研究者詳細 - 徳永　智春

論文 - 徳永　智春

分割表示 149 件中 81 - 100 件目／全件表示 >>

Small Nanosized Oxygen-Deficient Tungsten Oxide Particles: Mechanistic Investigation with Controlled Plasma Generation in Water for Their Preparation 査読有り国際誌

Ishida, Y; Motono, S; Doshin, W; Tokunaga, T; Tsukamoto, H; Yonezawa, T

ACS OMEGA 2 巻 ( 8 ) 頁： 5104 - 5110 2017年8月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：ACS Omega

Production of oxygen-deficient tungsten oxide nanoparticles with a diameter of around 10 nm have been successfully developed using a microwave-induced plasma in liquid technique. The prepared blue-green nanoparticles exhibit strong absorption in the visible region; thus, these could be efficient visible-light photocatalysts. The high-angle annular dark-field images revealed the dislocation of tungsten, which causes oxygen deficiencies.

DOI： 10.1021/acsomega.7b00986

Web of Science

Scopus

PubMed

Nanophase-separated Ni<sub>3</sub>Nb as an automobile exhaust catalyst 国際誌

Tanabe, T; Imai, T; Tokunaga, T; Arai, S; Yamamoto, Y; Ueda, S; Ramesh, GV; Nagao, S; Hirata, H; Matsumoto, S; Fujita, T; Abe, H

CHEMICAL SCIENCE 8 巻 ( 5 ) 頁： 3374 - 3378 2017年5月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Chemical Science

Catalytic remediation of automobile exhaust has relied on precious metals (PMs) including platinum (Pt). Herein, we report that an intermetallic phase of Ni and niobium (Nb) (i.e., Ni3Nb) exhibits a significantly higher activity than that of Pt for the remediation of the most toxic gas in exhaust (i.e., nitrogen monoxide (NO)) in the presence of carbon monoxide (CO). When subjected to the exhaust-remediation atmosphere, Ni3Nb spontaneously evolves into a catalytically active nanophase-separated structure consisting of filamentous Ni networks (thickness < 10 nm) that are incorporated in a niobium oxide matrix (i.e., NbOx (x < 5/2)). The exposure of the filamentous Ni promotes NO dissociation, CO oxidation and N2 generation, and the NbOx matrix absorbs excessive nitrogen adatoms to retain the active Ni sites at the metal/oxide interface. Furthermore, the NbOx matrix immobilizes the filamentous Ni at elevated temperatures to produce long-term and stable catalytic performance over hundreds of hours.

DOI： 10.1039/c6sc05473k

Web of Science

Scopus

PubMed

Methane decomposition for hydrogen production by catalytic activity of carbon black under low flow rate conditions

Tokunaga, T; Kishi, N; Yamakawa, K; Sasaki, K; Yamamoto, T

JOURNAL OF THE CERAMIC SOCIETY OF JAPAN 125 巻 ( 4 ) 頁： 185 - 189 2017年4月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Journal of the Ceramic Society of Japan

Recently, carbon materials were reported to work as catalysts for the production of H3 from hydrocarbons. However, the hydrogen production rate is extremely low. To broaden the scope of carbon materials as catalysts for the decomposition of hydrocarbons, a higher H3 production rate is required. Thus, the hydrogen production rate under conditions employing a low flow rate of hydrocarbon per unit area and a large quantity of carbon materials as the catalyst should be evaluated, and the influence of these conditions on the rate of H3 production by carbon materials should be discussed. Herein, the H3 production rate was measured under conditions employing a low flow rate of CH4 and a large quantity of carbon black (CB) as a catalyst. H3 production started at 600°C and the production rate was less than 0.1%. The transmission electron microscope image of CB heated in CH4 atmosphere demonstrated that a low flow rate of CH4 does not affect the reaction site (i.e., graphite edges) of CB. However, the H3 production rate was extremely low compared to that achieved with a high flow rate. It is proposed that there is an optimal flow rate for maintaining the catalytic activity at the graphite edge of CB for decomposition of CH4.

DOI： 10.2109/jcersj2.16246

Web of Science

Scopus

Preparation of Au/Pd Bimetallic Nanoparticles by a Microwave-Induced Plasma in Liquid Process

Shirai, H; Nguyen, MT; Cempel, D; Tsukamoto, H; Tokunaga, T; Liao, YC; Yonezawa, T

BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN 90 巻 ( 3 ) 頁： 279 - 285 2017年3月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：Bulletin of the Chemical Society of Japan

Au/Pd alloy nanoparticles (NPs) were successfully synthesized using HAuCl4, H2PdCl4, and α-thioglycerol as precursors and a stabilizer, respectively, by microwave-induced plasma in liquid process (MWPLP). After only several minutes of microwave irradiation, metallic NPs were obtained in aqueous environment without any reducing agent. The reduction mechanism of metal ions was confirmed by UV-vis spectral changes. The results from HAADF-STEM and EDS indicated that synthesized NPs were bimetallic Au/Pd. Moreover, XRD patterns of synthesized NPs implied that the composition of bimetallic NPs could be controlled by changing the initial ratio of metal precursors.

