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5. Morphology and chemical state of platinum ions implanted into glassy carbon substrates.

Author

Kimata, Tetsuya, Kato, Sho, Kobayashi, Tomohiro, Yamamoto, Shunya, Yamaki, Tetsuya, and Terai, Takayuki

Subjects
X-ray photoelectron spectroscopy, PLATINUM, TRANSMISSION electron microscopy, CRYSTAL defects, CHARGE exchange, DEPTH profiling
Abstract

Glassy carbon substrates were implanted with 100 keV platinum ions. The implanted samples were analyzed using cross-sectional transmission electron microscopy (TEM) and x-ray photoelectron spectroscopy. Ion beam sputtering significantly affected the depth profile during platinum-ion implantation. Cross-sectional TEM revealed that the implanted platinum atoms were in the amorphous state and did not aggregate. Chemical state analysis of the platinum-ion-implanted glassy carbon substrates suggested that lattice defects in the substrates owing to the platinum-ion implantation caused the platinum–carbon interaction with electron transfer from platinum to carbon. [ABSTRACT FROM AUTHOR]

Published
2022
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22. Platinum nanoparticles prepared by ion implantation exhibit high durability for fuel cell applications.

Author

Kimata, Tetsuya, Kato, Sho, Kobayashi, Tomohiro, Yamamoto, Shunya, Yamaki, Tetsuya, and Terai, Takayuki

Subjects
PLATINUM nanoparticles, ION implantation, PROTON exchange membrane fuel cells, FUEL cells, MAGNETRON sputtering, HEAT treatment
Abstract

Proton exchange membrane fuel cells (PEMFCs) have attracted considerable attention as distributed power sources for automotive and residential applications. In PEMFCs, platinum (Pt) nanoparticles supported on carbon materials are used as electrocatalysts for oxygen reduction reactions. However, improved durability of the electrocatalysts is urgently required for commercialization purposes. We describe an ion implantation technique for the preparation of Pt nanoparticles with superior catalytic properties, suitable for fuel cell applications. The Pt nanoparticles were obtained by implanting a glassy carbon (GC) substrate with 100 keV Pt-ions, followed by electrochemical etching and a heat treatment. Electrochemical measurements of the Pt nanoparticles prepared by the proposed implantation technique demonstrated superior durability when compared to those prepared by the conventional magnetron sputtering method. We suggested that the defective structure of the GC substrate, caused by the Pt-ion implantation, has led to the improved electrochemical stability of the GC substrate and Pt-carbon support interactions, thereby enhancing the durability of our Pt nanoparticles. [ABSTRACT FROM AUTHOR]

Published
2023
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32. Lithium Vapor Chemistry of Hyper-Stoichiometric Lithium Metatitanate Li₂.₁₂(₂)TiO₃+y

Author

Mukai, Keisuke, Yasumoto, Masaru, and Terai, Takayuki

Abstract

Developing a better ceramic breeder (Li-containing oxide) is a key challenge for realizing fuel-self-sufficient fusion reactors. Ceramic breeder pebbles of hyper-stoichiometric lithium metatitanate, Li2+xTiO3+y (Li/Ti > 2), have been developed for a demonstration fusion reactor as high Li density enhances fuel tritium production. Previous studies have reported that Li loss by vaporization at high temperatures was largely enhanced by the increase in Li/Ti ratio and environmental moisture concentration. Minimizing the Li loss is a key issue for sufficient tritium breeding and reduced corrosion of structural steel. However, a suitable environmental parameter for hyper-stoichiometric Li2+xTiO3+y pebbles has not yet been determined because of the unavailability of thermodynamic data. Herein, a solid/gas equilibria for Li2.12(2)TiO3+y was investigated by measuring vapor pressures using atmosphere controllable Knudsen cell high temperature mass spectrometry. The enhanced thermodynamic activities of Li and Li2O in Li2.12(2)TiO3+y in comparison with those in stoichiometric Li2TiO3 were obtained as functions of temperature and oxygen concentration. The equilibrium constants were used to achieve the optimum moisture concentration that can suppress the vapor reactions in a cylindrical breeding zone with inhomogeneous temperature distribution.

Published
2020

33. Platinum nanoparticles on HOPG surface modified by 380 keV Ar+ irradiation: TEM and Raman studies

Author

Kimata, Tetsuya, Kakitani, Kenta, Yamamoto, Shunya, Yamaki, Tetsuya, Terai, Takayuki, and G.Nakamura, Kazutaka

Abstract

炭素担体に導入されたイオンビーム誘起欠陥は、炭素担体上に堆積した白金（Pt）ナノ微粒子の触媒活性を向上させる。本研究では、炭素への欠陥導入によるPt微粒子の形成への影響について調べた。実験では、高配向性熱分解グラファイト（HOPG）表面に380 keV Ar+を照射し、その表面にRFマグネトロンスパッタリングでPt微粒子を堆積することで試料を作製した。Pt微粒子サイズ及びPt-HOPG界面におけるグラファイト構造を透過型電子顕微鏡（TEM）観察及びラマン分光測定により評価した。TEM観察から照射したHOPG表面上のPt微粒子は、未照射HOPG上のPt微粒子に比べてそのサイズが大きくなることが分かった。また、ラマン分光測定では、Ar照射量1.0×1012 ions/cm2でグラファイト構造に空孔欠陥が生成され始め、5.0×1013 ions/cm2よりも大きい照射量でsp3欠陥が生成されることが示された。イオンビーム誘起欠陥を有するグラファイト構造がPtの粒成長を促進したと示唆された。

Published
2020

43. Present status of Japanese tasks for lithium target facility under IFMIF/EVEDA

Author

Nakamura, Kazuyuki, Furukawa, Tomohiro, Hirakawa, Yasushi, Kanemura, Takuji, Kondo, Hiroo, Ida, Mizuho, Niitsuma, Shigeto, Ohtaka, Masahiko, Watanabe, Kazuyoshi, Horiike, Hiroshi, Hoashi, Eiji, Suzuki, Sachiko, Yamaoka, Nobuo, Sugiura, Hirokazu, Terai, Takayuki, Suzuki, Akihiro, Yagi, Juro, Bannai, Mikiko, Fukada, Satoshi, Nakamura, Hiroo, Edao, Yuki, Tsuji, Yoshiyuki, and Furuya, Kazuyuki

Published
2011
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