 1.0 was 4 x 10(-4) S cm(-1) at 150 degrees C under dry condition. (c) 2008 Elsevier B.V. All rights reserved.
  • Hirokazu Kitaura, Kenji Takahashi, Fuminori Mizuno, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    JOURNAL OF POWER SOURCES 183 (1) 418 - 421 0378-7753 2008/08 [Not refereed][Not invited]
     
    alpha-Fe2O3 fine particles have been prepared by a mechanochemical process and a solution process. alpha-Fe2O3 nanoparticles with aggregates composed of the several tens nm primary particles were produced by the mechanochemical process. The nanoparticles were applied to the electrode as an active material for all-solid-state lithium batteries and the electrochemical properties of the cell were investigated. Typical charge-discharge curves, as seen in the liquid type cell using the alpha-Fe2O3 nanoparticles as an electrode were observed in the all-solid-state cell. The first discharge capacity of the cell of about 780 mAh g(-1) was, however, smaller than the capacity of a cell using alpha-Fe2O3 particles prepared by the solution process, which were monodispersed particles of 250 nm without aggregates. In order to develop electrochemical performance of all-solid-state batteries, it is important to use the electrode particles without aggregation which lead to the formation of good solid-solid interface between active material and solid electrolyte particles. (C) 2008 Elsevier B.V. All rights reserved.
  • M. A. Aegerter, R. Almeida, A. Soutar, K. Tadanaga, H. Yang, T. Watanabe
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 47 (2) 203 - 205 0928-0707 2008/08 [Not refereed][Not invited]
  • Kiyoharu Tadanaga, Naoko Yamaguchi, Yusuke Uraoka, Atsunori Matsuda, Tsutomu Minami, Masahiro Tatsumisago
    THIN SOLID FILMS 516 (14) 4526 - 4529 0040-6090 2008/05 [Not refereed][Not invited]
     
    Alumina gel films were coated on poly(methyl methacrylate) (PMMA) substrates using the sol-gel process, and pseudo-boehmite nanocrystals of several tens of nanometers were precipitated on the surface of the alumina gel films through immersion in hot water. It was found that the PMMA substrates, which were coated with the pseudo-boehmite nanocrystals precipitated alumina, exhibited very slight incident-angle dependence in transmittance up to 60 degrees. The reflectance of PMMA substrates coated with the nanocrystal-precipitated alumina was less than 0.8% in the visible light region. (C) 2007 Elsevier B.V. All rights reserved.
  • Atsunori Matsuda, Kumpei Kobayashi, Toshihiro Kogure, Mototsugu Sakai, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    JOURNAL OF NON-CRYSTALLINE SOLIDS 354 (12-13) 1263 - 1266 0022-3093 2008/02 [Not refereed][Not invited]
     
    The shape of the precipitates on sol-gel derived SiO2-TiO2 coatings at the negative electrode changed from granular to ramiform, by applying an electric field to the substrates during a hot water treatment, whereas such changes in the shape of titania nanocrystals with the electric field were not observed at the positive electrode. The granular and ramiform. precipitates were identified as anatase (TiO2) and hydrated titania (n(TiO2) center dot mH(2)O), respectively. The ramiform shape of the titania, precipitates became significant with increasing the applied voltage, while the coatings gradually became dark-colored due to the reduction of Ti4+ to Ti3+. The coatings with ramiform precipitates showed an excellent wettability for water. (c) 2007 Published by Elsevier B.V.
  • Atsushi Sakuda, Hirokazu Kitaura, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    ELECTROCHEMICAL AND SOLID STATE LETTERS 11 (1) A1 - A3 1099-0062 2008 [Not refereed][Not invited]
     
    Development of rate capability is one of the most important issues to be solved in all-solid-state lithium secondary batteries. The electrochemical performance of these batteries has been highly improved by coating LiCoO2 particles with Li2O-SiO2 thin film. The interfacial resistance between LiCoO2 and the glass-ceramic electrolyte was decreased by those coatings. The rate capabilities of the cells using the coated LiCoO2 particles were superior to that of the cell using noncoated LiCoO2. The Li2SiO3 coating was more effective than the SiO2 coating in enhancing rate performance, suggesting that lithium-ion conductivity of the coating materials is important for high-rate performance. (C) 2007 The Electrochemical Society.
  • Takanori Konishi, Akitoshi Hayashi, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    JOURNAL OF NON-CRYSTALLINE SOLIDS 354 (2-9) 380 - 385 0022-3093 2008/01 [Not refereed][Not invited]
     
    Using melt quenching, SnO-P2O5 glasses were synthesized, and then characterized as negative electrode materials for lithium secondary batteries. The electrochemical cell Li/the 67SnO center dot 33P(2)O(5) (mol%) glass maintained reversible capacity of about 400 mAh g(-1) for 20 cycles. The cell's cycle performance was better than those of cells using Sn-based crystals such as Sn, SnO, and SnO2 as working electrodes. The local structure of the 67SnO center dot 33P(2)O(5) glass after lithium insertion and extraction was analyzed. Li-7 MAS-NMR measurements revealed that the Li-Sn alloy was formed during the first lithium insertion to the glass and that alloying-dealloying of the Li-Sn domain occurred during charge-discharge cycling. The glassy matrix surrounding the alloy was investigated using P-31 MAS-NMR. The P2O74- group might be changed to PO43- and P2O64- groups by the first lithium insertion to the glass. The formed phosphate groups remained after the consecutive lithium extraction process. An all-solid-state cell with the 67SnO center dot 33P(2)O(5) glass exhibited the discharge capacity of 750 mAh g(-1) at the first cycle, which is greater than that of a cell with the 50SnO center dot 50B(2)O(3) glass. (C) 2007 Published by Elsevier B.V.
  • Kenji Takahashi, Kiyoharu Tadanaga, Akitoshi Hayashi, Atsunori Matsuda, Masahiro Tatsumisago
    JOURNAL OF NON-CRYSTALLINE SOLIDS 354 (2-9) 700 - 704 0022-3093 2008/01 [Not refereed][Not invited]
     
    Spherical poly(phenylsilsesquioxane) (PhSiO(3)/2) particles prepared using a two-step acid-base catalyzed sol-gel process had a 'core-shell' structure: their inside and outside parts were composed respectively of PhSiO(3/2) species with low and high molecular weights. The PhSiO(3/2) particles prepared using the two-step acid-base catalyzed sol-gel process exhibited two glass transition temperatures (T,). The PhSiO(3/2) species in the inside of the particles showed glass transition behavior at a lower temperature than those in the outside of the particles, indicating that T(g) is mainly dependent on the materials' respective molecular weights. (C) 2007 Elsevier B.V. All rights reserved.
  • Kiyoharu Tadanaga, Naoko Yamaguchi, Atsunori Matsuda, Tsutomu Minami, Masahiro Tatsumisago
    JOURNAL OF ADHESION SCIENCE AND TECHNOLOGY 22 (3-4) 387 - 394 0169-4243 2008 [Not refereed][Not invited]
     
    Alumina thin films, with roughness of 20-50 nm and pseudoboehmite nanocrystals precipitated on the surface, were formed through immersion of porous alumina gel films in hot water. By coating hydrolyzed fluoroalkylsilane on such a thin film with slight roughness, a superhydrophobic surface with high transparency was obtained. Additives such as hydrochloric acid, sodium hydroxide, sodium chloride, manganese chloride, ethanol and ethylene glycol were dissolved in the hot water, and the effects of these additives on pseudobochmite nanocrystal formation during hot water treatment were examined. Pseudoboehmite nanocrystals were formed at pH = 5.5-8.0 when an acid or a base was added to water. The addition of inorganic salts and alcohol diminished the boehmite nanocrystal formation. These results suggest that the boehmite nanocrystals were formed through a dissolution and re-precipitation process. (c) Koninklijke Brill NV, Leiden, 2008
  • Kenji Takahashi, Kiyoharu Tadanaga, Akitoshi Hayashi, Atsunori Matsuda, Kiyofumi Katagiri, Masahiro Tatsurnisago
    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY 7 (9) 3307 - 3312 1533-4880 2007/09 [Not refereed][Not invited]
     
    Spherical polyphenylsilsesquioxane (PhSiO(3/2)) particles, one of the inorganic-organic hybrid materials, were synthesized by a two-step acid-base catalyzed sol-gel process, and hollow particles were successfully prepared by washing the as-prepared particles with organic solvents. It was found that the inside and outside parts of the as-prepared particles were composed of PhSiO(3/2) species with relatively low and high molecular weight, respectively, i.e., the PhSiO(3/2) particles had a kind of "core-shell" structure. Because the core portion in the as-prepared particles was soluble in ethanol and tetrahydrofuran, hollow particles were obtained through washing the as-prepared PhSiO(3/2) particles with ethanol or tetrahydrofuran. Furthermore, the molecular weight of the as-prepared particles was varied by the concentration of phenyltriethoxysilane used as a starting alkoxide. As a result of the variation of the molecular weight, the hollow PhSiO(3/2) particles with different stabilities against organic solvents were formed.
  • Kenji Takahashi, Kiyoharu Tadanaga, Atsunori Matsuda, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 43 (1) 85 - 91 0928-0707 2007/07 [Not refereed][Not invited]
     
    Polybenzylsilsesquioxane (BnSiO3/2) particles become a supercooled liquid through a heat treatment above the glass transition temperature (T (g)) of the particles. Micropatterns of BnSiO3/2 thick films with high transparency were obtained by the electrophoretic deposition of the BnSiO3/2 particles on indium tin oxide (ITO)-coated substrates with a hydrophobic-hydrophilic-patterned surface and subsequent heating above T (g) of the particles. It was found that the control of electrophoretic deposition conditions, in which the amounts of the particles deposited on the substrates were changed, led to two types of micropatterning processes of the BnSiO3/2 thick films. In the first process, the particles were selectively deposited on the hydrophilic areas after the electrophoretic deposition. In the second process, the particles were deposited on the whole area of the ITO-coated substrate with hydrophobic-hydrophilic patterns after the electrophoretic deposition. Due to the difference in wettability of BnSiO3/2 molten liquids between hydrophobic and hydrophilic surfaces, the molten liquids on the hydrophobic areas, which were obtained by heating above T (g) of the particles, migrated toward the hydrophilic areas. In both the processes, convex-shaped BnSiO3/2 micropatterns with high transparency were fabricated only on the hydrophilic areas after a heat treatment above T (g) of the particles.
  • Naoko Yamaguchi, Daisuke Ando, Kiyoharu Tadanaga, Masahiro Tatsumisago
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 90 (6) 1940 - 1942 0002-7820 2007/06 [Not refereed][Not invited]
     
    Amorphous Al(2)O(3)-MgO thin films with an Mg/Al ratio of unity were prepared on glass substrates by the sol-gel method with a heat treatment at 300 degrees C for 30 min. By immersing the films in water containing sodium hydroxide (pH 10-13) at 100 degrees C, nano-crystals of Mg-Al-layered double hydroxide (LDH) with a hexagonal structure, which is called hydrotalcite and the most basic composition of LDH, were precipitated on the amorphous Al(2)O(3)-MgO films. The maximum amount of Mg-Al nanocrystals was obtained when the film was immersed in basic solution of pH 12.
  • Teruaki Tezuka, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    SOLID STATE IONICS 178 (7-10) 705 - 708 0167-2738 2007/04 [Not refereed][Not invited]
     
    W, have prepared novel proton conducting inorganic-organic hybrid membranes from 3-aminopropyltriethoxysilane (APTES) and H(2)SO(4) by the sol-gel method. The resulting poly(3-aminopropylsitsesquioxane sulfate or hydrogensulfate) (PAPS-SO(4)/-HSO(4)) membranes were thermally stable up to 300 degrees C. From the results of IR spectra, it was confirmed that sulfuric acids in the membranes react with amino groups of PAPS to form ion complexes. XRD patterns of the PAPS-SO(4)/-HSO(4) membranes showed diffraction peaks assigned to hexagonal structure, which is probably formed by stacking of rodlike polysiloxanes with the ion complexes extruded outside. The PAPS-SO(4)/-HSO(4) membranes with a molar ratio of H(2)SO(4)/APTES = 1.0 showed high proton conductivities of 2 x 10(-3) S cm(-1) at 200 degrees C under dry condition. (c) 2007 Elsevier B.V All rights reserved.
  • Atsunori Matsuda, Yusuke Daiko, Tomohiko Ishida, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Solid State Ionics 178 (7-10) 709 - 712 0167-2738 2007/04 [Refereed][Not invited]
     
    Dodecatungstophosphoric acid (H3PW12O40·nH2O) and SiO2 were mechanically milled, and a new class of proton-conductive composites was prepared. The conductivity of WPA-SiO2 composite with P/Si = 0.1 was 3 × 10- 3 S cm- 1 at 30 °C and 60% relative humidity (RH), which was higher than that (6 × 10- 4 S cm- 1) of the corresponding mixture before milling. In the medium temperature range, the WPA-SiO2 composite retained relatively high conductivity of 1 × 10- 4 S cm- 1 at 100 °C and 2% RH, which was higher by one order of magnitude than that of the mixture without milling. These higher values of conductivity for the milled composite can be ascribed to the presence of mechanochemically formed surface defects such as Si-OH and P-OH groups. © 2007 Elsevier B.V. All rights reserved.
  • Kenji Takahashi, Kiyoharu Tadanaga, Atsunori Matsuda, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 41 (3) 217 - 222 0928-0707 2007/03 [Not refereed][Not invited]
     
    Polyphenylsilsesquioxane (PhSiO(3/2)) particles were synthesized by a two-step acid-base catalyzed sol-gel process, in which phenyltriethoxysilane used as a starting alkoxide was hydrolyzed and condensed in the first step under two different acid-catalyzed conditions. The PhSiO(3/2) particles prepared under an acid-catalyzed process without using a solvent were thermally hardened after the first heating up to 200 degrees C. In contrast, the PhSiO(3/2) particles prepared under an acid-catalyzed process with ethanol as a solvent were thermally softened with the repeated heating processes up to 200 degrees C. From the gel permeation chromatography measurements, it was found that the average molecular weight of the particles prepared with the use of ethanol was decreased in comparison with that of the particles prepared without using ethanol. The addition of ethanol in the sols during hydrolysis and condensation reaction under the acid-catalyzed process caused the decrease in the average molecular weight, which should result in the changes of thermal property of PhSiO(3/2) particles from thermosetting to thermoplastic.
  • Kenji Takahashi, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    CHEMISTRY LETTERS 36 (2) 324 - 325 0366-7022 2007/02 [Not refereed][Not invited]
     
    Spherical polyaminophenylsilsesquioxane (H2NC6H4SiO3/2) particles were prepared by a two-step acid-base-catalyzed sol-gel process, and we found that the particles showed the glass transition behavior. Amino groups in the H2NC6H4SiO3/2 particles were partially changed to amido ones by acetylation using acetic anhydride.
  • Naoko Yamaguchi, Kiyoharu Tadanaga, Atsunori Matsuda, Tsutomu Minami, Masahiro Tatsumisago
    THIN SOLID FILMS 515 (7-8) 3914 - 3917 0040-6090 2007/02 [Not refereed][Not invited]
     
    The antireflective (AR) properties of Al(2)O(3) thin films with small roughness on soda-lime silica glass substrates were investigated. By immersing porous Al(2)O(3) thin films in hot water, nanocrystals of pseudoboehmite were formed on the film surface. The reflectance of the Al(2)O(3) films treated with hot water for 30 min was less than 0.5% in the wavelength region of 360-620 nm. The Al(2)O(3) films with small roughness resulting from the hot water treatment become denser from their surface to the interface with the substrate, and the refractive index gradient brought by the structure results in excellent AR properties. (c) 2006 Elsevier B.V. All rights reserved.
  • TAKAHASHI Kenji, TADANAGA Kiyoharu, MATSUDA Atsunori, HAYASHI Akitoshi, TATSUMISAGO Masahiro
    Journal of the Ceramic Society of Japan 公益社団法人日本セラミックス協会 115 (1338) 131 - 135 1882-1022 2007/02/01 
    Spherical polyphenylsilsesquioxane particles were prepared by a two-step acid-base catalyzed sol-gel process, in which various amounts of ethanol were used as a solvent to vary the concentration of phenyltriethoxysilane (PhSi(OEt)_3) used as a starting alkoxide. The decrease in the PhSi (OEt)_3 concentration led to the decrease in the average molecular weight and glass transition temperature of the polyphenylsilsesquioxanes. Thus, the change of the PhSi (OEt)_3 concentration in the preparation of polyphenylsilsesquioxane particles by the two-step acid-base catalyzed sol-gel process is an effective means to control the glass transition temperature of the particles.
  • Kenji Takahashi, Kiyoharu Tadanaga, Atsunori Matsuda, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 115 (1338) 131 - 135 1882-0743 2007/02 [Refereed][Not invited]
     
    Spherical polyphenylsilsesquioxane particles were prepared by a two-step acid-base catalyzed sol-gel process, in which various amounts of ethanol were used as a solvent to vary the concentration of phenyltriethoxysilane (PhSi (OEt)(3)) used as a starting alkoxide. The decrease in the PhSi (OEt) 3 concentration led to the decrease in the average molecular weight and glass transition temperature of the polyphenylsilsesquioxanes. Thus, the change of the PhSi (OEt)(3) concentration in the preparation of polyphenylsilsesquioxane particles by the two-step acid-base catalyzed sol-gel process is an effective means to control the glass transition temperature of the particles.
  • Preparation of Proton Conductive Composites with CsHSO4/CsH2PO4 and Phosphosilicate Gel
    T. Tezuka, K. Tadanaga, A. Hayashi, M. Tatsumisago
    Solid State Ionics 177 (2463) 2466  2007 [Not refereed][Not invited]
  • Kenji Takahashi, Kiyoharu Tadanaga, Atsunori Matsuda, Akitoshi Hayashi, Masahiro Tatsumisago
    Journal of the Ceramic Society of Japan 115 (1338) 131 - 135 1348-6535 2007 [Not refereed][Not invited]
     
    Spherical polyphenylsilsesquioxane particles were prepared by a two-step acid-base catalyzed sol-gel process, in which various amounts of ethanol were used as a solvent to vary the concentration of phenyltriethoxysilane (PhSi(OEt)3) used as a starting alkoxide. The decrease in the PhSi(OEt)3 concentration led to the decrease in the average molecular weight and glass transition temperature of the polyphenylsilsesquioxanes. Thus, the change of the PhSi(OEt)3 concentration in the preparation of polyphenylsilsesquioxane particles by the two-step acid-base catalyzed sol-gel process is an effective means to control the glass transition temperature of the particles.
  • Naoko Yamaguchi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    ADVANCES IN NANOMATERIALS AND PROCESSING, PTS 1 AND 2 124-126 635 - + 1012-0394 2007 [Not refereed][Not invited]
     
    Zn-Al layered double hydroxide (LDH) thin films intercalated with various organic anions were prepared by immersion of sol-gel derived amorphous Al2O3-ZnO thin films in hot water containing organic salts like sodium dodecyl sulfate (SDS), sodium p-toluenesulfonate, and benzenecarboxylates. In all the systems, extended interlayer spacing of the Zn-Al LDH was observed after immersion in distilled water with the organic salts in comparison to the LDH with carbonate anions, indicating that we have succeeded in direct formation of Zn-Al LDH films with various organic anions on the substrates. It is suggested that divalent anions such as terephthalate ion have higher selectivity than monovalent anions.
  • Atsunori Matsuda, Ryohei Ogawa, Yusuke Daiko, Kiyoharu Tadanaga, Masahiro Tatsumisago
    JOURNAL OF PHOTOPOLYMER SCIENCE AND TECHNOLOGY 20 (1) 101 - 105 0914-9244 2007 [Not refereed][Not invited]
     
    Transparent vinylsilsesquioxane-titania (ViSiO(3/2)-TiO(2)) hybrid gel films were prepared from vinyltriethoxysilane and titanium tetrabutoxide by the sol-gel method. UV light irradiation partly cleaved Si-C bonds and addition-polymerized C = C bonds to form Si-O-Si and Si(CH(2))(n)Si linkage in the hybrid films due to the photosensitizing effect of TiO(2) component. The refractive index and dynamic hardness of the hybrid films increased, and the thickness and contact angle for water decreased by the structural changes induced by the UV light irradiation. in comparison with several kinds of organosilsesquioxane-titania (RSiO(3/2)-TiO(2), R=methyl, ethyl, phenyl and benzyl) hybrid gel films, ViSiO(3/2)-TiO(2) was found to show the largest increase in hardness due to the formation Of Si(CH2)nSi linkage. Micropatterning was successfully performed on the ViSiO(3/2)-TiO(2) hybrid films by UV light irradiation through a photomask. The patterned film can be applied as a printing plate with the surface energy differences as well as a micro-optical component with the surface profiles and refractive index differences.
  • Mechanochemical Synthesis of Proton Conductive M3H(SO4)2 (M=Na,K, Rb) Crystatls
    T. Tezuka, Y. Yamashita, A. Hayashi, K, Tadanaga, M. Tatsumisago
    Chem. Sustainable Development 15 237 - 241 2007 [Not refereed][Not invited]
  • Hirokazu Kitaura, Kenji Takahashi, Fuminori Mizuno, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 154 (7) A725 - A729 0013-4651 2007 [Not refereed][Not invited]
     
    alpha-Fe2O3 particles of various sizes were prepared by a solution process and were applied to the electrodes for all-solid-state lithium rechargeable batteries. The prepared alpha-Fe2O3 was monodispersed particles with sizes controlled from about 250 nm to 3.7 mu m. Their electrochemical properties were examined for the all-solid-state cells with highly conductive Li2S-P2S5 solid electrolytes and the influences of the particle size of alpha-Fe2O3 on the electrochemical performance of the cells were investigated. The first discharge capacities increased with decreasing the particle size of alpha-Fe2O3 and the cell using the smallest alpha-Fe2O3 particles of 250 nm showed the highest capacity of 1050 mAh g(-1). The charge-discharge reaction mechanism in the all-solid-state cells was investigated by means of X-ray diffraction and was revealed to be similar to that in conventional cells with a liquid electrolyte. The lithium intercalation to alpha-Fe2O3 occurred in the initial stage of the first discharge only in the cases using alpha-Fe2O3 particles with small crystallite size, large specific surface area and large pore volume. By controlling the cutoff voltage, the all-solid-state cell retained the constant capacity of about 130 mAh g(-1) for 15 cycles at the current density of 0.064 mA cm(-2). The rate capability at 25 degrees C and temperature dependence of the first discharge capacity in the all-solid-state cells were also investigated. The cell at 60 degrees C showed the larger first-discharge capacity of 940 mAh g(-1) at the current density of 1.27 mA cm(-2). (C) 2007 The Electrochemical Society.
  • Naoko Yamaguchi, Kiyoharu Tadanaga, Atsunori Matsuda, Tsutomu Minami, Masahiro Tatsumisago
    SURFACE & COATINGS TECHNOLOGY 201 (6) 3653 - 3657 0257-8972 2006/12 [Not refereed][Not invited]
     
    Al(2)O(3) films with a small roughness of less than 100 nm prepared through the sol-gel method have been found to show anti-reflective (AR) property in a wide wavelength region on polymer substrates such as poly(ethylene terephtalate) (PET), poly carbonate (PC), and poly(methyl methacrylate) (PMMA). The highest AR effects were obtained on PMMA substrates, the refractive index of which is similar to that of porous Al(2)O(3) gel films. The reflectance of PET, PC, and PMMA substrates coated with flowerlike Al(2)O(3) was less than 1.5, 1.0, and 0.8% in the visible light region, respectively. (c) 2006 Elsevier B.V. All rights reserved.
  • Atsunori Matsuda, Yugo Higashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    JOURNAL OF MATERIALS SCIENCE 41 (24) 8101 - 8108 0022-2461 2006/12 [Not refereed][Not invited]
     
    SiO2-TiO2 spherical microparticles of about 0.7 mu m in diameter were prepared by the sol-gel method. Anatase nanocrystals were formed in the microparticles and their specific surface area was increased after a hot-water treatment at 90 degrees C. From the changes in the concentration of I-2 photocatalytically generated from KI aqueous solution, the activity of the SiO2-TiO2 microparticles was found to increase with increasing the hot-water treatment time. Particulate, thick films were electrophoretically deposited on indium tin oxide (ITO)-coated glass substrates using the anatase nanocrystal-precipitated SiO2-TiO2 microparticles. The thickness of the electrophoretically deposited particulate film increased to be approximately 10 mu m with an increase in applied voltage. The resultant thick film showed a high photocatalytic activity.
  • Teruaki Tezuka, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY 128 (51) 16470 - 16471 0002-7863 2006/12 [Not refereed][Not invited]
  • Kiyoharu Tadanaga
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 40 (2-3) 281 - 285 0928-0707 2006/12 [Not refereed][Not invited]
     
    A process to prepare nanocrystals-dispersed thin films at low temperatures using a hot water treatment of the gel films, and application of these nanocomposite thin films were demonstrated. When amorphous Al2O3 gel films were immersed in a hot water, we found that boehmite nanocrystals were formed on the surface of the films. In the hot water treatment of Al2O3-ZnO amorphous films, Zn-Al layered double hydroxide (LDH) was found to be formed on the films. When the SiO2-TiO2 gel films containing poly(ethylene glycol) were treated in a hot water, anatase nanocrystals were formed on the surface and inside of the films, and for the gel films without an organic polymer, the anatase nanocrystals were formed only on the surface of the films. In the hot water treatment of SiO2-TiO2 gel films under a vibration, titania nanosheets were found to be precipitated, instead of anatase nanocrysltals. Since formation of nanocrystals on the substrates using a hot water treatment is very mild conditions as the precipitation of crystals, we believe this process will open new application fields of nanocystals-dispersed thin films.
  • Kenji Takahashi, Kiyoharu Tadanaga, Akitoshi Hayashi, Masahiro Tatsumisago, Atsunori Matsuda
    Journal of the American Ceramic Society 89 (12) 3832 - 3835 0002-7820 2006/12 [Refereed][Not invited]
     
    Poly(benzylsilsesquioxane) (BnSiO3/2) particles show glass transition behavior, and the particles become a supercooled liquid when they are heated at temperatures above the glass transition temperature. Contact angles of BnSiO3/2 molten liquid on the hydrophobic surface with fluoroalkylsilane and hydrophilic surface with silica were found to be around 77° and 12°, respectively. Using the difference in wettability for BnSiO3/2 molten liquid between the hydrophobic and hydrophilic surfaces, micro-patterns of transparent BnSiO3/2-thick films were formed by the electrophoretic deposition of BnSiO3/2 particles on indium tin oxide substrates with hydrophobic-hydrophilic patterns and subsequent heating above the glass transition temperature. © 2006 The American Ceramic Society.
  • Atsunori Matsuda, Naoki Nakamoto, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    SOLID STATE IONICS 177 (26-32) 2437 - 2441 0167-2738 2006/10 [Not refereed][Not invited]
     
    Thermally stable, flexible, and proton conductive composite sheets have been prepared from phosphosilicate (P(2)O(5)-SiO(2), P/Si = 1 in mole ratio) gel powder and several kinds of organic polymers. The organic polymers examined were polyimide (PI), polyamideimide (PAI), polyvinylidene fluoride (PVdF) and styrene-ethylene-butylenes-styrene elastomer (SEBS). PI and PAI effectively improved the chemical durability of the composite sheets by depressing the leaching of phosphoric acid from the gel. PVdF and SEBS provided the composite sheets with an excellent flexibility. Fuel cells using the membrane electrode assembly (MEA) composed of the composite sheet as an electrolyte and Pt-loaded carbon paper sheets as electrodes operated at temperatures in the range from room temperature to medium temperatures (similar to 150 degrees C) . (c) 2006 Elsevier B.V. All rights reserved.
  • Fuminori Mizuno, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    SOLID STATE IONICS 177 (26-32) 2721 - 2725 0167-2738 2006/10 [Not refereed][Not invited]
     
    Highly ion-conductive Li2S-P2S5 glass-ceramic electrolytes were prepared by controlling the compositions and heat treatment temperatures of the glasses. The 70Li(2)S.30P(2)S(5) (mol%) glass-ceramic heated at 360 degrees C showed the highest conductivity of 3.2 x 10(-3) S cm(-1) at room temperature and the lowest activation energy of 12 kJ mol(-1) for conduction in the binary system Li2S-P2S5. The outstanding property was attributed to both the precipitation of the new crystal as a metastable phase and the increase in crystallinity of the phase. With increasing heat treatment temperatures, the metastable phase changed into thermodynamically stable phases such as the Li4P2S6 crystal by heat treatment up to 550 degrees C, resulting in low conductivities of the glass-ceramics. It was, thus, found that the formation of superionic metastable phases by heating the Li2S-P2S5 glasses is responsible for the marked enhancement on the conducting properties of the glass-ceramics. (c) 2006 Elsevier B.V. All rights reserved.
  • Fuminori Mizuno, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    SOLID STATE IONICS 177 (26-32) 2731 - 2735 0167-2738 2006/10 [Not refereed][Not invited]
     
    Composite positive electrodes for all-solid-state In/LiCoO2 cells with Li2S-P2S5 glass-ceramic electrolytes were designed in order to improve rate performances of the cells. In the composite positive electrodes with LiCoO2 in 40 wt.% and the glass-ceramic electrolyte in 60 wt.%, suitable lithium ion conducting paths were formed, and the addition of vapor grown carbon fiber (VGCF) made it easier to form electron-conducting paths. The solid-state cell kept high capacities of about 90 mAh g(-1) even under high current densities of over 1 mA cm(-2) after charged and discharged under low current densities for 100 cycles. It was, thus, suggested that high rate performances of all-solid-state cells were achieved by controlling the mixed state of composite electrodes and the operating condition during charge-discharge cycles. (c) 2006 Elsevier B.V. All rights reserved.
  • Akitoshi Hayashi, Takanori Konishi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    SOLID STATE IONICS 177 (26-32) 2737 - 2740 0167-2738 2006/10 [Not refereed][Not invited]
     
