著者

Shun Hasegawa Yuji Kunisada Norihito Sakaguchi

出版者

The Japan Society of Vacuum and Surface Science

雑誌

e-Journal of Surface Science and Nanotechnology (ISSN:13480391)

巻号頁・発行日

vol.16, pp.193-200, 2018-05-25 (Released:2018-05-25)

参考文献数

38

被引用文献数

4

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In this study, we calculated the diffusion of an Fe atom on graphene and various light-element (B, N, O, Si, P, and S)-doped graphene supports, using first-principles calculations based on density functional theory. We focused on dopants that could suppress the detachment and diffusion of an Fe atom. Such doped graphene supports would have strong potential in high-durability fuel cell catalysts and hydrogen storage materials. The Fe atom adsorbs on pristine graphene via ionic bonding. The bonding between the Fe atom and pristine graphene is very weak, and it has a low adsorption energy of −0.61 eV. Doped graphene contains unoccupied localized orbitals. B-, O-, Si-, and P-doped graphene show high adsorption energies of −1.70 eV, −2.70 eV, −1.46 eV, and −1.38 eV, respectively. Thus, these graphene supports could suppress the detachment of Fe nanoclusters and nanoparticles. We demonstrate that these doped graphene supports with high adsorption energies also have high diffusion barriers, which suppresses the agglomeration of Fe nanoclusters and nanoparticles. We conclude that B-, O-, Si-, and P-doped graphene are promising supports for enhancing the adsorption lifetime of Fe nanoclusters and nanoparticles. [DOI: 10.1380/ejssnt.2018.193]

著者

Keita Tanahashi Yusei Omura Hidekazu Naya Yuji Kunisada Norihito Sakaguchi Ade Kurniawan Takahiro Nomura

出版者

The Iron and Steel Institute of Japan

雑誌

ISIJ International (ISSN:09151559)

巻号頁・発行日

vol.62, no.12, pp.2578-2586, 2022-12-15 (Released:2022-12-15)

参考文献数

30

被引用文献数

1

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High-temperature pressure swing adsorption (HT-PSA) is a promising energy-saving approach for oxygen production from air. Ca2AlMnO5+δ, a Brownmillerite-type perovskite, is a promising sorbent for HT-PSA because of its remarkably high oxygen storage capacity (up to 3.3 wt%). In this study, we investigated the redox thermodynamics of Ca2AlMnO5+δ by pressure–composition–temperature (PCT) measurements and investigated the HT-PSA performance of Ca2AlMnO5+δ pellets in a 100 g-scale packed-bed-type reactor. PCT measurements revealed that Ca2AlMnO5+δ can reversibly separate 2.2 wt% of oxygen per cycle under equilibrium conditions between ambient oxygen partial pressure and 5×10−4 MPa at 525°C. However, in a 5 min switching HT-PSA test, Ca2AlMnO5+δ pellets were able to reversibly separate less than 1 wt% oxygen per cycle, which is significantly lower than that estimated from the thermodynamic properties of Ca2AlMnO5+δ. On the other hand, the exothermic oxygen storage and endothermic oxygen release reactions cause significant temperature variation of the packed bed. This study clarifies that, in order to increase the energy efficiency of oxygen separation by HT-PSA, there is a need to compensate for the heat of reaction, which changes the reactor temperature in a direction that interferes with the reaction.

著者

Norihito Sakaguchi Fuuta Yamaki Genki Saito Yuji Kunisada

出版者

The Japan Institute of Metals and Materials

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

vol.58, no.10, pp.1341-1345, 2017-10-01 (Released:2017-09-25)

参考文献数

21

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We analyzed the spatial distribution of Ca dopants in α-SiAlON by using a statistical approach that analyzed a high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) image. By evaluating the image intensity of each atomic column, we found that the intensity deviation of columns with Ca atoms was twice that of other atomic columns. The results of HAADF-STEM image simulation suggested that there was a long-range repulsive interaction along the [0001] direction between pairs of Ca atoms in the same Ca column. Moreover, correlation of image intensities in neighboring Ca columns suggested the existence of a short-range repulsive force between first-nearest-neighbor Ca atoms. The origin of such anisotropic interactions between pairs of Ca atoms will be discussed.

著者

Norihito Sakaguchi Fuuta Yamaki Genki Saito Yuji Kunisada

出版者

(公社)日本金属学会/(一社)軽金属学会,(一社)資源・素材学会,ナノ学会,(公社)日本金属学会,(一社)日本塑性加工学会,(公社)日本鋳造工学会,日本銅学会,(一社)日本熱処理技術協会,(一社)日本熱電学会,(一社)日本非破壊検査協会,(一社)日本溶射学会,(一社)粉体粉末冶金協会,(公社)腐食防食学会

雑誌

MATERIALS TRANSACTIONS (ISSN:13459678)

巻号頁・発行日

pp.MAW201705, (Released:2017-07-24)

参考文献数

21

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We analyzed the spatial distribution of Ca dopants in α-SiAlON by using a statistical approach that analyzed a high-angle annular dark-field (HAADF) scanning transmission electron microscopy (STEM) image. By evaluating the image intensity of each atomic column, we found that the intensity deviation of columns with Ca atoms was twice that of other atomic columns. The results of HAADF-STEM image simulation suggested that there was a long-range repulsive interaction along the [0001] direction between pairs of Ca atoms in the same Ca column. Moreover, correlation of image intensities in neighboring Ca columns suggested the existence of a short-range repulsive force between first-nearest-neighbor Ca atoms. The origin of such anisotropic interactions between pairs of Ca atoms will be discussed.