Updated on 2022/03/29

写真a

 
SAITO Genki
 
Organization
Graduate School of Engineering Materials Physics 2 Assistant Professor
Graduate School
Graduate School of Engineering
Undergraduate School
School of Engineering Physical Science and Engineering
Title
Assistant Professor
External link

Degree 1

  1. Doctor (Engineering) ( 2014.3   Hokkaido University ) 

Research Interests 7

  1. Electron Microscopy

  2. Phosphor

  3. crystal structure

  4. Combustion synthesis

  5. Solution Plasma

  6. Material Science

  7. Nanoparticles

Research Areas 2

  1. Nanotechnology/Materials / Metallic material properties

  2. Nanotechnology/Materials / Inorganic materials and properties

Current Research Project and SDGs 2

  1. 電子顕微鏡による構造解析に関する研究

  2. 金属材料の析出物に関する研究

Research History 4

  1. Nagoya University   Graduate School of Engineering Materials Physics   Assistant Professor

    2020.10

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    Country:Japan

  2. Hokkaido University   Faculty of Engineering, Division of Materials Science and Engineering   Designated assistant professor

    2017.8 - 2020.9

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    Country:Japan

  3. Hokkaido University   Faculty of Engineering Center for Advanced Research of Energy and Materials

    2014.10 - 2017.7

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    Country:Japan

  4. 日本学術振興会特別研究員

    2013.4 - 2014.9

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    Country:Japan

Education 2

  1. Hokkaido University   Faculty of Engineering   Doctor's course

    2011.4 - 2014.3

  2. Hokkaido University   Faculty of Engineering Hokkaido   Master's course

    2009.4 - 2011.3

Professional Memberships 4

  1. THE IRON AND STEEL INSTITUTE OF JAPAN

  2. THE JAPAN INSTITUTE OF METALS

  3. THE JAPANESE SOCIETY OF MICROSCOPY

  4. THE SOCIETY OF POWDER TECHNOLOGY, JAPAN

Awards 8

  1. 第30回 日本金属学会 奨励賞

    2020.9  

  2. 日本金属学会・日本鉄鋼協会両支部合同サマーセッション 佐藤矩康賞

    2019.7  

  3. 2016年度 APT賞 (APT Distinguished Paper Award)

    2017.4   粉体工学会  

    Genki Saito, Chunyu Zhu, Cheng-Gong Han, Norihito Sakaguchi, Tomohiro Akiyama

  4. 日本顕微鏡学会 北海道支部 支部長賞

    2016.12  

  5. 日本金属学会・日本鉄鋼協会両支部合同サマーセッション 佐藤矩康賞

    2016.7  

  6. Postar Award

    2012.9   The Japan Institute of Metals  

    Genki Saito

  7. 2010 年度春期研究発表会 ベストプレゼンテーション賞

    2010.5   粉体工学会  

    齊藤 元貴

  8. Postar Award

    2009.9   The Japan Institute of Metals  

    Genki Saito

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Papers 59

  1. Sr-Doped Ca2AlMnO5 + δ for Energy-Saving Oxygen Separation Process Invited Reviewed

    Keita Tanahashi , Yusei Omura , Hidekazu Naya , Kaho Miyazaki , Genki Saito , Yuji Kunisada , Norihito Sakaguchi , Takahiro Nomura

    ACS Sustainable Chemistry & Engineering   Vol. 9 ( 28 ) page: 9317 - 9326   2021.7

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1021/acssuschemeng.1c02077

  2. Effects of cooling rate after hot forging on precipitation of fine particles during subsequent normalizing and austenite grain growth during carburization of Al- and Nb-microalloyed case-hardening steel Reviewed

    Genki Saito, Norihito Sakaguchi, Munekazu Ohno, Kiyotaka Matsuura, Masayoshi Takeuchi, Taichi Sano, Koki Minoguchi, Takuya Yamaoka

    ISIJ International   Vol. 61 ( 6 ) page: 1964 - 1970   2021.6

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2355/isijinternational.ISIJINT-2020-743

  3. In-situ observation of abnormal grain growth in a low-alloyed carbon steel using SEM-EBSD Reviewed

    Genki Saito, Tianglong Zhang, Norihito Sakaguchi, Munekazu Ohno, Kiyotaka Matsuura, Masayoshi Takeuchi, Taichi Sano, Koki Minoguchi, Takuya Yamaoka

    Materialia   Vol. 15   page: 100985 - 100985   2021.3

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Elsevier BV  

    DOI: 10.1016/j.mtla.2020.100985

  4. Faster generation of nanoporous hematite ore through dehydration of goethite under vacuum conditions Reviewed

    A. Kurniawan, G. Saito, T. Nomura, T. Akiyama

    ISIJ International   Vol. 61 ( 1 ) page: 493 - 497   2021.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2355/isijinternational.ISIJINT-2020-403

  5. Rapid oxygen storage and release with Brownmillerite-structured Ca2AlMnO5 Reviewed

    A. Sato, G. Saito, K. Abe, Y. Kunisada, N. Sakaguchi, T. Akiyama, T. Nomura

    Journal of Alloys and Compounds   Vol. 851 ( 15 ) page: 156817   2021.1

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.jallcom.2020.156817

  6. Effects of Concentrations of Micro-alloying Elements and Hot-forging Temperature on Austenite Grain Structure Formed during Carburization of Case-hardening Steel Reviewed

    Genki Saito, Norihito Sakaguchi, Munekazu Ohno, Kiyotaka Matsuura, Masayoshi Takeuchi, Taichi Sano, Koki Minoguchi, Takuya Yamaoka

    ISIJ International   Vol. 60 ( 11 ) page: 2549 - 2557   2020.11

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Iron and Steel Institute of Japan  

    DOI: 10.2355/isijinternational.isijint-2020-123

  7. Effects of fine precipitates on austenite grain refinement of micro-alloyed steel during cyclic heat treatment Reviewed

    G. Saito, N. Sakaguchi, M. Ohno, K. Matsuura, M. Takeuchi, T. Sano, K. Minoguchi, T. Yamaoka

    ISIJ International   Vol. 59 ( 11 ) page: 2098 - 2104   2019.11

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2355/isijinternational.ISIJINT-2019-153

  8. Synthesis of AlN particles via direct nitridation in a drop tube furnace Reviewed

    G. Saito, T. Senda, K. Abe, T. Nomura, T. Akiyama

    Journal of the Ceramic Society of Japan   Vol. 127 ( 11 ) page: 810 - 817   2019.11

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2109/jcersj2.19110

  9. Austenite memory during reverse transformation of steels at different heating rates Reviewed

    G. Saito, T. Nakayama, N. Sakaguchi, M. Ohno, K. Matsuura, M. Takeuchi, T. Sano, K. Minoguchi, T. Yamaoka

    Materialia   Vol. 7 ( September ) page: 100409-11 - 100409-9   2019.9

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.mtla.2019.100409

  10. Solution Combustion Synthesis of Functional Powders Invited

    Genki Saito, Chunyu Zhu, Tomohiro Akiyama

    J. Soc. Powder Technol., Japan   Vol. 56   page: 267 - 271   2019.5

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    Language:Japanese   Publishing type:Research paper (scientific journal)  

    DOI: 10.4164/sptj.56.267

  11. Crystalline Evaluation of Size-Controlled Silicon and Silicon Oxide Nanoparticles Produced by Solution Plasma Discharge Reviewed

    H. Sasaki, G. Saito, N. Sakaguchi, R. Ota, H. Takahashi

    MATERIALS TRANSACTIONS   Vol. 60 ( 5 ) page: 688 - 692   2019.3

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.2320/matertrans.MC201810

  12. Combustion synthesis of AlN doped with carbon and oxygen Reviewed

    G. Saito, Y. Kunisada, T. Watanabe, X. Yi, T. Nomura, N. Sakaguchi, T. Akiyama

    Journal of the American Ceramic Society   Vol. 102   page: 524 - 532   2019

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1111/jace.15947

  13. Sr Substitution Effects on Atomic and Local Electronic Structure of Ca2AlMnO5+δ Reviewed

    Y. Kunisada, G. Saito, K. Hayami, T. Nomura, N. Sakaguchi

    Surface and Interface Analysis   Vol. 51   page: 65 - 69   2019

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1002/sia.6549

  14. Combustion synthesis of YAG:Ce phosphors via the thermite reaction of aluminum Reviewed

    Junpei Ohyama, Chunyu Zhu, Genki Saito, Miki Haga, Takahiro Nomura, Norihito Sakaguchi, Tomohiro Akiyama

    Journal of Rare Earths   Vol. 36 ( 3 ) page: 248 - 256   2018.3

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    Authorship:Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:Chinese Society of Rare Earths  

    Cerium-doped yttrium aluminum garnet (YAG:Ce) as a yellow phosphor for white light-emitting diodes (LEDs) was synthesized via a facile combustion method using Y2O3, CeO2, Al2O3, Al, and NaClO4 as raw materials. The combustion synthesis approach utilizes the strong exothermic oxidation of aluminum to realize a self-sustaining reaction. In this study, we investigated the effects of the ratios of Al2O3 to Al, fluxes, and coprecipitated materials as raw materials on the luminescence properties of the synthesized YAG:Ce phosphors. When the amount of Al2O3 x is varied, the combustion reaction proceeds at x ≤ 1.8, with x = 1.725 being the optimum condition for producing a high-performance product. When 5 wt% BaF2 is added, the luminescence intensity is significantly improved owing to a decrease of YAP (YAlO3) formation with improved uniformity. However, the addition of CaF2 and NaF does not improve the luminescence properties. To suppress the segregation of CeO2, we used the coprecipitated material Y2O3–CeO2 as a raw material. Unlike with separate addition of Y2O3 and CeO2, Ce ions are uniformly distributed in the coprecipitated material, resulting in improved luminescence properties. The combination of BaF2 and coprecipitated material significantly improves the internal quantum efficiency to 83.0%, which is close to that of commercial phosphors.