DOI： 10.1246/bcsj.20160333

Web of Science

Scopus

Directly determining the polarity of WC grains in WC-12 wt%Co alloy by ABF-STEM 査読有り

Hayashi, Y; Tokunaga, T; Sasaki, K; Yamamoto, T

INTERNATIONAL JOURNAL OF REFRACTORY METALS & HARD MATERIALS 62 巻頁： 9 - 13 2017年1月

記述言語：英語掲載種別：研究論文（学術雑誌）出版者・発行元：International Journal of Refractory Metals and Hard Materials

WC grains in WC–Co alloys are shaped as truncated triangular prisms, each with a basal plane of a (0001) truncated triangle and two {11̅00} prismatic planes, one narrower and one wider. This anisotropic shape is related to the polarity of the WC lattice, which comes from the difference in the spacing of the W and C layers in the (0001) projection. We directly determined the relationship between the two {11̅00} prismatic planes and the polarity of the WC lattice by using high-resolution scanning transmission electron microscopy (STEM). High-angle annular dark-field STEM and annular bright-field STEM revealed that the wider prismatic plane had W and C atomic layers with a shorter spacing, while the narrower plane had a longer spacing. The WC/Co interface on the wider prismatic side was atomically flat, while many steps formed on the surface of the narrower prismatic side. This difference in step formation at these interfaces could have come from the difference in how their W[sbnd]C bonds formed.

DOI： 10.1016/j.ijrmhm.2016.10.013

Web of Science

Scopus

Methane Decomposition for Hydrogen Production by Catalytic Activity of Carbon Black under Low Flow Rate Conditions

Tomoharu Tokunaga, Naoyuki Kishi, Kenya Yamakawa, Katsuhiro Sasaki, Takahisa Yamamoto

ACS-Japan 125 巻 ( 4 ) 頁： 185-189 2017年

Water transport phenomena through membranes consisting of vertically-aligned double-walled carbon nanotube array

Hidetoshi Matsumoto, Shuji Tsuruoka, Yasuhiko Hayashi, Koji Abe, Kenjiro Hata, Shaoling Zhang, Yoshitaka Saito, Motohiro Aiba, Tomoharu Tokunaga, Toru Iijima, Takuma Hayashi

Carbon 120 巻頁： 358–365 2017年

Nanophase-separated Ni3Nb as Automobile Exhaust Catalysts 査読有り

Toyokazu Tanabe, Tsubasa Imai, Tomoharu Tokunaga, Shigeo Arai, Yuta Yamamoto, Shigenori Ueda, Gubbala V. Ramesh, Satoshi Nagao, Hirohito Hirata, Shin-ichi, Matsumoto, Takeshi Fujita, Hideki Abe

Chemical Science 8 巻頁： 3374-3378 2017年

Preparation of Au/Pd bimetallic nanoparticles by a microwave-induced plasma in liquid process 査読有り

Hiroaki Shirai, Mai Thanh Nguyen, David Čempel, Hiroki Tsukamoto, Tomoharu Tokunaga, Ying-Chih Liao, and Tetsu Yonezawa

Bulletin of the Chemical Society of Japan 90 巻 ( 3 ) 頁： 279-285 2017年

Intentionally Encapsulated Metal Alloys within Vertically Aligned Multi-Walled Carbon Nanotube Array via Chemical Vapor Deposition Technique

Hayashi Yasuhiko, Inoue Hirotaka, Hayashi Takuma, Hada Masaki, Nishikawa Takeshi, Tokunaga Tomoharu, Amaratunga G. A. J.