    All-solid-state cells with the SnX-P2X5 (X = S and 0) glassy electrodes and the ce:inf > S/ce:inf > S-P2S5 glass-ceramic electrolytes were fabricated, and their electrochemical performance was examined. The 67SnS.33P(2)S(5) (mol%) glassy electrode exhibited higher capacity of about 400 mAhg(-1) than the 67SnO.33P(2)O(5) glass and the SnS crystal. In the case of using the 67SnS.33P(2)S(5) glass as an active material, the cell using the composite electrode consisting of active material and conductive additive (acetylene-black) powders showed almost the same charge-discharge behaviors as the cell using the conventional composite electrode consisting of active material, conductive additive, and the solid electrolyte powders. The similarity of cell performance suggests that the highly Li+ ion conductive ce:inf > S/ce:inf > S-P2S5 solid electrolytes were formed by electrochemical Li insertion to the SnS-P2S5 electrode; the self-formed electrolyte supplied a Li+ ion conduction path in the composite electrode. A close electrode-electrolyte interface, which is important to develop all-solid-state batteries, would be established by utilizing the self-formation process of solid electrolyte. (c) 2006 Elsevier B.V. All rights reserved.
  • Fuminori Mizuno, Takamasa Ohtomo, Akitoshi Hayashi, Kiyoharu Tadanaga, Masahiro Tatsumisago
    SOLID STATE IONICS 177 (26-32) 2753 - 2757 0167-2738 2006/10 [Not refereed][Not invited]
     
    Glassy electrolyte of 80Li(2)S.20P(2)S(5) (mol%) was prepared by mechanical milling of Li2S and the mixture of elemental phosphorus and sulfur, which was mechanically milled in advance (two-step process). The glass showed relatively low conductivity of 3.9 x 10(-5) S cm(-1) at room temperature, while the glass-ceramic obtained by crystallization exhibited higher conductivity of 4.3 x 10(-4) S cm(-1) than the pristine glass. Raman spectroscopy revealed that the glass was mainly composed of the PS43- ions and slightly contained homo bonds such as P-P and S-S bonds. The mechanochemical synthesis using the two-step process was effective in reducing the homo bonds in the glassy electrolytes. The glass-ceramic, in which a highly ion-conductive thio-LISICON analog was precipitated, was mainly composed of the PS43- ions and very small amounts of S-S bonds. Cyclic voltammmetry demonstrated that the Li2S-P-S glass-ceramic had wide electrochemical window of 5 V. (c) 2006 Elsevier B.V. All rights reserved.
  • Kenji Takahashi, Kiyoharu Tadanaga, Masahiro Tatsumisago, Atsunori Matsuda
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 89 (10) 3107 - 3111 0002-7820 2006/10 [Not refereed][Not invited]
     
    Poly(phenylsilsesquioxane)-titania (PhSiO3/2-TiO2) hybrid particles were prepared from phenyltriethoxysilane and titanium tetra-n-butoxide by the sol-gel method. Fourier transform infrared spectra showed that PhSiO3/2 and the TiO2 components were hybridized through Si-O-Ti bonds. The refractive index of the particles was monotonically increased from 1.57 to 1.62 with an increase in the TiO2 content. The PhSiO3/2-TiO2 particles were electrophoretically deposited on indium tin oxide (ITO)-coated glass substrates to form opaque, thick films about 3 mu m in thickness. When the mole ratio x in (1-x)PhSiO3/2.xTiO(2) was equal to or less than 0.05, the deposited PhSiO3/2-TiO2 films became transparent with a heat treatment at 400 degrees C because of the thermal sintering of the particles.
  • Naoko Yamaguchi, Tomohiko Nakamura, Kiyoharu Tadanaga, Atsunori Matsuda, Tsutomu Minami, Masahiro Tatsumisago
    CRYSTAL GROWTH & DESIGN 6 (7) 1726 - 1729 1528-7483 2006/07 [Not refereed][Not invited]
     
    Amorphous Al(2)O(3)-ZnO thin films with various Zn/Al ratios were prepared on glass substrates by the sol-gel method with a heat treatment at 400 degrees C for 30 min followed by immersion of the films in distilled water at 100 degrees C to form nanocrystalline Zn-Al layered double hydroxide (LDH) with hexagonal structure. Zn-Al LDH nanocrystals were precipitated on the amorphous Al(2)O(3)-ZnO films with various Zn/Al ratios, and the maximum amount of nanocrystals was formed on the film of the Zn/Al atomic ratio of unity. Zn-Al LDH crystals with the size of 200-500 nm have been precipitated on glass substrates through hot water treatment at temperatures lower than 100 degrees C.
  • Kenji Takahashi, Kiyoharu Tadanaga, Atsunori Matsuda, Akitoshi Hayashi, Masahiro Tatsumisago
    JOURNAL OF MATERIALS RESEARCH 21 (5) 1255 - 1260 0884-2914 2006/05 [Not refereed][Not invited]
     
    Hydrophobic-hydrophilic patterns were formed on indium tin oxide substrates, and thick films of poly(phenylsilsesquioxane) (PhSiO3/2) particles, prepared by the sol-gel process, were selectively deposited onto hydrophilic areas of the substrates by electrophoresis. The films composed of PhSiO3/2 particles became transparent with morphological changes from aggregates of particles to a continuous phase after a heat treatment. After heat treatment at 200 degrees C, convex-shaped PhSiO3/2 micropatterns were formed on the hydrophilic region of the pattern. Moreover, the height of micropatterns was controlled by the deposition time. This patterning technique has a wide variety of applications such as fabrication of micro-optical components.
  • N Yamaguchi, T Nakamura, K Tadanaga, A Matsuda, T Minami, M Tatsumisago
    CHEMISTRY LETTERS 35 (2) 174 - 175 0366-7022 2006/02 [Not refereed][Not invited]
     
    We have successfully immobilized Zn-Al layered double hydroxide (LDH) directly on glass substrates through the sol-gel method with hot water treatment. Al2O3-ZnO thin films were originally prepared on glass substrates by the sol-gel method with a heat treatment at 400 degrees C for 30 min, and then the films were immersed in distilled water at 100 degrees C for 15 min to form nanocrystalline Zn-Al LDH with hexagonal structure.
  • Kiyoharu Tadanaga, Toshitsugu Sueki, Atsunori Matsuda, Tsutomu Minami, Masahiro Tatsumisago
    Journal of the Ceramic Society of Japan 114 (1325) 125 - 127 1348-6535 2006 [Not refereed][Invited]
     
    Inorganic-organic hybrid films with a maximum thickness of about 40 μm were prepared from vinyltriethoxysilane (VTES) through a sol-gel process. UV light from a high-pressure mercury lamp was irradiated through a photomask on the hybrid films from VTES. IR and 29Si NMR spectra of the coating films showed that C = C bonds in VTES were polymerized by UV irradiation. Micropatterns with a maximum height of about 40 μm were formed by the etching of unirradiated area of the films.
  • Kiyoharu Tadanaga, Kenji Takahashi, Masahiro Tatsumisago, Atsunori Matsuda
    Key Engineering Materials 314 159 - 164 1013-9826 2006 [Not refereed][Not invited]
     
    Micropatterns of phenylsilsesquioxane thick films have been prepared by electrophoretic sol-gel deposition using ITO-coated substrates with a hydrophobic-hydrophilic patterned surface. After the electrophoretic deposition, phenylsilsesquioxane thick films were formed only on hydrophilic areas on the pattern. These thick films obtained immediately after the electrophoretic deposition were opaque due to light scattering. However, phenylsilsesquioxane particles in the films were morphologically changed from aggregates of the spherical particles to continuous phase by a heat treatment process, and finally convex shaped phenylsilsesquioxane micropatterns were formed only on the hydrophilic areas.
  • Atsunori Matsuda, Mototsugu Sakai, Toshihiro Kogure, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of the Ceramic Society of Japan 114 (1325) 26 - 35 1348-6535 2006 [Not refereed][Not invited]
     
    This review paper is focused on the area of titania nanocoatings prepared from sol-gel derived films by hot-water treatment under external reaction fields to design their functionality through the control of their surface morphology and crystallinity at low processing temperatures. First, the formation of titania nanocrystalline coatings at low temperatures by wet chemical procedures is briefly reviewed. Second, a concept of material design based on an external-field hot-water treatment for sol-gel derived films and the effects of the external fields on the formation of titania nanocrystals from the sol-gel derived films are discussed. Finally, promising characteristics of the resultant titania nanocrystal-dispersed coatings with unique morphology are described. External fileds of vibrations and electric voltages affect the nanostructure of titania crystallites formed on SiO 2-TiO2 gel coatings during hot-water treatment. Without the external fields granular anatase nanocrystals of 30-50 nm in size are formed on the coatings during the hot-water treatment, whereas the shape of the precipitates becomes sheetlike by applying a vibration to the substrate during hot-water treatment. Similar changes in shape of the precipitates on the coatings are also observed, and ramiform (branchlike) crystallites are formed at the negative electrode by applying an electric field between the substrates. The sheetlike and ramiform crystallites are mainly composed of a hydrated titania, m(TiO2)· nH2O, with the lepidocrocite-like layered structure with a rf-spacing of 0.6-0.8 nm. Titania nanosheets are characterized by a large surface-to-volume ratio, which gives rise to the excellent wettability for water and antifogging properties. Processing temperatures for the preparation of the coatings are lower than 100°C under atmospheric pressure, so that the coatings have a great potential for applications to various substrates including organic polymers with poor heat resistance.
  • All-Solid-State Rechargeable Lithium Batteries Using SnX-P2X5(X=S and O)Amorphous Negative Electrodes
    A. Hayashi, T. Konishi, K. Tadanaga, T. Minami, M. Tatsumisago
    Research on Chemical Intermediates 32 (5-6) 497 - 506 2006 [Not refereed][Not invited]
  • Electrophoretic Deposition of Sol-Gel Derived V2O5 Microparticles and Its Application for Cathodes for Li-Secondary Batteries
    A. Matsuda, Y. Higashi, K. Tadanaga, T. Minami, M. Tatsumisago
    Key Engineering Materials 314 107 - 111 2006 [Not refereed][Not invited]
  • Titania Nanocrystals-Dispersed Coatings from SiO2-TiO2 Gel Films through Hydrolysis and Dissolution
    A. Matsuda, T. Kogure, H. Muto, M. Sakai, K. Tadanaga, T. Minami, M. Tatsumisago
    Key Engineering Materials 317-318 565 - 568 2006 [Not refereed][Not invited]
  • A. Matsuda, Y. Higashi, K. Tadanaga, T. Minami, M. Tatsumisago
    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS II 314 107 - 111 1013-9826 2006 [Refereed][Not invited]
     
    V2O5 microparticles of 0.3-0.6 mu m in diameter were prepared from VO(O-C3H7i)(3) in an ethanol solution by the sol-gel method. The addition of poly(ethylene glycol) and acetyl acetone into the sols was effective to control the size and spherical shape Of V2O5 particles. The particles thus obtained were amorphous having a layered structure with hydrated water, and transformed into an orthorhombic phase at 500 degrees C through a glassy state. The microparticles were positively charged in I-2-containing acetone, so that they were electrophoretically deposited on the cathode with applied DC voltage. The prepared particles were used as a cathode in an electrochemical cell with a lithium metal as an anode. Discharge capacity of a rechargeable cell of Li/LiPF6 (ethylene carbonate + diethylene carbonate) / V2O5-based composite was 110-180 mAh g(-1) when the potential range and current density were 2-4 V and 0.1 m-Acm(-2), respectively.
  • A. Matsuda, T. Kogure, H. Muto, M. Sakai, K. Tadanaga, T. Minami, M. Tatsumisago
    SCIENCE OF ENGINEERING CERAMICS III 317-318 565 - 568 1013-9826 2006 [Refereed][Not invited]
     
    Anatase nanocrystals were formed on sol-gel derived SiO(2)-TiO(2) coatings with water vapor or hot water treatments. The anatase nanocrystals were precipitated through hydrolysis of Si-O-Ti bonds, dissolution Of SiO(2) component, migration of hydrolyzed titania species, and nucleation and growth. The process temperatures can be lowered below 60 degrees C, which should open new applications. It was found that the crystal habit of titania was changes from roundish anatase to sheet-like titania by applying vibration during the hot water treatment. The nanosheets were identified as hydrated titania, TiO(2) mH(2)O, with layerd structure. The coatings of hydrated titania showed high photocatalytic activities and excellent antifogging properties due to their unique morphology.
  • A Matsuda, M Sakai, T Kogure, K Tadanaga, M Tatsumisago
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 (1325) 26 - 35 1882-0743 2006/01 [Refereed][Not invited]
     
    This review paper is focused on the area of titania nanocoatings prepared from sol-gel derived films by hot-water treatment under external reaction fields to design their functionality through the control of their surface morphology and crystallinity at low processing temperatures. First, the formation of titania nanocrystalline coatings at low temperatures by wet chemical procedures is briefly reviewed. Second, a concept of material design based on an external-field hot-water treatment for sol-gel derived films and the effects of the external fields on the formation of titania nanocrystals from the sol-gel derived films are discussed. Finally, promising characteristics of the resultant titania nanocrystal-dispersed coatings with unique morphology are described. External fileds of vibrations and electric voltages affect the nanostructure of titania crystallites formed on SiO2-TiO2 gel coatings during hot-water treatment. Without the external fields granular anatase nanocrystals of 30-50 nm in size are formed on the coatings during the hot-water treatment, whereas the shape of the precipitates becomes sheet-like by applying a vibration to the substrate during hot-water treatment. Similar changes in shape of the precipitates on the coatings are also observed, and ramiform (branchlike) crystallites are formed at the negative electrode by applying an electric field between the substrates. The sheetlike and ramiform crystallites are mainly composed of a hydrated titania, m (TiO2) center dot nH(2)O, with the lepidocrocite-like layered structure with a d-spacing of 0.6-0.8 urn. Titania nanosheets are characterized by a large surf ace-to-volume ratio, which gives rise to the excellent wettability for water and antifogging properties. Processing temperatures for the preparation of the coatings are lower than 100 degrees C under atmospheric pressure, so that the coatings have a great potential for applications to various substrates including organic polymers with poor heat resistance.
  • K Tadanaga, T Sueki, A Matsuda, T Minami, M Tatsumisago
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 114 (1325) 125 - 127 1882-0743 2006/01 [Refereed][Not invited]
     
    Inorganic-organic hybrid films with a maximum thickness of about 40 mu m were prepared from vinyltriethoxysilane (VTES) through a sol-gel process. UV light from a high-pressure mercury lamp was irradiated through a photomask on the hybrid films from VTES. IR and Si-29 NMR spectra of the coating films showed that C=C bonds in VTES were polymerized by UV irradiation. Micropatterns with a maximum height of about 40 mu m were formed by the etching of unirradiated area of the films.
  • A Matsuda, T Tezuka, Y Nono, K Tadanaga, T Minami, M Tatsumisago
    SOLID STATE IONICS 176 (39-40) 2899 - 2904 0167-2738 2005/12 [Not refereed][Not invited]
     
    Solid acids such as A1H(2)P(3)O(10)(.)2H(2)O, Zr(HPO(4))(2)(.)H(2)O, arnorphous-AIPO(4), and A1H(3)(PO(4))(2)(.)3H(2)O showed low conductivities of 10(-8)- 10(-7) S cm(-1) at 130 degrees C, whereas mechanical milling for these solid acids was found to improve the conductivities by 2 to 4 orders of magnitude. On the other hand, a large amount of phosphorus was leached out during a durability test after milling. XRD showed the solid acids were transformed to amorphous or crystal-amorphous composites by mechanical milling. (31)P MAS NMR spectra indicated that the intensities of the bands due to Q(3) and Q 4 units decreased and that of the peak due to Q(0) units increased. The increase in conductivity and the decrease of chemical durability of the mechanically milled solid acids are probably caused by the fort-nation Q0 units, i.e., orthophosphoric acid, in the resultant composites due to the disruption of inorganic structures. (c) 2005 Elsevier B.V. All rights reserved.
  • M Tatsumisago, T Tezuka, A Hayashi, K Tadanaga
    SOLID STATE IONICS 176 (39-40) 2909 - 2912 0167-2738 2005/12 [Not refereed][Not invited]
     
    We prepared a new composite material composed of cesium hydrosulfate (CSHSO(4)) and phosphosilicate gel (P(2)O(5)-SiO(2) gel); a high temperature form of the former exhibits exceptionally high proton conductivity at above 144 degrees C without humidification and the latter is one of the high proton conductors working under low humidity in a temperature range tip to around 150 degrees C. High electric conductivities of 10(-5) to 10(-2) Scm(-1) of the composite were observed under dry N(2) atmosphere in a wide temperature range from ambient to 160 degrees C and no steep change in conductivity at around 144 degrees C was observed. In X-ray diffraction patient of CsHSO(4)-(P(2)O(5)-SiO(2) gel) composites, new diffraction peaks were observed and original peaks of CsHSO(4) disappeared. A reaction of CsHSO(4) and orthophosphoric acid (H(3)PO(4)), which is probably formed by the hydrolysis Of P(2)O(5)-SiO(2) gel, would occur to produce a new crystalline phase with high proton conductivity at lower temperatures. (c) 2005 Elsevier B.V. All rights reserved.
  • T Tezuka, K Tadanaga, A Matsuda, A Hayashi, M Tatsumisago
    SOLID STATE IONICS 176 (39-40) 3001 - 3004 0167-2738 2005/12 [Not refereed][Not invited]
     
    Proton conductive inorganic -organic membranes supported by glass paper were prepared from 3-glycidoxypropyltrimethoxysilane, tetraalkoxysilane and orthophosphoric acid. Hybrid membranes with a thickness of 70-80 mu m were obtained by using two types of glass papers. The open circuit voltage of the test cell using the membrane supported by class paper was 0.75 V. A power density of about 80 mW cm(-2) was obtained with a current density of 300 mA cm(-2) at a cell temperature of 130 degrees C under 7% relative humidity. (c) 2005 Elsevier B.V. All rigths reserved.
  • K Tadanaga, H Yoshida, A Matsuda, T Minami, M Tatsumisago
    SOLID STATE IONICS 176 (39-40) 2997 - 2999 0167-2738 2005/12 [Not refereed][Not invited]
     
    Proton conductive inorganic -organic hybrid films, which show high proton conductivity at temperatures higher than 100 degrees C with low humidification, have been prepared from epoxycyclohexylethyltiimethoxysilane (EHTMS), 3-glycidoxypropyltrimethoxysilane (GPTMS) and H(3)PO(4) by the sol-gel method. Self-supporting, flexible films with a thickness of about 150 to 300 pm were obtained. The ionic conductivity of the films increased with an increase in the relative humidity and was about 1 X 10(-2) S cm(-1) under 25% relative humidity at 130 degrees C. For a fuel cell with the hybrid film (P/Si= 1.5) as an electrolyte under H(2) and air at 130 degrees C, 17% relative humidity, the open circuit voltage of the cell was about 2 2 0.9 V and a power of about 40 mW cm(-2) was obtained with current density of 110 mA cm(-2). It was also confirmed that the test cell can operate 2 more than 10 h with a current density of 100 mA cm(-2). (c) 2005 Elsevier B.V. All rights reserved.
  • T Ohtomo, F Mizuno, A Hayashi, K Tadanaga, M Tatsumisago
    SOLID STATE IONICS 176 (31-34) 2349 - 2353 0167-2738 2005/10 [Not refereed][Not invited]
     
    The Li2S-P-S glasses were prepared by mechanical milling from the mixture of Li2S and elemental phosphorus and sulfur. The conductivity of the glasses was 2.0 x 10(-5) S cm(-1) at room temperature. Raman spectroscopy revealed that the glasses mainly consisted of PS43- and Li+ ions, and partially contained homo bonds such as P-P and S-S bonds. Heat treatment of the glasses above the crystallization temperature produced glass-ceramics in which the crystal analogous to thio-LISICON with high conductivity was precipitated. The precipitation of the thio-LISICON analog enhanced the conductivity of the glasses, and the conductivity of the glass-ceramics was 3.9 x 10(-4) S cm(-1) at room temperature. The Li2S-P-S glass-ceramics contained mainly 4 ions with a small amount of S-S bonds, and the amounts of the P-P and S-S homo bonds in the glass-ceramics were diminished by heat treatment than those in the glasses. The local structure of the Li2S-P-S glass-ceramics was similar to that of the Li2S-P2S5 glass-ceramics prepared from Li2S and P2S5 using as raw materials. (c) 2005 Elsevier B.V. All rights reserved.
  • A Hayashi, T Konishi, K Tadanaga, T Minami, M Tatsumisago
    JOURNAL OF POWER SOURCES 146 (1-2) 496 - 500 0378-7753 2005/08 [Not refereed][Not invited]
     
    The 80SnS(center dot)20P(2)S(5) (mol%) amorphous material was prepared by a mechanical milling technique. The obtained material was fine powders with a few micrometers in size. All-solid-state cells with the SnS center dot P2S5 amorphous electrode and the Li2S center dot P2S5 glass-ceramic electrolyte, where a continuous P2S5 sulfide network between both the materials was formed, were fabricated. The cells exhibited high reversible capacity of over 400 mAh g(-1) for 50 cycles at room temperature. The addition of P2S5 as a glass former to SnS improved cell capacity and cyclability, suggesting that P2S5 network played an important role in enhancing the availability of SnS as an electrode material. (c) 2005 Elsevier B.V. All rights reserved.
  • F Mizuno, A Hayashi, K Tadanaga, M Tatsumisago
    JOURNAL OF POWER SOURCES 146 (1-2) 711 - 714 0378-7753 2005/08 [Not refereed][Not invited]
     
    Composite positive electrodes for all-solid-state ][n/LiCoO2 cells with Li2S-P2S5 glass-ceramic electrolytes were designed in order to improve the high rate performances of the cells. The composite electrodes consisted of the active material, the solid electrolyte and carbon conductive additive powders. The cell with vapor grown carbon fiber (VGCF) as a conductive additive was charged and discharged at current densities of over I mA cm(-2), while the cell with acetylene black (AB) did not work as a rechargeable battery. The difference in the cell performances was explained from viewpoints of the morphology of the carbon additives. VGCF formed a more continuous electron conducting path in the composite positive electrode than AB. The cells without conductive additives were charged and discharged by increasing LiCoO2 content in the composite positive electrode. Using a suitable morphology and amount of component powders for composite electrodes is a key to improve rate performances of all-solid-state secondary batteries. (c) 2005 Elsevier B.V All rights reserved.
  • T Ohtomo, F Mizuno, A Hayashi, K Tadanaga, M Tatsumisago
    JOURNAL OF POWER SOURCES 146 (1-2) 715 - 718 0378-7753 2005/08 [Not refereed][Not invited]
     
    The electrical and electrochemical properties of the Li2S-P2S5-P2O5 glass-ceramic electrolytes were investigated. The 80Li(2)S. (20-X)P(2)S(5)(.)xP(2)O(5) (mol%) glass-ceramics were prepared by a mechanical milling and a subsequent heat treatment. The 80Li(2)S(.)19P(2)S(5) (.) 1P(2)O(5) glass-ceramic showed the high lithium ion conductivity of 7.4 x 10(-4) S cm(-1) at room temperature and the low activation energy of 34 U mol(-1) for conduction. The addition of a small amount of P2O5 to the Li2S-P2S5 sulfide system lowered the electronic conductivity and enhanced the electrochemical stability of the glass-ceramic electrolytes. All-solid-state In/LiCoO2 cells with the 80Li(2)S (.) 19P(2)S(5) (.) 1P(2)O(5) glass-ceramic as a solid electrolyte worked as lithium secondary batteries at room temperature. The cells maintained high discharge capacity of about 100 mAh g(-1) for 10 cycles. (c) 2005 Elsevier B.V All rights reserved.
  • T Sasaki, A Matsuda, K Tadanaga, M Tatsumisago
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 113 (1320) 519 - 524 1882-0743 2005/08 [Refereed][Not invited]
     
    UV light irradiation induced structural changes of the cleavage of silicon-carbon bonds and elimination of organic groups in organosilsesquioxane-titania (RSiO3/2-TiO2,R=methyl, ethyl, phenyl and benzyl) hybridfilms due to the photocatalytic effect of TiO2 component. Phenyl and benzyl groups tended to remain in the films after the cleavage of Si-C bonds presumably due to their higher stability of aromatic rings and lager steric effect. The refractive index and dynamic hardness of all the hybrid films increased, and the thickness and contact angle for water decreased by the structural changes induced by the UV light irradiation. On the basis of these changes in film properties, micropatterning was successfully performed on the RSiO3/2-TiO2 hybrid films by UV light irradiation through a photomask. The micropatterns thus obtained should be applicable to a printing plate using the surface energy differences as well as a micro-optical component using the surface profiles and refractive index changes.
  • A Matsuda, T Matoda, K Tadanaga, T Minami, M Tatsumisago, T Kogure
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 88 (6) 1421 - 1426 0002-7820 2005/06 [Not refereed][Not invited]
     
    A longer period of time was necessary to form anatase nanocrystals on silica-titania gel coatings at lower hot water treatment temperature, whereas considerable amounts of anatase nanocrystals were observed even at 38 degrees C after a treatment of 65 h. The coatings pre-heated at 60 degrees C for 1 h and treated with hot water at 55 degrees C for 15 h showed higher photocatalytic activity for methylene blue bleaching than the coatings prepared under the conditions with higher processing temperature close to 100 degrees C. Such a high photocatalytic activity of the coatings obtained through low processing temperatures can be ascribed to a large specific surface area of the coatings and a smaller crystal size of the precipitated anatase.
  • F Mizuno, A Hayashi, K Tadanaga, M Tatsumisago
    ADVANCED MATERIALS 17 (7) 918 - + 0935-9648 2005/04 [Not refereed][Not invited]
     
    Novel sulfide lithium-ion conducting.. materials are synthesized by crystallization of mechanically milled Li2S-P2S5 glasses. High ambient-temperature conductivities (a) compared with other electrolytes (see Figure) and a low conduction activation energy are achieved by the formation of a highly conductive new crystalline phase.
  • A Matsuda, K Kobayashi, T Kogure, M Sakai, K Tadanaga, T Minami, M Tatsumisago
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 113 (1316) 333 - 335 1882-0743 2005/04 [Refereed][Not invited]
     
    Sol-gel derived SiO2-TiO2 coatings on indium tin oxide (ITO)-coated glass substrates were treated with hot water at 90 degrees C under electric field aiming at the control of morphology and crystalline phase of the titania precipitates. The shape of the precipitates on 75SiO(2) center dot 25TiO(2) (mol %) coating at the negative electrode changed from granular to ramiform by applying an electric field to the substrates during the treatment, whereas such changes in the shape of titania nanocrystals with the electric field were not observed at the positive electrode. The granular and ramiform precipitates were identified as anatase (TiO2) and hydrated titania (n(TiO2) center dot mH(2)O), respectively. The ramiform shape of the titania precipitates became significant with increasing the applied voltage, while the coatings gradually dark-colored due to the reduction of Ti4+ to Ti3+.
  • T Tezuka, K Tadanaga, A Matsuda, A Hayashi, M Tatsumisago
    ELECTROCHEMISTRY COMMUNICATIONS 7 (3) 245 - 248 1388-2481 2005/03 [Not refereed][Not invited]
     
    Proton conductive inorganic-organic membranes supported by glass paper were prepared from 3-glycidoxypropyltrimethoxysilane, tetraethoxysilane and orthophosphoric acid. Hybrid membranes with a thickness of 80 mum were obtained by using 40 mum-thick glass papers. Support of the hybrid membrane by the glass paper enables the formation of the membrane with small thickness and high mechanical strength. The open circuit voltage of the test cell using the membrane supported by the glass paper was 0.75 V and a power density of about 85 mW cm(-2) was obtained with current density of 300 mA cm(-2) at cell temperature of 130 degreesC and 7% relative humidity. (C) 2005 Elsevier B.V. All rights reserved.
  • A Matsuda, T Matoda, T Kogure, K Tadanaga, T Minami, M Tatsumisago
    CHEMISTRY OF MATERIALS 17 (4) 749 - 757 0897-4756 2005/02 [Not refereed][Not invited]
     
    Vibrations were found to affect the nanostructure of titania crystallites formed on SiO(2)-TiO(2) gel coatings during hot water treatment. Granular anatase nanocrystals of 30-50 nm in size ere formed on the coatings during hot water treatment without vibration, whereas the shape of the precipitates elongated to be sheetlike by applying a vibration to the substrate during hot water treatment. The sheetlike crystals mainly consisted of nanosheets with a spacing of about 0.6 inn, and were identified as a hydrated titania, m(TiO(2))(.)nH(2)O, with the lepidocrocite-like layered Structure. Titania nanosheets were characterized by a large surface-to-volume ratio, allowing the high photocatalytic reactivity comparable to that of anatase crystals. In addition, the coatings were highly transparent even after the formation of the nanosheets and thermally stable at around 500 degreesC. The hydrated titania nanosheet-precipitated coatings maintained an excellent wettability for water and antifogging properties even after being kept in dark for 2000 It due to their unique physicochemical properties. Processing temperatures for the coatings preparation are lower than 100 degreesC under atmospheric pressure, so that the coatings have a great potential for applications to various substrates including organic polymers with poor heat resistance.
  • N Yamaguchi, K Tadanaga, A Matsuda, T Minami, M Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 33 (1) 117 - 120 0928-0707 2005/01 [Not refereed][Not invited]
     
    Anti-reflective (AR) properties of flowerlike alumina thin films with a small roughness of less than 100 nm have been studied on substrates such as soda-lime silica glass, non-alkali glass, and quartz glass. The highest AR effects were obtained on quartz glass substrate, which has the lowest refractive index of the three substrates. The reflectance of quartz glass substrates coated with flowerlike Al(2)O(3) was less than 0.5% in the wavelength region from 300 to 720 nm.
  • A Matsuda, T Matoda, T Kogure, K Tadanaga, T Minami, M Tatsumisago
    JOURNAL OF MATERIALS RESEARCH 20 (1) 256 - 263 0884-2914 2005/01 [Not refereed][Not invited]
     
    Considerable amounts of anatase nanocrystals were formed on the (100-x)SiO(2)(.)xTiO(2) coatings with x of 16.5 and 25 mol% with boiling water treatment, whereas the formation of anatase nanocrystals was not clearly observed for the coatings with x of 50 and 75 mol%. Despite the lower TiO2 content, the coatings with x of 16.5 and 25 mol% showed higher concentration of Si-O-Ti bonds among the coatings. Thus, the hydrolysis of Si-O-Ti bonds and resultant sites should facilitate the nucleation and Growth of anatase nanocrystals. High transparency, high photocatalytic activity, and superhydrophilicity were demonstrated for the anatase nanocrystals-precipitated coatings.
  • Atsunori Matsuda, Kumpei Kobayashi, Toshihiro Kogure, Mototsugu Sakai, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    Journal of the Ceramic Society of Japan 113 (1316) 333 - 335 0914-5400 2005 [Not refereed][Not invited]
     