    DOI: 10.1016/j.jre.2017.06.014

    Scopus

  15. Development of a microencapsulated Al-Si phase change material with high-temperature thermal stability and durability over 3000 cycles Reviewed

    N. Sheng, C. Zhu, G. Saito, T. Hiraki, M. Haga, Y. Hasegawa, H. Sakai, T. Akiyama, T. Nomura

    Journal of Materials Chemistry A   Vol. 6   page: 18143 - 18153   2018

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1039/C8TA04708A

  16. Microencapsulation of eutectic and hyper-eutectic Al-Si alloy as phase change materials for high-temperature thermal energy storage Reviewed

    T. Nomura, J. Yoolerd, N. Sheng, H. Sakai, Y. Hasegawa, M. Haga, G. Saito, T. Akiyama

    Solar Energy Materials and Solar Cells   Vol. 187   page: 255 - 262   2018

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    Language:English   Publishing type:Research paper (scientific journal)  

    DOI: 10.1016/j.solmat.2018.08.001

  17. Combustion synthesis of Ca-alpha-SiAlON:Eu2+ phosphors with different Ca concentrations and diluent ratios Reviewed

    Genki Saito, Yuji Kunisada, Norihito Sakaguchi, Takahiro Nomura, Tomohiro Akiyama

    CERAMICS INTERNATIONAL   Vol. 43 ( 15 ) page: 12396 - 12401   2017.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCI LTD  

    Yellow Ca-alpha-SiAlON:Eu2+ phosphors for white light-emitting diodes (LEDs) were synthesized by a facile combustion synthesis method using CaO, Eu2O3, alpha-Si3N4, Si, and Al as raw materials. Ca concentrations and diluent ratios were optimized to improve their luminescence properties. The lattice constant and luminescence properties improved as x increased from 0.4 to 1.2 in Ca(x)Si(12-(m+n))Al(m+n)OnN(16-n):En(0.06). The optimum value was x = 1.2. Scanning transmission electron microscopy combined with energy dispersive X-ray analysis detected segregation of Ca and Eu at grain boundaries, which decreased luminescence behavior in the x = 1.4 sample. The influence of Si and Si3N4 diluents was investigated by varying the diluent ratio phi = (CaO + Eu2O3 + alpha-Si3N4)/(CaO + Eu2O3 + a-Si3N4 + Al + Si). Changes in temperature and flame propagation speed were measured during combustion synthesis using two thermocouples. When phi, was less than 0.5, the combustion temperature exceeded 1600 degrees C and the synthesized material contained an amount of the high-temperature beta-SiAlON phase. At phi > 0.7, the reaction temperature fell below 1200 degrees C, and unreacted raw materials remained. The optimum value of phi was 0.6. The internal quantum efficiency of the product synthesized at x = 1.2 and (I, = 0.6 was approximately 35% under 450-nm excitation. According to electron probe X-ray microanalysis, composition varied within individual synthesized particles, which may explain the decrease in emission behavior relative to a commercial product.

    DOI: 10.1016/j.ceramint.2017.06.106

    Web of Science

  18. Effects of Al particle size and nitrogen pressure on AlN combustion synthesis Reviewed

    Ayako Hiranaka, Xuemei Yi, Genki Saito, Jing Niu, Tomohiro Akiyama

    CERAMICS INTERNATIONAL   Vol. 43 ( 13 ) page: 9872 - 9876   2017.9

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCI LTD  

    This study investigates the combustion synthesis of AlN fibers using an NH4Cl additive and reports the effects of Al particle size (3, 30, and 180 mu m) and N-2 pressure (0.10, 0.25, and 0.50 MPa) on the purity and morphology of AlN fibers. The combustion temperature was directly measured during the synthesis to elucidate the formation mechanism of the AlN fibers. The phase purity and morphology of the products were studied using X-ray diffraction and scanning electron microscopy, respectively. When the particle size of Al was reduced from 180 to 3 mu m, the purity of the AlN product increased significantly owing to the large reaction area, which increased the combustion temperature. Furthermore, lower N-2 pressures enhanced the formation of AlN nanofibers due to the accelerated gasification of Al. The optimum values of the particle size of Al and the N-2 pressure for the formation of high-purity MN nanofibers were found to be 3 mu m and 0.10 MPa, respectively.

    DOI: 10.1016/j.ceramint.2017.04.170

    Web of Science

  19. Microencapsulated phase change materials with high heat capacity and high cyclic durability for high-temperature thermal energy storage and transportation Reviewed

    Takahiro Nomura, Nan Sheng, Chunyu Zhu, Genki Saito, Daiki Hanzaki, Takehito Hiraki, Tomohiro Akiyama

    APPLIED ENERGY   Vol. 188 ( 15 ) page: 9 - 18   2017.2

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    Latent heat storage (LHS) technology employing phase change materials (PCMs) has received great attention as an alternative to conventional solid sensible heat storage (SHS) for future high-temperature energy utilisation systems. In this study, we report the synthesis of a core-shell type microencapsulated PCM (MEPCM) consisting of AI-25 wt% Si microspheres (mean diameter of 363 pm and melting temperature of 577 degrees C) as the core (PCM) and Al2O3 as the shell. The MEPCM was prepared in two steps involving (1) the formation of an AlOOH precursor shell on the PCM microspheres by a hydroxide precipitation process in hot water and (2) heat-oxidation treatment in an O-2 atmosphere to form a stable Al2O3 shell. In particular, the effects of heat oxidation temperature on the shell morphology, shell crystal structure, mechanical strength, heat capacity, and cyclic durability of the prepared MEPCMs were examined. The resultant MEPCM is composed of a stable alpha-Al2O3 shell and Al-25 wt% Si core with an effective void inside the core to allow for volume expansion of the PCMs during solid-liquid phase transitions. The heat capacity measured for this material is five times higher than that of conventional solid SHS materials. Additionally, the MEPCM exhibits excellent durability up to 300 heating and cooling cycles under oxygen atmosphere. Consequently, it can potentially be used in the next-generation LHS-based high-temperature thermal energy storage and transportation systems. (C) 2016 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.apenergy.2016.11.025

    Web of Science

  20. Atomic and Local Electronic Structures of Ca(2)AIMnO(5+delta) as an Oxygen Storage Material Reviewed

    Genki Saito, Yuji Kunisada, Kazuki Hayami, Takahiro Nomura, Norihito Sakaguchi

    CHEMISTRY OF MATERIALS   Vol. 29 ( 2 ) page: 648 - 655   2017.1

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER CHEMICAL SOC  

    We investigated the atomic and local electronic structures of Ca(2)AIMnO(5+delta) to assess its potential as an oxygen storage material. High-angle annular dark-field scanning transmission electron microscopy was used to investigate structural changes in the material during oxygen storage. We found that the AlO4 tetrahedra convert to AlO6 octahedra during such a process. According to the Mn L-edge electron energy-loss near-edge structure (ELNES) measurements, the Mn oxidation state increased from +3 to +4 on oxygen storage. The observed site-resolved oxygen K-ELNES and first-principles electronic structure calculations showed that each nonequivalent oxygen site has different characteristics, corresponding to local chemical bonding and oxygen intake and release. For Ca(2)AIMnO(5), the prepeak intensity was higher at MnO6 octahedral sites, indicating covalent bonding between the oxygen and Mn atoms. After oxygen storage, the ELNES spectra revealed that the Jahn Teller distortion of the Mn sites was suppressed by the increase in the Mn oxidation state; furthermore, the spectra indicate that Mn octahedron shrank in the z-direction, accompanied by an increase in Mn O covalent bonding, thus providing sufficient space to form octahedral AlO6. Consequently, we found that the reversible oxygen storage ability is related to the canceling of the volume changes of the Mn and Al octahedra. The electrons in Mn 3d orbitals play an important role in this structural change.

    DOI: 10.1021/acs.chemmater.6b04099

    Web of Science

  21. Enhanced cycling performance of surface-doped LiMn2O4 modified by a Li2CuO2-Li2NiO2 solid solution for rechargeable lithium-ion batteries Reviewed

    Cheng-Gong Han, Chunyu Zhu, Genki Saito, Nan Sheng, Takahiro Nomura, Tomohiro Akiyama

    ELECTROCHIMICA ACTA   Vol. 224 ( 10 ) page: 71 - 79   2017.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    A series of surface-doped LiMn2O4 samples modified by a Li2CuO2-Li2NiO2 solid solution were synthesized using a simple and facile sol-gel method to achieve the enhanced cycling performance, especially at elevated temperatures. The corresponding phase structure and morphology were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The modified layer on the surface of LiMn2O4 particles, featuring a LiNi delta Mn2-delta O4-like phase, together with a Li2CuO2-Li2NiO2 solid solution, as confirmed by XRD and transmission electron microscopy (TEM), plays a key role in alleviating the dissolution of manganese, thus enhancing the cycling performance and rate capability relative to bare LiMn2O4. The 0.5 wt.%-modified LiMn2O4 sample delivers a discharge capacity of 113 mAh g(-1), and a capacity retention of 93.2% following 300 cycles at 1C and 25 degrees C, which is higher than the values of 96 mAh g(-1) and 81.2% for bare LiMn2O4. In addition, at 55 degrees C, a capacity retention of 81.2% at 1C is obtained for the 0.5 wt.%-modified LiMn2O4 sample after 200 cycles, compared to 70.0% for bare LiMn2O4. Modifying the surface of the latter by a LiNi delta Mn2-delta O4-like phase mixed with a Li2CuO2Li2NiO2 solid solution, is an effective strategy for improving electrochemical properties. (C) 2016 Published by Elsevier Ltd.

    DOI: 10.1016/j.electacta.2016.12.041

    Web of Science

  22. Estimating the Spatial Distribution of Ca Dopants in alpha-SiAlON by Statistical Analysis of HAADF-STEM Image Reviewed

    Norihito Sakaguchi, Fuuta Yamaki, Genki Saito, Yuji Kunisada

    MATERIALS TRANSACTIONS   Vol. 58 ( 10 ) page: 1341 - 1345   2017

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:JAPAN INST METALS  

    We analyzed the spatial distribution of Ca dopants in alpha-SiAlON by using a statistical approach that analyzed a high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) image. By evaluating the image intensity of each atomic column, we found that the intensity deviation of columns with Ca atoms was twice that of other atomic columns. The results of HAADF-STEM image simulation suggested that there was a long-range repulsive interaction along the [0001] direction between pairs of Ca atoms in the same Ca column. Moreover, correlation of image intensities in neighboring Ca columns suggested the existence of a short-range repulsive force between first-nearest-neighbor Ca atoms. The origin of such anisotropic interactions between pairs of Ca atoms will be discussed.

    DOI: 10.2320/matertrans.MAW201705

    Web of Science

  23. Facile synthesis of MnO/carbon composites by a single-step nitrate-cellulose combustion synthesis for Li ion battery anode Reviewed

    Chunyu Zhu, Cheng-gong Han, Genki Saito, Tomohiro Akiyama

    JOURNAL OF ALLOYS AND COMPOUNDS   Vol. 689   page: 931 - 937   2016.12

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE SA  

    In this paper, a novel method is proposed to produce MnO/carbon composites, in which the MnO nanoparticles were embedded into a porous carbon matrix, by a single-step nitrate-cellulose combustion synthesis. The composition, structure and morphology of the composites were characterized by X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, thermogravimetric analysis, and scanning/transmission electron microscopy. The composites were used as lithium ion battery anodes to evaluate their electrochemical properties. The MnO/carbon composite with a proper carbon content showed enhanced cycling performance and capacity retention, which delivered a reversible capacity of 561 mAh g(-1) after 90 cycles at 0.2 A g(-1). The easy production and good electrochemical properties enables the composite to be a possible candidate as an anode alternative for high-performance lithium ion battery. (C) 2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2016.08.054

    Web of Science

    J-GLOBAL

  24. Twin formation in hematite during dehydration of goethite Reviewed

    Genki Saito, Yuji Kunisada, Takahiro Nomura, Norihito Sakaguchi, Tomohiro Akiyama

    PHYSICS AND CHEMISTRY OF MINERALS   Vol. 43 ( 10 ) page: 749 - 757   2016.11

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:SPRINGER  

    Twin formation in hematite during dehydration was investigated using X-ray diffraction, electron diffraction, and high-resolution transmission electron microscopy (TEM). When synthetic goethite was heated at different temperatures between 100 and 800 degrees C, a phase transformation occurred at temperatures above 250 degrees C. The electron diffraction patterns showed that the single-crystalline goethite with a growth direction of [001](G) was transformed into hematite with a growth direction of [100](H). Two non-equivalent structures emerged in hematite after dehydration, with twin boundaries at the interface between the two variants. As the temperature was increased, crystal growth occurred. At 800 degrees C, the majority of the twin boundaries disappeared; however, some hematite particles remained in the twinned variant. The electron diffraction patterns and high-resolution TEM observations indicated that the twin boundaries consisted of crystallographically equivalent prismatic (100) (010), and (10) planes. According to the total energy calculations based on spin-polarized density functional theory, the twin boundary of prismatic (100) screw had small interfacial energy (0.24 J/m(2)). Owing to this low interfacial energy, the prismatic (100) screw interface remained after higher-temperature treatment at 800 degrees C.

