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Journal Articles

Neutron computed tomography of phase separation structures in solidified Cu-Co alloys and investigation of relationship between the structures and melt convection during solidification

Shoji, Eita*; Isogai, Shosei*; Suzuki, Rikuto*; Kubo, Masaki*; Tsukada, Takao*; Kai, Tetsuya; Shinohara, Takenao; Matsumoto, Yoshihiro*; Fukuyama, Hiroyuki*

Scripta Materialia, 175, p.29 - 32, 2020/01

 Times Cited Count:17 Percentile:79.05(Nanoscience & Nanotechnology)

Journal Articles

Effects of vibrational and rotational excitations on the dissociative adsorption of O$$_{2}$$ on Cu surfaces

Moritani, Kosuke*; Tsuda, Muneyuki*; Teraoka, Yuden; Okada, Michio*; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Kasai, Toshio*; Kasai, Hideaki*

Journal of Physical Chemistry C, 111(27), p.9961 - 9967, 2007/07

 Times Cited Count:14 Percentile:46.01(Chemistry, Physical)

We report an X-ray photoemission study of the dissociative adsorption of O$$_{2}$$ at Cu(111), (001), and (110) surfaces with an O$$_{2}$$ molecular beam generated with a variable temperature nozzle. The O-uptake curves, which are produced from precisely measured O-1s peaks, indicate that the dissociative absorption is enhanced as the nozzle temperature is increased up to 1000 K for the normal incidence of O$$_{2}$$ at a kinetic energy of 0.5 eV. However, further increasing the nozzle temperature to 1400 K reduces the probability of dissociativeadsorption. These results suggest that vibrational excitations of incident O$$_{2}$$ assist dissociative adsorption while rotational excitations hinder it.

Journal Articles

Comparative study of oxidation on Cu and Cu$$_{3}$$Au surfaces with a hyperthermal O$$_{2}$$ molecular beam

Okada, Michio*; Moritani, Kosuke; Fukuyama, Tetsuya*; Mizutani, Hironori*; Yoshigoe, Akitaka; Teraoka, Yuden; Kasai, Toshio*

Surface Science, 600(18), p.4228 - 4232, 2006/09

 Times Cited Count:20 Percentile:64.51(Chemistry, Physical)

Dissociative adsorption of hyperthermal O$$_{2}$$ molecules on Cu$$_{3}$$Au(100) was investigated by X-ray photoemission spectroscopy in conjunction with a synchrotron light source. Comparing the O-uptake curve on Cu$$_{3}$$Au with that on Cu, it was found that the dissociative adsorption of O$$_{2}$$ is more activated (less reactive) due to Au alloying. The low-energy electron-diffraction (LEED) pattern of c(2$$times$$2) for the clean surface turned into the (1$$times$$1) LEED pattern during the oxidation by hyperthermal O$$_{2}$$ molecular beam, suggesting that the O adsorption induces the Cu-atom segregation on the surface.

Journal Articles

The Azimuthal dependent oxidation process on Cu(110) by energetic oxygen molecules

Moritani, Kosuke; Okada, Michio*; Fukuyama, Tetsuya*; Teraoka, Yuden; Yoshigoe, Akitaka; Kasai, Toshio*

European Physical Journal D, 38(1), p.111 - 115, 2006/04

 Times Cited Count:14 Percentile:54.5(Optics)

We report a study on the oxidation process induced by a hyperthermal oxygen molecular beam (HOMB) on Cu(110) using X-ray photoemission spectroscopy in conjunction with a synchrotron radiation source. The oxidation process induced by energetic O$$_{2}$$ beams on Cu(110), depending on the azimuthal angle of incidence, suggests that the -Cu-O- added row structure has a role in inhibiting adsorption as a steric obstacle for incident O$$_{2}$$ molecules.

Journal Articles

Surface chemical reaction dynamics illuminated by high brilliance and high energy-resolution synchrotron radiation; In-situ photoemission spectroscopy for surface oxidation induced by supersonic O$$_{2}$$ molecular beams

Teraoka, Yuden; Yoshigoe, Akitaka; Moritani, Kosuke; Takakuwa, Yuji*; Ogawa, Shuichi*; Ishizuka, Shinji*; Okada, Michio*; Fukuyama, Tetsuya*; Kasai, Toshio*

Hoshako, 18(5), p.298 - 309, 2005/09

Representative research results in surface reaction dynamics, performed at a surface chemistry experimental station installed in the JAEA soft X-ray beamline in the SPring-8, were reviewed. As a research result in JAEA, SiO desorption mechanisms in the Si(001) oxidation at high temperature were introduced. As a collaboration with Osaka University on oxidation reaction dynamics of Cu, collision-induced atom absorption process was introduced. As a collaboration with Tohoku University on Ti(0001) oxidation reaction dynamics, it was introduced that two peaks, found in an incident energy dependence of initial sticking probability, were corresponding to potential energy barriers of dissociative adsorption of O$$_{2}$$ molecules.

Journal Articles

Full characterization of an intense pulsed hyperthermal molecular beam

Watanabe, Daisuke*; Che, D.-C.*; Fukuyama, Tetsuya*; Hashinokuchi, Michihiro*; Teraoka, Yuden; Kasai, Toshio*

Review of Scientific Instruments, 76(5), p.055108_1 - 055108_5, 2005/05

 Times Cited Count:6 Percentile:33.47(Instruments & Instrumentation)

A molecular beam technique for generating an intense pulsed hyperthermal molecular beam (HTMB) was developed. The beam source consists of a pulse valve, a cooling-water bottle that protectes the pulse valve from heat transfer of a high temperature nozzle, and the nozzle with a heater. The pulsed HTMB of HCl was practically generated and characterized by means of (2+1) resonance-enhanced multiphoton ionization and ion time-of-flight techniques.