    Sol-gel derived SiO2-TiO2 coatings on indium tin oxide (ITO)-coated glass substrates were treated with hot water at 90°C under electric field aiming at the control of morphology and crystalline phase of the titania precipitates. The shape of the precipitates on 75SiO 2· 25TiO2 (mol%) coating at the negative electrode changed from granular to ramiform by applying an electric field to the substrates during the treatment, whereas such changes in the shape of titania nanocrystals with the electric field were not observed at the positive electrode. The granular and ramiform precipitates were identified as anatase (TiO2) and hydrated titania (n(TiO2) ·mH 2O), respectively. The ramiform shape of the titania precipitates became significant with increasing the applied voltage, while the coatings gradually dark-colored due to the reduction of Ti4+ to Ti 3+.
  • Teruyuki Sasaki, Atsunori Matsuda, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Journal of the Ceramic Society of Japan 113 (1320) 519 - 524 0914-5400 2005 [Not refereed][Not invited]
     
    UV light irradiation induced structural changes of the cleavage of silicon-carbon bonds and elimination of organic groups in organosilsesquioxane- titania (RSiO3/2-TiO2, R = methyl, ethyl, phenyl and benzyl) hybrid films due to the photocatalytic effect of TiO2 component. Phenyl and benzyl groups tended to remain in the films after the cleavage of Si-C bonds presumably due to their higher stability of aromatic rings and lager steric effect. The refractive index and dynamic hardness of all the hybrid films increased, and the thickness and contact angle for water decreased by the structural changes induced by the UV light irradiation. On the basis of these changes in film properties, micropatterning was successfully performed on the RSiO3/2-TiO2 hybrid films by UV light irradiation through a photomask. The micropatterns thus obtained should be applicable to a printing plate using the surface energy differences as well as a micro-optical component using the surface profiles and refractive index changes.
  • F Mizuno, A Hayashi, K Tadanaga, M Tatsumisago
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 152 (8) A1499 - A1503 0013-4651 2005 [Not refereed][Not invited]
     
    The effects of conductive additives in composite positive electrodes on charge-discharge behaviors of all-solid-state In/LiCoO2 cells with (LiS)-S-2-P2S5 glass-ceramic electrolytes were investigated. Acetylene black (AB), vapor grown carbon fiber (VGCF), titanium nitride (TiN), and nickel metal (Ni) were used as conductive additives. Carbon materials were more effective to decrease the resistivities of composite positive electrodes compared to TiN and Ni. Under a current density of 64 mu A cm(-2), discharge capacities of about 100 mAh g(-1) were maintained over 50 cycles in the cell with VGCF, while gradual decreases in discharge capacities were observed in the cells with AB, TiN, and Ni. Furthermore, even under a current density over 1 mA cm-2, the cell with VGCF kept larger discharge capacities during 50 cycles than the cell with AB. Since VGCF is composed of submicrometer-ordered fibers, close solid-solid contacts among electrode, electrolyte, and VGCF were achieved. The design of continuous electron conducting paths from a point of view of morphology for conductive additives is important to improve cell performances of all-solid-state lithium secondary batteries. (c) 2005 The Electrochemical Society. [DOI: 10.1149/1.1939633] All rights reserved.
  • F Mizuno, A Hayashi, K Tadanaga, M Tatsumisago
    ELECTROCHEMICAL AND SOLID STATE LETTERS 8 (11) A603 - A606 1099-0062 2005 [Not refereed][Not invited]
     
    A lithium-ion highly conductive new crystal was first precipitated in the Li2S-P2S5 glass-ceramics obtained by crystallization of the glasses. The 70Li(2)S center dot 30P(2)S(5) (mol %) glass-ceramic heated at 360 degrees C showed the highest conductivity of 3.2 X 10(-3) S cm(-1) at room temperature and the lowest activation energy of 12 kJ mol(-1) for conduction. The new crystal was formed by heat-treatment from 240 to 360 degrees C, and the Li4P2S6 crystal was present at 550 degrees C, indicating that the new crystal was precipitated as a metastable phase. The superionic metastable phase is responsible for the high conductivity and low activation energy of the glass-ceramics. (c) 2005 The Electrochemical Society.
  • Akitoshi Hayashi, Takamasa Ohtomo, Fuminori Mizuno, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Electrochimica Acta 50 (2-3) 893 - 897 0013-4686 2004/11/30 [Not refereed][Not invited]
     
    All-solid-state cells, using sulfur-based cathode materials and Li 2S-P2S5 glass-ceramic electrolytes exhibited excellent cycling performance at room temperature. The cathode materials consisting of sulfur and CuS were synthesized by mechanical milling, using a mixture of sulfur and copper crystals with several different molar ratios. The cell performance was influenced by the composition of S/Cu for the cathode materials and the cell with the cathode material of S/Cu = 3 prepared by milling for 15min retained large discharge capacities over 650mA h g-1 for 20 cycles. Sulfur as well as CuS in the cathode materials proved to be utilized as active materials on charge-discharge processes in the all-solid-state batteries. © 2004 Elsevier Ltd. All rights reserved.
  • Fuminori Mizuno, Akitoshi Hayashi, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    Solid State Ionics 175 (1-4) 699 - 702 0167-2738 2004/11/30 [Not refereed][Not invited]
     
    Highly lithium ion conducting Li2S-SiS2-Li 4SiO4 glasses and Li2S-P2S 5 glass ceramics were prepared by using the melt-quenching method and the mechanical milling method, respectively. All-solid-state In/LiCoO 2 cells using the glass and glass ceramic as solid electrolytes were assembled and their cell performances were evaluated at room temperature. Although the cells worked as lithium secondary batteries, they had large irreversible capacities at the 1st cycle. Cyclic voltammetry (CV) suggested that an irreversible anodic reaction occurred only at the 1st cycle in both cells. By using charge-discharge conditions optimized, the solid-state cells with Li2S-SiS2-Li4SiO4 glasses and Li2S-P2S5 glass ceramics respectively kept high discharge capacity around 60 and 100 mA h g-1 over 100 cycles with charge-discharge efficiencies around 100%. © 2004 Elsevier B.V. All rights reserved.
  • Akitoshi Hayashi, Shigenori Kama, Fuminori Mizuno, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    Solid State Ionics 175 (1-4) 683 - 686 0167-2738 2004/11/30 [Not refereed][Not invited]
     
    Glass-ceramic solid electrolytes were prepared by crystallization of the mechanically milled 80Li2S ·20P2S5 glass and their electrical and electrochemical properties were examined. The glass-ceramics exhibited favorable features as a solid electrolyte for lithium secondary batteries such as high ambient temperature conductivity of 7.2×10-4 S cm-1, unity of lithium transport number, wide electrochemical window, and high stability against lithium metal. All-solid-state cells In/80Li2S ·20P2S5 glass-ceramic/LiCoO2 worked as lithium secondary batteries at room temperature and maintained large discharge capacity of about 100 mA h g -1 up to the 200th cycle with the charge-discharge efficiency of 100%. © 2004 Elsevier B.V. All rights reserved.
  • Naoki Nakamoto, Atsunori Matsuda, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    Journal of Power Sources 138 (1-2) 51 - 55 0378-7753 2004/11/15 [Refereed][Not invited]
     
    Fuel cells using a composite sheet composed of phosphosilicate (P 2O5-SiO2, P/Si = 1 in mole ratio) gel powder and polyimide operated up to 150°C under a relatively low water vapor pressure. Maximum power density of the fuel cell increased with increasing operation temperature up to 150°C and increasing humidity. No degradation was observed even after the continuous operation for 10 h at 150°C and 4% relative humidity (RH) under 50mA cm-2. Sieving of the mechanically milled phosphosilicate gel powders to be less than 5μm in size was found to improve the homogeneity and thus the proton conductivity of the resultant composite sheets. The conductivity of the composite sheet containing 75wt.% of the sieved gel powder was 4 × 10-3 S cm-1 at 150°C and 18% RH. Good contact between the composite sheet as an electrolyte and Pt-loaded carbon paper sheets as electrodes in the membrane electrode assembly (MEA) was very important to attain high performance of the fuel cells, which was achieved by the painting of phosphosilicate sol on the surface of the carbon paper and the hot-pressing of the MEA in vacuo. © 2004 Elsevier B.V. All rights reserved.
  • K Tadanaga, H Yoshida, A Matsuda, T Minami, M Tatsumisago
    ELECTROCHIMICA ACTA 50 (2-3) 705 - 708 0013-4686 2004/11 [Not refereed][Not invited]
     
    Proton conductive inorganic-organic hybrid films, which show high proton conductivity at temperatures higher than 100 degreesC with low relative humidity, were prepared from 3-glycidoxypropyltrimethoxysilane (GPTMS), tetramethoxysilane (TMOS) and orthophosphoric acid by the sol-gel method. The relative humidity dependence of the conductivity measurements showed that the ionic conductivity of the films, which increased with an increase in the relative humidity, was about 5 x 10(-2) S cm(-1) under 20% relative humidity (RH) at 130 degreesC. The polarization performances measured for test cells at 130 degreesC showed that the maximum power density increased with an increase in the relative humidity. For a cell with the hybrid film (molar ratio P/Si = 1.5) as an electrolyte under H(2) and air at 130 degreesC, 17% RH, the open circuit voltage of the cell was about 0.88 V and a power of about 50 MW cm(-2) was obtained with current density of 150 mA cm(-2) (C) 2004 Elsevier Ltd. All rights reserved.
  • Akitoshi Hayashi, Takanori Konishi, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    Journal of Non-Crystalline Solids 345-346 478 - 483 0022-3093 2004/10/15 [Not refereed][Not invited]
     
    The glass structure, thermal and electrochemical properties of the SnO-P2O5 glasses, prepared by melt-quenching technique, were examined. The glasses showed relatively low glass transition temperatures of about 250°C and these values were lower than those of the SnO-B 2O3 and SnO-BPO4 glasses. Local structure of the glasses was investigated by Raman and 31P MAS-NMR measurements, suggesting that the number of bridging oxygens decreased whereas the non-bridging oxygen concentration increased with increasing SnO content in the glasses. The electrochemical properties of the glasses as anode materials for lithium secondary batteries were examined using the cells with conventional liquid electrolytes. The cell using the 67SnO · 33P2O 5 (mol%) glass as a working electrode exhibited an excellent cycling performance and retained high charge-discharge capacities over 400mAhg -1 for 20 cycles under a cut-off voltage of 0-0.8 V. © 2004 Published by Elsevier B.V.
  • K Tadanaga, H Yoshida, A Matsuda, T Minami, M Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 31 (1-3) 365 - 368 0928-0707 2004/08 [Not refereed][Not invited]
     
    Proton conductive inorganic- organic hybrid films, which show high proton conductivity at temperatures higher than 100degrees C with low humidification, have been prepared from epoxycyclohexylethyltrimethoxysilane ( EHTMS), 3- glycidoxypropyltrimethoxysilane, and orthophosphoric acid by the sol- gel method. Self- supporting, flexible, and brownish transparent films with a thickness ranging from 150 to 300 mum were obtained. Differential thermal analyses and thermogravimetric measurements revealed that the films were stable up to about 200degrees C. Ionic conductivity of the films increased with an increase in the content of phosphoric acid in the films. The films with a molar ratio of P/ Si = 1.75 retained a high conductivity of about 6 x 10(-4) S cm(-1) even after holding for 150 h under 0.7% relative humidity at 130degrees C. The conductivity of the films increased with an increase in the relative humidity and was about 1 x 10(-2) S cm(-1) under 20% relative humidity at 130degrees C.
  • Kiyoharu Tadanaga, Takayuki Fujii, Atsunori Matsuda, Tsutomu Minami, Masahiro Tatsumisago
    Journal of Sol-Gel Science and Technology 31 (1-3) 299 - 302 0928-0707 2004/08 [Not refereed][Not invited]
     
    Formation process of convexly shaped oxide micropatterns using hydrophobic-hydrophilic patterned surface has been examined, and this technique was applied to several oxide thin films such as SnO2, ZrO 2, TiO2 and A12O3. Hydrophobic-hydrophilic patterned surfaces were prepared on glass substrates by selective UV irradiation through a photomask on double-layered films of a very thin TiO2 gel film as the underlayer and a hydrolyzed fluoroalkyltrimethoxysilane layer as the top layer. Precursor solutions were then spin-coated on the hydrophobichydrophilic patterns, and the coated substrates were dried at room temperature. The micropatterns of oxides were very difficult to be formed on the hydrophobic-hydrophilic patterned surfaces from metal-alkoxides as a precursor solution, but convexly shaped micropatterns were formed on the hydrophilic regions of the pattern when metal chlorides or oxychlorides were used as starting materials. This patterning technique potentially has a wide variety of applications such as fabrication of micro-optical components and finely patterned transparent electrodes.
  • Atsunori Matsuda, Tatsuo Matoda, Toshihiro Kogure, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    Journal of Sol-Gel Science and Technology 31 (1-3) 229 - 233 0928-0707 2004/08 [Refereed][Not invited]
     
    Titania nanosheet-precipitated coatings have been prepared by treating SiO2-TiO2 gel films on glass substrates with hot water at 90°C under vibration. Longitudinal vibrations at about 6 Hz during the treatment enhanced the formation of titania nanosheet. The titania nanosheet consisted of several layers with a spacing of about 0.6 nm and was identified as hydrated titania with a lepidocrocite-type structure. The morphology of the titania nanosheet-precipitated coatings is probably achieved by lowering of the concentration of hydrolyzed titania species at the surface due to rapid water flow driven by the vibrations. The coatings were transparent in the visible range and showed high photocatalytic activity and antifogging property.
  • A. Matsuda, T. Tanaka, K. Tadanaga, T. Minami, M. Tatsumisago
    Journal of Materials Science 39 (3) 903 - 909 0022-2461 2004/02/01 [Refereed][Not invited]
     
    Copolymerized methylsilsesquioxane-benzylsilsesquioxane, (100 - x)MeSiO3/2·xBnSiO3/2 (mol%), microparticles of 0.3-0.4 μm in average diameter have been prepared by the sol-gel method and applied to the formation of thick films on indium tin oxide (ITO)-coated glass substrates by the electrophoretic deposition. The microparticles obtained were considered to be hybrid containing both methyl and benzyl groups from thermal analyses and structural investigations. The microparticles became fusible at x ≥ 80 by a heat treatment. Thick film, ca. 5 μm thick, consisting of electrophoretically deposited pure BnO3/2 microparticles became transparent upon thermal sintering of the particles during heat treatment at temperatures higher than 100°C. On the other hand, the increase in optical transmittance during the heat treatment of the films consisting of 20MeSiO 3/2·80BnSiO3/2 microparticles was as small as about 20% in visible range even after the heat treatment. The smaller increase in transmittance is probably due to the relatively high viscosity of the 20MeSiO3/2·80BnSiO3/2 upon sintering in comparison with pure BnO3/2 for elimination of the voids in the films. © 2004 Kluwer Academic Publishers.
  • K Tadanaga, T Fujii, A Matsuda, T Minami, M Tatsumisago
    CERAMICS INTERNATIONAL 30 (7) 1815 - 1817 0272-8842 2004 [Not refereed][Not invited]
     
    SnO2 micropatterns were prepared by using hydrophobic-hydrophilic patterned surfaces. Hydrophobic-hydrophilic patterned surfaces were prepared by selective UV-irradiation through a photomask on multilayered films of a very thin TiO2 gel layer and a hydrolyzed fluoroalkyltrimethoxysilane layer. SnO2 precursor solution prepared from SnCl2 and ethanol was coated on the hydrophobic-hydrophilic patterned surfaces. Convexly shaped SnO2 patterns were formed on hydrophilic area of the patterned surfaces. Thickness of these patterns was more than 1 mum. This patterning technique must have a wide variety of applications such as fabrication of micro-optical components and micropatterned oxide thin films. (C) 2004 Elsevier Ltd and Techna Group S.r.l. All rights reserved.
  • K. Kobayashi, A. Matsuda, T. Kogure, K. Tadanaga, T. Minami, M. Tatsumisago
    J. Ceram. Soc. Jpn. 112 (5) S1425-S1429  2004 [Not refereed][Not invited]
  • A. Hayashi, T. Konishi, M. Nakai, H. Morimoto, K. Tadanaga, T. Minami, M. Tatsumisago
    J. Ceram. Soc. Jpn. 112 (5) S713-S716  2004 [Not refereed][Not invited]
  • F. Mizuno, T. Ohtomo, A. Hayashi, K. Tadanaga, T. Minami, M. Tatsumisago
    J. Ceram. Soc. Jpn. 112 (5) S709-S712  2004 [Not refereed][Not invited]
  • F Mizuno, A Hayashi, K Tadanaga, T Minami, M Tatsumisago
    JOURNAL OF POWER SOURCES 124 (1) 170 - 173 0378-7753 2003/10 [Not refereed][Not invited]
     
    All-solid-state cells of In/LiNi0.5Mn0.5O2 Using a superionic oxysulfide glass with high conductivity at room temperature of 10(-3) S cm(-1) as a solid electrolyte were fabricated and the cell performance was investigated. Although a large irreversible capacity was observed at the 1st cycle, the solid-state cells worked as lithium secondary batteries and exhibited excellent cycling performance after the 2nd cycle; the cells kept charge-discharge capacities around 70 mAh g(-1) and its efficiency was almost 100%. This is the first case to confirm that all-solid-state cells using manganese-based layer-structured cathode materials work as lithium secondary batteries. (C) 2003 Elsevier B.V. All rights reserved.
  • K Tadanaga, H Yoshida, A Matsuda, T Minami, M Tatsumisago
    ELECTROCHEMISTRY COMMUNICATIONS 5 (8) 644 - 646 1388-2481 2003/08 [Not refereed][Not invited]
     
    Proton conductive in organic-organic hybrid films were prepared from 3-glycidoxypropyltrimethoxysilane, tetramethoxysilane and orthophosphoric acid by the sol-gel method, and the polarization performances were measured at 130 degreesC for test cells using the hybrid film and the composite electrode with precursor sol of the hybrid film and Pt-loaded carbon sheet. For a cell with the hybrid film (P/Si = 1.5) as an electrolyte under H-2 and air at 130 degreesC, 17% relative humidity, the open circuit voltage of the cell was about 0.88 V and a power of about 50 mW cm(-2) was obtained with current density of 150 mA cm(-2). (C) 2003 Elsevier Science B.V. All rights reserved.
  • A Hayashi, T Ohtomo, F Mizuno, K Tadanaga, M Tatsumisago
    ELECTROCHEMISTRY COMMUNICATIONS 5 (8) 701 - 705 1388-2481 2003/08 [Not refereed][Not invited]
     
    All-solid-state cells using sulfur-based cathode materials and Li2S-P2S5 glass-ceramic electrolytes were successfully prepared and exhibited excellent cycling performance at room temperature. The cathode materials consisting of sulfur and CuS were synthesized by mechanical milling using sulfur and copper crystals as starting materials. The cell performance was influenced by the milling time for the cathode materials and the cell with cathode materials obtained by milling for 15 min retained large capacities over 650 mA h g(-1) for 20 cycles. Sulfur as well as CuS in cathode materials proved to be utilized as active materials on charge-discharge processes in the all-solid-state Li/S cells. (C) 2003 Published by Elsevier B.V.
  • A Matsuda, T Matoda, T Kogure, K Tadanaga, T Minami, M Tatsumisago
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 27 (1) 61 - 69 0928-0707 2003/05 [Not refereed][Not invited]
     
    Anatase nanocrystals-precipitated silica coatings were formed on plastic substrates such as poly(ethylene terephtalate) (PET), acrylic resin (AC) and polycarbonate (PC) from silica-titania gel coatings with and without addition of poly(ethylene glycol) (PEG) by hot water treatment. The maximum thickness of the coatings which can be formed without cracking or peeling-off was 100 to 200 nm for PET and PC substrates, whereas it was less than 50 nm for AC substrates. After a hot water treatment at 90degreesC for 120 min, the size of the anatase nanocrystals increased to be 30 and 50 nm for the coatings obtained with and without PEG, respectively. Anatase nanocrystals were formed throughout the whole of the coatings obtained with PEG and were formed only on the surface of the coatings obtained without PEG. Both coatings obtained with and without PEG were highly transparent. The plastic substrates with coatings obtained without PEG showed good weathering resistance owing to the protective effects of the residual silica under-layer. The coatings obtained with PEG showed higher photocatalytic activities than those obtained without PEG due to smaller size and higher dispersion of anatase nanocrystals in the coatings.
  • K Tadanaga, H Yoshida, A Matsuda, T Minami, M Tatsumisago
    CHEMISTRY OF MATERIALS 15 (9) 1910 - 1912 0897-4756 2003/05 [Not refereed][Not invited]
     
    Proton-conductive inorganic-organic hybrid films, which can be used as an electrolyte for polymer electrolyte-type fuel cells at temperatures higher than 100 degreesC with low humidification, have been prepared from 3-glycidoxypropyltrimethoxysilane, tetramethoxysilane, and orthophosphoric acid by the sol-gel method. Self-supporting, flexible, and brownish transparent films with a thickness of about 200 to 300 mum were obtained. Differential thermal analysis and thermogravimetric measurements revealed that the films were stable up to about 200 degreesC. The ionic conductivity of the films increased with an increase in the content of phosphoric acid in the films. The films with a molar ratio of P/Si = 1.5 kept a high conductivity of about 7 x 10(-4) S cm(-1\) even after holding for 6 h under 0.7% relative humidity at 130 degreesC.
  • K Tadanaga, K Kitamuro, A Matsuda, T Minami
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 26 (1-3) 705 - 708 0928-0707 2003/01 [Not refereed][Not invited]
     
    Transparent, superhydrophobic coating films have been prepared on polymer substrates at low temperatures through the sol-gel method. Al2O3 gel films were prepared on poly( ethylene terephthalate) substrates from Al(O-sec-C4H9)(3) chemically modified with ethyl acetoacetate. A small roughness of about 20-50 nm was found to form on the surface of the Al2O3 gel films dried at room temperature and then immersed in hot water at 60degreesC. The electron diffraction measurements have shown that this roughened surface consists of pseudoboehmite nanocrystals. The coating of hydrolyzed fluoroalkyltrimethoxysilane on the Al2O3 gel films with the small roughness produced transparent, superhydrophobic films with contact angle for water larger than 150degrees.
  • K Tadanaga, K Ueyama, T Sueki, A Matsuda, T Minami
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 26 (1-3) 431 - 434 0928-0707 2003/01 [Not refereed][Not invited]
     
    Inorganic-organic hybrid coating films were prepared from various trifunctional silicon alkoxides with a C=C double bond in their organic components, such as vinyltriethoxysilane (VTES), allyltriethoxysilane (ATES) or trimethoxysilylpropylmethacrylate (TMSPM), and zirconium n-tetrapropoxide modified with methacrylic acid. UV light from a high-pressure mercury lamp was irradiated through a photomask on the hybrid films, and this irradiation increased refractive index and microhardness of the films and decreased solubility of the films in alcohol or alkaline solution. IR spectra of the coating films have shown that C=C bonds in these trifunctional silicon alkoxides were polymerized with the UV irradiation. Patterns with a width of about 10 mum and thickness of about 5-15 mum were formed by the etching of unirradiated region of the films. Since VTES and ATES have a shorter organic chain than TMSPM, the hybrid films prepared from VTES or ATES are expected to show small optical loss in the near-infrared region due to C-H bonds in their use as waveguides.
  • Kiyoharu TADANAGA, Fuminori MIZUNO, Akitoshi HAYASHI, Tsutomu MINAMI, Masahiro TATSUMISAGO
    Electrochemistry 71 [12], 1192-1195 (12) 1192 - 1195 1344-3542 2003 [Refereed][Not invited]
  • A Matsuda, Y Nono, K Tadanaga, T Minami, M Tatsumisago
    SOLID STATE IONICS 162 253 - 259 0167-2738 2003 [Not refereed][Not invited]
     
    Phosphosilicate (P2O5-SiO2) gels with an addition of Al2O3 or B2O3 as a third component have been prepared by the sol-gel method aiming at the improvement in chemical durability of the gels. The presence of strongly interacted water with gel matrices was confirmed for all the gels from an endothermic peak with weight loss at around 230 degreesC in thermal analyses. The addition of Al2O3 or B2O3 suppressed the formation of Si5O(PO4)(6) in phosphosilicate gels during heat treatment and Al2O3 remarkably improved the chemical durability of the resultant gels after a heat treatment at 300 degreesC. Al2O3-added gels (P/Si/ Al = 1:0.9:0.1 molar ratio) showed conductivities of about 10(-4) Scm(-1) at 130 degreesC and 0.7% R.H. after a pre-treatment at 30 degreesC and 60% R.H. for 3 h, whereas pure phosphosilicate gels (P/Si = 1: 1) and B2O3-added gels (P/Si/B = 1:0.9:0.1 molar ratio) showed higher conductivities of about 10(-2) Scm(-1) under the same conditions. The lower conductivity of the Al2O3-added gel was ascribed to the smaller amounts of H3PO4 formed by hydrolysis Of Si5O(PO4)(6) in the gels during the pre-treatment. (C) 2003 Elsevier B.V. All rights reserved.
  • A Matsuda, N Nakamoto, K Tadanaga, T Minami, M Tatsumisago
    SOLID STATE IONICS 162 247 - 252 0167-2738 2003 [Not refereed][Not invited]
     
    Thermally stable proton-conducting composite sheets of 50-100 mum thick have been prepared from phosphosilicate gel (P/ Si = 1 molar ratio) powders and polyimide precursor. The proton conductivity of the composite sheet increased with an increase in the phosphosilicate gel content. The composite sheet containing 70 wt.% of the gel showed a tensile strength of about 170 N cm(-2) at 150 degreesC and a conductivity of 2 x 10(-4) S cm(-1) at 150 degreesC and 0.4% relative humidity (RH). The open circuit potential of the test cell using the composite sheet as an electrolyte was about 0.9 V at 30 degreesC and 60% RH, and the power density was maximized to be about 30 mW cm(-2) at around 90 mA cm(-2). (C) 2003 Elsevier B.V All rights reserved.
  • Fuminori Mizuno, Shigenori Hama, Akitoshi Hayashi, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago
    Chemistry Letters (12) 1244 - 1245 0366-7022 2002/12/05 [Not refereed][Not invited]
     
    All solid-state cells of In/LiCoO2 using the 80Li2S·20P2S5 (mol%) glass-ceramics with high ambient temperature conductivity of about 10-3 S cm-1 as a solid electrolyte were fabricated, and the cell performance was investigated. Although an irreversible capacity was observed at the 1st cycle, the solid-state cell exhibited excellent cycling performances with the reversible charge-discharge capacities of about 100 mAh g-1 even after 200 cycles.
  • Atsunori Matsuda, Takao Kanzaki, Kiyoharu Tadanaga, Toshiro Kogure, Masahiro Tatsumisago, Tsutomu Minami
    Journal of the Electrochemical Society 149 (8) E292 - E297 0013-4651 2002/08 [Not refereed][Not invited]
     
    Pore structure and proton conductivities of several types of porous silica gels impregnated with H2SO4 have been studied. The amounts of impregnated H2SO4 increased with an increase in the pore volume of the silica gels, and with an increase in the concentration of H2SO4 used for the impregnation. The surfactant-templated mesoporous silica gels, which were impregnated with 5 M H2SO4, showed high conductivities in the order of 10-1 S cm-1 in a range from 40 to 80°C and 6 RH. Regularly ordered cylindrical pores with smaller pore diameter in the mesoporous silica gel were found to permit the retention of physisorbed water at high temperatures and thus high conductivities at temperatures around 100°C.
  • A Matsuda, T Sasaki, K Tadanaga, M Tatsumisago, T Minami
    CHEMISTRY OF MATERIALS 14 (6) 2693 - 2700 0897-4756 2002/06 [Not refereed][Not invited]
     
    Refractive index of ethylsilsesquioxane-titania hybrid films increased from 1.50 to 1.55 accompanied by a decrease in film thickness by about 30% after UV light irradiation. The contact angle for water of the films decreased from 95degrees to about 45degrees and the dynamic hardness increased with UV irradiation. These changes in physical and chemical properties of the films with UV irradiation were caused by the cleavage of silicon-carbon bonds and elimination of ethyl groups in the films due to the photocatalytic effect of the titania component. Micropatterning was successfully performed on the films coated on the substrates by UV irradiation through a photomask.
  • K Tadanaga, K Imai, M Tatsumisago, T Minami
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 149 (6) A773 - A777 0013-4651 2002/06 [Not refereed][Not invited]
     
    AgI-ZrO2 and AgI-SiO2 composites were prepared using sol-gel derived aerogels. The conductivity at room temperature showed a maximum for the composition of 0.4AgI.0.6ZrO(2) or 0.4AgI.0.6SiO(2) and was 3.3 x 10(23) S cm(-1) for the composite using ZrO2 aerogels and 1.2 x 10(24) S cm(-1) for the composite using SiO2 aerogels. The diffusion of AgI into the micropores of the aerogel was observed for the ZrO2 system, suggesting that the diffusion caused a decrease of the crystallinity of AgI and the formation of a high conductive phase of AgI at the AgI-ZrO2 interface. In the SiO2-containing system, however, the diffusion was not observed and, hence, the conductivity was an order of magnitude lower than that of the ZrO2-based system. (C) 2002 The Electrochemical Society.
  • A Matsuda, T Kanzaki, K Tadanaga, M Tatsumisago, T Minami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 110 (2) 131 - 134 1882-0743 2002/02 [Refereed][Not invited]
     
    Phosphosilicate (P2O5-SiO2) gels with a P/Si molar ratio of 1.0 heat-treated at 150degreesC were found to retain a high conductivity of 1.5 x 10(-2) S . cm(-1) even after holding at a temperature of 130degreesC at a relative humidity of 0.7% for about 400 min. On the other hand, the conductivity of the porous silica gels impregnated with 5 M H3PO4 largely decreased from 1 x 10(-2) to 6 x 10(-6) S . cm(-1) during holding under the same conditions for about 400 min. The difference in the changes of conductivities between phosphosilicate gels and H3PO4-impregnated porous silica gels with holding time indicates that the former can retain larger amounts of adsorbed water at MOT than the latter. Condensed structural units with Si-O-P-OH groups in the phosphosilicate gels are expected to enhance the retention of the adsorbed water in the gels and improve the proton conductivity even at relatively high temperatures and low humidity conditions.
  • Atsunori Matsuda, Takao Kanzaki, Kiyoharu Tadanaga, Masahiro Tatsumisago, Tsutomu Minami
    Journal of the Ceramic Society of Japan 110 (1278) 131 - 134 0914-5400 2002 [Not refereed][Not invited]
     