    DOI: 10.1007/s00269-016-0831-8

    Web of Science

  25. Estimating the dopant distribution in Ca-doped alpha-SiAlON: statistical HAADF-STEM analysis and large-scale atomic modeling Reviewed

    Norihito Sakaguchi, Fuuta Yamaki, Genki Saito, Yuji Kunisada

    MICROSCOPY   Vol. 65 ( 5 ) page: 400 - 406   2016.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:OXFORD UNIV PRESS  

    We investigated the dopant distribution in Ca-doped alpha-SiAlON by using high-angle annular dark-field scanning transmission electron microscopy and a multi-slice image simulation. Our results showed that the electron wave propagated by hopping to adjacent Si(Al) and N(O) columns. The image intensities of the Ca columns had wider dispersions than other columns. To estimate the Ca distribution in the bulk material, we performed a Monte Carlo atomic simulation of the alpha-SiAlON with Ca dopants. A model including a short-range Coulomb-like repulsive force between adjacent Ca atoms reproduced the dispersion of the intensity distribution of the Ca column in the experimental image.

    DOI: 10.1093/jmicro/dfw020

    Web of Science

  26. Salt-assisted combustion synthesis of Ca-alpha-SiAlON:Eu2+ phosphors Reviewed

    Genki Saito, Jing Niu, Xuemei Yi, Yuji Kunisada, Norihito Sakaguchi, Tomohiro Akiyama

    JOURNAL OF ALLOYS AND COMPOUNDS   Vol. 681 ( 5 ) page: 22 - 27   2016.10

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE SA  

    In this study, Ca-alpha-SiAlON:Eu2+ yellow phosphors for white light-emitting diodes (LEDs) were synthesized via a facile combustion synthesis method by using CaO, Eu2O3, Si, and Al as raw materials, while NaCl and Si3N4 were utilized as diluents to contain the combustion temperature. The concentration of Eu was varied, and the resulting changes in phase purity, photoluminescence properties, and thermal quenching were investigated. We observed that the increase in lattice constant depended on the amount of Al, while the Ca sites were partially substituted by Eu ions. The synthesized Ca-alpha-SiAlON: Eu2+ powders exhibited emission wavelength at 556-560 nm and high thermal stability, revealing high potential for application in white LEDs. (C)2016 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2016.04.211

    Web of Science

  27. Limonitic Laterite Ore as a Catalyst for the Dry Reforming of Methane Reviewed

    Keisuke Abe, Genki Saito, Takahiro Nomura, Tomohiro Akiyama

    ENERGY & FUELS   Vol. 30 ( 10 ) page: 8457 - 8462   2016.10

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER CHEMICAL SOC  

    We investigated four catalysts for the dry reforming of methane: three Ni-containing natural iron ores (LN, SN, and NN ores) and one Ni-supported ore (Ni-supported NN ore) to solve the problems about unused high-temperature waste heat and CO2 emission in the steel industry. The CO2 conversion ratio was highest for the LN ore (1.18 wt '% Ni), followed by Ni-supported NN (1.0 wt % Ni), SN (0.30 wt % Ni), and NN (0 wt % Ni) ores. The CO2 conversion ratio of the LN ore was much higher than that of the Ni-supported NN ore, despite the fact that they contained almost the same amount of Ni. This is because the LN ore had a higher surface area and a higher nickel dispersion. Transmission electron microscopy with energy dispersive X-ray spectroscopy revealed that Ni existed quite finely in the LN ore but existed as a larger particle (20 nm) in the Nisupported NN ore. Smaller Ni particles have a higher surface area, resulting in the higher catalytic performance of the LN ore. More CO2 and CH4 reacted and higher amounts of H-2 and CO were produced with the LN ore catalyst compared to the uncatalyzed reaction. The LN ore showed more reduction at higher temperatures, and metallic iron and nickel were produced above 1073 K; reduction did not progress past Fe3O4 at lower temperatures.

    DOI: 10.1021/acs.energyfuels.6b00940

    Web of Science

  28. Improved electrochemical performance of LiMn2O4 surface-modified by a Mn4+-rich phase for rechargeable lithium-ion batteries Reviewed

    Cheng-Gong Han, Chunyu Zhu, Genki Saito, Tomohiro Akiyama

    ELECTROCHIMICA ACTA   Vol. 209   page: 225 - 234   2016.8

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:PERGAMON-ELSEVIER SCIENCE LTD  

    The surface of spinel LiMn2O4 is modified with different quantities of a Mn4+-rich phase prepared by a facile sol-gel method to improve electrochemical properties at elevated temperatures. Impurity-free and uniform morphologies for the LiMn2O4 particles are demonstrated from the X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The Mn4+-rich phase modified on the surface of the LiMn2O4 alleviates the dissolution of manganese in the electrolyte, thus improving the cycling performance and rate capability relative to the bare LiMn2O4. 1 wt.%-modified LiMn2O4 delivers a capacity retention of 92.7% and a discharge capacity of 113.5 mAh g(-1) after 200 cycles at 1C and 25 degrees C, compared with that of 83.1%, and 100.8 mAh g(-1) for the bare LiMn2O4. In addition, after 100 cycles, a capacity retention of 88.6% at 1C is achieved for 1 wt.%-modified LiMn2O4 at 55 degrees C, which is higher than the 76.0% for the bare LiMn2O4. Furthermore, this sample shows the best rate capability among all samples. The Mn4+-rich phase is an appropriate candidate for modifying surfaces to suppress dissolution of manganese, thereby improving the electrochemical properties of LiMn2O4. (C) 2016 Elsevier Ltd. All rights reserved.

    DOI: 10.1016/j.electacta.2016.05.075

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  29. Solution combustion synthesis of porous Sn-C composite as anode material for lithium ion batteries Reviewed

    Genki Saito, Chunyu Zhu, Cheng-Gong Han, Norihito Sakaguchi, Tomohiro Akiyama

    ADVANCED POWDER TECHNOLOGY   Vol. 27 ( 4 ) page: 1730 - 1737   2016.7

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    In this study, a Sn-C composite material as anode material for lithium ion batteries was fabricated via MgO template-assisted solution combustion synthesis, in which the starting material was a gel containing Sn(NO3)(2), glycine (C2H5O2N) as the carbon source, and Mg(NO3)(2)center dot 6H(2)O for the template. After the combustion reaction, the generated MgO was removed from the carbon, and the Sn nanoparticles were dispersed into a porous carbon structure during the carbon reduction of SnO2 under calcination in N-2. The effects of ratios of glycine (n) and MgO (m) on the material phase, morphology, carbon content, and electrochemical properties were mainly investigated. At glycine (n) ratios of 2 and 3, the SnO2 phase was not fully reduced to Sn. With n > 3, a composite material of metallic Sn nanoparticles and carbon was synthesized, in which the ratio of carbon increased with increasing n. With increasing m, the porosity of the particles increased, resulting in enhanced cyclic stability owing to the buffer space provided by the porous structure of carbon. The composite material obtained at n = 4 and m = 4 exhibited the highest reversible capacity of 588 mA h/g after 100 discharge/charge cycles at a current rate of 0.5 A/g as compared to the 269 mA h/g observed for n = 4 and m = 2. (C) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

    DOI: 10.1016/j.apt.2016.06.004

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  30. MnO nanocrystals incorporated in a N-containing carbon matrix for Li ion battery anodes Reviewed

    Chunyu Zhu, Cheng-gong Han, Genki Saito, Tomohiro Akiyama

    RSC ADVANCES   Vol. 6 ( 36 ) page: 30445 - 30453   2016

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    In this study, MnO nanocrystals incorporated in a N-containing carbon matrix were fabricated by the facile thermal decomposition of manganese nitrate-glycine gels. MnO/C composites with different carbon contents were prepared by controlling the initial ratio of manganese to glycine. The composition, phase structure and morphology of the composites were characterized by X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, scanning and transmission electron microscopy, and thermogravimetric analysis. The results indicated that MnO nanocrystals were uniformly embedded in the N-doped carbon matrix. The carbon matrix could effectively enhance the electrical conductivity of MnO and alleviate the strain arising from the discharge/charge cycling. The composite materials exhibited high discharge/charge capacities, superior cycling performance, and excellent rate capability. A high reversible capacity of 556 mA h g(-1) was obtained after 110 cycles of discharging and charging at a current rate of 0.5 A g(-1). Even at a high current rate of 3 A g(-1), the sample still delivered a capacity of around 286 mA h g(-1). The easy production and superior electrochemical properties enables the composites to be a promising candidate as an anode alternative for high-performance lithium-ion batteries.

    DOI: 10.1039/c6ra00571c

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  31. Optimization of the Dehydration Temperature of Goethite to Control Pore Morphology Reviewed

    Genki Saito, Takahiro Nomura, Norihito Sakaguchi, Tomohiro Akiyama

    ISIJ INTERNATIONAL   Vol. 56 ( 9 ) page: 1598 - 1605   2016

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:IRON STEEL INST JAPAN KEIDANREN KAIKAN  

    This study optimizes the dehydration temperature of goethite to control pore morphology. The pore morphology was characterized by using transmission electron microscopy and the nitrogen adsorption method. When the goethite was dehydrated at 200-250 degrees C, slit-like pores with a width lesser than 2 nm were formed along the [010] direction. These slit-like pores changed to spherical micropores (300-500 degrees C), and eventually disappeared (600-800 degrees C). Compared to the synthetic goethite, natural goethite has a lower crystallinity and smaller primary particle size of under 100 nm. The natural goethite before dehydration contained 4 nm pores as cracks that remained even after heating to 800 degrees C. In the case of natural goethite, the optimum dehydration temperature for higher surface area and pore volume was 350 degrees C, which was higher than that of 250 degrees C for the synthetic goethite.