Oral presentation

Stereodynamics of surface chemical reactions on silicon

Okada, Michio*; Hashinokuchi, Michihiro*; Fukuyama, Tetsuya*; Teraoka, Yuden; Kasai, Toshio*

no journal, , 

Oriented supersonic molecular beams of NO and CH$$_{3}$$Cl molecules, which have a parmanent dipole molent, are generated by non-uniform electric fields. The oriented NO and CH$$_{3}$$Cl beams dissociate and adsorbed at Si(111) and Si(001) surfaces, respectively. Molecular orientation effects for the surface reactions were studied. Sticking probabilities were evaluated in the reactions of oriented CH$$_{3}$$Cl molecules with the Si(001) surface by the King and Wells method. High reactivity was obtained in the Cl-end collisions. And, elements on the Si(111) surface were analysed by X-ray photoemission spectroscopy in the NO reactions at the Si(111) surface. High reactivity was clarified in the N-end collisions.

Oral presentation

Effects of vibrational and rotational excitations on the dissociative adsorption of O$$_{2}$$ on Cu surfaces

Moritani, Kosuke*; Tsuda, Muneyuki*; Teraoka, Yuden; Okada, Michio*; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Kasai, Toshio*; Kasai, Hideaki*

no journal, , 

Oxygen molecules adsorbe dissociatively at Cu(111), Cu(110), and Cu(001) surfaces. The oxygen uptake curves were investigated by using supersonic molecular beam techniques and photoemission spectroscopy with synchrotron radiation. Adsorption probability increased with increasing translational kinetic energy of oxygen molecules. Vibrational and rotational levels of oxygen molecules were excited by elevation of nozzle temperature up to 1400 K keeping the incident energy of 0.5 eV. Although the adsorption probability increased with increasing nozzle temperature by 1000 K, it decreased inversely around 1400 K. These phenomena were interpreted as adsorption probability increase by vibrational excitation and decrease by rotational excitation.

Oral presentation

Initial oxidation of Cu$$_{3}$$Pd(111) surface

Tsuda, Yasutaka*; Makino, Takamasa*; Tsukada, Chie; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Okada, Michio*

no journal, , 

It is well-known that oxidation is an important chemical reactions in corrosion processes. Cu$$_{3}$$Pd has an attracting material due to its catalytic property and its oxidation is the important subject. In this presentation, initial oxidation processes at the Cu$$_{3}$$Pd(111) surface was studied by using molecular beams. In situ photoemission measurements were conducted using surface chemistry apparatus at BL23SU at SPring-8. Single crystal Cu$$_{3}$$Pd was used after cleaning by means of Ar ion sputtering and annealing. It was found that molecular beams facilitate oxidation compared to that for backfilling condition. Furthermore, diffusion of surface atoms seems to be driven with increasing surface temperature.

Oral presentation

Oxidation of Cu$$_{3}$$Pt(111) surface with hyperthermal oxygen molecule

Tsuda, Yasutaka*; Makino, Takamasa*; Tsukada, Chie; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Okada, Michio*

no journal, , 

Oxidation is a main reaction in corrosion processes and its understabding is important to develop anticorrosion materials. In this study, initial oxidation at Cu$$_{3}$$Pt(111) surface was investigated by using surface analysis apparatus at BL23SU of SPring-8. The surface oxidized by 2.3 eV molecular beams was analzyed by synchrotron radiation photoelectron spectroscopy. We confirmed that Cu L$$_{3}$$M$$_{4.5}$$M$$_{4.5}$$ AES spectrum and Cu-2p XPS spectrum show the only growth of Cu oxide whereas Pt oxide was not formed from the results of Pt-4f XPS. It was also found that the reactivity of Cu$$_{3}$$Pd(111) surface is lower than that of Cu$$_{3}$$Au(111) surface.

Oral presentation

Initial oxidation of copper alloy surfaces with a hyperthermal oxygen molecular beam

Tsuda, Yasutaka*; Makino, Takamasa*; Yoshida, Hikaru; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Okada, Michio*

no journal, , 

Initial stage of corrosion is one of the central topics in material science. In the present study, we report the results of oxidation on Cu$$_{3}$$Pd(111) and Cu$$_{3}$$Pt(111) with a hyperthermal O$$_{2}$$ molecular beam (HOMB) with variable incident energies, using X-ray photoemission spectroscopy in conjunction with synchrotron radiation. All experiments were performed using the Surface Reaction Analysis Apparatus constructed in BL23SU at SPring-8. The Cu$$_{3}$$Pd(111) and Cu$$_{3}$$Pt(111) samples were cleaned by Ar+ sputtering and annealing. The kinetic energy of the HOMB was set to be 2.3 eV. From the uptake curves, it was found that the oxidation of Cu$$_{3}$$Pt is less effective than that on Cu$$_{3}$$Au and Cu$$_{3}$$Pd. This suppression of the surface reactivity may be caused by the Pt-rich subsurface layer.

Oral presentation

Surface temperature dependence of oxide formation on Cu$$_{3}$$Pt(111)

Tsuda, Yasutaka*; Makino, Takamasa*; Yoshida, Hikaru; Yoshigoe, Akitaka; Fukuyama, Tetsuya*; Okada, Michio*

no journal, , 

The oxidation with oxygen molecules is important in a metal corrosion process. In order to develop high noncorrosive materials, the understanding of oxidation processes is significant. In this study, the influence on oxidation reaction due to alloy ingredient difference was investigated by the comparison between Cu$$_{3}$$Au(111) and Cu$$_{3}$$Pt(111) surfaces. It was found that the Cu$$_{3}$$Pt(111) surface has lower reactivity than the Cu$$_{3}$$Au(111) surface.

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