    Phosphosilicate (P2O5-SiO2) gels with a P/Si molar ratio of 1.0 heat-treated at 150°C were found to retain a high conductivity of 1.5 × 10-2 S·cm-1 even after holding at a temperature of 130°C at a relative humidity of 0.7% for about 400 min. On the other hand, the conductivity of the porous silica gels impregnated with 5 M H3PO4 largely decreased from 1 × 10-2 to 6 × 10-6 S·cm-1 during holding under the same conditions for about 400 min. The difference in the changes of conductivities between phosphosilicate gels and H 3PO4-impregnated porous silica gels with holding time indicates that the former can retain larger amounts of adsorbed water at 130°C than the latter. Condensed structural units with Si-O-P-OH groups in the phosphosilicate gels are expected to enhance the retention of the adsorbed water in the gels and improve the proton conductivity even at relatively high temperatures and low humidity conditions.
  • Proton Conductivities of Sol-Gel Derived Phosphosilicate Gels in Medium Temperature Range with Low Humidity
    A. Matsuda, T. Kanzaki, K. Tadanaga, M. Tatsumisago, T. Minami
    Solid State Ionics 154-155 687 - 692 2002 [Refereed][Not invited]
  • K. Tadanaga, H. Yoshida, A. Matsuda, T. Minami, M. Tatsumisago
    Electrochemistry 電気化学会 70 (12) 998 - 1000 1344-3542 2002 [Not refereed][Not invited]
  • Formation of Convexly Shaped Silica Micropatterns on Sol-Gel Derived Films Using a Difference in Surface Free Energy
    K. Tadanaga, J. Morinaga, T. Fujii, A. Matsuda, T. Minami
    Glass Technol. 43C 275 - 277 2002 [Refereed][Not invited]
  • A Matsuda, K Tadanaga, T Minami, M Tatsumisago
    ELECTROPHORETIC DEPOSITION: FUNDAMENTALS AND APPLICATIONS, PROCEEDINGS 2002 (21) 287 - 294 2002 [Refereed][Not invited]
     
    Transparent, inorganic-organic thick films of a few micrometers in thickness have been prepared on glass substrates coated with indium tin oxide (ITO) by constant-voltage electrophoretic sol-gel deposition method using polysilsesquioxane particles such as polyphenylsilsesquioxane (PhSiO3/2) and polybenzylsilsesquioxane (BnSiO3/2). The films composed of aggregates of PhSiO3/2 and BnSiO3/2 particles became transparent with morphological changes from aggregates of particles to a monolithic, continuous layer with high refractive indices after heat treatment. The increase in optical transmittance was caused by thermal sintering of the particles in the films. Thermal sintering of PhSiO3/2 particles at 140 degreesC and that of BnSiO3/2 particles at 50 degreesC reduced the interfaces and openings among the particles and decreased light scattering of the films to form transparent films. The thermal sintering of the PhSiO3/2 and BnSiO3/2 particles was caused by the decrease of viscosity at temperatures higher than the glass transition temperatures.
  • A Matsuda, Y Nono, T Kanzaki, K Tadanaga, M Tatsumisago, T Minami
    SOLID STATE IONICS 145 (1-4) 135 - 140 0167-2738 2001/12 [Not refereed][Not invited]
     
    Highly proton-conductive acid-impregnated mesoporous silica gels have been prepared using alkyltrimethylammonium. chlorides with different alkyl chain length as a template and several kinds of protonic acids such as HClO4, H2SO4 and H3PO4 as a proton donor. The specific surface area and pore volume of the mesoporous silica gels increased with an increase in the number of carbon atoms in the alkyl chain. The electric conductivities of all the acid-impregnated mesoporous silica gels also tended to increase with increasing the number of carbon atoms in the alkyl chain in the surfactant. This phenomenon can be ascribed to an increase in the amounts of impregnated acid due to the enlarged pore volume in the mesoporous silica gels. It was found that HClO4 and H2SO4 more effectively enhanced the proton conductivity of the resultant acid-impregnated silica gels than H3PO4. The conductivities of the HClO4- and H2SO4-impregnated mesoporous silica gels obtained were higher than 10(-1) S cm(-1) under 60% relative humidity at 85 degreesC. (C) 2001 Elsevier Science B.V. All rights reserved.
  • A Matsuda, T Kanzaki, K Tadanaga, M Tatsumisago, T Minami
    ELECTROCHIMICA ACTA 47 (6) 939 - 944 0013-4686 2001/12 [Not refereed][Not invited]
     
    Proton conductivities of phosphosilicate dry gets derived from tetraethoxysilane (TEOS) and H3PO4 increased with an increase in the P/Si mole ratio from 0.5 to 1.0 and tended to level off at 1.0-1.5. The dry gel powder pellets with a P/Si mole ratio of 1.0 showed a high conductivity of 1 x 10(-2) S cm(-1) even after keeping under the atmosphere at 150 degreesC and 0.4% relative humidity (R.H.) for 400 min, Si5O(PO4)(6) crystals and highly condensed phosphates, both of which were formed in the gels during the heat treatment process at 150 degreesC, were readily hydrolyzed. The hydrolyzed species like isolated phosphoric acid and a structural unit with Si O-P OH groups permits the gels to retain high proton conductivity even at temperatures in the medium range with low humidity owing to the good affinity with adsorbed water. (C) 2001 Elsevier Science Ltd. All rights reserved.
  • Kiyoharu Tadanaga, Junichi Morinaga, Tsutomu Minami
    Journal of Sol-Gel Science and Technology 19 (1-3) 211 - 214 0928-0707 2000/12 [Not refereed][Invited]
     
    We have prepared superhydrophobic surfaces which become superhydrophilic by heat-treatment at 500°C or irradiation of UV-light. When hydrolyzed fluoroalkyltrimethoxysilane (FAS) was coated on Al2O3 gel film with a roughness of 20 to 50 nm, the films showed superhydrophobicity and high transparency the contact angle for water of the film was 165° and the transmittance for the visible light was higher than 92%. When the FAS-coated thin films were heat-treated at temperatures higher than 500°C, the films became superhydrophilic the contact angle for water on the films was smaller than 5°. Thin films of amorphous TiO2 or anatase TiO2 were coated between Al2O3 gel and FAS layer, and the contact angle for water was also about 160°. UV irradiation using high-pressure mercury lamp on these films resulted in the contact angle to be smaller than 5°. When UV light was irradiated through a photomask, superhydrophobic-superhydrophilic micropatterns applicable as a stamper for printing or a substrate of micro-optical components were successfully obtained on the films.
  • H Kitahata, K Tadanaga, T Minami, N Fujimura, T Ito
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 19 (1-3) 589 - 593 0928-0707 2000/12 [Not refereed][Not invited]
     
    Hexagonal YMnO3 has a ferroelectric property with an optimal remanent polarization along the c-axis. The c-axis oriented YMnO3 thin films with a small leakage current were prepared by the sol-gel dipping method. The c-axis orientation of the films was promoted by the addition of diethanolamine to the Mn precursor solution. A heat treatment with multiple steps led to a dense film structure with fine grains. The dense structure resulted in the decrease of the leakage current. Furthermore, when the films were heat-treated in a vacuum, the leakage current became considerably small and the ferroelectricity of the YMnO3 thin films was observed even at room temperature.
  • K Tadanaga, B Ellis, AB Seddon
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 19 (1-3) 687 - 690 0928-0707 2000/12 [Not refereed][Not invited]
     
    Ormosil dipped thin films and cast films were prepared using tetramethoxysilane and trimethoxysilylpropylmethacrylate (TMSPM). Structural changes during thermally induced polymerisation of the organic groups were investigated using near- and mid-infrared (IR) spectroscopy. IR spectra of the ormosil dipped thin films, dried at 60 degreesC, have shown that further heat-treatment of the films at 160 degreesC leads to the free radical polymerisation of C=C bonds in TMSPM. In the mid-infrared spectra, the intensity of the band at around 3500 cm(-1), due to O-H bonds, increased with the progress of polymerisation of vinyl groups. Near-infrared spectra of the cast films showed that this increase in intensity of the O-H band is due to the increase of monomeric water molecules hydrogen bonded to silanols. We suggest that optical loss measurements must be made in a dry atmosphere or, with a cover coating to protect the ormosil from adsorption of water, to reduce this source of optical loss for waveguides based on TMSPM.
  • K Tadanaga, T Owan, J Morinaga, S Urbanek, T Minami
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 19 (1-3) 791 - 794 0928-0707 2000/12 [Not refereed][Not invited]
     
    Finely patterned transparent, conductive SnO2 thin films have been prepared. UV-light from a high-pressure mercury lamp was irradiated through a mask on the precursor films prepared from SnCl2 with acetyl acetone in the ambient atmosphere, and this irradiation led to the change of solubility of the films in alkaline solution. Patterns with a width of about 3 to 50 mum and thickness of about 0.1 mum were formed with a pitch of about 2 to 20 mum. The resistivity of the films heat-treated at 500 degreesC after UV irradiation was about 1 x 10(-2) Omega cm, which was almost the same resisitivity for the films heat-treated at 500 degreesC without UV irradiation.
  • K Tadanaga, K Imai, M Tatsumisago, T Minami
    JOURNAL OF THE ELECTROCHEMICAL SOCIETY 147 (11) 4061 - 4064 0013-4651 2000/11 [Not refereed][Not invited]
     
    AgI-Al2O3 composites were prepared using sol-gel-derived Al2O3 aerogels and xerogels. The addition of Al2O3 aerogel or xerogel to AgI enhanced the ionic conductivity. The conductivity at room temperature showed a maximum at the composition 0.4AgI .0.6Al(2)O(3) in both aerogel-containing and xerogel-containing composites and was 2.8 X 10(-3) S cm(-1) for the aerogel composite. The conductivity of aerogel-containing composites was larger than that of xerogel-containing composites for all compositions, suggesting that the pore size distribution of aerogels was more effective than that of xerogels for enhancing the ionic conductivity. (C) 2000 The Electrochemical Society. S0013-4651(00)04-072-6. All rights reserved.
  • K Tadanaga, K Kitamuro, J Morinaga, Y Kotani, A Matsuda, T Minami
    CHEMISTRY LETTERS (8) 864 - 865 0366-7022 2000/08 [Not refereed][Not invited]
     
    Al2O3 gel films were prepared on poly(ethylene terephthalate) substrates from Al(O-sec-C4H9)(3) chemically modified with ethyl acetoacetate. A small roughness of about 20-50 nm was found to form on the Al2O3 gel films dried at room temperature and then immersed in hot water at 60 degrees C. When hydrolyzed fluoroalkyltrimethoxysilane was coated on the Al2O3 films, transparent thin films with contact angle for water to be more than 150 degrees were obtained.
  • K Tadanaga, T Minami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 108 (4) 420 - 423 1882-0743 2000/04 [Refereed][Not invited]
     
    Precursor structure of chemically modified Al(O-sec-Bu)(3) with ethyl acetoacetate or diethanolamine, dissolved in diethylene glycol (DEG), ethylene glycol monoethyl ether (EGE), and sec-butyl alcohol (sec-BuOH), was investigated using Al-27 NMR. Al-27 NMR spectra revealed that the reaction of DEG or EGE with Al(O-sec-Bu)(3) led to the formation of six-coordinated structural units, The precursor structure of Al(O-sec-Bu)(3) modified with ethyl acetoacetate in EGE, which consisted of six- and five-coordinated structural units, was almost the same as that in DEG, but different from that in sec-BuOH, where four-coordinated structural units were also observed, In Al(O-sec-Bu)(3) modified with diethanolamine, five- and six-coordinated structural units were present in all the solvents used in this study and the effect of solvents on the coordination state was very small.
  • K Tadanaga, J Morinaga, A Matsuda, T Minami
    CHEMISTRY OF MATERIALS 12 (3) 590 - + 0897-4756 2000/03 [Not refereed][Not invited]
     
    A never route to form superhydrophobic-superhydrophilic micropatterned coating film has been developed. UV light was irradiated on the superhyrdrophobic coating film which consists of three layers, a flowerlike Al2O3 gel film, a very thin TiO2 gel layer, and a FAS layer, to cleave the fluoroalkyl chain in FAS selectively, and well-defined superhydrophobic and superhydrophilic regions were formed.
  • K Tadanaga, B Ellis, AB Seddon
    SOL-GEL OPTICS V 3943 228 - 235 0277-786X 2000 [Not refereed][Not invited]
     
    Structural changes during thermally induced polymerisation of the dipped thin films prepared from TMSPM, zirconium n-tetrapropoxide and methacrylic acid were investigated using near- and mid-infrared (IR) spectroscopy. In the mid-infrared spectra, the intensity of the band due to C=C was decreased by the heat-treatment at 160 degrees C. The intensity of the band due to C=O at around 1720 cm(-1) was also decreased, and that of a band at around 1740 cm(-1) which is assigned to an ester carbonyl C=O in the polymerised methacrylate, was increased. In the near-infrared spectra, the intensities of a band due to the first overtone of fundamental nu(as)(CH2=) and a combination band of nu(as)(CH2=) and nu(C=C) were largely decreased with the heat-treatment at 160 degrees C. These spectral changes show that heat-treatment of the films at 160 degrees C leads to depletion of C=C bonds, indicating that polymerisation has occurred of TMSPM and methacrylic acid. However, in the mid-infrared spectra, the intensity of the band at around 3500 cm(-1) due to O-H bonds, increased with the progress of polymerisation of vinyl groups. Near-infrared spectra of the dipped thin films showed that this increase in intensity of the O-H band is due to the increase of monomeric water molecules hydrogen bonded to silanols. This indicates that polymerised samples are more hydrophilic than unpolymerised ones. The refractive index of the dipped films, measured with a prism coupling method, increased from 1.508 to 1.516 with the polymerisation for composition Zr/(Zr + Si) of 0.2.
  • 忠永 清治, 南 努
    J. Ceram. Soc. Jpn. 108 (1256) 420 - 423 0914-5400 2000 [Not refereed][Not invited]
  • H Kitahata, K Tadanaga, T Minami, N Fujimura, T Ito
    FERROELECTRIC THIN FILMS VIII 596 481 - 486 0272-9172 2000 [Not refereed][Not invited]
     
    The preparation conditions of YMnO3 thin films by the sol-gel method using yttrium alkoxide were optimized to decrease the leakage current of the films. The leakage current of the films was decreased due to the dense microstructure of the films. Moreover, the heat treatment in hydrogen atmosphere and the zirconium doping resulted in a further decrease of the leakage current The heat treatment in hydrogen atmosphere and the zirconium doping were effective in the decrease of carriers originating in the valence fluctuation of the Mn ions in YMnO3.
  • Shogo Nishiwaki, Kiyoharu Tadanaga, Masahiro Tatsumisago, Tsutomu Minami
    Journal of the American Ceramic Society 83 (12) 3004 - 3008 0002-7820 2000 [Refereed][Not invited]
     
    Surfactant-templated mesoporous silica gel that was impregnated with various protonic acids has been prepared, and we propose this material as a new type of proton conductor. The conductivity of the mesoporous silica gel that was impregnated with 5.0M H2SO4 was approx. 1 × 10-4 S/cm at room temperature in a dry nitrogen-gas atmosphere after drying in vacuo at room temperature this value was four orders of magnitude greater than that of silica gel that was prepared via the conventional sol-gel method and impregnated with H2SO4. The amount of impregnated H2SO4 in the mesoporous silica gel was approx. 2.5 times larger than that of impregnated H2SO4 in the conventional silica gel. The H2O molecules in the mesoporous silica gel that was impregnated with H2SO4 remained in the pores of the gel, even after drying in vacuo at room temperature.
  • H Kitahata, K Tadanaga, T Minami, N Fujimura, T Ito
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 1-REGULAR PAPERS SHORT NOTES & REVIEW PAPERS 38 (9B) 5448 - 5451 0021-4922 1999/09 [Not refereed][Not invited]
     
    We have succeeded in lowering the crystallization temperature of sol-gel derived YMnO3 thin films to 500 degrees C by using yttrium alkoxide as a starting material. The X-ray diffraction measurements indicated that the films heat treated at temperatures above 500 degrees C had a single phase of hexagonal YMnO3. The crystallization temperature of the YMnO3 thin film prepared from yttrium alkoxide was lower by at least 300 degrees C than that of film prepared from yttrium acetate. The film prepared from the alkoxide and heal treated at 700 degrees C for 3 min had a high crystallinity with c-axis preferred orientation, and ferroelectricity was observed in the film. The formation temperature of the ferroelectric YMnO3 thin film prepared from yttrium alkoxide was lower by at least 100 degrees C than that of film prepared from yttrium acetate.
  • H Kitahata, K Tadanaga, T Minami, N Fujimura, T Ito
    APPLIED PHYSICS LETTERS 75 (5) 719 - 721 0003-6951 1999/08 [Not refereed][Not invited]
     
    We have observed the ferroelectricity at room temperature in YMnO3 thin films prepared via solution. Precursor films of YMnO3 on Pt/sapphire or Y2O3/Si substrates were heat treated in vacuum or in air for controlling the crystallinity. X-ray diffraction measurements indicated that each film was a single phase of hexagonal YMnO3. While the film heat treated in air indicated an insufficient crystallinity, the film heat treated in vacuum showed a high crystallinity with a c-axis preferred orientation. The leakage current of the film heat treated in vacuum was at least three orders of magnitude lower than that heat treated in air. The ferroelectricity of the film heat treated in vacuum was confirmed in the capacitance-voltage measurement at room temperature due to its high crystallinity with the c-axis preferred orientation and the small leakage current. (C) 1999 American Institute of Physics. [S0003-6951(99)04131-5].
  • A Hayashi, R Araki, K Tadanaga, M Tatsumisago, T Minami
    PHYSICS AND CHEMISTRY OF GLASSES 40 (3) 140 - 145 0031-9090 1999/06 [Not refereed][Not invited]
     
    Glass structure of oxysulphide glasses of composition (1-y) [xLi(2)S. (100-x)SiS2].y[xLi(2)O.(100-x)P2O5] (50 less than or equal to x less than or equal to 65; y=0.05, 0.20) was systematically investigated using Si-29 and P-31 MAS-NMR measurements by changing x, the total lithium ion concentration, and also by changing y, the amount of oxide Li2O-P2O5 added to the sulphide Li2S-SiS2. fn the case of changing x with a constant y=0.05 the amounts of SiOnS4-n (n=1,2,3) tetrahedral units were maximised and those of SiS4 tetrahedral units were minimised in the glass with x=55. PS4 and POS3 tetrahedral units were mainly present in the range 50 less than or equal to x less than or equal to 58. However; the amounts of PO2S2, PO3S and PO4 tetrahedral units increased with an increase of x in the range 60 less than or equal to x less than or equal to 65. In the case of changing y with a constant x=60 the fraction of SiS4, PS4 and POS3 units decreased with an increase of y from 0.05 to 0.20.
  • A Hayashi, K Tadanaga, M Tatsumisago, T Minami, Y Miura
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 107 (6) 510 - 516 1882-0743 1999/06 [Refereed][Not invited]
     
    The structural change of the (100 - x) (0.6Li(2)S . 0.4SiS(2)). xLi(3)PO(4) oxysulfide glasses during crystallization was analyzed by means of solid-state nuclear magnetic resonance (NMR) and X-ray photoelectron spectroscopy (XPS). The unique tetrahedral units of SiOnS4-n (n = 1, 2, 3) and POnS4-n (n = 1, 2, 3) present in the glass samples vanished and the SiS4, SiO4, PS4 and PO4 units increased with proceeding of the crystallization process. Nonbridging sulfur and oxygen atoms decreased while bridging oxygens and S2- increased with proceeding of the crystallization process. Large structural difference between the glass and the corresponding crystallized sample explained the high stability against crystallization found in the oxysulfide glass with the composition of x = 5.
  • K Azuta, K Tadanaga, T Minami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 107 (3) 293 - 296 1882-0743 1999/03 [Refereed][Not invited]
     
    Silica thin films containing organic polymers, such as poly(vinyl alcohol), poly(vinylpyrrolidone) or poly(vinyl acetate), were prepared on PET substrates by the sol-gel method. Poly(vinyl alcohol) was found to be most effective to suppress the water permeability of PET substrates coated with the organic-inorganic composite films among the three. Under the optimal condition, the water permeability coefficient was about 40% of that of PET substrates. The oxygen permeability coefficient was decreased with an increase in the poly(vinyl alcohol) content in the composites and was about 10% of that of PET substrates when a large amount of poly(vinyl alcohol) was included in the composites.
  • AZUTA K, TADANAGA K, MINAMI T
    J. Ceram. Soc. Jpn. 107 (1243) 293 - 296 0914-5400 1999 [Not refereed][Not invited]
  • HAYASHI A, TADANAGA K, TATSUMISAGO M, MINAMI T, MIURA Y
    J. Ceram. Soc. Jpn. 107 (1246) 510 - 516 0914-5400 1999 [Not refereed][Not invited]
  • Preparation and Characterization of Super-Water-Repellent Coating Films by the Sol-Gel Method(共著)
    Topical Issues in Glasses: Photons, Glasses and Coatings 3 99 - 103 1999 [Not refereed][Not invited]
  • H Nakazumi, K Ishii, Y Sakashita, T Ikai, K Tadanaga, T Minami, M Ueda, M Funato, H Kanazawa, K Natsukawa, Y Sakurai
    2ND INTERNATIONAL CONFERENCE ON COATINGS ON GLASS, ICCG 114 - 119 1999 [Not refereed][Not invited]
     
    The sol-gel colored coating of glass bottles which enabled recycling of the bottles in production process was investigated. The stability of the sol, characteristics and practical resistance of the colored gel films for glass bottles are examined by the gel permeation chromatography, spectroscopic analyses using a fluorescent dye, and mechanical strength analysis, respectively. We found that the inorganic-organic gel films prepared from the mixed alkoxysilanes of phenyltrimethoxysilane and methoxysilane oligomer exhibit good feasibility for this process, especially for the high resistance against boiling water required for sterilization and goad homogeneous dispersion of organic colorants in the gel films. Thermal analyses of organic pigments used in color coating were also performed by a GC-mass spectrometer.
  • A Hayashi, R Araki, R Komiya, K Tadanaga, M Tatsumisago, T Minami
    SOLID STATE IONICS 113 733 - 738 0167-2738 1998/12 [Not refereed][Not invited]
     
    We have systematically investigated the thermal and electrical properties of (1 - y)[xLi(2)S .(100 - x)SiS2]. y[xLi(2)O .(100 - x)P2O5] (45 less than or equal to x less than or equal to 67; y = 0, 0.05, 0.20) oxysulfide glasses in the wide range of lithium ion concentration. These oxysulfide glasses with y = 0.05 exhibited high Tc-Tg values, which is a measure of the glass stability against crystallization, and high ion conductivities at room temperature in the middle range of lithium ion concentration around x = 55 mol%. In the same composition range, large amounts of silicon atoms coordinated with both sulfur and oxygen atoms, i.e. SiOnS4-n (n = 1, 2, 3) tetrahedral units, were observed by Si-29 MAS-NMR measurements. The presence of such unique structural units brought about the high glass stability and high ion conductivity of the glasses with y = 0.05. (C) 1998 Published by Elsevier Science B.V. All rights reserved.
  • H Kitahata, K Tadanaga, T Minami, N Fujimura, T Ito
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 81 (5) 1357 - 1360 0002-7820 1998/05 [Not refereed][Not invited]
     
    YMnO3 thin films with Y/Mn ratios from 1.00/1.05 to 1.00/0.90 were prepared by dip-coating from solution, in which starting materials were refluxed, and the effects of the Y/Mn ratio on the structure and dielectric properties of YMnO3 thin films were investigated. XRD measurements indicated that the films with the Y/Mn ratios in this study were a single phase of polycrystalline YMnO3. The lattice constants along the a-axis and c-axis lengthened with an increase in the Y/Mn ratio. FE-SEM micrographs of the films showed that the surface of the films became smoother and denser with an increase in the Y/Mn ratio. YMnO3 thin films with good dielectric properties were obtained with an Y/Mn ratio of 1.00/0.90, which gave the smoothest and densest microstructure and the smallest leakage current.
  • Kiyoharu Tadanaga, Hiroshi Kobayashi, Tsutomu Minami
    Journal of Non-Crystalline Solids 225 (1-3) 230 - 233 0022-3093 1998 [Not refereed][Not invited]
     
    Sintering and crystallization of low-density La2O3-doped Al2O3 aerogels prepared from Al-alkoxide chemically modified with ethyl acetoacetate were investigated. Isothermal sintering experiments showed that the sintering mechanism of Al2O3 aerogels is surface diffusion. The specific surface areas (SSA) of Al2O3 aerogels heat-treated at 1000 to 1200°C were greatly increased by the addition of 1-2 mol% La2O3. The crystalline phase of Al2O3 aerogels with 1 mol% La2O3 is θ-Al2O3 with heat-treatment at 1200°C, while that of non-doped Al2O3 aerogels is α-Al2O3 with small surface area. Addition of more than 5 mol% La2O3 caused crystallization of La-containing crystalline phases, and the SSA of these aerogels was smaller than that of Al2O3 aerogels with 1-2 mol% La2O3. Addition of small amount of La2O3 prevented aerogels from sintering through surface diffusion, while the addition of more La2O3 caused nucleation of La-containing crystals. © 1998 Elsevier Science B.V. All rights reserved.
  • KOBAYASHI H, TADANAGA K, MINAMI T
    J. Mater. Chem. 8 (5) 1241 - 1244 0959-9428 1998 [Not refereed][Not invited]
  • New Production Process for Colored Glass Bottles Enabling Recycling by the Sol-Gel Method Using Organic Colorants(共著)
    Proc. (]G0010[)(]G0008[) Inter. Cong. on Glass A5 112 - 117 1998 [Not refereed][Not invited]
  • TADANAGA K, KITAHATA H, MINAMI T, FUJIMURA N, ITO T
    J. Sol-Gel Sci. Tech. 13 (1/3) 903 - 907 0928-0707 1998 [Not refereed][Not invited]
  • K Tadanaga, N Katata, T Minami
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 80 (12) 3213 - 3216 0002-7820 1997/12 [Not refereed][Not invited]
     
    Alumina thin films with a roughness of 20 to 50 nm were formed by immersing porous alumina gel films prepared by the sol-gel method in boiling water. When hydrolyzed fluoroalkyltrimethoxysilane was coated on the alumina films, the contact angle for water was increased with an increase of immersion time, and immersion for 30 s was long enough to give super-water-repellency and high transparency; the contact angle for water of the film was 165 degrees and the transmittance for the visible light was higher than 92%. It was found that the surface of the alumina gel films immersed in boiling water consisted of boehmite crystals. It was shown that the existence of air in the hydrophobic pores on the surface caused the super-water-repellency.
  • N Fujimura, H Tanaka, H Kitahata, K Tadanaga, T Yoshimura, T Ito, T Minami
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 36 (12A) L1601 - L1603 0021-4922 1997/12 [Refereed][Not invited]
     
    We demonstrated for the first time that hexagonal YMnO3 films were fabricated from solutions which were effective for lowering the formation temperature. Two different processes, a thermal decomposition method and a reflux method, were studied. In the thermal decomposition method, the solution containing Y(OAc)3 . 4H(2)O and Mn(OAc)(2) . 4H(2)O dissolved in ethanol containing diethanolamine was used for coating. Firing temperatures over 900 degrees C were needed to obtain the YMnO3 single phase film using the thermal decomposition process. In the reflux method, the precursor solution prepared from 2-ethoxyethanol as a solvent was refluxed at 125 degrees C and the solution obtained was used for coating. The reflux process drastically lowered the firing temperatures to 700 degrees C, and this process also improved the microstructure. Effects of reflux on the crystallization process and dielectric properties have been demonstrated.
  • K Tadanaga, K Azuta, T Minami
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 105 (7) 555 - 558 1882-0743 1997/07 [Not refereed][Not invited]
     
    Organic-inorganic hybrid coating films were prepared using vinyltriethoxysilane and tetraethoxysilane by the sol-gel method on polyimide substrates. Tetraethoxysilane (TEOS) and vinyltriethoxysilane (VTES) or polyvinyltriethoxysilane (PVTES), which was obtained by the radical polymerization of VTES, were used as starting materials. In the TEOS-PVTES system, the organic-inorganic hybrid films with both carbon-carbon and siloxane bonds were obtained, and PVTES gave crack-free and flexible films over a wide composition range. It was found that the Si-O-Si bonds in the organic-inorganic hybrid films contributed to the increase in the dynamic hardness, while the smoothness of the coating films prepared using PVTES contributed to the increase in the pencil hardness.
  • K Iwashita, K Tadanaga, T Minami
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 10 (3) 301 - 307 0928-0707 1997 [Not refereed][Not invited]
     
    SiO2-CH3SiO3/2 thin films coated on nylon-6 substrates by the sol-gel method were modified with trimethylsilyl (TMS) groups and their water permeability was evaluated. The water permeability coefficient of the nylon-6 substrates coated with TMS-modified SiO2-CH3SiO3/2 thin films was smaller than that of unmodified ones. The wettability for water of SiO2-CH3SiO3/2 thin films modified with TMS was smaller than that of unmodified ones. The decrease in the wettability by the modification with TMS resulted in the decrease in water permeability. The measurements of pore size distribution and the water permeability coefficient of coating films with different pressures of upstream side suggested that the mechanism of permeation was governed by the capillary condensation flow. This mechanism was also supported by the result that the water permeability coefficient was decreased with a decrease in wettability.
  • FUJIMURA N, TANAKA H, KITAHATA H, TADANAGA K, YOSHIMURA T, ITO T, MINAMI T
    Jpn. J. Appl. Phys. 36 (12A) L1601 - L1603 0021-4922 1997 [Not refereed][Not invited]
  • K. Tadanaga, N. Katata, T. Minami
    J. Am. Ceram. Soc. 80 (4) 1040 - 1042 0002-7820 1997 [Not refereed][Not invited]
  • Kazuki Iwashita, Kiyoharu Tadanaga, Tsutomu Minami
    Journal of Applied Polymer Science 61 (12) 2173 - 2177 0021-8995 1996/09/19 [Not refereed][Not invited]
     
