Search results for: Kuniaki Watanabe

Items from 1 to 20 out of 33 results

article

Erratum to: Phylogeny and biogeography of the genus Stevia (Asteraceae: Eupatorieae): an example of diversification in the Asteraceae in the new world

Akiko Soejima, Akifumi S. Tanabe, Izumi Takayama, Takayuki Kawahara, more

Journal of Plant Research > 2017 > 130 > 6 > 973-973

The online version of the original article can be found at https://doi.org/10.1007/s10265-017-0955-z .

article

Phylogeny and biogeography of the genus Stevia (Asteraceae: Eupatorieae): an example of diversification in the Asteraceae in the new world

Akiko Soejima, Akifumi S. Tanabe, Izumi Takayama, Takayuki Kawahara, more

Journal of Plant Research > 2017 > 130 > 6 > 953-972

The genus Stevia comprises approximately 200 species, which are distributed in North and South America, and are representative of the species diversity of the Asteraceae in the New World. We reconstructed the phylogenetic relationships using sequences of ITS and cpDNA and estimated the divergence times of the major clade of this genus. Our results suggested that Stevia originated in Mexico 7.0–7.3 million...

article

Evaluation of terminal composition of palladium–silver hydrides in plateau region by electronic structure calculations

Masanori Hara, Hiroto Fujinami, Satoshi Akamaru, Norio Nunomura, more

Journal of Alloys and Compounds > 2013 > 580 > Supplement 1 > S202-S206

The electronic structures of palladium, palladium–silver alloys (Pd–Ag) and their hydrides were calculated to evaluate the terminal composition in the plateau region in the pressure–composition isotherm. The electronic structures were calculated by the Korringa–Kohn–Rostoker coherent potential approximation (KKR-CPA), MACHIKANEYAMA 2002 developed by Akai. The Fermi level of palladium at various hydrogen...

article

Alloying effects on the hydride formation of Zr(Mn1−xCox)2

Masanori Hara, Kaori Yudou, Emiko Kinoshita, Kayoko Okazaki, more

International Journal of Hydrogen Energy > 2011 > 36 > 19 > 12333- 12337

To study the alloying effects on ZrMn ₂ –H system, thermodynamic properties of Zr(Mn _1−x Co _x ) ₂ hydride were measured by volumetric method. ZrMn ₂ gave a single plateau region in the pressure–composition isotherm. On the other hand, double plateaus were clearly observed in Zr(Mn _0.7 Co _0.3 ) ₂ and Zr(Mn _0.6 Co _0.4 )...

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Temperature driven hydrogen-induced disproportionation of Zr2Cu

Masanori Hara, Yukiko Hayashi, Kuniaki Watanabe

Journal of Alloys and Compounds > 2009 > 487 > 1-2 > 489-493

The absorption of hydrogen by Zr ₂ Cu was studied by the aid of the Zr ₂ Cu–H phase diagram elaborated by Kadel and Weiss. It was found that Zr ₂ Cu hydride was formed at ambient temperature after moderate hydrogen absorption. Hydrogen-induced disproportionation of Zr ₂ Cu occurred at temperatures exceeding 550K. The unknown compound of the γ phase reported by Kadel...

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Hydrogen-induced magnetic and structural transformations of GdCu

Masanori Hara, Naomi Hatakeyama, Satoshi Akamaru, Kuniaki Watanabe, more

Journal of Magnetism and Magnetic Materials > 2009 > 321 > 5 > 423-428

The magnetization of GdCu induced by hydrogen uptake was measured within the temperature range of 4.2 to 300K, occurring phase changes were followed by X-ray diffraction measurements at ambient temperature. The prepared GdCu powder of CsCl-type structure readily absorbed hydrogen at ambient temperature, where hydrogen pressure was below 100kPa. Hydrogenation changed the magnetism of GdCu in a complex...

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Improvement of high temperature stability of Pd coating on Nb by intermediate layer comprising NbC and Nb2C

Yuji Hatano, Keita Ishiyama, Hirofumi Homma, Kuniaki Watanabe

Journal of Alloys and Compounds > 2007 > 446-447 > Complete > 539-542

Non-porous intermediate layers comprising NbC and Nb ₂ C were prepared between thin Pd films (100nm) and Nb substrates, and the high temperature stability (573–873K) of Pd coating was examined by hydrogen absorption experiments. This type of intermediate layer provided better stability of Pd coating at/below 673K than the layers consisting solely of Nb ₂ C. Sharp reduction and recovery...

