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Your search keyword '"Utsumi, Yuichi"' showing total 413 results
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413 results on '"Utsumi, Yuichi"'

2. Development of a microwave chemical cell coupled with post-wall waveguide for in situ/operando soft x-ray absorbance spectroscopy under microwave irradiation.

Author

Fujitani, Kaito, Suzuki, Satoru, Kishihara, Mitsuyoshi, and Utsumi, Yuichi

Subjects
MICROWAVE spectroscopy, X-ray spectroscopy, SOFT X rays, MICROWAVES, SYNCHROTRON radiation, MICROWAVE heating
Abstract

In this study, we developed a microwave chemical cell for total electron yield soft x-ray absorption spectroscopy (XAS) using synchrotron radiation under microwave irradiation. In addition, in situ XAS measurements of ammonia borane were performed using the device developed. The device comprises a post-wall waveguide housing a sample holder formed within it. Electrons emitted from the sample during soft x-ray irradiation pass through the metal plates of the waveguide and are measured using a picoammeter. Integration of the microwave irradiation structure into a synchrotron radiation beamline, which is a challenge in soft x-ray analysis requiring measurements in a high-vacuum atmosphere, was achieved by miniaturizing the device using 24.125 GHz ISM band microwaves, instead of the typical 2.45 GHz microwaves. Performance of the device was thoroughly assessed through temperature distribution simulation, temperature measurement of water, and evaluation of frequency characteristics. When the sample holder was filled with water and irradiated with 3 W microwaves, the temperature increased to 97 °C, which is close to the boiling point. The in situ XAS measurements performed using this device with ammonia borane/graphite (2:1) powder at the B-K edge during microwave irradiation showed that peaks associated with hydrogen desorption intensified with prolonged microwave exposure. This result indicates that microwave heating in a vacuum and soft x-ray analysis during microwave heating were achieved. The developed microwave chemical cell emerges as a powerful tool, facilitating advancements in our understanding of elementary chemical processes and elucidating microwave-specific effects such as local heating during microwave irradiation. [ABSTRACT FROM AUTHOR]

Published
2024
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5. Quasi-free-standing monolayer hexagonal boron nitride on Ni

Author

Suzuki, Satoru, Haruyama, Yuichi, Niibe, Masahito, Tokushima, Takashi, Yamaguchi, Akinobu, Utsumi, Yuichi, Ito, Atsushi, Kadowaki, Ryo, Maruta, Akane, and Abukawa, Tadashi

Subjects
Condensed Matter - Mesoscale and Nanoscale Physics
Abstract

The electronic structure of monolayer hexagonal boron nitride grown on Ni by the diffusion and precipitation method was studied by x-ray absorption spectroscopy, emission spectroscopy, x-ray photoelectron spectroscopy and micro-ultraviolet photoemission spectroscopy. No indication of hybridization between h-BN pi and Ni 3d orbitals was observed. That is, the monolayer h-BN was found to be in the quasi-free-standing state. These results are in striking contrast to those of previous studies in which h-BN was strongly bound to the Ni surface by the orbital hybridization. The absence of hybridization is attributed to absence of a Ni(111) surface in this study. The lattice-matched Ni(111) surface is considered to be essential to orbital hybridization between h-BN and Ni.

Published
2018
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6. Continuous On‐Chip Synthesis of Ag Nanoparticles Assisted by Resonant Microwave Heating Using a Post‐Wall Waveguide.

Author

Fujitani, Kaito, Kishihara, Mitsuyoshi, Sugiyama, Munehiro, and Utsumi, Yuichi

Subjects
NANOPARTICLE synthesis, SILVER nanoparticles, MICROWAVE heating, ELECTROMAGNETIC waves, RESONANCE effect
Abstract