    DOI: 10.2355/isijinternational.ISIJINT-2016-231

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  32. Glycine-nitrate-based solution-combustion synthesis of SrTiO3 Reviewed

    Genki Saito, Yuki Nakasugi, Norihito Sakaguchi, Chunyu Zhu, Tomohiro Akiyama

    JOURNAL OF ALLOYS AND COMPOUNDS   Vol. 652   page: 496 - 502   2015.12

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    In this paper, we describe the glycineenitrate-based solution combustion synthesis of SrTiO3 nanoparticles. The effects of the fuel ratio, 4, and washing treatment by HNO3 on the size, morphology, and crystalline structure of the synthesized particles were investigated. The photocatalytic activity of the final samples was also evaluated by measuring the photodegradation of methylene blue. The samples, which were calcined at 1000 degrees C for 10 h after combustion synthesis, were mainly SrTiO3. When 4 was increased, the number of pores in the sample was increased because of the increase in volume of ejected gas. Additionally, the initial particle size decreased with increasing 4 because glycine functioned not only as a fuel but also as a dispersant and stabilizer. After washing in a HNO3 solution, the porous structure decomposed to particles with high crystalline structure. The photocatalytic activity of SrTiO3 was significantly improved by HNO3 washing owing to the elimination of impurities, the increase in surface area, and the uncovering of the surface that consisted of (100) planes. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2015.08.227

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  33. Urchin-like hollow-structured cobalt oxides with excellent anode performance for lithium-ion batteries Reviewed

    Chunyu Zhu, Genki Saito, Tomohiro Akiyama

    JOURNAL OF ALLOYS AND COMPOUNDS   Vol. 646 ( 15 ) page: 639 - 646   2015.10

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    Urchin-like CoO and Co3O4 hollow structures with potential use as anodes in lithium ion batteries were synthesized via the facile thermal decomposition of precipitated amorphous cobalt carbonate hydroxide under either Ar or air. The morphology and, consequently, electrochemical properties of the samples were highly dependent on the precipitation temperature. The cobalt oxides, as derived from precursors that were obtained at room temperature, exhibited superior activity to those obtained at 50 degrees C and 80 degrees C because of their unique nanosized architecture. Meanwhile, CoO samples demonstrated much better cyclability and rate capability than Co3O4 samples, as they exhibited much higher coulombic efficiency and lower hysteresis for lithium insertion/extration. The curved, short, and closely entangled nanowires of CoO sample, which was derived from room temperature precursor, yielded excellent electrochemical performance. The sample displayed a high reversible capacity of about 850 mAh g(-1) at a current density of 500 mA g(-1), a good stability through 50 cycles with a high coulombic efficiency of about 98%, and a high rate capability of 610 mAh g(-1) even at a rate of 3000 mA g(-1). (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2015.05.206

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  34. Generation of solution plasma over a large electrode surface area Reviewed

    Genki Saito, Yuki Nakasugi, Tomohiro Akiyama

    JOURNAL OF APPLIED PHYSICS   Vol. 118 ( 2 ) page: 023303   2015.7

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    Solution plasma has been used in a variety of fields such as nanomaterials synthesis, the degradation of harmful substances, and solution analysis. However, as existing methods are ineffective in generating plasma over a large surface area, this study investigated the contact glow discharge electrolysis, in which the plasma was generated on the electrode surface. To clarify the condition of plasma generation, the effect of electrolyte concentration and temperature on plasma formation was studied. The electrical energy needed for plasma generation is higher than that needed to sustain a plasma, and when the electrolyte temperature was increased from 32 to 90 degrees C at 0.01 M NaOH solution, the electric power density for vapor formation decreased from 2005 to 774 W/cm(2). From these results, we determined that pre-warming of the electrolyte is quite effective in generating plasma at lower power density. In addition, lower electrolyte concentrations required higher power density for vapor formation owing to lower solution conductivity. On the basis these results, a method for large-area and flat-plate plasma generation is proposed in which an initial small area of plasma generation is extended. When used with a plate electrode, a concentration of current to the edge of the plate meant that plasma could be formed by covering the edge of the electrode plate. (c) 2015 AIP Publishing LLC.

    DOI: 10.1063/1.4926493

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  35. A facile solution combustion synthesis of nanosized amorphous iron oxide incorporated in a carbon matrix for use as a high-performance lithium ion battery anode material Reviewed

    Chunyu Zhu, Genki Saito, Tomohiro Akiyama

    JOURNAL OF ALLOYS AND COMPOUNDS   Vol. 633 ( 5 ) page: 424 - 429   2015.6

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    An amorphous iron oxide-carbon composite has been fabricated through an effective, inexpensive, and scalable method employing solution combustion synthesis. Amorphous iron oxide nanoparticles with diameters of about 5 nm were synthesized and uniformly embedded in a dense carbon matrix. The synthesized composite exhibits enhanced cyclability and rate capability, showing a high reversible capacity of 687 mA h g(1) after 200 discharge/charge cycles at a current rate of 0.5 A g (1), compared to the 400 mA h g (1) observed for Fe2O3 nanoparticles. This enhanced performance was retained despite more demanding conditions, delivering a high capacity of about 525 mA h g (1) and a nearly perfect coulombic efficiency even after 400 cycles at 1 A g (1). The easy production and superior electrochemical properties of this composite suggest that it is a promising material for use as an anode material in high performance lithium ion batteries. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.jallcom.2015.02.043

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  36. Solution plasma synthesis of Si nanoparticles Reviewed

    Genki Saito, Norihito Sakaguchi

    NANOTECHNOLOGY   Vol. 26 ( 23 ) page: 235602-1 - 235602-8   2015.6

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:IOP PUBLISHING LTD  

    Silicon nanoparticles (Si-NPs) were directly synthesized from a Si bar electrode via a solution plasma. In order to produce smaller Si-NPs, the effects of different electrolytes and applied voltages on the product were investigated in the experiments detailed in this paper. The results demonstrated that the use of an acidic solution of 0.1 M HCl or HNO3 produced Si-NPs without SiO2 formation. According to the transmission electron microscopy and electron energy-loss spectroscopy, the obtained Si-NPs contained both amorphous and polycrystalline Si particles, among which the smaller Si-NPs tended to be amorphous. When an alkaline solution of K2CO3 was used instead, amorphous SiO2 particles were synthesized owing to the corrosion of Si in the high-temperature environment. The pH values of KCl and KNO3 increased during electrolysis, and the products were partially oxidized in the alkaline solutions. The particle size increased with an increasing applied voltage because the excitation temperature of the plasma increased.

    DOI: 10.1088/0957-4484/26/23/235602

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  37. Solution plasma synthesis of Au nanoparticles for coating titanium dioxide to enhance its photocatalytic activity Reviewed

    Yuki Nakasugi, Genki Saito, Toru Yamashita, Norihito Sakaguchi, Tomohiro Akiyama

    THIN SOLID FILMS   Vol. 583 ( 29 ) page: 135 - 141   2015.5

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    A convenient method for coating titanium dioxide (TiO2) by Au nanoparticles (AuNPs) is demonstrated in solution plasma to improve the photocatalytic activity of TiO2. AuNPs from a metallic Au electrode were bonded to the surface of a commercial TiO2 powder, which acted as a catalyst support, with the reaction taking place in an electrolyte solution. The effect of diverse plasma conditions on the size and productivity of the AuNPs was investigated initially to provide a reference in the absence of TiO2. At 290V, "partial plasma" was attained, with only a weak light emission surrounding the Au electrode. Conditions then evolved to "full plasma", with a strong orange emission at 330 V. Partial or full status was maintained for 1 h at 300 and 400 V, respectively. At the transition to full, the AuNP particle size increased from 3.72 to 6.09 nm and the productivity increased dramatically from 0.025 to 0.87mgh(-1)mm(-2). Stronger plasma very efficiently synthesized AuNPs, and therefore, it was adopted for further study. AuNP-TiO2 combinations were formed by applying 400 V to a TiO2-dispersed solution. In these experiments, TiO2 coated with AuNPs was synthesized; these combinations of AuNP-TiO2 had 0.44 mol% of Au. The photocatalytic activity of AuNP-TiO2 was investigated by measuring the degradation of Rhodamine B (RhB). Under UV irradiation, the AuNP-TiO2 particles removed up to 95% of the dye in 70min. Commercial TiO2 achieves values closer to 85%. The results thus raise the possibility that solution plasma methods can be generalized as a means for achieving catalysis-enhancing coatings. (C) 2015 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.tsf.2015.03.075

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  38. Glycine/sucrose-based solution combustion synthesis of high-purity LiMn2O4 with improved yield as cathode materials for lithium-ion batteries Reviewed

    Cheng-Gong Han, Chunyu Zhu, Genki Saito, Tomohiro Akiyama

    ADVANCED POWDER TECHNOLOGY   Vol. 26 ( 2 ) page: 665 - 671   2015.3

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    Single-phase, high-purity nanosized LiMn2O4 powders, which are employed as cathode materials for lithium-ion batteries, were produced by solution combustion synthesis using glycine, sucrose, and nitrate, followed by calcination. Phase structure and morphology of the powders were characterized by X-ray diffraction and scanning electron microscopy. The electrochemical performance was measured by galvanostatic charge-discharge cycling in a voltage range of 3.2-4.4 V. The analysis of yield, morphology, and electrochemical performance mainly focused on the influence of different glycine/sucrose ratios. Compared to the sample obtained using 100% glycine, the yields of powders obtained by adding sucrose to the fuel were remarkably improved, from around 50% to over 90%. The highest discharge capacity at 1 C was obtained for the sample with 2% added sucrose, which retained a capacity of 116.6 mAh/g after 80 cycles. (C) 2015 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

    DOI: 10.1016/j.apt.2015.01.019

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  39. Microencapsulation of Metal-based Phase Change Material for High-temperature Thermal Energy Storage Reviewed

    Takahiro Nomura, Chunyu Zhu, Nan Sheng, Genki Saito, Tomohiro Akiyama

    SCIENTIFIC REPORTS   Vol. 5   page: 9117   2015.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:NATURE PUBLISHING GROUP  

    Latent heat storage using alloys as phase change materials (PCMs) is an attractive option for high-temperature thermal energy storage. Encapsulation of these PCMs is essential for their successful use. However, so far, technology for producing microencapsulated PCMs (MEPCMs) that can be used above 500 degrees C has not been established. Therefore, in this study, we developed Al-Si alloy microsphere MEPCMs covered by alpha-Al2O3 shells. The MEPCM was prepared in two steps: (1) the formation of an AlOOH shell on the PCM particles using a boehmite treatment, and (2) heat-oxidation treatment in an O-2 atmosphere to form a stable alpha-Al2O3 shell. The MEPCM presented a melting point of 573 degrees C and latent heat of 247 J g(-1). The cycling performance showed good durability. These results indicated the possibility of using MEPCM at high temperatures. The MEPCM developed in this study has great promise in future energy and chemical processes, such as exergy recuperation and process intensification.

    DOI: 10.1038/srep09117

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  40. Improved electrochemical properties of LiMn2O4 with the Bi and La co-doping for lithium-ion batteries Reviewed

    Cheng-Gong Han, Chunyu Zhu, Genki Saito, Tomohiro Akiyama

    RSC ADVANCES   Vol. 5 ( 89 ) page: 73315 - 73322   2015

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    A series of LiBixLaxMn2-2xO4 (x = 0, 0.002, 0.005, 0.010, 0.020) samples were synthesized by solution combustion synthesis in combination with calcination. The phase structure and morphology of the products were characterized by X-ray diffraction, scanning electron microscopy, and transition electron microscopy. The results demonstrated that a single-phase LiMn2O4 spinel structure was obtained for the LiBixLaxMn2-2xO4 (x = 0, 0.002, 0.005) samples, whereas impurities were observed for the LiBixLaxMn2-2xO4 (x = 0.010, 0.020) samples as a result of the doping limit. The electrochemical properties were investigated by galvanostatic charge-discharge cycling and cycling voltammetry in a voltage range of 3.2-4.4 V. The substitution of Mn3+ by equimolar Bi3+ and La3+ could significantly improve the structural stability and suppress the Jahn-Teller distortion, thereby resulting in improved electrochemical properties for the Bi and La co-doped samples in contrast with the pristine LiMn2O4 sample. In particular, the LiBi0.005La0.005Mn1.99O4 sample delivered a high initial discharge capacity of 130.2 mA h g(-1) at 1C, and following 80 cycles, the capacity retention was as high as 95.0%. Moreover, it also presented the best rate capability among all the samples, in which a high discharge capacity of 98.3 mA h g(-1) was still maintained at a high rate of 7C compared with that of 75.8 mA h g(-1) for the pristine LiMn2O4 sample.