    Nylon-6 substrates were coated with SiO2-RSiO3/2 (R = methyl, vinyl, phenyl) thin films by the sol-gel method, and their water permeability was evaluated. Tetraethoxysilane (TEOS) and trifunctional alkoxides such as methyltriethoxysilane (MTES), vinyltriethoxysilane (VTES), and phenyltriethoxysilane (PhTES) were used as starting materials. Water permeability coefficients of the nylon-6 substrates coated with these SiO2-RSiO3/2 thin films were increased with an increase in the content of these trialkoxysilanes in the films. The water permeability coefficients of these coated nylon-6 substrates were smaller in the order of the systems TEOS-PhTES < TEOS-VTES < TEOS-MTES in the relatively low content of the trialkoxysilanes. © 1996 John Wiley & Sons, Inc.
  • N Tohge, K Tadanaga, H Sakatani, T Minami
    JOURNAL OF MATERIALS SCIENCE LETTERS 15 (17) 1517 - 1519 0261-8028 1996/09 [Not refereed][Not invited]
  • K Tadanaga, S Ito, T Minami, N Tohge
    JOURNAL OF NON-CRYSTALLINE SOLIDS 201 (3) 231 - 236 0022-3093 1996/06 [Not refereed][Not invited]
     
    The precursor structures of aluminum-tri-sec-butoxide (Al(O-sec-Bu)(3)) chemically modified with alkanolamines, such as mono-, di-, and tri-ethanolamines, were investigated using Al-27 NMR. Those spectra revealed that the addition of these alkanolamines led to the structural change around Al atoms and peak half-width decreased with an increase in the number of OH groups in the alkanolamine molecules. The specific surface area of the gels prepared using triethanolamine, which has the strongest stabilizing ability among these alkanolamines, was smaller than the gels using monoethanolamine or diethanolamine. The specific surface area and pore size distribution of Al2O3 gels were thus controllable with varying the kind of alkanolamines.
  • K Tadanaga, K Iwashita, T Minami, N Tohge
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 6 (1) 107 - 111 0928-0707 1996 [Not refereed][Not invited]
     
    Nylon-6 substrates were coated with SiO2 thin films by the sol-gel method and their water permeability coefficient was evaluated. Methyltriethoxysilane (MTES) and tetraethoxysilane (TEOS) were used as starting materials. The addition of MTES to TEOS has enabled the formation of-crack-free thin films on the substrates. The thin films strongly adhered to the substrates. The water permeability coefficients of nylon-6 substrates coated with these thin films decreased with the increase in the ratio of TEOS to the total alkoxides. The pretreatment of the nylon-6 substrates with gamma-aminopropyltriethoxysilane was found to be effective to suppress the water permeability. The water permeability was suppressed by about 40% under the optimal condition.
  • H TANAKA, K TADANAGA, N TOHGE, T MINAMI
    JAPANESE JOURNAL OF APPLIED PHYSICS PART 2-LETTERS & EXPRESS LETTERS 34 (9A) L1155 - L1157 0021-4922 1995/09 [Not refereed][Not invited]
     
    Lead zirconium titanium trioxide (PZT) thin films were prepared by the sol-gel method using Ti and Zr alkoxides chemically modified with acetylacetone and trihydrated lead acetate dissolved in ethanol containing alkanolamines, such as monoethanolamine (MEA), diethanolamine (DEA) and triethanolamine (TEA), as starting materials. In FE-SEM micrographs of PZT thin films with each alkanolamine, the perovskite phases of 400-600 nm in diameter and the Pb-deficient pyrochlore grains of 20-50 nm in diameter, which could not be detected by Xray diffraction (XRD), were observed, although the XRD patterns of the films showed a single perovskite phase. The fraction and size of perovskite phases in the films using MEA are larger than those in the films using DEA or TEA. An overcoating of PbO on these films can lead to the formation of the perovskite single phase. The PZT thin films using MEA showed better dielectric properties than the films using DEA or TEA.
  • K TADANAGA, T IWAMI, T MINAMI, N TOHGE
    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 103 (6) 582 - 585 1882-0743 1995/06 [Not refereed][Not invited]
     
    Microstrucutre of Al2O3 xerogels and aerogels prepared from aluminum-tri-sec-butoxide (Al(O-seo-Bu)(3)) modified with ethylacetoacetate (EAcAc) was investigated for controlling the microstructure of Al2O3. The specific surface area and the pore volume of heat-treated xerogels decreased with an increase in the EAcAc/Al(O-sec-Bu)(3) molar ratio, whereas the size of pores was not affected by the ratio. The specific surface area of aerogels decreased monotonously with an increase in the heat-treatment temperature up to 1000 degrees C and was larger than that of xerogels in the whole temperature range of heat treatment, while that of xerogels decreased with increasing temperature due to sintering and drastically decreased at 1000 degrees C.
  • T IWAMI, K TADANAGA, M TATSUMISAGO, T MINAMI, N TOHGE
    JOURNAL OF THE AMERICAN CERAMIC SOCIETY 78 (6) 1668 - 1672 0002-7820 1995/06 [Not refereed][Not invited]
     
    CdS-doped SiO2 glasses were prepared via silica gels containing diethyldithiocarbamatocadmium Cd(S2CN(C2H5)(2))(2). Heat treatment of the gels gave transparent yellow SiO2 glasses doped with hexagonal CdS crystals. In optical absorption and fluorescence spectra, the optical absorption edge and the emission peak clearly exhibited a blue shift, which was attributed to the quantum size effect of the carrier confinement, as the CdS content was decreased. In the fluorescence spectra of the CdS-doped silica glasses, the emission peak was observed only near 500 nm and not observed at longer wavelengths which were known to be present if there were sulfur vacancies.
  • TADANAGA Kiyoharu, IWAMI Tomoaki, MINAMI Tsutomu, TOHGE Noboru
    Journal of the Ceramic Society of Japan 公益社団法人日本セラミックス協会 103 (1198) 582 - 585 1882-1022 1995/06/01 
    Microstrucutre of Al_2O_3 xerogels and aerogels prepared from aluminum-tri-sec-butoxide (Al(O-sec-Bu)_3) modified with ethylacetoacetate (EAcAc) was investigated for controlling the microstructure of Al_2O_3. The specific surface area and the pore volume of heat-treated xerogels decreased with an increase in the EAcAc/Al(O-sec-Bu)_3 molar ratio, whereas the size of pores was not affected by the ratio. The specific surface area of aerogels decreased monotonously with an increase in the heat-treatment temperature up to 1000℃ and was larger than that of xerogels in the whole temperature range of heat treatment, while that of xerogels decreased with increasing temperature due to sintering and drastically decreased at 1000℃.
  • N KAMIJO, N UMESAKI, K FUKUI, C GUY, K TADANAGA, M TATSUMISAGO, T MINAMI
    JOURNAL OF NON-CRYSTALLINE SOLIDS 177 187 - 192 0022-3093 1994/11 [Not refereed][Not invited]
     
    Using a laboratory X-ray absorption fine structure facility, the local structure of mullite gels prepared from chemically modified aluminium alkoxides has been determined. The gels were dried and heat treated at several temperatures between 60 and 1200 degrees C and the bond lengths and coordination numbers around the aluminium and silicon in each gel were obtained. It is found that the coordination number of oxygen around aluminium is reduced from 6 (in gels dried at 60 degrees C) to similar to 4 (in gels heat-treated at 200, 400 and 800 degrees C). Above 800 degrees C, the coordination number then returns to approximately 5. Double shell models are found to provide better fits for both Al-O and Si-O bonds in all measured gels during curve-fitting analyses. The results indicate that more than two types of coordination coexist for both the Al-O and Si-O sites. Local structure models of the gels are discussed.
  • Tsutomu Minami, Tomoaki Iwami, Kiyoharu Tadanaga, Masahiro Tatsumisago
    Proceedings of SPIE: Sol-Gel Optics III 2288 183 - 192 1994/10/13
  • Kiyoharu Tadanaga, Tsutomu Minami, Noboru Tohge
    Chemistry Letters The Chemical Society of Japan 23 (8) 1507 - 1510 0366-7022 1994/08 [Refereed]
     
    27Al NMR spectra of aluminum-tri-sec-butoxide (Al(O-sec-Bu)3) dissolved in several molar ratios of diacetone alcohol were measured. The spectrum of Al(O-sec-Bu)3 dissolved in diacetone alcohol showed the formation of five-coordinated structural units from original four-coordinated ones. This structural change revealed that diacetone alcohol chemically modified the Al-alkoxide and reduced the reactivity of the alkoxide.
  • Kiyoharu Tadanaga, Tomoaki Iwami, Noboru Tohge, Tsutomu Minami
    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY 3 (1) 5 - 10 0928-0707 1994/01 [Not refereed][Not invited]
     
    The precursor structure and hydrolysis-gelation process of aluminum-sec-butoxide, Al(O-sec-Bu)(3), modified with ethylacetoacetate (EAcAc) were investigated using IR, UV and high magnetic field (11.7 T) Al-27 NMR spectra. Al-27 NMR showed that the reaction of EAcAc with Al(O-sec-Bu)(3) led to the formation of six-coordinated structural units and most of the precursors were assumed to be present as linear trimer containing a four-and two six-coordinated Al atoms. It was found that EAcAc formed the strong chelating bonds with Al(O-sec-Bu)(3), which were hardly hydrolyzed by the attack of water molecules in the gelation process.
  • M TATSUMISAGO, H CHIGUSA, K TADANAGA, N TOHGE, T MINAMI
    MATERIALS CHEMISTRY AND PHYSICS 34 (2) 162 - 165 0254-0584 1993/05 [Not refereed][Not invited]
     
    The preparation process in the melt-solidification method for obtaining high-T(c) superconductor thick films consists of four steps: (I) melting, (II) solidification, (III) heat treatment and (IV) cooling. The preparation conditions for each step were optimized to obtain higher-T(c) superconductor films of Bi1.6Pb0.4Ca2Sr2Cu3Ox. The resulting optimum conditions were found to be very limited; melting at 1000-degrees-C for 15 min (I), solidification at a cooling rate of about 400-degrees-C min-1 (II), heat treatment at 855-degrees-C for more than 12 h (III) and cooling as quickly as possible (IV) brought about the best results. The thick films prepared under these optimum conditions exhibited a T(c)(zero) of 104 K.
  • T YOKO, K TADANAGA, F MIYAJI, S SAKKA
    JOURNAL OF NON-CRYSTALLINE SOLIDS 150 (1-3) 192 - 196 0022-3093 1992/11 [Not refereed][Not invited]
     
    Pb-207 magic angle spinning (MAS)-NMR spectra have been obtained for various Pb-containing crystalline compounds and high lead glasses. The isotropic chemical shifts were determined for the crystalline samples. The more ionic lead atoms with a coordination number larger than six had relatively small chemical shifts between 0 and 2382 ppm with respect to crystalline Pb(NO3)2. On the other hand, the covalent lead atoms with PbO3 trigonal and PbO4 square pyramidal configurations gave a multiplet line profile with shifts ranging from about 3000 to 6000 ppm. The lead atoms with different local environments in PbSiO3 (alamosite) and H-Pb2SiO4, for instance, could be clearly distinguished from each other on the basis of the isotropic chemical shift. The NMR spectra for the high lead glasses of composition 67PbO.33SiO2, 80PbO.20B2O3 and 70PbO.30GaO1.5 were found to exhibit an extremely broad peak with a shift ranging from about 3000 to 6000 ppm. This shift indicates that, in these glasses, neither such highly ionic lead atoms as found in symmetrical PbO6 octahedra nor such highly covalent ones as found in PbO4 square pyramids in the PbO crystal are predominant, but instead PbO3 trigonal or PbO4 square pyramids, with two or three other neighboring oxygens at larger distances as found in H-Pb2SiO4 or PbSiO3, are the major lead-oxygen configuration.
  • F MIYAJI, K TADANAGA, S SAKKA
    APPLIED PHYSICS LETTERS 60 (17) 2060 - 2061 0003-6951 1992/04 [Not refereed][Not invited]
     
    Third harmonic generation from nonconventional MO(x)-PbO-GaO1.5 (M = Ti,Nb,W) glasses have been measured. The nonlinear susceptibility, chi(3), of these glasses at 0.635-mu-m are about 30 times higher than that of SiO2 glass at the same wavelength. It has been found that TiO2 is most effective in increasing refractive index and chi(3).
  • F MIYAJI, K TADANAGA, T YOKO, S SAKKA
    JOURNAL OF NON-CRYSTALLINE SOLIDS 139 (3) 268 - 270 0022-3093 1992/03 [Not refereed][Not invited]
     
    Ga-71 NMR spectra of GaAs and beta-LiGaO2 crystals consisting of four-coordinated Ga3+ ions, GaNbO4 and alpha-Ga2O3 crystals consisting of six-coordinated Ga3+ ions, and PbO-Ga2O3 glasses were measured. About 240 ppm difference in chemical shift was observed between the spectra of beta-LiGaO2 crystal and GaNbO4 crystal. It has been found that Ga3+ ions are mainly tetrahedrally coordinated by four oxygen ions in the glasses by comparison of spectra of the glasses with those of the crystals.
  • Miyaji, Fumiaki, Tadanaga, Kiyoharu, Sakka, Sumio
    Bulletin of the Institute for Chemical Research, Kyoto University Institute for Chemical Research, Kyoto University 69 (5-6) 495 - 510 0023-6071 1992 [Not refereed][Not invited]
  • M TATSUMISAGO, K TADANAGA, S TSUBOI, N TOHGE, T MINAMI
    APPLIED PHYSICS LETTERS 57 (24) 2597 - 2599 0003-6951 1990/12 [Not refereed][Not invited]

MISC

  • 柴田姫芽, 藤井雄太, 三浦章, 鱒渕友治, 忠永清治  ガラスおよびフォトニクス材料討論会講演要旨集  64th-  2023
  • 中里亮介, 松本慶江子, 山口登, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治, CAVALLO Margherita, CROCELLA Valentina, BONINO Francesca, HADERMANN Joke, QUINTELIER Matthias  日本セラミックス協会年会講演予稿集(Web)  2023-  2023
  • 中里亮介, 松本慶江子, 山口登, ROSERO-NAVARRO Nataly Carolina, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治  日本セラミックス協会秋季シンポジウム講演予稿集(Web)  36th-  2023
  • Kiyoharu TADANAGA, Nataly Carolina ROSERO-NAVARRO  Journal of the Japan Society of Powder and Powder Metallurgy  69-  (12)  481  -483  2022/12/15  [Invited]
  • 忠永清治, 山口登, 松本慶江子, ROSERO-NAVARRO Nataly Carolina, 中里亮介, 三浦章  日本セラミックス協会秋季シンポジウム講演予稿集(Web)  35th-  2022
  • Layered Double Hydroxides for Materials of Electrochemical Devices
    Kiyoharu TADANAGA  Journal of the Society of Inorganic Materials, Japan  27-  108  2020/05  [Invited]
  • Hydroxide Ion Conduction in Layered Double Hydroxides and Application to Electrochemical Devices
    Kiyoharu TADANAGA  Ceramics Japan  53-  (5)  335  -338  2018/05  [Invited]
  • 忠永 清治  Electrochemistry  84-  31  -34  2016/01  [Not refereed][Invited]
  • TADANAGA Kiyoharu  NEW GLASS  30-  (2)  31  -33  2015/07  [Not refereed][Not invited]
  • 忠永 清治, 辰巳砂 昌弘  Materials integration  24-  (1)  17  -21  2011/01
  • M. Takahashi, J. Tani, H. Kido, A. Hayashi, K. Tadanaga, M. Tatsumisago  IOP Conference Series: Materials Science and Engineering  18-  (SYMPOSIUM 9A)  2011  [Not refereed][Not invited]
     
    The Li4Ti5O12 and the LiCoO2 have been considered as promising candidates of electrode materials for all-solid-state lithium secondary batteries. The spray pyrolysis method is a useful economical technique to prepare various thicknesses of oxide films though have not been intensively studied for fabrication of thin film lithium batteries. Thin films of Li4Ti5O12 and LiCoO2 electrode materials about 100-400 nm were prepared on quartz and gold substrates by the spray pyrolysis method by using Liacac and, TiO(acac)4 or Co(acac)3 with DMF solvent as starting materials. Electric properties as electrode materials for lithium batteries were estimated by using 3 probe liquid cells with liquid electrolyte LiPF 6 in EC-DMC and Li metal as reference and counter electrodes. Structure and morphology of the films were investigated by XRD and SEM. Crystalline Li4Ti5O12 and LiCoO2 thin films were found to be prepared over 700 °C of substrate temperature. Cyclic voltammograms of the Li4Ti5O12 electrode thin films showed sharp oxidation and reduction peaks around 1.6 and 1.5 V, respectively. Charge-discharge curves for both Li4Ti 5O12 and LiCoO2 electrode thin films showed discharge plateaus around 1.4 and 3.8 V with about 80 mAhg-1 of capacity. These results showed that these electrode thin films prepared by the spray pyrolysis method are electrochemically active and spray pyrolysis method is a promising technique to prepare thin film electrode materials. © 2011 Ceramic Society of Japan.
  • TADANAGA Kiyoharu  Ceramics Japan  44-  (8)  613  -615  2009/08/01
  • 忠永 清治, 辰巳砂 昌弘  化学工業  59-  (2)  124  -127  2008/02
  • エアロゲルの作製と特性
    忠永清治  成形加工  19-  (12)  738  -741  2007  [Not refereed][Not invited]
  • 辰巳砂昌弘, 忠永清治  Journal of the Hydrogen Energy Systems Society of Japan  32-  (2)  11  -15  2007  [Not refereed][Not invited]
  • Kitaura Hirokazu, Takahashi Kenji, Mizuno Fuminori, Hayashi Akitoshi, Tadanaga Kiyoharu, Tatsumisago Masahiro  Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2006-  (0)  94  -94  2006  [Not refereed][Not invited]
     
    本研究では、FeCl<SUB>3</SUB>水溶液に蒸留水または水酸化ナトリウム水溶液を加え、100℃で数日間エージングすることでβ-FeOOHとα-Fe<SUB>2</SUB>O<SUB>3</SUB>をそれぞれ作製した。α-Fe<SUB>2</SUB>O<SUB>3</SUB>は加える水酸化ナトリウム水溶液の量を変えることで粒子径を制御した。得られた粒子を全固体型電池の電極へと応用した。その結果、β-FeOOHが全固体型電池の電極活物質として機能することがわかった。また、全固体型電池においてα-Fe<SUB>2</SUB>O<SUB>3</SUB>の粒子サイズが電気化学的特性に影響を及ぼすことがわかった。また、α-Fe<SUB>2</SUB>O<SUB>3</SUB>の様々な充放電状態のXRD測定から全固体型電池における充放電メカニズムを明らかにした。
  • Akitoshi Hayashi, Takanori Konishi, Kiyoharu Tadanaga, Tsutomu Minami, Masahiro Tatsumisago  RESEARCH ON CHEMICAL INTERMEDIATES  32-  (5-6)  497  -506  2006  [Not refereed][Not invited]
     
    SnS-P2S5 and SnO-P2O5 amorphous materials were prepared by a mechanical milling technique. The SnO-P2O5 milled materials worked as a reversible electrode with higher capacity than SnO crystal in rechargeable lithium cells with conventional liquid electrolytes. All-solid-state cells with a SnX-P2X5 (X = S and 0) amorphous electrode and the Li2S-P2S5 glass-ceramic electrolyte were charged and discharged at room temperature. The sulfide electrodes exhibited better charge-discharge performance than the oxide electrodes, suggesting that SnS-P2S5 electrodes are more compatible with Li2S-P2S5 sulfide solid electrolytes. All-solid state batteries 80SnS center dot 20P(2)S(5)/LiCoO2 showed a charge-discharge plateau of about 3.4 V and high reversible capacity of over 400 mAh/g, even after 50 cycles. The SnX (X = S and O)-based amorphous materials are promising negative electrode materials with high capacity for rechargeable lithium batteries using not only liquid electrolytes but solid electrolytes.
  • ゾル-ゲル電気泳動電着法による厚膜の作製(解説)
    忠永清治  化学工業  57-  (12)  55  -59  2006  [Not refereed][Not invited]
  • 忠永清治, 辰巳砂昌弘  マテリアルインテグレーション  18-  (7)  42  -46  2005  [Not refereed][Not invited]
  • 中温作動形燃料電池用電解質 1.中温作動プロトン伝導性非晶質電解質(解説)
    忠永清治, 辰巳砂昌弘  Electrochemistry  73-  (9)  833  -836  2005  [Not refereed][Not invited]
  • 忠永清治  New Glass  20-  (3)  47  -50  2005  [Not refereed][Not invited]
  • Tezuka Teruaki, Tadanaga Kiyoharu, Matsuda Atsunori, Hayashi Akitoshi, Tatsumisago Masahiro  Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2004-  (0)  16  -16  2004  [Not refereed][Not invited]
     
    Proton conductive inorganic-organic membranes supported by glass papers were prepared from 3-glycidoxypropyltrimethoxysilane, tetraalkoxysilane and orthophosphoric acid to reduce the thickness of membranes without loss of mechanical strength. Hybrid membranes with a thickness of about 50-80 micrometer were obtained by using a glass paper about 40 micrometer thick. The conductivity of the membrane with P/Si of 1.5 was about 1.0 x 10<sup>-3</sup> S cm<sup>-1</sup> at 130 <sup>o</sup>C and 7 % relative humidity. The power density of 120 mW cm<sup>-2</sup> were obtained from the test cells using the membrane supported by glass paper. These cells operated continuously for 50 hours.
  • 無機ベース複合系電解質膜の研究開発(解説)
    忠永清治, 辰巳砂昌弘  燃料電池  4-  (1)  24  2004  [Not refereed][Not invited]
  • 無機-有機複合体膜の燃料電池への応用(解説)
    忠永清治, 辰巳砂昌弘  ケミカルエンジニアリング  49-  (12)  903  2004  [Not refereed][Not invited]
  • 水野 史教, 林 晃敏, 忠永 清治  Electrochemistry  71-  (12)  1196  -1200  2003/12  [Not refereed][Not invited]
  • 中温作動燃料電池用プロトン伝導性無機-有機複合体電解質膜(解説)
    工業材料  51 [4] 35-38-  2003  [Not refereed][Not invited]
  • O2およびH2Oハイバリア性有機-無機ハイブリッドコーティング膜(総説)
    忠永清治  セラミックス  37-  (3)  165  -168  2002  [Not refereed][Not invited]
  • 忠永 清治, 南 努  マテリアルインテグレ-ション  14-  (10)  9  -13  2001/10
  • 忠永 清治, 南 努  マテリアルステージ  1-  (1)  34  -38  2001/04
  • 日本印刷学会誌  38 〔5〕 331-335-  2001  [Not refereed][Not invited]
  • 忠永 清治, 南 努  マテリアルインテグレーション  13-  (12)  69  -72  2000  [Not refereed][Not invited]
  • K Tadanaga, B Ellis, AB Seddon  SOL-GEL OPTICS V  3943-  228  -235  2000  [Not refereed][Not invited]
     
    Structural changes during thermally induced polymerisation of the dipped thin films prepared from TMSPM, zirconium n-tetrapropoxide and methacrylic acid were investigated using near- and mid-infrared (IR) spectroscopy. In the mid-infrared spectra, the intensity of the band due to C=C was decreased by the heat-treatment at 160 degrees C. The intensity of the band due to C=O at around 1720 cm(-1) was also decreased, and that of a band at around 1740 cm(-1) which is assigned to an ester carbonyl C=O in the polymerised methacrylate, was increased. In the near-infrared spectra, the intensities of a band due to the first overtone of fundamental nu(as)(CH2=) and a combination band of nu(as)(CH2=) and nu(C=C) were largely decreased with the heat-treatment at 160 degrees C. These spectral changes show that heat-treatment of the films at 160 degrees C leads to depletion of C=C bonds, indicating that polymerisation has occurred of TMSPM and methacrylic acid. However, in the mid-infrared spectra, the intensity of the band at around 3500 cm(-1) due to O-H bonds, increased with the progress of polymerisation of vinyl groups. Near-infrared spectra of the dipped thin films showed that this increase in intensity of the O-H band is due to the increase of monomeric water molecules hydrogen bonded to silanols. This indicates that polymerised samples are more hydrophilic than unpolymerised ones. The refractive index of the dipped films, measured with a prism coupling method, increased from 1.508 to 1.516 with the polymerisation for composition Zr/(Zr + Si) of 0.2.
  • 忠永 清治, 南 努  機能材料  19-  (4)  47  -53  1999  [Not refereed][Not invited]
  • H Nakazumi, K Ishii, Y Sakashita, T Ikai, K Tadanaga, T Minami, M Ueda, M Funato, H Kanazawa, K Natsukawa, Y Sakurai  2ND INTERNATIONAL CONFERENCE ON COATINGS ON GLASS, ICCG  114  -119  1999  [Not refereed][Not invited]
     
    The sol-gel colored coating of glass bottles which enabled recycling of the bottles in production process was investigated. The stability of the sol, characteristics and practical resistance of the colored gel films for glass bottles are examined by the gel permeation chromatography, spectroscopic analyses using a fluorescent dye, and mechanical strength analysis, respectively. We found that the inorganic-organic gel films prepared from the mixed alkoxysilanes of phenyltrimethoxysilane and methoxysilane oligomer exhibit good feasibility for this process, especially for the high resistance against boiling water required for sterilization and goad homogeneous dispersion of organic colorants in the gel films. Thermal analyses of organic pigments used in color coating were also performed by a GC-mass spectrometer.
  • Preparation and Characterization of Super-Water-Repellent Coating Films by the Sol-Gel Method(共著)
    Topical Issues in Glasses: Photons, Glasses and Coatings  3-  99  -103  1999  [Not refereed][Not invited]
  • New Production Process for Colored Glass Bottles Enabling Recycling by the Sol-Gel Method Using Organic Colorants(共著)
    Proc. (]G0010[)(]G0008[) Inter. Cong. on Glass  A5-  112  -117  1998  [Not refereed][Not invited]
  • ゾル-ゲル法による機能性コーティング薄膜の作製(共著)
    表面技術  48-  (3)  298  -303  1997  [Not refereed][Not invited]
  • Tsutomu Minami, Noriko Katata, Kiyoharu Tadanaga  Proceedings of SPIE - The International Society for Optical Engineering  3136-  168  -175  1997  [Not refereed][Not invited]
     
    Alumina thin films with a roughness of 20 to 50 nm were formed by immersing the porous alumina gel films prepared by the sol-gel method in boiling water. When hydrolyzed fluoroalkyltrimethoxysilane was coated on the alumina films, the films showed super-water-repellency and high transparency the contact angle for water of the film was 165° and the transmittance for visible light was higher than 92 %. When the fluoroalkyltrimethoxysilane-coated thin films were heat-treated at temperatures higher than 500°C, the films became super-hydrophilic the contact angle for water on the films was less than 5°. It was shown the existence of air in the pores on the surface caused the super-water-repellency and that of water in the pores caused the super-hydrophilic property. The transparent, super water-repellent and super-hydrophilic coating films formed on glasses, metals, and ceramics have practical applications such as optical lenses, eye-glasses, cover glasses for solar cells, windshields of automobiles, and so on.
  • エアロゲルの作製と特性(共著)
    忠永清治, 南 努  化学  48-  (5)  360  1993  [Not refereed][Not invited]
  • ゾル-ゲル法による超撥水コーティング膜の作製(共著)
    ニューガラス  12-  (2)  42  -45  [Not refereed][Not invited]

Books etc

  • Next Generation Batterie
    Tadanaga K, Rosero-Navarro N.C, Miura A (ContributorWet Chemical Processes for the Preparation f Composite Electrodes in All-Solid-State Lithium Battery)
    Springer, Singapore 2021/03
  • Solid Electrolytes for Advanced Applications: Garnets and Competitors
    N.C. Rosero Navarro, K. Tadanaga (ContributorSintering Additives for Garnet-type Electrolytes)
    Springer Nature, Switzerland, 2019
  • 全固体電池のイオン伝導性向上技術と材料、製造プロセスの開発
    忠永清治 (Contributor液相法による硫化物固体電解質の作製と電極活物質への固体電解質のコーティング)
    技術情報協会 2017
  • Handbook of Sol-Gel Science and Technology
    Nataly Carolina Rosero-Navarro, Kiyoharu Tadanaga (ContributorSol-Gel Processing of Solid Electrolytes for Li-ion Batteries)
    Springer International Publishing 2016/08
  • ゲルテクノロジーハンドブック
    忠永清治, 辰巳砂昌弘 (Contributorゾル- ゲル法による薄膜形成)
    エヌ・ティー・エス 2014/10 461-466
  • ゾル-ゲル法の最新応用と展望
    忠永 清治 (Contributorゾル-ゲル反応の化学)
    シーエムシー出版 2014/02
  • プラスチックハードコート材料の最新技術(分担執筆) 執筆項目「防曇、防汚」
    シーエムシー出版 2008
  • ナノイオニクス ―最新技術とその展望―(分担執筆) 執筆項目「ゾルーゲル法による電極-電解質ナノ固体界面形成」
    シーエムシー出版 2008
  • ゾル-ゲル法および有機-無機ハイブリッド材料 ―構造制御・高性能化とその応用― 辰巳砂昌弘・忠永清治(分担執筆) 「無機-有機ハイブリッドおよびコンポジット電解質の作製」
    技術情報協会 2007
  • ゾル-ゲル法および有機-無機ハイブリッド材料 ―構造制御・高性能化とその応用― 忠永清治・辰巳砂昌弘(分担執筆) 「電気泳動電着法による透明厚膜の作製」
    技術情報協会 2007
  • ねれと(超)撥水、(超)親水技術、そのコントロール ―実用化および表面処理・試験評価・商品展開― 忠永清治(分担執筆) 「ゾル-ゲル法による撥水-親水パターンの形成と応用」
    技術情報協会 2007
  • 現代無機材料科学(編著:足立吟也、南 努) 忠永清治(分担執筆) 「燃料電池」
    化学同人 2007
  • エコマテリアルハンドブック 忠永清治(分担執筆) 「有機-無機ハイブリッドガラス」
    丸善 2006
  • 撥水・親水・防汚剤の開発とコーティングおよびぬれ性の制御 忠永清治(分担執筆) 「ゾル-ゲル法によるアルミナ透明超撥水膜の作製」
    情報機構 2006
  • Solid State Ionics for Batteries 忠永清治(分担執筆) 「Proton-Conducting Hybrid Materials」
    Springer-Verlag Tokyo 2005
  • ゾル-ゲル法のナノテクノロジーへの応用 忠永清治(分担執筆) 「ガスバリアコーティング膜」
    シーエムシー出版 2005
  • ナノマテリアル工学大系 第1巻ニューセラミックス・ガラス(監修:平尾一之) 忠永清治(分担執筆) 「超撥水ナノコーティング膜」
    フジ・テクノシステム 2005
  • ナノハイブリッド材料の最新技術 忠永清治・辰巳砂昌弘(分担執筆) 「プロトン伝導性無機-有機ハイブリッド電解質膜」
    シーエムシー出版 2005
  • Handbook of Sol-Gel Science and Technology, Vol.2 Characterization of Sol-Gel Materials and Products K. Tadanaga and T. Minami Measurements of Gas Adsorption and Permeability of Sol–Gel Materials
    Kluwer Academic Publisher 2005
  • [ディスプレイ、包装材料用]ハイバリア材料の開発―成膜技術とバリア性の測定・評価方法― (著書、分担執筆) 執筆項目「ゾル-ゲル法による高分子フィルムへの有機-無機ハイブリッド膜のコーティング」
    技術情報協会出版 2004
  • 目的を達成するための ゾル-ゲル法における構造制御ノウハウ集(著書、分担執筆) 執筆項目「ガスバリアコーティング膜-実用化に向けて-」
    技術情報協会 2003
  • 目的を達成するための ゾル-ゲル法における構造制御ノウハウ集(著書、分担執筆) 執筆項目「超撥水、超親水コーティング膜」
    技術情報協会 2003
  • Recent Research Developments in Materials Science (著書, 分担執筆) A. Matsuda, K. Tadanaga, and T. Minami "Prepareation and Application of Nanocomposite Films via Sol-Gel Process with Hot Water Treatment"
    Research Signpost 2001
  • 執筆題目「ゾルーゲル技術による新機能」松田厚載・忠永清治・南努
    ナノマテリアルの最新技術(著書、分担執筆)小泉光恵他編 2001
  • Recent Research Developments in Materials Science (著書, 分担執筆) A. Matsuda, K. Tadanaga, and T. Minami "Prepareation and Application of Nanocomposite Films via Sol-Gel Process with Hot Water Treatment"
    Research Signpost 2001