2017 IEEE INTERNATIONAL CONFERENCE ON MANIPULATION, MANUFACTURING AND MEASUREMENT ON THE NANOSCALE (3M-NANO) 頁： 357-361 2017年

Intentionally Encapsulated Metal Alloys within Vertically Aligned Multi-Walled Carbon Nanotube Array via Chemical Vapor Deposition Technique 査読有り

Yasuhiko Hayashi, Hirotaka Inoue, Takuma Hayashi, Masaki Hada, Takeshi Nishikawa, Tomoharu Tokunaga, G. A. J. Amaratunga

2017 IEEE INTERNATIONAL CONFERENCE ON MANIPULATION, MANUFACTURING AND MEASUREMENT ON THE NANOSCALE (3M-NANO) 頁： 357 - 361 2017年

記述言語：英語掲載種別：研究論文（国際会議プロシーディングス）出版者・発行元：IEEE

This paper presents a growth and characterization of vertically aligned PdxCo1-x alloy encapsulated inside Multi-Walled Carbon Nanotube (MWCNT) arrays on Pd/Co thin layers coated on Si substrate by a dc bias-enhanced plasma chemical vapor deposition (CVD) method. The Metal Alloy Encapsulated within MWCNTs (MAE-MWCNTs) were characterized by a scanning electron microscope (SEM) and a transmission electron microscopy (TEM). The SEM images show the teardrop-shape particles encapsulated within the tube top of MWCNTs. A vibrating sample magnetometer was used to study the magnetism of a large number of MAE-MWCNTs on Si substrate at room temperature. The hysteresis loop of the ME-MWCNTs shows clear ferromagnetic behavior and the easy axis of magnetization is parallel to the MEA-MWCNT tube axis, as can be elucidated from the large coercive fields and remanence values. Moreover, TEM off-axis electron holograms were used to study the magnetism of the individual MAE-MWCNT or the two pair of MAE-MWCNTs. Based on electron holography, we have successfully obtained the saturation magnetization of 0.7 T and 1.12 T for the individual MAE-MWCNT with diameters of 41 nm and 83 nm, respectively.

Web of Science

Double target sputtering into liquid 査読有り

Mai Thanh Nguyen, Tetsu Yonezawa, Yuan Wang, Tomoharu Tokunaga

Materials Letters 171 巻 ( 15 ) 頁： 75-78 2016年

Earth-Abundant and Durable Nanoporous Catalyst for Exhaust-Gas Conversion 査読有り

Takeshi Fujita,Hideki Abe,Toyokazu Tanabe,Yoshikazu Ito,Tomoharu Tokunaga,Shigeo Arai,Yuta Yamamoto,Akihiko Hirata,Mingwei Chen

Advanced Functional Materials 頁： 1-8 2016年

Hard-Templating Synthesis of Macroporous Platinum Microballs 査読有り

Hiroaki Shirai, Yu-Yuan Huang, Tetsu Yonezawa,* Wei-Chen Chang, Tomoharu Tokunaga, Saad Alshehri, Bo Jiang, Yusuke Yamauchi, and Kevin C.-W. Wu

Materials Letters 164 巻 ( 1 ) 頁： 488-492 2016年

Synthesis of zirconium oxynitride in air under DC electric fields 査読有り

Nobuhiro Morisaki, Hidehiro Yoshida, Koji Matsui, Tomoharu Tokunaga, Katsuhiro Sasaki, Takahisa Yamamoto

Applied Physics Letter 109 巻頁： 083104(1)- 083104(4) 2016年

Formation of grain boundary second phase in BaTiO3 polycrystal under a high DC electric field at elevated temperatures 査読有り

Hidehiro YOSHIDA, Akinori UEHASHI, Tomoharu TOKUNAGA, Katsuhiro SASAKI, Takahisa YAMAMOTO

Journal of the Ceramic Society of Japan 124 巻 ( 4 ) 頁： 388-392 2016年

Matrix Sputtering into Liquid Mercaptan: From Blue-Emitting Copper Nanoclusters to Red-Emitting Copper Sulfide Nanoclusters 査読有り

Matteo Porta, Mai Thanh Nguyen, Tomoharu Tokunaga, Yohei Ishida, Wei-Ren Liu, Tetsu Yonezawa

Langmuir 32 巻頁： 12159-12165 2016年

Matrix Sputtering into Liquid Mercaptan: From Blue-Emitting Copper Nanoclusters to Red-Emitting Copper Sulfide Nanoclusters 査読有り

Matteo Porta, Mai Thanh Nguyen, Tomoharu Tokunaga, Yohei Ishida, Wei-Ren Liu, Tetsu Yonezawa

Langmuir 32 巻頁： 12159-12165 2016年

Plasma-Induced Tungsten Doping of TiO2 Nanoparticles for Enhanced Photocatalysis using Visible Light 査読有り

17 巻 ( 38 ) 頁： 24556-24559 2015年

Hard-Templating Synthesis of Macroporous Platinum Microballs (MPtM) 査読有り

Hiroaki Shirai, Yu-Yuan Huang, Tetsu Yonezawa,* Wei-Chen Chang, Tomoharu Tokunaga, Saad Alshehri, Bo Jiang, Yusuke Yamauchi, and Kevin C.-W. Wu

Materials Letters 164 巻 ( 1 ) 頁： 488-492 2015年

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