    DOI: 10.1039/c5ra13005k

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  41. Nanomaterial Synthesis Using Plasma Generation in Liquid Invited Reviewed

    Genki Saito, Tomohiro Akiyama

    JOURNAL OF NANOMATERIALS   Vol. 2015   page: 123696   2015

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    Authorship:Lead author, Corresponding author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:HINDAWI LTD  

    Over the past few decades, the research field of nanomaterials (NMs) has developed rapidly because of the unique electrical, optical, magnetic, and catalytic properties of these materials. Among the various methods available today for NM synthesis, techniques for plasma generation in liquid are relatively new. Various types of plasma such as arc discharge and glow discharge can be applied to produce metal, alloy, oxide, inorganic, carbonaceous, and composite NMs. Many experimental setups have been reported, in which various parameters such as the liquid, electrode material, electrode configuration, and electric power source are varied. By examining the various electrode configurations and power sources available in the literature, this review classifies all available plasma in liquid setups into four main groups: (i) gas discharge between an electrode and the electrolyte surface, (ii) direct discharge between two electrodes, (iii) contact discharge between an electrode and the surface of surrounding electrolyte, and (iv) radio frequency and microwave plasma in liquid. After discussion of the techniques, NMs of metal, alloy, oxide, silicon, carbon, and composite produced by techniques for plasma generation in liquid are presented, where the source materials, reaction media, and electrode configurations are discussed in detail.

    DOI: 10.1155/2015/123696

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  42. Excitation temperature of a solution plasma during nanoparticle synthesis Reviewed

    Genki Saito, Yuki Nakasugi, Tomohiro Akiyama

    JOURNAL OF APPLIED PHYSICS   Vol. 116 ( 8 ) page: 83301   2014.8

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    Excitation temperature of a solution plasma was investigated by spectroscopic measurements to control the nanoparticle synthesis. In the experiments, the effects of edge shielding, applied voltage, and electrode material on the plasma were investigated. When the edge of the Ni electrode wire was shielded by a quartz glass tube, the plasma was uniformly generated together with metallic Ni nanoparticles. The emission spectrum of this electrode contained OH, H-alpha, H-beta, Na, O, and Ni lines. Without an edge-shielded electrode, the continuous infrared radiation emitted at the edge created a high temperature on the electrode surface, producing oxidized coarse particles as a result. The excitation temperature was estimated from the Boltzmann plot. When the voltages were varied at the edge-shielded electrode with low average surface temperature by using different electrolyte concentrations, the excitation temperature of current-concentration spots increased with an increase in the voltage. The size of the Ni nanoparticles decreased at high excitation temperatures. Although the formation of nanoparticles via melting and solidification of the electrode surface has been considered in the past, vaporization of the electrode surface could occur at a high excitation temperature to produce small particles. Moreover, we studied the effects of electrodes of Ti, Fe, Ni, Cu, Zn, Zr, Nb, Mo, Pd, Ag, W, Pt, Au, and various alloys of stainless steel and Cu-Ni alloys. With the exception of Ti, the excitation temperatures ranged from 3500 to 5500 K and the particle size depended on both the excitation temperature and electrode-material properties. (C) 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4894156

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  43. Optimization of electrolyte concentration and voltage for effective formation of Sn/SnO2 nanoparticles by electrolysis in liquid Reviewed

    Genki Saito, Wan Omar Sidiq Bin Wan Mohd Azman, Yuki Nakasugi, Tomohiro Akiyama

    ADVANCED POWDER TECHNOLOGY   Vol. 25 ( 3 ) page: 1038 - 1042   2014.5

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    This work investigates the optimum experimental conditions required for the synthesis of Sn nanopartides (Sn-NPs) via surfactant-free direct-current electrolysis using KCl as the electrolyte. Metallic Sn wire was used as a cathode, which was melted by the local concentration of current upon the application of a direct-current voltage. The effect of electrolyte concentration was analyzed by varying the concentration from 0.01 to 1.0 M, under constant electric power of 40W. Results indicated that the applied voltage required for plasma generation increased with a decrease in the electrolyte concentration and the particle size decreased at high applied voltage with low electrolyte concentration; particles with a mean diameter of 258.5 nm formed at 0.05 M. However, coarse Sn6O4(OH)(4) crystals were precipitated at a concentration of 0.01 M. Therefore, the optimum concentration required for the formation of smaller particles was determined to be 0.05 M. Subsequently, the effect of voltage was analyzed by varying the applied voltage from 70 to 190 V. As a result, the effective production energy of 45 W h/g was obtained at voltages ranging from 110 to 130 V. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

    DOI: 10.1016/j.apt.2014.02.003

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  44. Solution plasma synthesis of bimetallic nanoparticles Reviewed

    Genki Saito, Yuki Nakasugi, Toru Yamashita, Tomohiro Akiyama

    NANOTECHNOLOGY   Vol. 25 ( 13 ) page: 135603   2014.4

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    This paper describes the facile solution plasma synthesis of bimetallic nanoparticles, including solid solution alloys (Ni-Cu and Ni-Cr system), eutectic alloys of Sn-Pb, and intermetallic alloys (SnSb and Ni3Sn), by using metallic alloy wire as the cathode and Pt wire as the anode. In the typical process, the cathode was melted by the local-concentration of current, upon applying a DC voltage between the two electrodes immersed in the electrolyte. The solid solution alloys of Ni-Cu and Ni-Cr prepared in this study have a uniform distribution of composition. On the other hand, the uniformity in the composition of the eutectic Sn-Pb alloy depends on the microstructure of the electrode. The use of quenched electrode with small crystal grains favors the formation of Sn-Pb alloy nanoparticles, in which the Sn-rich and Pb-rich phases coexist in each particle. The formation of intermetallic SnSb and Ni3Sn alloy nanoparticles is accompanied by the formation of colloidal oxide. These results demonstrate that the solution plasma technique is applicable not only for the synthesis of pure metals but can also be used for the synthesis of various alloy nanoparticles.

    DOI: 10.1088/0957-4484/25/13/135603

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  45. Porous Ore Structure and Deposited Carbon Type during Integrated Pyrolysis-Tar Decomposition Reviewed

    Rochim B. Cahyono, Genki Saito, Naoto Yasuda, Takahiro Nomura, Tomohiro Akiyama

    ENERGY & FUELS   Vol. 28 ( 3 ) page: 2129 - 2134   2014.3

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    Carbon deposited by tar decomposition within pores of iron ore exhibited a high reactivity during the reduction reaction. The structure of porous low-grade ore was investigated in detail using transmission electron microscopy (TEM); a layered structure with 3 nm diameter pores was observed after dehydration, because of the removal of the hydroxide (OH) group from FeOOH. This pore size was deemed to be appropriate for tar decomposition and resultant carbon deposition. However, it was found that not all pores were filled with carbon. The TEM image showed that some of the deposited carbon partially blocks the pores, which negatively affects the carbon deposition process. In addition to the ore structure, the type of carbon deposited was also successfully evaluated using Raman spectroscopy and found to consist of two main peaks, G and D. The position of the G peak was found to shift slightly, indicating that the sp(3) content was reduced at elevated temperatures because of a greater degree of graphitization. The carbon deposited by integrated pyrolysis-tar decomposition over low-grade ore was categorized as amorphous carbon (a-C), with a sp(3) content of 19-21%. These results can also be explained by high reactivity of the deposited carbon, which was improved by not only nanoscale contact between iron and carbon but also specific molecule bonding and arrangement of amorphous carbon.

    DOI: 10.1021/ef500201m

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  46. Synthesis of nonstoichiometric titanium oxide nanoparticles using discharge in HCl solution Reviewed

    Yuki Nakasugi, Genki Saito, Toru Yamashita, Tomohiro Akiyama

    JOURNAL OF APPLIED PHYSICS   Vol. 115 ( 12 ) page: 123303   2014.3

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    This study demonstrates the synthesis of nonstoichiometric titanium oxide (TiO2-delta) nanoparticles using plasma discharge. We have primarily investigated the effect of electrolyte concentration and edge shielding of electrode on the morphology, and oxygen defects of the final product. As a precursor for nanoparticle synthesis, titanium wire was utilized as a cathode, which was immersed in an HCl electrolyte in the concentration range of 0.1-5.0 M. The electrode edge was shielded to maintain uniform distribution of electric current. For comparison, we also used an electrode without edge shielding. Systematic studies indicate that the as-prepared products were spherical titanium oxide nanoparticles, the size of which decreased with decrease in electrolyte concentration. The edge shielding of the electrode was found to affect the size distribution and oxidation degree of the products. In case of the edge-shielded electrode, the oxidation of the product was suppressed, resulting in a product composition of TiO1.72. In contrast, in case of the electrode without edge shielding, the oxidation of the products was favored, resulting in formation of TiO1.90. This could be attributed to the concentration of electric current at the electrode edge, in which the heating-up of the electrode edge enhanced the oxidation of the product. These results confirm the possibility of synthesizing nonstoichiometric oxide nanoparticles with controllable oxygen defects by using plasma discharge in HCl solution. (C) 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4869126

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  47. Surfactant-assisted synthesis of Sn nanoparticles via solution plasma technique Reviewed

    Genki Saito, Chunyu Zhu, Tomohiro Akiyama

    ADVANCED POWDER TECHNOLOGY   Vol. 25 ( 2 ) page: 728 - 732   2014.3

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE BV  

    We have adopted a solution plasma synthesis for preparing Sn nanoparticles (Sn-NPs) directly from metallic Sn electrode. The Sn-NPs were synthesized in the presence of the surfactant, cetyltrimethylammonium bromide (CTAB), and the effect of the concentration of CTAB on the Sn-NPs was investigated. Without CTAB addition, SnO plates were precipitated. Sn-NPs with less than 200 nm were synthesized at a high concentration of 200 x 10(-6) g ml(-1) of CTAB. Electrochemical properties of SnO plates and Sn-NPs were analyzed for use as an anode material in Li-ion batteries. A composite of Sn-NPs and graphite enhanced the cyclic stability owing to the buffer space provided by the graphite for volume expansion. In the case of the 30 wt% loaded Sn-NPs, the capacity was measured to be 414 mA h g(-1) after 20 cycles. (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

    DOI: 10.1016/j.apt.2013.11.001

    Web of Science

  48. High-speed camera observation of solution plasma during nanoparticles formation Reviewed

    Genki Saito, Yuki Nakasugi, Tomohiro Akiyama

    APPLIED PHYSICS LETTERS   Vol. 104 ( 8 ) page: 83104   2014.2

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    The direct-current discharge plasma during nanoparticles formation was observed using a high-speed camera. Metallic plates of Au, Ni, Ti, and Zn were used as a cathode, and a Pt wire was used as an anode. Both electrodes were immersed in a 0.1M NaOH solution. The solution plasma with light emission was generated via the vapor layer surrounding the cathode by applying 190 V. The current concentration occurred at a certain point of the electrode surface, in which the electrode surface was partially melted to produce nanoparticles. According to the high-speed observation, many light-emitting points appeared on the metallic plate and immediately disappeared when a certain point was strongly heated to produce nanoparticles. Additionally, light emission points moved in a chain reaction; after the first emission point was generated, the next emission point tended to be generated in the space surrounding the first emission point. During electrolysis, holes were generated on the cathode. The current concentration strongly heated certain spots on the electrode, and the electrode momentarily melted or vaporized, resulting in the formation of nanoparticles. (C) 2014 AIP Publishing LLC.