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Improvement in high temperature stability of Pd coating on Nb by Nb2C intermediate layer

Yuji Hatano, Keita Ishiyama, Hirofumi Homma, Kuniaki Watanabe

International Journal of Hydrogen Energy > 2007 > 32 > 5 > 615-619

Niobium subcarbide (Nb ₂ C) was chosen as a material for non-porous intermediate layer to improve the high temperature durability of Pd–Nb composite membranes for hydrogen separation. A layer of Nb ₂ C was prepared between Nb substrate and thin Pd films (100nm), and the stability of Pd coating at elevated temperatures (573–773K) was examined by hydrogen absorption experiments. Hydrogen...

article

Effect of a magnesium depletion on the Mg–Ni–Y alloy hydrogen absorption properties

Masanori Hara, Shotaro Morozumi, Kuniaki Watanabe

Journal of Alloys and Compounds > 2006 > 414 > 1-2 > 207-214

To improve the hydrogen absorption properties of Mg ₂ Ni, three kinds of specimens were prepared. They were denoted as MGNIY, DeMg–MGNIY and DeMg–MIX. The first one was a cast Mg–Ni–Y alloy, the second was prepared by vacuum heating of MGNIY to remove some part of Mg and the third was prepared by vacuum heating of a mixture of pulverized Mg–Y and Mg ₂ Ni. The term DeMg denotes removal...

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Phase transition and electrochemical capacitance of mechanically treated manganese oxides

Akira Taguchi, Sachio Inoue, Satoshi Akamaru, Masanori Hara, more

Journal of Alloys and Compounds > 2006 > 414 > 1-2 > 137-141

Mechanical grinding (MG) leads to a sequential phase transition of γ-MnO ₂ to form the thermodynamically stable α-Mn ₂ O ₃ and, subsequently, Mn ₃ O ₄ depending on the duration of MG treatment. By MG treatment for 150h, α-Mn ₂ O ₃ became a predominant species. A subsequent transition to Mn ₃ O ₄ was observed on further MG treatment...

article

Surface modification of polymer microparticles using a hexagonal-barrel sputtering system

Takayuki Abe, Satoshi Akamaru, Kuniaki Watanabe, Y. Honda

Journal of Alloys and Compounds > 2005 > 402 > 1-2 > 227-232

Surfaces of spherical polymer microparticles with three different sizes (50, 12 and 5μm in diameter) were modified with platinum using the hexagonal barrel equipped RF sputtering system. It was found that the surfaces of particles could be uniformly coated with Pt layers, regardless of their sizes. It should be noticed that the present system made it possible to form a uniform Pt-layer over a polymer...

article

Effects of bulk modification by Pd on electrochemical properties of MgNi

Tiejun Ma, Yuji Hatano, Takayuki Abe, Kuniaki Watanabe

Journal of Alloys and Compounds > 2005 > 391 > 1-2 > 313-317

An amorphous MgNi alloy was prepared by ball-milling of Mg ₂ Ni and Ni with 10mol% of Pd for 80h, and effects of the bulk modification by Pd on the electrochemical properties of amorphous MgNi were investigated by using a conventional two-electrode system. It was found through X-ray diffraction (XRD) and high-resolution transmission electron microscope (HRTEM) analyses that Pd dissolved uniformly...

article

Surface modification of Al ₂ O ₃ ceramic grains using a new RF sputtering system developed for powdery materials

Takayuki Abe, Satoshi Akamaru, Kuniaki Watanabe

Journal of Alloys and Compounds > 2004 > 377 > 1-2 > 194-201

A new RF sputtering system installed with a hexagonal-barrel was developed for modifying the surfaces of powdery materials. The validity of this system was examined for surface coating of three kinds of Al ₂ O ₃ powders with different grain shapes and sizes. It was found that the surfaces of powder grains could be uniformly coated with Pt layers, regardless of their shapes and sizes...

article

Influence of heat treatment on hydrogen ingress into V-4Cr-4Ti alloy

Ryo Hayakawa, Yuji Hatano, Ken-ichi Fukumoto, Hideki Matsui, more

Journal of Nuclear Materials > 2004 > 329-333 > Part A > 411-415

Specimens of V-4Cr-4Ti alloy were heated at 1273 K in vacuum, and the influence of this heat treatment on H ₂ absorption was examined at temperatures from 523 to 1023 K under the presence of water vapor of 10 ^- ⁵ Pa. The rate of H ₂ absorption was significantly reduced by the heat treatment in the temperature range examined. Such reduction in the absorption rate was ascribed...

article

Effects of Pd addition on electrochemical properties of MgNi

Tiejun Ma, Yuji Hatano, Takayuki Abe, Kuniaki Watanabe

Journal of Alloys and Compounds > 2004 > 372 > 1-2 > 251-258

Two kinds of Pd-modified MgNi were prepared and effects of Pd addition on the electrochemical properties of MgNi were investigated. Sample I was prepared by ball-milling amorphous MgNi with Pd (1, 6 and 10mol%) for 10min, 2 and 10h, and sample II was obtained by ball-milling Mg ₂ Ni and Ni with 10mol% Pd for 80h. The effects of Pd-modification for sample I depended on both Pd ratio and time...

article

XRD and electrochemical measurements of RuO ₂ powder treated by using a mechanical grinding method