Presentations

  • Preparation of nano-structured ZrO2-Al2O3 bilayer thin films by sol-gel process and its application to hydrophobic coating films
    清藤太郎, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治
    日本セラミックス協会年会講演予稿集(CD-ROM)  2020
  • Selective metathesis synthesis of MgCr2S4
    三浦章, 井藤浩明, BARTEL Christopher J., SUN Wenhao, ROSERO-NAVARRO Nataly Carolina, 忠永清治, 中田博子, 前田和彦, CEDER Gerbrand, CEDER Gerbrand
    日本セラミックス協会年会講演予稿集(CD-ROM)  2020
  • Nitridation of solution-process derived Sr-Ta oxide precursor thin film with solid nitrogen sources
    樋口亜門, ROSERO-NAVARRO Nataly Calorina, 三浦章, 鱒渕友治, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2020
  • Liquid-phase synthesis of Li2S-P2S5 solid electrolyte by microwave heating
    三浦章, 馬庭陸, ROSERO-NAVARRO Nataly Carolina, 忠永清治
    電池討論会PDF要旨集(CD-ROM)  2019
  • ゾル-ゲル法によるシリカを添加したメチル-フェニルシルセスキオキサン厚膜の作製
    井上雄太, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治, 笠作衛, 幸塚広光, 米田裕和, 新開誠司
    日本セラミックス協会年会講演予稿集(CD-ROM)  2019
  • 自己燃焼反応による新規マンガンモリブデン窒化物の合成
    三浦章, 小田原仁, ROSERO-NAVARRO Nataly Carolina, 忠永清治, 長尾雅則, 田中功
    日本セラミックス協会年会講演予稿集(CD-ROM)  2019
  • シリカフィラーを添加したメチル-フェニルシルセスキオキサン透明厚膜の作製
    井上雄太, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治, 笠作衛, 幸塚広光, 米田裕和, 新開誠司
    日本ゾル-ゲル学会討論会講演予稿集  2019
  • リチウムイオン伝導性無機-有機ハイブリッドの合成および正極-ガーネット型酸化物固体電解質界面への応用
    梶浦龍之介, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治
    電気化学会大会講演要旨集(CD-ROM)  2019
  • ペロブスカイト型有機-無機ハロゲン化鉛を電極材料として用いた全固体リチウム二次電池の構築
    藤井雄太, RAMIREZ Daniel, ROSERO-NAVARRO Nataly Carolina, JULIAN Domingo, 三浦章, JARAMILLO Franklin, 忠永清治
    電気化学会大会講演要旨集(CD-ROM)  2019
  • 大面積(Gd,La)2Si2O7:Ce多結晶薄板の作製とその対アルファ線シンチレーション特性
    福島光, 樋口幹雄, 金子純一, 三浦章, 忠永清治
    セラミックス基礎科学討論会講演要旨集  2018
  • LiZnBO3:Mnの合成と中性子イメージングへの応用
    川又俊介, 樋口幹雄, 金子純一, 竹谷篤, 小林知洋, 若林泰生, 大竹淑恵, 三浦章, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2018
  • 浮遊帯溶融法によるYbドープK2NiF4型およびメリライト型酸化物単結晶の育成
    近添慎弥, 樋口幹雄, 樋口幹雄, 小川貴代, 和田智之, 緑川克美, 鱒渕友治, 三浦章, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2018
  • アミド溶液を介した酸化インジウム薄膜への窒素ドープ
    成瀬雅浩, 三浦章, ROSERO-NAVARRO Nataly Carolina, 忠永清治, 伊左治忠之, 前田真一, 藤本修
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2018
  • SiO2フィラーを添加したフェニルシルセスキオキサン透明厚膜の作製
    井上雄太, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治, 笠作衛, 幸塚広光, 米田裕和, 新開誠司
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2018
  • 焼結助剤を用いたLi7La3Zr2O12系リチウムイオン伝導体の低温焼結とその評価
    竹當知矩, ROSERO NAVARRO Nataly Carolina, 三浦章, 忠永清治
    セラミックス基礎科学討論会講演要旨集  2018
  • (Ce,Pr)OBiS2の構造と超伝導
    三浦章, 長尾雅則, 綿打敏司, 田中功, 後藤陽介, 水口佳一, 森吉千佳子, 黒岩芳弘, ROSERO-NAVARRO Nataly Carolina, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2018
  • 層状酸硫化物LnOInS2(Ln=La,Ce,Pr,Sm)の構造と物性
    井藤浩明, 三浦章, ROSERO-NAVARRO Nataly C., 水口佳一, 後藤陽介, 森吉千佳子, 黒岩芳弘, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2018
  • 液相法で作製した酸化銅薄膜の尿素を用いた窒化
    大東侑生, 三浦章, ROSERO NAVARRO Nataly Carolina, 忠永清治
    セラミックス基礎科学討論会講演要旨集  2018
  • Morphology-Controlled Synthesis of Li6PS5Cl
    三浦章, ROSERO-NAVARRO Nataly Carolina, 忠永清治
    電池討論会講演要旨集  2018
  • Fe-P-S正極を用いた全固体リチウム二次電池の充放電特性
    小林美咲, 藤井雄太, ROSERO NAVARRO N. C., 三浦章, 忠永清治
    電気化学秋季大会講演要旨集(CD-ROM)  2018
  • Mg-Al系層状複水酸化物を固体電解質に用いたアンモニア水燃料電池の構築
    石山翔, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治
    電気化学秋季大会講演要旨集(CD-ROM)  2018
  • リチウムイオン伝導性を有するポリエチレンオキシド系無機-有機ハイブリッドの合成
    梶浦龍之介, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治
    日本ゾル-ゲル学会討論会講演予稿集  2018
  • フェニルシルセスキオキサンゲルの熱軟化を利用した透明厚膜作製
    井上雄太, ROSERO-NAVARRO Nataly Carolina, 三浦章, 忠永清治, 笠作衛, 幸塚広光, 米田裕和, 新開誠司
    日本ゾル-ゲル学会討論会講演予稿集  2018
  • フェニルシルセスキオキサンゲルの熱軟化挙動を利用した厚膜作製
    忠永清治, 井上雄太, NAVARRO N.C. Rosero, 三浦章, 笠作衛, 幸塚広光, 米田裕和, 新開誠司
    日本セラミックス協会年会講演予稿集(CD-ROM)  2018
  • NaInS2-xSex(x=0.5,1,1.5)の結晶構造および光吸収
    三浦章, 高橋夏海, 長尾雅則, 綿打敏司, 田中功, 後藤陽介, 水口佳一, 森吉千佳子, 黒岩芳弘, ROSERO-NAVARRO N.C., 忠永清治
    日本セラミックス協会年会講演予稿集(CD-ROM)  2018
  • ペロブスカイト型酸窒化物BaTaO2Nの爆発的反応合成
    小田原仁, 三浦章, ROSERO-NAVARRO Nataly Carolina, 忠永清治
    日本セラミックス協会年会講演予稿集(CD-ROM)  2018
  • Li3SbS4の合成・結晶構造およびLi+伝導性
    藤井雄太, 三浦章, ROSERO-NAVARRO N.C., 忠永清治, 後藤陽介, 水口佳一, 森吉千佳子, 黒岩芳弘
    日本セラミックス協会年会講演予稿集(CD-ROM)  2018
  • 液相法による全固体リチウム二次電池用Li6PS5Cl固体電解質の作製における溶媒の影響
    丹羽葉月, NAVARRO Nataly Carolina Rosero, 三浦章, 忠永清治
    電気化学会大会講演要旨集(CD-ROM)  2018
  • La置換Gd2Si2O7:Ceの反応焼結とそのシンチレーション特性
    福島光, 樋口幹雄, 和氣嵩暁, 金子純一, 三浦章, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2016
  • 透光性LiYSiO4:Ce多結晶薄板の作製とそのシンチレーション特性
    豊田紗希, 樋口幹雄, 金子純一, 三浦章, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2016
  • NaNH2融液を用いたマンガン酸窒化物の合成とその酸素還元触媒能
    三浦章, ROSERO-NAVARRO Carolina, 鱒渕友治, 樋口幹雄, 吉川信一, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2016
  • 液相焼結による透光性Gd2Si2O7:Ce薄板の作製とその対α線シンチレーション特性
    西方真美, 樋口幹雄, 坪田陽一, 金子純一, 山本誠一, 三浦章, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2015
  • LiCaBO3:Ceの合成とその蛍光特性
    豊田紗希, 樋口幹雄, 坪田陽一, 金子純一, 忠永清治
    結晶成長国内会議予稿集(CD-ROM)  2015
  • Gd2Si2O7:Ce多結晶における粒成長とその対α線シンチレーション特性
    西方真美, 樋口幹雄, 植田あき, 坪田陽一, 金子純一, 石橋浩之, 忠永清治
    応用物理学会秋季学術講演会講演予稿集(CD-ROM)  2014
  • SiO2をセルフフラックスとしたGd2Si2O7:Ceの液相焼結とその対α線シンチレーション特性
    西方真美, 樋口幹雄, 植田あき, 坪田陽一, 金子純一, 忠永清治, 石橋浩之
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2014
  • 透光性Gd2Si2O7:Ce多結晶薄板の作製とその対α線シンチレーション特性
    西方真美, 植田あき, 樋口幹雄, 金子純一, 坪田陽一, 石橋浩之, 忠永清治
    日本セラミックス協会秋季シンポジウム講演予稿集(CD-ROM)  2013
  • SiO2セルフフラックスを用いたGd2Si2O7:Ce焼結体における粒成長と対α線検出器への応用
    西方真美, 植田あき, 樋口幹雄, 金子純一, 坪田陽一, 忠永清治, 石橋浩之
    結晶成長国内会議予稿集(CD-ROM)  2013
  • 麻生圭吾, 林晃敏, 忠永清治, 辰巳砂昌弘, 柏木行康, 山本真理, 斉藤大志, 大野敏信, 中許昌美
    日本化学会講演予稿集  2012/03
  • Egawa Hiromi, Tadanaga Kiyoharu, hayashi Akitoshi, Tatsumisago Masahiro, Mario Aparicio, Alicia Duran
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2012  The Ceramic Society of Japan
     
    Thin films of garnet-type Li<SUB>7</SUB>La<SUB>3</SUB>Zr<SUB>2</SUB>O<SUB>12</SUB> (LLZ) were prepared for the application of all-solid-state thin film lithium batteries. Thin films were prepared by a dip-coating process using a precursor sol from Zr-alkoxide and Li and La nitrates. The thin film of polycrystalline cubic LLZ with a thickness of about 800 nm was obtained after sintering at 900 degree with Li<SUB>2</SUB>CO<SUB>3</SUB> powder.
  • Tadanaga Kiyoharu, Kubo Daiju, Hayashi Akitoshi, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2012  The Ceramic Society of Japan
     
    Electrolyte membranes for all-solid-state alkaline fuel cells were fabricated using Mg-Al layered double hydroxide (LDH) powder with glass paper or Pt-catalyst-loaded carbon cloth as a supporter. Membranes with a thickness of about 100-150 &mu;m were obtained. Fuel cells using those membranes as a electrolyte were confirmed to show OCV of more than 0.9 V. These cells showed higher power density compared with a fuel cell using the Mg-Al LDH pellet as the electrolyte.
  • 電子顕微鏡を用いた全固体リチウム二次電池におけるLiCoO2電極の観察
    林晃敏, 林晃敏, 長尾元寛, 作田敦, 忠永清治, 忠永清治, 辰巳砂昌弘, 辰巳砂昌弘, 戸川欣彦, 戸川欣彦, 森茂生, 森茂生
    電気化学会大会講演要旨集  2012
  • Onaka Tomoko, Tadanaga Kiyoharu, Hayashi Akitoshi, Tatsumisago Masahiro, Aparicio Mario, Durá, n Alicia
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2011  The Ceramic Society of Japan
     
    Thin films of the Li2O-P2O5 system were prepared for the application of all solid state thin film lithium batteries. Aqueous solution of LiNO3 and H3PO4 containing polyvinylpyrrolidone (PVP) was used for coating. Amorphous Li3PO4 thin films with thickness of about 600 nm were obtained after the heat-treatment at 400 <SUP>o</SUP>C. Addition of PVP causes not only the increase of the films thickness but also precipitation of Li3PO4 crystals.
  • バルク型全固体電池におけるLiCoO2正極-硫化物固体電解質界面のTEM観察
    林晃敏, 林晃敏, 長尾元寛, 作田敦, 忠永清治, 忠永清治, 辰巳砂昌弘, 辰巳砂昌弘, 戸川欣彦, 戸川欣彦, 森茂生, 森茂生
    電池討論会講演要旨集  2011
  • ミストCVD法によるLiMn2O4正極薄膜の作製
    山口晃弘, 忠永清治, 作田敦, 林晃敏, 辰巳砂昌弘, APARICIO M., DURAN A.
    化学電池材料研究会ミーティング講演要旨集  2011
  • オルトオキソ酸リチウムで表面修飾したLiCoO2を用いた全固体リチウム二次電池
    林晃敏, 林晃敏, 櫻井友季, 作田敦, 忠永清治, 忠永清治, 辰巳砂昌弘, 辰巳砂昌弘
    電気化学会大会講演要旨集  2011
  • 金属硫化物によって表面修飾されたLiCoO2を用いた全固体リチウム二次電池のキャラクタリゼーション
    中本尚之, 作田敦, 林晃敏, 忠永清治, 辰巳砂昌弘
    セラミックス基礎科学討論会講演要旨集  2009
  • Sakuda Atsushi, Kitaura Hirokazu, Hayashi Akitoshi, Tadanaga Kiyoharu, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2008  The Ceramic Society of Japan
     
    酸化物によってコーティングされたLiCoO<SUB>2</SUB)粒子とLi<SUB>2</SUB>S-P<SUB>2</SUB>SS<SUB>5</SUB>S系固体電解質を用いて全固体リチウム二次電池を作製した。交流インピーダンス測定によって、コーティングが正極-電解質界面の抵抗を低減させることが分かった。界面修飾による抵抗低減により、高い電流密度での作動特性が向上した。
  • 表面修飾されたLiCoO2正極を用いた全固体リチウム二次電池の作製と評価
    作田敦, 北浦弘和, 林晃敏, 忠永清治, 辰巳砂昌弘
    日本セラミックス協会秋季シンポジウム講演予稿集  2008
  • 表面修飾LiCoO2を用いた全固体リチウム二次電池の高電位における作動特性
    作田敦, 林晃敏, 忠永清治, 辰巳砂昌弘
    電池討論会講演要旨集  2008
  • 全固体リチウム二次電池におけるLiCoO2電極-固体電解質界面修飾
    作田敦, 北浦弘和, 林晃敏, 忠永清治, 辰巳砂昌弘
    電気化学会大会講演要旨集  2008
  • Nakamoto Naoyuki, Sakuda Atusi, Kitaura Hirokazu, Hayashi Akitosi, Tadanaga Kiyoharu, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2007  The Ceramic Society of Japan
     
    NiやCoの塩を用いてジエチルジチオカーバマト錯体を作製した。その錯体を溶解させたジクロロエタン溶液にLiCoO2粉末を混合し、乾燥・熱処理を行うことで、LiCoO2粒子表面をNiSやCoSなどの金属硫化物で修飾した。得られた試料を電極に用いて、硫化物電解質を用いた全固体電池を作製し、その特性評価を行った。その結果、金属硫化物でLiCoO2電極を表面修飾することにより、全固体電池は高電流密度下において良好な充放電性質を示すことがわかった。
  • Li2SiO3ガラスで表面修飾したLiCoO2を用いた全固体リチウム二次電池
    林晃敏, 作田敦, 北浦弘和, 忠永清治, 辰巳砂昌弘
    電気化学秋季大会講演要旨集  2007
  • ゾル-ゲル法によるLiCoO2への酸化物ガラスコーティングと全固体リチウム電池への応用
    作田敦, 北浦弘和, 林晃敏, 忠永清治, 辰巳砂昌弘
    電気化学会大会講演要旨集  2007
  • Okuno Shinji, Takahashi Kenji, Hayashi Akitoshi, Tadanaga Kiyoharu, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2006  The Ceramic Society of Japan
     
    プロトン伝導性の付与を目的としてポリベンジルシルセスキオキサンのスルホン化を試みた。スルホン化は出発原料であるフェニルトリエトキシシランをクロロスルホン酸で処理することによりスルホ基を導入し、次いでゾル-ゲル反応を進行させて試料を得る方法と、あらかじめゾル-ゲル法でポリベンジルシルセスキオキサンを作製し、ジクロロメタンに溶解させクロロスルホン酸で処理することでスルホン化した試料を得る方法の二種類を試みた。作製した試料の構造解析、熱分析、導電率の測定などの特性評価を行った。作製した試料の導電率は加湿条件下、30℃で10<sup>-4</sup>から10<sup>-3</sup> S cm<sup>-1</sup>と比較的高い値を示した。
  • Kitaura Hirokazu, Takahashi Kenji, Mizuno Fuminori, Hayashi Akitoshi, Tadanaga Kiyoharu, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2006  The Ceramic Society of Japan
     
    本研究では、FeCl<SUB>3</SUB>水溶液に蒸留水または水酸化ナトリウム水溶液を加え、100℃で数日間エージングすることでβ-FeOOHとα-Fe<SUB>2</SUB>O<SUB>3</SUB>をそれぞれ作製した。α-Fe<SUB>2</SUB>O<SUB>3</SUB>は加える水酸化ナトリウム水溶液の量を変えることで粒子径を制御した。得られた粒子を全固体型電池の電極へと応用した。その結果、β-FeOOHが全固体型電池の電極活物質として機能することがわかった。また、全固体型電池においてα-Fe<SUB>2</SUB>O<SUB>3</SUB>の粒子サイズが電気化学的特性に影響を及ぼすことがわかった。また、α-Fe<SUB>2</SUB>O<SUB>3</SUB>の様々な充放電状態のXRD測定から全固体型電池における充放電メカニズムを明らかにした。
  • Takahashi Kenji, Tadanaga Kiyoharu, Hayashi Akitoshi, Katagiri Kiyofumi, Matsuda Atsunori, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2006  The Ceramic Society of Japan
     
    We successfully prepared poly(phenylsilsesquioxane) particles, one of the organic-inorganic hybrid materials, by two-step acid-base catalyzed sol-gel process. However, the structure and formation mechanism of the particles were not fully understood. In this study, the structure and formation process of the particles prepared by two-step acid-base catalyzed sol-gel process have been investigated. Moreover, poly(phenylsilsesquioxane) particles have been prepared with different amounts of ethanol used as a solvent, and the average molecular weight of the particles has been decreased with an increase in the amount of ethanol.
  • Mizuno Fuminori, Ohtomo Takamasa, Hayashi Akitoshi, Tadanaga Kiyoharu, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2005  The Ceramic Society of Japan
     
    Li<SUB>2</SUB>S-P<SUB>2</SUB>S<SUB>5</SUB>-P<SUB>2</SUB>O<SUB>5</SUB> glass-ceramics were prepared by mechanical milling and subsequent heat treatment. Highly ion-conductive crystals were precipitated in those glass-ceramics, resulting in the enhancement of conductivities. The glass-ceramics with elemental P and S as starting materials showed as high conductivities at room temperature as the ones with P<SUB>2</SUB>S<SUB>5</SUB>. The addition of small amounts of P<SUB>2</SUB>O<SUB>5</SUB> to Li<SUB>2</SUB>S-P<SUB>2</SUB>S<SUB>5</SUB> system led to the improvement in conductivity and electrochemical stability. All-solid-state lithium secondary batteries with the glass-ceramic solid electrolytes worked at room temperature and maintained high capacities and high reversibilities.
  • Takahashi Kenji, Tadanaga Kiyoharu, Hayashi Akitoshi, Matsuda Atsunori, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2005  The Ceramic Society of Japan
     
    Recently, much attention has been paid to various kinds of organic-inorganic hybrid materials because of their optical, mechanical, thermal properties. Up to now, we have successfully prepared poly(phenylsilsesquioxane) particles, one of the organic-inorganic hybrid materials, by the sol-gel method. The poly(phenylsilsesquioxane) particles showed glass transition temperature, and the particles were thermally softened when they were heated at temperatures above glass transition temperature. In this work, thermal behavior of poly(phenylsilsesquioxane) particles was investigated by changing the preparation procedure and the amount of solvent that was used.
  • Hayashi Akitoshi, Tadanaga Kiyoharu, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2005  The Ceramic Society of Japan
     
    Local structure of melt-quenched SnO-MxOy (M=B and P) glasses was analyzed by using solid-state NMR, Raman and Mossbauer measurements. Electrochemical properties during Li<SUP>+</SUP> insertion and extraction of the glassy electrodes were investigated. Li<SUP>+</SUP> insertion to the glasses brought about the reduction of Sn<SUP>2+</SUP> and then the formation of nanocomposites with Sn nanoparticles in the Li<SUB>2</SUB>O-MxOy matrix. Effects of local structure of the glassy matrix on the electrochemical performance of the SnO-MxOy electrodes are discussed.
  • Tezuka Teruaki, Tadanaga Kiyoharu, Hayashi Akitoshi, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2005  The Ceramic Society of Japan
     
    Proton conductive composites composed of cesium hydrogen sulfate (CsHSO<SUB>4</SUB>) or cesium dihydrogen phosphate (CsH<SUB>2</SUB>PO<SUB>4</SUB>) and phosphosilicate gel (PSiG gel) were prepared. The reaction of orthophosphoric acid that derived from phosphosilicate gel and each solid acid produce Cs<SUB>2</SUB>H<SUB>5</SUB>(SO<SUB>4</SUB>)<SUB>2</SUB>(PO<SUB>4</SUB>) in CsHSO<SUB>4</SUB>-PSiG composites and CsH<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> in CsH<SUB>2</SUB>PO<SUB>4</SUB>-PSiG composites. These composites showed high conductivities of 10<SUP>-3</SUP> Scm<SUP>-1</SUP> at 160 <SUP>o</SUP>C under dry condition. The characteristics of composites prepared from silica gel and Cs<SUB>2</SUB>H<SUB>5</SUB>(SO<SUB>4</SUB>)<SUB>2</SUB>(PO<SUB>4</SUB>) or CsH<SUB>5</SUB>(PO<SUB>4</SUB>)<SUB>2</SUB> were compared with those of the composites using phosphosilicate gel.
  • Tezuka Teruaki, Tadanaga Kiyoharu, Matsuda Atsunori, Hayashi Akitoshi, Tatsumisago Masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2004  The Ceramic Society of Japan
     
    Proton conductive inorganic-organic membranes supported by glass papers were prepared from 3-glycidoxypropyltrimethoxysilane, tetraalkoxysilane and orthophosphoric acid to reduce the thickness of membranes without loss of mechanical strength. Hybrid membranes with a thickness of about 50-80 micrometer were obtained by using a glass paper about 40 micrometer thick. The conductivity of the membrane with P/Si of 1.5 was about 1.0 x 10<sup>-3</sup> S cm<sup>-1</sup> at 130 <sup>o</sup>C and 7 % relative humidity. The power density of 120 mW cm<sup>-2</sup> were obtained from the test cells using the membrane supported by glass paper. These cells operated continuously for 50 hours.
  • mizuno fuminori, shibutani yuko, hayashi akitoshi, tadanaga kiyoharu, minami tsutomu, tatsumisago masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2004  The Ceramic Society of Japan
     
    Li<sub>2</sub>S-P<sub>2</sub>S<sub>5</sub>-based glass-ceramics were prepared by mechanical milling and subsequent heat-treatment. In the systems Li<sub>2</sub>S-P<sub>2</sub>S<sub>5</sub>-GeS<sub>2</sub> and Li<sub>2</sub>S-P<sub>2</sub>S<sub>5</sub>-SiS<sub>2</sub>, the conductivities increased with an increase in the heat-treatment temperature and exhibited high values over 10<sup>-3</sup> S•cm<sup>-1</sup> after heating at 550 oC. The high conductivities were mainly caused by the formation of superionic crystals analogous to thio-LISICON in the Li<sub>3</sub>PS<sub>4</sub>-Li<sub>4</sub>GeS<sub>4</sub> solid solutions. All-solid-state cells such as In-Li / Li<sub>4/3</sub>Ti<sub>5/3</sub>O<sub>4</sub> using the highly conductive glass-ceramic electrolytes worked at room temperature and maintained high charge-discharge capacities of over 100 mAh•g<sup>-1</sup> even at the 300th cycle.
  • hayashi akitoshi, konishi takanori, tadanaga kiyoharu, minami tsutomu, tatsumisago masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2004  The Ceramic Society of Japan
     
    Sulfide glassy materials in the system SnS-P<sub>2</sub>S<sub>5</sub>were prepared by mechanical milling. Thermal properties and local structure were examined for the obtained materials. All-solid-state cells were fabricated with the SnS-P<sub>2</sub>S<sub>5</sub> glasses as an electrode and highly conductive Li<sub>2</sub>S-P<sub>2</sub>S<sub>5</sub> glass-ceramics as an electrolyte. Because of using a common P<sub>2</sub>S<sub>5</sub> component, a continuous sulfide network between electrolyte and electrode would be formed in the cells. An All-solid-state cell 80SnS•20P<sub>2</sub>S<sub>5</sub> / 80Li<sub>2</sub>S•20P<sub>2</sub>S<sub>5</sub> / LiCoO<sub>2</sub> exhibited excellent charge-discharge performances at room temperature. The average cell potential was 3.3 V and the cell retained high capacities over 400 mAh/g during charge-discharge cycling for 50 times.
  • ohtomo takamasa, mizuno fuminori, hayashi akitoshi, tadanaga kiyoharu, tatsumisago masahiro
    Preprints of Annual Meeting of The Ceramic Society of Japan
    Preprints of Fall Meeting of The Ceramic Society of Japan  2004  The Ceramic Society of Japan
     
    The Li<sub>2</sub>S-P<sub>2</sub>S<sub>5</sub> glasses were prepared from the mixture of Li<sub>2</sub>S, P and S by using mechanical milling. Electrical properties and local structure of the glasses were investigated. These glasses contained PS<sub>4</sub><sup>3-</sup> and P<sub>2</sub>S<sub>6</sub><sup>4-</sup> units, while the glasses obtained from Li<sub>2</sub>S and P<sub>2</sub>S<sub>5</sub> contained PS<sub>4</sub><sup>3-</sup> unit. The glass-ceramics were prepared by the heat-treatment of these glasses above the crystallization temperature. Raman spectra suggested that the glass-ceramics contained PS<sub>4</sub><sup>3-</sup> unit. The conductivity of the glass-ceramics was more than 10<sup>-4</sup> S/cm at room temperature.