    DOI: 10.1063/1.4865498

    Web of Science

  49. Solution combustion synthesis of LiMn2O4 fine powders for lithium ion batteries Reviewed

    Chunyu Zhu, Akira Nobuta, Genki Saito, Isao Nakatsugawa, Tomohiro Akiyama

    ADVANCED POWDER TECHNOLOGY   Vol. 25 ( 1 ) page: 342 - 347   2014.1

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE BV  

    In this work, fine powders of spinel-type LiMn2O4 as cathode materials for lithium ion batteries (LIBs) were produced by a facile solution combustion synthesis using glycine as fuel and metal nitrates as oxidizers. Single phase of LiMn2O4 products were successfully prepared by SCS with a subsequent calcination treatment at 600-1000 degrees C. The structure and morphology of the powders were studied in detail by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. The electrochemical properties were characterized by galvanostatic charge-discharge cycling and cyclic voltammetry. The crystallinity, morphology, and size of the products were greatly influenced by the calcination temperature. The sample calcined at 900 C had good crystallinity and particle sizes between 500 and 1000 nm. It showed the best performance with an initial discharge capacity of 115.6 mAh g(-1) and a capacity retention of 93% after 50 cycles at a 1 C rate. In comparison, the LiMn2O4 sample prepared by the solid-state reaction showed a lower capacity of around 80 mAh g(-1). (C) 2013 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.

    DOI: 10.1016/j.apt.2013.05.015

    Web of Science

  50. Solution plasma synthesis of ZnO flowers and their photoluminescence properties Reviewed

    Genki Saito, Yuki Nakasugi, Toru Yamashita, Tomohiro Akiyama

    APPLIED SURFACE SCIENCE   Vol. 290 ( 30 ) page: 419 - 424   2014.1

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    ZnO nanoflowers, amorphous ZnO nanospheres and metallic Zn particles have been controllably synthesized using solution plasma technique at different reaction temperatures and agitation. X-ray diffractometry (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) revealed that ZnO nanoflowers were synthesized at a high electrolyte temperature in a static system (no agitation). On the other hand, the use of agitation led to both amorphous ZnO nanospheres and spherical metallic zinc particles. The excitation temperature of plasma was 4000 K from the light emission using spectrometer. From these result, melting and vaporization of the Zn electrode produced particles. ZnO nanoflowers grew on the surface of spherical particles by precipitation from Zn(OH)(4)(2-) ions. Photoluminescence (PL) measurement indicated that as-synthesized ZnO flowers and amorphous ZnO nanospheres showed strong green emissions, which was attributable to their surface defect structure. Furthermore, the annealing at 700 degrees C led to a reduction in green emissions, attributable to a decrease in the number of surface defects. Photocatalytic activity of ZnO nanoflowers was increased by the annealing. (C) 2013 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.apsusc.2013.11.097

    Web of Science

  51. A New Route to Synthesize β-SiAlON:Eu2+ Phosphors for White Light-Emitting Diodes Reviewed

    Jing Niu, Genki Saito, Tomohiro Akiyama

    Applied Physics Express   Vol. 6 ( 4 ) page: 42105   2013.4

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    A simple, highly efficient method of synthesizing β-SiAlON:Eu2+ phosphors for white light-emitting diodes was reported. The new route was carried out via a combustion synthesis method using Si, SiO2, and Al raw materials, and NaCl as a diluent under nitrogen pressure. The phase purity, photoluminescence properties, and thermal quenching of the phosphors were investigated. The results revealed that the synthesized β-SiAlON:Eu2+ powders, which comprised rodlike crystals, exhibited high thermal stability: The emission intensity at 160 ±C was 84% of that measured at room temperature, which indicates that the synthesized β-SiAlON:Eu2+ phosphors have high potential for application to white LEDs. © 2013 The Japan Society of Applied Physics.

    DOI: 10.7567/APEX.6.042105

    Scopus

  52. A new CaCO3-template method to synthesize nanoporous manganese oxide hollow structures and their transformation to high-performance LiMn2O4 cathodes for lithium-ion batteries Reviewed

    Chunyu Zhu, Genki Saito, Tomohiro Akiyama

    JOURNAL OF MATERIALS CHEMISTRY A   Vol. 1 ( 24 ) page: 7077 - 7082   2013

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    Language:English   Publishing type:Research paper (scientific journal)   Publisher:ROYAL SOC CHEMISTRY  

    This paper presents a new CaCO3-template synthesis of highly nanoporous manganese oxide hollow structures and their transformation to high-performance LiMn2O4 cathodes for lithium-ion batteries via the facile coprecipitation of Mn-Ca-carbonates and temperature-controlled decomposition of MnCO3 and CaCO3, followed by the selective removal of the carbonates by washing with HCl. The as-prepared Mn2O3 nanostructures showed very high specific surface area with their subunit particle size of <30 nm, as compared with conventional processes with subunits of >100 nm. The transformation to uniformly porous LiMn2O4 hollow structures was successfully achieved by the facile impregnation of LiOH into the porous Mn2O3 hollow precursors, followed by a conventional solid-state reaction. The LiMn2O4 hollow structures deliver a discharge capacity of about 120 mA h g(-1) at a 1 C rate and 115 mA h g(-1) at a 10 C rate with excellent cycling stability. The capacity retention approached 94% after up to 800 cycles of charging-discharging at a 10 C rate.

    DOI: 10.1039/c3ta11066d

    Web of Science

  53. Surface morphology of a glow discharge electrode in a solution Reviewed

    Genki Saito, Sou Hosokai, Masakatsu Tsubota, Tomohiro Akiyama

    JOURNAL OF APPLIED PHYSICS   Vol. 112 ( 1 ) page: 13306   2012.7

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    This paper describes the surface morphology of a glow discharge electrode in a solution. In the experiments detailed in the paper, the effects of electrolysis time, solution temperature, voltage, electrolyte concentration, and surface area on the size of nanoparticles formed and their amount of nanoparticles produced were examined to study the surface morphologies of the electrodes. The results demonstrated that the amount of nanoparticles produced increased proportionally with the electrolysis time and current. When the voltages were below 140 V, surfaces with nanoparticles attached, called "Particles" type surfaces, were formed on the electrode. These surfaces changed and displayed ripples, turning into "Ripple" type surfaces, and the nanoparticle sizes increased with an increase in the amount of nanoparticles produced. In contrast, at voltages over 160 V, the surfaces of the electrodes were either "Random" or "Hole" type and the particle sizes were constant at different amount of nanoparticles produced. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4732076]

    DOI: 10.1063/1.4732076

    Web of Science

  54. Influence of Solution Temperature and Surfactants on Morphologies of Tin Oxide Produced Using a Solution Plasma Technique Reviewed

    Genki Saito, Sou Hosokai, Masakatsu Tsubota, Tomohiro Akiyama

    CRYSTAL GROWTH & DESIGN   Vol. 12 ( 5 ) page: 2455 - 2459   2012.5

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    Single-crystalline tin oxide (SnO) plates were synthesized by a solution plasma technique using an Sn wire. In the experiments, we applied a voltage of 400 V in a 0.001 M K2CO3 solution. The effects on the products of the solution temperature, the use of surfactants, and the cooling rate were investigated. A solution temperature above 95.0 degrees C was effective for producing single-crystal SnO plates. The addition of poly(vinyl alcohol) (PVA) significantly stabilized the Sn6O4(OH)(4) octahedrons. In the case of cetyltrimethylarnmonium bromide (CTAB) addition, SnO and Sn crystals with plate crystal, particle, and rod morphologies were formed. Quenching the solution affected the product size. Faster cooling rates reduced the size of the SnO plates. SnO plates with (001) plane faces precipitated from Sn(OH)(3)(-) ions to form plate-like crystals as a result of the difference in the growth rates at each plane.

    DOI: 10.1021/cg300083k

    Web of Science

  55. Ripple formation on a nickel electrode during a glow discharge in a solution Reviewed

    Genki Saito, Sou Hosokai, Masakatsu Tsubota, Tomohiro Akiyama

    APPLIED PHYSICS LETTERS   Vol. 100 ( 18 ) page: 181601   2012.4

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    We investigated ripple formation on a nickel electrode during a glow discharge in a solution. A nickel wire was partially melted to produce nanoparticles during glow discharge electrolysis. When the electrolysis time was over 30 min, a ripple pattern was formed on the electrode surface, and particle size increased. In this study, we investigated the relationship between the ripple formation and crystal orientation of the electrode. As a result, the ripple patterns were formed on all planes, except (111)- and (100)-oriented planes; their direction was [001]. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709491]

    DOI: 10.1063/1.4709491

    Web of Science

  56. Nickel Nanoparticles Formation from Solution Plasma Using Edge-Shielded Electrode Reviewed

    G. Saito, S. Hosokai, M. Tsubota, T. Akiyama

    PLASMA CHEMISTRY AND PLASMA PROCESSING   Vol. 31 ( 5 ) page: 719 - 728   2011.10

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    Because of the easy massproduction, synthesis of metallic nanoparticles from a solution plasma is an attractive method. However, a solution plasma produces a highly inhomogeneous electric field via transition to full-plasma, and the products are partially oxidized and agglomerated, with a wide size-distribution. Here, we show a simple method of suppressing oxidation of products. An electrode tip was shield by a glass tube and a voltage of up to 180 V was applied with the electrolyte of 0.1 M NaOH solution. Significantly, the edge-shield was quite effective for maintaining partially glow discharge. The results were (1) surface temperature of the electrode less than 100 degrees C, (2) main phase of metallic nickel evaluated by XRD, and (3) nanoparticles of an average size of 220 nm. These results showed the potential for an application to the production of nanoparticles.