Takayuki Abe, Sachio Inoue, Kuniaki Watanabe

Journal of Alloys and Compounds > 2003 > 358 > 1-2 > 177-181

Atomization, crystallinity, and electrochemical characteristics of powdery RuO ₂ treated by mechanical grinding (MG) were examined. XRD analysis, N ₂ adsorption/desorption measurements, and TEM observations showed that MG generated isotropic and rapid atomization of RuO ₂ particles in the initial stage of treatment (up to 190 h). Further MG resulted in gentle atomization with...

article

Hydrogen-induced disproportionation of Zr ₂ M (M=Fe, Co, Ni) and reproportionation

Masanori Hara, Ryo Hayakawa, Yoshinobu Kaneko, Kuniaki Watanabe

Journal of Alloys and Compounds > 2003 > 352 > 1-2 > 218-225

Hydrogen induced disproportionation and reproportionation for Zr ₂ Fe, Zr ₂ Co and Zr ₂ Ni were studied by means of volumetric measurements of hydrogen absorption and desorption, and X-ray diffraction analyses of the product phases. These alloys formed respective hydrides of Zr ₂ MH ₅ (M=Fe, Co and Ni) type at room temperature only under conditions of very slow...

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Electrochemical studies of the effect of surface modification of amorphous MgNi electrodes by carbon or Ni

Takayuki Abe, Sachio Inoue, Daobin Mu, Yuji Hatano, more

Journal of Alloys and Compounds > 2003 > 349 > 1-2 > 279-283

The effect of surface modification of amorphous MgNi by carbon or Ni was examined by conventional charge/discharge cycle tests and by a newly developed micro-paste electrode method. The change/discharge tests showed that the surface modification by Ni had no effect on the capacity degradation of amorphous MgNi. The carbon modification, however, clearly improved the degradation; the discharge capacity...

article

Solid state reaction between tungsten and amorphous carbon

Yuji Hatano, Miyuki Takamori, Kenji Matsuda, Susumu Ikeno, more

Journal of Nuclear Materials > 2002 > 307-311 > Part 2 > 1339-1343

The solid state reaction between tungsten and amorphous carbon was studied at 973, 1073 and 1173 K. An amorphous carbon film was deposited onto a tungsten sheet by vacuum evaporation. The specimens thus prepared were heated at given temperatures, and the time dependence of carbide growth was examined by means of X-ray diffraction. No carbide appeared at 973 K within 240 min. On the other hand, the...

article

Surface segregation and oxidation of Ti in a V–Ti alloy

Ryo Hayakawa, Yuji Hatano, Katsuhiko Fujii, Ken-ichi Fukumoto, more

Journal of Nuclear Materials > 2002 > 307-311 > Part 1 > 580-584

The oxidation and reduction of surface oxides of the V–4%Ti alloy were examined by X-ray photoelectron spectroscopy. A specimen sheet of the alloy covered by oxide films was heated between 513 and 1223 K for 10 min in vacuum. Vanadium oxides started to be reduced to the metallic state at 673 K owing to oxygen dissolution in the bulk, while titanium remained in oxidized states up to 983 K. Titanium...

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Search results for: Kuniaki Watanabe

Erratum to: Phylogeny and biogeography of the genus Stevia (Asteraceae: Eupatorieae): an example of diversification in the Asteraceae in the new world

Phylogeny and biogeography of the genus Stevia (Asteraceae: Eupatorieae): an example of diversification in the Asteraceae in the new world

Evaluation of terminal composition of palladium–silver hydrides in plateau region by electronic structure calculations

Alloying effects on the hydride formation of Zr(Mn1−xCox)2

Temperature driven hydrogen-induced disproportionation of Zr2Cu

Hydrogen-induced magnetic and structural transformations of GdCu

Improvement of high temperature stability of Pd coating on Nb by intermediate layer comprising NbC and Nb2C

Improvement in high temperature stability of Pd coating on Nb by Nb2C intermediate layer

Effect of a magnesium depletion on the Mg–Ni–Y alloy hydrogen absorption properties

Phase transition and electrochemical capacitance of mechanically treated manganese oxides

Surface modification of polymer microparticles using a hexagonal-barrel sputtering system

Effects of bulk modification by Pd on electrochemical properties of MgNi

Surface modification of Al ₂ O ₃ ceramic grains using a new RF sputtering system developed for powdery materials

Influence of heat treatment on hydrogen ingress into V-4Cr-4Ti alloy

Effects of Pd addition on electrochemical properties of MgNi

XRD and electrochemical measurements of RuO ₂ powder treated by using a mechanical grinding method

Hydrogen-induced disproportionation of Zr ₂ M (M=Fe, Co, Ni) and reproportionation

Electrochemical studies of the effect of surface modification of amorphous MgNi electrodes by carbon or Ni

Solid state reaction between tungsten and amorphous carbon

Surface segregation and oxidation of Ti in a V–Ti alloy

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