Association Memberships

  • 電気化学会   International Sol-Gel Society   日本ゾル-ゲル学会   高分子学会   日本セラミックス協会   日本化学会   

Research Projects

  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2021/04 -2024/03 
    Author : 忠永 清治, ROSERO CAROLINA
     
    本研究では、リチウムイオン伝導性硫化物固体電解質の液相法での合成における化学を総合的に明らかにすることを目的としている。 本年度は、Li2S、P2S5およびLiClなどを出発原料、アセトニトリルおよびテトラヒドロフランを溶媒して用いたサスペンション法およびサスペンション法と溶解・再析出法を組み合わせた液相法によるLi3PS4およびLi6PS5Clなどの硫化物系固体電解質の合成について検討をおこなった。 アセトニトリルを溶媒に用いたLi2SとP2S5を出発原料とするサスペンション法の合成においては、前駆体として得られるLi3PS4とアセトニトリル分子からなる錯体の結晶構造解析を行い、その結晶構造を明らかにした。この錯体は220℃に加熱した場合に生成する結晶相の生成メカニズムを検討したところ、この前駆体錯体が、室温で安定なγ―Li3PS4よりも、高温での安定相であるβ-Li3PS4相に比較的類似した構造を有していることが、錯体の熱分解によって高温安定相であるβ-Li3PS4相が生成しやすい理由であることを明らかにした。 一方、Li2S, P2S5、LiClをアセトニトリル中でサスペンション法により前駆体錯体を含むスラリーの作製を行い、さらに、溶媒の添加による溶解―再析出法を組み合わせることにより、Li6PS5Cl結晶がられることを見出した。また、溶解再析出法において、非イオン性の界面活性剤を加えることにより、粒径を制御したLi6PS5Clを作製することができることを明らかにした。
  • JST-HORIZON:International cooperation with Japan for Research and Innovation on advanced biofuels and alternative renewable fuels
    Date (from‐to) : 2021/05 -2024/03
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2021/07 -2023/03 
    Author : 忠永 清治
     
    安全性にすぐれた新規蓄電池システムとして、アニオン交換型の電極材料を用いた電池系が注目されている。その中で、水系電解液中で陰イオンが挿入脱離可能な材料の開発が望まれている。本研究では、インターカレーション型の塩化物イオン挿入脱離可能な電極材料として遷移金属含有層状複水酸化物(LDH)を新たに提案し、水系電解液で電気化学的挿入脱離を可能とすることを目指している。 今年度は、遷移金属含有LDHの中で、一種類のみ遷移金属を含む系の代表例としてCo-Al系LDHを選択し主に検討を行い、Co-Al系LDHの酸化還元挙動および塩化物イオンの挿入脱離について、水系電解液および非水系電解液を用いて検討した。 塩化物イオンを層間に含むCo-Al系LDHを共沈法により合成した。この塩化物含有Co-Al系LDH、金属リチウム、LiClを溶解した有機系電解液を用いて3極セルを構築し、サイクリックボルタンメトリー(CV)、定電流充放電試験を行った。CVにおいて、LDH中のCoの酸化還元を確認できた。また、このセルは充放電が可能であり、電池として動作することを確認した。充放電前後でLDH中の塩化物イオンの濃度が変化したことも確認したので、Co-Al系LDHにおいて電気化学的にCoの価数を変化させることによって塩化物イオンを挿入脱離することが確認できた。 さらに、水系電解液においては、炭酸イオンを層間に含むCo-Al系LDHにおいて、水酸化物イオンの挿入脱離を伴うCo-Al系LDHのCoの酸化・還元挙動を確認した。
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (B)
    Date (from‐to) : 2017/04 -2020/03 
    Author : TADANAGA Kiyoharu
     
    In this study, new processes to obtain thin films of metal nitrides or metal oxynitrides at rather mild conditions have been studied. Gel films prepared by the sol-gel process were reacted with a liquid phase of a low-temperature molten salt containing nitrogen, or heat-treated with various nitrogen-containing compounds. Oxide gel films were heat-treated in an electric furnace, where urea was placed upstream, under a nitrogen flow. Cu3N or TaON thin films were obtained by this heat-treatment with copper oxide or tantalum oxide thin films prepared by a liquid phase process.
  • 日本学術振興会:科学研究費助成事業 特別研究員奨励費
    Date (from‐to) : 2013/04 -2016/03 
    Author : 忠永 清治, ROSERO-NAVARRO NATALY CAROLINA, ROSERO-NAVARRO Nataly Carolina
     
    Lithium garnet-type oxides Li7-xLa3Zr2-xNbxO12 (LLZNbO, x=0-1) were prepared by a sol-gel process at low temperatures. Then, glass additives, LiO2-B2O3-SiO2 glass and BaO-B2O3-SiO2 glass, were used to stimulate the sintering of the ceramic electrolyte retaining the cubic phase stable at low temperatures. The cubic garnet phase was formed by a heat-treatment of sol-gel derived precursor powders at 600 - 700 degree C. The presursor powders and glass additives, 53LiO2・31B2O3・12SiO2 (mol%) (LiO2-B2O3-SiO2 glass) or 35BaO・10CaO・5Al2O3・15B2O3・10SiO2 (mol%) (BaO-B2O3-SiO2 glass) were pressed into pellets and sintered at 900 degree C. The relatative density of 86% was achieved by the sintering with glass additives at 900 degree C. In the composites sintered with the BaO-B2O3-SiO2 glass, the presence of La2Zr2O7 was detected at concentration higher of 4 wt%, while the single cubic phase was obtained for the composites sintered with the LiO2-B2O3-SiO2 glass. The ionic conductivity of the obtained composite was 8x10^-5 S/cm at 30 degree C using 4 wt.% of LiO2-B2O3-SiO2 glass. The conductivity is 20% lower than the material reported by the solid state reaction process, but the heat treatment used is about 300 degree C lower than that required by the conventional solid state reaction process. This represents an important contribution to further application of the LLZNbO solid electlolyte to all-solid-state battery.
  • 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 : Tadanaga Kiyoharu, HIGUCHI MIKIO
     
    Zn-Al layered double hydroxide (LDH) thin films intercalated with Eosin Y were prepared by the sol-gel method with hot water treatment. The heat-treated Zn-Al Eosin-Y LDH thin film was confirmed to work as the electrode of a solar cell under visible light irradiation. Powders of Zn-Al layered LDHs intercalated with eosin Y were also found to show the photocatalytic activity under visible light irradiation. The ionic conductivity of (Ni, Mn)-Al LDHs and (Ni, Mn)-Fe LDHs intercalated with CO32- was found to be higher than that of Ni-Al LDH or Ni-Fe LDH. The addition of LDHs to the catalyst layer of an air-electrode increased the current for oxygen reduction reaction (ORR). H2-O2 fuel cells with Mg-Al LDHs as an electrolyte were confirmed to be operated.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Challenging Exploratory Research
    Date (from‐to) : 2012/04 -2014/03 
    Author : TADANAGA Kiyoharu
     
    A novel electrochemical oxygen separation process using a hydroxide ion conductor as an electrolyte has been proposed. In this study, we used Ni-Fe layered double hydroxide (LDH) intercalated with carbonate anion as a hydroxide ion conductive material. The electrodes using Pt/C as a catalyst were prepared, and a membrane reactor for oxygen separation using Ni-Fe LDH as an electrolyte was fabricated. The electrochemical oxygen product flow was confirmed to be proportional to the external current density at 50 degree C under 70% of relative humidity, indicating that electrochemical oxygen separation using Ni-Fe LDH as hydroxide ion conductive material was functioned.
  • 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 : TATSUMISAGO Masahiro, TADANAGA Kiyoharu, HAYASHI Akitoshi
     
    The purpose of the present study is the preparation of sulfide-based lithium ion conductive solid electrolyte from liquid phase. Powders of sulfide-based solid electrolyte (SE) with high lithium concentration were dissolved into N-methylformamide (NMF) and a homogeneous solution was obtained. The NMF solution was dried at 150°C for 3 hours under vacuum to obtain precipitates. The ionic conductivity of the precipitates was 3×10^<-6>S cm^<-1>. Sulfide-based SE was coated onto positive electrode particles by using an NMF solution of SE.The all-solid-state cell using the electrode particles coated with the SE showed good charge-discharge behavior.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2009 -2012 
    Author : TATSUMISAGO Masahiro, TADANAGA Kiyoharu, HAYASHI Akitoshi
     
    Glass-ceramic Li_2S-P_2S_5 electrolytes with a high conductivity of over 5×10^<-3>S cm^<-1>at room temperature were prepared by optimizing preparation conditions of mother glasses, crystallization conditions, glass compositions. Chemical stability of sulfide electrolytes under exposure to air atmosphere was evaluated. The electrolyte with 75 mol% Li_2S showed the highest chemical stability in the binary system Li_2S-P_2S_5. Furthermore, the addition of metal oxides as H_2S absorbents was effective in reducing H_2S gas generation from the electrolytes. All-solid-state In / LiCoO_2 cells with the prepared electrolytes operated as secondary batteries with good cyclability.
  • 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 : TADANAGA Kiyoharu
     
    Thin films of layered double hydroxide(LDH) intercalated with various anions were prepared by immersing sol-gel derived precursor thin films. Organic dyes with sulfo groups were found to be easily intercalated in LDH nanocrystals in this process. Orientation of the nanocrystals on the surface can be controllable with the kind of organic molecules. Mg-Al and Ni-Al LDHs were found to show high hydroxide ion conductivity.
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 2009 -2010 
    Author : 林 晃敏, 辰己砂 昌弘, 忠永 清治
     
    本年度は硫化物固体電解質の導電率向上を目的として、メカノケミカル法を用いたLi_2S-P_2S_5系ガラスとイオン液体の複合化について検討した。75Li_2S・25P_2S_5(mol%)ガラスへ様々なイオン液体を添加し、遊星型ボールミル装置を用いたミリング処理を行うことによって電解質を作製した。その結果、1-ethyl-3-methylimidazolium bis(fluorosulfonyl)amide([EMII[FSA])がガラスの導電率向上に効果のあることがわかった。75Li_2S・25P_2S_5(mol%)ガラスへ10mol%の[EMI][FSA]を添加することによって、ガラスの室温導電率が3.8×10^<-4>Scm^<-1>から7.3×10^<-4>Scm^<-1>へと増加した。さらに、あらかじめリチウム塩lithium bis(trifluoromethanesulfonyl)amide Li[TFSA]を溶解しておいた[EMI][FSA]を添加して得られた電解質は、室温で10^<-3>Scm^<-1>以上の導電率を示した。またサイクリックボルタンメトリーより、この電解質は約5Vの電位窓を有することがわかった。ラマン分光測定の結果、作製した電解質中には、出発物質である硫化物ガラスおよびイオン液体の構成イオン種(PS_4^<3->や[EMI]^+、[FSI]^-)が分解せずに存在していることがわかった。一方、[EMI]BF_4を添加して得られた電解質では、母ガラスと比較して導電率が大きく減少し、これはミリング処理によるBF_4^-の分解に起因していると考えられた。以上の結果から、導電率が高く化学的に安定なイオン液体との複合化が、硫化物ガラス電解質の導電率向上に有効であると結論づけた。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 2007 -2008 
    Author : 林 晃敏, 辰巳砂 昌弘, 忠永 清治
     
    本年度は、電極活物質粒子へのコーティングによるヘテロ界面の構築とそのキャラクタリゼーションを行うとともに、メカノケミカル法を用いた電極-電解質ナノ複合体の合成と評価を行った。また得られた電極材料を用いた全固体電池を作製し、様々な条件での作動特性について検討した。 初期充電後のLiCoO_2正極/Li_2S-P_2S_5電解質界面の構造を調べるために、界面部分の断面TEM観察およびEDX分析を行った。ゾルーゲル法を用いてLi_2SiO_3をコートしたLiCoO_2を用いた電池では、コートなしの場合に比べて、界面付近における電解質側へのCoの拡散が抑制されており、充放電に伴う界面構造変化の小さいことがわかった。またこの電池は、繰り返し充放電による界面抵抗変化が小さく良好なサイクル特性を示し、1〜40mA cm^(-2)の大きな電流密度で二次電池として作動することが明らかになった。また、Li_2O-TiO_2系やLi_2O-Al_2O_3系薄膜についても同様に、コーティングによる界面抵抗低減効果が確認された。 メカノケミカル法により作製したNiS活物質、80Li_2S-20P_2S_5電解質、アセチレンブラックからなるナノ複合体を作用極に用いた全固体電池の充放電条件を検討した。この電池は1.3mA cm^(-2)の比較的大きな電流密度で充放電可能であり、360mAhg^<-1>の容量を50サイクルの間保持した。ナノ複合体の断面TEM観察から、充放電後においても、NiS微粒子が固体電解質と良好な界面コンタクトを保持していることが明らかになった。以上の結果から、電極/電解質ナノ複合体を用いることによって、電極活物質の利用率が増加するだけでなく、良好なサイクル特性を実現することができた。
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research Grant-in-Aid for Scientific Research (C)
    Date (from‐to) : 2007 -2008 
    Author : KIYOHARU Tadanaga
     
    ゾルゲル法で作製したMO-Al_2O_3(M=Mg, Co, Ni, Zn)系前駆体薄膜を、様々な塩を含む温水に浸漬させることにより、陰イオンが層間に挿入された層状複水酸化物微結晶が表面に析出した薄膜を作製した。本手法により、有機色素などの大きな有機分子が挿入された層状複水酸化物微結晶を基板上に容易に析出させることができた。遷移金属を含む薄膜は、電気化学素子の電極として動作することを確認した
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2006 -2008 
    Author : TATSUMISAGO Masahiro, TADANAGA Kiyoharu, HAYASHI Akitoshi
     
    Li_2S-P_2S_5系をベースとするガラス性液体からの超イオン伝導性Li_7P_3S_<11>結晶の析出条件を検討することによって、高いリチウムイオン伝導性と広い電位窓を兼ね備えた硫化物系固体電解質材料を開発した。得られた固体電解質を用いた全固体電池について、電極-電解質界面の構築と評価を行い、全固体リチウム電池が10mA cm^<-2>の大きな電流密度で二次電池として作動することを明らかにした。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 2006 -2007 
    Author : 辰巳砂 昌弘, 忠永 清治, 林 晃敏
     
    これまでに、硫化物系固体電解質材料が、リチウムイオン導電率が極めて高く、電極活物質との間で安定な界面を形成することを見出し、全固体リチウム二次電池用の固体電解質として応用について検討している。電極活物質微粒子をこの硫化物系固体電解質の薄膜でコーティングすることができれば、良好な界面形成によってスムーズな電気化学反応が可能となり、高電流密度の全固体二次電池にそのまま適用できるだけでなく、現在のリチウムイオン二次電池の画期的な高性能化を図ることも期待できる。そこで、本研究では、非金属硫化物リチウム塩の前駆体薄膜を溶液系から作製し、これを用いたリチウムイオン伝導性の高い硫化物固体電解質薄膜の作製条件を明らかにすることを目的として行っている。 特にガラス系で高いリチウムイオン伝導性を示すことがわかっている、Li_2S-P_2S_5系を中心に検討を行った。P_2S_5源として、ジエチルジチオカーバマトリン錯体の合成を試みた。また、Li_2S,P_2S_5,Li_3PS_4およびLi_2S-P_2S_5系ガラスを直接様々な溶媒に溶解させ、これを再析出させることによって、硫化物を得ることについても検討した。Li_3PS_4結晶やLi_2S-P_2S_5系ガラスはトルエンやジメチルスルフォキシドのような溶媒には溶解しないが、ジメチルホルムアミド(DMF)に比較的溶解しやすいことがわかった。よって、これらの硫化物が溶解したDMF溶液は、リチウムイオン伝導性アモルファス非金属硫化物の液相法のよる合成における前駆体となることが示唆された。
  • 日本学術振興会:科学研究費助成事業 特定領域研究
    Date (from‐to) : 2005 -2006 
    Author : 忠永 清治
     
    溶液状態から固体を作製するゾルーゲル法を用いれば、固体電解質の前駆体溶液が固体電極との間に形成する良好なナノメートルオーダーでの固-液界面を、そのまま良好な固体-固体間のナノ界面に変化させることができる。このことに着目し、本研究では、全固体電気化学素子の構築に必要な電極-固体電解質ナノ界面を形成することを目的とした。具体的には、ホスホシリケートゲル・ポリイミド複合体膜を用いた燃料電池の中温領域および無加湿条件化での発電、全固体型電気二重層キャパシタの構築、新規プロトン伝導性無機-有機ハイブリッドの合成を行った。 中温領域において無加湿条件下で高いプロトン伝導性を示す電解質膜の作製を目的として、アミノ基を有する3-アミノプロピルトリエトキシシラン(以下APTES)と硫酸あるいはリン酸を出発物質として無機-有機ハイブリッド膜を作製した。200℃付近まで安定であり、無加湿条件下、200℃で2×10^<-3>Scm^<-1>の比較的高い導電率を示すことがわかった。 次に熱軟化特性を示すことが知られているポリフェニルシルセスキオキサンに、プロトン伝導性基であるスルホ基の導入を試み、そのプロトン伝導性や熱的性質について検討した。XPS測定よりスルポ基のS_<2p>に帰属できるピークが観測されたことから、スルホ基が導入できていると考えられる。熱軟化特性については、スルホン化を行っていない試料に比べると、200℃程度での熱処理による流動は見られなかったが、粒子同士の結着が確認できた。乾燥状態では10^<-11>Scm^<-1>程度と非常に低い導電率を示したが、相対湿度の増加と共に導電率は指数関数的に大きくなり、相対湿度95%以上で約9×10^<-5>Scm^<-1>と6桁以上導電率が上昇することがわかった。
  • 日本学術振興会:科学研究費助成事業 若手研究(B)
    Date (from‐to) : 2005 -2006 
    Author : 忠永 清治
     
    層状複水酸化物(LDH)は、様々な陰イオンを層間に挿入できることが知られている陰イオン交換体である。このLDHは通常、沈殿として作製されるが、コーティング膜として様々な基材の上に形成できれば、LDHの応用が広がることが期待される。 本年度は、前年度に得られた知見をもとに、Zn-Al系LDH薄膜の組成や温水処理温度が結晶析出に与える影響、様々な有機アニオンが挿入されたZn-Al系LDH薄膜の形成、Mg-Al系およびNi-Al系LDH薄膜の作製について検討を行った。 Zn-Al系LDH薄膜の作製において、様々なZn/Al比を有する前駆体アモルファス膜を作製し、温水処理を行ったところ、Zn/Alの比が1のとき、最も多くのLDH結晶が析出することがわかった。また、温水処理温度を60℃とした場合は、100℃の場合と比べて比較的小さなサイズの微結晶が密度高く析出し、透明なLDH薄膜が得られることがわかった。 温水処理の溶液に様々な有機塩を溶かすことによって、様々な有機アニオンが挿入されたZn-Al系LDH薄膜が形成できた。スルホン化されたスピロピラン分子を含む温水処理した場合、x線回折測定の結果、2.658mmの層間隔に対応するピークが観察され、スピロピランが挿入されたLDH薄膜が形成されたことを確認した。 MgO-Al_2O_3系薄膜を作製し、この膜の温水処理によるLDHの析出条件の検討を行ったところ、中性条件下ではLDH結晶の析出は観察されなかったが、pH=12のNaOH溶液を用いて温水処理をおこなったときに最も多くの結晶が析出することがわかった。
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2004 -2005 
    Author : MATSUDA Atsunori, SAKAI Mototsugu, MUTO Hiroyuki, KOGURE Toshihiro, TADANAGA Kiyoharu, UCHIKOSHI Tetuso
     
    External fields of vibrations and electric voltages affected the nanostructure of titania crystallites formed on SiO_2-TiO_2 gel coatings during hot-water treatment. Without the external fields granular anatase nanocrystals of 30-50 nm in size were formed on the coatings during the hot-water treatment, whereas the shape of the precipitates became sheetlike by applying a vibration to the substrate during hot-water treatment. Similar changes in shape of the precipitates on the coatings were also observed, and ramiform (branchlike) crystallites were formed at the negative electrode by applying an electric field between the substrates. The sheetlike and ramiform crystallites are mainly composed of a hydrated titania, m(TiO_2)・nH_2O, with the lepidocrocite-like layered structure with a d-spacing of 0.6-0.8 nm. Titania nanosheets are characterized by a large surface-to-volume ratio, which gives rise to the excellent wettability for water and antifogging properties. Processing temperatures for the preparation of the coatings can be lowered at about 60℃ under atmospheric pressure, so that the coatings have a great potential for applications to various substrates including organic polymers with poor heat resistance. The addition of supramolecular assemblies of CTAB, P123, and F127 in the SiO_2-TiO_2 gel films permits the formation porous film structure and highly dispersion of anatase nanocrystals in the whole films after hot-water treatment. When the anatase nanocrystal-dispersed, porous films were irradiated with UV light, residual surfactants were completely eliminated due to the photocatalytic effects of the nanocrystals. SiO_2-TiO_2 spherical microparticles of about 0.7 μm in diameter have been prepared by the sol-gel method. Anatase nanocrystals were formed in the microparticles and their specific surface area was increased after a hot-water treatment at 90℃. Particulate, thick films were electrophoretically deposited on indium-tin oxide (ITO)-coated glass substrates using the anatase nanocrystal-precipitated SiO_2-TiO_2 microparticles. Hot water treatments were also found to be effective to form nanostructure as well as nanocrystals for Al_2O_3, SnO_2 and ZnO gel films at low temperatures. Cubic SnO_2 and hexagonal ZnO crystallites were precipitated by the hot water treatment, whereas AlO(OH) crystallite were formed on the Al_2O_3 film. With respect to ZnO gel coatings, the electric voltage and type of substrates showed a significant influence on the crystal habit of ZnO on the negative electrode. Hexagonal columnar and petal-like crystallites, which were oriented in the C-axis direction, were formed ITO-coated glass substrate and Si wafer, respectively.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2003 -2004 
    Author : TATSUMISAGO Masahiro, TADANAGA Kiyoharu, HAYASHI Akitoshi
     
    1.Glass ceramic materials with various compositions in the system Li_2S-P_2S_5 were prepared by mechanical milling of starting materials and subsequent heat treatment. The 70Li_2S-30P_2S_5 glass-ceramic obtained by crystallization of mechanically milled glass showed a higher ambient-temperature conductivity of 2.2x10^<-3> Scm^<-1>. The enhancement of conductivity was due to the formation of the new, highly conductive, metastable crystalline phase. The main structural units of the crystal were the P_2S_7^<4-> ions. 2.The Li_2S-P-S glasses were prepared by mechanical milling from the mixture of Li_2S and elemental phosphorus and sulfur. The Li_2S-P-S glass-ceramics contained mainly PS_4^<3-> ions with a small amount of S-S bonds, and the homo bonds present in the corresponding glasses almost disappeared by the heat treatment of the glasses. 3.The all-solid-state cells with the combination of the SnS-P_2S_5 glassy electrode and the Li_2S-P_2S_5 glass-ceramic electrolyte were constructed. The cell using the 80SnS - 20P_2S_5 glass as an anode worked as a secondary battery, which was a first step of glassy monolithic cells with a common glass network. 4.All-solid-state cells using cathode materials consisting of sulfur and CuS were successfully prepared and exhibited excellent cycling performance at room temperature. 5.The effects of conductive additives in composite positive electrodes on charge-discharge behaviors of all-solid-state In/LiCoO_2 cell with Li_2S-P_2S_5 glass-ceramic electrolytes were investigated. Under relatively high current densities, the cell with VGCF kept larger discharge capacities during 50 cycles compared with the cells with other conductive additives like AB.
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1999 -2004 
    Author : 南 努, 脇原 將孝, 岩倉 千秋, こうじ谷 信三, 田中 功, 忠永 清治, 足立 吟也, 曽我 直弘
     
    平成11年度〜15年度に実施した本特定領域の成果をまとめるために本の出版を行った。各班長および関連する企業の3名の研究者を中心に原稿を執筆し、シュプリンガーフェアラーク社より、"Solid State Ionics for Batteries"というタイトルで全世界で発売することとなった。以下に目次を示す。 1.Introduction 2.Recent progress in batteries and future problems 3.Recent development of amorphous solid electrolytes and their application to solid-state batteries 4.Recent development of electrode materials in lithium ion batteries 5.Construction of solid/solid interface between hydrogen storage alloy electrode and solid electrolyte for battery application 6.Polymer solid electrolytes for lithium-ion conduction 7.First principles calculations of lithium battery materials
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2002 -2003 
    Author : MATSUDA Atsunori, MUTO Hiroyuki, TADANAGA Kiyoharu, SAKAI Mototsugu
     
    Solid state proton-conductive membranes with high conductivity in the medium temperature range (100-200ーC) even under low humidity are highly required as the electrolytes for PEFCs. Since the operation of PEFCs in the medium temperature range improves the utilization of total electric power generated in the cells. and depresses the poisoning of Pt catalysts with CO in the fuel gases. In addition, working of PEFCs under low humidity permits to reduce the weight and volume of humidifiers. In the present work, proton conducting membranes based on sol-gel derived phosphosilicate (P_2O_5-SiO_2) gel have been fabricated for the application to medium temperature fuel cells as an electrolyte. Two types of proton conductive membranes, which show high conductivities even at medium temperatures with low humidity, have been successfully prepared. One is a composite sheet composed of phosphosilicate gel powder and organic polymer such as heat resistant polyimide. The other is a hybrid sheet in which inorganic and organic components derived from an organosilane such as 3-Glycidoxypropyltrimethoxysilane and phosphoric acid are covalently bonded. Fuel cells using a composite sheet composed of phosphosilicate (P_2O_5-SiO_2, P/Si=1 in mole ratio) gel powder and polyimide operated up to 150ーC under a relatively low water vapor, pressure. Maximum power density of the fuel cell increased with increasing operation temperature and was 28 mW cm^<-2> at 150 ℃ and 18 %RH. With respect to the hybrid type, fuel cells using a hybrid sheet derived from 3-Glycidoxypropyltrimethoxysilane and phosphoric, acid also continuously operated at 130 ℃. It was found that the addition of tin and tantalum as well as aluminum improved the chemical durability of phosphosilicate gels by depressing the leaching of phosphoric acid from the gels. At the same time, the improvement of durability of the gels resulted in a decrease in the proton conductivity.
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1999 -2003 
    Author : 南 努, 松田 厚範, 忠永 清治, 辰巳砂 昌弘, 河村 純一, 町田 信也
     
    本年度得られた成果は以下の通りである。 1.リチウムイオン濃度を高めたLi_2S-SiS_2-P_2S_5-Al_2S_3多成分系ガラスを比較的低温で結晶化させることによって、固相反応では得られない高イオン伝導性チオリシコン結晶がガラスから初晶として析出し、室温で1.2x10^<-3>Scm^<-1>の極めて高い導電率を示すことが分った。 2.メカノケミカル法を用いてSnS-P_2S_5系負極材料やCu-S系正極材料を合成し、共通のガラスフォーマーを有するLi_2S-P_2S_5系固体電解質と組み合わせた全固体電池を試作した。いずれの場合もサイクル特性に優れた二次電池として作動し、従来のリチウムイオン二次電池と比べると大きな充放電容量の得られることが分かった。 3.Li_2S-P_2S_5系固体電解質を用いたIn/LiCoO_2系全固体電池において導電助剤の検討を行ったところ、アセチレンブラックは初期不可逆容量の一因となることが分かった。一方、気相成長炭素繊維を用いると不可逆容量を低減することができ、高電流密度での充放電が可能になることが明らかになった。 4.ゾル-ゲル法によってホスホシリケート系ハイブリッドおよびコンポジット系シートを作製した。γ-グリシドキシプロピルトリメトキシシランを用いたハイブリッド系シートやポリイミドを用いたコンポジットシートを電解質膜とした固体高分子形燃料電池は、130℃以上、相対湿度数%の中温低加湿条件下でOCVが0.7-0.85V、最大出力が20-50mWcm^<-2>を示し、連続発電できることが分かった。 5.レーザー蒸着(PLD)法によって、SnO/Li-V-Si-O系ガラス/LiCoO_2系全固体薄膜リチウム二次電池を試作した。200μAcm^<-2>までは二次電池として作動可能であり、容量は大きくないものの、100サイクル以上の充放電を確認した。動作可能な薄膜二次電池が全プロセスPLD法を用いて作製できたことにより、将来のマイクロエレクトロニクスの電源素子として、そのプロセスの確立が望まれる。
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2001 -2002 
    Author : MINAMI Tsutomu, MATSUDA Atsunori, TADANAGA Kiyoharu, TATSUMISAGO Masahiro, NAKAMA Kenichi
     
    1. Transparent, thick films with high refractive index have been successfully prepared using silsesquioxanes from such as phenyltriethoxysilane and benzyltriethoxysilane and metal oxides. Titania-silsesquioxane films showed the highest refractive index. Thick films from diphenyldimethoxysilane and titania showed higher refractive index than the films from phenyltrietoxysilane and titania. Thick films from diphenylmethoxysilane showed fluidity with less than 30 mol % of titania. 2. Changes of structure, morphology, and optical properties of silsesquioxane-titania thick films by UV-irradiation have been investigated. Irradiation of UV-light led to depletion of Si-C bonds in the thick films, and hardness and refractive index of the films were increased. It was found that hardness of the vinylsilsesquioxane-titania films mostly increased. 3. Micropatterns of phenylsisisesquioxane-titana thick films were successfully prepared by the embossing process. Convexly shaped micropatterns have been formed on hydrophobic-hydrophilic patterned substrate with titania and fluoroalkylsilanes thin layer, based on the difference in the surface free energy and fluidity of the phenylsilsesquioxane-titana at temperatures higher than then-glass transition temperatures.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2001 -2002 
    Author : TATSUMISAGO Masahiro, MATSUDA Atsunori, TADANAGA Kiyoharu, MINAMI Tsutomu
     
    1. Amorphous materials with various compositions in the systems Li_2S-P_2S_5, Li_2S-P_2S_5-SiS_2, and Li_2S-P_2S_5-GeS_2 were prepared by mechanical milling (MM) of crystalline starting materials in a dry N_2 atmosphere at room temperature. The pelletized samples of these glassy materials exhibited high conductivities in the order of 10^<-4> Scm^<-1> at 25℃. It was found that the transport number of lithium ions of the glassy materials was almost unity and the potential window as solid electrolytes was wider than 10 V. 2. Highly conductive glass-ceramics were obtained by the heat treatment under a variety of conditions of the above glassy materials prepared by MM. The glass-ceramics obtained after heating at around 230℃ showed the X-ray diffraction patterns very similar to those of highly conductive thio-LISICON II phases in Li_<4-x>Ge_<1-x>P_xS_4, suggesting that the thio-LISICON II analogue is formed in the glass-ceramics derived from the mechanically milled glassy powder in these systems. 3. The highly conductive glass-ceramics were also obtained by the MM of starting materials of elements. Glassy Li_2S-P_2S_5 samples were successfully prepared by the MM of Li_2S, P, and S. The properties and structure of the glassy samples are very similar those of the samples prepared using Li_2S and P_2S_5. The glass-ceramics obtained by the heating of such an element-derived sulfide glasses exhibited similar properties to the glass-ceramics from P_2S_5-derived glasses. 4. Electrochemical cells were constructed using glass-ceramics in the system Li_2S-P_2S_5 obtained by MM and heat treatment as an electrolyte, LiCoO_2, as a positive electrode and indium as a negative electrode. The all-solid-state cell exhibited excellent cycling performances with the reversible charge-discharge capacities of about 100mAhg^<-1> even after 200 cycles.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 2001 -2002 
    Author : MINAMI Tsutomu, MATSUDA Atsunori, TADANAGA Kiyoharu, TATSUMISAGO Masahiro
     