    DOI: 10.1007/s11090-011-9313-4

    Web of Science

  57. Synthesis of ZnO nanoflowers by solution plasma Reviewed

    Genki Saito, Sou Hosokai, Tomohiro Akiyama

    MATERIALS CHEMISTRY AND PHYSICS   Vol. 130 ( 1-2 ) page: 79 - 83   2011.10

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:ELSEVIER SCIENCE SA  

    We synthesized ZnO nanoflowers using a solution plasma. We examined the effects of the applied voltage and the concentration of the electrolyte on the morphology of the products. In the experiments, the zinc wire (cathode) was immersed in an electrolysis solution of K2CO3 (concentration: 0.01-5.00 M) and was electrically melted by a glow discharge at different voltages ranging from 42 to 200 V. The results revealed that the products were nanoflowers having many nanorods (size: <100 nm). The ZnO nanoflowers had a wurtzite structure with the [0 0 0 1] orientation in the growth direction. The product morphology changed with a change in the concentration of the electrolyte, C, and the applied voltage, V; that is, nanoflowers were generated under the limited conditions of (C, V) = (1.0 M, 66 V), (0.5 M, 80 V), and (0.1 M, 105 V). (C) 2011 Elsevier B.V. All rights reserved.

    DOI: 10.1016/j.matchemphys.2011.05.084

    Web of Science

  58. Synthesis of copper/copper oxide nanoparticles by solution plasma Reviewed

    Genki Saito, Sou Hosokai, Masakatsu Tsubota, Tomohiro Akiyama

    JOURNAL OF APPLIED PHYSICS   Vol. 110 ( 2 ) page: 23302   2011.7

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    Authorship:Lead author   Language:English   Publishing type:Research paper (scientific journal)   Publisher:AMER INST PHYSICS  

    This paper describes the synthesis of copper/copper oxide nanoparticles via a solution plasma, in which the effect of the electrolyte and electrolysis time on the morphology of the products was mainly examined. In the experiments, a copper wire as a cathode was immersed in an electrolysis solution of a K(2)CO(3) with the concentration from 0.001 to 0.50 M or a citrate buffer (pH = 4.8), and was melted by the local-concentration of current. The results demonstrated that by using the K(2)CO(3) solution, we obtained CuO nanoflowers with many sharp nanorods, the size of which decreased with decreasing the concentration of the solution. Spherical particles of copper with/without pores formed when the citrate buffer was used. The pores in the copper nanoparticles appeared when the applied voltage changed from 105 V to 130 V, due to the dissolution of Cu(2)O. (C) 2011 American Institute of Physics. [doi:10.1063/1.3610496]

    DOI: 10.1063/1.3610496

    Web of Science

  59. Size-Controlled Ni Nanoparticles Formation by Solution Glow Discharge Reviewed

    Genki Saito, Sou Hosokai, Tomohiro Akiyama, Souki Yoshida, Shigeo Yatsu, Seiichi Watanabe

    JOURNAL OF THE PHYSICAL SOCIETY OF JAPAN   Vol. 79 ( 8 ) page: 83501   2010.8

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    We report the size control of Ni nanoparticles generated via solution glow discharge and focus on the effect of electrolyte concentration on Ni nanoparticles. In our experiments, voltage was applied to generate a plasma in NaOH electrolytes with concentrations ranging from 1.0 to 0.001 kmol m(-3). The applied voltage strongly depended on the electrolyte concentration, and interestingly, product size decreased with electrolyte concentration; for example, (mean diameter, applied voltage, electrolyte concentration) = (148 nm, 90 V, 0.5 kmol m(-3)), and (70 nm, 590 V, 0.001 kmol m(-3)). These results suggested the possibility of using plasma electrolysis for synthesizing size-controlled nanoparticles by changing only electrolyte concentration.

    DOI: 10.1143/JPSJ.79.083501

    Web of Science

▼display all

MISC 1

  1. 炭素鋼中における複合析出物の析出挙動

    齊藤 元貴

    まてりあ   Vol. 60 ( 8 ) page: 486 - 491   2021.8

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publishing type:Article, review, commentary, editorial, etc. (scientific journal)  

    DOI: 10.2320/materia.60.486

Presentations 49

  1. 肌焼鋼の熱間鍛造後の焼ならしにおけるAlNの析出挙動

    齊藤元貴, 坂口紀史, 松浦清隆, 佐野太一, 山岡拓也

    日本鉄鋼協会第183回春季講演大会  2022.3.15 

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    Event date: 2022.3

    Language:Japanese   Presentation type:Oral presentation (general)  

  2. In-situ SEM-EBSD法による低合金鋼の異常粒成長における粒界方位差の解析

    齊藤 元貴、張 天龍、坂口 紀史、大野 宗一、松浦 清隆、竹内 正芳、佐野 太一、山岡 拓也

    日本金属学会2022年春期講演大会  2022.3 

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    Event date: 2022.3

    Language:Japanese   Presentation type:Poster presentation  

  3. 省エネルギー空気分離プロセスへ向けた酸素貯蔵材料Ca2-xSrxAlMnO5+δのSrドープ量最適化

    棚橋 慧太 , 大村 湧生 , 納谷 英和 , 齊藤 元貴 , Ade Kurniawan , 國貞 雄治 , 坂口 紀史 , 能村 貴宏

    化学工学会第52回秋季大会  2021.9 

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    Event date: 2021.9

    Language:Japanese   Presentation type:Oral presentation (general)  

  4. AlおよびNbを添加した肌焼鋼中の微細粒子の析出挙動

    齊藤 元貴, 坂口 紀史, 松浦 清隆, 佐野 太一, 蓑口 光樹, 山岡 拓也

    日本顕微鏡学会 第77回学術講演会  2021.6.16 

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    Event date: 2021.6

    Language:Japanese   Presentation type:Oral presentation (general)  

  5. 酸素吸蔵材料Ca2AlMnO5+δの局所電子状態の分析

    齊藤元貴, 速水一輝, 國貞雄治, 能村貴宏, 坂口紀史

    日本顕微鏡学会第73回学術講演会  2017.5.30 

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  6. 肌焼鋼中のAlN-Nb(C, N)複合析出物の析出挙動

    齊藤 元貴, 坂口 紀史, 大野 宗一, 松浦 清隆, 竹内 正芳, 佐野 太一, 蓑口 光樹, 山岡 拓也

    日本顕微鏡学会第76回学術講演会  2020.5 

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  7. 肌焼鋼の熱間鍛造後の冷却速度および焼ならし温度が析出物および浸炭時のγ粒組織に与える影響

    齊藤元貴, 坂口紀史, 松浦清隆, 蓑口光樹, 山岡拓也

    日本鉄鋼協会第181回春季講演大会  2021.3.17 

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  8. 肌焼鋼の浸炭時におけるγ粒組織に及ぼす鍛造温度および添加元素濃度の影響

    齊藤元貴, 坂口紀史, 大野宗一, 松浦清隆, 蓑口光樹, 山岡拓也

    日本鉄鋼協会第178回秋季講演大会  2019.9.11 

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  9. 繰り返し変態によるばね鋼の結晶粒微細化における微細析出物の効果

    齊藤元貴, 坂口紀史, 大野宗一, 松浦清隆, 蓑口光樹, 山岡拓也

    日本鉄鋼協会第177回春季講演大会  2019.3.21 

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  10. 炭素および酸素をドープしたAlNの燃焼合成

    齊藤 元貴, 國貞 雄治, 渡邉 拓海, 能村 貴宏, 衣 雪梅, 坂口 紀史, 秋山 友宏

    日本金属学会2018年秋期講演大会  2018.9.19 

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  11. 加熱SEM-EBSD法によるばね鋼の逆変態のその場観察

    齊藤 元貴, 中山知哉, 坂口紀史, 大野宗一, 松浦清隆, 竹内正芳, 佐野太一, 蓑口光樹, 山岡拓也

    日本顕微鏡学会第75回学術講演会  2019.6.18 

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  12. マルテンサイトからの逆変態 γ 粒形成挙動に及ぼす加熱速度の影響

    齊藤 元貴, 中山知哉, 坂口紀史, 大野宗一, 松浦清隆, 竹内正芳, 佐野太一, 蓑口光樹, 山岡拓也

    日本金属学会・日本鉄鋼協会両支部合同サマーセッション  2019.7.5 

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  13. スルーフォーカスHAADF-STEM法によるドーパント分布解析における収束角の影響

    齊藤 元貴, 八巻 風太, 國貞 雄治, 坂口 紀史

    日本金属学会2017年秋期講演大会  2017.9.8 

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  14. スルーフォーカスHAADF-STEM法によるCa-α-SiAlON中Eu原子の3次元分布解析

    齊藤元貴, 八巻風太, 國貞雄治, 坂口紀史

    日本顕微鏡学会第73回学術講演会  2017.5.31 

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  15. ばね鋼の繰り返し逆変態による結晶粒微細化における微細析出物の影響

    齊藤 元貴, 田中 由紀子, 徳永 透子, 大野 宗一, 坂口 紀史, 松浦 清隆, 佐野 太一, 竹内 正芳, 簔口 光樹, 山岡 卓也

    平成30年度公益社団法人日本顕微鏡学会 北海道支部学術講演会  2018.11.24 

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  16. STEM-EELSによる酸素吸蔵材料Ca2AlMnO5+δの局所電子状態の解析

    齊藤元貴, 速水一輝, 國貞雄治, 坂口紀史

    日本金属学会2017年春期講演大会  2017.3.16 

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  17. Nb添加肌焼鋼の熱間鍛造後の冷却速度が浸炭時の微細析出物およびγ粒組織に与える影響

    齊藤元貴, 坂口紀史, 大野宗一, 松浦清隆, 蓑口光樹, 山岡拓也

    日本鉄鋼協会第179回春季講演大会  2020.3.18 

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  18. In situ observations of reverse transformation of austenite from martensite in low alloy steel International conference

    G. Saito, T. Tokunaga, M. Ohno, K. Matsuura, M. Takeuchi, T. Sano, K. Minoguchi, T. Yamaoka

    6th AGH-HU Joint Symposium  2018.5.16 

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  19. HAADF-STEM法による蛍光体材料中ドーパントの空間分布解析

    齊藤元貴, 國貞雄治, 坂口紀史

    日本顕微鏡学会第74回学術講演会  2018.5.29 

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  20. HAADF-STEM法による蛍光体中ドーパント原子の空間分布解析

    齊藤 元貴, 坂口 紀史

    日本金属学会2020年秋期講演大会  2020.9.18 

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  21. HAADF-STEM法によるドーパント分布解析における電子チャネリングの影響

    齊藤元貴, 國貞雄治, 坂口紀史

    日本金属学会2018年春期講演大会  2018.3.21 

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  22. HAADF-STEM 法によるドーパント分布解析におけるフォーカス依存性

    齊藤 元貴, 國貞 雄治, 坂口 紀史

    平成29年度公益社団法人日本顕微鏡学会 北海道支部学術講演会  2017.12.16 

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  23. Dopant distribution analysis of Eu-doped Ca-α-SiAlONvia HAADF-STEM imaging International conference

    G. Saito, F. Yamaki, Y. Kunisada, N. Sakaguchi, T. Akiyama

    9th International Symposium on Nitrides and Related Materials (ISNT2017) & 5th International Symposium on SiAlONs and Non-oxides (ISSNOX5)  2017.8.29 

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  24. 異なる温度で熱処理したゲーサイトの細孔形態および双晶構造

    齊藤 元貴, 國貞 雄治, 坂口 紀史, 秋山 友宏

    平成27年度日本金属学会北海道支部冬季講演大会  2015.12 

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  25. 液中プラズマで生成したシリコンナノ粒子の分析