Microfluidics made of dimethylpolysiloxane were developed for chemical synthesis using microwave heating at 24.125 GHz, and microwave efficiency was enhanced by the microwave resonance effect. In addition, the device was fabricated using a mold created using a 3D printer to reduce production costs. The microchip structure comprised a post‐wall waveguide and a microchannel that passed through the waveguide. This post‐wall waveguide also comprises metal columns (post‐wall) instead of a conductor side wall, and easily introduces microchannels through the gaps between the metal columns. The waveguide length was adjusted to achieve a resonance frequency of 24 GHz using an electromagnetic wave simulation, assuming that the microchannel was filled with pure water. Microwaves with an input power of 4 W caused a maximum temperature increase of 93 °C; this result is ~10 °C higher than that of a microchip with non‐resonant structure. In this study, Ag nanoparticles were synthesized using a chemical reaction induced by microwave irradiation of a chip flow system. Owing to irradiating the mixing reagent with microwaves of an input power of 4 W while controlling the flow rate at 0.7 μl/min, the formation of Ag nanoparticles with an average particle size of ~19.2 ± 2.4 nm was demonstrated by absorbance measurements and dynamic light scattering. It is expected that microwave microfluidics enhanced by the resonance effect will substantialize nanoparticle synthesis and high‐efficiency automated chemical synthesis combined with multichemical unit operations. © 2024 Institute of Electrical Engineers of Japan and Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

Published
2024
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25. In situ fluorescence yield soft X-ray absorption spectroscopy of electrochemical nickel deposition processes with and without ethylene glycol

Author

Yamaguchi, Akinobu, Akamatsu, Naoya, Saegusa, Shunya, Nakamura, Ryo, Utsumi, Yuichi, Kato, Masaru, Yagi, Ichizo, Ishihara, Tomoko, Oura, Masaki, Yamaguchi, Akinobu, Akamatsu, Naoya, Saegusa, Shunya, Nakamura, Ryo, Utsumi, Yuichi, Kato, Masaru, Yagi, Ichizo, Ishihara, Tomoko, and Oura, Masaki

Abstract

The electrochemical Ni deposition at a platinum electrode was investigated in a plating nickel bath in the presence and absence of ethylene glycol (EG) using fluorescence yield soft X-ray absorption spectroscopy (FY-XAS) in the Ni L2,3-edge and O K-edge regions under potential control. At ≤+0.35 V vs. the reversible hydrogen electrode (RHE), the electrochemical Ni deposition was detected by the Ni L2,3-edge FY-XAS in the presence of EG whereas almost no such event was observed in the absence of EG. A drastic decrease of FY-XAS intensities in the O K-edge region was also observed in the presence of EG at >+0.35 V vs. RHE, suggesting that the nano-/micro-structured Ni deposition initiated by the removal of water molecules occurs on the Pt electrode. The complex formation of Ni2+ with EG and the adsorption of EG on the Ni surface could play an important role in the Ni deposition. This study demonstrates that the in situ FY-XAS is a powerful and surface-sensitive technique to understand (electro)chemical reactions including polyol synthesis and electrocatalysis at solid–liquid interfaces.

Published
2022

26. In situ fluorescence yield soft X-ray absorption spectroscopy of electrochemical nickel deposition processes with and without ethylene glycol

Author

1000070423035, Yamaguchi, Akinobu, Akamatsu, Naoya, Saegusa, Shunya, Nakamura, Ryo, 1000080326298, Utsumi, Yuichi, 1000070709633, Kato, Masaru, 1000040292776, Yagi, Ichizo, Ishihara, Tomoko, 1000050250113, Oura, Masaki, 1000070423035, Yamaguchi, Akinobu, Akamatsu, Naoya, Saegusa, Shunya, Nakamura, Ryo, 1000080326298, Utsumi, Yuichi, 1000070709633, Kato, Masaru, 1000040292776, Yagi, Ichizo, Ishihara, Tomoko, 1000050250113, and Oura, Masaki

Abstract

The electrochemical Ni deposition at a platinum electrode was investigated in a plating nickel bath in the presence and absence of ethylene glycol (EG) using fluorescence yield soft X-ray absorption spectroscopy (FY-XAS) in the Ni L2,3-edge and O K-edge regions under potential control. At ≤+0.35 V vs. the reversible hydrogen electrode (RHE), the electrochemical Ni deposition was detected by the Ni L2,3-edge FY-XAS in the presence of EG whereas almost no such event was observed in the absence of EG. A drastic decrease of FY-XAS intensities in the O K-edge region was also observed in the presence of EG at >+0.35 V vs. RHE, suggesting that the nano-/micro-structured Ni deposition initiated by the removal of water molecules occurs on the Pt electrode. The complex formation of Ni2+ with EG and the adsorption of EG on the Ni surface could play an important role in the Ni deposition. This study demonstrates that the in situ FY-XAS is a powerful and surface-sensitive technique to understand (electro)chemical reactions including polyol synthesis and electrocatalysis at solid–liquid interfaces.

Published
2022

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