    In the present study, surface texture of the coating films prepared by the sol-gel method has been controlled to obtain new functional materials. 1. Anatase nanocrystallites were found to be formed on the surface of SiO_2-TiO_2 gel films through immersion in boiling water. The anatase precipitated films showed high photocatalitic activity. Anatase crystals were formed even through the immersion of the gel films in hot water of 55 ℃ after being dried at 60 ℃. Titania nano-sheets were found to be formed through the immersion of the films in hot water under vibration. The surface with titania nano-sheets has a small roughness, and shows superhydrophilic properties. These properties were kept even after being kept under a dark place for more than 2000 h. 2. When UV-light was irradiated on the SiO_2-TiO_2 gel films prepared from titanium alkoxide modified with ethyl acetoacetate, the solubility of irradiated area for various solvents become very small. By the irradiation of UV-light through a photo mask and etching of unirradiated area, micropatterns of SiO_2TiO_2 gel films were obtained. By immersion of the micropatterned SiO_2-TiO_2 gel films in hot water, anatase nano-crysltallites were formed on the micropatterned surface. 3. Small roughness of about 20 to 50 nm was found to be formed by immersion of Al_2O_3 gel films prepared from Al-alkoxide modified with ethyl acetoacetate, in hot water at 40 ℃. On the other hand, the surface with the small roughness shows very low reflectivity with the wide wavelength region.
  • 日本学術振興会:科学研究費助成事業 奨励研究(A)
    Date (from‐to) : 2000 -2001 
    Author : 忠永 清治
     
    本研究は、ゾル-ゲル法によって作製した超撥水表面を、光照射等の手法を用いて局部的に親水化し、超撥水-超親水パターンを形成すること、およびこのパターンの応用を検討することを目的として行ったものである。今年度は、昨年度に得られた知見を基にさらに研究を進め、以下のような成果を得た。 (1)多数の円が規則正しくならんだフォトマスクを用いて紫外光を照射することによって得られた超撥水-超親水パターン上に、水を溶媒としたコロイダルシリカ、ポリエチレングリコール、加水分解したテトラメトキシシランからなるシリカゾルをコーティングすると、このゾルは、光照射部である親水部分にのみ残り、乾燥後、膨らみ形状を持つシリカマイクロパターンが形成できることがわかった。 (2)ポリエチレングリコール、テトラメトキシシランを加えない場合には、非常に小さい厚みのパターンしか形成できない。また、シリカゾルの濃度、ポリエチレングリコールの添加量を変化させることで、得られる膨らみパターンの厚みが制御できることがわかった。 (3)超撥水を得るために形成している凹凸の程度を変化させた撥水-親水パターンを形成し、マイクロパターン形成に及ぼす凹凸の影響について検討した結果、凹凸が小さい方がより大きな厚みを持つマイクロパターンが得られることがわかった。 (4)プロセスの低温化について検討した結果、全プロセス100℃以下で、超撥水-超親水パターンが形成できることがわかった。
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 1999 -2000 
    Author : MINAMI Tsutomu, MATSUDA Atsunori, TADANAGA Kiyoharu, TATSUMISAGO Masahiro, MAEDA Koichi
     
    1. transparent, thick films have been successfully prepared using benzyltriethoxysilane-derived particles in the electrophoretic sol-gel deposition and the successive heat treatment. In addition, photo-polymerizable inorganic-organic hybrid films and the inorganic-organic hybrid films with high refractive indexes have been synthesized for their application to photolithographic and embossing micro-patterning, respectively. 2. The thickness of the methylsilsequioxane-phenylsilsesquioxane films which can be formed on the substrates without cracking was maximized at around the mole ratio of methy group : phenyl group=1 : 1. The optimum film hardness and the adequate timing for emboss micro-patterning were clarified. The refractive index of the phenylsilsesquioxane and benzylsilsesquioxane films increased with increasing the amount of titania added. 3. Optical waveguides have been photolithographically fabricated on glass substrates using vinyltrimethoxysilane-derived inorganic-organic hybrid films. Micro-lens arrays have been newly formed on hydrophobic-hydrophilic patterned substrates based on the difference in the surface free energy and fuluidity of the phenylsilsesquioxane and benzylsilsesquioxane at temperatures higher than their glass transition temperatures. 4. The shapes of the fabricated optical waveguides and micro-lens arrays were evaluated using SEM, AFM and 3D-surface profilometer. Fabricated micro-lens arrays showed good focusing properties.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 1999 -2000 
    Author : TATSUMISAGO Masahiro, MATSUDA Atsunori, TADANAGA Kiyoharu, MINAMI Tsutomu
     
    1.Amorphous materials with various compositions in the oxysulfide system Li_2S-SiS_2-LixMOy (LixMOy=Li_4SiO_4, Li_3PO_4) were obtained by mechanical milling (MM) of crystalline starting materials in a dry N_2 atmosphere at room temperature. The pelletized samples exhibited high conductivities in the order of 10^<-4> Scm^<-1> at 25℃. It was found that the transport number of lithium ions of the amorphous materials was almost unity and the potential window as solid electrolytes was wider than 10V. 2.Several spectroscopic measurements like MAS NMR and XPS revealed that the local structure of the amorphous oxysulfide powders prepared by MM was very close to thata of the corresponding melt quenched glass. Furthermore, the formation of continuous amorphous phase with the inrease of milling tive incresed conductivity grastically from 10^<-10> to 10^<-4> Scm^<-1> at room temperature. 3.The amorphous Li_2S-P_2S_5 sample prepared by MM exhibited high conductivity of 9x10^<-5> S cm^<-1> at room temperature. After the sample was heated up to the crystallization temperature, the conductivity decreased with a smaller slope in the cooling process. The conductivity of the heated sample was 6x10^<-4> S cm^<-1> at room temperature. It was revealed that the conductivity improvement with forming the. 80Li_2S・20P_2S_5 glass-ceramics was brought about by the softening of glassy powders and the formation of highly conductive Li_7PS_6 crystal. 4.Electrochemical cells were constructed using amorphous matterials in the system Li_2S-SiS_2-Li_4SiO_4 obtained by MM as an electrolyte, LiCoO_2 as a positive electrode and indium as a negative electrode. The charge-discharge capacity decreased gradually from 90 to 70 mAhcm^<-2> till about the 10th cycle and became stable after the 10th cycle.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 1999 -2000 
    Author : MINAMI Tsutomu, MATSUDA Atsunori, TADANAGA Kiyoharu, TATSUMISAGO Masahiro
     
    (1) UV irradiation on a superhydrophobic coating film which consists of three layers, a flowerlike Al_2O_3 gel film, a very thin TiO_2 layer, and a FAS layer, led to conversion of the superhydrophobic surface into a superhydrophilic surface. (2) A small roughness of about 20-50 nm was found to form on the Al_2O_3 gel films prepared from aluminum alkoxide and then immersed in hot water at 60℃. The coating of hydrolyzed fluoroalkyltrimethoxysilane on the flowerlike Al_2O_3 films produced transparent, superhydrophobic films with contact angle for water larger than 150°. (3) Silica thin films containing organic polymers were prepared on PET substrates by the sol-gel method. Poly(vinyl alcohol) was found to be most effective to suppress the water and oxygen permeability of PET substrates coated with the organic-inorganic composite films. (4) YMnO_3 thin films prepared from solution and heat-treated in vacuum had a fine, uniform, and dense structure with a very smooth surface. The ferroelectricity of the solution-derived YMnO_3 thin films at room temperature was observed for the first thme due to the improvement of crystallinity and the leakage current by the vacuum heat treatment. (5) Transparent and porous anatase nanocrystals-dispersed films were prepared by treating the sol-gel derived TiO_2-SiO_2 coating films containing poly (ethylene glycol) with hot water. In the SiO_2-TiO_2 films without the addition of poly (ethylene glycol), anatase nanocrystals were formed at the surface of the films with hot water treatment, and the surface had a small roughness.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 1997 -1998 
    Author : MINAMI Tsutomu, INABA Hiroshi, MATSUDA Atsunori, TADANAGA Kiyoharu, TATSUMISAGO Masahiro
     
    1. Alumina thin films with roughness of 20 to SO nm were formed by the sol-gel method by immersing porous alumina gel films, which were prepared from Al(O-sec-Bu)_3 chemically modified with ethyl acetoacetate, in boiling water. The roughened surface like flower of the alumina gel films after the immersion was found to consist of boehmite crystals. 2. When hydrolyzed fluoroalkyltrimethoxsilane was coated on the flower-like boehmite thin film, the contact angle for water increased with an increase of immersion time, and the immersion for 30 s was long enough to give super-water-repellency and high transparency ; the contact angle for water of the films was 165゚and the transmittance for the visible light was higher than 92 %. 3. The super-hydrophobic alumina films coated with fluoroalkyltrimethoxysilane became super- hydrophilic after a heat treatment at temperatures higher than 500* ; the contact angle for water on the films was less than 5゚. 4. Fluorine-free super-hydrophobic coatings were successfully prepared on the flower-like alumina by over-coating with hydrolyzed alkyltrimethoxysilane. The length of the alkyl groups and the concentration of the alkyltrimethoxysilane in the coating solution affected the hydrophobicity of the resultant coating films. 5. We have prepared super-hydrophobic coatings without flower-like alumina under layer using several organoalkoxysilanes. Among the organoalkoxysilanes examined, dimethyldiethoxysilane and phenyltriethoxysilane formed transparent super-hydrophobic coatings by heat-treating their films. SEM observation showed that the coating had a finely roughened surface with fractal structure.
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 1997 -1998 
    Author : MINAMI Tsutomu, MATSUDA Atsunori, TADANAGA Kiyoharu, TATSUMISAGO Masahiro
     
    1. Organic-inorganic hybrid coating films, which were crack-free and flexible, were prepared using polyvinyltriethoxysilane and tetraethoxysilane by the sol-gel method on polyimide substrates. 2. Thick silica films were prepared on the cathode by the electrophoretic sol-gel deposition using a cationic polymer surfactant, polyethylenimine (PEI). When the content of PEI added was 0.01 mass% and pH of the coating sols was 5, the resultant thick silica films had no cracks and the thickness was ca. 20 *m. 3. YMnO_3 thin films being proposed as a new material for non volatile ferroelectric memory devices were prepared from ethanol solutions of Y(OAc)_3 and Mn(OAc)_2. The reflux process was found to drastically lower the firing temperature and improve the microstructure and dielecfric properties of the resultant films. 4. We have found that anatase nanocrystals with about 6 nm in diameter precipitated in sol-gel derived TiO_2-SiO_2 thin films after hot water treatment and that the addition of organic polymer accelerated the precipitation of anatase. This mild process enable us to form anatase nanocrystals- dispersed films on various kinds of substrates including organic polymer and organism of which heat resistance is poor. 5. Thick films were prepared on ITO-coated glass substrates by electrophoretic deposition using sols containing phenylsilsesquioxane (PhSiO_<3/2>) particles derived from phenyltriethoxysilane. Transparency of the thick PhSiO_<3/2> films was significantly improved by a heat-treatment at 400゚C.From SEM observation, the thick films were found to change in morphology from aggregates of particles with a number of open spaces among the particles to a monolith with no open spaces after the heat-treatment.
  • 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 : 忠永 清治
     
    MFS型(金属-強誘電体-半導体)不揮発性メモリーへ応用できると考えられる、YMnO_3系複合酸化物薄膜をゾル-ゲル法によって作製し、その結晶化温度の低温化、誘電特性を評価した。 YMnO_3系強誘電体薄膜を作製する際の出発原料として、酢酸イットリウム、酢酸マンガン、溶媒として2-エトキシエタノール、添加剤としてジエタノールアミンを用いた場合に、約100〜500nmの膜厚を持つ均質な薄膜が得られることを見い出した。また、これらの出発原料を混合して作製した溶液でコーティングを行った場合には、900℃以上の熱処理で単相のYMnO_3が作製できるのに対し、出発原料を還流し、イットリウムおよびマンガンのアルコキシドを生成させてからコーティングを行うと、結晶化温度が低下し、800℃の熱処理で単相が得られることがわかった。走査型電子顕微鏡により表面の組織を観察したところ、粒子が大きく成長し、その粒子間に数十nm以上の穴の存在する組織であることが確認された。また、電気的特性に関しては、リ-ク電流が非常に大きく、十分な誘電特性の評価を行うことができなかった。 さらに、出発組成における、イットリウムとマンガンの比をわずかに変化させて薄膜を作製した場合、5〜10%イットリウムが過剰の組成において緻密で平滑な表面を持つ薄膜を得ることができた。この薄膜において測定した誘電率は約20、損失係数は約0.05、また、リ-ク電流は1Vの印加で10^<-4>A・cm^<-2>となった。但し、緻密化が十分でないために、細孔や粒界が存在し、低周波数における損失が大きく現れた。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1997 -1997 
    Author : 南 努, 松田 厚範, 忠永 清治, 辰巳砂 昌弘
     
    Li_2S-SiS_2系をベースとするオキシスルフィドガラスは、全固体リチウムイオン二次電池の電解質の有力な候補である。我々は、(1-y)[xLi_2S・(100-x)SiS_2]・y[xLi_2O・(100-x)P_2O_5](45SiNMR測定により、この組成域で硫黄と酸素の両方が配位したケイ素構造単位が多く存在することが観測された。このような構造単位の存在が、y=0.05の組成のガラスにおける高い安定性と高い伝導度の原因となっていることがわかった。 Li_2S-SiS_2系ガラスに対する、Li_3AlO_3およびLi_3AlS_3の添加の効果についても検討を行った。いずれの化合物を添加した場合においても、結晶化に対する安定性の向上および伝導の活性化エネルギーの減少がみられた。Li_3AlO_3を添加した系においては、硫黄と酸素の両方が配位したシリコンを含む構造単位が存在することがわかった。Li_3AlS_3を添加した系においては、^<27>AlNMRスペクトルによって、硫黄6配位のアルミニウムをもつ構造単位が多く存在することがわかった。この構造単位の存在が高いイオン伝導度に寄与していると考えられる。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1996 -1996 
    Author : 辰巳砂 昌弘, 忠永 清治
     
    本研究では、実用上重要な種々の酸化物系ニューガラスに対し、その融液から過冷却液体に至る幅広い粘度域での粘性係数の温度依存性を測定し、系や組成とFragilityの関係を明らかにした。一方で、様々な回析および分光学的手段を用いてそれぞれのガラスおよび融液の構造解析を行い、局所構造の組成依存性を検討した。本年度得られた成果は以下の通りである。 混合アニオン系として作製したSnX_2-P_2O_5(X=F,Cl)系ガラスでは、SnX_2含量の少ない組成ではEη/TgからみたFragilityは一定であるが、SnX_2含量の多い組成では、SnX_2含量の増加に伴ってFragilityは増加した。このとき、Fragilityが一定であったガラスでは局所構造が類似しているが、SnX_2含量の多い組成ではFragilityが大きいものほど、非架橋酸素の割合が多いピロリン酸グループやP-FやSn-Cl結合が多く存在することが確認された。このことから、イオン結合性の増加がFragilityの増加に寄与していると考えられる。 混合アルカリ系として作製したLi_2O-Na_2O-B_2O_3系ガラスでは、△CpからみたFragilityはほぼ一定であるが、Eη/Tgの観点からみるとアルカリを混合することでStrongになっていることが明らかとなった。この系の局所構造はアルカリ混合比によって変化せず、△CpからみたFragilityの傾向と一致した。 混合フォーマ-系として作製したNa_2O-SiO_2-B_2O_3系およびAgI-Ag_2MoO_4-Ag_2PO_<3.5>系ガラスではガラスフォーマ-を混合することによって△CpとEη/Tgの両方の観点からみてStrongになることが明らかになった。また、混合アルカリ系とは異なり、フォーマ-を混合することによって局所構造が大きく変化しており、△CpからみたFragilityと局所構造の間には密接な関係があることがわかった。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1996 -1996 
    Author : 南 努, 忠永 清治, 辰巳砂 昌弘
     
    本研究は、Li_2S-SiS_2系をベースとするLi_2S-SiS_2-Li_4SiO_4系オキシスルフィド系ガラスのイオン伝導度および熱的安定性における混合アニオン効果に着目し、このガラスの構造解析を行うことによりこの効果の本質的理解を深めながら応用展開することを目的としている。ここでは、このような系のガラスの高いイオン伝導性および優れた熱的安定性とガラス構造の関係について明らかにした。本年度得られた成果は以下の通りである。 1)^<29>Si MAS-NMR測定の結果から、ベースガラスに少量のLi_4SiO_4を添加すると、硫黄と酸素の両方の配位したケイ素がガラス中に多量に存在することがわかった。一方、多量のLi_4SiO_4を添加すると、このようなケイ素は減少した。 2)X線光電子スペクトルの結果から、少量のLi_4SiO_4を添加したガラス中では、硫黄は非架橋状態、酸素は架橋状態で主に存在し、多量に添加するとS^<2->や非架橋酸素が多く存在することが明らかになった。 3)5mol%のLi_4SiO_4を添加したガラス中には非架橋硫黄、架橋酸素が主に存在し、これらはリチウムイオンをトラップしにくいために、このガラスは高い伝導性を示すものと考えられる。さらに添加するとリチウムイオンをより強くトラップすると考えられるS^<2->や非架橋酸素の割合が増加するため、ガラスの伝導性は低下すると解釈することができる。 4)5mol%のLi_4SiO_4を添加したガラスは広い電位領域において高い電気化学的安定性を示すが、これは、このガラス中ではアニオン種の酸化反応の速度が非常に遅く、実際に酸化されるまでに大きな過電圧が生じるためと考えられる。20mol%のLi_4SiO_4を添加したガラス中では、S^<2->が多く存在し、これが電気化学的に酸化されることにより、ガラスの電気化学的安定性が低下するものと考えられる。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1995 -1995 
    Author : 南 努, 忠永 清治, 辰巳砂 昌弘
     
    本研究は、安定でイオン伝導性の高いガラス材料を設計する場合、必ずしも均質ガラスである必要はなく、伝導性の高いガラス相と安定性の高いガラス相を組み合わせた分相ガラスも視野に入れるべきであるという立場に立ち、不均質構造を有する新しい超イオン伝導ガラスを創製すべく、その基礎的検討を推進するものである。本研究で得られた成果を以下に示す。 1 AgI-Ag_2O-B_2O_3系超急冷試料の微細組織と組成の関係を調べた。その結果、通常のアイロンプレス法で作製できる組成のガラスは均質であるのに対し、超急冷法でのみ得られるAgI含量の多い組成のガラスは、基本的に不均質な組織を有していることが分かった。また、このような不均質ガラスの得られる組成域よりもわずかにAgI含量の多い組成域でα-AgIが常温凍結できることが分かった。 2 AgI-Ag_2O-B_2O_3系超急冷却試料のイオン伝導度と組成の関係を検討した。不均質ガラスの伝導度は、通常の均質超イオン伝導ガラスよりも高く、α-AgI常温凍結複合体よりも低い値を示した。また、均質ガラスにおいては、測定温度域内でArrhenius式に従うのに対し、不均質ガラスにおいては270K付近で折れ曲がりがみられた。この折れ曲がりは、α-AgI常温凍結複合体において明確にみられるAg^+イオンの秩序-無秩序転移に由来する伝導度異常に関係したものと考えられる。 3 AgI-Ag_2O-B_2O_3系において、不均質ガラスが、通常の均質ガラス生成域とα-AgI常温凍結複合体生成域の間の組成域で生成することから、このガラスはAgIに富むガラス相がAgIの少ないガラス相中に分散した分相ガラスと考えられる。またこのうち、AgIに富むガラス相は、均質ガラス中に存在すると考えられているAgI類似のクラスターがAgI濃度の増加の伴い成長したものではないかと考えられる。
  • 日本学術振興会:科学研究費助成事業 奨励研究(A)
    Date (from‐to) : 1995 -1995 
    Author : 忠永 清治
     
    ゾル-ゲル法は、各種基板に酸化物薄膜をコーティングする非常に有効な手段であるが、コーティングを行う基板としては、ガラス、セラミックス金属など高温での熱処理に耐えられるものが使われてきており、高分子フィルムのような耐熱性の小さい基板への無機膜のコーティングの研究はほとんど行われていない。本研究ではゾル-ゲル法によって、透明高分子フィルムであるナイロン-6フィルムに柔軟性のある無機-有機複合体薄膜をコーティングすることによって、高分子および無機膜両方の特性を兼ね備えた新しい材料を開発することを目的として行ったものである。得られた成果を以下に示す。 1.ビニルトリエトキシシランを原料とし、ビニル基をAIBNを開始剤としてアルゴン雰囲気下でラジカル重合させることによって、無機-有機複合体の前駆体である、ポリビニルトリエトキシシラン(PVTES)が合成できることがわかった。 2.PVTESもしくはPVTES-Si(OC_2H_5)_4系を出発原料として加水分解重縮合させた溶液をコーティング溶液とすることによってナイロン-6基板およびPET基板に均一なクラックのない無機-有機複合体薄膜を形成することができた。 3.得られた無機-有機複合体薄膜の鉛筆硬度測定をおこなったところ、PVTES-Si(OC_2H_5)_4系、およびPVTES単成分いずれの系においても150℃の熱処理によって9Hの硬度を示し、耐摩耗性に優れていることがわかった。また、ダイナミック硬度測定では、出発原料中のSi(OC_2H_5)_4の割合が増加するにつれて膜の微小硬度は増大した。 4.原子間力顕微鏡観察により、この無機-有機複合体薄膜の表面は1nm以下の凹凸しか存在しない極めて平滑な表面を持つことがわかった。
  • Japan Society for the Promotion of Science:Grants-in-Aid for Scientific Research
    Date (from‐to) : 1994 -1995 
    Author : MINAMI Tsutomu, KONDO Shigeo, TANAHASHI Ichiro, MACHIDA Nobuya, TADANAGA Kiyoharu, TATSUMISAGO Masahiro
     
    (1) New composite materials in which alpha-Agl was frozen in the superionic conducting glasses exhibited extremely high ion conductivities of about 10^<-2> - 10^<-1> Scm^<-1> at room temperature. (2) Kinetics for nucleation and growth of alpha-Agl crystals in Agl-based silver orthoborate glasses were studied by isothermal and nonisothermal measurmentsby DSC.A constant number of nuclei of alpha-Agl precipitated in a glass matrix grew three-dimensionally. (3) Composite silica gels containing HC10_4, WPA,H_2SO_4, or H_3PO_4 were prepared by the sol-gel method. The conductivities of the silica gels doped with the acid above ranged 10^<-4>-10^<-1> Scm^<-1>. (4) In the EC cell using HC10_4-doped silica gel film as a solid electrolyte remarkable coloration was observed when d.c. voltage was applied. (5) A conduction path of proton may be formed in the acid-doped silica gel structure and the interaction between the conduction paths and the silanol groups would affect the conductivities. The smaller interaction probably reslults in the higher proton conduction of the doped silica gel 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) : 1994 -1994 
    Author : 忠永 清治
     
    ゾル-ゲル法は、各種基板に酸化物薄膜をコーティングする非常に有効な手段であるが、コーティングを行う基板としては、ガラス、セラミックス金属など高温での熱処理に耐えられるものが使われてきており、高分子フィルムのような耐熱性の小さい基板への無機膜のコーティングの研究はほとんど行われていない。本研究ではゾル-ゲル法によって、透明高分子フィルムであるナイロン-6フィルムの酸化物薄膜をコーティングを行い、その特性を明らかにすることを目的として行ったものである。得られた成果を以下に示す。 1.4官能アルコキシドであるテトラエトキシシラン(TEOS)を原料を用いた場合にはコーティング膜はクラックを生じたが、出発原料に3官能アルコキシドであるメチルトリエトキシシラン(MTES)を加えることによってクラックのない均一な薄膜をコーティングできることがわかった。 2.シリカ系薄膜をコーティングしたナイロン-6基板について水蒸気透過速度を測定したところ、コーティングによって透過速度を抑制できることがわかった。組成依存性については、MTESに対するTEOSの比が大きくなるにつれてより抑制できることがわかった。 3.シランカップリング剤であるγ-アミノプロピルトリエトキシシランを加水分解した溶液でナイロン-6基板を前処理し、その後シリカ系のコーティングを行うと、コーティングフィルムとナイロン-6フィルムの密着性が向上した。また、水蒸気透過速度も抑制されることが明かとなった。 4.コーティング薄膜に紫外線を照射することによって、コーティング膜の緻密化が起こり、水蒸気透過速度も若干抑えられることがわかった。また、コーティング膜と基板の密着性がかなり改善された。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1993 -1994 
    Author : 峠 登, 忠永 清治
     
    ゾル-ゲル法において金属アルコキシドをβ-ジケトンで化学修飾すると、加水分解反応が抑制されると同時に、生成するゲル膜が光感応性を示すようになり、薄膜の微細加工が可能となる。本研究は、化学修飾されたゲル膜の光分解を利用した薄膜の作製と微細加工、および生成する薄膜の特性評価を目的として行ったものであり、以下の成果を得た。 (1)^<27>Al NMRから、Al-ブトキシドをアセト酢酸エチルEAcAcで化学修飾すると、Alが6配位された構造単位が生成し、前駆体の大部分は4配位された1個のAlと6配位された2個のAlから成る三量体を形成していることが明らかとなった。また、AlブトキシドのAlは、イソプロピルアルコール中では4配位であるが、ジアセトンアルコール中では5配位をとっていた。 (2)アセチルアセトンAcAcまたはベンゾイルアセトンBzAcで化学修飾されたZr-、Ti、またはAl-ブトキシドから生成スルゲル膜に紫外線を照射すると、ゲル膜中のキレート環が分解され、同時に酸やアルコールに対する溶解度が変化することを見いだした。 化学修飾されたゲル膜への紫外線照射によって生じる、ゲル膜の溶解度の変化を利用して、ZrO_2、TiO_2、およびAl_2O_3薄膜の微細パタ-ニングプロセスを開発した。 AcAcで化学修飾したZr-およびTi-ブトキシド、ならびに酢酸鉛三水和物、および硝酸ランタンを原料として、PZTおよびPLZT強誘電体薄膜を作製した。Pt基板上に形成したゲル膜を700℃で熱処理することにより、組成ずれのないペロブスカイト単一相の薄膜が得られた。 BzAcで化学修飾されたZr-およびTi-ブトキシド、ならびに酢酸鉛三水和物を原料として得られるゲル膜に紫外線を照射すると、ゲル膜のアルコールに対する溶解度が減少し、この現象を利用してPZT強誘電体のような多成分系薄膜もパタ-ニングできることを実証した。
  • 日本学術振興会:科学研究費助成事業
    Date (from‐to) : 1992 -1994 
    Author : 南 努, 忠永 清治, 辰巳砂 昌弘, 峠 登
     
    α-AgIは、147°C以上で安定な「超イオン伝導体」であるが、147°C以下では伝導性の低いβ-AgIに転移してしまう。ところが、AgIを極端に多量に含む融液を10^5K/s以上の冷却速度で超急冷すると、α→β転移が阻止され、常温でα-AgIがガラスマトリックス中に凍結された一種の複合体が得られることがわかった。本研究では、このようなα-AgI常温凍結複合体のキャラクタリゼーションを行うとともに、凍結条件を最適化し、また凍結機構を明らかにした。得られた成果を以下に示す。 (1)AgIを多量に含むAgI-Ag_2O-M_xO_y(M_xO_y=B_2O_3,GeO_2,P_2O_5,Mo0_3,WO_3,V_2O_5)系の融液を超急冷することにより、ガラス生成域よりわずかにAgI含量の多い組成域において、α-AgIをガラスマトリックス中に常温で凍結できることがわかった。 (2)ガラス転移温度(Tg)の高いガラスマトリックスの方が、AgIのα→β転移抑制効果が大きく、容易にα-AgIが凍結できた。 (3)α-AgIを常温凍結した複合体は、室温で極めて高いイオン伝導度を示すことがわかった。また、伝導の活性化エネルギーは、α-AgIと超イオン伝導ガラスの中間の値を示した。 (4)α-AgI常温凍結複合体には、数十nmの粒径を持つα-AgI微粒子がガラスマトリックス中に均一に分散して存在することがわかった。また、β-AgIの析出した試料には、数百nm程度の粒径を持つ比較的大きなβ-AgI結晶が密に存在することがわかった。 (5)常温凍結されたα-AgIは、周囲のマトリックスガラスから応力を受け、歪んだ状態で存在していることがわかった。 (6)α-AgI常温凍結試料中のα-AgI結晶格子の不均一歪は、室温以下においてさらに増大することがわかった。また、それと同時に、低温になると、銀イオンの部分的な秩序化が起こっていることがわかった。
  • 日本学術振興会:科学研究費助成事業 奨励研究(A)
    Date (from‐to) : 1993 -1993 
    Author : 忠永 清治
     
    エアロゲルは、ゾル-ゲル法で作製したゲルを超臨界乾燥することによって得られる気孔率90%以上の極めて密度の小さい多孔質体であるが、これまではおもにシリカ単成分のみの研究が行われ、多成分系のゲルを容易に作製できるというゾル-ゲル法の特徴を活かした多成分系のエアロゲルの作製はほとんど報告されていない。本研究は、ゾル-ゲル法によって作製したSiO_2-Al_2O_3 2成分系ゲルを超臨界乾燥させることによってエアロゲルを作製し、その特性を評価することを目的として行ったものである。得られた成果を以下に示す。 1.Al_2O_3成分の原料としてAl(O-Bu)_3用いる際、加水分解速度を制御するためにアセト酢酸エチルによって化学修飾することが効果的であった。この化学修飾されたAl-アルコキシドの加水分解挙動を調べたところ、ゲル化点においても約70%のアセト酢酸エチルが配位したままであることがわかった。 2.化学修飾されたAl(O-Bu)_3とテトラエトキシシランを原料とし、溶媒としてイソプロピルアルコールを用いてウェットゲルを作製した。このウェットゲルを、270℃、12MPaの条件で超臨界乾燥を行うことによって、エアロゲルを作製することができた。このエアロゲルは、半透明、密度約0.17g/cm^3、収縮率約20%であった。 3.種々のSi/Al=0.2付近で極大を示すことがわかった。Si/Al=0.17の場合、800℃で432m^2/g、1000℃で296m^2/gという値が得られ、高温で熱処理しても大きな比表面積を維持していることがわかった。 4.窒素吸着法によって細孔分布を求めたところ、100-200A程度の比較的大きな細孔が多く存在することがわかった。

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