    齊藤 元貴, 坂口 紀史

    日本顕微鏡学会第71回学術講演会  2015.5.14 

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    Language:Japanese   Presentation type:Poster presentation  

  26. 多孔質カーボン‐Snナノ粒子複合体の作製と二次電池特性

    齊藤 元貴, 朱 春宇, 坂口 紀史, 秋山 友宏

    日本金属学会2016年春期大会  2016.3.24 

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    Language:Japanese   Presentation type:Oral presentation (general)  

  27. 光触媒材料としてのチタン酸ストロンチウムの液体燃焼合成

    中杉 祐己, 齊藤 元貴, 朱 春宇, 秋山 友宏

    日本金属学会 2014年秋期講演大会  2014.9.24 

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    Language:English   Presentation type:Poster presentation  

    Venue:名古屋大学東山キャンパス  

  28. マンガン酸化物のEELS測定条件の検討

    齊藤元貴, 國貞雄治, 坂口紀史

    日本金属学会・日本鉄鋼協会両支部合同サマーセッション  2015.7 

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    Language:Japanese   Presentation type:Poster presentation  

  29. ブラウンミラーライト型Ca2MnAlO5+δの局所電子状態の解析

    齊藤 元貴, 速水 一輝, 國貞 雄治, 能村 貴宏, 坂口 紀史, 秋山 友宏

    日本顕微鏡学会第72回学術講演会  2016.6.15 

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    Language:Japanese   Presentation type:Poster presentation  

  30. ナノ粒子生成中の液中プラズマの高速度カメラ観察

    齊藤元貴, 中杉祐己, 秋山友宏

    第75回応用物理学会秋季学術講演会  2014.9.20 

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    Language:English   Presentation type:Oral presentation (general)  

    Venue:北海道大学 札幌キャンパス  

  31. スルーフォーカスHAADF-STEM法によるSiAlON中ドーパントの3次元分布解析

    齊藤 元貴, 八巻 風太, 國貞 雄治, 坂口 紀史

    日本金属学会・日本鉄鋼協会両支部合同サマーセッション  2016.7.1 

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    Language:Japanese   Presentation type:Poster presentation  

  32. スルーフォーカスHAADF-STEM法によるCa-SiAlON中Eu原子の空間分布解析

    齊藤 元貴, 八巻 風太, 國貞 雄治, 坂口 紀史

    日本金属学会2016年秋期講演大会  2016.9.22 

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  33. スルーフォーカスHAADF-STEM 法による蛍光体中ドーパントの3 次元分布評価

    齊藤元貴, 八巻風太, 國貞雄治, 坂口紀史

    平成28年度公益社団法人日本顕微鏡学会 北海道支部学術講演会  2016.12.10 

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    Language:Japanese   Presentation type:Oral presentation (general)  

  34. スズナノ粒子の液中プラズマ合成と電池特性

    齊藤 元貴, 朱 春宇, 坂口 紀史, 秋山 友宏

    日本金属学会 2015年春季講演大会  2015.3.18 

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  35. シリコンナノ粒子の液中プラズマ合成

    齊藤 元貴, 坂口 紀史, 秋山 友宏, 高橋 平七郎

    日本金属学会 2014年秋期講演大会  2014.9.26 

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    Venue:名古屋大学東山キャンパス  

  36. ゲーサイトの脱水により生じる細孔の形態評価

    齊藤 元貴, 坂口 紀史, 秋山 友宏

    粉体工学会2015年度春期研究発表会  2015.5.20 

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    Language:Japanese   Presentation type:Oral presentation (general)  

  37. ゲーサイトの脱水によりヘマタイト中に生じるナノ細孔の形態

    齊藤 元貴, 坂口 紀史, 秋山 友宏

    日本金属学会2015年秋季講演大会  2015.9.17 

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    Language:Japanese   Presentation type:Oral presentation (general)  

  38. ZnO nanoparticles synthesis via solution plasma International conference

    Genki Saito, Norihito Sakaguchi, Tomohiro Akiyama

    10th Japanese-Polish Joint Seminar on Micro and Nano Analysis  2014.10.24 

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  39. Observation of inorganic nanomaterials synthesized by solution plasma International conference

    Genki Saito, Norihito Sakaguchi

    2nd Circular Opening International Symposium  2014.11.3 

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  40. Improved electrochemical properties of Bi and La co-doped LiMn2O4 cathode for Li-ion batteries

    Cheng-Gong Han, Chunyu Zhu, Genki Saito, Tomohiro Akiyama

    日本金属学会 2015年春季講演大会  2015.3.18 

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    Language:English   Presentation type:Poster presentation  

  41. HAADF-STEM法による蛍光体中の希土類原子の分布評価に向けた検討

    齊藤 元貴, 國貞 雄治, 坂口 紀史

    平成27年度公益社団法人日本顕微鏡学会 北海道支部学術講演会  2015.12 

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    Language:Japanese   Presentation type:Oral presentation (general)  

  42. HAADF-STEM法によるα-SiAlON中ドーパントの分析

    齊藤 元貴, 八巻 風太, 坂口 紀史

    日本顕微鏡学会 超高分解能顕微鏡法分科会 合宿研究会  2015.9 

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  43. Ca-α-SiAlON焼結体のHAADF-STEM観察

    坂口 紀史, 八巻 風太, 齊藤 元貴

    日本顕微鏡学会第71回学術講演会  2015.5.14 

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    Language:Japanese   Presentation type:Oral presentation (general)  

  44. 液中グロー放電による酸化亜鉛の作製と構造解析

    齊藤元貴, 細貝聡, 秋山友宏

    日本金属学会 第147回秋期講演大会  2010.9.25 

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    Presentation type:Oral presentation (general)  

    Venue:北海道大学  

  45. 液中グロー放電による各種微粒子の作製と形状制御

    齊藤元貴, 細貝聡, 秋山友宏

    粉体工学会 2010年度春季研究発表会  2010.5.25 

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    Presentation type:Oral presentation (general)  

    Venue:京大会館 京都府  

  46. Synthesis of tin and tin oxide nanoparticles by solution plasma International conference

    G. Saito, T. Akiyama

    3rd NANO TODAY CONFERENCE  2013.12.9 

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    Presentation type:Poster presentation  

    Venue:Matrix, Biopolis, Singapore  

  47. Solution plasma synthesis of metal nanoparticles International conference

    G. Saito, Wan Omar, Sidiq Bin, Wan Mohd Azman, T. Akiyama

    Symposium on Green Energy and Technology 2013  2013.12.12 

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    Presentation type:Oral presentation (general)  

    Venue:Kualalumpur Malaysia  

  48. Solution Glow Discharge for Synthesis of Ni Nanoparticles International conference

    G. Saito, S. Hosokai, T. Akiyama

    13th Asia Pacific Confederation of Chemical Engineering Congress Appche2010  2010.10.6 

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    Presentation type:Oral presentation (general)  

    Venue:Haward International House, Taipei  

  49. Metallic nanoparticles formation from solution plasma using edge-shielded electrode International conference

    G. Saito, S. Hosokai, M. Tsubota, T. Akiyama

    2nd Nano Today Conference  2011.12.13 

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    Presentation type:Poster presentation  

    Venue:Waikoloa Beach, Hawaii  

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Research Project for Joint Research, Competitive Funding, etc. 4

  1. HAADF-STEM法による鋼中複合析出物界面の原子構造解析

    2019.4 - 2020.3

    長舩記念特別研究奨励金 

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    Authorship:Principal investigator  Grant type:Competitive

  2. ポーラスカーボン/ナノ粒子複合体による合金系リチウムイオン電池負極材料の高性能化

    2016.4 - 2017.3

    単年度研究助成 

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    Authorship:Principal investigator  Grant type:Competitive

  3. EELSによるマンガン系複合酸化物の電子状態分析

    2015.4 - 2016.3

    平成27年度 若手研究員等研究助成 

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    Authorship:Principal investigator  Grant type:Competitive

  4. 液中プラズマにより作製したリチウムイオン電池電極材料の特性評価

    2012.4 - 2013.3

    博士後期課程在学生研究助成 

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    Authorship:Principal investigator  Grant type:Competitive

KAKENHI (Grants-in-Aid for Scientific Research) 4

  1. ナノ電子プローブ実・逆空間走査による統合データ駆動型材料物性解析

    Grant number:21H04616  2021.4 - 2025.3

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    武藤 俊介

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    Authorship:Coinvestigator(s)  Grant type:Competitive

  2. Microstructure control of carbon steel based on the investigation of precipitation mechanism of fine precipitates

    Grant number:20K15055  2020.4 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research Grant-in-Aid for Early-Career Scientists  Grant-in-Aid for Early-Career Scientists

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\4290000 ( Direct Cost: \3300000 、 Indirect Cost:\990000 )

  3. Three-dimensional analysis of dopant atoms in phosphors via HAADF-STEM imaging

    Grant number:17K14805  2017.4 - 2019.3

    Saito Genki

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\4290000 ( Direct Cost: \3300000 、 Indirect Cost:\990000 )

    Three-dimensional (3D) distributional analysis of individual dopant atoms in materials is important to understand their properties. In this study, through-focus high-angle annular dark-field (HAADF) imaging was developed for 3D distributional analysis of dopant atoms in phosphors, in which the defocus was changed in narrow steps, and the contrast profile obtained for various depths at each dopant column was analyzed to determine the depth position of dopant atoms. For the analysis of Eu atoms in Ca-α-SiAlON, the effect of convergence semi-angle was investigated using multi-slice image simulation. Because the electron beam tends spread instead of channeling along the atomic columns, the large convergence semi-angle greatly increased the depth resolution. Through-focus HAADF-STEM imaging was used to analyze the Eu atom distribution. The contrast depth profile recorded with a narrow step width clearly analyzed the possible depth positions of Eu atoms.

  4. 液中プラズマによる電池電極材料の開発

    Grant number:13J02072  2013.4 - 2015.3

    日本学術振興会  特別研究員奨励費 

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    Authorship:Principal investigator  Grant type:Competitive

    Grant amount:\2400000

Industrial property rights 3

  1. 窒化アルミニウムの製造方法

    秋山友宏, 仙田竜也, 能村貴宏, 齊籐元貴, 福永豊

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    Application no:特願2018-217577  Date applied:2018.11

    Announcement no:特開2020-83680  Date announced:2020.6

  2. AINファイバー製造方法

    秋山友宏, 平中絢子, 能村貴宏, 齊籐元貴, 仙田竜也

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    Application no:特願2017-141422  Date applied:2017.7

    Announcement no:特開2019-019039  Date announced:2019.2

  3. YAG系蛍光体およびその製造方法

    秋山 友宏, 朱 春宇, 齊藤 元貴, 大山 純平

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    Application no:特願2015-122976  Date applied:2015.6

    Announcement no:特開2017-8162  Date announced:2017.1

    Patent/Registration no:特許6602066  Date registered:2019.10 

 

Teaching Experience (On-campus) 6

  1. 物質科学特別輪講

    2021

  2. ナノ顕微分光物質科学セミナー

    2021

  3. ナノ顕微分光物質科学特別実験及び演習

    2021

  4. 物理工学実験第3

    2021

  5. 物理工学実験第2

    2021

  6. 物理工学実験第1

    2021

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